tor/ReleaseNotes

This document summarizes new features and bugfixes in each stable release
of Tor. If you want to see more detailed descriptions of the changes in
each development snapshot, see the ChangeLog file.

Changes in version 0.3.0.8 - 2017-06-08
  Tor 0.3.0.8 fixes a pair of bugs that would allow an attacker to
  remotely crash a hidden service with an assertion failure. Anyone
  running a hidden service should upgrade to this version, or to some
  other version with fixes for TROVE-2017-004 and TROVE-2017-005.

  Tor 0.3.0.8 also includes fixes for several key management bugs
  that sometimes made relays unreliable, as well as several other
  bugfixes described below.

  o Major bugfixes (hidden service, relay, security, backport
    from 0.3.1.3-alpha):
    - Fix a remotely triggerable assertion failure when a hidden service
      handles a malformed BEGIN cell. Fixes bug 22493, tracked as
      TROVE-2017-004 and as CVE-2017-0375; bugfix on 0.3.0.1-alpha.
    - Fix a remotely triggerable assertion failure caused by receiving a
      BEGIN_DIR cell on a hidden service rendezvous circuit. Fixes bug
      22494, tracked as TROVE-2017-005 and CVE-2017-0376; bugfix
      on 0.2.2.1-alpha.

  o Major bugfixes (relay, link handshake, backport from 0.3.1.3-alpha):
    - When performing the v3 link handshake on a TLS connection, report
      that we have the x509 certificate that we actually used on that
      connection, even if we have changed certificates since that
      connection was first opened. Previously, we would claim to have
      used our most recent x509 link certificate, which would sometimes
      make the link handshake fail. Fixes one case of bug 22460; bugfix
      on 0.2.3.6-alpha.

  o Major bugfixes (relays, key management, backport from 0.3.1.3-alpha):
    - Regenerate link and authentication certificates whenever the key
      that signs them changes; also, regenerate link certificates
      whenever the signed key changes. Previously, these processes were
      only weakly coupled, and we relays could (for minutes to hours)
      wind up with an inconsistent set of keys and certificates, which
      other relays would not accept. Fixes two cases of bug 22460;
      bugfix on 0.3.0.1-alpha.
    - When sending an Ed25519 signing->link certificate in a CERTS cell,
      send the certificate that matches the x509 certificate that we
      used on the TLS connection. Previously, there was a race condition
      if the TLS context rotated after we began the TLS handshake but
      before we sent the CERTS cell. Fixes a case of bug 22460; bugfix
      on 0.3.0.1-alpha.

  o Major bugfixes (hidden service v3, backport from 0.3.1.1-alpha):
    - Stop rejecting v3 hidden service descriptors because their size
      did not match an old padding rule. Fixes bug 22447; bugfix on
      tor-0.3.0.1-alpha.

  o Minor features (fallback directory list, backport from 0.3.1.3-alpha):
    - Replace the 177 fallbacks originally introduced in Tor 0.2.9.8 in
      December 2016 (of which ~126 were still functional) with a list of
      151 fallbacks (32 new, 119 unchanged, 58 removed) generated in May
      2017. Resolves ticket 21564.

  o Minor bugfixes (configuration, backport from 0.3.1.1-alpha):
    - Do not crash when starting with LearnCircuitBuildTimeout 0. Fixes
      bug 22252; bugfix on 0.2.9.3-alpha.

  o Minor bugfixes (correctness, backport from 0.3.1.3-alpha):
    - Avoid undefined behavior when parsing IPv6 entries from the geoip6
      file. Fixes bug 22490; bugfix on 0.2.4.6-alpha.

  o Minor bugfixes (link handshake, backport from 0.3.1.3-alpha):
    - Lower the lifetime of the RSA->Ed25519 cross-certificate to six
      months, and regenerate it when it is within one month of expiring.
      Previously, we had generated this certificate at startup with a
      ten-year lifetime, but that could lead to weird behavior when Tor
      was started with a grossly inaccurate clock. Mitigates bug 22466;
      mitigation on 0.3.0.1-alpha.

  o Minor bugfixes (memory leak, directory authority, backport from
    0.3.1.2-alpha):
    - When directory authorities reject a router descriptor due to
      keypinning, free the router descriptor rather than leaking the
      memory. Fixes bug 22370; bugfix on 0.2.7.2-alpha.


Changes in version 0.2.9.11 - 2017-06-08
  Tor 0.2.9.11 backports a fix for a bug that would allow an attacker to
  remotely crash a hidden service with an assertion failure. Anyone
  running a hidden service should upgrade to this version, or to some
  other version with fixes for TROVE-2017-005. (Versions before 0.3.0
  are not affected by TROVE-2017-004.)

  Tor 0.2.9.11 also backports fixes for several key management bugs
  that sometimes made relays unreliable, as well as several other
  bugfixes described below.

  o Major bugfixes (hidden service, relay, security, backport
    from 0.3.1.3-alpha):
    - Fix a remotely triggerable assertion failure caused by receiving a
      BEGIN_DIR cell on a hidden service rendezvous circuit. Fixes bug
      22494, tracked as TROVE-2017-005 and CVE-2017-0376; bugfix
      on 0.2.2.1-alpha.

  o Major bugfixes (relay, link handshake, backport from 0.3.1.3-alpha):
    - When performing the v3 link handshake on a TLS connection, report
      that we have the x509 certificate that we actually used on that
      connection, even if we have changed certificates since that
      connection was first opened. Previously, we would claim to have
      used our most recent x509 link certificate, which would sometimes
      make the link handshake fail. Fixes one case of bug 22460; bugfix
      on 0.2.3.6-alpha.

  o Minor features (fallback directory list, backport from 0.3.1.3-alpha):
    - Replace the 177 fallbacks originally introduced in Tor 0.2.9.8 in
      December 2016 (of which ~126 were still functional) with a list of
      151 fallbacks (32 new, 119 unchanged, 58 removed) generated in May
      2017. Resolves ticket 21564.

  o Minor features (future-proofing, backport from 0.3.0.7):
    - Tor no longer refuses to download microdescriptors or descriptors if
      they are listed as "published in the future".  This change will
      eventually allow us to stop listing meaningful "published" dates
      in microdescriptor consensuses, and thereby allow us to reduce the
      resources required to download consensus diffs by over 50%.
      Implements part of ticket 21642; implements part of proposal 275.

  o Minor features (directory authorities, backport from 0.3.0.4-rc)
    - Directory authorities now reject relays running versions
      0.2.9.1-alpha through 0.2.9.4-alpha, because those relays
      suffer from bug 20499 and don't keep their consensus cache
      up-to-date. Resolves ticket 20509.

  o Minor features (geoip):
    - Update geoip and geoip6 to the May 2 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (control port, backport from 0.3.0.6):
    - The GETINFO extra-info/digest/<digest> command was broken because
      of a wrong base16 decode return value check, introduced when
      refactoring that API. Fixes bug 22034; bugfix on 0.2.9.1-alpha.

  o Minor bugfixes (correctness, backport from 0.3.1.3-alpha):
    - Avoid undefined behavior when parsing IPv6 entries from the geoip6
      file. Fixes bug 22490; bugfix on 0.2.4.6-alpha.

  o Minor bugfixes (Linux seccomp2 sandbox, backport from 0.3.0.7):
    - The getpid() system call is now permitted under the Linux seccomp2
      sandbox, to avoid crashing with versions of OpenSSL (and other
      libraries) that attempt to learn the process's PID by using the
      syscall rather than the VDSO code. Fixes bug 21943; bugfix
      on 0.2.5.1-alpha.

  o Minor bugfixes (memory leak, directory authority, backport
    from 0.3.1.2-alpha):
    - When directory authorities reject a router descriptor due to
      keypinning, free the router descriptor rather than leaking the
      memory. Fixes bug 22370; bugfix on 0.2.7.2-alpha.

Changes in version 0.2.8.14 - 2017-06-08
  Tor 0.2.7.8 backports a fix for a bug that would allow an attacker to
  remotely crash a hidden service with an assertion failure. Anyone
  running a hidden service should upgrade to this version, or to some
  other version with fixes for TROVE-2017-005.  (Versions before 0.3.0
  are not affected by TROVE-2017-004.)

  o Major bugfixes (hidden service, relay, security):
    - Fix a remotely triggerable assertion failure caused by receiving a
      BEGIN_DIR cell on a hidden service rendezvous circuit. Fixes bug
      22494, tracked as TROVE-2017-005 and CVE-2017-0376; bugfix
      on 0.2.2.1-alpha.

  o Minor features (geoip):
    - Update geoip and geoip6 to the May 2 2017 Maxmind GeoLite2
      Country database.

  o Minor features (fallback directory list, backport from 0.3.1.3-alpha):
    - Replace the 177 fallbacks originally introduced in Tor 0.2.9.8 in
      December 2016 (of which ~126 were still functional) with a list of
      151 fallbacks (32 new, 119 unchanged, 58 removed) generated in May
      2017. Resolves ticket 21564.

  o Minor bugfixes (correctness):
    - Avoid undefined behavior when parsing IPv6 entries from the geoip6
      file. Fixes bug 22490; bugfix on 0.2.4.6-alpha.

Changes in version 0.2.7.8 - 2017-06-08
  Tor 0.2.7.8 backports a fix for a bug that would allow an attacker to
  remotely crash a hidden service with an assertion failure. Anyone
  running a hidden service should upgrade to this version, or to some
  other version with fixes for TROVE-2017-005.  (Versions before 0.3.0
  are not affected by TROVE-2017-004.)

  o Major bugfixes (hidden service, relay, security):
    - Fix a remotely triggerable assertion failure caused by receiving a
      BEGIN_DIR cell on a hidden service rendezvous circuit. Fixes bug
      22494, tracked as TROVE-2017-005 and CVE-2017-0376; bugfix
      on 0.2.2.1-alpha.

  o Minor features (geoip):
    - Update geoip and geoip6 to the May 2 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (correctness):
    - Avoid undefined behavior when parsing IPv6 entries from the geoip6
      file. Fixes bug 22490; bugfix on 0.2.4.6-alpha.


Changes in version 0.2.6.12 - 2017-06-08
  Tor 0.2.6.12 backports a fix for a bug that would allow an attacker to
  remotely crash a hidden service with an assertion failure. Anyone
  running a hidden service should upgrade to this version, or to some
  other version with fixes for TROVE-2017-005.  (Versions before 0.3.0
  are not affected by TROVE-2017-004.)

  o Major bugfixes (hidden service, relay, security):
    - Fix a remotely triggerable assertion failure caused by receiving a
      BEGIN_DIR cell on a hidden service rendezvous circuit. Fixes bug
      22494, tracked as TROVE-2017-005 and CVE-2017-0376; bugfix
      on 0.2.2.1-alpha.

  o Minor features (geoip):
    - Update geoip and geoip6 to the May 2 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (correctness):
    - Avoid undefined behavior when parsing IPv6 entries from the geoip6
      file. Fixes bug 22490; bugfix on 0.2.4.6-alpha.

Changes in version 0.2.5.14 - 2017-06-08
  Tor 0.2.5.14 backports a fix for a bug that would allow an attacker to
  remotely crash a hidden service with an assertion failure. Anyone
  running a hidden service should upgrade to this version, or to some
  other version with fixes for TROVE-2017-005.  (Versions before 0.3.0
  are not affected by TROVE-2017-004.)

  o Major bugfixes (hidden service, relay, security):
    - Fix a remotely triggerable assertion failure caused by receiving a
      BEGIN_DIR cell on a hidden service rendezvous circuit. Fixes bug
      22494, tracked as TROVE-2017-005 and CVE-2017-0376; bugfix
      on 0.2.2.1-alpha.

  o Minor features (geoip):
    - Update geoip and geoip6 to the May 2 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (correctness):
    - Avoid undefined behavior when parsing IPv6 entries from the geoip6
      file. Fixes bug 22490; bugfix on 0.2.4.6-alpha.

Changes in version 0.2.4.29 - 2017-06-08
  Tor 0.2.4.29 backports a fix for a bug that would allow an attacker to
  remotely crash a hidden service with an assertion failure. Anyone
  running a hidden service should upgrade to this version, or to some
  other version with fixes for TROVE-2017-005.  (Versions before 0.3.0
  are not affected by TROVE-2017-004.)

  o Major bugfixes (hidden service, relay, security):
    - Fix a remotely triggerable assertion failure caused by receiving a
      BEGIN_DIR cell on a hidden service rendezvous circuit. Fixes bug
      22494, tracked as TROVE-2017-005 and CVE-2017-0376; bugfix
      on 0.2.2.1-alpha.

  o Minor features (geoip):
    - Update geoip and geoip6 to the May 2 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (correctness):
    - Avoid undefined behavior when parsing IPv6 entries from the geoip6
      file. Fixes bug 22490; bugfix on 0.2.4.6-alpha.


Changes in version 0.3.0.7 - 2017-05-15
  Tor 0.3.0.7 fixes a medium-severity security bug in earlier versions
  of Tor 0.3.0.x, where an attacker could cause a Tor relay process
  to exit. Relays running earlier versions of Tor 0.3.0.x should upgrade;
  clients are not affected.

  o Major bugfixes (hidden service directory, security):
    - Fix an assertion failure in the hidden service directory code, which
      could be used by an attacker to remotely cause a Tor relay process to
      exit. Relays running earlier versions of Tor 0.3.0.x should upgrade.
      should upgrade. This security issue is tracked as TROVE-2017-002.
      Fixes bug 22246; bugfix on 0.3.0.1-alpha.

  o Minor features:
    - Update geoip and geoip6 to the May 2 2017 Maxmind GeoLite2
      Country database.

  o Minor features (future-proofing):
    - Tor no longer refuses to download microdescriptors or descriptors
      if they are listed as "published in the future". This change will
      eventually allow us to stop listing meaningful "published" dates
      in microdescriptor consensuses, and thereby allow us to reduce the
      resources required to download consensus diffs by over 50%.
      Implements part of ticket 21642; implements part of proposal 275.

  o Minor bugfixes (Linux seccomp2 sandbox):
    - The getpid() system call is now permitted under the Linux seccomp2
      sandbox, to avoid crashing with versions of OpenSSL (and other
      libraries) that attempt to learn the process's PID by using the
      syscall rather than the VDSO code. Fixes bug 21943; bugfix
      on 0.2.5.1-alpha.


Changes in version 0.3.0.6 - 2017-04-26
  Tor 0.3.0.6 is the first stable release of the Tor 0.3.0 series.

  With the 0.3.0 series, clients and relays now use Ed25519 keys to
  authenticate their link connections to relays, rather than the old
  RSA1024 keys that they used before. (Circuit crypto has been
  Curve25519-authenticated since 0.2.4.8-alpha.) We have also replaced
  the guard selection and replacement algorithm to behave more robustly
  in the presence of unreliable networks, and to resist guard-
  capture attacks.

  This series also includes numerous other small features and bugfixes,
  along with more groundwork for the upcoming hidden-services revamp.

  Per our stable release policy, we plan to support the Tor 0.3.0
  release series for at least the next nine months, or for three months
  after the first stable release of the 0.3.1 series: whichever is
  longer. If you need a release with long-term support, we recommend
  that you stay with the 0.2.9 series.

  Below are the changes since 0.2.9.10. For a list of only the changes
  since 0.3.0.5-rc, see the ChangeLog file.

  o Major features (directory authority, security):
    - The default for AuthDirPinKeys is now 1: directory authorities
      will reject relays where the RSA identity key matches a previously
      seen value, but the Ed25519 key has changed. Closes ticket 18319.

  o Major features (guard selection algorithm):
    - Tor's guard selection algorithm has been redesigned from the
      ground up, to better support unreliable networks and restrictive
      sets of entry nodes, and to better resist guard-capture attacks by
      hostile local networks. Implements proposal 271; closes
      ticket 19877.

  o Major features (next-generation hidden services):
    - Relays can now handle v3 ESTABLISH_INTRO cells as specified by
      prop224 aka "Next Generation Hidden Services". Service and clients
      don't use this functionality yet. Closes ticket 19043. Based on
      initial code by Alec Heifetz.
    - Relays now support the HSDir version 3 protocol, so that they can
      can store and serve v3 descriptors. This is part of the next-
      generation onion service work detailled in proposal 224. Closes
      ticket 17238.

  o Major features (protocol, ed25519 identity keys):
    - Clients now support including Ed25519 identity keys in the EXTEND2
      cells they generate. By default, this is controlled by a consensus
      parameter, currently disabled. You can turn this feature on for
      testing by setting ExtendByEd25519ID in your configuration. This
      might make your traffic appear different than the traffic
      generated by other users, however. Implements part of ticket
      15056; part of proposal 220.
    - Relays now understand requests to extend to other relays by their
      Ed25519 identity keys. When an Ed25519 identity key is included in
      an EXTEND2 cell, the relay will only extend the circuit if the
      other relay can prove ownership of that identity. Implements part
      of ticket 15056; part of proposal 220.
    - Relays now use Ed25519 to prove their Ed25519 identities and to
      one another, and to clients. This algorithm is faster and more
      secure than the RSA-based handshake we've been doing until now.
      Implements the second big part of proposal 220; Closes
      ticket 15055.

  o Major features (security):
    - Change the algorithm used to decide DNS TTLs on client and server
      side, to better resist DNS-based correlation attacks like the
      DefecTor attack of Greschbach, Pulls, Roberts, Winter, and
      Feamster. Now relays only return one of two possible DNS TTL
      values, and clients are willing to believe DNS TTL values up to 3
      hours long. Closes ticket 19769.

  o Major bugfixes (client, onion service, also in 0.2.9.9):
    - Fix a client-side onion service reachability bug, where multiple
      socks requests to an onion service (or a single slow request)
      could cause us to mistakenly mark some of the service's
      introduction points as failed, and we cache that failure so
      eventually we run out and can't reach the service. Also resolves a
      mysterious "Remote server sent bogus reason code 65021" log
      warning. The bug was introduced in ticket 17218, where we tried to
      remember the circuit end reason as a uint16_t, which mangled
      negative values. Partially fixes bug 21056 and fixes bug 20307;
      bugfix on 0.2.8.1-alpha.

  o Major bugfixes (crash, directory connections):
    - Fix a rare crash when sending a begin cell on a circuit whose
      linked directory connection had already been closed. Fixes bug
      21576; bugfix on 0.2.9.3-alpha. Reported by Alec Muffett.

  o Major bugfixes (directory authority):
    - During voting, when marking a relay as a probable sybil, do not
      clear its BadExit flag: sybils can still be bad in other ways
      too. (We still clear the other flags.) Fixes bug 21108; bugfix
      on 0.2.0.13-alpha.

  o Major bugfixes (DNS):
    - Fix a bug that prevented exit nodes from caching DNS records for
      more than 60 seconds. Fixes bug 19025; bugfix on 0.2.4.7-alpha.

  o Major bugfixes (IPv6 Exits):
    - Stop rejecting all IPv6 traffic on Exits whose exit policy rejects
      any IPv6 addresses. Instead, only reject a port over IPv6 if the
      exit policy rejects that port on more than an IPv6 /16 of
      addresses. This bug was made worse by 17027 in 0.2.8.1-alpha,
      which rejected a relay's own IPv6 address by default. Fixes bug
      21357; bugfix on commit 004f3f4e53 in 0.2.4.7-alpha.

  o Major bugfixes (parsing):
    - Fix an integer underflow bug when comparing malformed Tor
      versions. This bug could crash Tor when built with
      --enable-expensive-hardening, or on Tor 0.2.9.1-alpha through Tor
      0.2.9.8, which were built with -ftrapv by default. In other cases
      it was harmless. Part of TROVE-2017-001. Fixes bug 21278; bugfix
      on 0.0.8pre1. Found by OSS-Fuzz.
    - When parsing a malformed content-length field from an HTTP
      message, do not read off the end of the buffer. This bug was a
      potential remote denial-of-service attack against Tor clients and
      relays. A workaround was released in October 2016, to prevent this
      bug from crashing Tor. This is a fix for the underlying issue,
      which should no longer matter (if you applied the earlier patch).
      Fixes bug 20894; bugfix on 0.2.0.16-alpha. Bug found by fuzzing
      using AFL (http://lcamtuf.coredump.cx/afl/).

  o Major bugfixes (scheduler):
    - Actually compare circuit policies in ewma_cmp_cmux(). This bug
      caused the channel scheduler to behave more or less randomly,
      rather than preferring channels with higher-priority circuits.
      Fixes bug 20459; bugfix on 0.2.6.2-alpha.

  o Major bugfixes (security, also in 0.2.9.9):
    - Downgrade the "-ftrapv" option from "always on" to "only on when
      --enable-expensive-hardening is provided." This hardening option,
      like others, can turn survivable bugs into crashes--and having it
      on by default made a (relatively harmless) integer overflow bug
      into a denial-of-service bug. Fixes bug 21278 (TROVE-2017-001);
      bugfix on 0.2.9.1-alpha.

  o Minor feature (client):
    - Enable IPv6 traffic on the SocksPort by default. To disable this,
      a user will have to specify "NoIPv6Traffic". Closes ticket 21269.

  o Minor feature (fallback scripts):
    - Add a check_existing mode to updateFallbackDirs.py, which checks
      if fallbacks in the hard-coded list are working. Closes ticket
      20174. Patch by haxxpop.

  o Minor feature (protocol versioning):
    - Add new protocol version for proposal 224. HSIntro now advertises
      version "3-4" and HSDir version "1-2". Fixes ticket 20656.

  o Minor features (ciphersuite selection):
    - Allow relays to accept a wider range of ciphersuites, including
      chacha20-poly1305 and AES-CCM. Closes the other part of 15426.
    - Clients now advertise a list of ciphersuites closer to the ones
      preferred by Firefox. Closes part of ticket 15426.

  o Minor features (controller):
    - Add "GETINFO sr/current" and "GETINFO sr/previous" keys, to expose
      shared-random values to the controller. Closes ticket 19925.
    - When HSFETCH arguments cannot be parsed, say "Invalid argument"
      rather than "unrecognized." Closes ticket 20389; patch from
      Ivan Markin.

  o Minor features (controller, configuration):
    - Each of the *Port options, such as SocksPort, ORPort, ControlPort,
      and so on, now comes with a __*Port variant that will not be saved
      to the torrc file by the controller's SAVECONF command. This
      change allows TorBrowser to set up a single-use domain socket for
      each time it launches Tor. Closes ticket 20956.
    - The GETCONF command can now query options that may only be
      meaningful in context-sensitive lists. This allows the controller
      to query the mixed SocksPort/__SocksPort style options introduced
      in feature 20956. Implements ticket 21300.

  o Minor features (diagnostic, directory client):
    - Warn when we find an unexpected inconsistency in directory
      download status objects. Prevents some negative consequences of
      bug 20593.

  o Minor features (directory authorities):
    - Directory authorities now reject descriptors that claim to be
      malformed versions of Tor. Helps prevent exploitation of
      bug 21278.
    - Reject version numbers with components that exceed INT32_MAX.
      Otherwise 32-bit and 64-bit platforms would behave inconsistently.
      Fixes bug 21450; bugfix on 0.0.8pre1.

  o Minor features (directory authority):
    - Add a new authority-only AuthDirTestEd25519LinkKeys option (on by
      default) to control whether authorities should try to probe relays
      by their Ed25519 link keys. This option will go away in a few
      releases--unless we encounter major trouble in our ed25519 link
      protocol rollout, in which case it will serve as a safety option.

  o Minor features (directory cache):
    - Relays and bridges will now refuse to serve the consensus they
      have if they know it is too old for a client to use. Closes
      ticket 20511.

  o Minor features (ed25519 link handshake):
    - Advertise support for the ed25519 link handshake using the
      subprotocol-versions mechanism, so that clients can tell which
      relays can identity themselves by Ed25519 ID. Closes ticket 20552.

  o Minor features (entry guards):
    - Add UseEntryGuards to TEST_OPTIONS_DEFAULT_VALUES in order to not
      break regression tests.
    - Require UseEntryGuards when UseBridges is set, in order to make
      sure bridges aren't bypassed. Resolves ticket 20502.

  o Minor features (fallback directories):
    - Allow 3 fallback relays per operator, which is safe now that we
      are choosing 200 fallback relays. Closes ticket 20912.
    - Annotate updateFallbackDirs.py with the bandwidth and consensus
      weight for each candidate fallback. Closes ticket 20878.
    - Display the relay fingerprint when downloading consensuses from
      fallbacks. Closes ticket 20908.
    - Exclude relays affected by bug 20499 from the fallback list.
      Exclude relays from the fallback list if they are running versions
      known to be affected by bug 20499, or if in our tests they deliver
      a stale consensus (i.e. one that expired more than 24 hours ago).
      Closes ticket 20539.
    - Make it easier to change the output sort order of fallbacks.
      Closes ticket 20822.
    - Reduce the minimum fallback bandwidth to 1 MByte/s. Part of
      ticket 18828.
    - Require fallback directories to have the same address and port for
      7 days (now that we have enough relays with this stability).
      Relays whose OnionOO stability timer is reset on restart by bug
      18050 should upgrade to Tor 0.2.8.7 or later, which has a fix for
      this issue. Closes ticket 20880; maintains short-term fix
      in 0.2.8.2-alpha.
    - Require fallbacks to have flags for 90% of the time (weighted
      decaying average), rather than 95%. This allows at least 73% of
      clients to bootstrap in the first 5 seconds without contacting an
      authority. Part of ticket 18828.
    - Select 200 fallback directories for each release. Closes
      ticket 20881.

  o Minor features (fingerprinting resistence, authentication):
    - Extend the length of RSA keys used for TLS link authentication to
      2048 bits. (These weren't used for forward secrecy; for forward
      secrecy, we used P256.) Closes ticket 13752.

  o Minor features (geoip):
    - Update geoip and geoip6 to the April 4 2017 Maxmind GeoLite2
      Country database.

  o Minor features (geoip, also in 0.2.9.9):
    - Update geoip and geoip6 to the January 4 2017 Maxmind GeoLite2
      Country database.

  o Minor features (infrastructure):
    - Implement smartlist_add_strdup() function. Replaces the use of
      smartlist_add(sl, tor_strdup(str)). Closes ticket 20048.

  o Minor features (linting):
    - Enhance the changes file linter to warn on Tor versions that are
      prefixed with "tor-". Closes ticket 21096.

  o Minor features (logging):
    - In several places, describe unset ed25519 keys as "<unset>",
      rather than the scary "AAAAAAAA...AAA". Closes ticket 21037.

  o Minor features (portability, compilation):
    - Autoconf now checks to determine if OpenSSL structures are opaque,
      instead of explicitly checking for OpenSSL version numbers. Part
      of ticket 21359.
    - Support building with recent LibreSSL code that uses opaque
      structures. Closes ticket 21359.

  o Minor features (relay):
    - We now allow separation of exit and relay traffic to different
      source IP addresses, using the OutboundBindAddressExit and
      OutboundBindAddressOR options respectively. Closes ticket 17975.
      Written by Michael Sonntag.

  o Minor features (reliability, crash):
    - Try better to detect problems in buffers where they might grow (or
      think they have grown) over 2 GB in size. Diagnostic for
      bug 21369.

  o Minor features (testing):
    - During 'make test-network-all', if tor logs any warnings, ask
      chutney to output them. Requires a recent version of chutney with
      the 21572 patch. Implements 21570.

  o Minor bugfix (control protocol):
    - The reply to a "GETINFO config/names" request via the control
      protocol now spells the type "Dependent" correctly. This is a
      breaking change in the control protocol. (The field seems to be
      ignored by the most common known controllers.) Fixes bug 18146;
      bugfix on 0.1.1.4-alpha.
    - The GETINFO extra-info/digest/<digest> command was broken because
      of a wrong base16 decode return value check, introduced when
      refactoring that API. Fixes bug 22034; bugfix on 0.2.9.1-alpha.

  o Minor bugfix (logging):
    - Don't recommend the use of Tor2web in non-anonymous mode.
      Recommending Tor2web is a bad idea because the client loses all
      anonymity. Tor2web should only be used in specific cases by users
      who *know* and understand the issues. Fixes bug 21294; bugfix
      on 0.2.9.3-alpha.

  o Minor bugfixes (bug resilience):
    - Fix an unreachable size_t overflow in base64_decode(). Fixes bug
      19222; bugfix on 0.2.0.9-alpha. Found by Guido Vranken; fixed by
      Hans Jerry Illikainen.

  o Minor bugfixes (build):
    - Replace obsolete Autoconf macros with their modern equivalent and
      prevent similar issues in the future. Fixes bug 20990; bugfix
      on 0.1.0.1-rc.

  o Minor bugfixes (certificate expiration time):
    - Avoid using link certificates that don't become valid till some
      time in the future. Fixes bug 21420; bugfix on 0.2.4.11-alpha

  o Minor bugfixes (client):
    - Always recover from failures in extend_info_from_node(), in an
      attempt to prevent any recurrence of bug 21242. Fixes bug 21372;
      bugfix on 0.2.3.1-alpha.
    - When clients that use bridges start up with a cached consensus on
      disk, they were ignoring it and downloading a new one. Now they
      use the cached one. Fixes bug 20269; bugfix on 0.2.3.12-alpha.

  o Minor bugfixes (code correctness):
    - Repair a couple of (unreachable or harmless) cases of the risky
      comparison-by-subtraction pattern that caused bug 21278.

  o Minor bugfixes (config):
    - Don't assert on startup when trying to get the options list and
      LearnCircuitBuildTimeout is set to 0: we are currently parsing the
      options so of course they aren't ready yet. Fixes bug 21062;
      bugfix on 0.2.9.3-alpha.

  o Minor bugfixes (configuration):
    - Accept non-space whitespace characters after the severity level in
      the `Log` option. Fixes bug 19965; bugfix on 0.2.1.1-alpha.
    - Support "TByte" and "TBytes" units in options given in bytes.
      "TB", "terabyte(s)", "TBit(s)" and "terabit(s)" were already
      supported. Fixes bug 20622; bugfix on 0.2.0.14-alpha.

  o Minor bugfixes (configure, autoconf):
    - Rename the configure option --enable-expensive-hardening to
      --enable-fragile-hardening. Expensive hardening makes the tor
      daemon abort when some kinds of issues are detected. Thus, it
      makes tor more at risk of remote crashes but safer against RCE or
      heartbleed bug category. We now try to explain this issue in a
      message from the configure script. Fixes bug 21290; bugfix
      on 0.2.5.4-alpha.

  o Minor bugfixes (consensus weight):
    - Add new consensus method that initializes bw weights to 1 instead
      of 0. This prevents a zero weight from making it all the way to
      the end (happens in small testing networks) and causing an error.
      Fixes bug 14881; bugfix on 0.2.2.17-alpha.

  o Minor bugfixes (crash prevention):
    - Fix an (currently untriggerable, but potentially dangerous) crash
      bug when base32-encoding inputs whose sizes are not a multiple of
      5. Fixes bug 21894; bugfix on 0.2.9.1-alpha.

  o Minor bugfixes (dead code):
    - Remove a redundant check for PidFile changes at runtime in
      options_transition_allowed(): this check is already performed
      regardless of whether the sandbox is active. Fixes bug 21123;
      bugfix on 0.2.5.4-alpha.

  o Minor bugfixes (descriptors):
    - Correctly recognise downloaded full descriptors as valid, even
      when using microdescriptors as circuits. This affects clients with
      FetchUselessDescriptors set, and may affect directory authorities.
      Fixes bug 20839; bugfix on 0.2.3.2-alpha.

  o Minor bugfixes (directory mirrors):
    - Allow relays to use directory mirrors without a DirPort: these
      relays need to be contacted over their ORPorts using a begindir
      connection. Fixes one case of bug 20711; bugfix on 0.2.8.2-alpha.
    - Clarify the message logged when a remote relay is unexpectedly
      missing an ORPort or DirPort: users were confusing this with a
      local port. Fixes another case of bug 20711; bugfix
      on 0.2.8.2-alpha.

  o Minor bugfixes (directory system):
    - Bridges and relays now use microdescriptors (like clients do)
      rather than old-style router descriptors. Now bridges will blend
      in with clients in terms of the circuits they build. Fixes bug
      6769; bugfix on 0.2.3.2-alpha.
    - Download all consensus flavors, descriptors, and authority
      certificates when FetchUselessDescriptors is set, regardless of
      whether tor is a directory cache or not. Fixes bug 20667; bugfix
      on all recent tor versions.

  o Minor bugfixes (documentation):
    - Update the tor manual page to document every option that can not
      be changed while tor is running. Fixes bug 21122.

  o Minor bugfixes (ed25519 certificates):
    - Correctly interpret ed25519 certificates that would expire some
      time after 19 Jan 2038. Fixes bug 20027; bugfix on 0.2.7.2-alpha.

  o Minor bugfixes (fallback directories):
    - Avoid checking fallback candidates' DirPorts if they are down in
      OnionOO. When a relay operator has multiple relays, this
      prioritizes relays that are up over relays that are down. Fixes
      bug 20926; bugfix on 0.2.8.3-alpha.
    - Stop failing when OUTPUT_COMMENTS is True in updateFallbackDirs.py.
      Fixes bug 20877; bugfix on 0.2.8.3-alpha.
    - Stop failing when a relay has no uptime data in
      updateFallbackDirs.py. Fixes bug 20945; bugfix on 0.2.8.1-alpha.

  o Minor bugfixes (hidden service):
    - Clean up the code for expiring intro points with no associated
      circuits. It was causing, rarely, a service with some expiring
      introduction points to not open enough additional introduction
      points. Fixes part of bug 21302; bugfix on 0.2.7.2-alpha.
    - Resolve two possible underflows which could lead to creating and
      closing a lot of introduction point circuits in a non-stop loop.
      Fixes bug 21302; bugfix on 0.2.7.2-alpha.
    - Stop setting the torrc option HiddenServiceStatistics to "0" just
      because we're not a bridge or relay. Instead, we preserve whatever
      value the user set (or didn't set). Fixes bug 21150; bugfix
      on 0.2.6.2-alpha.

  o Minor bugfixes (hidden services):
    - Make hidden services check for failed intro point connections,
      even when they have exceeded their intro point creation limit.
      Fixes bug 21596; bugfix on 0.2.7.2-alpha. Reported by Alec Muffett.
    - Make hidden services with 8 to 10 introduction points check for
      failed circuits immediately after startup. Previously, they would
      wait for 5 minutes before performing their first checks. Fixes bug
      21594; bugfix on 0.2.3.9-alpha. Reported by Alec Muffett.
    - Stop ignoring misconfigured hidden services. Instead, refuse to
      start tor until the misconfigurations have been corrected. Fixes
      bug 20559; bugfix on multiple commits in 0.2.7.1-alpha
      and earlier.

  o Minor bugfixes (IPv6):
    - Make IPv6-using clients try harder to find an IPv6 directory
      server. Fixes bug 20999; bugfix on 0.2.8.2-alpha.
    - When IPv6 addresses have not been downloaded yet (microdesc
      consensus documents don't list relay IPv6 addresses), use hard-
      coded addresses for authorities, fallbacks, and configured
      bridges. Now IPv6-only clients can use microdescriptors. Fixes bug
      20996; bugfix on b167e82 from 19608 in 0.2.8.5-alpha.

  o Minor bugfixes (memory leak at exit):
    - Fix a small harmless memory leak at exit of the previously unused
      RSA->Ed identity cross-certificate. Fixes bug 17779; bugfix
      on 0.2.7.2-alpha.

  o Minor bugfixes (onion services):
    - Allow the number of introduction points to be as low as 0, rather
      than as low as 3. Fixes bug 21033; bugfix on 0.2.7.2-alpha.

  o Minor bugfixes (portability):
    - Use "OpenBSD" compiler macro instead of "OPENBSD" or "__OpenBSD__".
      It is supported by OpenBSD itself, and also by most OpenBSD
      variants (such as Bitrig). Fixes bug 20980; bugfix
      on 0.1.2.1-alpha.

  o Minor bugfixes (portability, also in 0.2.9.9):
    - Avoid crashing when Tor is built using headers that contain
      CLOCK_MONOTONIC_COARSE, but then tries to run on an older kernel
      without CLOCK_MONOTONIC_COARSE. Fixes bug 21035; bugfix
      on 0.2.9.1-alpha.
    - Fix Libevent detection on platforms without Libevent 1 headers
      installed. Fixes bug 21051; bugfix on 0.2.9.1-alpha.

  o Minor bugfixes (relay):
    - Avoid a double-marked-circuit warning that could happen when we
      receive DESTROY cells under heavy load. Fixes bug 20059; bugfix
      on 0.1.0.1-rc.
    - Honor DataDirectoryGroupReadable when tor is a relay. Previously,
      initializing the keys would reset the DataDirectory to 0700
      instead of 0750 even if DataDirectoryGroupReadable was set to 1.
      Fixes bug 19953; bugfix on 0.0.2pre16. Patch by "redfish".

  o Minor bugfixes (testing):
    - Fix Raspbian build issues related to missing socket errno in
      test_util.c. Fixes bug 21116; bugfix on 0.2.8.2. Patch by "hein".
    - Remove undefined behavior from the backtrace generator by removing
      its signal handler. Fixes bug 21026; bugfix on 0.2.5.2-alpha.
    - Use bash in src/test/test-network.sh. This ensures we reliably
      call chutney's newer tools/test-network.sh when available. Fixes
      bug 21562; bugfix on 0.2.9.1-alpha.

  o Minor bugfixes (tor-resolve):
    - The tor-resolve command line tool now rejects hostnames over 255
      characters in length. Previously, it would silently truncate them,
      which could lead to bugs. Fixes bug 21280; bugfix on 0.0.9pre5.
      Patch by "junglefowl".

  o Minor bugfixes (unit tests):
    - Allow the unit tests to pass even when DNS lookups of bogus
      addresses do not fail as expected. Fixes bug 20862 and 20863;
      bugfix on unit tests introduced in 0.2.8.1-alpha
      through 0.2.9.4-alpha.

  o Minor bugfixes (util):
    - When finishing writing a file to disk, if we were about to replace
      the file with the temporary file created before and we fail to
      replace it, remove the temporary file so it doesn't stay on disk.
      Fixes bug 20646; bugfix on 0.2.0.7-alpha. Patch by fk.

  o Minor bugfixes (Windows services):
    - Be sure to initialize the monotonic time subsystem before using
      it, even when running as an NT service. Fixes bug 21356; bugfix
      on 0.2.9.1-alpha.

  o Minor bugfixes (Windows):
    - Check for getpagesize before using it to mmap files. This fixes
      compilation in some MinGW environments. Fixes bug 20530; bugfix on
      0.1.2.1-alpha. Reported by "ice".

  o Code simplification and refactoring:
    - Abolish all global guard context in entrynodes.c; replace with new
      guard_selection_t structure as preparation for proposal 271.
      Closes ticket 19858.
    - Extract magic numbers in circuituse.c into defined variables.
    - Introduce rend_service_is_ephemeral() that tells if given onion
      service is ephemeral. Replace unclear NULL-checkings for service
      directory with this function. Closes ticket 20526.
    - Refactor circuit_is_available_for_use to remove unnecessary check.
    - Refactor circuit_predict_and_launch_new for readability and
      testability. Closes ticket 18873.
    - Refactor code to manipulate global_origin_circuit_list into
      separate functions. Closes ticket 20921.
    - Refactor large if statement in purpose_needs_anonymity to use
      switch statement instead. Closes part of ticket 20077.
    - Refactor the hashing API to return negative values for errors, as
      is done as throughout the codebase. Closes ticket 20717.
    - Remove data structures that were used to index or_connection
      objects by their RSA identity digests. These structures are fully
      redundant with the similar structures used in the
      channel abstraction.
    - Remove duplicate code in the channel_write_*cell() functions.
      Closes ticket 13827; patch from Pingl.
    - Remove redundant behavior of is_sensitive_dir_purpose, refactor to
      use only purpose_needs_anonymity. Closes part of ticket 20077.
    - The code to generate and parse EXTEND and EXTEND2 cells has been
      replaced with code automatically generated by the
      "trunnel" utility.

  o Documentation (formatting):
    - Clean up formatting of tor.1 man page and HTML doc, where <pre>
      blocks were incorrectly appearing. Closes ticket 20885.

  o Documentation (man page):
    - Clarify many options in tor.1 and add some min/max values for
      HiddenService options. Closes ticket 21058.

  o Documentation:
    - Change '1' to 'weight_scale' in consensus bw weights calculation
      comments, as that is reality. Closes ticket 20273. Patch
      from pastly.
    - Clarify that when ClientRejectInternalAddresses is enabled (which
      is the default), multicast DNS hostnames for machines on the local
      network (of the form *.local) are also rejected. Closes
      ticket 17070.
    - Correct the value for AuthDirGuardBWGuarantee in the manpage, from
      250 KBytes to 2 MBytes. Fixes bug 20435; bugfix on 0.2.5.6-alpha.
    - Include the "TBits" unit in Tor's man page. Fixes part of bug
      20622; bugfix on 0.2.5.1-alpha.
    - Small fixes to the fuzzing documentation. Closes ticket 21472.
    - Stop the man page from incorrectly stating that HiddenServiceDir
      must already exist. Fixes 20486.
    - Update the description of the directory server options in the
      manual page, to clarify that a relay no longer needs to set
      DirPort in order to be a directory cache. Closes ticket 21720.

  o Removed features:
    - The AuthDirMaxServersPerAuthAddr option no longer exists: The same
      limit for relays running on a single IP applies to authority IP
      addresses as well as to non-authority IP addresses. Closes
      ticket 20960.
    - The UseDirectoryGuards torrc option no longer exists: all users
      that use entry guards will also use directory guards. Related to
      proposal 271; implements part of ticket 20831.

  o Testing:
    - Add tests for networkstatus_compute_bw_weights_v10.
    - Add unit tests circuit_predict_and_launch_new.
    - Extract dummy_origin_circuit_new so it can be used by other
      test functions.
    - New unit tests for tor_htonll(). Closes ticket 19563. Patch
      from "overcaffeinated".
    - Perform the coding style checks when running the tests and fail
      when coding style violations are found. Closes ticket 5500.


