Merge remote-tracking branch 'teor/reject-tap-v6'

changes/reject-tap

@@ -0,0 +1,15 @@
+  o Major bug fixes (circuit building):
+    - Tor authorities, relays, and clients only use ntor, except for
+      rare cases in the hidden service protocol.
+    - Authorities, relays and clients specifically check that each
+      descriptor has an ntor key.
+    - Clients avoid downloading a descriptor if the relay version is
+      too old to support ntor.
+    - Client code never chooses nodes without ntor keys: they will not
+      be selected during circuit-building, or as guards, or as directory
+      mirrors, or as introduction or rendezvous points.
+    - Circuit-building code assumes that all hops can use ntor,
+      except for rare hidden service protocol cases.
+    - Hidden service client to intro point and service to rendezvous point
+      connections use the TAP key supplied by the protocol.
+      Fixes bug 19163; bugfix on 0.2.4.18-rc.

doc/tor.1.txt

@@ -1452,16 +1452,6 @@ The following options are useful only for clients (that is, if
     "auto" (recommended) then it is on for all clients that do not set
     FetchUselessDescriptors. (Default: auto)
 
-[[UseNTorHandshake]] **UseNTorHandshake** **0**|**1**|**auto**::
-    The "ntor" circuit-creation handshake is faster and (we think) more
-    secure than the original ("TAP") circuit handshake, but starting to use
-    it too early might make your client stand out. If this option is 0, your
-    Tor client won't use the ntor handshake. If it's 1, your Tor client
-    will use the ntor handshake to extend circuits through servers that
-    support it. If this option is "auto", then your client
-    will use the ntor handshake once enough directory authorities recommend
-    it. (Default: 1)
-
 [[PathBiasCircThreshold]] **PathBiasCircThreshold** __NUM__ +
 
 [[PathBiasNoticeRate]] **PathBiasNoticeRate** __NUM__ +

src/or/circuitbuild.c

@@ -58,7 +58,6 @@ static crypt_path_t *onion_next_hop_in_cpath(crypt_path_t *cpath);
 static int onion_extend_cpath(origin_circuit_t *circ);
 static int count_acceptable_nodes(smartlist_t *routers);
 static int onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice);
-static int circuits_can_use_ntor(void);
 
 /** This function tries to get a channel to the specified endpoint,
  * and then calls command_setup_channel() to give it the right
@@ -365,7 +364,7 @@ circuit_rep_hist_note_result(origin_circuit_t *circ)
   } while (hop!=circ->cpath);
 }
 
-/** Return 1 iff at least one node in circ's cpath supports ntor. */
+/** Return 1 iff every node in circ's cpath definitely supports ntor. */
 static int
 circuit_cpath_supports_ntor(const origin_circuit_t *circ)
 {
@@ -373,16 +372,19 @@ circuit_cpath_supports_ntor(const origin_circuit_t *circ)
 
   cpath = head = circ->cpath;
   do {
-    if (cpath->extend_info &&
-        !tor_mem_is_zero(
-            (const char*)cpath->extend_info->curve25519_onion_key.public_key,
-            CURVE25519_PUBKEY_LEN))
-      return 1;
+    /* if the extend_info is missing, we can't tell if it supports ntor */
+    if (!cpath->extend_info) {
+      return 0;
+    }
 
+    /* if the key is blank, it definitely doesn't support ntor */
+    if (!extend_info_supports_ntor(cpath->extend_info)) {
+      return 0;
+    }
     cpath = cpath->next;
   } while (cpath != head);
 
-  return 0;
+  return 1;
 }
 
 /** Pick all the entries in our cpath. Stop and return 0 when we're
@@ -390,41 +392,61 @@ circuit_cpath_supports_ntor(const origin_circuit_t *circ)
 static int
 onion_populate_cpath(origin_circuit_t *circ)
 {
-  int n_tries = 0;
-  const int using_ntor = circuits_can_use_ntor();
+  int r = 0;
 
