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- /* Copyright (c) 2003-2004, Roger Dingledine.
- * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
- * Copyright (c) 2007-2018, The Tor Project, Inc. */
- /* See LICENSE for licensing information */
- /**
- * \file dns.c
- * \brief Implements a local cache for DNS results for Tor servers.
- * This is implemented as a wrapper around Adam Langley's eventdns.c code.
- * (We can't just use gethostbyname() and friends because we really need to
- * be nonblocking.)
- *
- * There are three main cases when a Tor relay uses dns.c to launch a DNS
- * request:
- * <ol>
- * <li>To check whether the DNS server is working more or less correctly.
- * This happens via dns_launch_correctness_checks(). The answer is
- * reported in the return value from later calls to
- * dns_seems_to_be_broken().
- * <li>When a client has asked the relay, in a RELAY_BEGIN cell, to connect
- * to a given server by hostname. This happens via dns_resolve().
- * <li>When a client has asked the relay, in a RELAY_RESOLVE cell, to look
- * up a given server's IP address(es) by hostname. This also happens via
- * dns_resolve().
- * </ol>
- *
- * Each of these gets handled a little differently.
- *
- * To check for correctness, we look up some hostname we expect to exist and
- * have real entries, some hostnames which we expect to definitely not exist,
- * and some hostnames that we expect to probably not exist. If too many of
- * the hostnames that shouldn't exist do exist, that's a DNS hijacking
- * attempt. If too many of the hostnames that should exist have the same
- * addresses as the ones that shouldn't exist, that's a very bad DNS hijacking
- * attempt, or a very naughty captive portal. And if the hostnames that
- * should exist simply don't exist, we probably have a broken nameserver.
- *
- * To handle client requests, we first check our cache for answers. If there
- * isn't something up-to-date, we've got to launch A or AAAA requests as
- * appropriate. How we handle responses to those in particular is a bit
- * complex; see dns_lookup() and set_exitconn_info_from_resolve().
- *
- * When a lookup is finally complete, the inform_pending_connections()
- * function will tell all of the streams that have been waiting for the
- * resolve, by calling connection_exit_connect() if the client sent a
- * RELAY_BEGIN cell, and by calling send_resolved_cell() or
- * send_hostname_cell() if the client sent a RELAY_RESOLVE cell.
- **/
- #define DNS_PRIVATE
- #include "core/or/or.h"
- #include "core/or/circuitlist.h"
- #include "core/or/circuituse.h"
- #include "app/config/config.h"
- #include "core/mainloop/connection.h"
- #include "core/or/connection_edge.h"
- #include "feature/control/control.h"
- #include "lib/crypt_ops/crypto_rand.h"
- #include "feature/relay/dns.h"
- #include "core/mainloop/main.h"
- #include "core/or/policies.h"
- #include "core/or/relay.h"
- #include "feature/relay/router.h"
- #include "ht.h"
- #include "lib/sandbox/sandbox.h"
- #include "lib/evloop/compat_libevent.h"
- #include "core/or/edge_connection_st.h"
- #include "core/or/or_circuit_st.h"
- #ifdef HAVE_SYS_STAT_H
- #include <sys/stat.h>
- #endif
- #include <event2/event.h>
- #include <event2/dns.h>
- /** How long will we wait for an answer from the resolver before we decide
- * that the resolver is wedged? */
- #define RESOLVE_MAX_TIMEOUT 300
- /** Our evdns_base; this structure handles all our name lookups. */
- static struct evdns_base *the_evdns_base = NULL;
- /** Have we currently configured nameservers with eventdns? */
- static int nameservers_configured = 0;
- /** Did our most recent attempt to configure nameservers with eventdns fail? */
- static int nameserver_config_failed = 0;
- /** What was the resolv_conf fname we last used when configuring the
- * nameservers? Used to check whether we need to reconfigure. */
- static char *resolv_conf_fname = NULL;
- /** What was the mtime on the resolv.conf file we last used when configuring
- * the nameservers? Used to check whether we need to reconfigure. */
- static time_t resolv_conf_mtime = 0;
- static void purge_expired_resolves(time_t now);
- static void dns_found_answer(const char *address, uint8_t query_type,
- int dns_answer,
- const tor_addr_t *addr,
- const char *hostname,
- uint32_t ttl);
- static void add_wildcarded_test_address(const char *address);
- static int configure_nameservers(int force);
- static int answer_is_wildcarded(const char *ip);
- static int evdns_err_is_transient(int err);
- static void inform_pending_connections(cached_resolve_t *resolve);
- static void make_pending_resolve_cached(cached_resolve_t *cached);
- #ifdef DEBUG_DNS_CACHE
- static void assert_cache_ok_(void);
- #define assert_cache_ok() assert_cache_ok_()
- #else
- #define assert_cache_ok() STMT_NIL
- #endif /* defined(DEBUG_DNS_CACHE) */
- static void assert_resolve_ok(cached_resolve_t *resolve);
- /** Hash table of cached_resolve objects. */
- static HT_HEAD(cache_map, cached_resolve_t) cache_root;
- /** Global: how many IPv6 requests have we made in all? */
- static uint64_t n_ipv6_requests_made = 0;
- /** Global: how many IPv6 requests have timed out? */
- static uint64_t n_ipv6_timeouts = 0;
- /** Global: Do we think that IPv6 DNS is broken? */
- static int dns_is_broken_for_ipv6 = 0;
- /** Function to compare hashed resolves on their addresses; used to
- * implement hash tables. */
- static inline int
- cached_resolves_eq(cached_resolve_t *a, cached_resolve_t *b)
- {
- /* make this smarter one day? */
- assert_resolve_ok(a); // Not b; b may be just a search.
- return !strncmp(a->address, b->address, MAX_ADDRESSLEN);
- }
- /** Hash function for cached_resolve objects */
- static inline unsigned int
- cached_resolve_hash(cached_resolve_t *a)
- {
- return (unsigned) siphash24g((const uint8_t*)a->address, strlen(a->address));
- }
- HT_PROTOTYPE(cache_map, cached_resolve_t, node, cached_resolve_hash,
- cached_resolves_eq)
- HT_GENERATE2(cache_map, cached_resolve_t, node, cached_resolve_hash,
- cached_resolves_eq, 0.6, tor_reallocarray_, tor_free_)
- /** Initialize the DNS cache. */
- static void
- init_cache_map(void)
- {
- HT_INIT(cache_map, &cache_root);
- }
- /** Helper: called by eventdns when eventdns wants to log something. */
- static void
- evdns_log_cb(int warn, const char *msg)
- {
- const char *cp;
- static int all_down = 0;
- int severity = warn ? LOG_WARN : LOG_INFO;
- if (!strcmpstart(msg, "Resolve requested for") &&
- get_options()->SafeLogging) {
- log_info(LD_EXIT, "eventdns: Resolve requested.");
- return;
- } else if (!strcmpstart(msg, "Search: ")) {
- return;
- }
- if (!strcmpstart(msg, "Nameserver ") && (cp=strstr(msg, " has failed: "))) {
- char *ns = tor_strndup(msg+11, cp-(msg+11));
- const char *colon = strchr(cp, ':');
- tor_assert(colon);
- const char *err = colon+2;
- /* Don't warn about a single failed nameserver; we'll warn with 'all
- * nameservers have failed' if we're completely out of nameservers;
- * otherwise, the situation is tolerable. */
- severity = LOG_INFO;
- control_event_server_status(LOG_NOTICE,
- "NAMESERVER_STATUS NS=%s STATUS=DOWN ERR=%s",
- ns, escaped(err));
- tor_free(ns);
- } else if (!strcmpstart(msg, "Nameserver ") &&
- (cp=strstr(msg, " is back up"))) {
- char *ns = tor_strndup(msg+11, cp-(msg+11));
- severity = (all_down && warn) ? LOG_NOTICE : LOG_INFO;
- all_down = 0;
- control_event_server_status(LOG_NOTICE,
- "NAMESERVER_STATUS NS=%s STATUS=UP", ns);
- tor_free(ns);
- } else if (!strcmp(msg, "All nameservers have failed")) {
- control_event_server_status(LOG_WARN, "NAMESERVER_ALL_DOWN");
- all_down = 1;
- } else if (!strcmpstart(msg, "Address mismatch on received DNS")) {
- static ratelim_t mismatch_limit = RATELIM_INIT(3600);
- const char *src = strstr(msg, " Apparent source");
- if (!src || get_options()->SafeLogging) {
- src = "";
- }
- log_fn_ratelim(&mismatch_limit, severity, LD_EXIT,
- "eventdns: Received a DNS packet from "
- "an IP address to which we did not send a request. This "
- "could be a DNS spoofing attempt, or some kind of "
- "misconfiguration.%s", src);
- return;
- }
- tor_log(severity, LD_EXIT, "eventdns: %s", msg);
- }
- /** Helper: passed to eventdns.c as a callback so it can generate random
- * numbers for transaction IDs and 0x20-hack coding. */
- static void
- dns_randfn_(char *b, size_t n)
- {
- crypto_rand(b,n);
- }
- /** Initialize the DNS subsystem; called by the OR process. */
- int
- dns_init(void)
- {
- init_cache_map();
- evdns_set_random_bytes_fn(dns_randfn_);
- if (server_mode(get_options())) {
- int r = configure_nameservers(1);
- return r;
- }
- return 0;
- }
- /** Called when DNS-related options change (or may have changed). Returns -1
- * on failure, 0 on success. */
- int
- dns_reset(void)
- {
- const or_options_t *options = get_options();
- if (! server_mode(options)) {
- if (!the_evdns_base) {
- if (!(the_evdns_base = evdns_base_new(tor_libevent_get_base(), 0))) {
- log_err(LD_BUG, "Couldn't create an evdns_base");
- return -1;
- }
- }
- evdns_base_clear_nameservers_and_suspend(the_evdns_base);
- evdns_base_search_clear(the_evdns_base);
- nameservers_configured = 0;
- tor_free(resolv_conf_fname);
- resolv_conf_mtime = 0;
- } else {
- if (configure_nameservers(0) < 0) {
- return -1;
- }
- }
- return 0;
- }
- /** Return true iff the most recent attempt to initialize the DNS subsystem
- * failed. */
- int
- has_dns_init_failed(void)
- {
- return nameserver_config_failed;
- }
- /** Helper: Given a TTL from a DNS response, determine what TTL to give the
- * OP that asked us to resolve it, and how long to cache that record
- * ourselves. */
- uint32_t
- dns_clip_ttl(uint32_t ttl)
- {
- /* This logic is a defense against "DefectTor" DNS-based traffic
- * confirmation attacks, as in https://nymity.ch/tor-dns/tor-dns.pdf .