Changes in version 0.2.8.13 - 2017-03-03
  Tor 0.2.8.13 backports a security fix from later Tor
  releases.  Anybody running Tor 0.2.8.12 or earlier should upgrade to this
  this release, if for some reason they cannot upgrade to a later
  release series, and if they build Tor with the --enable-expensive-hardening
  option.

  Note that support for Tor 0.2.8.x is ending next year: we will not issue
  any fixes for the Tor 0.2.8.x series after 1 Jan 2018.  If you need
  a Tor release series with longer-term support, we recommend Tor 0.2.9.x.

  o Major bugfixes (parsing, backported from 0.3.0.4-rc):
    - Fix an integer underflow bug when comparing malformed Tor
      versions. This bug could crash Tor when built with
      --enable-expensive-hardening, or on Tor 0.2.9.1-alpha through Tor
      0.2.9.8, which were built with -ftrapv by default. In other cases
      it was harmless. Part of TROVE-2017-001. Fixes bug 21278; bugfix
      on 0.0.8pre1. Found by OSS-Fuzz.

  o Minor features (geoip):
    - Update geoip and geoip6 to the February 8 2017 Maxmind GeoLite2
      Country database.


Changes in version 0.2.7.7 - 2017-03-03
  Tor 0.2.7.7 backports a number of security fixes from later Tor
  releases.  Anybody running Tor 0.2.7.6 or earlier should upgrade to
  this release, if for some reason they cannot upgrade to a later
  release series.

  Note that support for Tor 0.2.7.x is ending this year: we will not issue
  any fixes for the Tor 0.2.7.x series after 1 August 2017.  If you need
  a Tor release series with longer-term support, we recommend Tor 0.2.9.x.

  o Directory authority changes (backport from 0.2.8.5-rc):
    - Urras is no longer a directory authority. Closes ticket 19271.

  o Directory authority changes (backport from 0.2.9.2-alpha):
    - The "Tonga" bridge authority has been retired; the new bridge
      authority is "Bifroest". Closes tickets 19728 and 19690.

  o Directory authority key updates (backport from 0.2.8.1-alpha):
    - Update the V3 identity key for the dannenberg directory authority:
      it was changed on 18 November 2015. Closes task 17906. Patch
      by "teor".

  o Major bugfixes (parsing, security, backport from 0.2.9.8):
    - Fix a bug in parsing that could cause clients to read a single
      byte past the end of an allocated region. This bug could be used
      to cause hardened clients (built with --enable-expensive-hardening)
      to crash if they tried to visit a hostile hidden service. Non-
      hardened clients are only affected depending on the details of
      their platform's memory allocator. Fixes bug 21018; bugfix on
      0.2.0.8-alpha. Found by using libFuzzer. Also tracked as TROVE-
      2016-12-002 and as CVE-2016-1254.

  o Major bugfixes (security, client, DNS proxy, backport from 0.2.8.3-alpha):
    - Stop a crash that could occur when a client running with DNSPort
      received a query with multiple address types, and the first
      address type was not supported. Found and fixed by Scott Dial.
      Fixes bug 18710; bugfix on 0.2.5.4-alpha.
    - Prevent a class of security bugs caused by treating the contents
      of a buffer chunk as if they were a NUL-terminated string. At
      least one such bug seems to be present in all currently used
      versions of Tor, and would allow an attacker to remotely crash
      most Tor instances, especially those compiled with extra compiler
      hardening. With this defense in place, such bugs can't crash Tor,
      though we should still fix them as they occur. Closes ticket
      20384 (TROVE-2016-10-001).

  o Major bugfixes (security, pointers, backport from 0.2.8.2-alpha):
    - Avoid a difficult-to-trigger heap corruption attack when extending
      a smartlist to contain over 16GB of pointers. Fixes bug 18162;
      bugfix on 0.1.1.11-alpha, which fixed a related bug incompletely.
      Reported by Guido Vranken.

  o Major bugfixes (dns proxy mode, crash, backport from 0.2.8.2-alpha):
    - Avoid crashing when running as a DNS proxy. Fixes bug 16248;
      bugfix on 0.2.0.1-alpha. Patch from "cypherpunks".

  o Major bugfixes (key management, backport from 0.2.8.3-alpha):
    - If OpenSSL fails to generate an RSA key, do not retain a dangling
      pointer to the previous (uninitialized) key value. The impact here
      should be limited to a difficult-to-trigger crash, if OpenSSL is
      running an engine that makes key generation failures possible, or
      if OpenSSL runs out of memory. Fixes bug 19152; bugfix on
      0.2.1.10-alpha. Found by Yuan Jochen Kang, Suman Jana, and
      Baishakhi Ray.

  o Major bugfixes (parsing, backported from 0.3.0.4-rc):
    - Fix an integer underflow bug when comparing malformed Tor
      versions. This bug could crash Tor when built with
      --enable-expensive-hardening, or on Tor 0.2.9.1-alpha through Tor
      0.2.9.8, which were built with -ftrapv by default. In other cases
      it was harmless. Part of TROVE-2017-001. Fixes bug 21278; bugfix
      on 0.0.8pre1. Found by OSS-Fuzz.

  o Minor features (security, memory erasure, backport from 0.2.8.1-alpha):
    - Make memwipe() do nothing when passed a NULL pointer or buffer of
      zero size. Check size argument to memwipe() for underflow. Fixes
      bug 18089; bugfix on 0.2.3.25 and 0.2.4.6-alpha. Reported by "gk",
      patch by "teor".

  o Minor features (bug-resistance, backport from 0.2.8.2-alpha):
    - Make Tor survive errors involving connections without a
      corresponding event object. Previously we'd fail with an
      assertion; now we produce a log message. Related to bug 16248.

  o Minor features (geoip):
    - Update geoip and geoip6 to the February 8 2017 Maxmind GeoLite2
      Country database.


Changes in version 0.2.6.11 - 2017-03-03
  Tor 0.2.6.11 backports a number of security fixes from later Tor
  releases.  Anybody running Tor 0.2.6.10 or earlier should upgrade to
  this release, if for some reason they cannot upgrade to a later
  release series.

  Note that support for Tor 0.2.6.x is ending this year: we will not issue
  any fixes for the Tor 0.2.6.x series after 1 August 2017.  If you need
  a Tor release series with longer-term support, we recommend Tor 0.2.9.x.

  o Directory authority changes (backport from 0.2.8.5-rc):
    - Urras is no longer a directory authority. Closes ticket 19271.

  o Directory authority changes (backport from 0.2.9.2-alpha):
    - The "Tonga" bridge authority has been retired; the new bridge
      authority is "Bifroest". Closes tickets 19728 and 19690.

  o Directory authority key updates (backport from 0.2.8.1-alpha):
    - Update the V3 identity key for the dannenberg directory authority:
      it was changed on 18 November 2015. Closes task 17906. Patch
      by "teor".

  o Major features (security fixes, backport from 0.2.9.4-alpha):
    - Prevent a class of security bugs caused by treating the contents
      of a buffer chunk as if they were a NUL-terminated string. At
      least one such bug seems to be present in all currently used
      versions of Tor, and would allow an attacker to remotely crash
      most Tor instances, especially those compiled with extra compiler
      hardening. With this defense in place, such bugs can't crash Tor,
      though we should still fix them as they occur. Closes ticket
      20384 (TROVE-2016-10-001).

  o Major bugfixes (parsing, security, backport from 0.2.9.8):
    - Fix a bug in parsing that could cause clients to read a single
      byte past the end of an allocated region. This bug could be used
      to cause hardened clients (built with --enable-expensive-hardening)
      to crash if they tried to visit a hostile hidden service. Non-
      hardened clients are only affected depending on the details of
      their platform's memory allocator. Fixes bug 21018; bugfix on
      0.2.0.8-alpha. Found by using libFuzzer. Also tracked as TROVE-
      2016-12-002 and as CVE-2016-1254.

  o Major bugfixes (security, client, DNS proxy, backport from 0.2.8.3-alpha):
    - Stop a crash that could occur when a client running with DNSPort
      received a query with multiple address types, and the first
      address type was not supported. Found and fixed by Scott Dial.
      Fixes bug 18710; bugfix on 0.2.5.4-alpha.

  o Major bugfixes (security, correctness, backport from 0.2.7.4-rc):
    - Fix an error that could cause us to read 4 bytes before the
      beginning of an openssl string. This bug could be used to cause
      Tor to crash on systems with unusual malloc implementations, or
      systems with unusual hardening installed. Fixes bug 17404; bugfix
      on 0.2.3.6-alpha.

  o Major bugfixes (security, pointers, backport from 0.2.8.2-alpha):
    - Avoid a difficult-to-trigger heap corruption attack when extending
      a smartlist to contain over 16GB of pointers. Fixes bug 18162;
      bugfix on 0.1.1.11-alpha, which fixed a related bug incompletely.
      Reported by Guido Vranken.

  o Major bugfixes (dns proxy mode, crash, backport from 0.2.8.2-alpha):
    - Avoid crashing when running as a DNS proxy. Fixes bug 16248;
      bugfix on 0.2.0.1-alpha. Patch from "cypherpunks".

  o Major bugfixes (guard selection, backport from 0.2.7.6):
    - Actually look at the Guard flag when selecting a new directory
      guard. When we implemented the directory guard design, we
      accidentally started treating all relays as if they have the Guard
      flag during guard selection, leading to weaker anonymity and worse
      performance. Fixes bug 17772; bugfix on 0.2.4.8-alpha. Discovered
      by Mohsen Imani.

  o Major bugfixes (key management, backport from 0.2.8.3-alpha):
    - If OpenSSL fails to generate an RSA key, do not retain a dangling
      pointer to the previous (uninitialized) key value. The impact here
      should be limited to a difficult-to-trigger crash, if OpenSSL is
      running an engine that makes key generation failures possible, or
      if OpenSSL runs out of memory. Fixes bug 19152; bugfix on
      0.2.1.10-alpha. Found by Yuan Jochen Kang, Suman Jana, and
      Baishakhi Ray.

  o Major bugfixes (parsing, backported from 0.3.0.4-rc):
    - Fix an integer underflow bug when comparing malformed Tor
      versions. This bug could crash Tor when built with
      --enable-expensive-hardening, or on Tor 0.2.9.1-alpha through Tor
      0.2.9.8, which were built with -ftrapv by default. In other cases
      it was harmless. Part of TROVE-2017-001. Fixes bug 21278; bugfix
      on 0.0.8pre1. Found by OSS-Fuzz.

  o Minor features (security, memory erasure, backport from 0.2.8.1-alpha):
    - Make memwipe() do nothing when passed a NULL pointer or buffer of
      zero size. Check size argument to memwipe() for underflow. Fixes
      bug 18089; bugfix on 0.2.3.25 and 0.2.4.6-alpha. Reported by "gk",
      patch by "teor".

  o Minor features (bug-resistance, backport from 0.2.8.2-alpha):
    - Make Tor survive errors involving connections without a
      corresponding event object. Previously we'd fail with an
      assertion; now we produce a log message. Related to bug 16248.

  o Minor features (geoip):
    - Update geoip and geoip6 to the February 8 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (compilation, backport from 0.2.7.6):
    - Fix a compilation warning with Clang 3.6: Do not check the
      presence of an address which can never be NULL. Fixes bug 17781.


Changes in version 0.2.5.13 - 2017-03-03
  Tor 0.2.5.13 backports a number of security fixes from later Tor
  releases.  Anybody running Tor 0.2.5.13 or earlier should upgrade to
  this release, if for some reason they cannot upgrade to a later
  release series.

  Note that support for Tor 0.2.5.x is ending next year: we will not issue
  any fixes for the Tor 0.2.5.x series after 1 May 2018.  If you need
  a Tor release series with longer-term support, we recommend Tor 0.2.9.x.

  o Directory authority changes (backport from 0.2.8.5-rc):
    - Urras is no longer a directory authority. Closes ticket 19271.

  o Directory authority changes (backport from 0.2.9.2-alpha):
    - The "Tonga" bridge authority has been retired; the new bridge
      authority is "Bifroest". Closes tickets 19728 and 19690.

  o Directory authority key updates (backport from 0.2.8.1-alpha):
    - Update the V3 identity key for the dannenberg directory authority:
      it was changed on 18 November 2015. Closes task 17906. Patch
      by "teor".

  o Major features (security fixes, backport from 0.2.9.4-alpha):
    - Prevent a class of security bugs caused by treating the contents
      of a buffer chunk as if they were a NUL-terminated string. At
      least one such bug seems to be present in all currently used
      versions of Tor, and would allow an attacker to remotely crash
      most Tor instances, especially those compiled with extra compiler
      hardening. With this defense in place, such bugs can't crash Tor,
      though we should still fix them as they occur. Closes ticket
      20384 (TROVE-2016-10-001).

  o Major bugfixes (parsing, security, backport from 0.2.9.8):
    - Fix a bug in parsing that could cause clients to read a single
      byte past the end of an allocated region. This bug could be used
      to cause hardened clients (built with --enable-expensive-hardening)
      to crash if they tried to visit a hostile hidden service. Non-
      hardened clients are only affected depending on the details of
      their platform's memory allocator. Fixes bug 21018; bugfix on
      0.2.0.8-alpha. Found by using libFuzzer. Also tracked as TROVE-
      2016-12-002 and as CVE-2016-1254.

  o Major bugfixes (security, client, DNS proxy, backport from 0.2.8.3-alpha):
    - Stop a crash that could occur when a client running with DNSPort
      received a query with multiple address types, and the first
      address type was not supported. Found and fixed by Scott Dial.
      Fixes bug 18710; bugfix on 0.2.5.4-alpha.

  o Major bugfixes (security, correctness, backport from 0.2.7.4-rc):
    - Fix an error that could cause us to read 4 bytes before the
      beginning of an openssl string. This bug could be used to cause
      Tor to crash on systems with unusual malloc implementations, or
      systems with unusual hardening installed. Fixes bug 17404; bugfix
      on 0.2.3.6-alpha.

  o Major bugfixes (security, pointers, backport from 0.2.8.2-alpha):
    - Avoid a difficult-to-trigger heap corruption attack when extending
      a smartlist to contain over 16GB of pointers. Fixes bug 18162;
      bugfix on 0.1.1.11-alpha, which fixed a related bug incompletely.
      Reported by Guido Vranken.

  o Major bugfixes (dns proxy mode, crash, backport from 0.2.8.2-alpha):
    - Avoid crashing when running as a DNS proxy. Fixes bug 16248;
      bugfix on 0.2.0.1-alpha. Patch from "cypherpunks".

  o Major bugfixes (guard selection, backport from 0.2.7.6):
    - Actually look at the Guard flag when selecting a new directory
      guard. When we implemented the directory guard design, we
      accidentally started treating all relays as if they have the Guard
      flag during guard selection, leading to weaker anonymity and worse
      performance. Fixes bug 17772; bugfix on 0.2.4.8-alpha. Discovered
      by Mohsen Imani.

  o Major bugfixes (key management, backport from 0.2.8.3-alpha):
    - If OpenSSL fails to generate an RSA key, do not retain a dangling
      pointer to the previous (uninitialized) key value. The impact here
      should be limited to a difficult-to-trigger crash, if OpenSSL is
      running an engine that makes key generation failures possible, or
      if OpenSSL runs out of memory. Fixes bug 19152; bugfix on
      0.2.1.10-alpha. Found by Yuan Jochen Kang, Suman Jana, and
      Baishakhi Ray.

  o Major bugfixes (parsing, backported from 0.3.0.4-rc):
    - Fix an integer underflow bug when comparing malformed Tor
      versions. This bug could crash Tor when built with
      --enable-expensive-hardening, or on Tor 0.2.9.1-alpha through Tor
      0.2.9.8, which were built with -ftrapv by default. In other cases
      it was harmless. Part of TROVE-2017-001. Fixes bug 21278; bugfix
      on 0.0.8pre1. Found by OSS-Fuzz.

  o Minor features (security, memory erasure, backport from 0.2.8.1-alpha):
    - Make memwipe() do nothing when passed a NULL pointer or buffer of
      zero size. Check size argument to memwipe() for underflow. Fixes
      bug 18089; bugfix on 0.2.3.25 and 0.2.4.6-alpha. Reported by "gk",
      patch by "teor".

  o Minor features (bug-resistance, backport from 0.2.8.2-alpha):
    - Make Tor survive errors involving connections without a
      corresponding event object. Previously we'd fail with an
      assertion; now we produce a log message. Related to bug 16248.

  o Minor features (geoip):
    - Update geoip and geoip6 to the February 8 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (compilation, backport from 0.2.7.6):
    - Fix a compilation warning with Clang 3.6: Do not check the
      presence of an address which can never be NULL. Fixes bug 17781.

  o Minor bugfixes (crypto error-handling, backport from 0.2.7.2-alpha):
    - Check for failures from crypto_early_init, and refuse to continue.
      A previous typo meant that we could keep going with an
      uninitialized crypto library, and would have OpenSSL initialize
      its own PRNG. Fixes bug 16360; bugfix on 0.2.5.2-alpha, introduced
      when implementing ticket 4900. Patch by "teor".

  o Minor bugfixes (hidden service, backport from 0.2.7.1-alpha):
    - Fix an out-of-bounds read when parsing invalid INTRODUCE2 cells on
      a client authorized hidden service. Fixes bug 15823; bugfix
      on 0.2.1.6-alpha.


Changes in version 0.2.4.28 - 2017-03-03
  Tor 0.2.4.28 backports a number of security fixes from later Tor
  releases.  Anybody running Tor 0.2.4.27 or earlier should upgrade to
  this release, if for some reason they cannot upgrade to a later
  release series.

  Note that support for Tor 0.2.4.x is ending soon: we will not issue
  any fixes for the Tor 0.2.4.x series after 1 August 2017.  If you need
  a Tor release series with long-term support, we recommend Tor 0.2.9.x.

  o Directory authority changes (backport from 0.2.8.5-rc):
    - Urras is no longer a directory authority. Closes ticket 19271.

  o Directory authority changes (backport from 0.2.9.2-alpha):
    - The "Tonga" bridge authority has been retired; the new bridge
      authority is "Bifroest". Closes tickets 19728 and 19690.

  o Directory authority key updates (backport from 0.2.8.1-alpha):
    - Update the V3 identity key for the dannenberg directory authority:
      it was changed on 18 November 2015. Closes task 17906. Patch
      by "teor".

  o Major features (security fixes, backport from 0.2.9.4-alpha):
    - Prevent a class of security bugs caused by treating the contents
      of a buffer chunk as if they were a NUL-terminated string. At
      least one such bug seems to be present in all currently used
      versions of Tor, and would allow an attacker to remotely crash
      most Tor instances, especially those compiled with extra compiler
      hardening. With this defense in place, such bugs can't crash Tor,
      though we should still fix them as they occur. Closes ticket
      20384 (TROVE-2016-10-001).

  o Major bugfixes (parsing, security, backport from 0.2.9.8):
    - Fix a bug in parsing that could cause clients to read a single
      byte past the end of an allocated region. This bug could be used
      to cause hardened clients (built with --enable-expensive-hardening)
      to crash if they tried to visit a hostile hidden service. Non-
      hardened clients are only affected depending on the details of
      their platform's memory allocator. Fixes bug 21018; bugfix on
      0.2.0.8-alpha. Found by using libFuzzer. Also tracked as TROVE-
      2016-12-002 and as CVE-2016-1254.

  o Major bugfixes (security, correctness, backport from 0.2.7.4-rc):
    - Fix an error that could cause us to read 4 bytes before the
      beginning of an openssl string. This bug could be used to cause
      Tor to crash on systems with unusual malloc implementations, or
      systems with unusual hardening installed. Fixes bug 17404; bugfix
      on 0.2.3.6-alpha.

  o Major bugfixes (security, pointers, backport from 0.2.8.2-alpha):
    - Avoid a difficult-to-trigger heap corruption attack when extending
      a smartlist to contain over 16GB of pointers. Fixes bug 18162;
      bugfix on 0.1.1.11-alpha, which fixed a related bug incompletely.
      Reported by Guido Vranken.

  o Major bugfixes (dns proxy mode, crash, backport from 0.2.8.2-alpha):
    - Avoid crashing when running as a DNS proxy. Fixes bug 16248;
      bugfix on 0.2.0.1-alpha. Patch from "cypherpunks".

  o Major bugfixes (guard selection, backport from 0.2.7.6):
    - Actually look at the Guard flag when selecting a new directory
      guard. When we implemented the directory guard design, we
      accidentally started treating all relays as if they have the Guard
      flag during guard selection, leading to weaker anonymity and worse
      performance. Fixes bug 17772; bugfix on 0.2.4.8-alpha. Discovered
      by Mohsen Imani.

  o Major bugfixes (key management, backport from 0.2.8.3-alpha):
    - If OpenSSL fails to generate an RSA key, do not retain a dangling
      pointer to the previous (uninitialized) key value. The impact here
      should be limited to a difficult-to-trigger crash, if OpenSSL is
      running an engine that makes key generation failures possible, or
      if OpenSSL runs out of memory. Fixes bug 19152; bugfix on
      0.2.1.10-alpha. Found by Yuan Jochen Kang, Suman Jana, and
      Baishakhi Ray.

  o Major bugfixes (parsing, backported from 0.3.0.4-rc):
    - Fix an integer underflow bug when comparing malformed Tor
      versions. This bug could crash Tor when built with
      --enable-expensive-hardening, or on Tor 0.2.9.1-alpha through Tor
      0.2.9.8, which were built with -ftrapv by default. In other cases
      it was harmless. Part of TROVE-2017-001. Fixes bug 21278; bugfix
      on 0.0.8pre1. Found by OSS-Fuzz.

  o Minor features (security, memory erasure, backport from 0.2.8.1-alpha):
    - Make memwipe() do nothing when passed a NULL pointer or buffer of
      zero size. Check size argument to memwipe() for underflow. Fixes
      bug 18089; bugfix on 0.2.3.25 and 0.2.4.6-alpha. Reported by "gk",
      patch by "teor".

  o Minor features (bug-resistance, backport from 0.2.8.2-alpha):
    - Make Tor survive errors involving connections without a
      corresponding event object. Previously we'd fail with an
      assertion; now we produce a log message. Related to bug 16248.

  o Minor features (DoS-resistance, backport from 0.2.7.1-alpha):
    - Make it harder for attackers to overload hidden services with
      introductions, by blocking multiple introduction requests on the
      same circuit. Resolves ticket 15515.

  o Minor features (geoip):
    - Update geoip and geoip6 to the February 8 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (compilation, backport from 0.2.7.6):
    - Fix a compilation warning with Clang 3.6: Do not check the
      presence of an address which can never be NULL. Fixes bug 17781.

  o Minor bugfixes (hidden service, backport from 0.2.7.1-alpha):
    - Fix an out-of-bounds read when parsing invalid INTRODUCE2 cells on
      a client authorized hidden service. Fixes bug 15823; bugfix
      on 0.2.1.6-alpha.


Changes in version 0.2.9.10 - 2017-03-01
  Tor 0.2.9.10 backports a security fix from later Tor release.  It also
  includes fixes for some major issues affecting directory authorities,
  LibreSSL compatibility, and IPv6 correctness.

  The Tor 0.2.9.x release series is now marked as a long-term-support
  series.  We intend to backport security fixes to 0.2.9.x until at
  least January of 2020.

  o Major bugfixes (directory authority, 0.3.0.3-alpha):
    - During voting, when marking a relay as a probable sybil, do not
      clear its BadExit flag: sybils can still be bad in other ways
      too. (We still clear the other flags.) Fixes bug 21108; bugfix
      on 0.2.0.13-alpha.

  o Major bugfixes (IPv6 Exits, backport from 0.3.0.3-alpha):
    - Stop rejecting all IPv6 traffic on Exits whose exit policy rejects
      any IPv6 addresses. Instead, only reject a port over IPv6 if the
      exit policy rejects that port on more than an IPv6 /16 of
      addresses. This bug was made worse by 17027 in 0.2.8.1-alpha,
      which rejected a relay's own IPv6 address by default. Fixes bug
      21357; bugfix on commit 004f3f4e53 in 0.2.4.7-alpha.

  o Major bugfixes (parsing, also in 0.3.0.4-rc):
    - Fix an integer underflow bug when comparing malformed Tor
      versions. This bug could crash Tor when built with
      --enable-expensive-hardening, or on Tor 0.2.9.1-alpha through Tor
      0.2.9.8, which were built with -ftrapv by default. In other cases
      it was harmless. Part of TROVE-2017-001. Fixes bug 21278; bugfix
      on 0.0.8pre1. Found by OSS-Fuzz.

  o Minor features (directory authorities, also in 0.3.0.4-rc):
    - Directory authorities now reject descriptors that claim to be
      malformed versions of Tor. Helps prevent exploitation of
      bug 21278.
    - Reject version numbers with components that exceed INT32_MAX.
      Otherwise 32-bit and 64-bit platforms would behave inconsistently.
      Fixes bug 21450; bugfix on 0.0.8pre1.

  o Minor features (geoip):
    - Update geoip and geoip6 to the February 8 2017 Maxmind GeoLite2
      Country database.

  o Minor features (portability, compilation, backport from 0.3.0.3-alpha):
    - Autoconf now checks to determine if OpenSSL structures are opaque,
      instead of explicitly checking for OpenSSL version numbers. Part
      of ticket 21359.
    - Support building with recent LibreSSL code that uses opaque
      structures. Closes ticket 21359.

  o Minor bugfixes (code correctness, also in 0.3.0.4-rc):
    - Repair a couple of (unreachable or harmless) cases of the risky
      comparison-by-subtraction pattern that caused bug 21278.

  o Minor bugfixes (tor-resolve, backport from 0.3.0.3-alpha):
    - The tor-resolve command line tool now rejects hostnames over 255
      characters in length. Previously, it would silently truncate them,
      which could lead to bugs. Fixes bug 21280; bugfix on 0.0.9pre5.
      Patch by "junglefowl".


Changes in version 0.2.9.9 - 2017-01-23
  Tor 0.2.9.9 fixes a denial-of-service bug where an attacker could
  cause relays and clients to crash, even if they were not built with
  the --enable-expensive-hardening option. This bug affects all 0.2.9.x
  versions, and also affects 0.3.0.1-alpha: all relays running an affected
  version should upgrade.

  This release also resolves a client-side onion service reachability
  bug, and resolves a pair of small portability issues.

  o Major bugfixes (security):
    - Downgrade the "-ftrapv" option from "always on" to "only on when
      --enable-expensive-hardening is provided." This hardening option,
      like others, can turn survivable bugs into crashes -- and having
      it on by default made a (relatively harmless) integer overflow bug
      into a denial-of-service bug. Fixes bug 21278 (TROVE-2017-001);
      bugfix on 0.2.9.1-alpha.

  o Major bugfixes (client, onion service):
    - Fix a client-side onion service reachability bug, where multiple
      socks requests to an onion service (or a single slow request)
      could cause us to mistakenly mark some of the service's
      introduction points as failed, and we cache that failure so
      eventually we run out and can't reach the service. Also resolves a
      mysterious "Remote server sent bogus reason code 65021" log
      warning. The bug was introduced in ticket 17218, where we tried to
      remember the circuit end reason as a uint16_t, which mangled
      negative values. Partially fixes bug 21056 and fixes bug 20307;
      bugfix on 0.2.8.1-alpha.

  o Minor features (geoip):
    - Update geoip and geoip6 to the January 4 2017 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (portability):
    - Avoid crashing when Tor is built using headers that contain
      CLOCK_MONOTONIC_COARSE, but then tries to run on an older kernel
      without CLOCK_MONOTONIC_COARSE. Fixes bug 21035; bugfix
      on 0.2.9.1-alpha.
    - Fix Libevent detection on platforms without Libevent 1 headers
      installed. Fixes bug 21051; bugfix on 0.2.9.1-alpha.


Changes in version 0.2.8.12 - 2016-12-19
  Tor 0.2.8.12 backports a fix for a medium-severity issue (bug 21018
  below) where Tor clients could crash when attempting to visit a
  hostile hidden service. Clients are recommended to upgrade as packages
  become available for their systems.

  It also includes an updated list of fallback directories, backported
  from 0.2.9.

  Now that the Tor 0.2.9 series is stable, only major bugfixes will be
  backported to 0.2.8 in the future.

  o Major bugfixes (parsing, security, backported from 0.2.9.8):
    - Fix a bug in parsing that could cause clients to read a single
      byte past the end of an allocated region. This bug could be used
      to cause hardened clients (built with --enable-expensive-hardening)
      to crash if they tried to visit a hostile hidden service. Non-
      hardened clients are only affected depending on the details of
      their platform's memory allocator. Fixes bug 21018; bugfix on
      0.2.0.8-alpha. Found by using libFuzzer. Also tracked as TROVE-
      2016-12-002 and as CVE-2016-1254.

  o Minor features (fallback directory list, backported from 0.2.9.8):
    - Replace the 81 remaining fallbacks of the 100 originally
      introduced in Tor 0.2.8.3-alpha in March 2016, with a list of 177
      fallbacks (123 new, 54 existing, 27 removed) generated in December
      2016. Resolves ticket 20170.

  o Minor features (geoip, backported from 0.2.9.7-rc):
    - Update geoip and geoip6 to the December 7 2016 Maxmind GeoLite2
      Country database.


Changes in version 0.2.9.8 - 2016-12-19
  Tor 0.2.9.8 is the first stable release of the Tor 0.2.9 series.

  The Tor 0.2.9 series makes mandatory a number of security features
  that were formerly optional. It includes support for a new shared-
  randomness protocol that will form the basis for next generation
  hidden services, includes a single-hop hidden service mode for
  optimizing .onion services that don't actually want to be hidden,
  tries harder not to overload the directory authorities with excessive
  downloads, and supports a better protocol versioning scheme for
  improved compatibility with other implementations of the Tor protocol.

  And of course, there are numerous other bugfixes and improvements.

  This release also includes a fix for a medium-severity issue (bug
  21018 below) where Tor clients could crash when attempting to visit a
  hostile hidden service. Clients are recommended to upgrade as packages
  become available for their systems.

  Below are listed the changes since Tor 0.2.8.11.  For a list of
  changes since 0.2.9.7-rc, see the ChangeLog file.

  o New system requirements:
    - When building with OpenSSL, Tor now requires version 1.0.1 or
      later. OpenSSL 1.0.0 and earlier are no longer supported by the
      OpenSSL team, and should not be used. Closes ticket 20303.
    - Tor now requires Libevent version 2.0.10-stable or later. Older
      versions of Libevent have less efficient backends for several
      platforms, and lack the DNS code that we use for our server-side
      DNS support. This implements ticket 19554.
    - Tor now requires zlib version 1.2 or later, for security,
      efficiency, and (eventually) gzip support. (Back when we started,
      zlib 1.1 and zlib 1.0 were still found in the wild. 1.2 was
      released in 2003. We recommend the latest version.)

  o Deprecated features:
    - A number of DNS-cache-related sub-options for client ports are now
      deprecated for security reasons, and may be removed in a future
      version of Tor. (We believe that client-side DNS caching is a bad
      idea for anonymity, and you should not turn it on.) The options
      are: CacheDNS, CacheIPv4DNS, CacheIPv6DNS, UseDNSCache,
      UseIPv4Cache, and UseIPv6Cache.
    - A number of options are deprecated for security reasons, and may
      be removed in a future version of Tor. The options are:
      AllowDotExit, AllowInvalidNodes, AllowSingleHopCircuits,
      AllowSingleHopExits, ClientDNSRejectInternalAddresses,
      CloseHSClientCircuitsImmediatelyOnTimeout,
      CloseHSServiceRendCircuitsImmediatelyOnTimeout,
      ExcludeSingleHopRelays, FastFirstHopPK, TLSECGroup,
      UseNTorHandshake, and WarnUnsafeSocks.
    - The *ListenAddress options are now deprecated as unnecessary: the
      corresponding *Port options should be used instead. These options
      may someday be removed. The affected options are:
      ControlListenAddress, DNSListenAddress, DirListenAddress,
      NATDListenAddress, ORListenAddress, SocksListenAddress,
      and TransListenAddress.

  o Major bugfixes (parsing, security, new since 0.2.9.7-rc):
    - Fix a bug in parsing that could cause clients to read a single
      byte past the end of an allocated region. This bug could be used
      to cause hardened clients (built with --enable-expensive-hardening)
      to crash if they tried to visit a hostile hidden service. Non-
      hardened clients are only affected depending on the details of
      their platform's memory allocator. Fixes bug 21018; bugfix on
      0.2.0.8-alpha. Found by using libFuzzer. Also tracked as TROVE-
      2016-12-002 and as CVE-2016-1254.

  o Major features (build, hardening):
    - Tor now builds with -ftrapv by default on compilers that support
      it. This option detects signed integer overflow (which C forbids),
      and turns it into a hard-failure. We do not apply this option to
      code that needs to run in constant time to avoid side-channels;
      instead, we use -fwrapv in that code. Closes ticket 17983.
    - When --enable-expensive-hardening is selected, stop applying the
      clang/gcc sanitizers to code that needs to run in constant time.
      Although we are aware of no introduced side-channels, we are not
      able to prove that there are none. Related to ticket 17983.

  o Major features (circuit building, security):
    - Authorities, relays, and clients now require ntor keys in all
      descriptors, for all hops (except for rare hidden service protocol
      cases), for all circuits, and for all other roles. Part of
      ticket 19163.
    - Authorities, relays, and clients only use ntor, except for
      rare cases in the hidden service protocol. Part of ticket 19163.

  o Major features (compilation):
    - Our big list of extra GCC warnings is now enabled by default when
      building with GCC (or with anything like Clang that claims to be
      GCC-compatible). To make all warnings into fatal compilation
      errors, pass --enable-fatal-warnings to configure. Closes
      ticket 19044.
    - Use the Autoconf macro AC_USE_SYSTEM_EXTENSIONS to automatically
      turn on C and POSIX extensions. (Previously, we attempted to do
      this on an ad hoc basis.) Closes ticket 19139.

  o Major features (directory authorities, hidden services):
    - Directory authorities can now perform the shared randomness
      protocol specified by proposal 250. Using this protocol, directory
      authorities generate a global fresh random value every day. In the
      future, this value will be used by hidden services to select
      HSDirs. This release implements the directory authority feature;
      the hidden service side will be implemented in the future as part
      of proposal 224. Resolves ticket 16943; implements proposal 250.

  o Major features (downloading, random exponential backoff):
    - When we fail to download an object from a directory service, wait
      for an (exponentially increasing) randomized amount of time before
      retrying, rather than a fixed interval as we did before. This
      prevents a group of Tor instances from becoming too synchronized,
      or a single Tor instance from becoming too predictable, in its
      download schedule. Closes ticket 15942.

  o Major features (resource management):
    - Tor can now notice it is about to run out of sockets, and
      preemptively close connections of lower priority. (This feature is
      off by default for now, since the current prioritizing method is
      yet not mature enough. You can enable it by setting
      "DisableOOSCheck 0", but watch out: it might close some sockets
      you would rather have it keep.) Closes ticket 18640.

  o Major features (single-hop "hidden" services):
    - Add experimental HiddenServiceSingleHopMode and
      HiddenServiceNonAnonymousMode options. When both are set to 1,
      every hidden service on that Tor instance becomes a non-anonymous
      Single Onion Service. Single Onions make one-hop (direct)
      connections to their introduction and rendezvous points. One-hop
      circuits make Single Onion servers easily locatable, but clients
      remain location-anonymous. This is compatible with the existing
      hidden service implementation, and works on the current Tor
      network without any changes to older relays or clients. Implements
      proposal 260, completes ticket 17178. Patch by teor and asn.

  o Major features (subprotocol versions):
    - Tor directory authorities now vote on a set of recommended
      "subprotocol versions", and on a set of required subprotocol
      versions. Clients and relays that lack support for a _required_
      subprotocol version will not start; those that lack support for a
      _recommended_ subprotocol version will warn the user to upgrade.
      This change allows compatible implementations of the Tor protocol(s)
      to exist without pretending to be 100% bug-compatible with
      particular releases of Tor itself. Closes ticket 19958; implements
      part of proposal 264.

  o Major bugfixes (circuit building):
    - Hidden service client-to-intro-point and service-to-rendezvous-
      point circuits use the TAP key supplied by the protocol, to avoid
      epistemic attacks. Fixes bug 19163; bugfix on 0.2.4.18-rc.

  o Major bugfixes (download scheduling):
    - Avoid resetting download status for consensuses hourly, since we
      already have another, smarter retry mechanism. Fixes bug 8625;
      bugfix on 0.2.0.9-alpha.
    - If a consensus expires while we are waiting for certificates to
      download, stop waiting for certificates.
    - If we stop waiting for certificates less than a minute after we
      started downloading them, do not consider the certificate download
      failure a separate failure. Fixes bug 20533; bugfix
      on 0.2.0.9-alpha.
    - When using exponential backoff in test networks, use a lower
      exponent, so the delays do not vary as much. This helps test
      networks bootstrap consistently. Fixes bug 20597; bugfix on 20499.

  o Major bugfixes (exit policies):
    - Avoid disclosing exit outbound bind addresses, configured port
      bind addresses, and local interface addresses in relay descriptors
      by default under ExitPolicyRejectPrivate. Instead, only reject
      these (otherwise unlisted) addresses if
      ExitPolicyRejectLocalInterfaces is set. Fixes bug 18456; bugfix on
      0.2.7.2-alpha. Patch by teor.

  o Major bugfixes (hidden services):
    - Allow Tor clients with appropriate controllers to work with
      FetchHidServDescriptors set to 0. Previously, this option also
      disabled descriptor cache lookup, thus breaking hidden services
      entirely. Fixes bug 18704; bugfix on 0.2.0.20-rc. Patch by "twim".
    - Clients now require hidden services to include the TAP keys for
      their intro points in the hidden service descriptor. This prevents
      an inadvertent upgrade to ntor, which a malicious hidden service
      could use to distinguish clients by consensus version. Fixes bug
      20012; bugfix on 0.2.4.8-alpha. Patch by teor.

  o Major bugfixes (relay, resolver, logging):
    - For relays that don't know their own address, avoid attempting a
      local hostname resolve for each descriptor we download. This
      will cut down on the number of "Success: chose address 'x.x.x.x'"
      log lines, and also avoid confusing clock jumps if the resolver
      is slow. Fixes bugs 20423 and 20610; bugfix on 0.2.8.1-alpha.

  o Minor features (port flags):
    - Add new flags to the *Port options to give finer control over which
      requests are allowed. The flags are NoDNSRequest, NoOnionTraffic,
      and the synthetic flag OnionTrafficOnly, which is equivalent to
      NoDNSRequest, NoIPv4Traffic, and NoIPv6Traffic. Closes enhancement
      18693; patch by "teor".

  o Minor features (build, hardening):
    - Detect and work around a libclang_rt problem that would prevent
      clang from finding __mulodi4() on some 32-bit platforms, and thus
      keep -ftrapv from linking on those systems. Closes ticket 19079.
    - When building on a system without runtime support for the runtime
      hardening options, try to log a useful warning at configuration
      time, rather than an incomprehensible warning at link time. If
      expensive hardening was requested, this warning becomes an error.
      Closes ticket 18895.

  o Minor features (client, directory):
    - Since authorities now omit all routers that lack the Running and
      Valid flags, we assume that any relay listed in the consensus must
      have those flags. Closes ticket 20001; implements part of
      proposal 272.

  o Minor features (code safety):
    - In our integer-parsing functions, ensure that the maximum value we
      allow is no smaller than the minimum value. Closes ticket 19063;
      patch from "U+039b".

  o Minor features (compilation, portability):
    - Compile correctly on MacOS 10.12 (aka "Sierra"). Closes
      ticket 20241.

  o Minor features (config):
    - Warn users when descriptor and port addresses are inconsistent.
      Mitigates bug 13953; patch by teor.

  o Minor features (controller):
    - Allow controllers to configure basic client authorization on
      hidden services when they create them with the ADD_ONION controller
      command. Implements ticket 15588. Patch by "special".
    - Fire a STATUS_SERVER controller event whenever the hibernation
      status changes between "awake"/"soft"/"hard". Closes ticket 18685.
    - Implement new GETINFO queries for all downloads that use
      download_status_t to schedule retries. This allows controllers to
      examine the schedule for pending downloads. Closes ticket 19323.

  o Minor features (development tools, etags):
    - Teach the "make tags" Makefile target how to correctly find
      "MOCK_IMPL" function definitions. Patch from nherring; closes
      ticket 16869.