-#define MAX_POPULATE_ATTEMPTS 32
+  /* onion_extend_cpath assumes these are non-NULL */
+  tor_assert(circ);
+  tor_assert(circ->build_state);
 
-  while (1) {
-    int r = onion_extend_cpath(circ);
+  while (r == 0) {
+    r = onion_extend_cpath(circ);
     if (r < 0) {
       log_info(LD_CIRC,"Generating cpath hop failed.");
       return -1;
     }
-    if (r == 1) {
-      /* This circuit doesn't need/shouldn't be forced to have an ntor hop */
-      if (circ->build_state->desired_path_len <= 1 || ! using_ntor)
-        return 0;
+  }
 
-      /* This circuit has an ntor hop. great! */
-      if (circuit_cpath_supports_ntor(circ))
-        return 0;
+  /* The path is complete */
+  tor_assert(r == 1);
 
-      /* No node in the circuit supports ntor.  Have we already tried too many
-       * times? */
-      if (++n_tries >= MAX_POPULATE_ATTEMPTS)
-        break;
+  /* Does every node in this path support ntor? */
+  int path_supports_ntor = circuit_cpath_supports_ntor(circ);
+
+  /* We would like every path to support ntor, but we have to allow for some
+   * edge cases. */
+  tor_assert(circuit_get_cpath_len(circ));
+  if (circuit_can_use_tap(circ)) {
+    /* Circuits from clients to intro points, and hidden services to
+     * rend points do not support ntor, because the hidden service protocol
+     * does not include ntor onion keys. This is also true for Tor2web clients
+     * and Single Onion Services. */
+    return 0;
+  }
 
-      /* Clear the path and retry */
-      circuit_clear_cpath(circ);
+  if (circuit_get_cpath_len(circ) == 1) {
+    /* Allow for bootstrapping: when we're fetching directly from a fallback,
+     * authority, or bridge, we have no way of knowing its ntor onion key
+     * before we connect to it. So instead, we try connecting, and end up using
+     * CREATE_FAST. */
+    tor_assert(circ->cpath);
+    tor_assert(circ->cpath->extend_info);
+    const node_t *node = node_get_by_id(
+                                    circ->cpath->extend_info->identity_digest);
+    /* If we don't know the node and its descriptor, we must be bootstrapping.
+     */
+    if (!node || !node_has_descriptor(node)) {
+      return 0;
     }
   }
-  log_warn(LD_CIRC, "I tried for %d times, but I couldn't build a %d-hop "
-           "circuit with at least one node that supports ntor.",
-           MAX_POPULATE_ATTEMPTS,
-           circ->build_state->desired_path_len);
 
-  return -1;
+  if (BUG(!path_supports_ntor)) {
+    /* If we're building a multi-hop path, and it's not one of the HS or
+     * bootstrapping exceptions, and it doesn't support ntor, something has
+     * gone wrong. */
+    return -1;
+  }
+
+  return 0;
 }
 
 /** Create and return a new origin circuit. Initialize its purpose and
@@ -757,10 +779,13 @@ should_use_create_fast_for_circuit(origin_circuit_t *circ)
   tor_assert(circ->cpath);
   tor_assert(circ->cpath->extend_info);
 
-  if (!circ->cpath->extend_info->onion_key)
-    return 1; /* our hand is forced: only a create_fast will work. */
+  if (!circuit_has_usable_onion_key(circ)) {
+    /* We don't have ntor, and we don't have or can't use TAP,
+     * so our hand is forced: only a create_fast will work. */
+    return 1;
+  }
   if (public_server_mode(options)) {
-    /* We're a server, and we know an onion key. We can choose.
+    /* We're a server, and we have a usable onion key. We can choose.
      * Prefer to blend our circuit into the other circuits we are
      * creating on behalf of others. */
     return 0;
@@ -785,30 +810,20 @@ circuit_timeout_want_to_count_circ(origin_circuit_t *circ)
           && circ->build_state->desired_path_len == DEFAULT_ROUTE_LEN;
 }
 