- * We only give two values: a "low" value and a "high" value.
- */
- if (ttl < MIN_DNS_TTL_AT_EXIT)
- return MIN_DNS_TTL_AT_EXIT;
- else
- return MAX_DNS_TTL_AT_EXIT;
- }
- /** Helper: free storage held by an entry in the DNS cache. */
- static void
- free_cached_resolve_(cached_resolve_t *r)
- {
- if (!r)
- return;
- while (r->pending_connections) {
- pending_connection_t *victim = r->pending_connections;
- r->pending_connections = victim->next;
- tor_free(victim);
- }
- if (r->res_status_hostname == RES_STATUS_DONE_OK)
- tor_free(r->result_ptr.hostname);
- r->magic = 0xFF00FF00;
- tor_free(r);
- }
- /** Compare two cached_resolve_t pointers by expiry time, and return
- * less-than-zero, zero, or greater-than-zero as appropriate. Used for
- * the priority queue implementation. */
- static int
- compare_cached_resolves_by_expiry_(const void *_a, const void *_b)
- {
- const cached_resolve_t *a = _a, *b = _b;
- if (a->expire < b->expire)
- return -1;
- else if (a->expire == b->expire)
- return 0;
- else
- return 1;
- }
- /** Priority queue of cached_resolve_t objects to let us know when they
- * will expire. */
- static smartlist_t *cached_resolve_pqueue = NULL;
- static void
- cached_resolve_add_answer(cached_resolve_t *resolve,
- int query_type,
- int dns_result,
- const tor_addr_t *answer_addr,
- const char *answer_hostname,
- uint32_t ttl)
- {
- if (query_type == DNS_PTR) {
- if (resolve->res_status_hostname != RES_STATUS_INFLIGHT)
- return;
- if (dns_result == DNS_ERR_NONE && answer_hostname) {
- resolve->result_ptr.hostname = tor_strdup(answer_hostname);
- resolve->res_status_hostname = RES_STATUS_DONE_OK;
- } else {
- resolve->result_ptr.err_hostname = dns_result;
- resolve->res_status_hostname = RES_STATUS_DONE_ERR;
- }
- resolve->ttl_hostname = ttl;
- } else if (query_type == DNS_IPv4_A) {
- if (resolve->res_status_ipv4 != RES_STATUS_INFLIGHT)
- return;
- if (dns_result == DNS_ERR_NONE && answer_addr &&
- tor_addr_family(answer_addr) == AF_INET) {
- resolve->result_ipv4.addr_ipv4 = tor_addr_to_ipv4h(answer_addr);
- resolve->res_status_ipv4 = RES_STATUS_DONE_OK;
- } else {
- resolve->result_ipv4.err_ipv4 = dns_result;
- resolve->res_status_ipv4 = RES_STATUS_DONE_ERR;
- }
- resolve->ttl_ipv4 = ttl;
- } else if (query_type == DNS_IPv6_AAAA) {
- if (resolve->res_status_ipv6 != RES_STATUS_INFLIGHT)
- return;
- if (dns_result == DNS_ERR_NONE && answer_addr &&
- tor_addr_family(answer_addr) == AF_INET6) {
- memcpy(&resolve->result_ipv6.addr_ipv6,
- tor_addr_to_in6(answer_addr),
- sizeof(struct in6_addr));
- resolve->res_status_ipv6 = RES_STATUS_DONE_OK;
- } else {
- resolve->result_ipv6.err_ipv6 = dns_result;
- resolve->res_status_ipv6 = RES_STATUS_DONE_ERR;
- }
- resolve->ttl_ipv6 = ttl;
- }
- }
- /** Return true iff there are no in-flight requests for <b>resolve</b>. */
- static int
- cached_resolve_have_all_answers(const cached_resolve_t *resolve)
- {
- return (resolve->res_status_ipv4 != RES_STATUS_INFLIGHT &&
- resolve->res_status_ipv6 != RES_STATUS_INFLIGHT &&
- resolve->res_status_hostname != RES_STATUS_INFLIGHT);
- }
- /** Set an expiry time for a cached_resolve_t, and add it to the expiry
- * priority queue */
- static void
- set_expiry(cached_resolve_t *resolve, time_t expires)
- {
- tor_assert(resolve && resolve->expire == 0);
- if (!cached_resolve_pqueue)
- cached_resolve_pqueue = smartlist_new();
- resolve->expire = expires;
- smartlist_pqueue_add(cached_resolve_pqueue,
- compare_cached_resolves_by_expiry_,
- offsetof(cached_resolve_t, minheap_idx),
- resolve);
- }
- /** Free all storage held in the DNS cache and related structures. */
- void
- dns_free_all(void)
- {
- cached_resolve_t **ptr, **next, *item;
- assert_cache_ok();
- if (cached_resolve_pqueue) {
- SMARTLIST_FOREACH(cached_resolve_pqueue, cached_resolve_t *, res,
- {
- if (res->state == CACHE_STATE_DONE)
- free_cached_resolve_(res);
- });
- }
- for (ptr = HT_START(cache_map, &cache_root); ptr != NULL; ptr = next) {
- item = *ptr;
- next = HT_NEXT_RMV(cache_map, &cache_root, ptr);
- free_cached_resolve_(item);
- }
- HT_CLEAR(cache_map, &cache_root);
- smartlist_free(cached_resolve_pqueue);
- cached_resolve_pqueue = NULL;
- tor_free(resolv_conf_fname);
- }
- /** Remove every cached_resolve whose <b>expire</b> time is before or
- * equal to <b>now</b> from the cache. */
- static void
- purge_expired_resolves(time_t now)
- {
- cached_resolve_t *resolve, *removed;
- pending_connection_t *pend;
- edge_connection_t *pendconn;
- assert_cache_ok();
- if (!cached_resolve_pqueue)
- return;
- while (smartlist_len(cached_resolve_pqueue)) {
- resolve = smartlist_get(cached_resolve_pqueue, 0);
- if (resolve->expire > now)
- break;
- smartlist_pqueue_pop(cached_resolve_pqueue,
- compare_cached_resolves_by_expiry_,
- offsetof(cached_resolve_t, minheap_idx));
- if (resolve->state == CACHE_STATE_PENDING) {
- log_debug(LD_EXIT,
- "Expiring a dns resolve %s that's still pending. Forgot to "
- "cull it? DNS resolve didn't tell us about the timeout?",
- escaped_safe_str(resolve->address));
- } else if (resolve->state == CACHE_STATE_CACHED) {
- log_debug(LD_EXIT,
- "Forgetting old cached resolve (address %s, expires %lu)",
- escaped_safe_str(resolve->address),
- (unsigned long)resolve->expire);
- tor_assert(!resolve->pending_connections);
- } else {
- tor_assert(resolve->state == CACHE_STATE_DONE);
- tor_assert(!resolve->pending_connections);
- }
- if (resolve->pending_connections) {
- log_debug(LD_EXIT,
- "Closing pending connections on timed-out DNS resolve!");
- while (resolve->pending_connections) {
- pend = resolve->pending_connections;
- resolve->pending_connections = pend->next;
- /* Connections should only be pending if they have no socket. */
- tor_assert(!SOCKET_OK(pend->conn->base_.s));
- pendconn = pend->conn;
- /* Prevent double-remove */
- pendconn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
- if (!pendconn->base_.marked_for_close) {
- connection_edge_end(pendconn, END_STREAM_REASON_TIMEOUT);
- circuit_detach_stream(circuit_get_by_edge_conn(pendconn), pendconn);
- connection_free_(TO_CONN(pendconn));
- }
- tor_free(pend);
- }
- }
- if (resolve->state == CACHE_STATE_CACHED ||
- resolve->state == CACHE_STATE_PENDING) {
- removed = HT_REMOVE(cache_map, &cache_root, resolve);
- if (removed != resolve) {
- log_err(LD_BUG, "The expired resolve we purged didn't match any in"
- " the cache. Tried to purge %s (%p); instead got %s (%p).",
- resolve->address, (void*)resolve,
- removed ? removed->address : "NULL", (void*)removed);
- }
- tor_assert(removed == resolve);
- } else {
- /* This should be in state DONE. Make sure it's not in the cache. */
- cached_resolve_t *tmp = HT_FIND(cache_map, &cache_root, resolve);
- tor_assert(tmp != resolve);
- }
- if (resolve->res_status_hostname == RES_STATUS_DONE_OK)
- tor_free(resolve->result_ptr.hostname);
- resolve->magic = 0xF0BBF0BB;
- tor_free(resolve);
- }
- assert_cache_ok();
- }
- /* argument for send_resolved_cell only, meaning "let the answer type be ipv4
- * or ipv6 depending on the connection's address". */
- #define RESOLVED_TYPE_AUTO 0xff
- /** Send a response to the RESOLVE request of a connection.