  o Minor features (directory authority):
    - After voting, if the authorities decide that a relay is not
      "Valid", they no longer include it in the consensus at all. Closes
      ticket 20002; implements part of proposal 272.
    - Directory authorities now only give the Guard flag to a relay if
      they are also giving it the Stable flag. This change allows us to
      simplify path selection for clients. It should have minimal effect
      in practice, since >99% of Guards already have the Stable flag.
      Implements ticket 18624.
    - Directory authorities now write their v3-status-votes file out to
      disk earlier in the consensus process, so we have a record of the
      votes even if we abort the consensus process. Resolves
      ticket 19036.

  o Minor features (fallback directory list, new since 0.2.9.7-rc):
    - Replace the 81 remaining fallbacks of the 100 originally
      introduced in Tor 0.2.8.3-alpha in March 2016, with a list of 177
      fallbacks (123 new, 54 existing, 27 removed) generated in December
      2016. Resolves ticket 20170.

  o Minor features (hidden service):
    - Stop being so strict about the payload length of "rendezvous1"
      cells. We used to be locked in to the "TAP" handshake length, and
      now we can handle better handshakes like "ntor". Resolves
      ticket 18998.

  o Minor features (infrastructure, time):
    - Tor now includes an improved timer backend, so that we can
      efficiently support tens or hundreds of thousands of concurrent
      timers, as will be needed for some of our planned anti-traffic-
      analysis work. This code is based on William Ahern's "timeout.c"
      project, which implements a "tickless hierarchical timing wheel".
      Closes ticket 18365.
    - Tor now uses the operating system's monotonic timers (where
      available) for internal fine-grained timing. Previously we would
      look at the system clock, and then attempt to compensate for the
      clock running backwards. Closes ticket 18908.

  o Minor features (logging):
    - Add a set of macros to check nonfatal assertions, for internal
      use. Migrating more of our checks to these should help us avoid
      needless crash bugs. Closes ticket 18613.
    - Provide a more useful warning message when configured with an
      invalid Nickname. Closes ticket 18300; patch from "icanhasaccount".
    - When dumping unparseable router descriptors, optionally store them
      in separate files, named by digest, up to a configurable size
      limit. You can change the size limit by setting the
      MaxUnparseableDescSizeToLog option, and disable this feature by
      setting that option to 0. Closes ticket 18322.

  o Minor features (performance):
    - Change the "optimistic data" extension from "off by default" to
      "on by default". The default was ordinarily overridden by a
      consensus option, but when clients were bootstrapping for the
      first time, they would not have a consensus to get the option
      from. Changing this default saves a round-trip during startup.
      Closes ticket 18815.

  o Minor features (relay, usability):
    - When the directory authorities refuse a bad relay's descriptor,
      encourage the relay operator to contact us. Many relay operators
      won't notice this line in their logs, but it's a win if even a few
      learn why we don't like what their relay was doing. Resolves
      ticket 18760.

  o Minor features (security, TLS):
    - Servers no longer support clients that lack AES ciphersuites.
      (3DES is no longer considered an acceptable cipher.) We believe
      that no such Tor clients currently exist, since Tor has required
      OpenSSL 0.9.7 or later since 2009. Closes ticket 19998.

  o Minor features (testing):
    - Disable memory protections on OpenBSD when performing our unit
      tests for memwipe(). The test deliberately invokes undefined
      behavior, and the OpenBSD protections interfere with this. Patch
      from "rubiate". Closes ticket 20066.
    - Move the test-network.sh script to chutney, and modify tor's test-
      network.sh to call the (newer) chutney version when available.
      Resolves ticket 19116. Patch by teor.
    - Use the lcov convention for marking lines as unreachable, so that
      we don't count them when we're generating test coverage data.
      Update our coverage tools to understand this convention. Closes
      ticket 16792.
    - Our link-handshake unit tests now check that when invalid
      handshakes fail, they fail with the error messages we expected.
    - Our unit testing code that captures log messages no longer
      prevents them from being written out if the user asked for them
      (by passing --debug or --info or --notice or --warn to the "test"
      binary). This change prevents us from missing unexpected log
      messages simply because we were looking for others. Related to
      ticket 19999.
    - The unit tests now log all warning messages with the "BUG" flag.
      Previously, they only logged errors by default. This change will
      help us make our testing code more correct, and make sure that we
      only hit this code when we mean to. In the meantime, however,
      there will be more warnings in the unit test logs than before.
      This is preparatory work for ticket 19999.
    - The unit tests now treat any failure of a "tor_assert_nonfatal()"
      assertion as a test failure.
    - We've done significant work to make the unit tests run faster.

  o Minor features (testing, ipv6):
    - Add the hs-ipv6 chutney target to make test-network-all's IPv6
      tests. Remove bridges+hs, as it's somewhat redundant. This
      requires a recent chutney version that supports IPv6 clients,
      relays, and authorities. Closes ticket 20069; patch by teor.
    - Add the single-onion and single-onion-ipv6 chutney targets to
      "make test-network-all". This requires a recent chutney version
      with the single onion network flavors (git c72a652 or later).
      Closes ticket 20072; patch by teor.

  o Minor features (Tor2web):
    - Make Tor2web clients respect ReachableAddresses. This feature was
      inadvertently enabled in 0.2.8.6, then removed by bugfix 19973 on
      0.2.8.7. Implements feature 20034. Patch by teor.

  o Minor features (unix domain sockets):
    - When configuring a unix domain socket for a SocksPort,
      ControlPort, or Hidden service, you can now wrap the address in
      quotes, using C-style escapes inside the quotes. This allows unix
      domain socket paths to contain spaces. Resolves ticket 18753.

  o Minor features (user interface):
    - Tor now supports the ability to declare options deprecated, so
      that we can recommend that people stop using them. Previously, this
      was done in an ad-hoc way. There is a new --list-deprecated-options
      command-line option to list all of the deprecated options. Closes
      ticket 19820.

  o Minor features (virtual addresses):
    - Increase the maximum number of bits for the IPv6 virtual network
      prefix from 16 to 104. In this way, the condition for address
      allocation is less restrictive. Closes ticket 20151; feature
      on 0.2.4.7-alpha.

  o Minor bug fixes (circuits):
    - Use the CircuitBuildTimeout option whenever
      LearnCircuitBuildTimeout is disabled. Previously, we would respect
      the option when a user disabled it, but not when it was disabled
      because some other option was set. Fixes bug 20073; bugfix on
      0.2.4.12-alpha. Patch by teor.

  o Minor bugfixes (build):
    - The current Git revision when building from a local repository is
      now detected correctly when using git worktrees. Fixes bug 20492;
      bugfix on 0.2.3.9-alpha.

  o Minor bugfixes (relay address discovery):
    - Stop reordering IP addresses returned by the OS. This makes it
      more likely that Tor will guess the same relay IP address every
      time. Fixes issue 20163; bugfix on 0.2.7.1-alpha, ticket 17027.
      Reported by René Mayrhofer, patch by "cypherpunks".

  o Minor bugfixes (memory allocation):
    - Change how we allocate memory for large chunks on buffers, to
      avoid a (currently impossible) integer overflow, and to waste less
      space when allocating unusually large chunks. Fixes bug 20081;
      bugfix on 0.2.0.16-alpha. Issue identified by Guido Vranken.

  o Minor bugfixes (bootstrap):
    - Remember the directory server we fetched the consensus or previous
      certificates from, and use it to fetch future authority
      certificates. This change improves bootstrapping performance.
      Fixes bug 18963; bugfix on 0.2.8.1-alpha.

  o Minor bugfixes (circuits):
    - Make sure extend_info_from_router() is only called on servers.
      Fixes bug 19639; bugfix on 0.2.8.1-alpha.

  o Minor bugfixes (client, fascistfirewall):
    - Avoid spurious warnings when ReachableAddresses or FascistFirewall
      is set. Fixes bug 20306; bugfix on 0.2.8.2-alpha.

  o Minor bugfixes (client, unix domain sockets):
    - Disable IsolateClientAddr when using AF_UNIX backed SocksPorts as
      the client address is meaningless. Fixes bug 20261; bugfix
      on 0.2.6.3-alpha.

  o Minor bugfixes (code style):
    - Fix an integer signedness conversion issue in the case conversion
      tables. Fixes bug 19168; bugfix on 0.2.1.11-alpha.

  o Minor bugfixes (compilation):
    - Build correctly on versions of libevent2 without support for
      evutil_secure_rng_add_bytes(). Fixes bug 19904; bugfix
      on 0.2.5.4-alpha.
    - When building with Clang, use a full set of GCC warnings.
      (Previously, we included only a subset, because of the way we
      detected them.) Fixes bug 19216; bugfix on 0.2.0.1-alpha.
    - Detect Libevent2 functions correctly on systems that provide
      libevent2, but where libevent1 is linked with -levent. Fixes bug
      19904; bugfix on 0.2.2.24-alpha. Patch from Rubiate.
    - Run correctly when built on Windows build environments that
      require _vcsprintf(). Fixes bug 20560; bugfix on 0.2.2.11-alpha.

  o Minor bugfixes (configuration):
    - When parsing quoted configuration values from the torrc file,
      handle Windows line endings correctly. Fixes bug 19167; bugfix on
      0.2.0.16-alpha. Patch from "Pingl".

  o Minor bugfixes (directory authority):
    - Authorities now sort the "package" lines in their votes, for ease
      of debugging. (They are already sorted in consensus documents.)
      Fixes bug 18840; bugfix on 0.2.6.3-alpha.
    - Die with a more useful error when the operator forgets to place
      the authority_signing_key file into the keys directory. This
      avoids an uninformative assert & traceback about having an invalid
      key. Fixes bug 20065; bugfix on 0.2.0.1-alpha.
    - When allowing private addresses, mark Exits that only exit to
      private locations as such. Fixes bug 20064; bugfix
      on 0.2.2.9-alpha.
    - When parsing a detached signature, make sure we use the length of
      the digest algorithm instead of a hardcoded DIGEST256_LEN in
      order to avoid comparing bytes out-of-bounds with a smaller digest
      length such as SHA1. Fixes bug 19066; bugfix on 0.2.2.6-alpha.

  o Minor bugfixes (getpass):
    - Defensively fix a non-triggerable heap corruption at do_getpass()
      to protect ourselves from mistakes in the future. Fixes bug
      19223; bugfix on 0.2.7.3-rc. Bug found by Guido Vranken, patch
      by nherring.

  o Minor bugfixes (guard selection):
    - Don't mark guards as unreachable if connection_connect() fails.
      That function fails for local reasons, so it shouldn't reveal
      anything about the status of the guard. Fixes bug 14334; bugfix
      on 0.2.3.10-alpha.
    - Use a single entry guard even if the NumEntryGuards consensus
      parameter is not provided. Fixes bug 17688; bugfix
      on 0.2.5.6-alpha.

  o Minor bugfixes (hidden services):
    - Increase the minimum number of internal circuits we preemptively
      build from 2 to 3, so a circuit is available when a client
      connects to another onion service. Fixes bug 13239; bugfix
      on 0.1.0.1-rc.
    - Allow hidden services to run on IPv6 addresses even when the
      IPv6Exit option is not set. Fixes bug 18357; bugfix
      on 0.2.4.7-alpha.
    - Stop logging intro point details to the client log on certain
      error conditions. Fixed as part of bug 20012; bugfix on
      0.2.4.8-alpha. Patch by teor.
    - When deleting an ephemeral hidden service, close its intro points
      even if they are not completely open. Fixes bug 18604; bugfix
      on 0.2.7.1-alpha.
    - When configuring hidden services, check every hidden service
      directory's permissions. Previously, we only checked the last
      hidden service. Fixes bug 20529; bugfix on 0.2.6.2-alpha.

  o Minor bugfixes (IPv6, testing):
    - Check for IPv6 correctly on Linux when running test networks.
      Fixes bug 19905; bugfix on 0.2.7.3-rc; patch by teor.

  o Minor bugfixes (Linux seccomp2 sandbox):
    - Add permission to run the sched_yield() and sigaltstack() system
      calls, in order to support versions of Tor compiled with asan or
      ubsan code that use these calls. Now "sandbox 1" and
      "--enable-expensive-hardening" should be compatible on more
      systems. Fixes bug 20063; bugfix on 0.2.5.1-alpha.

  o Minor bugfixes (logging):
    - Downgrade a harmless log message about the
      pending_entry_connections list from "warn" to "info". Mitigates
      bug 19926.
    - Log a more accurate message when we fail to dump a microdescriptor.
      Fixes bug 17758; bugfix on 0.2.2.8-alpha. Patch from Daniel Pinto.
    - When logging a directory ownership mismatch, log the owning
      username correctly. Fixes bug 19578; bugfix on 0.2.2.29-beta.
    - When we are unable to remove the bw_accounting file, do not warn
      if the reason we couldn't remove it was that it didn't exist.
      Fixes bug 19964; bugfix on 0.2.5.4-alpha. Patch from pastly.

  o Minor bugfixes (memory leak):
    - Fix a series of slow memory leaks related to parsing torrc files
      and options. Fixes bug 19466; bugfix on 0.2.1.6-alpha.
    - Avoid a small memory leak when informing worker threads about
      rotated onion keys. Fixes bug 20401; bugfix on 0.2.6.3-alpha.
    - Fix a small memory leak when receiving AF_UNIX connections on a
      SocksPort. Fixes bug 20716; bugfix on 0.2.6.3-alpha.
    - When moving a signed descriptor object from a source to an
      existing destination, free the allocated memory inside that
      destination object. Fixes bug 20715; bugfix on 0.2.8.3-alpha.
    - Fix a memory leak and use-after-free error when removing entries
      from the sandbox's getaddrinfo() cache. Fixes bug 20710; bugfix on
      0.2.5.5-alpha. Patch from "cypherpunks".
    - Fix a small, uncommon memory leak that could occur when reading a
      truncated ed25519 key file. Fixes bug 18956; bugfix
      on 0.2.6.1-alpha.

  o Minor bugfixes (option parsing):
    - Count unix sockets when counting client listeners (SOCKS, Trans,
      NATD, and DNS). This has no user-visible behavior changes: these
      options are set once, and never read. Required for correct
      behavior in ticket 17178. Fixes bug 19677; bugfix on
      0.2.6.3-alpha. Patch by teor.

  o Minor bugfixes (options):
    - Check the consistency of UseEntryGuards and EntryNodes more
      reliably. Fixes bug 20074; bugfix on 0.2.4.12-alpha. Patch
      by teor.
    - Stop changing the configured value of UseEntryGuards on
      authorities and Tor2web clients. Fixes bug 20074; bugfix on
      commits 51fc6799 in 0.1.1.16-rc and acda1735 in 0.2.4.3-alpha.
      Patch by teor.

  o Minor bugfixes (relay):
    - Ensure relays don't make multiple connections during bootstrap.
      Fixes bug 20591; bugfix on 0.2.8.1-alpha.
    - Do not try to parallelize workers more than 16x without the user
      explicitly configuring us to do so, even if we do detect more than
      16 CPU cores. Fixes bug 19968; bugfix on 0.2.3.1-alpha.

  o Minor bugfixes (testing):
    - The test-stem and test-network makefile targets now depend only on
      the tor binary that they are testing. Previously, they depended on
      "make all". Fixes bug 18240; bugfix on 0.2.8.2-alpha. Based on a
      patch from "cypherpunks".
    - Allow clients to retry HSDirs much faster in test networks. Fixes
      bug 19702; bugfix on 0.2.7.1-alpha. Patch by teor.
    - Avoid a unit test failure on systems with over 16 detectable CPU
      cores. Fixes bug 19968; bugfix on 0.2.3.1-alpha.
    - Let backtrace tests work correctly under AddressSanitizer:
      disable ASAN's detection of segmentation faults while running
      test_bt.sh, so that we can make sure that our own backtrace
      generation code works. Fixes bug 18934; bugfix
      on 0.2.5.2-alpha. Patch from "cypherpunks".
    - Fix the test-network-all target on out-of-tree builds by using the
      correct path to the test driver script. Fixes bug 19421; bugfix
      on 0.2.7.3-rc.
    - Stop spurious failures in the local interface address discovery
      unit tests. Fixes bug 20634; bugfix on 0.2.8.1-alpha; patch by
      Neel Chauhan.
    - Use ECDHE ciphers instead of ECDH in tortls tests. LibreSSL has
      removed the ECDH ciphers which caused the tests to fail on
      platforms which use it. Fixes bug 20460; bugfix on 0.2.8.1-alpha.
    - The tor_tls_server_info_callback unit test no longer crashes when
      debug-level logging is turned on. Fixes bug 20041; bugfix
      on 0.2.8.1-alpha.

  o Minor bugfixes (time):
    - Improve overflow checks in tv_udiff and tv_mdiff. Fixes bug 19483;
      bugfix on all released tor versions.
    - When computing the difference between two times in milliseconds,
      we now round to the nearest millisecond correctly. Previously, we
      could sometimes round in the wrong direction. Fixes bug 19428;
      bugfix on 0.2.2.2-alpha.

  o Minor bugfixes (Tor2web):
    - Prevent Tor2web clients from running hidden services: these services
      are not anonymous due to the one-hop client paths. Fixes bug
      19678. Patch by teor.

  o Minor bugfixes (user interface):
    - Display a more accurate number of suppressed messages in the log
      rate-limiter. Previously, there was a potential integer overflow
      in the counter. Now, if the number of messages hits a maximum, the
      rate-limiter doesn't count any further. Fixes bug 19435; bugfix
      on 0.2.4.11-alpha.
    - Fix a typo in the passphrase prompt for the ed25519 identity key.
      Fixes bug 19503; bugfix on 0.2.7.2-alpha.

  o Code simplification and refactoring:
    - Remove redundant declarations of the MIN macro. Closes
      ticket 18889.
    - Rename tor_dup_addr() to tor_addr_to_str_dup() to avoid confusion.
      Closes ticket 18462; patch from "icanhasaccount".
    - Split the 600-line directory_handle_command_get function into
      separate functions for different URL types. Closes ticket 16698.

  o Documentation:
    - Add module-level internal documentation for 36 C files that
      previously didn't have a high-level overview. Closes ticket 20385.
    - Correct the IPv6 syntax in our documentation for the
      VirtualAddrNetworkIPv6 torrc option. Closes ticket 19743.
    - Correct the minimum bandwidth value in torrc.sample, and queue a
      corresponding change for torrc.minimal. Closes ticket 20085.
    - Fix spelling of "--enable-tor2web-mode" in the manpage. Closes
      ticket 19153. Patch from "U+039b".
    - Module-level documentation for several more modules. Closes
      tickets 19287 and 19290.
    - Document the --passphrase-fd option in the tor manpage. Fixes bug
      19504; bugfix on 0.2.7.3-rc.
    - Document the default PathsNeededToBuildCircuits value that's used
      by clients when the directory authorities don't set
      min_paths_for_circs_pct. Fixes bug 20117; bugfix on 0.2.4.10-alpha.
      Patch by teor, reported by Jesse V.
    - Fix manual for the User option: it takes a username, not a UID.
      Fixes bug 19122; bugfix on 0.0.2pre16 (the first version to have
      a manpage!).
    - Fix the description of the --passphrase-fd option in the
      tor-gencert manpage. The option is used to pass the number of a
      file descriptor to read the passphrase from, not to read the file
      descriptor from. Fixes bug 19505; bugfix on 0.2.0.20-alpha.

  o Removed code:
    - We no longer include the (dead, deprecated) bufferevent code in
      Tor. Closes ticket 19450. Based on a patch from "U+039b".

  o Removed features:
    - Remove support for "GET /tor/bytes.txt" DirPort request, and
      "GETINFO dir-usage" controller request, which were only available
      via a compile-time option in Tor anyway. Feature was added in
      0.2.2.1-alpha. Resolves ticket 19035.
    - There is no longer a compile-time option to disable support for
      TransPort. (If you don't want TransPort, just don't use it.) Patch
      from "U+039b". Closes ticket 19449.

  o Testing:
    - Run more workqueue tests as part of "make check". These had
      previously been implemented, but you needed to know special
      command-line options to enable them.
    - We now have unit tests for our code to reject zlib "compression
      bombs". (Fortunately, the code works fine.)


Changes in version 0.2.8.11 - 2016-12-08
  Tor 0.2.8.11 backports fixes for additional portability issues that
  could prevent Tor from building correctly on OSX Sierra, or with
  OpenSSL 1.1. Affected users should upgrade; others can safely stay
  with 0.2.8.10.

  o Minor bugfixes (portability):
    - Avoid compilation errors when building on OSX Sierra. Sierra began
      to support the getentropy() and clock_gettime() APIs, but created
      a few problems in doing so. Tor 0.2.9 has a more thorough set of
      workarounds; in 0.2.8, we are just using the /dev/urandom and mach
      monotonic time interfaces. Fixes bug 20865. Bugfix
      on 0.2.8.1-alpha.

  o Minor bugfixes (portability, backport from 0.2.9.5-alpha):
    - Fix compilation with OpenSSL 1.1 and less commonly-used CPU
      architectures. Closes ticket 20588.


Changes in version 0.2.8.10 - 2016-12-02
  Tor 0.2.8.10 backports a fix for a bug that would sometimes make clients
  unusable after they left standby mode. It also backports fixes for
  a few portability issues and a small but problematic memory leak.

  o Major bugfixes (client reliability, backport from 0.2.9.5-alpha):
    - When Tor leaves standby because of a new application request, open
      circuits as needed to serve that request. Previously, we would
      potentially wait a very long time. Fixes part of bug 19969; bugfix
      on 0.2.8.1-alpha.

  o Major bugfixes (client performance, backport from 0.2.9.5-alpha):
    - Clients now respond to new application stream requests immediately
      when they arrive, rather than waiting up to one second before
      starting to handle them. Fixes part of bug 19969; bugfix
      on 0.2.8.1-alpha.

  o Minor bugfixes (portability, backport from 0.2.9.6-rc):
    - Work around a bug in the OSX 10.12 SDK that would prevent us from
      successfully targeting earlier versions of OSX. Resolves
      ticket 20235.

  o Minor bugfixes (portability, backport from 0.2.9.5-alpha):
    - Fix implicit conversion warnings under OpenSSL 1.1. Fixes bug
      20551; bugfix on 0.2.1.1-alpha.

  o Minor bugfixes (relay, backport from 0.2.9.5-alpha):
    - Work around a memory leak in OpenSSL 1.1 when encoding public
      keys. Fixes bug 20553; bugfix on 0.0.2pre8.

  o Minor features (geoip):
    - Update geoip and geoip6 to the November 3 2016 Maxmind GeoLite2
      Country database.


Changes in version 0.2.8.9 - 2016-10-17
  Tor 0.2.8.9 backports a fix for a security hole in previous versions
  of Tor that would allow a remote attacker to crash a Tor client,
  hidden service, relay, or authority. All Tor users should upgrade to
  this version, or to 0.2.9.4-alpha. Patches will be released for older
  versions of Tor.

  o Major features (security fixes, also in 0.2.9.4-alpha):
    - Prevent a class of security bugs caused by treating the contents
      of a buffer chunk as if they were a NUL-terminated string. At
      least one such bug seems to be present in all currently used
      versions of Tor, and would allow an attacker to remotely crash
      most Tor instances, especially those compiled with extra compiler
      hardening. With this defense in place, such bugs can't crash Tor,
      though we should still fix them as they occur. Closes ticket
      20384 (TROVE-2016-10-001).

  o Minor features (geoip):
    - Update geoip and geoip6 to the October 4 2016 Maxmind GeoLite2
      Country database.


Changes in version 0.2.8.8 - 2016-09-23
  Tor 0.2.8.8 fixes two crash bugs present in previous versions of the
  0.2.8.x series. Relays running 0.2.8.x should upgrade, as should users
  who select public relays as their bridges.

  o Major bugfixes (crash):
    - Fix a complicated crash bug that could affect Tor clients
      configured to use bridges when replacing a networkstatus consensus
      in which one of their bridges was mentioned. OpenBSD users saw
      more crashes here, but all platforms were potentially affected.
      Fixes bug 20103; bugfix on 0.2.8.2-alpha.

  o Major bugfixes (relay, OOM handler):
    - Fix a timing-dependent assertion failure that could occur when we
      tried to flush from a circuit after having freed its cells because
      of an out-of-memory condition. Fixes bug 20203; bugfix on
      0.2.8.1-alpha. Thanks to "cypherpunks" for help diagnosing
      this one.

  o Minor feature (fallback directories):
    - Remove broken fallbacks from the hard-coded fallback directory
      list. Closes ticket 20190; patch by teor.

  o Minor features (geoip):
    - Update geoip and geoip6 to the September 6 2016 Maxmind GeoLite2
      Country database.


Changes in version 0.2.8.7 - 2016-08-24
  Tor 0.2.8.7 fixes an important bug related to the ReachableAddresses
  option in 0.2.8.6, and replaces a retiring bridge authority. Everyone
  who sets the ReachableAddresses option, and all bridges, are strongly
  encouraged to upgrade.

  o Directory authority changes:
    - The "Tonga" bridge authority has been retired; the new bridge
      authority is "Bifroest". Closes tickets 19728 and 19690.

  o Major bugfixes (client, security):
    - Only use the ReachableAddresses option to restrict the first hop
      in a path. In earlier versions of 0.2.8.x, it would apply to
      every hop in the path, with a possible degradation in anonymity
      for anyone using an uncommon ReachableAddress setting. Fixes bug
      19973; bugfix on 0.2.8.2-alpha.

  o Minor features (geoip):
    - Update geoip and geoip6 to the August 2 2016 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (compilation):
    - Remove an inappropriate "inline" in tortls.c that was causing
      warnings on older versions of GCC. Fixes bug 19903; bugfix
      on 0.2.8.1-alpha.

  o Minor bugfixes (fallback directories):
    - Avoid logging a NULL string pointer when loading fallback
      directory information. Fixes bug 19947; bugfix on 0.2.4.7-alpha
      and 0.2.8.1-alpha. Report and patch by "rubiate".


Changes in version 0.2.8.6 - 2016-08-02

  Tor 0.2.8.6 is the first stable version of the Tor 0.2.8 series.

  The Tor 0.2.8 series improves client bootstrapping performance,
  completes the authority-side implementation of improved identity
  keys for relays, and includes numerous bugfixes and performance
  improvements throughout the program. This release continues to
  improve the coverage of Tor's test suite.  For a full list of
  changes since Tor 0.2.7, see the ReleaseNotes file.

  Below is a list of the changes since Tor 0.2.7.

  o New system requirements:
    - Tor no longer attempts to support platforms where the "time_t"
      type is unsigned. (To the best of our knowledge, only OpenVMS does
      this, and Tor has never actually built on OpenVMS.) Closes
      ticket 18184.
    - Tor no longer supports versions of OpenSSL with a broken
      implementation of counter mode. (This bug was present in OpenSSL
      1.0.0, and was fixed in OpenSSL 1.0.0a.) Tor still detects, but no
      longer runs with, these versions.
    - Tor now uses Autoconf version 2.63 or later, and Automake 1.11 or
      later (released in 2008 and 2009 respectively). If you are
      building Tor from the git repository instead of from the source
      distribution, and your tools are older than this, you will need to
      upgrade. Closes ticket 17732.

  o Directory authority changes:
    - Update the V3 identity key for the dannenberg directory authority:
      it was changed on 18 November 2015. Closes task 17906. Patch
      by teor.
    - Urras is no longer a directory authority. Closes ticket 19271.

  o Major features (directory system):
    - Include a trial list of default fallback directories, based on an
      opt-in survey of suitable relays. Doing this should make clients
      bootstrap more quickly and reliably, and reduce the load on the
      directory authorities. Closes ticket 15775. Patch by teor.
      Candidates identified using an OnionOO script by weasel, teor,
      gsathya, and karsten.
    - Previously only relays that explicitly opened a directory port
      (DirPort) accepted directory requests from clients. Now all
      relays, with and without a DirPort, accept and serve tunneled
      directory requests that they receive through their ORPort. You can
      disable this behavior using the new DirCache option. Closes
      ticket 12538.
    - When bootstrapping multiple consensus downloads at a time, use the
      first one that starts downloading, and close the rest. This
      reduces failures when authorities or fallback directories are slow
      or down. Together with the code for feature 15775, this feature
      should reduces failures due to fallback churn. Implements ticket
      4483. Patch by teor. Implements IPv4 portions of proposal 210 by
      mikeperry and teor.

  o Major features (security, Linux):
    - When Tor starts as root on Linux and is told to switch user ID, it
      can now retain the capability to bind to low ports. By default,
      Tor will do this only when it's switching user ID and some low
      ports have been configured. You can change this behavior with the
      new option KeepBindCapabilities. Closes ticket 8195.

  o Major bugfixes (client, bootstrapping):
    - Check if bootstrap consensus downloads are still needed when the
      linked connection attaches. This prevents tor making unnecessary
      begindir-style connections, which are the only directory
      connections tor clients make since the fix for 18483 was merged.
    - Fix some edge cases where consensus download connections may not
      have been closed, even though they were not needed. Related to fix
      for 18809.
    - Make relays retry consensus downloads the correct number of times,
      rather than the more aggressive client retry count. Fixes part of
      ticket 18809.

  o Major bugfixes (dns proxy mode, crash):
    - Avoid crashing when running as a DNS proxy. Fixes bug 16248;
      bugfix on 0.2.0.1-alpha. Patch from "cypherpunks".

  o Major bugfixes (ed25519, voting):
    - Actually enable support for authorities to match routers by their
      Ed25519 identities. Previously, the code had been written, but
      some debugging code that had accidentally been left in the
      codebase made it stay turned off. Fixes bug 17702; bugfix
      on 0.2.7.2-alpha.
    - When collating votes by Ed25519 identities, authorities now
      include a "NoEdConsensus" flag if the ed25519 value (or lack
      thereof) for a server does not reflect the majority consensus.
      Related to bug 17668; bugfix on 0.2.7.2-alpha.
    - When generating a vote with keypinning disabled, never include two
      entries for the same ed25519 identity. This bug was causing
      authorities to generate votes that they could not parse when a
      router violated key pinning by changing its RSA identity but
      keeping its Ed25519 identity. Fixes bug 17668; fixes part of bug
      18318. Bugfix on 0.2.7.2-alpha.

  o Major bugfixes (key management):
    - If OpenSSL fails to generate an RSA key, do not retain a dangling
      pointer to the previous (uninitialized) key value. The impact here
      should be limited to a difficult-to-trigger crash, if OpenSSL is
      running an engine that makes key generation failures possible, or
      if OpenSSL runs out of memory. Fixes bug 19152; bugfix on
      0.2.1.10-alpha. Found by Yuan Jochen Kang, Suman Jana, and
      Baishakhi Ray.

  o Major bugfixes (security, client, DNS proxy):
    - Stop a crash that could occur when a client running with DNSPort
      received a query with multiple address types, and the first
      address type was not supported. Found and fixed by Scott Dial.
      Fixes bug 18710; bugfix on 0.2.5.4-alpha.

  o Major bugfixes (security, compilation):
    - Correctly detect compiler flags on systems where _FORTIFY_SOURCE
      is predefined. Previously, our use of -D_FORTIFY_SOURCE would
      cause a compiler warning, thereby making other checks fail, and
      needlessly disabling compiler-hardening support. Fixes one case of
      bug 18841; bugfix on 0.2.3.17-beta. Patch from "trudokal".
    - Repair hardened builds under the clang compiler. Previously, our
      use of _FORTIFY_SOURCE would conflict with clang's address
      sanitizer. Fixes bug 14821; bugfix on 0.2.5.4-alpha.

  o Major bugfixes (security, pointers):
    - Avoid a difficult-to-trigger heap corruption attack when extending
      a smartlist to contain over 16GB of pointers. Fixes bug 18162;
      bugfix on 0.1.1.11-alpha, which fixed a related bug incompletely.
      Reported by Guido Vranken.

  o Major bugfixes (testing):
    - Fix a bug that would block 'make test-network-all' on systems where
      IPv6 packets were lost. Fixes bug 19008; bugfix on 0.2.7.3-rc.

  o Major bugfixes (user interface):
    - Correctly give a warning in the cases where a relay is specified
      by nickname, and one such relay is found, but it is not officially
      Named. Fixes bug 19203; bugfix on 0.2.3.1-alpha.

  o Minor features (accounting):
    - Added two modes to the AccountingRule option: One for limiting
      only the number of bytes sent ("AccountingRule out"), and one for
      limiting only the number of bytes received ("AccountingRule in").
      Closes ticket 15989; patch from "unixninja92".

  o Minor features (bug-resistance):
    - Make Tor survive errors involving connections without a
      corresponding event object. Previously we'd fail with an
      assertion; now we produce a log message. Related to bug 16248.
    - Use tor_snprintf() and tor_vsnprintf() even in external and low-
      level code, to harden against accidental failures to NUL-
      terminate. Part of ticket 17852. Patch from jsturgix. Found
      with Flawfinder.

  o Minor features (build):
    - Detect systems with FreeBSD-derived kernels (such as GNU/kFreeBSD)
      as having possible IPFW support. Closes ticket 18448. Patch from
      Steven Chamberlain.
    - Since our build process now uses "make distcheck", we no longer
      force "make dist" to depend on "make check". Closes ticket 17893;
      patch from "cypherpunks".
    - Tor now builds once again with the recent OpenSSL 1.1 development
      branch (tested against 1.1.0-pre5 and 1.1.0-pre6-dev). We have been
      tracking OpenSSL 1.1 development as it has progressed, and fixing
      numerous compatibility issues as they arose. See tickets
      17549, 17921, 17984, 19499, and 18286.
    - When building manual pages, set the timezone to "UTC", so that the
      output is reproducible. Fixes bug 19558; bugfix on 0.2.2.9-alpha.
      Patch from intrigeri.

  o Minor features (clients):
    - Make clients, onion services, and bridge relays always use an
      encrypted begindir connection for directory requests. Resolves
      ticket 18483. Patch by teor.

  o Minor features (controller):
    - Add 'GETINFO exit-policy/reject-private/[default,relay]', so
      controllers can examine the the reject rules added by
      ExitPolicyRejectPrivate. This makes it easier for stem to display
      exit policies.
    - Adds the FallbackDir entries to 'GETINFO config/defaults'. Closes
      tickets 16774 and 17817. Patch by George Tankersley.
    - New 'GETINFO hs/service/desc/id/' command to retrieve a hidden
      service descriptor from a service's local hidden service
      descriptor cache. Closes ticket 14846.

  o Minor features (crypto):
    - Add SHA3 and SHAKE support to crypto.c. Closes ticket 17783.
    - Add SHA512 support to crypto.c. Closes ticket 17663; patch from
      George Tankersley.
    - Improve performance when hashing non-multiple of 8 sized buffers,
      based on Andrew Moon's public domain SipHash-2-4 implementation.
      Fixes bug 17544; bugfix on 0.2.5.3-alpha.
    - Validate the hard-coded Diffie-Hellman parameters and ensure that
      p is a safe prime, and g is a suitable generator. Closes
      ticket 18221.
    - When allocating a digest state object, allocate no more space than
      we actually need. Previously, we would allocate as much space as
      the state for the largest algorithm would need. This change saves
      up to 672 bytes per circuit. Closes ticket 17796.

  o Minor features (directory downloads):
    - Add UseDefaultFallbackDirs, which enables any hard-coded fallback
      directory mirrors. The default is 1; set it to 0 to disable
      fallbacks. Implements ticket 17576. Patch by teor.
    - Wait for busy authorities and fallback directories to become non-
      busy when bootstrapping. (A similar change was made in 6c443e987d
      for directory caches chosen from the consensus.) Closes ticket
      17864; patch by teor.

  o Minor features (geoip):
    - Update geoip and geoip6 to the July 6 2016 Maxmind GeoLite2
      Country database.

  o Minor features (hidden service directory):
    - Streamline relay-side hsdir handling: when relays consider whether
      to accept an uploaded hidden service descriptor, they no longer
      check whether they are one of the relays in the network that is
      "supposed" to handle that descriptor. Implements ticket 18332.

  o Minor features (IPv6):
    - Add ClientPreferIPv6DirPort, which is set to 0 by default. If set
      to 1, tor prefers IPv6 directory addresses.
    - Add ClientUseIPv4, which is set to 1 by default. If set to 0, tor
      avoids using IPv4 for client OR and directory connections.
    - Add address policy assume_action support for IPv6 addresses.
    - Add an argument 'ipv6=address:orport' to the DirAuthority and
      FallbackDir torrc options, to specify an IPv6 address for an
      authority or fallback directory. Add hard-coded ipv6 addresses for
      directory authorities that have them. Closes ticket 17327; patch
      from Nick Mathewson and teor.
    - Allow users to configure directory authorities and fallback
      directory servers with IPv6 addresses and ORPorts. Resolves
      ticket 6027.
    - Limit IPv6 mask bits to 128.
    - Make tor_ersatz_socketpair work on IPv6-only systems. Fixes bug
      17638; bugfix on 0.0.2pre8. Patch by teor.
    - Try harder to obey the IP version restrictions "ClientUseIPv4 0",
      "ClientUseIPv6 0", "ClientPreferIPv6ORPort", and
      "ClientPreferIPv6DirPort". Closes ticket 17840; patch by teor.
    - Warn when comparing against an AF_UNSPEC address in a policy, it's
      almost always a bug. Closes ticket 17863; patch by teor.
    - routerset_parse now accepts IPv6 literal addresses. Fixes bug
      17060; bugfix on 0.2.1.3-alpha. Patch by teor.

  o Minor features (Linux seccomp2 sandbox):
    - Reject attempts to change our Address with "Sandbox 1" enabled.
      Changing Address with Sandbox turned on would never actually work,
      but previously it would fail in strange and confusing ways. Found
      while fixing 18548.

  o Minor features (logging):
    - When logging to syslog, allow a tag to be added to the syslog
      identity (the string prepended to every log message). The tag can
      be configured with SyslogIdentityTag and defaults to none. Setting
      it to "foo" will cause logs to be tagged as "Tor-foo". Closes
      ticket 17194.

  o Minor features (portability):
    - Use timingsafe_memcmp() where available. Closes ticket 17944;
      patch from <logan@hackers.mu>.

  o Minor features (relay, address discovery):
    - Add a family argument to get_interface_addresses_raw() and
      subfunctions to make network interface address interogation more
      efficient. Now Tor can specifically ask for IPv4, IPv6 or both
      types of interfaces from the operating system. Resolves
      ticket 17950.
    - When get_interface_address6_list(.,AF_UNSPEC,.) is called and
      fails to enumerate interface addresses using the platform-specific
      API, have it rely on the UDP socket fallback technique to try and
      find out what IP addresses (both IPv4 and IPv6) our machine has.
      Resolves ticket 17951.

  o Minor features (replay cache):
    - The replay cache now uses SHA256 instead of SHA1. Implements
      feature 8961. Patch by teor, issue reported by rransom.

  o Minor features (robustness):
    - Exit immediately with an error message if the code attempts to use
      Libevent without having initialized it. This should resolve some
      frequently-made mistakes in our unit tests. Closes ticket 18241.

  o Minor features (security, clock):
    - Warn when the system clock appears to move back in time (when the
      state file was last written in the future). Tor doesn't know that
      consensuses have expired if the clock is in the past. Patch by
      teor. Implements ticket 17188.

  o Minor features (security, exit policies):
    - ExitPolicyRejectPrivate now rejects more private addresses by
      default. Specifically, it now rejects the relay's outbound bind
      addresses (if configured), and the relay's configured port
      addresses (such as ORPort and DirPort). Fixes bug 17027; bugfix on
      0.2.0.11-alpha. Patch by teor.

  o Minor features (security, memory erasure):
    - Make memwipe() do nothing when passed a NULL pointer or buffer of
      zero size. Check size argument to memwipe() for underflow. Fixes
      bug 18089; bugfix on 0.2.3.25 and 0.2.4.6-alpha. Reported by "gk",
      patch by teor.
    - Set the unused entries in a smartlist to NULL. This helped catch
      a (harmless) bug, and shouldn't affect performance too much.
      Implements ticket 17026.
    - Use SecureMemoryWipe() function to securely clean memory on
      Windows. Previously we'd use OpenSSL's OPENSSL_cleanse() function.
      Implements feature 17986.
    - Use explicit_bzero or memset_s when present. Previously, we'd use
      OpenSSL's OPENSSL_cleanse() function. Closes ticket 7419; patches
      from <logan@hackers.mu> and <selven@hackers.mu>.

  o Minor features (security, RNG):
    - Adjust Tor's use of OpenSSL's RNG APIs so that they absolutely,
      positively are not allowed to fail. Previously we depended on
      internal details of OpenSSL's behavior. Closes ticket 17686.
    - Never use the system entropy output directly for anything besides
      seeding the PRNG. When we want to generate important keys, instead
      of using system entropy directly, we now hash it with the PRNG
      stream. This may help resist certain attacks based on broken OS
      entropy implementations. Closes part of ticket 17694.
    - Use modern system calls (like getentropy() or getrandom()) to
      generate strong entropy on platforms that have them. Closes
      ticket 13696.

  o Minor features (security, win32):
    - Set SO_EXCLUSIVEADDRUSE on Win32 to avoid a local port-stealing
      attack. Fixes bug 18123; bugfix on all tor versions. Patch
      by teor.