-/** Return true if the ntor handshake is enabled in the configuration, or if
- * it's been set to "auto" in the configuration and it's enabled in the
- * consensus. */
-static int
-circuits_can_use_ntor(void)
-{
-  const or_options_t *options = get_options();
-  if (options->UseNTorHandshake != -1)
-    return options->UseNTorHandshake;
-  return networkstatus_get_param(NULL, "UseNTorHandshake", 0, 0, 1);
-}
-
 /** Decide whether to use a TAP or ntor handshake for connecting to <b>ei</b>
  * directly, and set *<b>cell_type_out</b> and *<b>handshake_type_out</b>
- * accordingly. */
+ * accordingly.
+ * Note that TAP handshakes are only used for direct connections:
+ *  - from Tor2web to intro points not in the client's consensus, and
+ *  - from Single Onions to rend points not in the service's consensus.
+ * This is checked in onion_populate_cpath. */
 static void
 circuit_pick_create_handshake(uint8_t *cell_type_out,
                               uint16_t *handshake_type_out,
                               const extend_info_t *ei)
 {
-  /* XXXX029 Remove support for deciding to use TAP. */
-  if (!tor_mem_is_zero((const char*)ei->curve25519_onion_key.public_key,
-                       CURVE25519_PUBKEY_LEN) &&
-      circuits_can_use_ntor()) {
+  /* XXXX030 Remove support for deciding to use TAP. */
+  if (extend_info_supports_ntor(ei)) {
     *cell_type_out = CELL_CREATE2;
     *handshake_type_out = ONION_HANDSHAKE_TYPE_NTOR;
     return;
@@ -822,7 +837,11 @@ circuit_pick_create_handshake(uint8_t *cell_type_out,
  * directly, and set *<b>handshake_type_out</b> accordingly. Decide whether,
  * in extending through <b>node</b> to do so, we should use an EXTEND2 or an
  * EXTEND cell to do so, and set *<b>cell_type_out</b> and
- * *<b>create_cell_type_out</b> accordingly. */
+ * *<b>create_cell_type_out</b> accordingly.
+ * Note that TAP handshakes are only used for extend handshakes:
+ *  - from clients to intro points, and
+ *  - from hidden services to rend points.
+ * This is checked in onion_populate_cpath. */
 static void
 circuit_pick_extend_handshake(uint8_t *cell_type_out,
                               uint8_t *create_cell_type_out,
@@ -833,17 +852,27 @@ circuit_pick_extend_handshake(uint8_t *cell_type_out,
   uint8_t t;
   circuit_pick_create_handshake(&t, handshake_type_out, ei);
 
-  /* XXXX029 Remove support for deciding to use TAP. */
+  /* XXXX030 Remove support for deciding to use TAP. */
+
+  /* It is an error to extend if there is no previous node. */
+  tor_assert_nonfatal(node_prev);
+  /* It is an error for a node with a known version to be so old it does not
+   * support ntor. */
+  tor_assert_nonfatal(routerstatus_version_supports_ntor(node_prev->rs, 1));
+
+  /* Assume relays without tor versions or routerstatuses support ntor.
+   * The authorities enforce ntor support, and assuming and failing is better
+   * than allowing a malicious node to perform a protocol downgrade to TAP. */
   if (node_prev &&
       *handshake_type_out != ONION_HANDSHAKE_TYPE_TAP &&
       (node_has_curve25519_onion_key(node_prev) ||
-       (node_prev->rs && node_prev->rs->version_supports_extend2_cells))) {
-    *cell_type_out = RELAY_COMMAND_EXTEND2;
-    *create_cell_type_out = CELL_CREATE2;
-  } else {
-    *cell_type_out = RELAY_COMMAND_EXTEND;
-    *create_cell_type_out = CELL_CREATE;
-  }
+       (routerstatus_version_supports_ntor(node_prev->rs, 1)))) {
+        *cell_type_out = RELAY_COMMAND_EXTEND2;
+        *create_cell_type_out = CELL_CREATE2;
+      } else {
+        *cell_type_out = RELAY_COMMAND_EXTEND;
+        *create_cell_type_out = CELL_CREATE;
+      }
 }
 