- * <b>answer_type</b> must be one of
- * RESOLVED_TYPE_(AUTO|ERROR|ERROR_TRANSIENT|).
- *
- * If <b>circ</b> is provided, and we have a cached answer, send the
- * answer back along circ; otherwise, send the answer back along
- * <b>conn</b>'s attached circuit.
- */
- MOCK_IMPL(STATIC void,
- send_resolved_cell,(edge_connection_t *conn, uint8_t answer_type,
- const cached_resolve_t *resolved))
- {
- char buf[RELAY_PAYLOAD_SIZE], *cp = buf;
- size_t buflen = 0;
- uint32_t ttl;
- buf[0] = answer_type;
- ttl = dns_clip_ttl(conn->address_ttl);
- switch (answer_type)
- {
- case RESOLVED_TYPE_AUTO:
- if (resolved && resolved->res_status_ipv4 == RES_STATUS_DONE_OK) {
- cp[0] = RESOLVED_TYPE_IPV4;
- cp[1] = 4;
- set_uint32(cp+2, htonl(resolved->result_ipv4.addr_ipv4));
- set_uint32(cp+6, htonl(ttl));
- cp += 10;
- }
- if (resolved && resolved->res_status_ipv6 == RES_STATUS_DONE_OK) {
- const uint8_t *bytes = resolved->result_ipv6.addr_ipv6.s6_addr;
- cp[0] = RESOLVED_TYPE_IPV6;
- cp[1] = 16;
- memcpy(cp+2, bytes, 16);
- set_uint32(cp+18, htonl(ttl));
- cp += 22;
- }
- if (cp != buf) {
- buflen = cp - buf;
- break;
- } else {
- answer_type = RESOLVED_TYPE_ERROR;
- /* fall through. */
- }
- /* Falls through. */
- case RESOLVED_TYPE_ERROR_TRANSIENT:
- case RESOLVED_TYPE_ERROR:
- {
- const char *errmsg = "Error resolving hostname";
- size_t msglen = strlen(errmsg);
- buf[0] = answer_type;
- buf[1] = msglen;
- strlcpy(buf+2, errmsg, sizeof(buf)-2);
- set_uint32(buf+2+msglen, htonl(ttl));
- buflen = 6+msglen;
- break;
- }
- default:
- tor_assert(0);
- return;
- }
- // log_notice(LD_EXIT, "Sending a regular RESOLVED reply: ");
- connection_edge_send_command(conn, RELAY_COMMAND_RESOLVED, buf, buflen);
- }
- /** Send a response to the RESOLVE request of a connection for an in-addr.arpa
- * address on connection <b>conn</b> which yielded the result <b>hostname</b>.
- * The answer type will be RESOLVED_HOSTNAME.
- *
- * If <b>circ</b> is provided, and we have a cached answer, send the
- * answer back along circ; otherwise, send the answer back along
- * <b>conn</b>'s attached circuit.
- */
- MOCK_IMPL(STATIC void,
- send_resolved_hostname_cell,(edge_connection_t *conn,
- const char *hostname))
- {
- char buf[RELAY_PAYLOAD_SIZE];
- size_t buflen;
- uint32_t ttl;
- size_t namelen = strlen(hostname);
- tor_assert(hostname);
- tor_assert(namelen < 256);
- ttl = dns_clip_ttl(conn->address_ttl);
- buf[0] = RESOLVED_TYPE_HOSTNAME;
- buf[1] = (uint8_t)namelen;
- memcpy(buf+2, hostname, namelen);
- set_uint32(buf+2+namelen, htonl(ttl));
- buflen = 2+namelen+4;
- // log_notice(LD_EXIT, "Sending a reply RESOLVED reply: %s", hostname);
- connection_edge_send_command(conn, RELAY_COMMAND_RESOLVED, buf, buflen);
- // log_notice(LD_EXIT, "Sent");
- }
- /** See if we have a cache entry for <b>exitconn</b>-\>address. If so,
- * if resolve valid, put it into <b>exitconn</b>-\>addr and return 1.
- * If resolve failed, free exitconn and return -1.
- *
- * (For EXIT_PURPOSE_RESOLVE connections, send back a RESOLVED error cell
- * on returning -1. For EXIT_PURPOSE_CONNECT connections, there's no
- * need to send back an END cell, since connection_exit_begin_conn will
- * do that for us.)
- *
- * If we have a cached answer, send the answer back along <b>exitconn</b>'s
- * circuit.
- *
- * Else, if seen before and pending, add conn to the pending list,
- * and return 0.
- *
- * Else, if not seen before, add conn to pending list, hand to
- * dns farm, and return 0.
- *
- * Exitconn's on_circuit field must be set, but exitconn should not
- * yet be linked onto the n_streams/resolving_streams list of that circuit.
- * On success, link the connection to n_streams if it's an exit connection.
- * On "pending", link the connection to resolving streams. Otherwise,
- * clear its on_circuit field.
- */
- int
- dns_resolve(edge_connection_t *exitconn)
- {
- or_circuit_t *oncirc = TO_OR_CIRCUIT(exitconn->on_circuit);
- int is_resolve, r;
- int made_connection_pending = 0;
- char *hostname = NULL;
- cached_resolve_t *resolve = NULL;
- is_resolve = exitconn->base_.purpose == EXIT_PURPOSE_RESOLVE;
- r = dns_resolve_impl(exitconn, is_resolve, oncirc, &hostname,
- &made_connection_pending, &resolve);
- switch (r) {
- case 1:
- /* We got an answer without a lookup -- either the answer was
- * cached, or it was obvious (like an IP address). */
- if (is_resolve) {
- /* Send the answer back right now, and detach. */
- if (hostname)
- send_resolved_hostname_cell(exitconn, hostname);
- else
- send_resolved_cell(exitconn, RESOLVED_TYPE_AUTO, resolve);
- exitconn->on_circuit = NULL;
- } else {
- /* Add to the n_streams list; the calling function will send back a
- * connected cell. */
- exitconn->next_stream = oncirc->n_streams;
- oncirc->n_streams = exitconn;
- }
- break;
- case 0:
- /* The request is pending: add the connection into the linked list of
- * resolving_streams on this circuit. */
- exitconn->base_.state = EXIT_CONN_STATE_RESOLVING;
- exitconn->next_stream = oncirc->resolving_streams;
- oncirc->resolving_streams = exitconn;
- break;
- case -2:
- case -1:
- /* The request failed before it could start: cancel this connection,
- * and stop everybody waiting for the same connection. */
- if (is_resolve) {
- send_resolved_cell(exitconn,
- (r == -1) ? RESOLVED_TYPE_ERROR : RESOLVED_TYPE_ERROR_TRANSIENT,
- NULL);
- }
- exitconn->on_circuit = NULL;
- dns_cancel_pending_resolve(exitconn->base_.address);
- if (!made_connection_pending && !exitconn->base_.marked_for_close) {
- /* If we made the connection pending, then we freed it already in
- * dns_cancel_pending_resolve(). If we marked it for close, it'll
- * get freed from the main loop. Otherwise, can free it now. */
- connection_free_(TO_CONN(exitconn));
- }
- break;
- default:
- tor_assert(0);
- }
- tor_free(hostname);
- return r;
- }
- /** Helper function for dns_resolve: same functionality, but does not handle:
- * - marking connections on error and clearing their on_circuit
- * - linking connections to n_streams/resolving_streams,
- * - sending resolved cells if we have an answer/error right away,
- *
- * Return -2 on a transient error. If it's a reverse resolve and it's
- * successful, sets *<b>hostname_out</b> to a newly allocated string
- * holding the cached reverse DNS value.