  o Minor features (unix domain sockets):
    - Add a new per-socket option, RelaxDirModeCheck, to allow creating
      Unix domain sockets without checking the permissions on the parent
      directory. (Tor checks permissions by default because some
      operating systems only check permissions on the parent directory.
      However, some operating systems do look at permissions on the
      socket, and tor's default check is unneeded.) Closes ticket 18458.
      Patch by weasel.

  o Minor features (unix file permissions):
    - Defer creation of Unix sockets until after setuid. This avoids
      needing CAP_CHOWN and CAP_FOWNER when using systemd's
      CapabilityBoundingSet, or chown and fowner when using SELinux.
      Implements part of ticket 17562. Patch from Jamie Nguyen.
    - If any directory created by Tor is marked as group readable, the
      filesystem group is allowed to be either the default GID or the
      root user. Allowing root to read the DataDirectory prevents the
      need for CAP_READ_SEARCH when using systemd's
      CapabilityBoundingSet, or dac_read_search when using SELinux.
      Implements part of ticket 17562. Patch from Jamie Nguyen.
    - Introduce a new DataDirectoryGroupReadable option. If it is set to
      1, the DataDirectory will be made readable by the default GID.
      Implements part of ticket 17562. Patch from Jamie Nguyen.

  o Minor bugfixes (accounting):
    - The max bandwidth when using 'AccountRule sum' is now correctly
      logged. Fixes bug 18024; bugfix on 0.2.6.1-alpha. Patch
      from "unixninja92".

  o Minor bugfixes (assert, portability):
    - Fix an assertion failure in memarea.c on systems where "long" is
      shorter than the size of a pointer. Fixes bug 18716; bugfix
      on 0.2.1.1-alpha.

  o Minor bugfixes (bootstrap):
    - Consistently use the consensus download schedule for authority
      certificates. Fixes bug 18816; bugfix on 0.2.4.13-alpha.

  o Minor bugfixes (build):
    - Avoid spurious failures from configure files related to calling
      exit(0) in TOR_SEARCH_LIBRARY. Fixes bug 18626; bugfix on
      0.2.0.1-alpha. Patch from "cypherpunks".
    - Do not link the unit tests against both the testing and non-
      testing versions of the static libraries. Fixes bug 18490; bugfix
      on 0.2.7.1-alpha.
    - Resolve warnings when building on systems that are concerned with
      signed char. Fixes bug 18728; bugfix on 0.2.7.2-alpha
      and 0.2.6.1-alpha.
    - Silence spurious clang-scan warnings in the ed25519_donna code by
      explicitly initializing some objects. Fixes bug 18384; bugfix on
      0.2.7.2-alpha. Patch by teor.
    - When libscrypt.h is found, but no libscrypt library can be linked,
      treat libscrypt as absent. Fixes bug 19161; bugfix
      on 0.2.6.1-alpha.
    - Cause the unit tests to compile correctly on mingw64 versions that
      lack sscanf. Fixes bug 19213; bugfix on 0.2.7.1-alpha.
    - Don't try to use the pthread_condattr_setclock() function unless
      it actually exists. Fixes compilation on NetBSD-6.x. Fixes bug
      17819; bugfix on 0.2.6.3-alpha.
    - Fix backtrace compilation on FreeBSD. Fixes bug 17827; bugfix
      on 0.2.5.2-alpha.
    - Fix search for libevent libraries on OpenBSD (and other systems
      that install libevent 1 and libevent 2 in parallel). Fixes bug
      16651; bugfix on 0.1.0.7-rc. Patch from "rubiate".
    - Isolate environment variables meant for tests from the rest of the
      build system. Fixes bug 17818; bugfix on 0.2.7.3-rc.
    - Mark all object files that include micro-revision.i as depending
      on it, so as to make parallel builds more reliable. Fixes bug
      17826; bugfix on 0.2.5.1-alpha.
    - Remove config.log only from make distclean, not from make clean.
      Fixes bug 17924; bugfix on 0.2.4.1-alpha.
    - Replace usage of 'INLINE' with 'inline'. Fixes bug 17804; bugfix
      on 0.0.2pre8.
    - Remove an #endif from configure.ac so that we correctly detect the
      presence of in6_addr.s6_addr32. Fixes bug 17923; bugfix
      on 0.2.0.13-alpha.

  o Minor bugfixes (client, bootstrap):
    - Count receipt of new microdescriptors as progress towards
      bootstrapping. Previously, with EntryNodes set, Tor might not
      successfully repopulate the guard set on bootstrapping. Fixes bug
      16825; bugfix on 0.2.3.1-alpha.

  o Minor bugfixes (code correctness):
    - Fix a bad memory handling bug that would occur if we had queued a
      cell on a channel's incoming queue. Fortunately, we can't actually
      queue a cell like that as our code is constructed today, but it's
      best to avoid this kind of error, even if there isn't any code
      that triggers it today. Fixes bug 18570; bugfix on 0.2.4.4-alpha.
    - Assert that allocated memory held by the reputation code is freed
      according to its internal counters. Fixes bug 17753; bugfix
      on 0.1.1.1-alpha.
    - Assert when the TLS contexts fail to initialize. Fixes bug 17683;
      bugfix on 0.0.6.
    - Update to the latest version of Trunnel, which tries harder to
      avoid generating code that can invoke memcpy(p,NULL,0). Bug found
      by clang address sanitizer. Fixes bug 18373; bugfix
      on 0.2.7.2-alpha.
    - When closing an entry connection, generate a warning if we should
      have sent an end cell for it but we haven't. Fixes bug 17876;
      bugfix on 0.2.3.2-alpha.

  o Minor bugfixes (configuration):
    - Fix a tiny memory leak when parsing a port configuration ending in
      ":auto". Fixes bug 18374; bugfix on 0.2.3.3-alpha.

  o Minor bugfixes (containers):
    - If we somehow attempt to construct a heap with more than
      1073741822 elements, avoid an integer overflow when maintaining
      the heap property. Fixes bug 18296; bugfix on 0.1.2.1-alpha.

  o Minor bugfixes (controller, microdescriptors):
    - Make GETINFO dir/status-vote/current/consensus conform to the
      control specification by returning "551 Could not open cached
      consensus..." when not caching consensuses. Fixes bug 18920;
      bugfix on 0.2.2.6-alpha.

  o Minor bugfixes (crypto):
    - Check the return value of HMAC() and assert on failure. Fixes bug
      17658; bugfix on 0.2.3.6-alpha. Patch by teor.

  o Minor bugfixes (directories):
    - When fetching extrainfo documents, compare their SHA256 digests
      and Ed25519 signing key certificates with the routerinfo that led
      us to fetch them, rather than with the most recent routerinfo.
      Otherwise we generate many spurious warnings about mismatches.
      Fixes bug 17150; bugfix on 0.2.7.2-alpha.
    - When generating a URL for a directory server on an IPv6 address,
      wrap the IPv6 address in square brackets. Fixes bug 18051; bugfix
      on 0.2.3.9-alpha. Patch from Malek.

  o Minor bugfixes (downloading):
    - Predict more correctly whether we'll be downloading over HTTP when
      we determine the maximum length of a URL. This should avoid a
      "BUG" warning about the Squid HTTP proxy and its URL limits. Fixes
      bug 19191.

  o Minor bugfixes (exit policies, security):
    - Refresh an exit relay's exit policy when interface addresses
      change. Previously, tor only refreshed the exit policy when the
      configured external address changed. Fixes bug 18208; bugfix on
      0.2.7.3-rc. Patch by teor.

  o Minor bugfixes (fallback directories):
    - Mark fallbacks as "too busy" when they return a 503 response,
      rather than just marking authorities. Fixes bug 17572; bugfix on
      0.2.4.7-alpha. Patch by teor.
    - When requesting extrainfo descriptors from a trusted directory
      server, check whether it is an authority or a fallback directory
      which supports extrainfo descriptors. Fixes bug 18489; bugfix on
      0.2.4.7-alpha. Reported by atagar, patch by teor.

  o Minor bugfixes (hidden service, client):
    - Handle the case where the user makes several fast consecutive
      requests to the same .onion address. Previously, the first six
      requests would each trigger a descriptor fetch, each picking a
      directory (there are 6 overall) and the seventh one would fail
      because no directories were left, thereby triggering a close on
      all current directory connections asking for the hidden service.
      The solution here is to not close the connections if we have
      pending directory fetches. Fixes bug 15937; bugfix
      on 0.2.7.1-alpha.

  o Minor bugfixes (hidden service, control port):
    - Add the onion address to the HS_DESC event for the UPLOADED action
      both on success or failure. It was previously hardcoded with
      UNKNOWN. Fixes bug 16023; bugfix on 0.2.7.2-alpha.

  o Minor bugfixes (hidden service, directory):
    - Bridges now refuse "rendezvous2" (hidden service descriptor)
      publish attempts. Suggested by ticket 18332.

  o Minor bugfixes (IPv6):
    - Update the limits in max_dl_per_request for IPv6 address length.
      Fixes bug 17573; bugfix on 0.2.1.5-alpha.

  o Minor bugfixes (Linux seccomp2 sandbox):
    - Allow more syscalls when running with "Sandbox 1" enabled:
      sysinfo, getsockopt(SO_SNDBUF), and setsockopt(SO_SNDBUFFORCE). On
      some systems, these are required for Tor to start. Fixes bug
      18397; bugfix on 0.2.5.1-alpha. Patch from Daniel Pinto.
    - Allow IPPROTO_UDP datagram sockets when running with "Sandbox 1",
      so that get_interface_address6_via_udp_socket_hack() can work.
      Fixes bug 19660; bugfix on 0.2.5.1-alpha.
    - Allow the setrlimit syscall, and the prlimit and prlimit64
      syscalls, which some libc implementations use under the hood.
      Fixes bug 15221; bugfix on 0.2.5.1-alpha.
    - Avoid a 10-second delay when starting as a client with "Sandbox 1"
      enabled and no DNS resolvers configured. This should help TAILS
      start up faster. Fixes bug 18548; bugfix on 0.2.5.1-alpha.
    - Fix a crash when using offline master ed25519 keys with the Linux
      seccomp2 sandbox enabled. Fixes bug 17675; bugfix on 0.2.7.3-rc.
    - Allow statistics to be written to disk when "Sandbox 1" is
      enabled. Fixes bugs 19556 and 19957; bugfix on 0.2.5.1-alpha and
      0.2.6.1-alpha respectively.

  o Minor bugfixes (logging):
    - In log messages that include a function name, use __FUNCTION__
      instead of __PRETTY_FUNCTION__. In GCC, these are synonymous, but
      with clang __PRETTY_FUNCTION__ has extra information we don't
      need. Fixes bug 16563; bugfix on 0.0.2pre8. Fix by Tom van
      der Woerdt.
    - Remove needless quotes from a log message about unparseable
      addresses. Fixes bug 17843; bugfix on 0.2.3.3-alpha.
    - Scrub service name in "unrecognized service ID" log messages.
      Fixes bug 18600; bugfix on 0.2.4.11-alpha.
    - When logging information about an unparsable networkstatus vote or
      consensus, do not say "vote" when we mean consensus. Fixes bug
      18368; bugfix on 0.2.0.8-alpha.
    - When we can't generate a signing key because OfflineMasterKey is
      set, do not imply that we should have been able to load it. Fixes
      bug 18133; bugfix on 0.2.7.2-alpha.
    - When logging a malformed hostname received through socks4, scrub
      it if SafeLogging says we should. Fixes bug 17419; bugfix
      on 0.1.1.16-rc.

  o Minor bugfixes (memory safety):
    - Avoid freeing an uninitialized pointer when opening a socket fails
      in get_interface_addresses_ioctl(). Fixes bug 18454; bugfix on
      0.2.3.11-alpha. Reported by toralf and "cypherpunks", patch
      by teor.
    - Fix a memory leak in "tor --list-fingerprint". Fixes part of bug
      18672; bugfix on 0.2.5.1-alpha.
    - Fix a memory leak in tor-gencert. Fixes part of bug 18672; bugfix
      on 0.2.0.1-alpha.

  o Minor bugfixes (pluggable transports):
    - Avoid reporting a spurious error when we decide that we don't need
      to terminate a pluggable transport because it has already exited.
      Fixes bug 18686; bugfix on 0.2.5.5-alpha.

  o Minor bugfixes (pointer arithmetic):
    - Fix a bug in memarea_alloc() that could have resulted in remote
      heap write access, if Tor had ever passed an unchecked size to
      memarea_alloc(). Fortunately, all the sizes we pass to
      memarea_alloc() are pre-checked to be less than 128 kilobytes.
      Fixes bug 19150; bugfix on 0.2.1.1-alpha. Bug found by
      Guido Vranken.

  o Minor bugfixes (private directory):
    - Prevent a race condition when creating private directories. Fixes
      part of bug 17852; bugfix on 0.0.2pre13. Part of ticket 17852.
      Patch from jsturgix. Found with Flawfinder.

  o Minor bugfixes (relays):
    - Check that both the ORPort and DirPort (if present) are reachable
      before publishing a relay descriptor. Otherwise, relays publish a
      descriptor with DirPort 0 when the DirPort reachability test takes
      longer than the ORPort reachability test. Fixes bug 18050; bugfix
      on 0.1.0.1-rc. Reported by "starlight", patch by teor.
    - Resolve some edge cases where we might launch an ORPort
      reachability check even when DisableNetwork is set. Noticed while
      fixing bug 18616; bugfix on 0.2.3.9-alpha.

  o Minor bugfixes (relays, hidden services):
    - Refuse connection requests to private OR addresses unless
      ExtendAllowPrivateAddresses is set. Previously, tor would connect,
      then refuse to send any cells to a private address. Fixes bugs
      17674 and 8976; bugfix on 0.2.3.21-rc. Patch by teor.

  o Minor bugfixes (security, hidden services):
    - Prevent hidden services connecting to client-supplied rendezvous
      addresses that are reserved as internal or multicast. Fixes bug
      8976; bugfix on 0.2.3.21-rc. Patch by dgoulet and teor.

  o Minor bugfixes (statistics):
    - Consistently check for overflow in round_*_to_next_multiple_of
      functions, and add unit tests with additional and maximal values.
      Fixes part of bug 13192; bugfix on 0.2.2.1-alpha.
    - Handle edge cases in the laplace functions: avoid division by
      zero, avoid taking the log of zero, and silence clang type
      conversion warnings using round and trunc. Add unit tests for edge
      cases with maximal values. Fixes part of bug 13192; bugfix
      on 0.2.6.2-alpha.
    - We now include consensus downloads via IPv6 in our directory-
      request statistics. Fixes bug 18460; bugfix on 0.2.3.14-alpha.

  o Minor bugfixes (test networks, IPv6):
    - Allow internal IPv6 addresses in descriptors in test networks.
      Fixes bug 17153; bugfix on 0.2.3.16-alpha. Patch by teor, reported
      by karsten.

  o Minor bugfixes (testing):
    - Check the full results of SHA256 and SHA512 digests in the unit
      tests. Bugfix on 0.2.2.4-alpha. Patch by teor.
    - Fix a memory leak in the ntor test. Fixes bug 17778; bugfix
      on 0.2.4.8-alpha.
    - Fix a small memory leak that would occur when the
      TestingEnableCellStatsEvent option was turned on. Fixes bug 18673;
      bugfix on 0.2.5.2-alpha.
    - Make unit tests pass on IPv6-only systems, and systems without
      localhost addresses (like some FreeBSD jails). Fixes bug 17632;
      bugfix on 0.2.7.3-rc. Patch by teor.
    - The test for log_heartbeat was incorrectly failing in timezones
      with non-integer offsets. Instead of comparing the end of the time
      string against a constant, compare it to the output of
      format_local_iso_time when given the correct input. Fixes bug
      18039; bugfix on 0.2.5.4-alpha.
    - We no longer disable assertions in the unit tests when coverage is
      enabled. Instead, we require you to say --disable-asserts-in-tests
      to the configure script if you need assertions disabled in the
      unit tests (for example, if you want to perform branch coverage).
      Fixes bug 18242; bugfix on 0.2.7.1-alpha.

  o Minor bugfixes (time handling):
    - When correcting a corrupt 'struct tm' value, fill in the tm_wday
      field. Otherwise, our unit tests crash on Windows. Fixes bug
      18977; bugfix on 0.2.2.25-alpha.
    - Avoid overflow in tor_timegm when parsing dates in and after 2038
      on platforms with 32-bit time_t. Fixes bug 18479; bugfix on
      0.0.2pre14. Patch by teor.

  o Minor bugfixes (tor-gencert):
    - Correctly handle the case where an authority operator enters a
      passphrase but sends an EOF before sending a newline. Fixes bug
      17443; bugfix on 0.2.0.20-rc. Found by junglefowl.

  o Code simplification and refactoring:
    - Clean up a little duplicated code in
      crypto_expand_key_material_TAP(). Closes ticket 17587; patch
      from "pfrankw".
    - Decouple the list of streams waiting to be attached to circuits
      from the overall connection list. This change makes it possible to
      attach streams quickly while simplifying Tor's callgraph and
      avoiding O(N) scans of the entire connection list. Closes
      ticket 17590.
    - Extract the more complicated parts of circuit_mark_for_close()
      into a new function that we run periodically before circuits are
      freed. This change removes more than half of the functions
      currently in the "blob". Closes ticket 17218.
    - Move logging of redundant policy entries in
      policies_parse_exit_policy_internal into its own function. Closes
      ticket 17608; patch from "juce".
    - Quote all the string interpolations in configure.ac -- even those
      which we are pretty sure can't contain spaces. Closes ticket
      17744. Patch from zerosion.
    - Remove code for configuring OpenSSL dynamic locks; OpenSSL doesn't
      use them. Closes ticket 17926.
    - Remove specialized code for non-inplace AES_CTR. 99% of our AES is
      inplace, so there's no need to have a separate implementation for
      the non-inplace code. Closes ticket 18258. Patch from Malek.
    - Simplify return types for some crypto functions that can't
      actually fail. Patch from Hassan Alsibyani. Closes ticket 18259.
    - When a direct directory request fails immediately on launch,
      instead of relaunching that request from inside the code that
      launches it, instead mark the connection for teardown. This change
      simplifies Tor's callback and prevents the directory-request
      launching code from invoking itself recursively. Closes
      ticket 17589.

  o Documentation:
    - Add a description of the correct use of the '--keygen' command-
      line option. Closes ticket 17583; based on text by 's7r'.
    - Change build messages to refer to "Fedora" instead of "Fedora
      Core", and "dnf" instead of "yum". Closes tickets 18459 and 18426.
      Patches from "icanhasaccount" and "cypherpunks".
    - Document the contents of the 'datadir/keys' subdirectory in the
      manual page. Closes ticket 17621.
    - Document the minimum HeartbeatPeriod value. Closes ticket 15638.
    - Explain actual minima for BandwidthRate. Closes ticket 16382.
    - Fix a minor formatting typo in the manpage. Closes ticket 17791.
    - Mention torspec URL in the manpage and point the reader to it
      whenever we mention a document that belongs in torspce. Fixes
      issue 17392.
    - Stop recommending use of nicknames to identify relays in our
      MapAddress documentation. Closes ticket 18312.

  o Removed features:
    - Remove client-side support for connecting to Tor relays running
      versions of Tor before 0.2.3.6-alpha. These relays didn't support
      the v3 TLS handshake protocol, and are no longer allowed on the
      Tor network. Implements the client side of ticket 11150. Based on
      patches by Tom van der Woerdt.
    - We no longer maintain an internal freelist in memarea.c.
      Allocators should be good enough to make this code unnecessary,
      and it's doubtful that it ever had any performance benefit.

  o Testing:
    - Add unit tests to check for common RNG failure modes, such as
      returning all zeroes, identical values, or incrementing values
      (OpenSSL's rand_predictable feature). Patch by teor.
    - Always test both ed25519 backends, so that we can be sure that our
      batch-open replacement code works. Part of ticket 16794.
    - Cover dns_resolve_impl() in dns.c with unit tests. Implements a
      portion of ticket 16831.
    - Fix several warnings from clang's address sanitizer produced in
      the unit tests.
    - Log more information when the backtrace tests fail. Closes ticket
      17892. Patch from "cypherpunks."
    - More unit tests for compat_libevent.c, procmon.c, tortls.c,
      util_format.c, directory.c, and options_validate.c. Closes tickets
      17075, 17082, 17084, 17003, and 17076 respectively. Patches from
      Ola Bini.
    - Treat backtrace test failures as expected on FreeBSD until we
      solve bug 17808. Closes ticket 18204.
    - Unit tests for directory_handle_command_get. Closes ticket 17004.
      Patch from Reinaldo de Souza Jr.


Changes in version 0.2.7.6 - 2015-12-10
  Tor version 0.2.7.6 fixes a major bug in entry guard selection, as
  well as a minor bug in hidden service reliability.

  o Major bugfixes (guard selection):
    - Actually look at the Guard flag when selecting a new directory
      guard. When we implemented the directory guard design, we
      accidentally started treating all relays as if they have the Guard
      flag during guard selection, leading to weaker anonymity and worse
      performance. Fixes bug 17772; bugfix on 0.2.4.8-alpha. Discovered
      by Mohsen Imani.

  o Minor features (geoip):
    - Update geoip and geoip6 to the December 1 2015 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (compilation):
    - When checking for net/pfvar.h, include netinet/in.h if possible.
      This fixes transparent proxy detection on OpenBSD. Fixes bug
      17551; bugfix on 0.1.2.1-alpha. Patch from "rubiate".
    - Fix a compilation warning with Clang 3.6: Do not check the
      presence of an address which can never be NULL. Fixes bug 17781.

  o Minor bugfixes (correctness):
    - When displaying an IPv6 exit policy, include the mask bits
      correctly even when the number is greater than 31. Fixes bug
      16056; bugfix on 0.2.4.7-alpha. Patch from "gturner".
    - The wrong list was used when looking up expired intro points in a
      rend service object, causing what we think could be reachability
      issues for hidden services, and triggering a BUG log. Fixes bug
      16702; bugfix on 0.2.7.2-alpha.
    - Fix undefined behavior in the tor_cert_checksig function. Fixes
      bug 17722; bugfix on 0.2.7.2-alpha.


Changes in version 0.2.7.5 - 2015-11-20
  The Tor 0.2.7 release series is dedicated to the memory of Tor user
  and privacy advocate Caspar Bowden (1961-2015). Caspar worked
  tirelessly to advocate human rights regardless of national borders,
  and oppose the encroachments of mass surveillance. He opposed national
  exceptionalism, he brought clarity to legal and policy debates, he
  understood and predicted the impact of mass surveillance on the world,
  and he laid the groundwork for resisting it. While serving on the Tor
  Project's board of directors, he brought us his uncompromising focus
  on technical excellence in the service of humankind. Caspar was an
  inimitable force for good and a wonderful friend. He was kind,
  humorous, generous, gallant, and believed we should protect one
  another without exception. We honor him here for his ideals, his
  efforts, and his accomplishments. Please honor his memory with works
  that would make him proud.

  Tor 0.2.7.5 is the first stable release in the Tor 0.2.7 series.

  The 0.2.7 series adds a more secure identity key type for relays,
  improves cryptography performance, resolves several longstanding
  hidden-service performance issues, improves controller support for
  hidden services, and includes small bugfixes and performance
  improvements throughout the program. This release series also includes
  more tests than before, and significant simplifications to which parts
  of Tor invoke which others. For a full list of changes, see below.

  o New system requirements:
    - Tor no longer includes workarounds to support Libevent versions
      before 1.3e. Libevent 2.0 or later is recommended. Closes
      ticket 15248.
    - Tor no longer supports copies of OpenSSL that are missing support
      for Elliptic Curve Cryptography. (We began using ECC when
      available in 0.2.4.8-alpha, for more safe and efficient key
      negotiation.) In particular, support for at least one of P256 or
      P224 is now required, with manual configuration needed if only
      P224 is available. Resolves ticket 16140.
    - Tor no longer supports versions of OpenSSL before 1.0. (If you are
      on an operating system that has not upgraded to OpenSSL 1.0 or
      later, and you compile Tor from source, you will need to install a
      more recent OpenSSL to link Tor against.) These versions of
      OpenSSL are still supported by the OpenSSL, but the numerous
      cryptographic improvements in later OpenSSL releases makes them a
      clear choice. Resolves ticket 16034.

  o Major features (controller):
    - Add the ADD_ONION and DEL_ONION commands that allow the creation
      and management of hidden services via the controller. Closes
      ticket 6411.
    - New "GETINFO onions/current" and "GETINFO onions/detached"
      commands to get information about hidden services created via the
      controller. Part of ticket 6411.
    - New HSFETCH command to launch a request for a hidden service
      descriptor. Closes ticket 14847.
    - New HSPOST command to upload a hidden service descriptor. Closes
      ticket 3523. Patch by "DonnchaC".

  o Major features (Ed25519 identity keys, Proposal 220):
    - Add support for offline encrypted Ed25519 master keys. To use this
      feature on your tor relay, run "tor --keygen" to make a new master
      key (or to make a new signing key if you already have a master
      key). Closes ticket 13642.
    - All relays now maintain a stronger identity key, using the Ed25519
      elliptic curve signature format. This master key is designed so
      that it can be kept offline. Relays also generate an online
      signing key, and a set of other Ed25519 keys and certificates.
      These are all automatically regenerated and rotated as needed.
      Implements part of ticket 12498.
    - Directory authorities now vote on Ed25519 identity keys along with
      RSA1024 keys. Implements part of ticket 12498.
    - Directory authorities track which Ed25519 identity keys have been
      used with which RSA1024 identity keys, and do not allow them to
      vary freely. Implements part of ticket 12498.
    - Microdescriptors now include Ed25519 identity keys. Implements
      part of ticket 12498.
    - Add a --newpass option to allow changing or removing the
      passphrase of an encrypted key with tor --keygen. Implements part
      of ticket 16769.
    - Add a new OfflineMasterKey option to tell Tor never to try loading
      or generating a secret Ed25519 identity key. You can use this in
      combination with tor --keygen to manage offline and/or encrypted
      Ed25519 keys. Implements ticket 16944.
    - On receiving a HUP signal, check to see whether the Ed25519
      signing key has changed, and reload it if so. Closes ticket 16790.
    - Significant usability improvements for Ed25519 key management. Log
      messages are better, and the code can recover from far more
      failure conditions. Thanks to "s7r" for reporting and diagnosing
      so many of these!

  o Major features (ECC performance):
    - Improve the runtime speed of Ed25519 signature verification by
      using Ed25519-donna's batch verification support. Implements
      ticket 16533.
    - Improve the speed of Ed25519 operations and Curve25519 keypair
      generation when built targeting 32 bit x86 platforms with SSE2
      available. Implements ticket 16535.
    - Improve the runtime speed of Ed25519 operations by using the
      public-domain Ed25519-donna by Andrew M. ("floodyberry").
      Implements ticket 16467.
    - Improve the runtime speed of the ntor handshake by using an
      optimized curve25519 basepoint scalarmult implementation from the
      public-domain Ed25519-donna by Andrew M. ("floodyberry"), based on
      ideas by Adam Langley. Implements ticket 9663.

  o Major features (Hidden services):
    - Hidden services, if using the EntryNodes option, are required to
      use more than one EntryNode, in order to avoid a guard discovery
      attack. (This would only affect people who had configured hidden
      services and manually specified the EntryNodes option with a
      single entry-node. The impact was that it would be easy to
      remotely identify the guard node used by such a hidden service.
      See ticket for more information.) Fixes ticket 14917.
    - Add the torrc option HiddenServiceNumIntroductionPoints, to
      specify a fixed number of introduction points. Its maximum value
      is 10 and default is 3. Using this option can increase a hidden
      service's reliability under load, at the cost of making it more
      visible that the hidden service is facing extra load. Closes
      ticket 4862.
    - Remove the adaptive algorithm for choosing the number of
      introduction points, which used to change the number of
      introduction points (poorly) depending on the number of
      connections the HS sees. Closes ticket 4862.

  o Major features (onion key cross-certification):
    - Relay descriptors now include signatures of their own identity
      keys, made using the TAP and ntor onion keys. These signatures
      allow relays to prove ownership of their own onion keys. Because
      of this change, microdescriptors will no longer need to include
      RSA identity keys. Implements proposal 228; closes ticket 12499.

  o Major bugfixes (client-side privacy, also in 0.2.6.9):
    - Properly separate out each SOCKSPort when applying stream
      isolation. The error occurred because each port's session group
      was being overwritten by a default value when the listener
      connection was initialized. Fixes bug 16247; bugfix on
      0.2.6.3-alpha. Patch by "jojelino".

  o Major bugfixes (hidden service clients, stability, also in 0.2.6.10):
    - Stop refusing to store updated hidden service descriptors on a
      client. This reverts commit 9407040c59218 (which indeed fixed bug
      14219, but introduced a major hidden service reachability
      regression detailed in bug 16381). This is a temporary fix since
      we can live with the minor issue in bug 14219 (it just results in
      some load on the network) but the regression of 16381 is too much
      of a setback. First-round fix for bug 16381; bugfix
      on 0.2.6.3-alpha.

  o Major bugfixes (hidden services):
    - Revert commit that made directory authorities assign the HSDir
      flag to relay without a DirPort; this was bad because such relays
      can't handle BEGIN_DIR cells. Fixes bug 15850; bugfix
      on 0.2.6.3-alpha.
    - When cannibalizing a circuit for an introduction point, always
      extend to the chosen exit node (creating a 4 hop circuit).
      Previously Tor would use the current circuit exit node, which
      changed the original choice of introduction point, and could cause
      the hidden service to skip excluded introduction points or
      reconnect to a skipped introduction point. Fixes bug 16260; bugfix
      on 0.1.0.1-rc.

  o Major bugfixes (memory leaks):
    - Fix a memory leak in ed25519 batch signature checking. Fixes bug
      17398; bugfix on 0.2.6.1-alpha.

  o Major bugfixes (open file limit):
    - The open file limit wasn't checked before calling
      tor_accept_socket_nonblocking(), which would make Tor exceed the
      limit. Now, before opening a new socket, Tor validates the open
      file limit just before, and if the max has been reached, return an
      error. Fixes bug 16288; bugfix on 0.1.1.1-alpha.

  o Major bugfixes (security, correctness):
    - Fix an error that could cause us to read 4 bytes before the
      beginning of an openssl string. This bug could be used to cause
      Tor to crash on systems with unusual malloc implementations, or
      systems with unusual hardening installed. Fixes bug 17404; bugfix
      on 0.2.3.6-alpha.

  o Major bugfixes (stability, also in 0.2.6.10):
    - Stop crashing with an assertion failure when parsing certain kinds
      of malformed or truncated microdescriptors. Fixes bug 16400;
      bugfix on 0.2.6.1-alpha. Found by "torkeln"; fix based on a patch
      by "cypherpunks_backup".
    - Stop random client-side assertion failures that could occur when
      connecting to a busy hidden service, or connecting to a hidden
      service while a NEWNYM is in progress. Fixes bug 16013; bugfix
      on 0.1.0.1-rc.

  o Minor features (client, SOCKS):
    - Add GroupWritable and WorldWritable options to unix-socket based
      SocksPort and ControlPort options. These options apply to a single
      socket, and override {Control,Socks}SocketsGroupWritable. Closes
      ticket 15220.
    - Relax the validation done to hostnames in SOCKS5 requests, and
      allow a single trailing '.' to cope with clients that pass FQDNs
      using that syntax to explicitly indicate that the domain name is
      fully-qualified. Fixes bug 16674; bugfix on 0.2.6.2-alpha.
    - Relax the validation of hostnames in SOCKS5 requests, allowing the
      character '_' to appear, in order to cope with domains observed in
      the wild that are serving non-RFC compliant records. Resolves
      ticket 16430.

  o Minor features (client-side privacy):
    - New KeepAliveIsolateSOCKSAuth option to indefinitely extend circuit
      lifespan when IsolateSOCKSAuth and streams with SOCKS
      authentication are attached to the circuit. This allows
      applications like TorBrowser to manage circuit lifetime on their
      own. Implements feature 15482.
    - When logging malformed hostnames from SOCKS5 requests, respect
      SafeLogging configuration. Fixes bug 16891; bugfix on 0.1.1.16-rc.

  o Minor features (clock-jump tolerance):
    - Recover better when our clock jumps back many hours, like might
      happen for Tails or Whonix users who start with a very wrong
      hardware clock, use Tor to discover a more accurate time, and then
      fix their clock. Resolves part of ticket 8766.

  o Minor features (command-line interface):
    - Make --hash-password imply --hush to prevent unnecessary noise.
      Closes ticket 15542. Patch from "cypherpunks".
    - Print a warning whenever we find a relative file path being used
      as torrc option. Resolves issue 14018.

  o Minor features (compilation):
    - Give a warning as early as possible when trying to build with an
      unsupported OpenSSL version. Closes ticket 16901.
    - Use C99 variadic macros when the compiler is not GCC. This avoids
      failing compilations on MSVC, and fixes a log-file-based race
      condition in our old workarounds. Original patch from Gisle Vanem.

  o Minor features (control protocol):
    - Support network-liveness GETINFO key and NETWORK_LIVENESS event in
      the control protocol. Resolves ticket 15358.

  o Minor features (controller):
    - Add DirAuthority lines for default directory authorities to the
      output of the "GETINFO config/defaults" command if not already
      present. Implements ticket 14840.
    - Controllers can now use "GETINFO hs/client/desc/id/..." to
      retrieve items from the client's hidden service descriptor cache.
      Closes ticket 14845.
    - Implement a new controller command "GETINFO status/fresh-relay-
      descs" to fetch a descriptor/extrainfo pair that was generated on
      demand just for the controller's use. Implements ticket 14784.

  o Minor features (directory authorities):
    - Directory authorities no longer vote against the "Fast", "Stable",
      and "HSDir" flags just because they were going to vote against
      "Running": if the consensus turns out to be that the router was
      running, then the authority's vote should count. Patch from Peter
      Retzlaff; closes issue 8712.

  o Minor features (directory authorities, security, also in 0.2.6.9):
    - The HSDir flag given by authorities now requires the Stable flag.
      For the current network, this results in going from 2887 to 2806
      HSDirs. Also, it makes it harder for an attacker to launch a sybil
      attack by raising the effort for a relay to become Stable to
      require at the very least 7 days, while maintaining the 96 hours
      uptime requirement for HSDir. Implements ticket 8243.

  o Minor features (DoS-resistance):
    - Make it harder for attackers to overload hidden services with
      introductions, by blocking multiple introduction requests on the
      same circuit. Resolves ticket 15515.

  o Minor features (geoip):
    - Update geoip and geoip6 to the October 9 2015 Maxmind GeoLite2
      Country database.

  o Minor features (hidden services):
    - Add the new options "HiddenServiceMaxStreams" and
      "HiddenServiceMaxStreamsCloseCircuit" to allow hidden services to
      limit the maximum number of simultaneous streams per circuit, and
      optionally tear down the circuit when the limit is exceeded. Part
      of ticket 16052.
    - Client now uses an introduction point failure cache to know when
      to fetch or keep a descriptor in their cache. Previously, failures
      were recorded implicitly, but not explicitly remembered. Closes
      ticket 16389.
    - Relays need to have the Fast flag to get the HSDir flag. As this
      is being written, we'll go from 2745 HSDirs down to 2342, a ~14%
      drop. This change should make some attacks against the hidden
      service directory system harder. Fixes ticket 15963.
    - Turn on hidden service statistics collection by setting the torrc
      option HiddenServiceStatistics to "1" by default. (This keeps
      track only of the fraction of traffic used by hidden services, and
      the total number of hidden services in existence.) Closes
      ticket 15254.
    - To avoid leaking HS popularity, don't cycle the introduction point
      when we've handled a fixed number of INTRODUCE2 cells but instead
      cycle it when a random number of introductions is reached, thus
      making it more difficult for an attacker to find out the amount of
      clients that have used the introduction point for a specific HS.
      Closes ticket 15745.

  o Minor features (logging):
    - Include the Tor version in all LD_BUG log messages, since people
      tend to cut and paste those into the bugtracker. Implements
      ticket 15026.

  o Minor features (pluggable transports):
    - When launching managed pluggable transports on Linux systems,
      attempt to have the kernel deliver a SIGTERM on tor exit if the
      pluggable transport process is still running. Resolves
      ticket 15471.
    - When launching managed pluggable transports, setup a valid open
      stdin in the child process that can be used to detect if tor has
      terminated. The "TOR_PT_EXIT_ON_STDIN_CLOSE" environment variable
      can be used by implementations to detect this new behavior.
      Resolves ticket 15435.

  o Minor bugfixes (torrc exit policies):
    - In each instance above, usage advice is provided to avoid the
      message. Resolves ticket 16069. Patch by "teor". Fixes part of bug
      16069; bugfix on 0.2.4.7-alpha.
    - In torrc, "accept6 *" and "reject6 *" ExitPolicy lines now only
      produce IPv6 wildcard addresses. Previously they would produce
      both IPv4 and IPv6 wildcard addresses. Patch by "teor". Fixes part
      of bug 16069; bugfix on 0.2.4.7-alpha.
    - When parsing torrc ExitPolicies, we now issue an info-level
      message when expanding an "accept/reject *" line to include both
      IPv4 and IPv6 wildcard addresses. Related to ticket 16069.
    - When parsing torrc ExitPolicies, we now warn for a number of cases
      where the user's intent is likely to differ from Tor's actual
      behavior. These include: using an IPv4 address with an accept6 or
      reject6 line; using "private" on an accept6 or reject6 line; and
      including any ExitPolicy lines after accept *:* or reject *:*.
      Related to ticket 16069.

  o Minor bugfixes (command-line interface):
    - When "--quiet" is provided along with "--validate-config", do not
      write anything to stdout on success. Fixes bug 14994; bugfix
      on 0.2.3.3-alpha.
    - When complaining about bad arguments to "--dump-config", use
      stderr, not stdout.
    - Print usage information for --dump-config when it is used without
      an argument. Also, fix the error message to use different wording
      and add newline at the end. Fixes bug 15541; bugfix
      on 0.2.5.1-alpha.

  o Minor bugfixes (compilation):
    - Fix compilation of sandbox.c with musl-libc. Fixes bug 17347;
      bugfix on 0.2.5.1-alpha. Patch from 'jamestk'.
    - Repair compilation with the most recent (unreleased, alpha)
      vesions of OpenSSL 1.1. Fixes part of ticket 17237.

  o Minor bugfixes (compilation, also in 0.2.6.9):
    - Build with --enable-systemd correctly when libsystemd is
      installed, but systemd is not. Fixes bug 16164; bugfix on
      0.2.6.3-alpha. Patch from Peter Palfrader.

  o Minor bugfixes (configuration, unit tests):
    - Only add the default fallback directories when the DirAuthorities,
      AlternateDirAuthority, and FallbackDir directory config options
      are set to their defaults. The default fallback directory list is
      currently empty, this fix will only change tor's behavior when it
      has default fallback directories. Includes unit tests for
      consider_adding_dir_servers(). Fixes bug 15642; bugfix on
      90f6071d8dc0 in 0.2.4.7-alpha. Patch by "teor".

  o Minor bugfixes (controller):
    - Add the descriptor ID in each HS_DESC control event. It was
      missing, but specified in control-spec.txt. Fixes bug 15881;
      bugfix on 0.2.5.2-alpha.

  o Minor bugfixes (correctness):
    - For correctness, avoid modifying a constant string in
      handle_control_postdescriptor. Fixes bug 15546; bugfix
      on 0.1.1.16-rc.
    - Remove side-effects from tor_assert() calls. This was harmless,
      because we never disable assertions, but it is bad style and
      unnecessary. Fixes bug 15211; bugfix on 0.2.5.5, 0.2.2.36,
      and 0.2.0.10.
    - When calling channel_free_list(), avoid calling smartlist_remove()
      while inside a FOREACH loop. This partially reverts commit
      17356fe7fd96af where the correct SMARTLIST_DEL_CURRENT was
      incorrectly removed. Fixes bug 16924; bugfix on 0.2.4.4-alpha.

  o Minor bugfixes (crypto error-handling, also in 0.2.6.10):
    - Check for failures from crypto_early_init, and refuse to continue.
      A previous typo meant that we could keep going with an
      uninitialized crypto library, and would have OpenSSL initialize
      its own PRNG. Fixes bug 16360; bugfix on 0.2.5.2-alpha, introduced
      when implementing ticket 4900. Patch by "teor".

  o Minor bugfixes (hidden service):
    - Fix an out-of-bounds read when parsing invalid INTRODUCE2 cells on
      a client authorized hidden service. Fixes bug 15823; bugfix
      on 0.2.1.6-alpha.
    - Remove an extraneous newline character from the end of hidden
      service descriptors. Fixes bug 15296; bugfix on 0.2.0.10-alpha.

  o Minor bugfixes (Linux seccomp2 sandbox):
    - Use the sandbox in tor_open_cloexec whether or not O_CLOEXEC is
      defined. Patch by "teor". Fixes bug 16515; bugfix on 0.2.3.1-alpha.
    - Allow bridge authorities to run correctly under the seccomp2
      sandbox. Fixes bug 16964; bugfix on 0.2.5.1-alpha.
    - Add the "hidserv-stats" filename to our sandbox filter for the
      HiddenServiceStatistics option to work properly. Fixes bug 17354;
      bugfix on 0.2.6.2-alpha. Patch from David Goulet.