 /** This is the backbone function for building circuits.
@@ -2058,15 +2087,18 @@ count_acceptable_nodes(smartlist_t *nodes)
     if (! node->is_running)
 //      log_debug(LD_CIRC,"Nope, the directory says %d is not running.",i);
       continue;
+    /* XXX This clause makes us count incorrectly: if AllowInvalidRouters
+     * allows this node in some places, then we're getting an inaccurate
+     * count. For now, be conservative and don't count it. But later we
+     * should try to be smarter. */
     if (! node->is_valid)
 //      log_debug(LD_CIRC,"Nope, the directory says %d is not valid.",i);
       continue;
     if (! node_has_descriptor(node))
       continue;
-      /* XXX This clause makes us count incorrectly: if AllowInvalidRouters
-       * allows this node in some places, then we're getting an inaccurate
-       * count. For now, be conservative and don't count it. But later we
-       * should try to be smarter. */
+    /* The node has a descriptor, so we can just check the ntor key directly */
+    if (!node_has_curve25519_onion_key(node))
+      continue;
     ++num;
   } SMARTLIST_FOREACH_END(node);
 
@@ -2356,6 +2388,14 @@ extend_info_from_node(const node_t *node, int for_direct_connect)
     log_warn(LD_CIRC, "Could not choose valid address for %s",
               node->ri ? node->ri->nickname : node->rs->nickname);
 
+  /* Every node we connect or extend to must support ntor */
+  if (!node_has_curve25519_onion_key(node)) {
+    log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
+           "Attempted to create extend_info for a node that does not support "
+           "ntor: %s", node_describe(node));
+    return NULL;
+  }
+
   if (valid_addr && node->ri)
     return extend_info_new(node->ri->nickname,
                              node->identity,
@@ -2441,3 +2481,65 @@ extend_info_addr_is_allowed(const tor_addr_t *addr)
   return 0;
 }
 
+/* Does ei have a valid TAP key? */
+int
+extend_info_supports_tap(const extend_info_t* ei)
+{
+  tor_assert(ei);
+  /* Valid TAP keys are not NULL */
+  return ei->onion_key != NULL;
+}
+
+/* Does ei have a valid ntor key? */
+int
+extend_info_supports_ntor(const extend_info_t* ei)
+{
+  tor_assert(ei);
+  /* Valid ntor keys have at least one non-zero byte */
+  return !tor_mem_is_zero(
+                          (const char*)ei->curve25519_onion_key.public_key,
+                          CURVE25519_PUBKEY_LEN);
+}
+
+/* Is circuit purpose allowed to use the deprecated TAP encryption protocol?
+ * The hidden service protocol still uses TAP for some connections, because
+ * ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */
+static int
+circuit_purpose_can_use_tap_impl(uint8_t purpose)
+{
+  return (purpose == CIRCUIT_PURPOSE_S_CONNECT_REND ||
+          purpose == CIRCUIT_PURPOSE_C_INTRODUCING);
+}
+
+/* Is circ allowed to use the deprecated TAP encryption protocol?
+ * The hidden service protocol still uses TAP for some connections, because
+ * ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */
+int
+circuit_can_use_tap(const origin_circuit_t *circ)
+{
+  tor_assert(circ);
+  tor_assert(circ->cpath);
+  tor_assert(circ->cpath->extend_info);
+  return (circuit_purpose_can_use_tap_impl(circ->base_.purpose) &&
+          extend_info_supports_tap(circ->cpath->extend_info));
+}
+
+/* Does circ have an onion key which it's allowed to use? */
+int
+circuit_has_usable_onion_key(const origin_circuit_t *circ)
+{
+  tor_assert(circ);
+  tor_assert(circ->cpath);
+  tor_assert(circ->cpath->extend_info);
+  return (extend_info_supports_ntor(circ->cpath->extend_info) ||
+          circuit_can_use_tap(circ));
+}
+
+/* Does ei have an onion key which it would prefer to use?
+ * Currently, we prefer ntor keys*/
+int
+extend_info_has_preferred_onion_key(const extend_info_t* ei)
+{
+  tor_assert(ei);
+  return extend_info_supports_ntor(ei);
+}