- *
- * Set *<b>made_connection_pending_out</b> to true if we have placed
- * <b>exitconn</b> on the list of pending connections for some resolve; set it
- * to false otherwise.
- *
- * Set *<b>resolve_out</b> to a cached resolve, if we found one.
- */
- MOCK_IMPL(STATIC int,
- dns_resolve_impl,(edge_connection_t *exitconn, int is_resolve,
- or_circuit_t *oncirc, char **hostname_out,
- int *made_connection_pending_out,
- cached_resolve_t **resolve_out))
- {
- cached_resolve_t *resolve;
- cached_resolve_t search;
- pending_connection_t *pending_connection;
- int is_reverse = 0;
- tor_addr_t addr;
- time_t now = time(NULL);
- int r;
- assert_connection_ok(TO_CONN(exitconn), 0);
- tor_assert(!SOCKET_OK(exitconn->base_.s));
- assert_cache_ok();
- tor_assert(oncirc);
- *made_connection_pending_out = 0;
- /* first check if exitconn->base_.address is an IP. If so, we already
- * know the answer. */
- if (tor_addr_parse(&addr, exitconn->base_.address) >= 0) {
- if (tor_addr_family(&addr) == AF_INET ||
- tor_addr_family(&addr) == AF_INET6) {
- tor_addr_copy(&exitconn->base_.addr, &addr);
- exitconn->address_ttl = DEFAULT_DNS_TTL;
- return 1;
- } else {
- /* XXXX unspec? Bogus? */
- return -1;
- }
- }
- /* If we're a non-exit, don't even do DNS lookups. */
- if (router_my_exit_policy_is_reject_star())
- return -1;
- if (address_is_invalid_destination(exitconn->base_.address, 0)) {
- tor_log(LOG_PROTOCOL_WARN, LD_EXIT,
- "Rejecting invalid destination address %s",
- escaped_safe_str(exitconn->base_.address));
- return -1;
- }
- /* then take this opportunity to see if there are any expired
- * resolves in the hash table. */
- purge_expired_resolves(now);
- /* lower-case exitconn->base_.address, so it's in canonical form */
- tor_strlower(exitconn->base_.address);
- /* Check whether this is a reverse lookup. If it's malformed, or it's a
- * .in-addr.arpa address but this isn't a resolve request, kill the
- * connection.
- */
- if ((r = tor_addr_parse_PTR_name(&addr, exitconn->base_.address,
- AF_UNSPEC, 0)) != 0) {
- if (r == 1) {
- is_reverse = 1;
- if (tor_addr_is_internal(&addr, 0)) /* internal address? */
- return -1;
- }
- if (!is_reverse || !is_resolve) {
- if (!is_reverse)
- log_info(LD_EXIT, "Bad .in-addr.arpa address \"%s\"; sending error.",
- escaped_safe_str(exitconn->base_.address));
- else if (!is_resolve)
- log_info(LD_EXIT,
- "Attempt to connect to a .in-addr.arpa address \"%s\"; "
- "sending error.",
- escaped_safe_str(exitconn->base_.address));
- return -1;
- }
- //log_notice(LD_EXIT, "Looks like an address %s",
- //exitconn->base_.address);
- }
- exitconn->is_reverse_dns_lookup = is_reverse;
- /* now check the hash table to see if 'address' is already there. */
- strlcpy(search.address, exitconn->base_.address, sizeof(search.address));
- resolve = HT_FIND(cache_map, &cache_root, &search);
- if (resolve && resolve->expire > now) { /* already there */
- switch (resolve->state) {
- case CACHE_STATE_PENDING:
- /* add us to the pending list */
- pending_connection = tor_malloc_zero(
- sizeof(pending_connection_t));
- pending_connection->conn = exitconn;
- pending_connection->next = resolve->pending_connections;
- resolve->pending_connections = pending_connection;
- *made_connection_pending_out = 1;
- log_debug(LD_EXIT,"Connection (fd "TOR_SOCKET_T_FORMAT") waiting "
- "for pending DNS resolve of %s", exitconn->base_.s,
- escaped_safe_str(exitconn->base_.address));
- return 0;
- case CACHE_STATE_CACHED:
- log_debug(LD_EXIT,"Connection (fd "TOR_SOCKET_T_FORMAT") found "
- "cached answer for %s",
- exitconn->base_.s,
- escaped_safe_str(resolve->address));
- *resolve_out = resolve;
- return set_exitconn_info_from_resolve(exitconn, resolve, hostname_out);
- case CACHE_STATE_DONE:
- log_err(LD_BUG, "Found a 'DONE' dns resolve still in the cache.");
- tor_fragile_assert();
- }
- tor_assert(0);
- }
- tor_assert(!resolve);
- /* not there, need to add it */
- resolve = tor_malloc_zero(sizeof(cached_resolve_t));
- resolve->magic = CACHED_RESOLVE_MAGIC;
- resolve->state = CACHE_STATE_PENDING;
- resolve->minheap_idx = -1;
- strlcpy(resolve->address, exitconn->base_.address, sizeof(resolve->address));
- /* add this connection to the pending list */
- pending_connection = tor_malloc_zero(sizeof(pending_connection_t));
- pending_connection->conn = exitconn;
- resolve->pending_connections = pending_connection;
- *made_connection_pending_out = 1;
- /* Add this resolve to the cache and priority queue. */
- HT_INSERT(cache_map, &cache_root, resolve);
- set_expiry(resolve, now + RESOLVE_MAX_TIMEOUT);
- log_debug(LD_EXIT,"Launching %s.",
- escaped_safe_str(exitconn->base_.address));
- assert_cache_ok();
- return launch_resolve(resolve);
- }
- /** Given an exit connection <b>exitconn</b>, and a cached_resolve_t
- * <b>resolve</b> whose DNS lookups have all either succeeded or failed,
- * update the appropriate fields (address_ttl and addr) of <b>exitconn</b>.
- *
- * The logic can be complicated here, since we might have launched both
- * an A lookup and an AAAA lookup, and since either of those might have
- * succeeded or failed, and since we want to answer a RESOLVE cell with
- * a full answer but answer a BEGIN cell with whatever answer the client
- * would accept <i>and</i> we could still connect to.
- *
- * If this is a reverse lookup, set *<b>hostname_out</b> to a newly allocated
- * copy of the name resulting hostname.
- *
- * Return -2 on a transient error, -1 on a permenent error, and 1 on
- * a successful lookup.
- */
- MOCK_IMPL(STATIC int,
- set_exitconn_info_from_resolve,(edge_connection_t *exitconn,
- const cached_resolve_t *resolve,
- char **hostname_out))
- {
- int ipv4_ok, ipv6_ok, answer_with_ipv4, r;
- uint32_t begincell_flags;
- const int is_resolve = exitconn->base_.purpose == EXIT_PURPOSE_RESOLVE;
- tor_assert(exitconn);
- tor_assert(resolve);
- if (exitconn->is_reverse_dns_lookup) {
- exitconn->address_ttl = resolve->ttl_hostname;
- if (resolve->res_status_hostname == RES_STATUS_DONE_OK) {
- *hostname_out = tor_strdup(resolve->result_ptr.hostname);
- return 1;
- } else {
- return -1;
- }
- }
- /* If we're here then the connection wants one or either of ipv4, ipv6, and
- * we can give it one or both. */
- if (is_resolve) {
- begincell_flags = BEGIN_FLAG_IPV6_OK;
- } else {
- begincell_flags = exitconn->begincell_flags;
- }
- ipv4_ok = (resolve->res_status_ipv4 == RES_STATUS_DONE_OK) &&
- ! (begincell_flags & BEGIN_FLAG_IPV4_NOT_OK);
- ipv6_ok = (resolve->res_status_ipv6 == RES_STATUS_DONE_OK) &&
- (begincell_flags & BEGIN_FLAG_IPV6_OK) &&
- get_options()->IPv6Exit;
- /* Now decide which one to actually give. */
- if (ipv4_ok && ipv6_ok && is_resolve) {
- answer_with_ipv4 = 1;
- } else if (ipv4_ok && ipv6_ok) {
- /* If we have both, see if our exit policy has an opinion. */
- const uint16_t port = exitconn->base_.port;
- int ipv4_allowed, ipv6_allowed;
- tor_addr_t a4, a6;
- tor_addr_from_ipv4h(&a4, resolve->result_ipv4.addr_ipv4);
- tor_addr_from_in6(&a6, &resolve->result_ipv6.addr_ipv6);
- ipv4_allowed = !router_compare_to_my_exit_policy(&a4, port);
- ipv6_allowed = !router_compare_to_my_exit_policy(&a6, port);
- if (ipv4_allowed && !ipv6_allowed) {
- answer_with_ipv4 = 1;
- } else if (ipv6_allowed && !ipv4_allowed) {
- answer_with_ipv4 = 0;
- } else {
- /* Our exit policy would permit both. Answer with whichever the user
- * prefers */
- answer_with_ipv4 = !(begincell_flags &
- BEGIN_FLAG_IPV6_PREFERRED);
- }
- } else {
- /* Otherwise if one is okay, send it back. */
- if (ipv4_ok) {
- answer_with_ipv4 = 1;
- } else if (ipv6_ok) {
- answer_with_ipv4 = 0;
- } else {
- /* Neither one was okay. Choose based on user preference. */
- answer_with_ipv4 = !(begincell_flags &
- BEGIN_FLAG_IPV6_PREFERRED);
- }
- }
- /* Finally, we write the answer back. */
- r = 1;
- if (answer_with_ipv4) {
- if (resolve->res_status_ipv4 == RES_STATUS_DONE_OK) {
- tor_addr_from_ipv4h(&exitconn->base_.addr,
- resolve->result_ipv4.addr_ipv4);
- } else {
- r = evdns_err_is_transient(resolve->result_ipv4.err_ipv4) ? -2 : -1;
- }
- exitconn->address_ttl = resolve->ttl_ipv4;
- } else {
- if (resolve->res_status_ipv6 == RES_STATUS_DONE_OK) {
- tor_addr_from_in6(&exitconn->base_.addr,
- &resolve->result_ipv6.addr_ipv6);
- } else {
- r = evdns_err_is_transient(resolve->result_ipv6.err_ipv6) ? -2 : -1;
- }
- exitconn->address_ttl = resolve->ttl_ipv6;
- }
- return r;
- }
- /** Log an error and abort if conn is waiting for a DNS resolve.