  o Minor bugfixes (Linux seccomp2 sandbox, also in 0.2.6.10):
    - Allow pipe() and pipe2() syscalls in the seccomp2 sandbox: we need
      these when eventfd2() support is missing. Fixes bug 16363; bugfix
      on 0.2.6.3-alpha. Patch from "teor".

  o Minor bugfixes (Linux seccomp2 sandbox, also in 0.2.6.9):
    - Allow systemd connections to work with the Linux seccomp2 sandbox
      code. Fixes bug 16212; bugfix on 0.2.6.2-alpha. Patch by
      Peter Palfrader.
    - Fix sandboxing to work when running as a relay, by allowing the
      renaming of secret_id_key, and allowing the eventfd2 and futex
      syscalls. Fixes bug 16244; bugfix on 0.2.6.1-alpha. Patch by
      Peter Palfrader.

  o Minor bugfixes (logging):
    - When building Tor under Clang, do not include an extra set of
      parentheses in log messages that include function names. Fixes bug
      15269; bugfix on every released version of Tor when compiled with
      recent enough Clang.

  o Minor bugfixes (network):
    - When attempting to use fallback technique for network interface
      lookup, disregard loopback and multicast addresses since they are
      unsuitable for public communications.

  o Minor bugfixes (open file limit):
    - Fix set_max_file_descriptors() to set by default the max open file
      limit to the current limit when setrlimit() fails. Fixes bug
      16274; bugfix on tor- 0.2.0.10-alpha. Patch by dgoulet.

  o Minor bugfixes (portability):
    - Check correctly for Windows socket errors in the workqueue
      backend. Fixes bug 16741; bugfix on 0.2.6.3-alpha.
    - Try harder to normalize the exit status of the Tor process to the
      standard-provided range. Fixes bug 16975; bugfix on every version
      of Tor ever.
    - Use libexecinfo on FreeBSD to enable backtrace support. Fixes part
      of bug 17151; bugfix on 0.2.5.2-alpha. Patch from Marcin Cieślak.

  o Minor bugfixes (relay):
    - Ensure that worker threads actually exit when a fatal error or
      shutdown is indicated. This fix doesn't currently affect the
      behavior of Tor, because Tor workers never indicates fatal error
      or shutdown except in the unit tests. Fixes bug 16868; bugfix
      on 0.2.6.3-alpha.
    - Fix a rarely-encountered memory leak when failing to initialize
      the thread pool. Fixes bug 16631; bugfix on 0.2.6.3-alpha. Patch
      from "cypherpunks".
    - Unblock threads before releasing the work queue mutex to ensure
      predictable scheduling behavior. Fixes bug 16644; bugfix
      on 0.2.6.3-alpha.

  o Minor bugfixes (security, exit policies):
    - ExitPolicyRejectPrivate now also rejects the relay's published
      IPv6 address (if any), and any publicly routable IPv4 or IPv6
      addresses on any local interfaces. ticket 17027. Patch by "teor".
      Fixes bug 17027; bugfix on 0.2.0.11-alpha.

  o Minor bugfixes (statistics):
    - Disregard the ConnDirectionStatistics torrc options when Tor is
      not a relay since in that mode of operation no sensible data is
      being collected and because Tor might run into measurement hiccups
      when running as a client for some time, then becoming a relay.
      Fixes bug 15604; bugfix on 0.2.2.35.

  o Minor bugfixes (systemd):
    - Tor's systemd unit file no longer contains extraneous spaces.
      These spaces would sometimes confuse tools like deb-systemd-
      helper. Fixes bug 16162; bugfix on 0.2.5.5-alpha.

  o Minor bugfixes (test networks):
    - When self-testing reachability, use ExtendAllowPrivateAddresses to
      determine if local/private addresses imply reachability. The
      previous fix used TestingTorNetwork, which implies
      ExtendAllowPrivateAddresses, but this excluded rare configurations
      where ExtendAllowPrivateAddresses is set but TestingTorNetwork is
      not. Fixes bug 15771; bugfix on 0.2.6.1-alpha. Patch by "teor",
      issue discovered by CJ Ess.

  o Minor bugfixes (tests, also in 0.2.6.9):
    - Fix a crash in the unit tests when built with MSVC2013. Fixes bug
      16030; bugfix on 0.2.6.2-alpha. Patch from "NewEraCracker".

  o Code simplification and refactoring:
    - Change the function that's called when we need to retry all
      downloads so that it only reschedules the downloads to happen
      immediately, rather than launching them all at once itself. This
      further simplifies Tor's callgraph.
    - Define WINVER and _WIN32_WINNT centrally, in orconfig.h, in order
      to ensure they remain consistent and visible everywhere.
    - Move some format-parsing functions out of crypto.c and
      crypto_curve25519.c into crypto_format.c and/or util_format.c.
    - Move the client-only parts of init_keys() into a separate
      function. Closes ticket 16763.
    - Move the hacky fallback code out of get_interface_address6() into
      separate function and get it covered with unit-tests. Resolves
      ticket 14710.
    - Refactor hidden service client-side cache lookup to intelligently
      report its various failure cases, and disentangle failure cases
      involving a lack of introduction points. Closes ticket 14391.
    - Remove some vestigial workarounds for the MSVC6 compiler. We
      haven't supported that in ages.
    - Remove the unused "nulterminate" argument from buf_pullup().
    - Simplify the microdesc_free() implementation so that it no longer
      appears (to code analysis tools) to potentially invoke a huge
      suite of other microdesc functions.
    - Simply the control graph further by deferring the inner body of
      directory_all_unreachable() into a callback. Closes ticket 16762.
    - The link authentication code has been refactored for better
      testability and reliability. It now uses code generated with the
      "trunnel" binary encoding generator, to reduce the risk of bugs
      due to programmer error. Done as part of ticket 12498.
    - Treat the loss of an owning controller as equivalent to a SIGTERM
      signal. This removes a tiny amount of duplicated code, and
      simplifies our callgraph. Closes ticket 16788.
    - Use our own Base64 encoder instead of OpenSSL's, to allow more
      control over the output. Part of ticket 15652.
    - When generating an event to send to the controller, we no longer
      put the event over the network immediately. Instead, we queue
      these events, and use a Libevent callback to deliver them. This
      change simplifies Tor's callgraph by reducing the number of
      functions from which all other Tor functions are reachable. Closes
      ticket 16695.
    - Wrap Windows-only C files inside '#ifdef _WIN32' so that tools
      that try to scan or compile every file on Unix won't decide that
      they are broken.

  o Documentation:
    - Fix capitalization of SOCKS in sample torrc. Closes ticket 15609.
    - Improve the descriptions of statistics-related torrc options in
      the manpage to describe rationale and possible uses cases. Fixes
      issue 15550.
    - Improve the layout and formatting of ./configure --help messages.
      Closes ticket 15024. Patch from "cypherpunks".
    - Include a specific and (hopefully) accurate documentation of the
      torrc file's meta-format in doc/torrc_format.txt. This is mainly
      of interest to people writing programs to parse or generate torrc
      files. This document is not a commitment to long-term
      compatibility; some aspects of the current format are a bit
      ridiculous. Closes ticket 2325.
    - Include the TUNING document in our source tarball. It is referred
      to in the ChangeLog and an error message. Fixes bug 16929; bugfix
      on 0.2.6.1-alpha.
    - Note that HiddenServicePorts can take a unix domain socket. Closes
      ticket 17364.
    - Recommend a 40 GB example AccountingMax in torrc.sample rather
      than a 4 GB max. Closes ticket 16742.
    - Standardize on the term "server descriptor" in the manual page.
      Previously, we had used "router descriptor", "server descriptor",
      and "relay descriptor" interchangeably. Part of ticket 14987.
    - Advise users on how to configure separate IPv4 and IPv6 exit
      policies in the manpage and sample torrcs. Related to ticket 16069.
    - Fix an error in the manual page and comments for
      TestingDirAuthVoteHSDir[IsStrict], which suggested that a HSDir
      required "ORPort connectivity". While this is true, it is in no
      way unique to the HSDir flag. Of all the flags, only HSDirs need a
      DirPort configured in order for the authorities to assign that
      particular flag. Patch by "teor". Fixed as part of 14882; bugfix
      on 0.2.6.3-alpha.
    - Fix the usage message of tor-resolve(1) so that it no longer lists
      the removed -F option. Fixes bug 16913; bugfix on 0.2.2.28-beta.

  o Removed code:
    - Remove `USE_OPENSSL_BASE64` and the corresponding fallback code
      and always use the internal Base64 decoder. The internal decoder
      has been part of tor since 0.2.0.10-alpha, and no one should
      be using the OpenSSL one. Part of ticket 15652.
    - Remove the 'tor_strclear()' function; use memwipe() instead.
      Closes ticket 14922.
    - Remove the code that would try to aggressively flush controller
      connections while writing to them. This code was introduced in
      0.1.2.7-alpha, in order to keep output buffers from exceeding
      their limits. But there is no longer a maximum output buffer size,
      and flushing data in this way caused some undesirable recursions
      in our call graph. Closes ticket 16480.
    - The internal pure-C tor-fw-helper tool is now removed from the Tor
      distribution, in favor of the pure-Go clone available from
      https://gitweb.torproject.org/tor-fw-helper.git/ . The libraries
      used by the C tor-fw-helper are not, in our opinion, very
      confidence- inspiring in their secure-programming techniques.
      Closes ticket 13338.

  o Removed features:
    - Remove the (seldom-used) DynamicDHGroups feature. For anti-
      fingerprinting we now recommend pluggable transports; for forward-
      secrecy in TLS, we now use the P-256 group. Closes ticket 13736.
    - Remove the HidServDirectoryV2 option. Now all relays offer to
      store hidden service descriptors. Related to 16543.
    - Remove the VoteOnHidServDirectoriesV2 option, since all
      authorities have long set it to 1. Closes ticket 16543.
    - Remove the undocumented "--digests" command-line option. It
      complicated our build process, caused subtle build issues on
      multiple platforms, and is now redundant since we started
      including git version identifiers. Closes ticket 14742.
    - Tor no longer contains checks for ancient directory cache versions
      that didn't know about microdescriptors.
    - Tor no longer contains workarounds for stat files generated by
      super-old versions of Tor that didn't choose guards sensibly.

  o Testing:
    - The test-network.sh script now supports performance testing.
      Requires corresponding chutney performance testing changes. Patch
      by "teor". Closes ticket 14175.
    - Add a new set of callgraph analysis scripts that use clang to
      produce a list of which Tor functions are reachable from which
      other Tor functions. We're planning to use these to help simplify
      our code structure by identifying illogical dependencies.
    - Add new 'test-full' and 'test-full-online' targets to run all
      tests, including integration tests with stem and chutney.
    - Autodetect CHUTNEY_PATH if the chutney and Tor sources are side-
      by-side in the same parent directory. Closes ticket 16903. Patch
      by "teor".
    - Document use of coverity, clang static analyzer, and clang dynamic
      undefined behavior and address sanitizers in doc/HACKING. Include
      detailed usage instructions in the blacklist. Patch by "teor".
      Closes ticket 15817.
    - Make "bridges+hs" the default test network. This tests almost all
      tor functionality during make test-network, while allowing tests
      to succeed on non-IPv6 systems. Requires chutney commit 396da92 in
      test-network-bridges-hs. Closes tickets 16945 (tor) and 16946
      (chutney). Patches by "teor".
    - Make the test-workqueue test work on Windows by initializing the
      network before we begin.
    - New make target (make test-network-all) to run multiple applicable
      chutney test cases. Patch from Teor; closes 16953.
    - Now that OpenSSL has its own scrypt implementation, add an unit
      test that checks for interoperability between libscrypt_scrypt()
      and OpenSSL's EVP_PBE_scrypt() so that we could not use libscrypt
      and rely on EVP_PBE_scrypt() whenever possible. Resolves
      ticket 16189.
    - The link authentication protocol code now has extensive tests.
    - The relay descriptor signature testing code now has
      extensive tests.
    - The test_workqueue program now runs faster, and is enabled by
      default as a part of "make check".
    - Unit test dns_resolve(), dns_clip_ttl() and dns_get_expiry_ttl()
      functions in dns.c. Implements a portion of ticket 16831.
    - Use environment variables rather than autoconf substitutions to
      send variables from the build system to the test scripts. This
      change should be easier to maintain, and cause 'make distcheck' to
      work better than before. Fixes bug 17148.
    - When building Tor with testing coverage enabled, run Chutney tests
      (if any) using the 'tor-cov' coverage binary.
    - When running test-network or test-stem, check for the absence of
      stem/chutney before doing any build operations.
    - Add a test to verify that the compiler does not eliminate our
      memwipe() implementation. Closes ticket 15377.
    - Add make rule `check-changes` to verify the format of changes
      files. Closes ticket 15180.
    - Add unit tests for control_event_is_interesting(). Add a compile-
      time check that the number of events doesn't exceed the capacity
      of control_event_t.event_mask. Closes ticket 15431, checks for
      bugs similar to 13085. Patch by "teor".
    - Command-line argument tests moved to Stem. Resolves ticket 14806.
    - Integrate the ntor, backtrace, and zero-length keys tests into the
      automake test suite. Closes ticket 15344.
    - Remove assertions during builds to determine Tor's test coverage.
      We don't want to trigger these even in assertions, so including
      them artificially makes our branch coverage look worse than it is.
      This patch provides the new test-stem-full and coverage-html-full
      configure options. Implements ticket 15400.
    - New TestingDirAuthVote{Exit,Guard,HSDir}IsStrict flags to
      explicitly manage consensus flags in testing networks. Patch by
      "robgjansen", modified by "teor". Implements part of ticket 14882.
    - Check for matching value in server response in ntor_ref.py. Fixes
      bug 15591; bugfix on 0.2.4.8-alpha. Reported and fixed
      by "joelanders".
    - Set the severity correctly when testing
      get_interface_addresses_ifaddrs() and
      get_interface_addresses_win32(), so that the tests fail gracefully
      instead of triggering an assertion. Fixes bug 15759; bugfix on
      0.2.6.3-alpha. Reported by Nicolas Derive.

Changes in version 0.2.6.10 - 2015-07-12
  Tor version 0.2.6.10 fixes some significant stability and hidden
  service client bugs, bulletproofs the cryptography init process, and
  fixes a bug when using the sandbox code with some older versions of
  Linux. Everyone running an older version, especially an older version
  of 0.2.6, should upgrade.

  o Major bugfixes (hidden service clients, stability):
    - Stop refusing to store updated hidden service descriptors on a
      client. This reverts commit 9407040c59218 (which indeed fixed bug
      14219, but introduced a major hidden service reachability
      regression detailed in bug 16381). This is a temporary fix since
      we can live with the minor issue in bug 14219 (it just results in
      some load on the network) but the regression of 16381 is too much
      of a setback. First-round fix for bug 16381; bugfix
      on 0.2.6.3-alpha.

  o Major bugfixes (stability):
    - Stop crashing with an assertion failure when parsing certain kinds
      of malformed or truncated microdescriptors. Fixes bug 16400;
      bugfix on 0.2.6.1-alpha. Found by "torkeln"; fix based on a patch
      by "cypherpunks_backup".
    - Stop random client-side assertion failures that could occur when
      connecting to a busy hidden service, or connecting to a hidden
      service while a NEWNYM is in progress. Fixes bug 16013; bugfix
      on 0.1.0.1-rc.

  o Minor features (geoip):
    - Update geoip to the June 3 2015 Maxmind GeoLite2 Country database.
    - Update geoip6 to the June 3 2015 Maxmind GeoLite2 Country database.

  o Minor bugfixes (crypto error-handling):
    - Check for failures from crypto_early_init, and refuse to continue.
      A previous typo meant that we could keep going with an
      uninitialized crypto library, and would have OpenSSL initialize
      its own PRNG. Fixes bug 16360; bugfix on 0.2.5.2-alpha, introduced
      when implementing ticket 4900. Patch by "teor".

  o Minor bugfixes (Linux seccomp2 sandbox):
    - Allow pipe() and pipe2() syscalls in the seccomp2 sandbox: we need
      these when eventfd2() support is missing. Fixes bug 16363; bugfix
      on 0.2.6.3-alpha. Patch from "teor".


Changes in version 0.2.6.9 - 2015-06-11
  Tor 0.2.6.9 fixes a regression in the circuit isolation code, increases the
  requirements for receiving an HSDir flag, and addresses some other small
  bugs in the systemd and sandbox code. Clients using circuit isolation
  should upgrade; all directory authorities should upgrade.

  o Major bugfixes (client-side privacy):
    - Properly separate out each SOCKSPort when applying stream
      isolation. The error occurred because each port's session group was
      being overwritten by a default value when the listener connection
      was initialized. Fixes bug 16247; bugfix on 0.2.6.3-alpha. Patch
      by "jojelino".

  o Minor feature (directory authorities, security):
    - The HSDir flag given by authorities now requires the Stable flag.
      For the current network, this results in going from 2887 to 2806
      HSDirs. Also, it makes it harder for an attacker to launch a sybil
      attack by raising the effort for a relay to become Stable which
      takes at the very least 7 days to do so and by keeping the 96
      hours uptime requirement for HSDir. Implements ticket 8243.

  o Minor bugfixes (compilation):
    - Build with --enable-systemd correctly when libsystemd is
      installed, but systemd is not. Fixes bug 16164; bugfix on
      0.2.6.3-alpha. Patch from Peter Palfrader.

  o Minor bugfixes (Linux seccomp2 sandbox):
    - Fix sandboxing to work when running as a relaymby renaming of
      secret_id_key, and allowing the eventfd2 and futex syscalls. Fixes
      bug 16244; bugfix on 0.2.6.1-alpha. Patch by Peter Palfrader.
    - Allow systemd connections to work with the Linux seccomp2 sandbox
      code. Fixes bug 16212; bugfix on 0.2.6.2-alpha. Patch by
      Peter Palfrader.

  o Minor bugfixes (tests):
    - Fix a crash in the unit tests when built with MSVC2013. Fixes bug
      16030; bugfix on 0.2.6.2-alpha. Patch from "NewEraCracker".


Changes in version 0.2.6.8 - 2015-05-21
  Tor 0.2.6.8 fixes a bit of dodgy code in parsing INTRODUCE2 cells, and
  fixes an authority-side bug in assigning the HSDir flag. All directory
  authorities should upgrade.

  o Major bugfixes (hidden services, backport from 0.2.7.1-alpha):
    - Revert commit that made directory authorities assign the HSDir
      flag to relay without a DirPort; this was bad because such relays
      can't handle BEGIN_DIR cells. Fixes bug 15850; bugfix
      on 0.2.6.3-alpha.

  o Minor bugfixes (hidden service, backport from 0.2.7.1-alpha):
    - Fix an out-of-bounds read when parsing invalid INTRODUCE2 cells on
      a client authorized hidden service. Fixes bug 15823; bugfix
      on 0.2.1.6-alpha.

  o Minor features (geoip):
    - Update geoip to the April 8 2015 Maxmind GeoLite2 Country database.
    - Update geoip6 to the April 8 2015 Maxmind GeoLite2
      Country database.


Changes in version 0.2.6.7 - 2015-04-06
  Tor 0.2.6.7 fixes two security issues that could be used by an
  attacker to crash hidden services, or crash clients visiting hidden
  services. Hidden services should upgrade as soon as possible; clients
  should upgrade whenever packages become available.

  This release also contains two simple improvements to make hidden
  services a bit less vulnerable to denial-of-service attacks.

  o Major bugfixes (security, hidden service):
    - Fix an issue that would allow a malicious client to trigger an
      assertion failure and halt a hidden service. Fixes bug 15600;
      bugfix on 0.2.1.6-alpha. Reported by "disgleirio".
    - Fix a bug that could cause a client to crash with an assertion
      failure when parsing a malformed hidden service descriptor. Fixes
      bug 15601; bugfix on 0.2.1.5-alpha. Found by "DonnchaC".

  o Minor features (DoS-resistance, hidden service):
    - Introduction points no longer allow multiple INTRODUCE1 cells to
      arrive on the same circuit. This should make it more expensive for
      attackers to overwhelm hidden services with introductions.
      Resolves ticket 15515.
    - Decrease the amount of reattempts that a hidden service performs
      when its rendezvous circuits fail. This reduces the computational
      cost for running a hidden service under heavy load. Resolves
      ticket 11447.


Changes in version 0.2.5.12 - 2015-04-06
  Tor 0.2.5.12 backports two fixes from 0.2.6.7 for security issues that
  could be used by an attacker to crash hidden services, or crash clients
  visiting hidden services. Hidden services should upgrade as soon as
  possible; clients should upgrade whenever packages become available.

  This release also backports a simple improvement to make hidden
  services a bit less vulnerable to denial-of-service attacks.

  o Major bugfixes (security, hidden service):
    - Fix an issue that would allow a malicious client to trigger an
      assertion failure and halt a hidden service. Fixes bug 15600;
      bugfix on 0.2.1.6-alpha. Reported by "disgleirio".
    - Fix a bug that could cause a client to crash with an assertion
      failure when parsing a malformed hidden service descriptor. Fixes
      bug 15601; bugfix on 0.2.1.5-alpha. Found by "DonnchaC".

  o Minor features (DoS-resistance, hidden service):
    - Introduction points no longer allow multiple INTRODUCE1 cells to
      arrive on the same circuit. This should make it more expensive for
      attackers to overwhelm hidden services with introductions.
      Resolves ticket 15515.


Changes in version 0.2.4.27 - 2015-04-06
  Tor 0.2.4.27 backports two fixes from 0.2.6.7 for security issues that
  could be used by an attacker to crash hidden services, or crash clients
  visiting hidden services. Hidden services should upgrade as soon as
  possible; clients should upgrade whenever packages become available.

  This release also backports a simple improvement to make hidden
  services a bit less vulnerable to denial-of-service attacks.

  o Major bugfixes (security, hidden service):
    - Fix an issue that would allow a malicious client to trigger an
      assertion failure and halt a hidden service. Fixes bug 15600;
      bugfix on 0.2.1.6-alpha. Reported by "disgleirio".
    - Fix a bug that could cause a client to crash with an assertion
      failure when parsing a malformed hidden service descriptor. Fixes
      bug 15601; bugfix on 0.2.1.5-alpha. Found by "DonnchaC".

  o Minor features (DoS-resistance, hidden service):
    - Introduction points no longer allow multiple INTRODUCE1 cells to
      arrive on the same circuit. This should make it more expensive for
      attackers to overwhelm hidden services with introductions.
      Resolves ticket 15515.


Changes in version 0.2.6.6 - 2015-03-24
  Tor 0.2.6.6 is the first stable release in the 0.2.6 series.

  It adds numerous safety, security, correctness, and performance
  improvements. Client programs can be configured to use more kinds of
  sockets, AutomapHosts works better, the multithreading backend is
  improved, cell transmission is refactored, test coverage is much
  higher, more denial-of-service attacks are handled, guard selection is
  improved to handle long-term guards better, pluggable transports
  should work a bit better, and some annoying hidden service performance
  bugs should be addressed.

  o New compiler and system requirements:
    - Tor 0.2.6.x requires that your compiler support more of the C99
      language standard than before. The 'configure' script now detects
      whether your compiler supports C99 mid-block declarations and
      designated initializers. If it does not, Tor will not compile.

      We may revisit this requirement if it turns out that a significant
      number of people need to build Tor with compilers that don't
      bother implementing a 15-year-old standard. Closes ticket 13233.
    - Tor no longer supports systems without threading support. When we
      began working on Tor, there were several systems that didn't have
      threads, or where the thread support wasn't able to run the
      threads of a single process on multiple CPUs. That no longer
      holds: every system where Tor needs to run well now has threading
      support. Resolves ticket 12439.

  o Deprecated versions and removed support:
    - Tor relays older than 0.2.4.18-rc are no longer allowed to
      advertise themselves on the network. Closes ticket 13555.
    - Tor clients no longer support connecting to hidden services
      running on Tor 0.2.2.x and earlier; the Support022HiddenServices
      option has been removed. (There shouldn't be any hidden services
      running these versions on the network.) Closes ticket 7803.

  o Directory authority changes:
    - The directory authority Faravahar has a new IP address. This
      closes ticket 14487.
    - Remove turtles as a directory authority.
    - Add longclaw as a new (v3) directory authority. This implements
      ticket 13296. This keeps the directory authority count at 9.

  o Major features (bridges):
    - Expose the outgoing upstream HTTP/SOCKS proxy to pluggable
      transports if they are configured via the "TOR_PT_PROXY"
      environment variable. Implements proposal 232. Resolves
      ticket 8402.

  o Major features (changed defaults):
    - Prevent relay operators from unintentionally running exits: When a
      relay is configured as an exit node, we now warn the user unless
      the "ExitRelay" option is set to 1. We warn even more loudly if
      the relay is configured with the default exit policy, since this
      can indicate accidental misconfiguration. Setting "ExitRelay 0"
      stops Tor from running as an exit relay. Closes ticket 10067.

  o Major features (client performance, hidden services):
    - Allow clients to use optimistic data when connecting to a hidden
      service, which should remove a round-trip from hidden service
      initialization. See proposal 181 for details. Implements
      ticket 13211.

  o Major features (directory system):
    - Upon receiving an unparseable directory object, if its digest
      matches what we expected, then don't try to download it again.
      Previously, when we got a descriptor we didn't like, we would keep
      trying to download it over and over. Closes ticket 11243.
    - When downloading server- or microdescriptors from a directory
      server, we no longer launch multiple simultaneous requests to the
      same server. This reduces load on the directory servers,
      especially when directory guards are in use. Closes ticket 9969.
    - When downloading server- or microdescriptors over a tunneled
      connection, do not limit the length of our requests to what the
      Squid proxy is willing to handle. Part of ticket 9969.
    - Authorities can now vote on the correct digests and latest
      versions for different software packages. This allows packages
      that include Tor to use the Tor authority system as a way to get
      notified of updates and their correct digests. Implements proposal
      227. Closes ticket 10395.

  o Major features (guards):
    - Introduce the Guardfraction feature to improves load balancing on
      guard nodes. Specifically, it aims to reduce the traffic gap that
      guard nodes experience when they first get the Guard flag. This is
      a required step if we want to increase the guard lifetime to 9
      months or greater.  Closes ticket 9321.

  o Major features (hidden services):
    - Make HS port scanning more difficult by immediately closing the
      circuit when a user attempts to connect to a nonexistent port.
      Closes ticket 13667.
    - Add a HiddenServiceStatistics option that allows Tor relays to
      gather and publish statistics about the overall size and volume of
      hidden service usage. Specifically, when this option is turned on,
      an HSDir will publish an approximate number of hidden services
      that have published descriptors to it the past 24 hours. Also, if
      a relay has acted as a hidden service rendezvous point, it will
      publish the approximate amount of rendezvous cells it has relayed
      the past 24 hours. The statistics themselves are obfuscated so
      that the exact values cannot be derived. For more details see
      proposal 238, "Better hidden service stats from Tor relays". This
      feature is currently disabled by default. Implements feature 13192.

  o Major features (performance):
    - Make the CPU worker implementation more efficient by avoiding the
      kernel and lengthening pipelines. The original implementation used
      sockets to transfer data from the main thread to the workers, and
      didn't allow any thread to be assigned more than a single piece of
      work at once. The new implementation avoids communications
      overhead by making requests in shared memory, avoiding kernel IO
      where possible, and keeping more requests in flight at once.
      Implements ticket 9682.

  o Major features (relay):
    - Raise the minimum acceptable configured bandwidth rate for bridges
      to 50 KiB/sec and for relays to 75 KiB/sec. (The old values were
      20 KiB/sec.) Closes ticket 13822.
    - Complete revision of the code that relays use to decide which cell
      to send next. Formerly, we selected the best circuit to write on
      each channel, but we didn't select among channels in any
      sophisticated way. Now, we choose the best circuits globally from
      among those whose channels are ready to deliver traffic.

      This patch implements a new inter-cmux comparison API, a global
      high/low watermark mechanism and a global scheduler loop for
      transmission prioritization across all channels as well as among
      circuits on one channel. This schedule is currently tuned to
      (tolerantly) avoid making changes in network performance, but it
      should form the basis for major circuit performance increases in
      the future. Code by Andrea; tuning by Rob Jansen; implements
      ticket 9262.

  o Major features (sample torrc):
    - Add a new, infrequently-changed "torrc.minimal". This file is
      similar to torrc.sample, but it will change as infrequently as
      possible, for the benefit of users whose systems prompt them for
      intervention whenever a default configuration file is changed.
      Making this change allows us to update torrc.sample to be a more
      generally useful "sample torrc".

  o Major features (security, unix domain sockets):
    - Allow SocksPort to be an AF_UNIX Unix Domain Socket. Now high risk
      applications can reach Tor without having to create AF_INET or
      AF_INET6 sockets, meaning they can completely disable their
      ability to make non-Tor network connections. To create a socket of
      this type, use "SocksPort unix:/path/to/socket". Implements
      ticket 12585.
    - Support mapping hidden service virtual ports to AF_UNIX sockets.
      The syntax is "HiddenServicePort 80 unix:/path/to/socket".
      Implements ticket 11485.

  o Major bugfixes (client, automap):
    - Repair automapping with IPv6 addresses. This automapping should
      have worked previously, but one piece of debugging code that we
      inserted to detect a regression actually caused the regression to
      manifest itself again. Fixes bug 13811 and bug 12831; bugfix on
      0.2.4.7-alpha. Diagnosed and fixed by Francisco Blas
      Izquierdo Riera.

  o Major bugfixes (crash, OSX, security):
    - Fix a remote denial-of-service opportunity caused by a bug in
      OSX's _strlcat_chk() function. Fixes bug 15205; bug first appeared
      in OSX 10.9.

  o Major bugfixes (directory authorities):
    - Do not assign the HSDir flag to relays if they are not Valid, or
      currently hibernating. Fixes 12573; bugfix on 0.2.0.10-alpha.

  o Major bugfixes (directory bandwidth performance):
    - Don't flush the zlib buffer aggressively when compressing
      directory information for clients. This should save about 7% of
      the bandwidth currently used for compressed descriptors and
      microdescriptors. Fixes bug 11787; bugfix on 0.1.1.23.

  o Major bugfixes (exit node stability):
    - Fix an assertion failure that could occur under high DNS load.
      Fixes bug 14129; bugfix on Tor 0.0.7rc1. Found by "jowr";
      diagnosed and fixed by "cypherpunks".

  o Major bugfixes (FreeBSD IPFW transparent proxy):
    - Fix address detection with FreeBSD transparent proxies, when
      "TransProxyType ipfw" is in use. Fixes bug 15064; bugfix
      on 0.2.5.4-alpha.

  o Major bugfixes (hidden services):
    - When closing an introduction circuit that was opened in parallel
      with others, don't mark the introduction point as unreachable.
      Previously, the first successful connection to an introduction
      point would make the other introduction points get marked as
      having timed out. Fixes bug 13698; bugfix on 0.0.6rc2.

  o Major bugfixes (Linux seccomp2 sandbox):
    - Upon receiving sighup with the seccomp2 sandbox enabled, do not
      crash during attempts to call wait4. Fixes bug 15088; bugfix on
      0.2.5.1-alpha. Patch from "sanic".

  o Major bugfixes (mixed relay-client operation):
    - When running as a relay and client at the same time (not
      recommended), if we decide not to use a new guard because we want
      to retry older guards, only close the locally-originating circuits
      passing through that guard. Previously we would close all the
      circuits through that guard. Fixes bug 9819; bugfix on
      0.2.1.1-alpha. Reported by "skruffy".

  o Major bugfixes (pluggable transports):
    - Initialize the extended OR Port authentication cookie before
      launching pluggable transports. This prevents a race condition
      that occured when server-side pluggable transports would cache the
      authentication cookie before it has been (re)generated. Fixes bug
      15240; bugfix on 0.2.5.1-alpha.

  o Major bugfixes (relay, stability, possible security):
    - Fix a bug that could lead to a relay crashing with an assertion
      failure if a buffer of exactly the wrong layout is passed to
      buf_pullup() at exactly the wrong time. Fixes bug 15083; bugfix on
      0.2.0.10-alpha. Patch from "cypherpunks".
    - Do not assert if the 'data' pointer on a buffer is advanced to the
      very end of the buffer; log a BUG message instead. Only assert if
      it is past that point. Fixes bug 15083; bugfix on 0.2.0.10-alpha.

  o Minor features (build):
    - New --disable-system-torrc compile-time option to prevent Tor from
      looking for the system-wide torrc or torrc-defaults files.
      Resolves ticket 13037.

  o Minor features (client):
    - Clients are now willing to send optimistic data (before they
      receive a 'connected' cell) to relays of any version. (Relays
      without support for optimistic data are no longer supported on the
      Tor network.) Resolves ticket 13153.

  o Minor features (client):
    - Validate hostnames in SOCKS5 requests more strictly. If SafeSocks
      is enabled, reject requests with IP addresses as hostnames.
      Resolves ticket 13315.

  o Minor features (controller):
    - Add a "SIGNAL HEARTBEAT" controller command that tells Tor to
      write an unscheduled heartbeat message to the log. Implements
      feature 9503.
    - Include SOCKS_USERNAME and SOCKS_PASSWORD values in controller
      events so controllers can observe circuit isolation inputs. Closes
      ticket 8405.
    - ControlPort now supports the unix:/path/to/socket syntax as an
      alternative to the ControlSocket option, for consistency with
      SocksPort and HiddenServicePort. Closes ticket 14451.
    - New "GETINFO bw-event-cache" to get information about recent
      bandwidth events. Closes ticket 14128. Useful for controllers to
      get recent bandwidth history after the fix for ticket 13988.
    - Messages about problems in the bootstrap process now include
      information about the server we were trying to connect to when we
      noticed the problem. Closes ticket 15006.

  o Minor features (Denial of service resistance):
    - Count the total number of bytes used storing hidden service
      descriptors against the value of MaxMemInQueues. If we're low on
      memory, and more than 20% of our memory is used holding hidden
      service descriptors, free them until no more than 10% of our
      memory holds hidden service descriptors. Free the least recently
      fetched descriptors first. Resolves ticket 13806.
    - When we have recently been under memory pressure (over 3/4 of
      MaxMemInQueues is allocated), then allocate smaller zlib objects
      for small requests. Closes ticket 11791.

  o Minor features (directory authorities):
    - Don't list relays with a bandwidth estimate of 0 in the consensus.
      Implements a feature proposed during discussion of bug 13000.
    - In tor-gencert, report an error if the user provides the same
      argument more than once.
    - If a directory authority can't find a best consensus method in the
      votes that it holds, it now falls back to its favorite consensus
      method. Previously, it fell back to method 1. Neither of these is
      likely to get enough signatures, but "fall back to favorite"
      doesn't require us to maintain support an obsolete consensus
      method. Implements part of proposal 215.

  o Minor features (geoip):
    - Update geoip to the March 3 2015 Maxmind GeoLite2 Country database.
    - Update geoip6 to the March 3 2015 Maxmind GeoLite2
      Country database.

  o Minor features (guard nodes):
    - Reduce the time delay before saving guard status to disk from 10
      minutes to 30 seconds (or from one hour to 10 minutes if
      AvoidDiskWrites is set). Closes ticket 12485.

  o Minor features (heartbeat):
    - On relays, report how many connections we negotiated using each
      version of the Tor link protocols. This information will let us
      know if removing support for very old versions of the Tor
      protocols is harming the network. Closes ticket 15212.

  o Minor features (hidden service):
    - Make Sybil attacks against hidden services harder by changing the
      minimum time required to get the HSDir flag from 25 hours up to 96
      hours. Addresses ticket 14149.
    - New option "HiddenServiceAllowUnknownPorts" to allow hidden
      services to disable the anti-scanning feature introduced in
      0.2.6.2-alpha. With this option not set, a connection to an
      unlisted port closes the circuit. With this option set, only a
      RELAY_DONE cell is sent. Closes ticket 14084.
    - When re-enabling the network, don't try to build introduction
      circuits until we have successfully built a circuit. This makes
      hidden services come up faster when the network is re-enabled.
      Patch from "akwizgran". Closes ticket 13447.
    - When we fail to retrieve a hidden service descriptor, send the
      controller an "HS_DESC FAILED" controller event. Implements
      feature 13212.
    - New HiddenServiceDirGroupReadable option to cause hidden service
      directories and hostname files to be created group-readable. Patch
      from "anon", David Stainton, and "meejah". Closes ticket 11291.

  o Minor features (interface):
    - Implement "-f -" command-line option to read torrc configuration
      from standard input, if you don't want to store the torrc file in
      the file system. Implements feature 13865.

  o Minor features (logging):
    - Add a count of unique clients to the bridge heartbeat message.
      Resolves ticket 6852.
    - Suppress "router info incompatible with extra info" message when
      reading extrainfo documents from cache. (This message got loud
      around when we closed bug 9812 in 0.2.6.2-alpha.) Closes
      ticket 13762.
    - Elevate hidden service authorized-client message from DEBUG to
      INFO. Closes ticket 14015.
    - On Unix-like systems, you can now use named pipes as the target of
      the Log option, and other options that try to append to files.
      Closes ticket 12061. Patch from "carlo von lynX".
    - When opening a log file at startup, send it every log message that
      we generated between startup and opening it. Previously, log
      messages that were generated before opening the log file were only
      logged to stdout. Closes ticket 6938.
    - Add a TruncateLogFile option to overwrite logs instead of
      appending to them. Closes ticket 5583.
    - Quiet some log messages in the heartbeat and at startup. Closes
      ticket 14950.

  o Minor features (portability, Solaris):
    - Threads are no longer disabled by default on Solaris; we believe
      that the versions of Solaris with broken threading support are all
      obsolete by now. Resolves ticket 9495.

  o Minor features (relay):
    - Re-check our address after we detect a changed IP address from
      getsockname(). This ensures that the controller command "GETINFO
      address" will report the correct value. Resolves ticket 11582.
      Patch from "ra".
    - A new AccountingRule option lets Relays set whether they'd like
      AccountingMax to be applied separately to inbound and outbound
      traffic, or applied to the sum of inbound and outbound traffic.
      Resolves ticket 961. Patch by "chobe".
    - When identity keypair is generated for first time, log a
      congratulatory message that links to the new relay lifecycle
      document. Implements feature 10427.

  o Minor features (security, memory wiping):
    - Ensure we securely wipe keys from memory after
      crypto_digest_get_digest and init_curve25519_keypair_from_file
      have finished using them. Resolves ticket 13477.

  o Minor features (security, out-of-memory handling):
    - When handling an out-of-memory condition, allocate less memory for
      temporary data structures. Fixes issue 10115.
    - When handling an out-of-memory condition, consider more types of
      buffers, including those on directory connections, and zlib
      buffers. Resolves ticket 11792.

  o Minor features (stability):
    - Add assertions in our hash-table iteration code to check for
      corrupted values that could cause infinite loops. Closes
      ticket 11737.

  o Minor features (systemd):
    - Various improvements and modernizations in systemd hardening
      support. Closes ticket 13805. Patch from Craig Andrews.
    - Where supported, when running with systemd, report successful
      startup to systemd. Part of ticket 11016. Patch by Michael Scherer.
    - When running with systemd, support systemd watchdog messages. Part
      of ticket 11016. Patch by Michael Scherer.

  o Minor features (testing networks):
    - Add the TestingDirAuthVoteExit option, which lists nodes to assign
      the "Exit" flag regardless of their uptime, bandwidth, or exit
      policy. TestingTorNetwork must be set for this option to have any
      effect. Previously, authorities would take up to 35 minutes to
      give nodes the Exit flag in a test network. Partially implements
      ticket 13161.
    - Drop the minimum RendPostPeriod on a testing network to 5 seconds,
      and the default on a testing network to 2 minutes. Drop the
      MIN_REND_INITIAL_POST_DELAY on a testing network to 5 seconds, but
      keep the default on a testing network at 30 seconds. This reduces
      HS bootstrap time to around 25 seconds. Also, change the default
      time in test-network.sh to match. Closes ticket 13401. Patch
      by "teor".
    - Create TestingDirAuthVoteHSDir to correspond to
      TestingDirAuthVoteExit/Guard. Ensures that authorities vote the
      HSDir flag for the listed relays regardless of uptime or ORPort
      connectivity. Respects the value of VoteOnHidServDirectoriesV2.
      Partial implementation for ticket 14067. Patch by "teor".

  o Minor features (tor2web mode):
    - Introduce the config option Tor2webRendezvousPoints, which allows
      clients in Tor2webMode to select a specific Rendezvous Point to be
      used in HS circuits. This might allow better performance for
      Tor2Web nodes. Implements ticket 12844.

  o Minor features (transparent proxy):
    - Update the transparent proxy option checks to allow for both ipfw
      and pf on OS X. Closes ticket 14002.
    - Use the correct option when using IPv6 with transparent proxy
      support on Linux. Resolves 13808. Patch by Francisco Blas
      Izquierdo Riera.

  o Minor features (validation):
    - Check all date/time values passed to tor_timegm and
      parse_rfc1123_time for validity, taking leap years into account.
      Improves HTTP header validation. Implemented with bug 13476.
    - In correct_tm(), limit the range of values returned by system
      localtime(_r) and gmtime(_r) to be between the years 1 and 8099.
      This means we don't have to deal with negative or too large dates,
      even if a clock is wrong. Otherwise we might fail to read a file
      written by us which includes such a date. Fixes bug 13476.
    - Stop allowing invalid address patterns like "*/24" that contain
      both a wildcard address and a bit prefix length. This affects all
      our address-range parsing code. Fixes bug 7484; bugfix
      on 0.0.2pre14.