src/or/circuitbuild.h

@@ -54,6 +54,11 @@ extend_info_t *extend_info_from_node(const node_t *r, int for_direct_connect);
 extend_info_t *extend_info_dup(extend_info_t *info);
 void extend_info_free(extend_info_t *info);
 int extend_info_addr_is_allowed(const tor_addr_t *addr);
+int extend_info_supports_tap(const extend_info_t* ei);
+int extend_info_supports_ntor(const extend_info_t* ei);
+int circuit_can_use_tap(const origin_circuit_t *circ);
+int circuit_has_usable_onion_key(const origin_circuit_t *circ);
+int extend_info_has_preferred_onion_key(const extend_info_t* ei);
 const node_t *build_state_get_exit_node(cpath_build_state_t *state);
 const char *build_state_get_exit_nickname(cpath_build_state_t *state);
 

src/or/circuitlist.c

@@ -1613,7 +1613,8 @@ circuit_find_to_cannibalize(uint8_t purpose, extend_info_t *info,
   return best;
 }
 
-/** Return the number of hops in circuit's path. */
+/** Return the number of hops in circuit's path. If circ has no entries,
+ * or is NULL, returns 0. */
 int
 circuit_get_cpath_len(origin_circuit_t *circ)
 {
@@ -1629,7 +1630,8 @@ circuit_get_cpath_len(origin_circuit_t *circ)
 }
 
 /** Return the <b>hopnum</b>th hop in <b>circ</b>->cpath, or NULL if there
- * aren't that many hops in the list. */
+ * aren't that many hops in the list. <b>hopnum</b> starts at 1.
+ * Returns NULL if <b>hopnum</b> is 0 or negative. */
 crypt_path_t *
 circuit_get_cpath_hop(origin_circuit_t *circ, int hopnum)
 {

src/or/config.c

@@ -438,7 +438,7 @@ static config_var_t option_vars_[] = {
   V(UseEntryGuardsAsDirGuards,   BOOL,     "1"),
   V(UseGuardFraction,            AUTOBOOL, "auto"),
   V(UseMicrodescriptors,         AUTOBOOL, "auto"),
-  V(UseNTorHandshake,            AUTOBOOL, "1"),
+  OBSOLETE("UseNTorHandshake"),
   V(User,                        STRING,   NULL),
   OBSOLETE("UserspaceIOCPBuffers"),
   V(AuthDirSharedRandomness,     BOOL,     "1"),

src/or/dirserv.c

@@ -255,6 +255,20 @@ dirserv_router_get_status(const routerinfo_t *router, const char **msg,
     return FP_REJECT;
   }
 