- */
- void
- assert_connection_edge_not_dns_pending(edge_connection_t *conn)
- {
- pending_connection_t *pend;
- cached_resolve_t search;
- #if 1
- cached_resolve_t *resolve;
- strlcpy(search.address, conn->base_.address, sizeof(search.address));
- resolve = HT_FIND(cache_map, &cache_root, &search);
- if (!resolve)
- return;
- for (pend = resolve->pending_connections; pend; pend = pend->next) {
- tor_assert(pend->conn != conn);
- }
- #else /* !(1) */
- cached_resolve_t **resolve;
- HT_FOREACH(resolve, cache_map, &cache_root) {
- for (pend = (*resolve)->pending_connections; pend; pend = pend->next) {
- tor_assert(pend->conn != conn);
- }
- }
- #endif /* 1 */
- }
- /** Log an error and abort if any connection waiting for a DNS resolve is
- * corrupted. */
- void
- assert_all_pending_dns_resolves_ok(void)
- {
- pending_connection_t *pend;
- cached_resolve_t **resolve;
- HT_FOREACH(resolve, cache_map, &cache_root) {
- for (pend = (*resolve)->pending_connections;
- pend;
- pend = pend->next) {
- assert_connection_ok(TO_CONN(pend->conn), 0);
- tor_assert(!SOCKET_OK(pend->conn->base_.s));
- tor_assert(!connection_in_array(TO_CONN(pend->conn)));
- }
- }
- }
- /** Remove <b>conn</b> from the list of connections waiting for conn-\>address.
- */
- void
- connection_dns_remove(edge_connection_t *conn)
- {
- pending_connection_t *pend, *victim;
- cached_resolve_t search;
- cached_resolve_t *resolve;
- tor_assert(conn->base_.type == CONN_TYPE_EXIT);
- tor_assert(conn->base_.state == EXIT_CONN_STATE_RESOLVING);
- strlcpy(search.address, conn->base_.address, sizeof(search.address));
- resolve = HT_FIND(cache_map, &cache_root, &search);
- if (!resolve) {
- log_notice(LD_BUG, "Address %s is not pending. Dropping.",
- escaped_safe_str(conn->base_.address));
- return;
- }
- tor_assert(resolve->pending_connections);
- assert_connection_ok(TO_CONN(conn),0);
- pend = resolve->pending_connections;
- if (pend->conn == conn) {
- resolve->pending_connections = pend->next;
- tor_free(pend);
- log_debug(LD_EXIT, "First connection (fd "TOR_SOCKET_T_FORMAT") no "
- "longer waiting for resolve of %s",
- conn->base_.s,
- escaped_safe_str(conn->base_.address));
- return;
- } else {
- for ( ; pend->next; pend = pend->next) {
- if (pend->next->conn == conn) {
- victim = pend->next;
- pend->next = victim->next;
- tor_free(victim);
- log_debug(LD_EXIT,
- "Connection (fd "TOR_SOCKET_T_FORMAT") no longer waiting "
- "for resolve of %s",
- conn->base_.s, escaped_safe_str(conn->base_.address));
- return; /* more are pending */
- }
- }
- log_warn(LD_BUG, "Connection (fd "TOR_SOCKET_T_FORMAT") was not waiting "
- "for a resolve of %s, but we tried to remove it.",
- conn->base_.s, escaped_safe_str(conn->base_.address));
- }
- }
- /** Mark all connections waiting for <b>address</b> for close. Then cancel
- * the resolve for <b>address</b> itself, and remove any cached results for
- * <b>address</b> from the cache.
- */
- MOCK_IMPL(void,
- dns_cancel_pending_resolve,(const char *address))
- {
- pending_connection_t *pend;
- cached_resolve_t search;
- cached_resolve_t *resolve, *tmp;
- edge_connection_t *pendconn;
- circuit_t *circ;
- strlcpy(search.address, address, sizeof(search.address));
- resolve = HT_FIND(cache_map, &cache_root, &search);
- if (!resolve)
- return;
- if (resolve->state != CACHE_STATE_PENDING) {
- /* We can get into this state if we never actually created the pending
- * resolve, due to finding an earlier cached error or something. Just
- * ignore it. */
- if (resolve->pending_connections) {
- log_warn(LD_BUG,
- "Address %s is not pending but has pending connections!",
- escaped_safe_str(address));
- tor_fragile_assert();
- }
- return;
- }
- if (!resolve->pending_connections) {
- log_warn(LD_BUG,
- "Address %s is pending but has no pending connections!",
- escaped_safe_str(address));
- tor_fragile_assert();
- return;
- }
- tor_assert(resolve->pending_connections);
- /* mark all pending connections to fail */
- log_debug(LD_EXIT,
- "Failing all connections waiting on DNS resolve of %s",
- escaped_safe_str(address));
- while (resolve->pending_connections) {
- pend = resolve->pending_connections;
- pend->conn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
- pendconn = pend->conn;
- assert_connection_ok(TO_CONN(pendconn), 0);
- tor_assert(!SOCKET_OK(pendconn->base_.s));
- if (!pendconn->base_.marked_for_close) {
- connection_edge_end(pendconn, END_STREAM_REASON_RESOLVEFAILED);
- }
- circ = circuit_get_by_edge_conn(pendconn);
- if (circ)
- circuit_detach_stream(circ, pendconn);
- if (!pendconn->base_.marked_for_close)
- connection_free_(TO_CONN(pendconn));
- resolve->pending_connections = pend->next;
- tor_free(pend);
- }
- tmp = HT_REMOVE(cache_map, &cache_root, resolve);
- if (tmp != resolve) {
- log_err(LD_BUG, "The cancelled resolve we purged didn't match any in"
- " the cache. Tried to purge %s (%p); instead got %s (%p).",
- resolve->address, (void*)resolve,
- tmp ? tmp->address : "NULL", (void*)tmp);
- }
- tor_assert(tmp == resolve);
- resolve->state = CACHE_STATE_DONE;
- }
- /** Return true iff <b>address</b> is one of the addresses we use to verify
- * that well-known sites aren't being hijacked by our DNS servers. */
- static inline int
- is_test_address(const char *address)
- {
- const or_options_t *options = get_options();
- return options->ServerDNSTestAddresses &&
- smartlist_contains_string_case(options->ServerDNSTestAddresses, address);
- }
- /** Called on the OR side when the eventdns library tells us the outcome of a
- * single DNS resolve: remember the answer, and tell all pending connections
- * about the result of the lookup if the lookup is now done. (<b>address</b>
- * is a NUL-terminated string containing the address to look up;
- * <b>query_type</b> is one of DNS_{IPv4_A,IPv6_AAAA,PTR}; <b>dns_answer</b>
- * is DNS_OK or one of DNS_ERR_*, <b>addr</b> is an IPv4 or IPv6 address if we
- * got one; <b>hostname</b> is a hostname fora PTR request if we got one, and
- * <b>ttl</b> is the time-to-live of this answer, in seconds.)