  o Minor bugfixes (bridge clients):
    - When configured to use a bridge without an identity digest (not
      recommended), avoid launching an extra channel to it when
      bootstrapping. Fixes bug 7733; bugfix on 0.2.4.4-alpha.

  o Minor bugfixes (bridges):
    - When DisableNetwork is set, do not launch pluggable transport
      plugins, and if any are running, terminate them. Fixes bug 13213;
      bugfix on 0.2.3.6-alpha.

  o Minor bugfixes (C correctness):
    - Fix several instances of possible integer overflow/underflow/NaN.
      Fixes bug 13104; bugfix on 0.2.3.1-alpha and later. Patches
      from "teor".
    - In circuit_build_times_calculate_timeout() in circuitstats.c,
      avoid dividing by zero in the pareto calculations. This traps
      under clang's "undefined-trap" sanitizer. Fixes bug 13290; bugfix
      on 0.2.2.2-alpha.
    - Fix an integer overflow in format_time_interval(). Fixes bug
      13393; bugfix on 0.2.0.10-alpha.
    - Set the correct day of year value when the system's localtime(_r)
      or gmtime(_r) functions fail to set struct tm. Not externally
      visible. Fixes bug 13476; bugfix on 0.0.2pre14.
    - Avoid unlikely signed integer overflow in tor_timegm on systems
      with 32-bit time_t. Fixes bug 13476; bugfix on 0.0.2pre14.

  o Minor bugfixes (certificate handling):
    - If an authority operator accidentally makes a signing certificate
      with a future publication time, do not discard its real signing
      certificates. Fixes bug 11457; bugfix on 0.2.0.3-alpha.
    - Remove any old authority certificates that have been superseded
      for at least two days. Previously, we would keep superseded
      certificates until they expired, if they were published close in
      time to the certificate that superseded them. Fixes bug 11454;
      bugfix on 0.2.1.8-alpha.

  o Minor bugfixes (client):
    - Fix smartlist_choose_node_by_bandwidth() so that relays with the
      BadExit flag are not considered worthy candidates. Fixes bug
      13066; bugfix on 0.1.2.3-alpha.
    - Use the consensus schedule for downloading consensuses, and not
      the generic schedule. Fixes bug 11679; bugfix on 0.2.2.6-alpha.
    - Handle unsupported or malformed SOCKS5 requests properly by
      responding with the appropriate error message before closing the
      connection. Fixes bugs 12971 and 13314; bugfix on 0.0.2pre13.

  o Minor bugfixes (client, automapping):
    - Avoid crashing on torrc lines for VirtualAddrNetworkIPv[4|6] when
      no value follows the option. Fixes bug 14142; bugfix on
      0.2.4.7-alpha. Patch by "teor".
    - Fix a memory leak when using AutomapHostsOnResolve. Fixes bug
      14195; bugfix on 0.1.0.1-rc.
    - Prevent changes to other options from removing the wildcard value
      "." from "AutomapHostsSuffixes". Fixes bug 12509; bugfix
      on 0.2.0.1-alpha.
    - Allow MapAddress and AutomapHostsOnResolve to work together when
      an address is mapped into another address type (like .onion) that
      must be automapped at resolve time. Fixes bug 7555; bugfix
      on 0.2.0.1-alpha.

  o Minor bugfixes (client, bridges):
    - When we are using bridges and we had a network connectivity
      problem, only retry connecting to our currently configured
      bridges, not all bridges we know about and remember using. Fixes
      bug 14216; bugfix on 0.2.2.17-alpha.

  o Minor bugfixes (client, DNS):
    - Report the correct cached DNS expiration times on SOCKS port or in
      DNS replies. Previously, we would report everything as "never
      expires." Fixes bug 14193; bugfix on 0.2.3.17-beta.
    - Avoid a small memory leak when we find a cached answer for a
      reverse DNS lookup in a client-side DNS cache. (Remember, client-
      side DNS caching is off by default, and is not recommended.) Fixes
      bug 14259; bugfix on 0.2.0.1-alpha.

  o Minor bugfixes (client, IPv6):
    - Reject socks requests to literal IPv6 addresses when IPv6Traffic
      flag is not set; and not because the NoIPv4Traffic flag was set.
      Previously we'd looked at the NoIPv4Traffic flag for both types of
      literal addresses. Fixes bug 14280; bugfix on 0.2.4.7-alpha.

  o Minor bugfixes (client, microdescriptors):
    - Use a full 256 bits of the SHA256 digest of a microdescriptor when
      computing which microdescriptors to download. This keeps us from
      erroneous download behavior if two microdescriptor digests ever
      have the same first 160 bits. Fixes part of bug 13399; bugfix
      on 0.2.3.1-alpha.
    - Reset a router's status if its microdescriptor digest changes,
      even if the first 160 bits remain the same. Fixes part of bug
      13399; bugfix on 0.2.3.1-alpha.

  o Minor bugfixes (client, torrc):
    - Stop modifying the value of our DirReqStatistics torrc option just
      because we're not a bridge or relay. This bug was causing Tor
      Browser users to write "DirReqStatistics 0" in their torrc files
      as if they had chosen to change the config. Fixes bug 4244; bugfix
      on 0.2.3.1-alpha.
    - When GeoIPExcludeUnknown is enabled, do not incorrectly decide
      that our options have changed every time we SIGHUP. Fixes bug
      9801; bugfix on 0.2.4.10-alpha. Patch from "qwerty1".

  o Minor bugfixes (compilation):
    - Fix a compilation warning on s390. Fixes bug 14988; bugfix
      on 0.2.5.2-alpha.
    - Silence clang warnings under --enable-expensive-hardening,
      including implicit truncation of 64 bit values to 32 bit, const
      char assignment to self, tautological compare, and additional
      parentheses around equality tests. Fixes bug 13577; bugfix
      on 0.2.5.4-alpha.
    - Fix a clang warning about checking whether an address in the
      middle of a structure is NULL. Fixes bug 14001; bugfix
      on 0.2.1.2-alpha.
    - The address of an array in the middle of a structure will always
      be non-NULL. clang recognises this and complains. Disable the
      tautologous and redundant check to silence this warning. Fixes bug
      14001; bugfix on 0.2.1.2-alpha.
    - Compile correctly with (unreleased) OpenSSL 1.1.0 headers.
      Addresses ticket 14188.
    - Build without warnings with the stock OpenSSL srtp.h header, which
      has a duplicate declaration of SSL_get_selected_srtp_profile().
      Fixes bug 14220; this is OpenSSL's bug, not ours.
    - Do not compile any code related to Tor2Web mode when Tor2Web mode
      is not enabled at compile time. Previously, this code was included
      in a disabled state. See discussion on ticket 12844.
    - Allow our configure script to build correctly with autoconf 2.62
      again. Fixes bug 12693; bugfix on 0.2.5.2-alpha.
    - Improve the error message from ./configure to make it clear that
      when asciidoc has not been found, the user will have to either add
      --disable-asciidoc argument or install asciidoc. Resolves
      ticket 13228.

  o Minor bugfixes (controller):
    - Report "down" in response to the "GETINFO entry-guards" command
      when relays are down with an unreachable_since value. Previously,
      we would report "up". Fixes bug 14184; bugfix on 0.1.2.2-alpha.
    - Avoid crashing on a malformed EXTENDCIRCUIT command. Fixes bug
      14116; bugfix on 0.2.2.9-alpha.

  o Minor bugfixes (controller):
    - Return an error when the second or later arguments of the
      "setevents" controller command are invalid events. Previously we
      would return success while silently skipping invalid events. Fixes
      bug 13205; bugfix on 0.2.3.2-alpha. Reported by "fpxnns".

  o Minor bugfixes (directory authority):
    - Allow directory authorities to fetch more data from one another if
      they find themselves missing lots of votes. Previously, they had
      been bumping against the 10 MB queued data limit. Fixes bug 14261;
      bugfix on 0.1.2.5-alpha.
    - Do not attempt to download extrainfo documents which we will be
      unable to validate with a matching server descriptor. Fixes bug
      13762; bugfix on 0.2.0.1-alpha.
    - Fix a bug that was truncating AUTHDIR_NEWDESC events sent to the
      control port. Fixes bug 14953; bugfix on 0.2.0.1-alpha.
    - Enlarge the buffer to read bwauth generated files to avoid an
      issue when parsing the file in dirserv_read_measured_bandwidths().
      Fixes bug 14125; bugfix on 0.2.2.1-alpha.
    - When running as a v3 directory authority, advertise that you serve
      extra-info documents so that clients who want them can find them
      from you too. Fixes part of bug 11683; bugfix on 0.2.0.1-alpha.

  o Minor bugfixes (directory system):
    - Always believe that v3 directory authorities serve extra-info
      documents, whether they advertise "caches-extra-info" or not.
      Fixes part of bug 11683; bugfix on 0.2.0.1-alpha.
    - Check the BRIDGE_DIRINFO flag bitwise rather than using equality.
      Previously, directories offering BRIDGE_DIRINFO and some other
      flag (i.e. microdescriptors or extrainfo) would be ignored when
      looking for bridges. Partially fixes bug 13163; bugfix
      on 0.2.0.7-alpha.

  o Minor bugfixes (file handling):
    - Stop failing when key files are zero-length. Instead, generate new
      keys, and overwrite the empty key files. Fixes bug 13111; bugfix
      on all versions of Tor. Patch by "teor".
    - Stop generating a fresh .old RSA onion key file when the .old file
      is missing. Fixes part of 13111; bugfix on 0.0.6rc1.
    - Avoid overwriting .old key files with empty key files.
    - Skip loading zero-length extrainfo store, router store, stats,
      state, and key files.
    - Avoid crashing when trying to reload a torrc specified as a
      relative path with RunAsDaemon turned on. Fixes bug 13397; bugfix
      on 0.2.3.11-alpha.

  o Minor bugfixes (hidden services):
    - Close the introduction circuit when we have no more usable intro
      points, instead of waiting for it to time out. This also ensures
      that no follow-up HS descriptor fetch is triggered when the
      circuit eventually times out. Fixes bug 14224; bugfix on 0.0.6.
    - When fetching a hidden service descriptor for a down service that
      was recently up, do not keep refetching until we try the same
      replica twice in a row. Fixes bug 14219; bugfix on 0.2.0.10-alpha.
    - Correctly send a controller event when we find that a rendezvous
      circuit has finished. Fixes bug 13936; bugfix on 0.1.1.5-alpha.
    - Pre-check directory permissions for new hidden-services to avoid
      at least one case of "Bug: Acting on config options left us in a
      broken state. Dying." Fixes bug 13942; bugfix on 0.0.6pre1.
    - When fetching hidden service descriptors, we now check not only
      for whether we got the hidden service we had in mind, but also
      whether we got the particular descriptors we wanted. This prevents
      a class of inefficient but annoying DoS attacks by hidden service
      directories. Fixes bug 13214; bugfix on 0.2.1.6-alpha. Reported
      by "special".

  o Minor bugfixes (Linux seccomp2 sandbox):
    - Make transparent proxy support work along with the seccomp2
      sandbox. Fixes part of bug 13808; bugfix on 0.2.5.1-alpha. Patch
      by Francisco Blas Izquierdo Riera.
    - Fix a memory leak in tor-resolve when running with the sandbox
      enabled. Fixes bug 14050; bugfix on 0.2.5.9-rc.
    - Allow glibc fatal errors to be sent to stderr before Tor exits.
      Previously, glibc would try to write them to /dev/tty, and the
      sandbox would trap the call and make Tor exit prematurely. Fixes
      bug 14759; bugfix on 0.2.5.1-alpha.

  o Minor bugfixes (logging):
    - Avoid crashing when there are more log domains than entries in
      domain_list. Bugfix on 0.2.3.1-alpha.
    - Downgrade warnings about RSA signature failures to info log level.
      Emit a warning when an extra info document is found incompatible
      with a corresponding router descriptor. Fixes bug 9812; bugfix
      on 0.0.6rc3.
    - Make connection_ap_handshake_attach_circuit() log the circuit ID
      correctly. Fixes bug 13701; bugfix on 0.0.6.

  o Minor bugfixes (networking):
    - Check for orconns and use connection_or_close_for_error() rather
      than connection_mark_for_close() directly in the getsockopt()
      failure case of connection_handle_write_impl(). Fixes bug 11302;
      bugfix on 0.2.4.4-alpha.

  o Minor bugfixes (parsing):
    - Stop accepting milliseconds (or other junk) at the end of
      descriptor publication times. Fixes bug 9286; bugfix on 0.0.2pre25.
    - Support two-number and three-number version numbers correctly, in
      case we change the Tor versioning system in the future. Fixes bug
      13661; bugfix on 0.0.8pre1.

  o Minor bugfixes (portability):
    - Fix the ioctl()-based network interface lookup code so that it
      will work on systems that have variable-length struct ifreq, for
      example Mac OS X.
    - Use the correct datatype in the SipHash-2-4 function to prevent
      compilers from assuming any sort of alignment. Fixes bug 15436;
      bugfix on 0.2.5.3-alpha.

  o Minor bugfixes (preventative security, C safety):
    - When reading a hexadecimal, base-32, or base-64 encoded value from
      a string, always overwrite the whole output buffer. This prevents
      some bugs where we would look at (but fortunately, not reveal)
      uninitialized memory on the stack. Fixes bug 14013; bugfix on all
      versions of Tor.
    - Clear all memory targetted by tor_addr_{to,from}_sockaddr(), not
      just the part that's used. This makes it harder for data leak bugs
      to occur in the event of other programming failures. Resolves
      ticket 14041.

  o Minor bugfixes (relay):
    - When generating our family list, remove spaces from around the
      entries. Fixes bug 12728; bugfix on 0.2.1.7-alpha.
    - If our previous bandwidth estimate was 0 bytes, allow publishing a
      new relay descriptor immediately. Fixes bug 13000; bugfix
      on 0.1.1.6-alpha.

  o Minor bugfixes (shutdown):
    - When shutting down, always call event_del() on lingering read or
      write events before freeing them. Otherwise, we risk double-frees
      or read-after-frees in event_base_free(). Fixes bug 12985; bugfix
      on 0.1.0.2-rc.

  o Minor bugfixes (small memory leaks):
    - Avoid leaking memory when using IPv6 virtual address mappings.
      Fixes bug 14123; bugfix on 0.2.4.7-alpha. Patch by Tom van
      der Woerdt.

  o Minor bugfixes (statistics):
    - Increase period over which bandwidth observations are aggregated
      from 15 minutes to 4 hours. Fixes bug 13988; bugfix on 0.0.8pre1.

  o Minor bugfixes (systemd support):
    - Run correctly under systemd with the RunAsDaemon option set. Fixes
      part of bug 14141; bugfix on 0.2.5.7-rc. Patch from Tomasz Torcz.
    - Inform the systemd supervisor about more changes in the Tor
      process status. Implements part of ticket 14141. Patch from
      Tomasz Torcz.

  o Minor bugfixes (testing networks):
    - Fix TestingDirAuthVoteGuard to properly give out Guard flags in a
      testing network. Fixes bug 13064; bugfix on 0.2.5.2-alpha.
    - Stop using the default authorities in networks which provide both
      AlternateDirAuthority and AlternateBridgeAuthority. Partially
      fixes bug 13163; bugfix on 0.2.0.13-alpha.

  o Minor bugfixes (testing networks, fast startup):
    - Allow Tor to build circuits using a consensus with no exits. If
      the consensus has no exits (typical of a bootstrapping test
      network), allow Tor to build circuits once enough descriptors have
      been downloaded. This assists in bootstrapping a testing Tor
      network. Fixes bug 13718; bugfix on 0.2.4.10-alpha. Patch
      by "teor".
    - When V3AuthVotingInterval is low, give a lower If-Modified-Since
      header to directory servers. This allows us to obtain consensuses
      promptly when the consensus interval is very short. This assists
      in bootstrapping a testing Tor network. Fixes parts of bugs 13718
      and 13963; bugfix on 0.2.0.3-alpha. Patch by "teor".
    - Stop assuming that private addresses are local when checking
      reachability in a TestingTorNetwork. Instead, when testing, assume
      all OR connections are remote. (This is necessary due to many test
      scenarios running all relays on localhost.) This assists in
      bootstrapping a testing Tor network. Fixes bug 13924; bugfix on
      0.1.0.1-rc. Patch by "teor".
    - Avoid building exit circuits from a consensus with no exits. Now
      thanks to our fix for 13718, we accept a no-exit network as not
      wholly lost, but we need to remember not to try to build exit
      circuits on it. Closes ticket 13814; patch by "teor".
    - Stop requiring exits to have non-zero bandwithcapacity in a
      TestingTorNetwork. Instead, when TestingMinExitFlagThreshold is 0,
      ignore exit bandwidthcapacity. This assists in bootstrapping a
      testing Tor network. Fixes parts of bugs 13718 and 13839; bugfix
      on 0.2.0.3-alpha. Patch by "teor".
    - Add "internal" to some bootstrap statuses when no exits are
      available. If the consensus does not contain Exits, Tor will only
      build internal circuits. In this case, relevant statuses will
      contain the word "internal" as indicated in the Tor control-
       spec.txt. When bootstrap completes, Tor will be ready to build
      internal circuits. If a future consensus contains Exits, exit
      circuits may become available. Fixes part of bug 13718; bugfix on
      0.2.4.10-alpha. Patch by "teor".
    - Decrease minimum consensus interval to 10 seconds when
      TestingTorNetwork is set, or 5 seconds for the first consensus.
      Fix assumptions throughout the code that assume larger intervals.
      Fixes bugs 13718 and 13823; bugfix on 0.2.0.3-alpha. Patch
      by "teor".
    - Avoid excluding guards from path building in minimal test
      networks, when we're in a test network and excluding guards would
      exclude all relays. This typically occurs in incredibly small tor
      networks, and those using "TestingAuthVoteGuard *". Fixes part of
      bug 13718; bugfix on 0.1.1.11-alpha. Patch by "teor".

  o Minor bugfixes (testing):
    - Avoid a side-effect in a tor_assert() in the unit tests. Fixes bug
      15188; bugfix on 0.1.2.3-alpha. Patch from Tom van der Woerdt.
    - Stop spawn test failures due to a race condition between the
      SIGCHLD handler updating the process status, and the test reading
      it. Fixes bug 13291; bugfix on 0.2.3.3-alpha.
    - Avoid passing an extra backslash when creating a temporary
      directory for running the unit tests on Windows. Fixes bug 12392;
      bugfix on 0.2.2.25-alpha. Patch from Gisle Vanem.

  o Minor bugfixes (TLS):
    - Check more thoroughly throughout the TLS code for possible
      unlogged TLS errors. Possible diagnostic or fix for bug 13319.

  o Minor bugfixes (transparent proxy):
    - Use getsockname, not getsockopt, to retrieve the address for a
      TPROXY-redirected connection. Fixes bug 13796; bugfix
      on 0.2.5.2-alpha.

  o Minor bugfixes (windows):
    - Remove code to special-case handling of NTE_BAD_KEYSET when
      acquiring windows CryptoAPI context. This error can't actually
      occur for the parameters we're providing. Fixes bug 10816; bugfix
      on 0.0.2pre26.

  o Minor bugfixes (zlib):
    - Avoid truncating a zlib stream when trying to finalize it with an
      empty output buffer. Fixes bug 11824; bugfix on 0.1.1.23.

  o Code simplification and refactoring:
    - Change the entry_is_live() function to take named bitfield
      elements instead of an unnamed list of booleans. Closes
      ticket 12202.
    - Refactor and unit-test entry_is_time_to_retry() in entrynodes.c.
      Resolves ticket 12205.
    - Use calloc and reallocarray functions instead of multiply-
      then-malloc. This makes it less likely for us to fall victim to an
      integer overflow attack when allocating. Resolves ticket 12855.
    - Use the standard macro name SIZE_MAX, instead of our
      own SIZE_T_MAX.
    - Document usage of the NO_DIRINFO and ALL_DIRINFO flags clearly in
      functions which take them as arguments. Replace 0 with NO_DIRINFO
      in a function call for clarity. Seeks to prevent future issues
      like 13163.
    - Avoid 4 null pointer errors under clang static analysis by using
      tor_assert() to prove that the pointers aren't null. Fixes
      bug 13284.
    - Rework the API of policies_parse_exit_policy() to use a bitmask to
      represent parsing options, instead of a confusing mess of
      booleans. Resolves ticket 8197.
    - Introduce a helper function to parse ExitPolicy in
      or_options_t structure.
    - Move fields related to isolating and configuring client ports into
      a shared structure. Previously, they were duplicated across
      port_cfg_t, listener_connection_t, and edge_connection_t. Failure
      to copy them correctly had been the cause of at least one bug in
      the past. Closes ticket 8546.
    - Refactor the get_interface_addresses_raw() doom-function into
      multiple smaller and simpler subfunctions. Cover the resulting
      subfunctions with unit-tests. Fixes a significant portion of
      issue 12376.
    - Remove workaround in dirserv_thinks_router_is_hs_dir() that was
      only for version <= 0.2.2.24 which is now deprecated. Closes
      ticket 14202.
    - Remove a test for a long-defunct broken version-one
      directory server.
    - Refactor main loop to extract the 'loop' part. This makes it
      easier to run Tor under Shadow. Closes ticket 15176.
    - Stop using can_complete_circuits as a global variable; access it
      with a function instead.
    - Avoid using operators directly as macro arguments: this lets us
      apply coccinelle transformations to our codebase more directly.
      Closes ticket 13172.
    - Combine the functions used to parse ClientTransportPlugin and
      ServerTransportPlugin into a single function. Closes ticket 6456.
    - Add inline functions and convenience macros for inspecting channel
      state. Refactor the code to use convenience macros instead of
      checking channel state directly. Fixes issue 7356.
    - Document all members of was_router_added_t and rename
      ROUTER_WAS_NOT_NEW to ROUTER_IS_ALREADY_KNOWN to make it less
      confusable with ROUTER_WAS_TOO_OLD. Fixes issue 13644.
    - In connection_exit_begin_conn(), use END_CIRC_REASON_TORPROTOCOL
      constant instead of hardcoded value. Fixes issue 13840.
    - Refactor our generic strmap and digestmap types into a single
      implementation, so that we can add a new digest256map
      type trivially.

  o Documentation:
    - Add a doc/TUNING document with tips for handling large numbers of
      TCP connections when running busy Tor relay. Update the warning
      message to point to this file when running out of sockets
      operating system is allowing to use simultaneously. Resolves
      ticket 9708.
    - Adding section on OpenBSD to our TUNING document. Thanks to mmcc
      for writing the OpenBSD-specific tips. Resolves ticket 13702.
    - Make the tor-resolve documentation match its help string and its
      options. Resolves part of ticket 14325.
    - Log a more useful error message from tor-resolve when failing to
      look up a hidden service address. Resolves part of ticket 14325.
    - Document the bridge-authority-only 'networkstatus-bridges' file.
      Closes ticket 13713; patch from "tom".
    - Fix typo in PredictedPortsRelevanceTime option description in
      manpage. Resolves issue 13707.
    - Stop suggesting that users specify relays by nickname: it isn't a
      good idea. Also, properly cross-reference how to specify relays in
      all parts of manual documenting options that take a list of
      relays. Closes ticket 13381.
    - Clarify the HiddenServiceDir option description in manpage to make
      it clear that relative paths are taken with respect to the current
      working directory. Also clarify that this behavior is not
      guaranteed to remain indefinitely. Fixes issue 13913.

  o Distribution (systemd):
    - systemd unit file: only allow tor to write to /var/lib/tor and
      /var/log/tor. The rest of the filesystem is accessible for reading
      only. Patch by intrigeri; resolves ticket 12751.
    - systemd unit file: ensure that the process and all its children
      can never gain new privileges. Patch by intrigeri; resolves
      ticket 12939.
    - systemd unit file: set up /var/run/tor as writable for the Tor
      service. Patch by intrigeri; resolves ticket 13196.

  o Downgraded warnings:
    - Don't warn when we've attempted to contact a relay using the wrong
      ntor onion key. Closes ticket 9635.

  o Removed code:
    - Remove some lingering dead code that once supported mempools.
      Mempools were disabled by default in 0.2.5, and removed entirely
      in 0.2.6.3-alpha. Closes more of ticket 14848; patch
      by "cypherpunks".

  o Removed features (directory authorities):
    - Remove code that prevented authorities from listing Tor relays
      affected by CVE-2011-2769 as guards. These relays are already
      rejected altogether due to the minimum version requirement of
      0.2.3.16-alpha. Closes ticket 13152.
    - The "AuthDirRejectUnlisted" option no longer has any effect, as
      the fingerprints file (approved-routers) has been deprecated.
    - Directory authorities do not support being Naming dirauths anymore.
      The "NamingAuthoritativeDir" config option is now obsolete.
    - Directory authorities do not support giving out the BadDirectory
      flag anymore.
    - Directory authorities no longer advertise or support consensus
      methods 1 through 12 inclusive. These consensus methods were
      obsolete and/or insecure: maintaining the ability to support them
      served no good purpose. Implements part of proposal 215; closes
      ticket 10163.

  o Removed features:
    - To avoid confusion with the "ExitRelay" option, "ExitNode" is no
      longer silently accepted as an alias for "ExitNodes".
    - The --enable-mempool and --enable-buf-freelists options, which
      were originally created to work around bad malloc implementations,
      no longer exist. They were off-by-default in 0.2.5. Closes
      ticket 14848.
    - We no longer remind the user about configuration options that have
      been obsolete since 0.2.3.x or earlier. Patch by Adrien Bak.
    - Remove our old, non-weighted bandwidth-based node selection code.
      Previously, we used it as a fallback when we couldn't perform
      weighted bandwidth-based node selection. But that would only
      happen in the cases where we had no consensus, or when we had a
      consensus generated by buggy or ancient directory authorities. In
      either case, it's better to use the more modern, better maintained
      algorithm, with reasonable defaults for the weights. Closes
      ticket 13126.
    - Remove the --disable-curve25519 configure option. Relays and
      clients now are required to support curve25519 and the
      ntor handshake.
    - The old "StrictEntryNodes" and "StrictExitNodes" options, which
      used to be deprecated synonyms for "StrictNodes", are now marked
      obsolete. Resolves ticket 12226.
    - Clients don't understand the BadDirectory flag in the consensus
      anymore, and ignore it.

  o Removed platform support:
    - We no longer include special code to build on Windows CE; as far
      as we know, nobody has used Tor on Windows CE in a very long time.
      Closes ticket 11446.

  o Testing (test-network.sh):
    - Stop using "echo -n", as some shells' built-in echo doesn't
      support "-n". Instead, use "/bin/echo -n". Partially fixes
      bug 13161.
    - Stop an apparent test-network hang when used with make -j2. Fixes
      bug 13331.
    - Add a --delay option to test-network.sh, which configures the
      delay before the chutney network tests for data transmission.
      Partially implements ticket 13161.

  o Testing:
    - Test that tor does not fail when key files are zero-length. Check
      that tor generates new keys, and overwrites the empty key files.
    - Test that tor generates new keys when keys are missing
      (existing behavior).
    - Test that tor does not overwrite key files that already contain
      data (existing behavior). Tests bug 13111. Patch by "teor".
    - New "make test-stem" target to run stem integration tests.
      Requires that the "STEM_SOURCE_DIR" environment variable be set.
      Closes ticket 14107.
    - Make the test_cmdline_args.py script work correctly on Windows.
      Patch from Gisle Vanem.
    - Move the slower unit tests into a new "./src/test/test-slow"
      binary that can be run independently of the other tests. Closes
      ticket 13243.
    - New tests for many parts of channel, relay, and circuitmux
      functionality. Code by Andrea; part of 9262.
    - New tests for parse_transport_line(). Part of ticket 6456.
    - In the unit tests, use chgrp() to change the group of the unit
      test temporary directory to the current user, so that the sticky
      bit doesn't interfere with tests that check directory groups.
      Closes 13678.
    - Add unit tests for resolve_my_addr(). Part of ticket 12376; patch
      by 'rl1987'.
    - Refactor the function that chooses guard nodes so that it can more
      easily be tested; write some tests for it.
    - Fix and re-enable the fgets_eagain unit test. Fixes bug 12503;
      bugfix on 0.2.3.1-alpha. Patch from "cypherpunks."
    - Create unit tests for format_time_interval(). With bug 13393.
    - Add unit tests for tor_timegm signed overflow, tor_timegm and
      parse_rfc1123_time validity checks, correct_tm year clamping. Unit
      tests (visible) fixes in bug 13476.
    - Add a "coverage-html" make target to generate HTML-visualized
      coverage results when building with --enable-coverage. (Requires
      lcov.) Patch from Kevin Murray.
    - Enable the backtrace handler (where supported) when running the
      unit tests.
    - Revise all unit tests that used the legacy test_* macros to
      instead use the recommended tt_* macros. This patch was generated
      with coccinelle, to avoid manual errors. Closes ticket 13119.

Changes in version 0.2.5.11 - 2015-03-17
  Tor 0.2.5.11 is the second stable release in the 0.2.5 series.

  It backports several bugfixes from the 0.2.6 branch, including a
  couple of medium-level security fixes for relays and exit nodes.
  It also updates the list of directory authorities.

  o Directory authority changes:
    - Remove turtles as a directory authority.
    - Add longclaw as a new (v3) directory authority. This implements
      ticket 13296. This keeps the directory authority count at 9.
    - The directory authority Faravahar has a new IP address. This
      closes ticket 14487.

  o Major bugfixes (crash, OSX, security):
    - Fix a remote denial-of-service opportunity caused by a bug in
      OSX's _strlcat_chk() function. Fixes bug 15205; bug first appeared
      in OSX 10.9.

  o Major bugfixes (relay, stability, possible security):
    - Fix a bug that could lead to a relay crashing with an assertion
      failure if a buffer of exactly the wrong layout was passed to
      buf_pullup() at exactly the wrong time. Fixes bug 15083; bugfix on
      0.2.0.10-alpha. Patch from 'cypherpunks'.
    - Do not assert if the 'data' pointer on a buffer is advanced to the
      very end of the buffer; log a BUG message instead. Only assert if
      it is past that point. Fixes bug 15083; bugfix on 0.2.0.10-alpha.

  o Major bugfixes (exit node stability):
    - Fix an assertion failure that could occur under high DNS load.
      Fixes bug 14129; bugfix on Tor 0.0.7rc1. Found by "jowr";
      diagnosed and fixed by "cypherpunks".

  o Major bugfixes (Linux seccomp2 sandbox):
    - Upon receiving sighup with the seccomp2 sandbox enabled, do not
      crash during attempts to call wait4. Fixes bug 15088; bugfix on
      0.2.5.1-alpha. Patch from "sanic".

  o Minor features (controller):
    - New "GETINFO bw-event-cache" to get information about recent
      bandwidth events. Closes ticket 14128. Useful for controllers to
      get recent bandwidth history after the fix for ticket 13988.

  o Minor features (geoip):
    - Update geoip to the March 3 2015 Maxmind GeoLite2 Country database.
    - Update geoip6 to the March 3 2015 Maxmind GeoLite2
      Country database.

  o Minor bugfixes (client, automapping):
    - Avoid crashing on torrc lines for VirtualAddrNetworkIPv[4|6] when
      no value follows the option. Fixes bug 14142; bugfix on
      0.2.4.7-alpha. Patch by "teor".
    - Fix a memory leak when using AutomapHostsOnResolve. Fixes bug
      14195; bugfix on 0.1.0.1-rc.

  o Minor bugfixes (compilation):
    - Build without warnings with the stock OpenSSL srtp.h header, which
      has a duplicate declaration of SSL_get_selected_srtp_profile().
      Fixes bug 14220; this is OpenSSL's bug, not ours.

  o Minor bugfixes (directory authority):
    - Allow directory authorities to fetch more data from one another if
      they find themselves missing lots of votes. Previously, they had
      been bumping against the 10 MB queued data limit. Fixes bug 14261;
      bugfix on 0.1.2.5-alpha.
    - Enlarge the buffer to read bwauth generated files to avoid an
      issue when parsing the file in dirserv_read_measured_bandwidths().
      Fixes bug 14125; bugfix on 0.2.2.1-alpha.

  o Minor bugfixes (statistics):
    - Increase period over which bandwidth observations are aggregated
      from 15 minutes to 4 hours. Fixes bug 13988; bugfix on 0.0.8pre1.

  o Minor bugfixes (preventative security, C safety):
    - When reading a hexadecimal, base-32, or base-64 encoded value from
      a string, always overwrite the whole output buffer. This prevents
      some bugs where we would look at (but fortunately, not reveal)
      uninitialized memory on the stack. Fixes bug 14013; bugfix on all
      versions of Tor.


Changes in version 0.2.4.26 - 2015-03-17
  Tor 0.2.4.26 includes an updated list of directory authorities.  It
  also backports a couple of stability and security bugfixes from 0.2.5
  and beyond.

  o Directory authority changes:
    - Remove turtles as a directory authority.
    - Add longclaw as a new (v3) directory authority. This implements
      ticket 13296. This keeps the directory authority count at 9.
    - The directory authority Faravahar has a new IP address. This
      closes ticket 14487.

  o Major bugfixes (exit node stability, also in 0.2.6.3-alpha):
    - Fix an assertion failure that could occur under high DNS load.
      Fixes bug 14129; bugfix on Tor 0.0.7rc1. Found by "jowr";
      diagnosed and fixed by "cypherpunks".

  o Major bugfixes (relay, stability, possible security, also in 0.2.6.4-rc):
    - Fix a bug that could lead to a relay crashing with an assertion
      failure if a buffer of exactly the wrong layout was passed to
      buf_pullup() at exactly the wrong time. Fixes bug 15083; bugfix on
      0.2.0.10-alpha. Patch from 'cypherpunks'.
    - Do not assert if the 'data' pointer on a buffer is advanced to the
      very end of the buffer; log a BUG message instead. Only assert if
      it is past that point. Fixes bug 15083; bugfix on 0.2.0.10-alpha.

  o Minor features (geoip):
    - Update geoip to the March 3 2015 Maxmind GeoLite2 Country database.
    - Update geoip6 to the March 3 2015 Maxmind GeoLite2
      Country database.

Changes in version 0.2.5.10 - 2014-10-24
  Tor 0.2.5.10 is the first stable release in the 0.2.5 series.

  It adds several new security features, including improved
  denial-of-service resistance for relays, new compiler hardening
  options, and a system-call sandbox for hardened installations on Linux
  (requires seccomp2). The controller protocol has several new features,
  resolving IPv6 addresses should work better than before, and relays
  should be a little more CPU-efficient. We've added support for more
  OpenBSD and FreeBSD transparent proxy types. We've improved the build
  system and testing infrastructure to allow unit testing of more parts
  of the Tor codebase. Finally, we've addressed several nagging pluggable
  transport usability issues, and included numerous other small bugfixes
  and features mentioned below.

  This release marks end-of-life for Tor 0.2.3.x; those Tor versions
  have accumulated many known flaws; everyone should upgrade.

  o Major features (security):
    - The ntor handshake is now on-by-default, no matter what the
      directory authorities recommend. Implements ticket 8561.
    - Make the "tor-gencert" tool used by directory authority operators
      create 2048-bit signing keys by default (rather than 1024-bit, since
      1024-bit is uncomfortably small these days). Addresses ticket 10324.
    - Warn about attempts to run hidden services and relays in the same
      process: that's probably not a good idea. Closes ticket 12908.
    - Disable support for SSLv3. All versions of OpenSSL in use with Tor
      today support TLS 1.0 or later, so we can safely turn off support
      for this old (and insecure) protocol. Fixes bug 13426.

  o Major features (relay security, DoS-resistance):
    - When deciding whether we have run out of memory and we need to
      close circuits, also consider memory allocated in buffers for
      streams attached to each circuit.

      This change, which extends an anti-DoS feature introduced in
      0.2.4.13-alpha and improved in 0.2.4.14-alpha, lets Tor exit relays
      better resist more memory-based DoS attacks than before. Since the
      MaxMemInCellQueues option now applies to all queues, it is renamed
      to MaxMemInQueues. This feature fixes bug 10169.
    - Avoid hash-flooding denial-of-service attacks by using the secure
      SipHash-2-4 hash function for our hashtables. Without this
      feature, an attacker could degrade performance of a targeted
      client or server by flooding their data structures with a large
      number of entries to be stored at the same hash table position,
      thereby slowing down the Tor instance. With this feature, hash
      table positions are derived from a randomized cryptographic key,
      and an attacker cannot predict which entries will collide. Closes
      ticket 4900.
    - If you don't specify MaxMemInQueues yourself, Tor now tries to
      pick a good value based on your total system memory. Previously,
      the default was always 8 GB. You can still override the default by
      setting MaxMemInQueues yourself. Resolves ticket 11396.

  o Major features (bridges and pluggable transports):
    - Add support for passing arguments to managed pluggable transport
      proxies. Implements ticket 3594.
    - Bridges now track GeoIP information and the number of their users
      even when pluggable transports are in use, and report usage
      statistics in their extra-info descriptors. Resolves tickets 4773
      and 5040.
    - Don't launch pluggable transport proxies if we don't have any
      bridges configured that would use them. Now we can list many
      pluggable transports, and Tor will dynamically start one when it
      hears a bridge address that needs it. Resolves ticket 5018.
    - The bridge directory authority now assigns status flags (Stable,
      Guard, etc) to bridges based on thresholds calculated over all
      Running bridges. Now bridgedb can finally make use of its features
      to e.g. include at least one Stable bridge in its answers. Fixes
      bug 9859.

  o Major features (controller):
    - Extend ORCONN controller event to include an "ID" parameter,
      and add four new controller event types CONN_BW, CIRC_BW,
      CELL_STATS, and TB_EMPTY that show connection and circuit usage.
      The new events are emitted in private Tor networks only, with the
      goal of being able to better track performance and load during
      full-network simulations. Implements proposal 218 and ticket 7359.

  o Major features (relay performance):
    - Speed up server-side lookups of rendezvous and introduction point
      circuits by using hashtables instead of linear searches. These
      functions previously accounted between 3 and 7% of CPU usage on
      some busy relays. Resolves ticket 9841.
    - Avoid wasting CPU when extending a circuit over a channel that is
      nearly out of circuit IDs. Previously, we would do a linear scan
      over possible circuit IDs before finding one or deciding that we
      had exhausted our possibilities. Now, we try at most 64 random
      circuit IDs before deciding that we probably won't succeed. Fixes
      a possible root cause of ticket 11553.

  o Major features (seccomp2 sandbox, Linux only):
    - Use the seccomp2 syscall filtering facility on Linux to limit
      which system calls Tor can invoke. This is an experimental,
      Linux-only feature to provide defense-in-depth against unknown
      attacks. To try turning it on, set "Sandbox 1" in your torrc
      file. Please be ready to report bugs. We hope to add support
      for better sandboxing in the future, including more fine-grained
      filters, better division of responsibility, and support for more
      platforms. This work has been done by Cristian-Matei Toader for
      Google Summer of Code. Resolves tickets 11351 and 11465.

  o Major features (testing networks):
    - Make testing Tor networks bootstrap better: lower directory fetch
      retry schedules and maximum interval without directory requests,
      and raise maximum download tries. Implements ticket 6752.
    - Add make target 'test-network' to run tests on a Chutney network.
      Implements ticket 8530.

  o Major features (other):
    - On some platforms (currently: recent OSX versions, glibc-based
      platforms that support the ELF format, and a few other
      Unix-like operating systems), Tor can now dump stack traces
      when a crash occurs or an assertion fails. By default, traces
      are dumped to stderr (if possible) and to any logs that are
      reporting errors. Implements ticket 9299.

  o Deprecated versions:
    - Tor 0.2.3.x has reached end-of-life; it has received no patches or
      attention for some while.

  o Major bugfixes (security, directory authorities):
    - Directory authorities now include a digest of each relay's
      identity key as a part of its microdescriptor.