+  /* dirserv_get_status_impl already rejects versions older than 0.2.4.18-rc,
+   * and onion_curve25519_pkey was introduced in 0.2.4.8-alpha.
+   * But just in case a relay doesn't provide or lies about its version, or
+   * doesn't include an ntor key in its descriptor, check that it exists,
+   * and is non-zero (clients check that it's non-zero before using it). */
+  if (!routerinfo_has_curve25519_onion_key(router)) {
+    log_fn(severity, LD_DIR,
+           "Descriptor from router %s is missing an ntor curve25519 onion "
+           "key.", router_describe(router));
+    if (msg)
+      *msg = "Missing ntor curve25519 onion key. Please upgrade!";
+    return FP_REJECT;
+  }
+
   if (router->cache_info.signing_key_cert) {
     /* This has an ed25519 identity key. */
     if (KEYPIN_MISMATCH ==

src/or/networkstatus.c

@@ -2275,6 +2275,12 @@ client_would_use_router(const routerstatus_t *rs, time_t now,
     /* We'd drop it immediately for being too old. */
     return 0;
   }
+  if (!routerstatus_version_supports_ntor(rs, 1)) {
+    /* We'd ignore it because it doesn't support ntor.
+     * If we don't know the version, download the descriptor so we can
+     * check if it supports ntor. */
+    return 0;
+  }
   return 1;
 }
 

src/or/nodelist.c

@@ -1173,14 +1173,38 @@ node_get_pref_ipv6_dirport(const node_t *node, tor_addr_port_t *ap_out)
   }
 }
 
+/** Return true iff <b>md</b> has a curve25519 onion key.
+ * Use node_has_curve25519_onion_key() instead of calling this directly. */
+static int
+microdesc_has_curve25519_onion_key(const microdesc_t *md)
+{
+  if (!md) {
+    return 0;
+  }
+
+  if (!md->onion_curve25519_pkey) {
+    return 0;
+  }
+
+  if (tor_mem_is_zero((const char*)md->onion_curve25519_pkey->public_key,
+                      CURVE25519_PUBKEY_LEN)) {
+    return 0;
+  }
+
+  return 1;
+}
+
 /** Return true iff <b>node</b> has a curve25519 onion key. */
 int
 node_has_curve25519_onion_key(const node_t *node)
 {
+  if (!node)
+    return 0;
+
   if (node->ri)
-    return node->ri->onion_curve25519_pkey != NULL;
+    return routerinfo_has_curve25519_onion_key(node->ri);
   else if (node->md)
-    return node->md->onion_curve25519_pkey != NULL;
+    return microdesc_has_curve25519_onion_key(node->md);
   else
     return 0;
 }

src/or/onion.c

@@ -11,6 +11,7 @@
  **/
 
 #include "or.h"
+#include "circuitbuild.h"
 #include "circuitlist.h"
 #include "config.h"
 #include "cpuworker.h"
@@ -438,8 +439,7 @@ onion_skin_create(int type,
     r = CREATE_FAST_LEN;
     break;
   case ONION_HANDSHAKE_TYPE_NTOR:
-    if (tor_mem_is_zero((const char*)node->curve25519_onion_key.public_key,
-                        CURVE25519_PUBKEY_LEN))
+    if (!extend_info_supports_ntor(node))
       return -1;
     if (onion_skin_ntor_create((const uint8_t*)node->identity_digest,
                                &node->curve25519_onion_key,

src/or/or.h

@@ -4384,9 +4384,6 @@ typedef struct {
 
   char *TLSECGroup; /**< One of "P256", "P224", or nil for auto */
 
-  /** Autobool: should we use the ntor handshake if we can? */
-  int UseNTorHandshake;
-
   /** Fraction: */
   double PathsNeededToBuildCircuits;
 

src/or/rendclient.c

@@ -1368,8 +1368,13 @@ rend_client_get_random_intro_impl(const rend_cache_entry_t *entry,
 
   i = crypto_rand_int(smartlist_len(usable_nodes));
   intro = smartlist_get(usable_nodes, i);
+  if (BUG(!intro->extend_info)) {
+    /* This should never happen, but it isn't fatal, just try another */
+    smartlist_del(usable_nodes, i);
+    goto again;
+  }
   /* Do we need to look up the router or is the extend info complete? */
-  if (!intro->extend_info->onion_key) {
+  if (!extend_info_supports_tap(intro->extend_info)) {
     const node_t *node;
     extend_info_t *new_extend_info;
     if (tor_digest_is_zero(intro->extend_info->identity_digest))

src/or/rendservice.c

@@ -3896,3 +3896,11 @@ rend_service_set_connection_addr_port(edge_connection_t *conn,
     return -2;
 }
 