- */
- static void
- dns_found_answer(const char *address, uint8_t query_type,
- int dns_answer,
- const tor_addr_t *addr,
- const char *hostname, uint32_t ttl)
- {
- cached_resolve_t search;
- cached_resolve_t *resolve;
- assert_cache_ok();
- strlcpy(search.address, address, sizeof(search.address));
- resolve = HT_FIND(cache_map, &cache_root, &search);
- if (!resolve) {
- int is_test_addr = is_test_address(address);
- if (!is_test_addr)
- log_info(LD_EXIT,"Resolved unasked address %s; ignoring.",
- escaped_safe_str(address));
- return;
- }
- assert_resolve_ok(resolve);
- if (resolve->state != CACHE_STATE_PENDING) {
- /* XXXX Maybe update addr? or check addr for consistency? Or let
- * VALID replace FAILED? */
- int is_test_addr = is_test_address(address);
- if (!is_test_addr)
- log_notice(LD_EXIT,
- "Resolved %s which was already resolved; ignoring",
- escaped_safe_str(address));
- tor_assert(resolve->pending_connections == NULL);
- return;
- }
- cached_resolve_add_answer(resolve, query_type, dns_answer,
- addr, hostname, ttl);
- if (cached_resolve_have_all_answers(resolve)) {
- inform_pending_connections(resolve);
- make_pending_resolve_cached(resolve);
- }
- }
- /** Given a pending cached_resolve_t that we just finished resolving,
- * inform every connection that was waiting for the outcome of that
- * resolution.
- *
- * Do this by sending a RELAY_RESOLVED cell (if the pending stream had sent us
- * RELAY_RESOLVE cell), or by launching an exit connection (if the pending
- * stream had send us a RELAY_BEGIN cell).
- */
- static void
- inform_pending_connections(cached_resolve_t *resolve)
- {
- pending_connection_t *pend;
- edge_connection_t *pendconn;
- int r;
- while (resolve->pending_connections) {
- char *hostname = NULL;
- pend = resolve->pending_connections;
- pendconn = pend->conn; /* don't pass complex things to the
- connection_mark_for_close macro */
- assert_connection_ok(TO_CONN(pendconn),time(NULL));
- if (pendconn->base_.marked_for_close) {
- /* prevent double-remove. */
- pendconn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
- resolve->pending_connections = pend->next;
- tor_free(pend);
- continue;
- }
- r = set_exitconn_info_from_resolve(pendconn,
- resolve,
- &hostname);
- if (r < 0) {
- /* prevent double-remove. */
- pendconn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
- if (pendconn->base_.purpose == EXIT_PURPOSE_CONNECT) {
- connection_edge_end(pendconn, END_STREAM_REASON_RESOLVEFAILED);
- /* This detach must happen after we send the end cell. */
- circuit_detach_stream(circuit_get_by_edge_conn(pendconn), pendconn);
- } else {
- send_resolved_cell(pendconn, r == -1 ?
- RESOLVED_TYPE_ERROR : RESOLVED_TYPE_ERROR_TRANSIENT,
- NULL);
- /* This detach must happen after we send the resolved cell. */
- circuit_detach_stream(circuit_get_by_edge_conn(pendconn), pendconn);
- }
- connection_free_(TO_CONN(pendconn));
- } else {
- circuit_t *circ;
- if (pendconn->base_.purpose == EXIT_PURPOSE_CONNECT) {
- /* prevent double-remove. */
- pend->conn->base_.state = EXIT_CONN_STATE_CONNECTING;
- circ = circuit_get_by_edge_conn(pend->conn);
- tor_assert(circ);
- tor_assert(!CIRCUIT_IS_ORIGIN(circ));
- /* unlink pend->conn from resolving_streams, */
- circuit_detach_stream(circ, pend->conn);
- /* and link it to n_streams */
- pend->conn->next_stream = TO_OR_CIRCUIT(circ)->n_streams;
- pend->conn->on_circuit = circ;
- TO_OR_CIRCUIT(circ)->n_streams = pend->conn;
- connection_exit_connect(pend->conn);
- } else {
- /* prevent double-remove. This isn't really an accurate state,
- * but it does the right thing. */
- pendconn->base_.state = EXIT_CONN_STATE_RESOLVEFAILED;
- if (pendconn->is_reverse_dns_lookup)
- send_resolved_hostname_cell(pendconn, hostname);
- else
- send_resolved_cell(pendconn, RESOLVED_TYPE_AUTO, resolve);
- circ = circuit_get_by_edge_conn(pendconn);
- tor_assert(circ);
- circuit_detach_stream(circ, pendconn);
- connection_free_(TO_CONN(pendconn));
- }
- }
- resolve->pending_connections = pend->next;
- tor_free(pend);
- tor_free(hostname);
- }
- }
- /** Remove a pending cached_resolve_t from the hashtable, and add a
- * corresponding cached cached_resolve_t.
- *
- * This function is only necessary because of the perversity of our
- * cache timeout code; see inline comment for ideas on eliminating it.
- **/
- static void
- make_pending_resolve_cached(cached_resolve_t *resolve)
- {
- cached_resolve_t *removed;
- resolve->state = CACHE_STATE_DONE;
- removed = HT_REMOVE(cache_map, &cache_root, resolve);
- if (removed != resolve) {
- log_err(LD_BUG, "The pending resolve we found wasn't removable from"
- " the cache. Tried to purge %s (%p); instead got %s (%p).",
- resolve->address, (void*)resolve,
- removed ? removed->address : "NULL", (void*)removed);
- }
- assert_resolve_ok(resolve);
- assert_cache_ok();
- /* The resolve will eventually just hit the time-out in the expiry queue and
- * expire. See fd0bafb0dedc7e2 for a brief explanation of how this got that
- * way. XXXXX we could do better!*/
- {
- cached_resolve_t *new_resolve = tor_memdup(resolve,
- sizeof(cached_resolve_t));
- uint32_t ttl = UINT32_MAX;
- new_resolve->expire = 0; /* So that set_expiry won't croak. */
- if (resolve->res_status_hostname == RES_STATUS_DONE_OK)
- new_resolve->result_ptr.hostname =
- tor_strdup(resolve->result_ptr.hostname);
- new_resolve->state = CACHE_STATE_CACHED;
- assert_resolve_ok(new_resolve);
- HT_INSERT(cache_map, &cache_root, new_resolve);
- if ((resolve->res_status_ipv4 == RES_STATUS_DONE_OK ||
- resolve->res_status_ipv4 == RES_STATUS_DONE_ERR) &&
- resolve->ttl_ipv4 < ttl)
- ttl = resolve->ttl_ipv4;
- if ((resolve->res_status_ipv6 == RES_STATUS_DONE_OK ||
- resolve->res_status_ipv6 == RES_STATUS_DONE_ERR) &&
- resolve->ttl_ipv6 < ttl)
- ttl = resolve->ttl_ipv6;
- if ((resolve->res_status_hostname == RES_STATUS_DONE_OK ||
- resolve->res_status_hostname == RES_STATUS_DONE_ERR) &&
- resolve->ttl_hostname < ttl)
- ttl = resolve->ttl_hostname;
- set_expiry(new_resolve, time(NULL) + dns_clip_ttl(ttl));
- }
- assert_cache_ok();
- }
- /** Eventdns helper: return true iff the eventdns result <b>err</b> is
- * a transient failure. */
- static int
- evdns_err_is_transient(int err)
- {
- switch (err)
- {
- case DNS_ERR_SERVERFAILED:
- case DNS_ERR_TRUNCATED:
- case DNS_ERR_TIMEOUT:
- return 1;
- default:
- return 0;
- }
- }
- /** Configure eventdns nameservers if force is true, or if the configuration
- * has changed since the last time we called this function, or if we failed on
- * our last attempt. On Unix, this reads from /etc/resolv.conf or
- * options->ServerDNSResolvConfFile; on Windows, this reads from
- * options->ServerDNSResolvConfFile or the registry. Return 0 on success or
- * -1 on failure. */
- static int
- configure_nameservers(int force)
- {
- const or_options_t *options;
- const char *conf_fname;
- struct stat st;
- int r, flags;
- options = get_options();
- conf_fname = options->ServerDNSResolvConfFile;
- #ifndef _WIN32
- if (!conf_fname)
- conf_fname = "/etc/resolv.conf";
- #endif
- flags = DNS_OPTIONS_ALL;
- if (!the_evdns_base) {
- if (!(the_evdns_base = evdns_base_new(tor_libevent_get_base(), 0))) {
- log_err(LD_BUG, "Couldn't create an evdns_base");
- return -1;
- }
- }
- evdns_set_log_fn(evdns_log_cb);
- if (conf_fname) {
- log_debug(LD_FS, "stat()ing %s", conf_fname);
- if (stat(sandbox_intern_string(conf_fname), &st)) {
- log_warn(LD_EXIT, "Unable to stat resolver configuration in '%s': %s",