      This is a workaround for bug 11743 (reported by "cypherpunks"),
      where Tor clients do not support receiving multiple
      microdescriptors with the same SHA256 digest in the same
      consensus. When clients receive a consensus like this, they only
      use one of the relays. Without this fix, a hostile relay could
      selectively disable some client use of target relays by
      constructing a router descriptor with a different identity and the
      same microdescriptor parameters and getting the authorities to
      list it in a microdescriptor consensus. This fix prevents an
      attacker from causing a microdescriptor collision, because the
      router's identity is not forgeable.

  o Major bugfixes (openssl bug workaround):
    - Avoid crashing when using OpenSSL version 0.9.8zc, 1.0.0o, or
      1.0.1j, built with the 'no-ssl3' configuration option. Fixes
      bug 13471. This is a workaround for an OpenSSL bug.

  o Major bugfixes (client):
    - Perform circuit cleanup operations even when circuit
      construction operations are disabled (because the network is
      disabled, or because there isn't enough directory information).
      Previously, when we were not building predictive circuits, we
      were not closing expired circuits either. Fixes bug 8387; bugfix on
      0.1.1.11-alpha. This bug became visible in 0.2.4.10-alpha when we
      became more strict about when we have "enough directory information
      to build circuits".

  o Major bugfixes (client, pluggable transports):
    - When managing pluggable transports, use OS notification facilities
      to learn if they have crashed, and don't attempt to kill any
      process that has already exited. Fixes bug 8746; bugfix
      on 0.2.3.6-alpha.

  o Major bugfixes (relay denial of service):
    - Instead of writing destroy cells directly to outgoing connection
      buffers, queue them and intersperse them with other outgoing cells.
      This can prevent a set of resource starvation conditions where too
      many pending destroy cells prevent data cells from actually getting
      delivered. Reported by "oftc_must_be_destroyed". Fixes bug 7912;
      bugfix on 0.2.0.1-alpha.

  o Major bugfixes (relay):
    - Avoid queuing or sending destroy cells for circuit ID zero when we
      fail to send a CREATE cell. Fixes bug 12848; bugfix on 0.0.8pre1.
      Found and fixed by "cypherpunks".
    - Fix ORPort reachability detection on relays running behind a
      proxy, by correctly updating the "local" mark on the controlling
      channel when changing the address of an or_connection_t after the
      handshake. Fixes bug 12160; bugfix on 0.2.4.4-alpha.
    - Use a direct dirport connection when uploading non-anonymous
      descriptors to the directory authorities. Previously, relays would
      incorrectly use tunnel connections under a fairly wide variety of
      circumstances. Fixes bug 11469; bugfix on 0.2.4.3-alpha.
    - When a circuit accidentally has the same circuit ID for its
      forward and reverse direction, correctly detect the direction of
      cells using that circuit. Previously, this bug made roughly one
      circuit in a million non-functional. Fixes bug 12195; this is a
      bugfix on every version of Tor.

  o Minor features (security):
    - New --enable-expensive-hardening option to enable security
      hardening options that consume nontrivial amounts of CPU and
      memory. Right now, this includes AddressSanitizer and UbSan, which
      are supported in newer versions of GCC and Clang. Closes ticket
      11477.
    - Authorities now assign the Guard flag to the fastest 25% of the
      network (it used to be the fastest 50%). Also raise the consensus
      weight that guarantees the Guard flag from 250 to 2000. For the
      current network, this results in about 1100 guards, down from 2500.
      This step paves the way for moving the number of entry guards
      down to 1 (proposal 236) while still providing reasonable expected
      performance for most users. Implements ticket 12690.

  o Minor features (security, memory management):
    - Memory allocation tricks (mempools and buffer freelists) are now
      disabled by default. You can turn them back on with
      --enable-mempools and --enable-buf-freelists respectively. We're
      disabling these features because malloc performance is good enough
      on most platforms, and a similar feature in OpenSSL exacerbated
      exploitation of the Heartbleed attack. Resolves ticket 11476.

  o Minor features (bridge client):
    - Report a more useful failure message when we can't connect to a
      bridge because we don't have the right pluggable transport
      configured. Resolves ticket 9665. Patch from Fábio J. Bertinatto.

  o Minor features (bridge):
    - Add an ExtORPortCookieAuthFileGroupReadable option to make the
      cookie file for the ExtORPort g+r by default.

  o Minor features (bridges, pluggable transports):
    - Bridges now write the SHA1 digest of their identity key
      fingerprint (that is, a hash of a hash of their public key) to
      notice-level logs, and to a new hashed-fingerprint file. This
      information will help bridge operators look up their bridge in
      Globe and similar tools. Resolves ticket 10884.
    - Improve the message that Tor displays when running as a bridge
      using pluggable transports without an Extended ORPort listener.
      Also, log the message in the log file too. Resolves ticket 11043.
    - Add threshold cutoffs to the networkstatus document created by
      the Bridge Authority. Fixes bug 1117.
    - On Windows, spawn background processes using the CREATE_NO_WINDOW
      flag. Now Tor Browser Bundle 3.5 with pluggable transports enabled
      doesn't pop up a blank console window. (In Tor Browser Bundle 2.x,
      Vidalia set this option for us.) Implements ticket 10297.

  o Minor features (build):
    - The configure script has a --disable-seccomp option to turn off
      support for libseccomp on systems that have it, in case it (or
      Tor's use of it) is broken. Resolves ticket 11628.
    - Assume that a user using ./configure --host wants to cross-compile,
      and give an error if we cannot find a properly named
      tool-chain. Add a --disable-tool-name-check option to proceed
      nevertheless. Addresses ticket 9869. Patch by Benedikt Gollatz.
    - If we run ./configure and the compiler recognizes -fstack-protector
      but the linker rejects it, warn the user about a potentially missing
      libssp package. Addresses ticket 9948. Patch from Benedikt Gollatz.
    - Add support for `--library-versions` flag. Implements ticket 6384.
    - Return the "unexpected sendme" warnings to a warn severity, but make
      them rate limited, to help diagnose ticket 8093.
    - Detect a missing asciidoc, and warn the user about it, during
      configure rather than at build time. Fixes issue 6506. Patch from
      Arlo Breault.

  o Minor features (client):
    - Add a new option, PredictedPortsRelevanceTime, to control how long
      after having received a request to connect to a given port Tor
      will try to keep circuits ready in anticipation of future requests
      for that port. Patch from "unixninja92"; implements ticket 9176.

  o Minor features (config options and command line):
    - Add an --allow-missing-torrc commandline option that tells Tor to
      run even if the configuration file specified by -f is not available.
      Implements ticket 10060.
    - Add support for the TPROXY transparent proxying facility on Linux.
      See documentation for the new TransProxyType option for more
      details. Implementation by "thomo". Closes ticket 10582.

  o Minor features (config options):
    - Config (torrc) lines now handle fingerprints which are missing
      their initial '$'. Resolves ticket 4341; improvement over 0.0.9pre5.
    - Support a --dump-config option to print some or all of the
      configured options. Mainly useful for debugging the command-line
      option parsing code. Helps resolve ticket 4647.
    - Raise awareness of safer logging: notify user of potentially
      unsafe config options, like logging more verbosely than severity
      "notice" or setting SafeLogging to 0. Resolves ticket 5584.
    - Add a new configuration option TestingV3AuthVotingStartOffset
      that bootstraps a network faster by changing the timing for
      consensus votes. Addresses ticket 8532.
    - Add a new torrc option "ServerTransportOptions" that allows
      bridge operators to pass configuration parameters to their
      pluggable transports. Resolves ticket 8929.
    - The config (torrc) file now accepts bandwidth and space limits in
      bits as well as bytes. (Anywhere that you can say "2 Kilobytes",
      you can now say "16 kilobits", and so on.) Resolves ticket 9214.
      Patch by CharlieB.

  o Minor features (controller):
    - Make the entire exit policy available from the control port via
      GETINFO exit-policy/*. Implements enhancement 7952. Patch from
      "rl1987".
    - Because of the fix for ticket 11396, the real limit for memory
      usage may no longer match the configured MaxMemInQueues value. The
      real limit is now exposed via GETINFO limits/max-mem-in-queues.
    - Add a new "HS_DESC" controller event that reports activities
      related to hidden service descriptors. Resolves ticket 8510.
    - New "DROPGUARDS" controller command to forget all current entry
      guards. Not recommended for ordinary use, since replacing guards
      too frequently makes several attacks easier. Resolves ticket 9934;
      patch from "ra".
    - Implement the TRANSPORT_LAUNCHED control port event that
      notifies controllers about new launched pluggable
      transports. Resolves ticket 5609.

  o Minor features (diagnostic):
    - When logging a warning because of bug 7164, additionally check the
      hash table for consistency (as proposed on ticket 11737). This may
      help diagnose bug 7164.
    - When we log a heartbeat, log how many one-hop circuits we have
      that are at least 30 minutes old, and log status information about
      a few of them. This is an attempt to track down bug 8387.
    - When encountering an unexpected CR while writing text to a file on
      Windows, log the name of the file. Should help diagnosing
      bug 11233.
    - Give more specific warnings when a client notices that an onion
      handshake has failed. Fixes ticket 9635.
    - Add significant new logging code to attempt to diagnose bug 12184,
      where relays seem to run out of available circuit IDs.
    - Improve the diagnostic log message for bug 8387 even further to
      try to improve our odds of figuring out why one-hop directory
      circuits sometimes do not get closed.
    - Add more log messages to diagnose bug 7164, which causes
      intermittent "microdesc_free() called but md was still referenced"
      warnings. We now include more information, to figure out why we
      might be cleaning a microdescriptor for being too old if it's
      still referenced by a live node_t object.
    - Log current accounting state (bytes sent and received + remaining
      time for the current accounting period) in the relay's heartbeat
      message. Implements ticket 5526; patch from Peter Retzlaff.

  o Minor features (geoip):
    - Update geoip and geoip6 to the August 7 2014 Maxmind GeoLite2
      Country database.

  o Minor features (interface):
    - Generate a warning if any ports are listed in the SocksPolicy,
      DirPolicy, AuthDirReject, AuthDirInvalid, AuthDirBadDir, or
      AuthDirBadExit options. (These options only support address
      ranges.) Fixes part of ticket 11108.

  o Minor features (kernel API usage):
    - Use the SOCK_NONBLOCK socket type, if supported, to open nonblocking
      sockets in a single system call. Implements ticket 5129.

  o Minor features (log messages):
    - When ServerTransportPlugin is set on a bridge, Tor can write more
      useful statistics about bridge use in its extrainfo descriptors,
      but only if the Extended ORPort ("ExtORPort") is set too. Add a
      log message to inform the user in this case. Resolves ticket 9651.
    - When receiving a new controller connection, log the origin address.
      Resolves ticket 9698; patch from "sigpipe".
    - When logging OpenSSL engine status at startup, log the status of
      more engines. Fixes ticket 10043; patch from Joshua Datko.

  o Minor features (log verbosity):
    - Demote the message that we give when a flushing connection times
      out for too long from NOTICE to INFO. It was usually meaningless.
      Resolves ticket 5286.
    - Don't log so many notice-level bootstrapping messages at startup
      about downloading descriptors. Previously, we'd log a notice
      whenever we learned about more routers. Now, we only log a notice
      at every 5% of progress. Fixes bug 9963.
    - Warn less verbosely when receiving a malformed
      ESTABLISH_RENDEZVOUS cell. Fixes ticket 11279.

  o Minor features (performance):
    - If we're using the pure-C 32-bit curve25519_donna implementation
      of curve25519, build it with the -fomit-frame-pointer option to
      make it go faster on register-starved hosts. This improves our
      handshake performance by about 6% on i386 hosts without nacl.
      Closes ticket 8109.

  o Minor features (relay):
    - If a circuit timed out for at least 3 minutes, check if we have a
      new external IP address, and publish a new descriptor with the new
      IP address if it changed. Resolves ticket 2454.

  o Minor features (testing):
    - If Python is installed, "make check" now runs extra tests beyond
      the unit test scripts.
    - When bootstrapping a test network, sometimes very few relays get
      the Guard flag. Now a new option "TestingDirAuthVoteGuard" can
      specify a set of relays which should be voted Guard regardless of
      their uptime or bandwidth. Addresses ticket 9206.

  o Minor features (transparent proxy, *BSD):
    - Support FreeBSD's ipfw firewall interface for TransPort ports on
      FreeBSD. To enable it, set "TransProxyType ipfw". Resolves ticket
      10267; patch from "yurivict".
    - Support OpenBSD's divert-to rules with the pf firewall for
      transparent proxy ports. To enable it, set "TransProxyType
      pf-divert". This allows Tor to run a TransPort transparent proxy
      port on OpenBSD 4.4 or later without root privileges. See the
      pf.conf(5) manual page for information on configuring pf to use
      divert-to rules. Closes ticket 10896; patch from Dana Koch.

  o Minor bugfixes (bridge client):
    - Stop accepting bridge lines containing hostnames. Doing so would
      cause clients to perform DNS requests on the hostnames, which was
      not sensible behavior. Fixes bug 10801; bugfix on 0.2.0.1-alpha.

  o Minor bugfixes (bridges):
    - Avoid potential crashes or bad behavior when launching a
      server-side managed proxy with ORPort or ExtORPort temporarily
      disabled. Fixes bug 9650; bugfix on 0.2.3.16-alpha.
    - Fix a bug where the first connection works to a bridge that uses a
      pluggable transport with client-side parameters, but we don't send
      the client-side parameters on subsequent connections. (We don't
      use any pluggable transports with client-side parameters yet,
      but ScrambleSuit will soon become the first one.) Fixes bug 9162;
      bugfix on 0.2.0.3-alpha. Based on a patch from "rl1987".

  o Minor bugfixes (build, auxiliary programs):
    - Stop preprocessing the "torify" script with autoconf, since
      it no longer refers to LOCALSTATEDIR. Fixes bug 5505; patch
      from Guilhem.
    - The tor-fw-helper program now follows the standard convention and
      exits with status code "0" on success. Fixes bug 9030; bugfix on
      0.2.3.1-alpha. Patch by Arlo Breault.
    - Corrected ./configure advice for what openssl dev package you should
      install on Debian. Fixes bug 9207; bugfix on 0.2.0.1-alpha.

  o Minor bugfixes (client):
    - Avoid "Tried to open a socket with DisableNetwork set" warnings
      when starting a client with bridges configured and DisableNetwork
      set. (Tor launcher starts Tor with DisableNetwork set the first
      time it runs.) Fixes bug 10405; bugfix on 0.2.3.9-alpha.
    - Improve the log message when we can't connect to a hidden service
      because all of the hidden service directory nodes hosting its
      descriptor are excluded. Improves on our fix for bug 10722, which
      was a bugfix on 0.2.0.10-alpha.
    - Raise a control port warning when we fail to connect to all of
      our bridges. Previously, we didn't inform the controller, and
      the bootstrap process would stall. Fixes bug 11069; bugfix on
      0.2.1.2-alpha.
    - Exit immediately when a process-owning controller exits.
      Previously, tor relays would wait for a little while after their
      controller exited, as if they had gotten an INT signal -- but this
      was problematic, since there was no feedback for the user. To do a
      clean shutdown, controllers should send an INT signal and give Tor
      a chance to clean up. Fixes bug 10449; bugfix on 0.2.2.28-beta.
    - Stop attempting to connect to bridges before our pluggable
      transports are configured (harmless but resulted in some erroneous
      log messages). Fixes bug 11156; bugfix on 0.2.3.2-alpha.
    - Fix connections to IPv6 addresses over SOCKS5. Previously, we were
      generating incorrect SOCKS5 responses, and confusing client
      applications. Fixes bug 10987; bugfix on 0.2.4.7-alpha.

  o Minor bugfixes (client, DNSPort):
    - When using DNSPort, try to respond to AAAA requests with AAAA
      answers. Previously, we hadn't looked at the request type when
      deciding which answer type to prefer. Fixes bug 10468; bugfix on
      0.2.4.7-alpha.
    - When receiving a DNS query for an unsupported record type, reply
      with no answer rather than with a NOTIMPL error. This behavior
      isn't correct either, but it will break fewer client programs, we
      hope. Fixes bug 10268; bugfix on 0.2.0.1-alpha. Original patch
      from "epoch".

  o Minor bugfixes (client, logging during bootstrap):
    - Only report the first fatal bootstrap error on a given OR
      connection. This stops us from telling the controller bogus error
      messages like "DONE". Fixes bug 10431; bugfix on 0.2.1.1-alpha.
    - Avoid generating spurious warnings when starting with
      DisableNetwork enabled. Fixes bug 11200 and bug 10405; bugfix on
      0.2.3.9-alpha.

  o Minor bugfixes (closing OR connections):
    - If write_to_buf() in connection_write_to_buf_impl_() ever fails,
      check if it's an or_connection_t and correctly call
      connection_or_close_for_error() rather than
      connection_mark_for_close() directly. Fixes bug 11304; bugfix on
      0.2.4.4-alpha.
    - When closing all connections on setting DisableNetwork to 1, use
      connection_or_close_normally() rather than closing OR connections
      out from under the channel layer. Fixes bug 11306; bugfix on
      0.2.4.4-alpha.

  o Minor bugfixes (code correctness):
    - Previously we used two temporary files when writing descriptors to
      disk; now we only use one. Fixes bug 1376.
    - Remove an erroneous (but impossible and thus harmless) pointer
      comparison that would have allowed compilers to skip a bounds
      check in channeltls.c. Fixes bugs 10313 and 9980; bugfix on
      0.2.0.10-alpha. Noticed by Jared L Wong and David Fifield.
    - Fix an always-true assertion in pluggable transports code so it
      actually checks what it was trying to check. Fixes bug 10046;
      bugfix on 0.2.3.9-alpha. Found by "dcb".

  o Minor bugfixes (command line):
    - Use a single command-line parser for parsing torrc options on the
      command line and for finding special command-line options to avoid
      inconsistent behavior for torrc option arguments that have the same
      names as command-line options. Fixes bugs 4647 and 9578; bugfix on
      0.0.9pre5.
    - No longer allow 'tor --hash-password' with no arguments. Fixes bug
      9573; bugfix on 0.0.9pre5.

  o Minor bugfixes (compilation):
    - Compile correctly with builds and forks of OpenSSL (such as
      LibreSSL) that disable compression. Fixes bug 12602; bugfix on
      0.2.1.1-alpha. Patch from "dhill".
    - Restore the ability to compile Tor with V2_HANDSHAKE_SERVER
      turned off (that is, without support for v2 link handshakes). Fixes
      bug 4677; bugfix on 0.2.3.2-alpha. Patch from "piet".
    - In routerlist_assert_ok(), don't take the address of a
      routerinfo's cache_info member unless that routerinfo is non-NULL.
      Fixes bug 13096; bugfix on 0.1.1.9-alpha. Patch by "teor".
    - Fix a large number of false positive warnings from the clang
      analyzer static analysis tool. This should make real warnings
      easier for clang analyzer to find. Patch from "teor". Closes
      ticket 13036.
    - Resolve GCC complaints on OpenBSD about discarding constness in
      TO_{ORIGIN,OR}_CIRCUIT functions. Fixes part of bug 11633; bugfix
      on 0.1.1.23. Patch from Dana Koch.
    - Resolve clang complaints on OpenBSD with -Wshorten-64-to-32 due to
      treatment of long and time_t as comparable types. Fixes part of
      bug 11633. Patch from Dana Koch.
    - When deciding whether to build the 64-bit curve25519
      implementation, detect platforms where we can compile 128-bit
      arithmetic but cannot link it. Fixes bug 11729; bugfix on
      0.2.4.8-alpha. Patch from "conradev".
    - Fix compilation when DNS_CACHE_DEBUG is enabled. Fixes bug 11761;
      bugfix on 0.2.3.13-alpha. Found by "cypherpunks".
    - Fix compilation with dmalloc. Fixes bug 11605; bugfix
      on 0.2.4.10-alpha.
    - Build and run correctly on systems like OpenBSD-current that have
      patched OpenSSL to remove get_cipher_by_char and/or its
      implementations. Fixes issue 13325.

  o Minor bugfixes (controller and command-line):
    - If changing a config option via "setconf" fails in a recoverable
      way, we used to nonetheless write our new control ports to the
      file described by the "ControlPortWriteToFile" option. Now we only
      write out that file if we successfully switch to the new config
      option. Fixes bug 5605; bugfix on 0.2.2.26-beta. Patch from "Ryman".

  o Minor bugfixes (directory server):
    - No longer accept malformed http headers when parsing urls from
      headers. Now we reply with Bad Request ("400"). Fixes bug 2767;
      bugfix on 0.0.6pre1.
    - When sending a compressed set of descriptors or microdescriptors,
      make sure to finalize the zlib stream. Previously, we would write
      all the compressed data, but if the last descriptor we wanted to
      send was missing or too old, we would not mark the stream as
      finished. This caused problems for decompression tools. Fixes bug
      11648; bugfix on 0.1.1.23.

  o Minor bugfixes (hidden service):
    - Only retry attempts to connect to a chosen rendezvous point 8
      times, not 30. Fixes bug 4241; bugfix on 0.1.0.1-rc.

  o Minor bugfixes (interface):
    - Reject relative control socket paths and emit a warning. Previously,
      single-component control socket paths would be rejected, but Tor
      would not log why it could not validate the config. Fixes bug 9258;
      bugfix on 0.2.3.16-alpha.

  o Minor bugfixes (log messages):
    - Fix a bug where clients using bridges would report themselves
      as 50% bootstrapped even without a live consensus document.
      Fixes bug 9922; bugfix on 0.2.1.1-alpha.
    - Suppress a warning where, if there's only one directory authority
      in the network, we would complain that votes and signatures cannot
      be uploaded to other directory authorities. Fixes bug 10842;
      bugfix on 0.2.2.26-beta.
    - Report bootstrapping progress correctly when we're downloading
      microdescriptors. We had updated our "do we have enough microdescs
      to begin building circuits?" logic most recently in 0.2.4.10-alpha
      (see bug 5956), but we left the bootstrap status event logic at
      "how far through getting 1/4 of them are we?" Fixes bug 9958;
      bugfix on 0.2.2.36, which is where they diverged (see bug 5343).

  o Minor bugfixes (logging):
    - Downgrade "Unexpected onionskin length after decryption" warning
      to a protocol-warn, since there's nothing relay operators can do
      about a client that sends them a malformed create cell. Resolves
      bug 12996; bugfix on 0.0.6rc1.
    - Log more specific warnings when we get an ESTABLISH_RENDEZVOUS
      cell on a cannibalized or non-OR circuit. Resolves ticket 12997.
    - When logging information about an EXTEND2 or EXTENDED2 cell, log
      their names correctly. Fixes part of bug 12700; bugfix
      on 0.2.4.8-alpha.
    - When logging information about a relay cell whose command we don't
      recognize, log its command as an integer. Fixes part of bug 12700;
      bugfix on 0.2.1.10-alpha.
    - Escape all strings from the directory connection before logging
      them. Fixes bug 13071; bugfix on 0.1.1.15. Patch from "teor".
    - Squelch a spurious LD_BUG message "No origin circuit for
      successful SOCKS stream" in certain hidden service failure cases;
      fixes bug 10616.
    - Downgrade the severity of the 'unexpected sendme cell from client'
      from 'warn' to 'protocol warning'. Closes ticket 8093.

  o Minor bugfixes (misc code correctness):
    - In munge_extrainfo_into_routerinfo(), check the return value of
      memchr(). This would have been a serious issue if we ever passed
      it a non-extrainfo. Fixes bug 8791; bugfix on 0.2.0.6-alpha. Patch
      from Arlo Breault.
    - On the chance that somebody manages to build Tor on a
      platform where time_t is unsigned, correct the way that
      microdesc_add_to_cache() handles negative time arguments.
      Fixes bug 8042; bugfix on 0.2.3.1-alpha.
    - Fix various instances of undefined behavior in channeltls.c,
      tor_memmem(), and eventdns.c that would cause us to construct
      pointers to memory outside an allocated object. (These invalid
      pointers were not accessed, but C does not even allow them to
      exist.) Fixes bug 10363; bugfixes on 0.1.1.1-alpha, 0.1.2.1-alpha,
      0.2.0.10-alpha, and 0.2.3.6-alpha. Reported by "bobnomnom".
    - Use the AddressSanitizer and Ubsan sanitizers (in clang-3.4) to
      fix some miscellaneous errors in our tests and codebase. Fixes bug
      11232. Bugfixes on versions back as far as 0.2.1.11-alpha.
    - Always check return values for unlink, munmap, UnmapViewOfFile;
      check strftime return values more often. In some cases all we can
      do is report a warning, but this may help prevent deeper bugs from
      going unnoticed. Closes ticket 8787; bugfixes on many, many tor
      versions.
    - Fix numerous warnings from the clang "scan-build" static analyzer.
      Some of these are programming style issues; some of them are false
      positives that indicated awkward code; some are undefined behavior
      cases related to constructing (but not using) invalid pointers;
      some are assumptions about API behavior; some are (harmlessly)
      logging sizeof(ptr) bytes from a token when sizeof(*ptr) would be
      correct; and one or two are genuine bugs that weren't reachable
      from the rest of the program. Fixes bug 8793; bugfixes on many,
      many tor versions.

  o Minor bugfixes (node selection):
    - If ExcludeNodes is set, consider non-excluded hidden service
      directory servers before excluded ones. Do not consider excluded
      hidden service directory servers at all if StrictNodes is
      set. (Previously, we would sometimes decide to connect to those
      servers, and then realize before we initiated a connection that
      we had excluded them.) Fixes bug 10722; bugfix on 0.2.0.10-alpha.
      Reported by "mr-4".
    - If we set the ExitNodes option but it doesn't include any nodes
      that have the Exit flag, we would choose not to bootstrap. Now we
      bootstrap so long as ExitNodes includes nodes which can exit to
      some port. Fixes bug 10543; bugfix on 0.2.4.10-alpha.

  o Minor bugfixes (performance):
    - Avoid a bug where every successful connection made us recompute
      the flag telling us whether we have sufficient information to
      build circuits. Previously, we would forget our cached value
      whenever we successfully opened a channel (or marked a router as
      running or not running for any other reason), regardless of
      whether we had previously believed the router to be running. This
      forced us to run an expensive update operation far too often.
      Fixes bug 12170; bugfix on 0.1.2.1-alpha.
    - Avoid using tor_memeq() for checking relay cell integrity. This
      removes a possible performance bottleneck. Fixes part of bug
      12169; bugfix on 0.2.1.31.

  o Minor bugfixes (platform-specific):
    - When dumping a malformed directory object to disk, save it in
      binary mode on Windows, not text mode. Fixes bug 11342; bugfix on
      0.2.2.1-alpha.
    - Don't report failures from make_socket_reuseable() on incoming
      sockets on OSX: this can happen when incoming connections close
      early. Fixes bug 10081.

  o Minor bugfixes (pluggable transports):
    - Avoid another 60-second delay when starting Tor in a pluggable-
      transport-using configuration when we already have cached
      descriptors for our bridges. Fixes bug 11965; bugfix
      on 0.2.3.6-alpha.

  o Minor bugfixes (protocol correctness):
    - When receiving a VERSIONS cell with an odd number of bytes, close
      the connection immediately since the cell is malformed. Fixes bug
      10365; bugfix on 0.2.0.10-alpha. Spotted by "bobnomnom"; fix by
      "rl1987".

  o Minor bugfixes (relay, other):
    - We now drop CREATE cells for already-existent circuit IDs and for
      zero-valued circuit IDs, regardless of other factors that might
      otherwise have called for DESTROY cells. Fixes bug 12191; bugfix
      on 0.0.8pre1.
    - When rejecting DATA cells for stream_id zero, still count them
      against the circuit's deliver window so that we don't fail to send
      a SENDME. Fixes bug 11246; bugfix on 0.2.4.10-alpha.

  o Minor bugfixes (relay, threading):
    - Check return code on spawn_func() in cpuworker code, so that we
      don't think we've spawned a nonworking cpuworker and write junk to
      it forever. Fix related to bug 4345; bugfix on all released Tor
      versions. Found by "skruffy".
    - Use a pthread_attr to make sure that spawn_func() cannot return an
      error while at the same time launching a thread. Fix related to
      bug 4345; bugfix on all released Tor versions. Reported
      by "cypherpunks".

  o Minor bugfixes (relays and bridges):
    - Avoid crashing on a malformed resolv.conf file when running a
      relay using Libevent 1. Fixes bug 8788; bugfix on 0.1.1.23.
    - Non-exit relays no longer launch mock DNS requests to check for
      DNS hijacking. This has been unnecessary since 0.2.1.7-alpha, when
      non-exit relays stopped servicing DNS requests. Fixes bug 965;
      bugfix on 0.2.1.7-alpha. Patch from Matt Pagan.
    - Bridges now report complete directory request statistics. Related
      to bug 5824; bugfix on 0.2.2.1-alpha.
    - Bridges now never collect statistics that were designed for
      relays. Fixes bug 5824; bugfix on 0.2.3.8-alpha.

  o Minor bugfixes (testing):
    - Fix all valgrind warnings produced by the unit tests. There were
      over a thousand memory leak warnings previously, mostly produced
      by forgetting to free things in the unit test code. Fixes bug
      11618, bugfixes on many versions of Tor.

  o Minor bugfixes (tor-fw-helper):
    - Give a correct log message when tor-fw-helper fails to launch.
      (Previously, we would say something like "tor-fw-helper sent us a
      string we could not parse".) Fixes bug 9781; bugfix
      on 0.2.4.2-alpha.

  o Minor bugfixes (trivial memory leaks):
    - Fix a small memory leak when signing a directory object. Fixes bug
      11275; bugfix on 0.2.4.13-alpha.
    - Resolve some memory leaks found by coverity in the unit tests, on
      exit in tor-gencert, and on a failure to compute digests for our
      own keys when generating a v3 networkstatus vote. These leaks
      should never have affected anyone in practice.

  o Code simplification and refactoring:
    - Remove some old fallback code designed to keep Tor clients working
      in a network with only two working relays. Elsewhere in the code we
      have long since stopped supporting such networks, so there wasn't
      much point in keeping it around. Addresses ticket 9926.
    - Reject 0-length EXTEND2 cells more explicitly. Fixes bug 10536;
      bugfix on 0.2.4.8-alpha. Reported by "cypherpunks".
    - Extract the common duplicated code for creating a subdirectory
      of the data directory and writing to a file in it. Fixes ticket
      4282; patch from Peter Retzlaff.
    - Since OpenSSL 0.9.7, the i2d_*() functions support allocating output
      buffer. Avoid calling twice: i2d_RSAPublicKey(), i2d_DHparams(),
      i2d_X509(), and i2d_PublicKey(). Resolves ticket 5170.
    - Add a set of accessor functions for the circuit timeout data
      structure. Fixes ticket 6153; patch from "piet".
    - Clean up exit paths from connection_listener_new(). Closes ticket
      8789. Patch from Arlo Breault.
    - Since we rely on OpenSSL 0.9.8 now, we can use EVP_PKEY_cmp()
      and drop our own custom pkey_eq() implementation. Fixes bug 9043.
    - Use a doubly-linked list to implement the global circuit list.
      Resolves ticket 9108. Patch from Marek Majkowski.
    - Remove contrib/id_to_fp.c since it wasn't used anywhere.
    - Remove constants and tests for PKCS1 padding; it's insecure and
      shouldn't be used for anything new. Fixes bug 8792; patch
      from Arlo Breault.
    - Remove instances of strcpy() from the unit tests. They weren't
      hurting anything, since they were only in the unit tests, but it's
      embarassing to have strcpy() in the code at all, and some analysis
      tools don't like it. Fixes bug 8790; bugfix on 0.2.3.6-alpha and
      0.2.3.8-alpha. Patch from Arlo Breault.
    - Remove is_internal_IP() function. Resolves ticket 4645.
    - Remove unused function circuit_dump_by_chan from circuitlist.c.
      Closes issue 9107; patch from "marek".
    - Change our use of the ENUM_BF macro to avoid declarations that
      confuse Doxygen.
    - Get rid of router->address, since in all cases it was just the
      string representation of router->addr. Resolves ticket 5528.

  o Documentation:
    - Adjust the URLs in the README to refer to the new locations of
      several documents on the website. Fixes bug 12830. Patch from
      Matt Pagan.
    - Document 'reject6' and 'accept6' ExitPolicy entries. Resolves
      ticket 12878.
    - Update manpage to describe some of the files you can expect to
      find in Tor's DataDirectory. Addresses ticket 9839.
    - Clean up several option names in the manpage to match their real
      names, add the missing documentation for a couple of testing and
      directory authority options, remove the documentation for a
      V2-directory fetching option that no longer exists. Resolves
      ticket 11634.
    - Correct the documenation so that it lists the correct directory
      for the stats files. (They are in a subdirectory called "stats",
      not "status".)
    - In the manpage, move more authority-only options into the
      directory authority section so that operators of regular directory
      caches don't get confused.
    - Fix the layout of the SOCKSPort flags in the manpage. Fixes bug
      11061; bugfix on 0.2.4.7-alpha.
    - Resolve warnings from Doxygen.
    - Document in the manpage that "KBytes" may also be written as
      "kilobytes" or "KB", that "Kbits" may also be written as
      "kilobits", and so forth. Closes ticket 9222.
    - Document that the ClientOnly config option overrides ORPort.
      Our old explanation made ClientOnly sound as though it did
      nothing at all. Resolves bug 9059.
    - Explain that SocksPolicy, DirPolicy, and similar options don't
      take port arguments. Fixes the other part of ticket 11108.
    - Fix a comment about the rend_server_descriptor_t.protocols field
      to more accurately describe its range. Also, make that field
      unsigned, to more accurately reflect its usage. Fixes bug 9099;
      bugfix on 0.2.1.5-alpha.
    - Fix the manpage's description of HiddenServiceAuthorizeClient:
      the maximum client name length is 16, not 19. Fixes bug 11118;
      bugfix on 0.2.1.6-alpha.

  o Package cleanup:
    - The contrib directory has been sorted and tidied. Before, it was
      an unsorted dumping ground for useful and not-so-useful things.
      Now, it is divided based on functionality, and the items which
      seemed to be nonfunctional or useless have been removed. Resolves
      ticket 8966; based on patches from "rl1987".

  o Removed code and features:
    - Clients now reject any directory authority certificates lacking
      a dir-key-crosscert element. These have been included since
      0.2.1.9-alpha, so there's no real reason for them to be optional
      any longer. Completes proposal 157. Resolves ticket 10162.
    - Remove all code that existed to support the v2 directory system,
      since there are no longer any v2 directory authorities. Resolves
      ticket 10758.
    - Remove the HSAuthoritativeDir and AlternateHSAuthority torrc
      options, which were used for designating authorities as "Hidden
      service authorities". There has been no use of hidden service
      authorities since 0.2.2.1-alpha, when we stopped uploading or
      downloading v0 hidden service descriptors. Fixes bug 10881; also
      part of a fix for bug 10841.
    - Remove /tor/dbg-stability.txt URL that was meant to help debug WFU
      and MTBF calculations, but that nobody was using. Fixes bug 11742.
    - The TunnelDirConns and PreferTunnelledDirConns options no longer
      exist; tunneled directory connections have been available since
      0.1.2.5-alpha, and turning them off is not a good idea. This is a
      brute-force fix for 10849, where "TunnelDirConns 0" would break
      hidden services.
    - Remove all code for the long unused v1 directory protocol.
      Resolves ticket 11070.
    - Remove all remaining code related to version-0 hidden service
      descriptors: they have not been in use since 0.2.2.1-alpha. Fixes
      the rest of bug 10841.
    - Remove migration code from when we renamed the "cached-routers"
      file to "cached-descriptors" back in 0.2.0.8-alpha. This
      incidentally resolves ticket 6502 by cleaning up the related code
      a bit. Patch from Akshay Hebbar.

  o Test infrastructure:
    - Tor now builds each source file in two modes: a mode that avoids
      exposing identifiers needlessly, and another mode that exposes
      more identifiers for testing. This lets the compiler do better at
      optimizing the production code, while enabling us to take more
      radical measures to let the unit tests test things.
    - The production builds no longer include functions used only in
      the unit tests; all functions exposed from a module only for
      unit-testing are now static in production builds.
    - Add an --enable-coverage configuration option to make the unit
      tests (and a new src/or/tor-cov target) to build with gcov test
      coverage support.
    - Update to the latest version of tinytest.
    - Improve the tinytest implementation of string operation tests so
      that comparisons with NULL strings no longer crash the tests; they
      now just fail, normally. Fixes bug 9004; bugfix on 0.2.2.4-alpha.
    - New macros in test.h to simplify writing mock-functions for unit
      tests. Part of ticket 11507. Patch from Dana Koch.
    - We now have rudimentary function mocking support that our unit
      tests can use to test functions in isolation. Function mocking
      lets the tests temporarily replace a function's dependencies with
      stub functions, so that the tests can check the function without
      invoking the other functions it calls.

  o Testing:
    - Complete tests for the status.c module. Resolves ticket 11507.
      Patch from Dana Koch.
    - Add more unit tests for the <circid,channel>->circuit map, and
      the destroy-cell-tracking code to fix bug 7912.
    - Unit tests for failing cases of the TAP onion handshake.
    - More unit tests for address-manipulation functions.

  o Distribution (systemd):
    - Include a tor.service file in contrib/dist for use with systemd.
      Some distributions will be able to use this file unmodified;
      others will need to tweak it, or write their own. Patch from Jamie
      Nguyen; resolves ticket 8368.
    - Verify configuration file via ExecStartPre in the systemd unit
      file. Patch from intrigeri; resolves ticket 12730.
    - Explicitly disable RunAsDaemon in the systemd unit file. Our
      current systemd unit uses "Type = simple", so systemd does not
      expect tor to fork. If the user has "RunAsDaemon 1" in their
      torrc, then things won't work as expected. This is e.g. the case
      on Debian (and derivatives), since there we pass "--defaults-torrc
      /usr/share/tor/tor-service-defaults-torrc" (that contains
      "RunAsDaemon 1") by default. Patch by intrigeri; resolves
      ticket 12731.


Changes in version 0.2.4.25 - 2014-10-20
  Tor 0.2.4.25 disables SSL3 in response to the recent "POODLE" attack
  (even though POODLE does not affect Tor). It also works around a crash
  bug caused by some operating systems' response to the "POODLE" attack
  (which does affect Tor).

  o Major security fixes (also in 0.2.5.9-rc):
    - Disable support for SSLv3. All versions of OpenSSL in use with Tor
      today support TLS 1.0 or later, so we can safely turn off support
      for this old (and insecure) protocol. Fixes bug 13426.

  o Major bugfixes (openssl bug workaround, also in 0.2.5.9-rc):
    - Avoid crashing when using OpenSSL version 0.9.8zc, 1.0.0o, or
      1.0.1j, built with the 'no-ssl3' configuration option. Fixes bug
      13471. This is a workaround for an OpenSSL bug.


Changes in version 0.2.4.24 - 2014-09-22
  Tor 0.2.4.24 fixes a bug that affects consistency and speed when
  connecting to hidden services, and it updates the location of one of
  the directory authorities.

  o Major bugfixes:
    - Clients now send the correct address for their chosen rendezvous
      point when trying to access a hidden service. They used to send
      the wrong address, which would still work some of the time because
      they also sent the identity digest of the rendezvous point, and if
      the hidden service happened to try connecting to the rendezvous
      point from a relay that already had a connection open to it,
      the relay would reuse that connection. Now connections to hidden
      services should be more robust and faster. Also, this bug meant
      that clients were leaking to the hidden service whether they were
      on a little-endian (common) or big-endian (rare) system, which for
      some users might have reduced their anonymity. Fixes bug 13151;
      bugfix on 0.2.1.5-alpha.

  o Directory authority changes:
    - Change IP address for gabelmoo (v3 directory authority).

  o Minor features (geoip):
    - Update geoip and geoip6 to the August 7 2014 Maxmind GeoLite2
      Country database.


Changes in version 0.2.4.23 - 2014-07-28
  Tor 0.2.4.23 brings us a big step closer to slowing down the risk from
  guard rotation, and also backports several important fixes from the
  Tor 0.2.5 alpha release series.

  o Major features:
    - Clients now look at the "usecreatefast" consensus parameter to
      decide whether to use CREATE_FAST or CREATE cells for the first hop
      of their circuit. This approach can improve security on connections
      where Tor's circuit handshake is stronger than the available TLS
      connection security levels, but the tradeoff is more computational
      load on guard relays. Implements proposal 221. Resolves ticket 9386.
    - Make the number of entry guards configurable via a new
      NumEntryGuards consensus parameter, and the number of directory
      guards configurable via a new NumDirectoryGuards consensus
      parameter. Implements ticket 12688.

  o Major bugfixes:
    - Fix a bug in the bounds-checking in the 32-bit curve25519-donna
      implementation that caused incorrect results on 32-bit
      implementations when certain malformed inputs were used along with
      a small class of private ntor keys. This bug does not currently
      appear to allow an attacker to learn private keys or impersonate a
      Tor server, but it could provide a means to distinguish 32-bit Tor
      implementations from 64-bit Tor implementations. Fixes bug 12694;
      bugfix on 0.2.4.8-alpha. Bug found by Robert Ransom; fix from
      Adam Langley.

  o Minor bugfixes:
    - Warn and drop the circuit if we receive an inbound 'relay early'
      cell. Those used to be normal to receive on hidden service circuits
      due to bug 1038, but the buggy Tor versions are long gone from
      the network so we can afford to resume watching for them. Resolves
      the rest of bug 1038; bugfix on 0.2.1.19.
    - Correct a confusing error message when trying to extend a circuit
      via the control protocol but we don't know a descriptor or
      microdescriptor for one of the specified relays. Fixes bug 12718;
      bugfix on 0.2.3.1-alpha.
    - Avoid an illegal read from stack when initializing the TLS
      module using a version of OpenSSL without all of the ciphers
      used by the v2 link handshake. Fixes bug 12227; bugfix on
      0.2.4.8-alpha.  Found by "starlight".

  o Minor features:
    - Update geoip and geoip6 to the July 10 2014 Maxmind GeoLite2
      Country database.