+/* Stub that should be replaced with the #17178 version of the function
+ * when merging. */
+int
+rend_service_allow_direct_connection(const or_options_t *options)
+{
+  (void)options;
+  return 0;
+}

src/or/rendservice.h

@@ -131,5 +131,7 @@ void directory_post_to_hs_dir(rend_service_descriptor_t *renddesc,
                               const char *service_id, int seconds_valid);
 void rend_service_desc_has_uploaded(const rend_data_t *rend_data);
 
+int rend_service_allow_direct_connection(const or_options_t *options);
+
 #endif
 

src/or/router.c

@@ -2836,6 +2836,10 @@ router_dump_router_to_string(routerinfo_t *router,
                   (const char *)router->onion_curve25519_pkey->public_key,
                   CURVE25519_PUBKEY_LEN, BASE64_ENCODE_MULTILINE);
     smartlist_add_asprintf(chunks, "ntor-onion-key %s", kbuf);
+  } else {
+    /* Authorities will start rejecting relays without ntor keys in 0.2.9 */
+    log_err(LD_BUG, "A relay must have an ntor onion key");
+    goto err;
   }
 
   /* Write the exit policy to the end of 's'. */

src/or/routerlist.c

@@ -2260,10 +2260,16 @@ router_add_running_nodes_to_smartlist(smartlist_t *sl, int allow_invalid,
       continue;
     if (node_is_unreliable(node, need_uptime, need_capacity, need_guard))
       continue;
-    /* Choose a node with an OR address that matches the firewall rules,
-     * if we are making a direct connection */
+    /* Don't choose nodes if we are certain they can't do ntor */
+    if (node->rs && !routerstatus_version_supports_ntor(node->rs, 1))
+      continue;
+    if ((node->ri || node->md) && !node_has_curve25519_onion_key(node))
+      continue;
+    /* Choose a node with an OR address that matches the firewall rules */
     if (direct_conn && check_reach &&
-        !fascist_firewall_allows_node(node, FIREWALL_OR_CONNECTION, pref_addr))
+        !fascist_firewall_allows_node(node,
+                                      FIREWALL_OR_CONNECTION,
+                                      pref_addr))
       continue;
 
     smartlist_add(sl, (void *)node);
@@ -5497,6 +5503,45 @@ routerinfo_incompatible_with_extrainfo(const crypto_pk_t *identity_pkey,
   return r;
 }
 
+/* Does ri have a valid ntor onion key?
+ * Valid ntor onion keys exist and have at least one non-zero byte. */
+int
+routerinfo_has_curve25519_onion_key(const routerinfo_t *ri)
+{
+  if (!ri) {
+    return 0;
+  }
+
+  if (!ri->onion_curve25519_pkey) {
+    return 0;
+  }
+
+  if (tor_mem_is_zero((const char*)ri->onion_curve25519_pkey->public_key,
+                      CURVE25519_PUBKEY_LEN)) {
+    return 0;
+  }
+
+  return 1;
+}
+
+/* Is rs running a tor version known to support ntor?
+ * If allow_unknown_versions is true, return true if the version is unknown.
+ * Otherwise, return false if the version is unknown. */
+int
+routerstatus_version_supports_ntor(const routerstatus_t *rs,
+                                   int allow_unknown_versions)
+{
+  if (!rs) {
+    return allow_unknown_versions;
+  }
+
+  if (!rs->version_known) {
+    return allow_unknown_versions;
+  }
+
+  return rs->version_supports_extend2_cells;
+}
+
 /** Assert that the internal representation of <b>rl</b> is
  * self-consistent. */
 void