- conf_fname, strerror(errno));
- goto err;
- }
- if (!force && resolv_conf_fname && !strcmp(conf_fname,resolv_conf_fname)
- && st.st_mtime == resolv_conf_mtime) {
- log_info(LD_EXIT, "No change to '%s'", conf_fname);
- return 0;
- }
- if (nameservers_configured) {
- evdns_base_search_clear(the_evdns_base);
- evdns_base_clear_nameservers_and_suspend(the_evdns_base);
- }
- #if defined(DNS_OPTION_HOSTSFILE) && defined(USE_LIBSECCOMP)
- if (flags & DNS_OPTION_HOSTSFILE) {
- flags ^= DNS_OPTION_HOSTSFILE;
- log_debug(LD_FS, "Loading /etc/hosts");
- evdns_base_load_hosts(the_evdns_base,
- sandbox_intern_string("/etc/hosts"));
- }
- #endif /* defined(DNS_OPTION_HOSTSFILE) && defined(USE_LIBSECCOMP) */
- log_info(LD_EXIT, "Parsing resolver configuration in '%s'", conf_fname);
- if ((r = evdns_base_resolv_conf_parse(the_evdns_base, flags,
- sandbox_intern_string(conf_fname)))) {
- log_warn(LD_EXIT, "Unable to parse '%s', or no nameservers in '%s' (%d)",
- conf_fname, conf_fname, r);
- goto err;
- }
- if (evdns_base_count_nameservers(the_evdns_base) == 0) {
- log_warn(LD_EXIT, "Unable to find any nameservers in '%s'.", conf_fname);
- goto err;
- }
- tor_free(resolv_conf_fname);
- resolv_conf_fname = tor_strdup(conf_fname);
- resolv_conf_mtime = st.st_mtime;
- if (nameservers_configured)
- evdns_base_resume(the_evdns_base);
- }
- #ifdef _WIN32
- else {
- if (nameservers_configured) {
- evdns_base_search_clear(the_evdns_base);
- evdns_base_clear_nameservers_and_suspend(the_evdns_base);
- }
- if (evdns_base_config_windows_nameservers(the_evdns_base)) {
- log_warn(LD_EXIT,"Could not config nameservers.");
- goto err;
- }
- if (evdns_base_count_nameservers(the_evdns_base) == 0) {
- log_warn(LD_EXIT, "Unable to find any platform nameservers in "
- "your Windows configuration.");
- goto err;
- }
- if (nameservers_configured)
- evdns_base_resume(the_evdns_base);
- tor_free(resolv_conf_fname);
- resolv_conf_mtime = 0;
- }
- #endif /* defined(_WIN32) */
- #define SET(k,v) evdns_base_set_option(the_evdns_base, (k), (v))
- // If we only have one nameserver, it does not make sense to back off
- // from it for a timeout. Unfortunately, the value for max-timeouts is
- // currently clamped by libevent to 255, but it does not hurt to set
- // it higher in case libevent gets a patch for this. Higher-than-
- // default maximum of 3 with multiple nameservers to avoid spuriously
- // marking one down on bursts of timeouts resulting from scans/attacks
- // against non-responding authoritative DNS servers.
- if (evdns_base_count_nameservers(the_evdns_base) == 1) {
- SET("max-timeouts:", "1000000");
- } else {
- SET("max-timeouts:", "10");
- }
- // Elongate the queue of maximum inflight dns requests, so if a bunch
- // remain pending at the resolver (happens commonly with Unbound) we won't
- // stall every other DNS request. This potentially means some wasted
- // CPU as there's a walk over a linear queue involved, but this is a
- // much better tradeoff compared to just failing DNS requests because
- // of a full queue.
- SET("max-inflight:", "8192");
- // Two retries at 5 and 10 seconds for bind9/named which relies on
- // clients to handle retries. Second retry for retried circuits with
- // extended 15 second timeout. Superfluous with local-system Unbound
- // instance--has its own elaborate retry scheme.
- SET("timeout:", "5");
- SET("attempts:","3");
- if (options->ServerDNSRandomizeCase)
- SET("randomize-case:", "1");
- else
- SET("randomize-case:", "0");
- #undef SET
- dns_servers_relaunch_checks();
- nameservers_configured = 1;
- if (nameserver_config_failed) {
- nameserver_config_failed = 0;
- /* XXX the three calls to republish the descriptor might be producing
- * descriptors that are only cosmetically different, especially on
- * non-exit relays! -RD */
- mark_my_descriptor_dirty("dns resolvers back");
- }
- return 0;
- err:
- nameservers_configured = 0;
- if (! nameserver_config_failed) {
- nameserver_config_failed = 1;
- mark_my_descriptor_dirty("dns resolvers failed");
- }
- return -1;
- }
- /** For eventdns: Called when we get an answer for a request we launched.
- * See eventdns.h for arguments; 'arg' holds the address we tried to resolve.
- */
- static void
- evdns_callback(int result, char type, int count, int ttl, void *addresses,
- void *arg)
- {
- char *arg_ = arg;
- uint8_t orig_query_type = arg_[0];
- char *string_address = arg_ + 1;
- tor_addr_t addr;
- const char *hostname = NULL;
- int was_wildcarded = 0;
- tor_addr_make_unspec(&addr);
- /* Keep track of whether IPv6 is working */
- if (type == DNS_IPv6_AAAA) {
- if (result == DNS_ERR_TIMEOUT) {
- ++n_ipv6_timeouts;
- }
- if (n_ipv6_timeouts > 10 &&
- n_ipv6_timeouts > n_ipv6_requests_made / 2) {
- if (! dns_is_broken_for_ipv6) {
- log_notice(LD_EXIT, "More than half of our IPv6 requests seem to "
- "have timed out. I'm going to assume I can't get AAAA "
- "responses.");
- dns_is_broken_for_ipv6 = 1;
- }
- }
- }
- if (result == DNS_ERR_NONE) {
- if (type == DNS_IPv4_A && count) {
- char answer_buf[INET_NTOA_BUF_LEN+1];
- char *escaped_address;
- uint32_t *addrs = addresses;
- tor_addr_from_ipv4n(&addr, addrs[0]);
- tor_addr_to_str(answer_buf, &addr, sizeof(answer_buf), 0);
- escaped_address = esc_for_log(string_address);
- if (answer_is_wildcarded(answer_buf)) {
- log_debug(LD_EXIT, "eventdns said that %s resolves to ISP-hijacked "
- "address %s; treating as a failure.",
- safe_str(escaped_address),
- escaped_safe_str(answer_buf));
- was_wildcarded = 1;
- tor_addr_make_unspec(&addr);
- result = DNS_ERR_NOTEXIST;
- } else {
- log_debug(LD_EXIT, "eventdns said that %s resolves to %s",
- safe_str(escaped_address),
- escaped_safe_str(answer_buf));
- }
- tor_free(escaped_address);
- } else if (type == DNS_IPv6_AAAA && count) {
- char answer_buf[TOR_ADDR_BUF_LEN];
- char *escaped_address;
- struct in6_addr *addrs = addresses;
- tor_addr_from_in6(&addr, &addrs[0]);
- tor_inet_ntop(AF_INET6, &addrs[0], answer_buf, sizeof(answer_buf));
- escaped_address = esc_for_log(string_address);
- if (answer_is_wildcarded(answer_buf)) {
- log_debug(LD_EXIT, "eventdns said that %s resolves to ISP-hijacked "
- "address %s; treating as a failure.",
- safe_str(escaped_address),
- escaped_safe_str(answer_buf));
- was_wildcarded = 1;
- tor_addr_make_unspec(&addr);
- result = DNS_ERR_NOTEXIST;
- } else {
- log_debug(LD_EXIT, "eventdns said that %s resolves to %s",
- safe_str(escaped_address),
- escaped_safe_str(answer_buf));
- }
- tor_free(escaped_address);
- } else if (type == DNS_PTR && count) {
- char *escaped_address;
- hostname = ((char**)addresses)[0];
- escaped_address = esc_for_log(string_address);
- log_debug(LD_EXIT, "eventdns said that %s resolves to %s",
- safe_str(escaped_address),
- escaped_safe_str(hostname));
- tor_free(escaped_address);
- } else if (count) {
- log_info(LD_EXIT, "eventdns returned only unrecognized answer types "
- " for %s.",
- escaped_safe_str(string_address));
- } else {
- log_info(LD_EXIT, "eventdns returned no addresses or error for %s.",
- escaped_safe_str(string_address));
- }
- }
- if (was_wildcarded) {
- if (is_test_address(string_address)) {
- /* Ick. We're getting redirected on known-good addresses. Our DNS
- * server must really hate us. */
- add_wildcarded_test_address(string_address);
- }
- }
- if (orig_query_type && type && orig_query_type != type) {
- log_warn(LD_BUG, "Weird; orig_query_type == %d but type == %d",
- (int)orig_query_type, (int)type);
- }