Changes in version 0.2.4.22 - 2014-05-16
  Tor 0.2.4.22 backports numerous high-priority fixes from the Tor 0.2.5
  alpha release series. These include blocking all authority signing
  keys that may have been affected by the OpenSSL "heartbleed" bug,
  choosing a far more secure set of TLS ciphersuites by default, closing
  a couple of memory leaks that could be used to run a target relay out
  of RAM, and several others.

  o Major features (security, backport from 0.2.5.4-alpha):
    - Block authority signing keys that were used on authorities
      vulnerable to the "heartbleed" bug in OpenSSL (CVE-2014-0160). (We
      don't have any evidence that these keys _were_ compromised; we're
      doing this to be prudent.) Resolves ticket 11464.

  o Major bugfixes (security, OOM):
    - Fix a memory leak that could occur if a microdescriptor parse
      fails during the tokenizing step. This bug could enable a memory
      exhaustion attack by directory servers. Fixes bug 11649; bugfix
      on 0.2.2.6-alpha.

  o Major bugfixes (TLS cipher selection, backport from 0.2.5.4-alpha):
    - The relay ciphersuite list is now generated automatically based on
      uniform criteria, and includes all OpenSSL ciphersuites with
      acceptable strength and forward secrecy. Previously, we had left
      some perfectly fine ciphersuites unsupported due to omission or
      typo. Resolves bugs 11513, 11492, 11498, 11499. Bugs reported by
      'cypherpunks'. Bugfix on 0.2.4.8-alpha.
    - Relays now trust themselves to have a better view than clients of
      which TLS ciphersuites are better than others. (Thanks to bug
      11513, the relay list is now well-considered, whereas the client
      list has been chosen mainly for anti-fingerprinting purposes.)
      Relays prefer: AES over 3DES; then ECDHE over DHE; then GCM over
      CBC; then SHA384 over SHA256 over SHA1; and last, AES256 over
      AES128. Resolves ticket 11528.
    - Clients now try to advertise the same list of ciphersuites as
      Firefox 28. This change enables selection of (fast) GCM
      ciphersuites, disables some strange old ciphers, and stops
      advertising the ECDH (not to be confused with ECDHE) ciphersuites.
      Resolves ticket 11438.

  o Minor bugfixes (configuration, security):
    - When running a hidden service, do not allow TunneledDirConns 0:
      trying to set that option together with a hidden service would
      otherwise prevent the hidden service from running, and also make
      it publish its descriptors directly over HTTP. Fixes bug 10849;
      bugfix on 0.2.1.1-alpha.

  o Minor bugfixes (controller, backport from 0.2.5.4-alpha):
    - Avoid sending a garbage value to the controller when a circuit is
      cannibalized. Fixes bug 11519; bugfix on 0.2.3.11-alpha.

  o Minor bugfixes (exit relay, backport from 0.2.5.4-alpha):
    - Stop leaking memory when we successfully resolve a PTR record.
      Fixes bug 11437; bugfix on 0.2.4.7-alpha.

  o Minor bugfixes (bridge client, backport from 0.2.5.4-alpha):
    - Avoid 60-second delays in the bootstrapping process when Tor is
      launching for a second time while using bridges. Fixes bug 9229;
      bugfix on 0.2.0.3-alpha.

  o Minor bugfixes (relays and bridges, backport from 0.2.5.4-alpha):
    - Give the correct URL in the warning message when trying to run a
      relay on an ancient version of Windows. Fixes bug 9393.

  o Minor bugfixes (compilation):
    - Fix a compilation error when compiling with --disable-curve25519.
      Fixes bug 9700; bugfix on 0.2.4.17-rc.

  o Minor bugfixes:
    - Downgrade the warning severity for the the "md was still
      referenced 1 node(s)" warning. Tor 0.2.5.4-alpha has better code
      for trying to diagnose this bug, and the current warning in
      earlier versions of tor achieves nothing useful. Addresses warning
      from bug 7164.

  o Minor features (log verbosity, backport from 0.2.5.4-alpha):
    - When we run out of usable circuit IDs on a channel, log only one
      warning for the whole channel, and describe how many circuits
      there were on the channel. Fixes part of ticket 11553.

  o Minor features (security, backport from 0.2.5.4-alpha):
    - Decrease the lower limit of MaxMemInCellQueues to 256 MBytes (but
      leave the default at 8GBytes), to better support Raspberry Pi
      users. Fixes bug 9686; bugfix on 0.2.4.14-alpha.

  o Documentation (backport from 0.2.5.4-alpha):
    - Correctly document that we search for a system torrc file before
      looking in ~/.torrc. Fixes documentation side of 9213; bugfix on
      0.2.3.18-rc.


Changes in version 0.2.4.21 - 2014-02-28
  Tor 0.2.4.21 further improves security against potential adversaries who
  find breaking 1024-bit crypto doable, and backports several stability
  and robustness patches from the 0.2.5 branch.

  o Major features (client security):
    - When we choose a path for a 3-hop circuit, make sure it contains
      at least one relay that supports the NTor circuit extension
      handshake. Otherwise, there is a chance that we're building
      a circuit that's worth attacking by an adversary who finds
      breaking 1024-bit crypto doable, and that chance changes the game
      theory. Implements ticket 9777.

  o Major bugfixes:
    - Do not treat streams that fail with reason
      END_STREAM_REASON_INTERNAL as indicating a definite circuit failure,
      since it could also indicate an ENETUNREACH connection error. Fixes
      part of bug 10777; bugfix on 0.2.4.8-alpha.

  o Code simplification and refactoring:
    - Remove data structures which were introduced to implement the
      CellStatistics option: they are now redundant with the new timestamp
      field in the regular packed_cell_t data structure, which we did
      in 0.2.4.18-rc in order to resolve bug 9093. Resolves ticket 10870.

  o Minor features:
    - Always clear OpenSSL bignums before freeing them -- even bignums
      that don't contain secrets. Resolves ticket 10793. Patch by
      Florent Daigniere.
    - Build without warnings under clang 3.4. (We have some macros that
      define static functions only some of which will get used later in
      the module. Starting with clang 3.4, these give a warning unless the
      unused attribute is set on them.) Resolves ticket 10904.
    - Update geoip and geoip6 files to the February 7 2014 Maxmind
      GeoLite2 Country database.

  o Minor bugfixes:
    - Set the listen() backlog limit to the largest actually supported
      on the system, not to the value in a header file. Fixes bug 9716;
      bugfix on every released Tor.
    - Treat ENETUNREACH, EACCES, and EPERM connection failures at an
      exit node as a NOROUTE error, not an INTERNAL error, since they
      can apparently happen when trying to connect to the wrong sort
      of netblocks. Fixes part of bug 10777; bugfix on 0.1.0.1-rc.
    - Fix build warnings about missing "a2x" comment when building the
      manpages from scratch on OpenBSD; OpenBSD calls it "a2x.py".
      Fixes bug 10929; bugfix on 0.2.2.9-alpha. Patch from Dana Koch.
    - Avoid a segfault on SIGUSR1, where we had freed a connection but did
      not entirely remove it from the connection lists. Fixes bug 9602;
      bugfix on 0.2.4.4-alpha.
    - Fix a segmentation fault in our benchmark code when running with
      Fedora's OpenSSL package, or any other OpenSSL that provides
      ECDH but not P224. Fixes bug 10835; bugfix on 0.2.4.8-alpha.
    - Turn "circuit handshake stats since last time" log messages into a
      heartbeat message. Fixes bug 10485; bugfix on 0.2.4.17-rc.

  o Documentation fixes:
    - Document that all but one DirPort entry must have the NoAdvertise
      flag set. Fixes bug 10470; bugfix on 0.2.3.3-alpha / 0.2.3.16-alpha.


Changes in version 0.2.4.20 - 2013-12-22
  Tor 0.2.4.20 fixes potentially poor random number generation for users
  who 1) use OpenSSL 1.0.0 or later, 2) set "HardwareAccel 1" in their
  torrc file, 3) have "Sandy Bridge" or "Ivy Bridge" Intel processors,
  and 4) have no state file in their DataDirectory (as would happen on
  first start). Users who generated relay or hidden service identity
  keys in such a situation should discard them and generate new ones.

  This release also fixes a logic error that caused Tor clients to build
  many more preemptive circuits than they actually need.

  o Major bugfixes:
    - Do not allow OpenSSL engines to replace the PRNG, even when
      HardwareAccel is set. The only default builtin PRNG engine uses
      the Intel RDRAND instruction to replace the entire PRNG, and
      ignores all attempts to seed it with more entropy. That's
      cryptographically stupid: the right response to a new alleged
      entropy source is never to discard all previously used entropy
      sources. Fixes bug 10402; works around behavior introduced in
      OpenSSL 1.0.0. Diagnosis and investigation thanks to "coderman"
      and "rl1987".
    - Fix assertion failure when AutomapHostsOnResolve yields an IPv6
      address. Fixes bug 10465; bugfix on 0.2.4.7-alpha.
    - Avoid launching spurious extra circuits when a stream is pending.
      This fixes a bug where any circuit that _wasn't_ unusable for new
      streams would be treated as if it were, causing extra circuits to
      be launched. Fixes bug 10456; bugfix on 0.2.4.12-alpha.

  o Minor bugfixes:
    - Avoid a crash bug when starting with a corrupted microdescriptor
      cache file. Fixes bug 10406; bugfix on 0.2.2.6-alpha.
    - If we fail to dump a previously cached microdescriptor to disk, avoid
      freeing duplicate data later on. Fixes bug 10423; bugfix on
      0.2.4.13-alpha. Spotted by "bobnomnom".


Changes in version 0.2.4.19 - 2013-12-11
  The Tor 0.2.4 release series is dedicated to the memory of Aaron Swartz
  (1986-2013). Aaron worked on diverse projects including helping to guide
  Creative Commons, playing a key role in stopping SOPA/PIPA, bringing
  transparency to the U.S government's PACER documents, and contributing
  design and development for Tor and Tor2Web. Aaron was one of the latest
  martyrs in our collective fight for civil liberties and human rights,
  and his death is all the more painful because he was one of us.

  Tor 0.2.4.19, the first stable release in the 0.2.4 branch, features
  a new circuit handshake and link encryption that use ECC to provide
  better security and efficiency; makes relays better manage circuit
  creation requests; uses "directory guards" to reduce client enumeration
  risks; makes bridges collect and report statistics about the pluggable
  transports they support; cleans up and improves our geoip database;
  gets much closer to IPv6 support for clients, bridges, and relays; makes
  directory authorities use measured bandwidths rather than advertised
  ones when computing flags and thresholds; disables client-side DNS
  caching to reduce tracking risks; and fixes a big bug in bridge
  reachability testing. This release introduces two new design
  abstractions in the code: a new "channel" abstraction between circuits
  and or_connections to allow for implementing alternate relay-to-relay
  transports, and a new "circuitmux" abstraction storing the queue of
  circuits for a channel. The release also includes many stability,
  security, and privacy fixes.

  o Major features (new circuit handshake):
    - Tor now supports a new circuit extension handshake designed by Ian
      Goldberg, Douglas Stebila, and Berkant Ustaoglu. Our original
      circuit extension handshake, later called "TAP", was a bit slow
      (especially on the relay side), had a fragile security proof, and
      used weaker keys than we'd now prefer. The new circuit handshake
      uses Dan Bernstein's "curve25519" elliptic-curve Diffie-Hellman
      function, making it significantly more secure than the older
      handshake, and significantly faster. Tor can use one of two built-in
      pure-C curve25519-donna implementations by Adam Langley, or it
      can link against the "nacl" library for a tuned version if present.

      The built-in version is very fast for 64-bit systems when building
      with GCC. The built-in 32-bit version is still faster than the
      old TAP protocol, but using libnacl is better on most such hosts.

      Implements proposal 216; closes ticket 7202.

  o Major features (better link encryption):
    - Relays can now enable the ECDHE TLS ciphersuites when available
      and appropriate. These ciphersuites let us negotiate forward-secure
      TLS secret keys more safely and more efficiently than with our
      previous use of Diffie-Hellman modulo a 1024-bit prime. By default,
      public relays prefer the (faster) P224 group, and bridges prefer
      the (more common) P256 group; you can override this with the
      TLSECGroup option.

      This feature requires clients running 0.2.3.17-beta or later,
      and requires both sides to be running OpenSSL 1.0.0 or later
      with ECC support. OpenSSL 1.0.1, with the compile-time option
      "enable-ec_nistp_64_gcc_128", is highly recommended.

      Implements the relay side of proposal 198; closes ticket 7200.

    - Re-enable TLS 1.1 and 1.2 when built with OpenSSL 1.0.1e or later.
      Resolves ticket 6055. (OpenSSL before 1.0.1 didn't have TLS 1.1 or
      1.2, and OpenSSL from 1.0.1 through 1.0.1d had bugs that prevented
      renegotiation from working with TLS 1.1 or 1.2, so we had disabled
      them to solve bug 6033.)

  o Major features (relay performance):
    - Instead of limiting the number of queued onionskins (aka circuit
      create requests) to a fixed, hard-to-configure number, we limit
      the size of the queue based on how many we expect to be able to
      process in a given amount of time. We estimate the time it will
      take to process an onionskin based on average processing time
      of previous onionskins. Closes ticket 7291. You'll never have to
      configure MaxOnionsPending again.
    - Relays process the new "NTor" circuit-level handshake requests
      with higher priority than the old "TAP" circuit-level handshake
      requests. We still process some TAP requests to not totally starve
      0.2.3 clients when NTor becomes popular. A new consensus parameter
      "NumNTorsPerTAP" lets us tune the balance later if we need to.
      Implements ticket 9574.

  o Major features (client bootstrapping resilience):
    - Add a new "FallbackDir" torrc option to use when we can't use
      a directory mirror from the consensus (either because we lack a
      consensus, or because they're all down). Currently, all authorities
      are fallbacks by default, and there are no other default fallbacks,
      but that will change. This option will allow us to give clients a
      longer list of servers to try to get a consensus from when first
      connecting to the Tor network, and thereby reduce load on the
      directory authorities. Implements proposal 206, "Preconfigured
      directory sources for bootstrapping". We also removed the old
      "FallbackNetworkstatus" option, since we never got it working well
      enough to use it. Closes bug 572.
    - If we have no circuits open, use a relaxed timeout (the
      95th-percentile cutoff) until a circuit succeeds. This heuristic
      should allow Tor to succeed at building circuits even when the
      network connection drastically changes. Should help with bug 3443.

  o Major features (use of guards):
    - Support directory guards (proposal 207): when possible, clients now
      use their entry guards for non-anonymous directory requests. This
      can help prevent client enumeration. Note that this behavior only
      works when we have a usable consensus directory, and when options
      about what to download are more or less standard. In the future we
      should re-bootstrap from our guards, rather than re-bootstrapping
      from the preconfigured list of directory sources that ships with
      Tor. Resolves ticket 6526.
    - Raise the default time that a client keeps an entry guard from
      "1-2 months" to "2-3 months", as suggested by Tariq Elahi's WPES
      2012 paper. (We would make it even longer, but we need better client
      load balancing first.) Also, make the guard lifetime controllable
      via a new GuardLifetime torrc option and a GuardLifetime consensus
      parameter. Start of a fix for bug 8240; bugfix on 0.1.1.11-alpha.

  o Major features (bridges with pluggable transports):
    - Bridges now report the pluggable transports they support to the
      bridge authority, so it can pass the supported transports on to
      bridgedb and/or eventually do reachability testing. Implements
      ticket 3589.
    - Automatically forward the TCP ports of pluggable transport
      proxies using tor-fw-helper if PortForwarding is enabled. Implements
      ticket 4567.

  o Major features (geoip database):
    - Maxmind began labelling Tor relays as being in country "A1",
      which breaks by-country node selection inside Tor. Now we use a
      script to replace "A1" ("Anonymous Proxy") entries in our geoip
      file with real country codes. This script fixes about 90% of "A1"
      entries automatically and uses manual country code assignments to
      fix the remaining 10%. See src/config/README.geoip for details.
      Fixes bug 6266.
    - Add GeoIP database for IPv6 addresses. The new config option
      is GeoIPv6File.
    - Update to the October 2 2013 Maxmind GeoLite Country database.

  o Major features (IPv6):
    - Clients who set "ClientUseIPv6 1" may connect to entry nodes over
      IPv6. Set "ClientPreferIPv6ORPort 1" to make this even more likely
      to happen. Implements ticket 5535.
    - All kind of relays, not just bridges, can now advertise an IPv6
      OR port. Implements ticket 6362.
    - Relays can now exit to IPv6 addresses: make sure that you have IPv6
      connectivity, then set the IPv6Exit flag to 1. Also make sure your
      exit policy reads as you would like: the address * applies to all
      address families, whereas *4 is IPv4 address only, and *6 is IPv6
      addresses only. On the client side, you'll need to wait for enough
      exits to support IPv6, apply the "IPv6Traffic" flag to a SocksPort,
      and use Socks5. Closes ticket 5547, implements proposal 117 as
      revised in proposal 208.
    - Bridge authorities now accept IPv6 bridge addresses and include
      them in network status documents. Implements ticket 5534.
    - Directory authorities vote on IPv6 OR ports. Implements ticket 6363.

  o Major features (directory authorities):
    - Directory authorities now prefer using measured bandwidths to
      advertised ones when computing flags and thresholds. Resolves
      ticket 8273.
    - Directory authorities that vote measured bandwidths about more
      than a threshold number of relays now treat relays with
      unmeasured bandwidths as having bandwidth 0 when computing their
      flags. Resolves ticket 8435.
    - Directory authorities now support a new consensus method (17)
      where they cap the published bandwidth of relays for which
      insufficient bandwidth measurements exist. Fixes part of bug 2286.
    - Directory authorities that set "DisableV2DirectoryInfo_ 1" no longer
      serve any v2 directory information. Now we can test disabling the
      old deprecated v2 directory format, and see whether doing so has
      any effect on network load. Begins to fix bug 6783.

  o Major features (build and portability):
    - Switch to a nonrecursive Makefile structure. Now instead of each
      Makefile.am invoking other Makefile.am's, there is a master
      Makefile.am that includes the others. This change makes our build
      process slightly more maintainable, and improves parallelism for
      building with make -j. Original patch by Stewart Smith; various
      fixes by Jim Meyering.
    - Where available, we now use automake's "silent" make rules by
      default, so that warnings are easier to spot. You can get the old
      behavior with "make V=1". Patch by Stewart Smith for ticket 6522.
    - Resume building correctly with MSVC and Makefile.nmake. This patch
      resolves numerous bugs and fixes reported by ultramage, including
      7305, 7308, 7309, 7310, 7312, 7313, 7315, 7316, and 7669.

  o Security features:
    - Switch to a completely time-invariant approach for picking nodes
      weighted by bandwidth. Our old approach would run through the
      part of the loop after it had made its choice slightly slower
      than it ran through the part of the loop before it had made its
      choice. Addresses ticket 6538.
    - Disable the use of Guard nodes when in Tor2WebMode. Guard usage
      by tor2web clients allows hidden services to identify tor2web
      clients through their repeated selection of the same rendezvous
      and introduction point circuit endpoints (their guards). Resolves
      ticket 6888.

  o Major bugfixes (relay denial of service):
    - When we have too much memory queued in circuits (according to a new
      MaxMemInCellQueues option), close the circuits that have the oldest
      queued cells, on the theory that those are most responsible for
      us running low on memory. This prevents us from running out of
      memory as a relay if circuits fill up faster than they can be
      drained. Fixes bugs 9063 and 9093; bugfix on the 54th commit of
      Tor. This bug is a further fix beyond bug 6252, whose fix was
      merged into 0.2.3.21-rc.
    - Reject bogus create and relay cells with 0 circuit ID or 0 stream
      ID: these could be used to create unexpected streams and circuits
      which would count as "present" to some parts of Tor but "absent"
      to others, leading to zombie circuits and streams or to a bandwidth
      denial-of-service. Fixes bug 7889; bugfix on every released version
      of Tor. Reported by "oftc_must_be_destroyed".
    - Avoid a bug where our response to TLS renegotiation under certain
      network conditions could lead to a busy-loop, with 100% CPU
      consumption. Fixes bug 5650; bugfix on 0.2.0.16-alpha.

  o Major bugfixes (asserts, crashes, leaks):
    - Prevent the get_freelists() function from running off the end of
      the list of freelists if it somehow gets an unrecognized
      allocation. Fixes bug 8844; bugfix on 0.2.0.16-alpha. Reported by
      eugenis.
    - Avoid a memory leak where we would leak a consensus body when we
      find that a consensus which we couldn't previously verify due to
      missing certificates is now verifiable. Fixes bug 8719; bugfix
      on 0.2.0.10-alpha.
    - If we are unable to save a microdescriptor to the journal, do not
      drop it from memory and then reattempt downloading it. Fixes bug
      9645; bugfix on 0.2.2.6-alpha.
    - Fix an assertion failure that would occur when disabling the
      ORPort setting on a running Tor process while accounting was
      enabled. Fixes bug 6979; bugfix on 0.2.2.18-alpha.
    - Avoid an assertion failure on OpenBSD (and perhaps other BSDs)
      when an exit connection with optimistic data succeeds immediately
      rather than returning EINPROGRESS. Fixes bug 9017; bugfix on
      0.2.3.1-alpha.
    - Fix a memory leak that would occur whenever a configuration
      option changed. Fixes bug 8718; bugfix on 0.2.3.3-alpha.

  o Major bugfixes (relay rate limiting):
    - When a TLS write is partially successful but incomplete, remember
      that the flushed part has been flushed, and notice that bytes were
      actually written. Reported and fixed pseudonymously. Fixes bug 7708;
      bugfix on Tor 0.1.0.5-rc.
    - Raise the default BandwidthRate/BandwidthBurst values from 5MB/10MB
      to 1GB/1GB. The previous defaults were intended to be "basically
      infinite", but it turns out they're now limiting our 100mbit+
      relays and bridges. Fixes bug 6605; bugfix on 0.2.0.10-alpha (the
      last time we raised it).
    - No longer stop reading or writing on cpuworker connections when
      our rate limiting buckets go empty. Now we should handle circuit
      handshake requests more promptly. Resolves bug 9731.

  o Major bugfixes (client-side privacy):
    - When we mark a circuit as unusable for new circuits, have it
      continue to be unusable for new circuits even if MaxCircuitDirtiness
      is increased too much at the wrong time, or the system clock jumps
      backwards. Fixes bug 6174; bugfix on 0.0.2pre26.
    - If ClientDNSRejectInternalAddresses ("do not believe DNS queries
      which have resolved to internal addresses") is set, apply that
      rule to IPv6 as well. Fixes bug 8475; bugfix on 0.2.0.7-alpha.
    - When an exit relay rejects a stream with reason "exit policy", but
      we only know an exit policy summary (e.g. from the microdesc
      consensus) for it, do not mark the relay as useless for all exiting.
      Instead, mark just the circuit as unsuitable for that particular
      address. Fixes part of bug 7582; bugfix on 0.2.3.2-alpha.

  o Major bugfixes (stream isolation):
    - Allow applications to get proper stream isolation with
      IsolateSOCKSAuth. Many SOCKS5 clients that want to offer
      username/password authentication also offer "no authentication". Tor
      had previously preferred "no authentication", so the applications
      never actually sent Tor their auth details. Now Tor selects
      username/password authentication if it's offered. You can disable
      this behavior on a per-SOCKSPort basis via PreferSOCKSNoAuth. Fixes
      bug 8117; bugfix on 0.2.3.3-alpha.
    - Follow the socks5 protocol when offering username/password
      authentication. The fix for bug 8117 exposed this bug, and it
      turns out real-world applications like Pidgin do care. Bugfix on
      0.2.3.2-alpha; fixes bug 8879.

  o Major bugfixes (client circuit building):
    - Alter circuit build timeout measurement to start at the point
      where we begin the CREATE/CREATE_FAST step (as opposed to circuit
      initialization). This should make our timeout measurements more
      uniform. Previously, we were sometimes including ORconn setup time
      in our circuit build time measurements. Should resolve bug 3443.
    - If the circuit build timeout logic is disabled (via the consensus,
      or because we are an authority), then don't build testing circuits.
      Fixes bug 9657; bugfix on 0.2.2.14-alpha.

  o Major bugfixes (client-side DNS):
    - Turn off the client-side DNS cache by default. Updating and using
      the DNS cache is now configurable on a per-client-port
      level. SOCKSPort, DNSPort, etc lines may now contain
      {No,}Cache{IPv4,IPv6,}DNS lines to indicate that we shouldn't
      cache these types of DNS answers when we receive them from an
      exit node in response to an application request on this port, and
      {No,}UseCached{IPv4,IPv6,DNS} lines to indicate that if we have
      cached DNS answers of these types, we shouldn't use them. It's
      potentially risky to use cached DNS answers at the client, since
      doing so can indicate to one exit what answers we've gotten
      for DNS lookups in the past. With IPv6, this becomes especially
      problematic. Using cached DNS answers for requests on the same
      circuit would present less linkability risk, since all traffic
      on a circuit is already linkable, but it would also provide
      little performance benefit: the exit node caches DNS replies
      too. Implements a simplified version of Proposal 205. Implements
      ticket 7570.

  o Major bugfixes (hidden service privacy):
    - Limit hidden service descriptors to at most ten introduction
      points, to slow one kind of guard enumeration. Fixes bug 9002;
      bugfix on 0.1.1.11-alpha.

  o Major bugfixes (directory fetching):
    - If the time to download the next old-style networkstatus is in
      the future, do not decline to consider whether to download the
      next microdescriptor networkstatus. Fixes bug 9564; bugfix on
      0.2.3.14-alpha.
    - We used to always request authority certificates by identity digest,
      meaning we'd get the newest one even when we wanted one with a
      different signing key. Then we would complain about being given
      a certificate we already had, and never get the one we really
      wanted. Now we use the "fp-sk/" resource as well as the "fp/"
      resource to request the one we want. Fixes bug 5595; bugfix on
      0.2.0.8-alpha.

  o Major bugfixes (bridge reachability):
    - Bridges now send AUTH_CHALLENGE cells during their v3 handshakes;
      previously they did not, which prevented them from receiving
      successful connections from relays for self-test or bandwidth
      testing. Also, when a relay is extending a circuit to a bridge,
      it needs to send a NETINFO cell, even when the bridge hasn't sent
      an AUTH_CHALLENGE cell. Fixes bug 9546; bugfix on 0.2.3.6-alpha.

  o Major bugfixes (control interface):
    - When receiving a new configuration file via the control port's
      LOADCONF command, do not treat the defaults file as absent.
      Fixes bug 9122; bugfix on 0.2.3.9-alpha.

  o Major bugfixes (directory authorities):
    - Stop marking every relay as having been down for one hour every
      time we restart a directory authority. These artificial downtimes
      were messing with our Stable and Guard flag calculations. Fixes
      bug 8218 (introduced by the fix for 1035). Bugfix on 0.2.2.23-alpha.
    - When computing directory thresholds, ignore any rejected-as-sybil
      nodes during the computation so that they can't influence Fast,
      Guard, etc. (We should have done this for proposal 109.) Fixes
      bug 8146.
    - When marking a node as a likely sybil, reset its uptime metrics
      to zero, so that it cannot time towards getting marked as Guard,
      Stable, or HSDir. (We should have done this for proposal 109.) Fixes
      bug 8147.
    - Fix a bug in the voting algorithm that could yield incorrect results
      when a non-naming authority declared too many flags. Fixes bug 9200;
      bugfix on 0.2.0.3-alpha.

  o Internal abstraction features:
    - Introduce new channel_t abstraction between circuits and
      or_connection_t to allow for implementing alternate OR-to-OR
      transports. A channel_t is an abstract object which can either be a
      cell-bearing channel, which is responsible for authenticating and
      handshaking with the remote OR and transmitting cells to and from
      it, or a listening channel, which spawns new cell-bearing channels
      at the request of remote ORs. Implements part of ticket 6465.
    - Make a channel_tls_t subclass of channel_t, adapting it to the
      existing or_connection_t code. The V2/V3 protocol handshaking
      code which formerly resided in command.c has been moved below the
      channel_t abstraction layer and may be found in channeltls.c now.
      Implements the rest of ticket 6465.
    - Introduce new circuitmux_t storing the queue of circuits for
      a channel; this encapsulates and abstracts the queue logic and
      circuit selection policy, and allows the latter to be overridden
      easily by switching out a policy object. The existing EWMA behavior
      is now implemented as a circuitmux_policy_t. Resolves ticket 6816.

  o New build requirements:
    - Tor now requires OpenSSL 0.9.8 or later. OpenSSL 1.0.0 or later is
      strongly recommended.
    - Tor maintainers now require Automake version 1.9 or later to build
      Tor from the Git repository. (Automake is not required when building
      from a source distribution.)

  o Minor features (protocol):
    - No longer include the "opt" prefix when generating routerinfos
      or v2 directories: it has been needless since Tor 0.1.2. Closes
      ticket 5124.
    - Reject EXTEND cells sent to nonexistent streams. According to the
      spec, an EXTEND cell sent to _any_ nonzero stream ID is invalid, but
      we were only checking for stream IDs that were currently in use.
      Found while hunting for more instances of bug 6271. Bugfix on
      0.0.2pre8, which introduced incremental circuit construction.
    - Tor relays and clients now support a better CREATE/EXTEND cell
      format, allowing the sender to specify multiple address, identity,
      and handshake types. Implements Robert Ransom's proposal 200;
      closes ticket 7199.
    - Reject as invalid most directory objects containing a NUL.
      Belt-and-suspender fix for bug 8037.

  o Minor features (security):
    - Clear keys and key-derived material left on the stack in
      rendservice.c and rendclient.c. Check return value of
      crypto_pk_write_private_key_to_string() in rend_service_load_keys().
      These fixes should make us more forward-secure against cold-boot
      attacks and the like. Fixes bug 2385.
    - Use our own weak RNG when we need a weak RNG. Windows's rand() and
      Irix's random() only return 15 bits; Solaris's random() returns more
      bits but its RAND_MAX says it only returns 15, and so on. Motivated
      by the fix for bug 7801; bugfix on 0.2.2.20-alpha.

  o Minor features (control protocol):
    - Add a "GETINFO signal/names" control port command. Implements
      ticket 3842.
    - Provide default values for all options via "GETINFO config/defaults".
      Implements ticket 4971.
    - Allow an optional $ before the node identity digest in the
      controller command GETINFO ns/id/<identity>, for consistency with
      md/id/<identity> and desc/id/<identity>. Resolves ticket 7059.
    - Add CACHED keyword to ADDRMAP events in the control protocol
      to indicate whether a DNS result will be cached or not. Resolves
      ticket 8596.
    - Generate bootstrapping status update events correctly when fetching
      microdescriptors. Fixes bug 9927.

  o Minor features (path selection):
    - When deciding whether we have enough descriptors to build circuits,
      instead of looking at raw relay counts, look at which fraction
      of (bandwidth-weighted) paths we're able to build. This approach
      keeps clients from building circuits if their paths are likely to
      stand out statistically. The default fraction of paths needed is
      taken from the consensus directory; you can override it with the
      new PathsNeededToBuildCircuits option. Fixes ticket 5956.
    - When any country code is listed in ExcludeNodes or ExcludeExitNodes,
      and we have GeoIP information, also exclude all nodes with unknown
      countries "??" and "A1". This behavior is controlled by the
      new GeoIPExcludeUnknown option: you can make such nodes always
      excluded with "GeoIPExcludeUnknown 1", and disable the feature
      with "GeoIPExcludeUnknown 0". Setting "GeoIPExcludeUnknown auto"
      gets you the default behavior. Implements feature 7706.

  o Minor features (hidden services):
    - Improve circuit build timeout handling for hidden services.
      In particular: adjust build timeouts more accurately depending
      upon the number of hop-RTTs that a particular circuit type
      undergoes. Additionally, launch intro circuits in parallel
      if they timeout, and take the first one to reply as valid.
    - The Tor client now ignores sub-domain components of a .onion
      address. This change makes HTTP "virtual" hosting
      possible: http://foo.aaaaaaaaaaaaaaaa.onion/ and
      http://bar.aaaaaaaaaaaaaaaa.onion/ can be two different websites
      hosted on the same hidden service. Implements proposal 204.
    - Enable Tor to read configuration, state, and key information from
      a FIFO. Previously Tor would only read from files with a positive
      stat.st_size. Code from meejah; fixes bug 6044.

  o Minor features (clients):
    - Teach bridge-using clients to avoid 0.2.2.x bridges when making
      microdescriptor-related dir requests, and only fall back to normal
      descriptors if none of their bridges can handle microdescriptors
      (as opposed to the fix in ticket 4013, which caused them to fall
      back to normal descriptors if *any* of their bridges preferred
      them). Resolves ticket 4994.
    - Tweak tor-fw-helper to accept an arbitrary amount of arbitrary
      TCP ports to forward. In the past it only accepted two ports:
      the ORPort and the DirPort.

  o Minor features (protecting client timestamps):
    - Clients no longer send timestamps in their NETINFO cells. These were
      not used for anything, and they provided one small way for clients
      to be distinguished from each other as they moved from network to
      network or behind NAT. Implements part of proposal 222.
    - Clients now round timestamps in INTRODUCE cells down to the nearest
      10 minutes. If a new Support022HiddenServices option is set to 0, or
      if it's set to "auto" and the feature is disabled in the consensus,
      the timestamp is sent as 0 instead. Implements part of proposal 222.
    - Stop sending timestamps in AUTHENTICATE cells. This is not such
      a big deal from a security point of view, but it achieves no actual
      good purpose, and isn't needed. Implements part of proposal 222.
    - Reduce down accuracy of timestamps in hidden service descriptors.
      Implements part of proposal 222.

  o Minor features (bridges):
    - Make bridge relays check once a minute for whether their IP
      address has changed, rather than only every 15 minutes. Resolves
      bugs 1913 and 1992.
    - Bridge statistics now count bridge clients connecting over IPv6:
      bridge statistics files now list "bridge-ip-versions" and
      extra-info documents list "geoip6-db-digest". The control protocol
      "CLIENTS_SEEN" and "ip-to-country" queries now support IPv6. Initial
      implementation by "shkoo", addressing ticket 5055.
    - Add a new torrc option "ServerTransportListenAddr" to let bridge
      operators select the address where their pluggable transports will
      listen for connections. Resolves ticket 7013.
    - Randomize the lifetime of our SSL link certificate, so censors can't
      use the static value for filtering Tor flows. Resolves ticket 8443;
      related to ticket 4014 which was included in 0.2.2.33.

  o Minor features (relays):
    - Option OutboundBindAddress can be specified multiple times and
      accepts IPv6 addresses. Resolves ticket 6876.

  o Minor features (IPv6, client side):
    - AutomapHostsOnResolve now supports IPv6 addresses. By default, we
      prefer to hand out virtual IPv6 addresses, since there are more of
      them and we can't run out. To override this behavior and make IPv4
      addresses preferred, set NoPreferIPv6Automap on whatever SOCKSPort
      or DNSPort you're using for resolving. Implements ticket 7571.
    - AutomapHostsOnResolve responses are now randomized, to avoid
      annoying situations where Tor is restarted and applications
      connect to the wrong addresses.
    - Never try more than 1000 times to pick a new virtual address when
      AutomapHostsOnResolve is set. That's good enough so long as we
      aren't close to handing out our entire virtual address space;
      if you're getting there, it's best to switch to IPv6 virtual
      addresses anyway.

  o Minor features (IPv6, relay/authority side):
    - New config option "AuthDirHasIPv6Connectivity 1" that directory
      authorities should set if they have IPv6 connectivity and want to
      do reachability tests for IPv6 relays. Implements feature 5974.
    - A relay with an IPv6 OR port now sends that address in NETINFO
      cells (in addition to its other address). Implements ticket 6364.

  o Minor features (directory authorities):
    - Directory authorities no long accept descriptors for any version of
      Tor before 0.2.2.35, or for any 0.2.3 release before 0.2.3.10-alpha.
      These versions are insecure, unsupported, or both. Implements
      ticket 6789.
    - When directory authorities are computing thresholds for flags,
      never let the threshold for the Fast flag fall below 4096
      bytes. Also, do not consider nodes with extremely low bandwidths
      when deciding thresholds for various directory flags. This change
      should raise our threshold for Fast relays, possibly in turn
      improving overall network performance; see ticket 1854. Resolves
      ticket 8145.
    - Directory authorities now include inside each vote a statement of
      the performance thresholds they used when assigning flags.
      Implements ticket 8151.
    - Add an "ignoring-advertised-bws" boolean to the flag-threshold lines
      in directory authority votes to describe whether they have enough
      measured bandwidths to ignore advertised (relay descriptor)
      bandwidth claims. Resolves ticket 8711.

  o Minor features (path bias detection):
    - Path Use Bias: Perform separate accounting for successful circuit
      use. Keep separate statistics on stream attempt rates versus stream
      success rates for each guard. Provide configurable thresholds to
      determine when to emit log messages or disable use of guards that
      fail too many stream attempts. Resolves ticket 7802.
    - Create three levels of Path Bias log messages, as opposed to just
      two. These are configurable via consensus as well as via the torrc
      options PathBiasNoticeRate, PathBiasWarnRate, PathBiasExtremeRate.
      The default values are 0.70, 0.50, and 0.30 respectively.
    - Separate the log message levels from the decision to drop guards,
      which also is available via torrc option PathBiasDropGuards.
      PathBiasDropGuards still defaults to 0 (off).
    - Deprecate PathBiasDisableRate in favor of PathBiasDropGuards
      in combination with PathBiasExtremeRate.
    - Increase the default values for PathBiasScaleThreshold and
      PathBiasCircThreshold from (200, 20) to (300, 150).
    - Add in circuit usage accounting to path bias. If we try to use a
      built circuit but fail for any reason, it counts as path bias.
      Certain classes of circuits where the adversary gets to pick your
      destination node are exempt from this accounting. Usage accounting
      can be specifically disabled via consensus parameter or torrc.
    - Convert all internal path bias state to double-precision floating
      point, to avoid roundoff error and other issues.
    - Only record path bias information for circuits that have completed
      *two* hops. Assuming end-to-end tagging is the attack vector, this
      makes us more resilient to ambient circuit failure without any
      detection capability loss.

  o Minor features (build):
    - Tor now builds correctly on Bitrig, an OpenBSD fork. Patch from
      dhill. Resolves ticket 6982.
    - Compile on win64 using mingw64. Fixes bug 7260; patches from
      "yayooo".
    - Work correctly on Unix systems where EAGAIN and EWOULDBLOCK are
      separate error codes; or at least, don't break for that reason.
      Fixes bug 7935. Reported by "oftc_must_be_destroyed".

  o Build improvements (autotools):
    - Warn if building on a platform with an unsigned time_t: there
      are too many places where Tor currently assumes that time_t can
      hold negative values. We'd like to fix them all, but probably
      some will remain.
    - Do not report status verbosely from autogen.sh unless the -v flag
      is specified. Fixes issue 4664. Patch from Onizuka.
    - Detect and reject attempts to build Tor with threading support
      when OpenSSL has been compiled without threading support.
      Fixes bug 6673.
    - Try to detect if we are ever building on a platform where
      memset(...,0,...) does not set the value of a double to 0.0. Such
      platforms are permitted by the C standard, though in practice
      they're pretty rare (since IEEE 754 is nigh-ubiquitous). We don't
      currently support them, but it's better to detect them and fail
      than to perform erroneously.
    - We no longer warn so much when generating manpages from their
      asciidoc source.
    - Use Ville Laurikari's implementation of AX_CHECK_SIGN() to determine
      the signs of types during autoconf. This is better than our old
      approach, which didn't work when cross-compiling.

  o Minor features (log messages, warnings):
    - Detect when we're running with a version of OpenSSL other than the
      one we compiled with. This conflict has occasionally given people
      hard-to-track-down errors.
    - Warn users who run hidden services on a Tor client with
      UseEntryGuards disabled that their hidden services will be
      vulnerable to http://freehaven.net/anonbib/#hs-attack06 (the
      attack which motivated Tor to support entry guards in the first
      place). Resolves ticket 6889.
    - Warn when we are binding low ports when hibernation is enabled;
      previously we had warned when we were _advertising_ low ports with
      hibernation enabled. Fixes bug 7285; bugfix on 0.2.3.9-alpha.
    - Issue a warning when running with the bufferevents backend enabled.
      It's still not stable, and people should know that they're likely
      to hit unexpected problems. Closes ticket 9147.

  o Minor features (log messages, notices):
    - Refactor resolve_my_address() so it returns the method by which we
      decided our public IP address (explicitly configured, resolved from
      explicit hostname, guessed from interfaces, learned by gethostname).
      Now we can provide more helpful log messages when a relay guesses
      its IP address incorrectly (e.g. due to unexpected lines in
      /etc/hosts). Resolves ticket 2267.
    - Track how many "TAP" and "NTor" circuit handshake requests we get,
      and how many we complete, and log it every hour to help relay
      operators follow trends in network load. Addresses ticket 9658.

  o Minor features (log messages, diagnostics):
    - If we fail to free a microdescriptor because of bug 7164, log
      the filename and line number from which we tried to free it.
    - We compute the overhead from passing onionskins back and forth to
      cpuworkers, and report it when dumping statistics in response to
      SIGUSR1. Supports ticket 7291.
    - Add another diagnostic to the heartbeat message: track and log
      overhead that TLS is adding to the data we write. If this is
      high, we are sending too little data to SSL_write at a time.
      Diagnostic for bug 7707.