src/or/routerlist.h

@@ -206,6 +206,9 @@ int routerinfo_incompatible_with_extrainfo(const crypto_pk_t *ri,
                                            extrainfo_t *ei,
                                            signed_descriptor_t *sd,
                                            const char **msg);
+int routerinfo_has_curve25519_onion_key(const routerinfo_t *ri);
+int routerstatus_version_supports_ntor(const routerstatus_t *rs,
+                                       int allow_unknown_versions);
 
 void routerlist_assert_ok(const routerlist_t *rl);
 const char *esc_router_info(const routerinfo_t *router);

src/test/test_dir.c

@@ -116,6 +116,7 @@ test_dir_formats(void *arg)
   const addr_policy_t *p;
   time_t now = time(NULL);
   port_cfg_t orport, dirport;
+  char cert_buf[256];
 
   (void)arg;
   pk1 = pk_generate(0);
@@ -135,6 +136,11 @@ test_dir_formats(void *arg)
   tor_addr_parse(&r1->ipv6_addr, "1:2:3:4::");
   r1->ipv6_orport = 9999;
   r1->onion_pkey = crypto_pk_dup_key(pk1);
+  /* Fake just enough of an ntor key to get by */
+  curve25519_keypair_t r1_onion_keypair;
+  curve25519_keypair_generate(&r1_onion_keypair, 0);
+  r1->onion_curve25519_pkey = tor_memdup(&r1_onion_keypair.pubkey,
+                                         sizeof(curve25519_public_key_t));
   r1->identity_pkey = crypto_pk_dup_key(pk2);
   r1->bandwidthrate = 1000;
   r1->bandwidthburst = 5000;
@@ -167,11 +173,6 @@ test_dir_formats(void *arg)
                                          &kp2.pubkey,
                                          now, 86400,
                                          CERT_FLAG_INCLUDE_SIGNING_KEY);
-  char cert_buf[256];
-  base64_encode(cert_buf, sizeof(cert_buf),
-                (const char*)r2->cache_info.signing_key_cert->encoded,
-                r2->cache_info.signing_key_cert->encoded_len,
-                BASE64_ENCODE_MULTILINE);
   r2->platform = tor_strdup(platform);
   r2->cache_info.published_on = 5;
   r2->or_port = 9005;
@@ -247,6 +248,11 @@ test_dir_formats(void *arg)
   strlcat(buf2, "hidden-service-dir\n", sizeof(buf2));
   strlcat(buf2, "contact Magri White <magri@elsewhere.example.com>\n",
           sizeof(buf2));
+  strlcat(buf2, "ntor-onion-key ", sizeof(buf2));
+  base64_encode(cert_buf, sizeof(cert_buf),
+                (const char*)r1_onion_keypair.pubkey.public_key, 32,
+                BASE64_ENCODE_MULTILINE);
+  strlcat(buf2, cert_buf, sizeof(buf2));
   strlcat(buf2, "reject *:*\n", sizeof(buf2));
   strlcat(buf2, "tunnelled-dir-server\nrouter-signature\n", sizeof(buf2));
   buf[strlen(buf2)] = '\0'; /* Don't compare the sig; it's never the same
@@ -276,6 +282,10 @@ test_dir_formats(void *arg)
           "router Fred 10.3.2.1 9005 0 0\n"
           "identity-ed25519\n"
           "-----BEGIN ED25519 CERT-----\n", sizeof(buf2));
+  base64_encode(cert_buf, sizeof(cert_buf),
+                (const char*)r2->cache_info.signing_key_cert->encoded,
+                r2->cache_info.signing_key_cert->encoded_len,
+                BASE64_ENCODE_MULTILINE);
   strlcat(buf2, cert_buf, sizeof(buf2));
   strlcat(buf2, "-----END ED25519 CERT-----\n", sizeof(buf2));
   strlcat(buf2, "master-key-ed25519 ", sizeof(buf2));