- if (result != DNS_ERR_SHUTDOWN)
- dns_found_answer(string_address, orig_query_type,
- result, &addr, hostname, ttl);
- tor_free(arg_);
- }
- /** Start a single DNS resolve for <b>address</b> (if <b>query_type</b> is
- * DNS_IPv4_A or DNS_IPv6_AAAA) <b>ptr_address</b> (if <b>query_type</b> is
- * DNS_PTR). Return 0 if we launched the request, -1 otherwise. */
- static int
- launch_one_resolve(const char *address, uint8_t query_type,
- const tor_addr_t *ptr_address)
- {
- const int options = get_options()->ServerDNSSearchDomains ? 0
- : DNS_QUERY_NO_SEARCH;
- const size_t addr_len = strlen(address);
- struct evdns_request *req = 0;
- char *addr = tor_malloc(addr_len + 2);
- addr[0] = (char) query_type;
- memcpy(addr+1, address, addr_len + 1);
- switch (query_type) {
- case DNS_IPv4_A:
- req = evdns_base_resolve_ipv4(the_evdns_base,
- address, options, evdns_callback, addr);
- break;
- case DNS_IPv6_AAAA:
- req = evdns_base_resolve_ipv6(the_evdns_base,
- address, options, evdns_callback, addr);
- ++n_ipv6_requests_made;
- break;
- case DNS_PTR:
- if (tor_addr_family(ptr_address) == AF_INET)
- req = evdns_base_resolve_reverse(the_evdns_base,
- tor_addr_to_in(ptr_address),
- DNS_QUERY_NO_SEARCH,
- evdns_callback, addr);
- else if (tor_addr_family(ptr_address) == AF_INET6)
- req = evdns_base_resolve_reverse_ipv6(the_evdns_base,
- tor_addr_to_in6(ptr_address),
- DNS_QUERY_NO_SEARCH,
- evdns_callback, addr);
- else
- log_warn(LD_BUG, "Called with PTR query and unexpected address family");
- break;
- default:
- log_warn(LD_BUG, "Called with unexpectd query type %d", (int)query_type);
- break;
- }
- if (req) {
- return 0;
- } else {
- tor_free(addr);
- return -1;
- }
- }
- /** For eventdns: start resolving as necessary to find the target for
- * <b>exitconn</b>. Returns -1 on error, -2 on transient error,
- * 0 on "resolve launched." */
- MOCK_IMPL(STATIC int,
- launch_resolve,(cached_resolve_t *resolve))
- {
- tor_addr_t a;
- int r;
- if (net_is_disabled())
- return -1;
- /* What? Nameservers not configured? Sounds like a bug. */
- if (!nameservers_configured) {
- log_warn(LD_EXIT, "(Harmless.) Nameservers not configured, but resolve "
- "launched. Configuring.");
- if (configure_nameservers(1) < 0) {
- return -1;
- }
- }
- r = tor_addr_parse_PTR_name(
- &a, resolve->address, AF_UNSPEC, 0);
- tor_assert(the_evdns_base);
- if (r == 0) {
- log_info(LD_EXIT, "Launching eventdns request for %s",
- escaped_safe_str(resolve->address));
- resolve->res_status_ipv4 = RES_STATUS_INFLIGHT;
- if (get_options()->IPv6Exit)
- resolve->res_status_ipv6 = RES_STATUS_INFLIGHT;
- if (launch_one_resolve(resolve->address, DNS_IPv4_A, NULL) < 0) {
- resolve->res_status_ipv4 = 0;
- r = -1;
- }
- if (r==0 && get_options()->IPv6Exit) {
- /* We ask for an IPv6 address for *everything*. */
- if (launch_one_resolve(resolve->address, DNS_IPv6_AAAA, NULL) < 0) {
- resolve->res_status_ipv6 = 0;
- r = -1;
- }
- }
- } else if (r == 1) {
- r = 0;
- log_info(LD_EXIT, "Launching eventdns reverse request for %s",
- escaped_safe_str(resolve->address));
- resolve->res_status_hostname = RES_STATUS_INFLIGHT;
- if (launch_one_resolve(resolve->address, DNS_PTR, &a) < 0) {
- resolve->res_status_hostname = 0;
- r = -1;
- }
- } else if (r == -1) {
- log_warn(LD_BUG, "Somehow a malformed in-addr.arpa address reached here.");
- }
- if (r < 0) {
- log_fn(LOG_PROTOCOL_WARN, LD_EXIT, "eventdns rejected address %s.",
- escaped_safe_str(resolve->address));
- }
- return r;
- }
- /** How many requests for bogus addresses have we launched so far? */
- static int n_wildcard_requests = 0;
- /** Map from dotted-quad IP address in response to an int holding how many
- * times we've seen it for a randomly generated (hopefully bogus) address. It
- * would be easier to use definitely-invalid addresses (as specified by
- * RFC2606), but see comment in dns_launch_wildcard_checks(). */
- static strmap_t *dns_wildcard_response_count = NULL;
- /** If present, a list of dotted-quad IP addresses that we are pretty sure our
- * nameserver wants to return in response to requests for nonexistent domains.
- */
- static smartlist_t *dns_wildcard_list = NULL;
- /** True iff we've logged about a single address getting wildcarded.
- * Subsequent warnings will be less severe. */
- static int dns_wildcard_one_notice_given = 0;
- /** True iff we've warned that our DNS server is wildcarding too many failures.
- */
- static int dns_wildcard_notice_given = 0;
- /** List of supposedly good addresses that are getting wildcarded to the
- * same addresses as nonexistent addresses. */
- static smartlist_t *dns_wildcarded_test_address_list = NULL;
- /** True iff we've warned about a test address getting wildcarded */
- static int dns_wildcarded_test_address_notice_given = 0;
- /** True iff all addresses seem to be getting wildcarded. */
- static int dns_is_completely_invalid = 0;
- /** Called when we see <b>id</b> (a dotted quad or IPv6 address) in response
- * to a request for a hopefully bogus address. */
- static void
- wildcard_increment_answer(const char *id)
- {
- int *ip;
- if (!dns_wildcard_response_count)
- dns_wildcard_response_count = strmap_new();
- ip = strmap_get(dns_wildcard_response_count, id); // may be null (0)
- if (!ip) {
- ip = tor_malloc_zero(sizeof(int));
- strmap_set(dns_wildcard_response_count, id, ip);
- }
- ++*ip;
- if (*ip > 5 && n_wildcard_requests > 10) {
- if (!dns_wildcard_list) dns_wildcard_list = smartlist_new();
- if (!smartlist_contains_string(dns_wildcard_list, id)) {
- tor_log(dns_wildcard_notice_given ? LOG_INFO : LOG_NOTICE, LD_EXIT,
- "Your DNS provider has given \"%s\" as an answer for %d different "
- "invalid addresses. Apparently they are hijacking DNS failures. "
- "I'll try to correct for this by treating future occurrences of "
- "\"%s\" as 'not found'.", id, *ip, id);
- smartlist_add_strdup(dns_wildcard_list, id);
- }
- if (!dns_wildcard_notice_given)
- control_event_server_status(LOG_NOTICE, "DNS_HIJACKED");
- dns_wildcard_notice_given = 1;
- }
- }
- /** Note that a single test address (one believed to be good) seems to be
- * getting redirected to the same IP as failures are. */
- static void
- add_wildcarded_test_address(const char *address)
- {
- int n, n_test_addrs;
- if (!dns_wildcarded_test_address_list)
- dns_wildcarded_test_address_list = smartlist_new();
- if (smartlist_contains_string_case(dns_wildcarded_test_address_list,
- address))
- return;
- n_test_addrs = get_options()->ServerDNSTestAddresses ?
- smartlist_len(get_options()->ServerDNSTestAddresses) : 0;
- smartlist_add_strdup(dns_wildcarded_test_address_list, address);
- n = smartlist_len(dns_wildcarded_test_address_list);
- if (n > n_test_addrs/2) {
- tor_log(dns_wildcarded_test_address_notice_given ? LOG_INFO : LOG_NOTICE,
- LD_EXIT, "Your DNS provider tried to redirect \"%s\" to a junk "
- "address. It has done this with %d test addresses so far. I'm "
- "going to stop being an exit node for now, since our DNS seems so "
- "broken.", address, n);
- if (!dns_is_completely_invalid) {
- dns_is_completely_invalid = 1;
- mark_my_descriptor_dirty("dns hijacking confirmed");
- }
- if (!dns_wildcarded_test_address_notice_given)
- control_event_server_status(LOG_WARN, "DNS_USELESS");
- dns_wildcarded_test_address_notice_given = 1;
- }
- }
- /** Callback function when we get an answer (possibly failing) for a request
- * for a (hopefully) nonexistent domain. */
- static void
- evdns_wildcard_check_callback(int result, char type, int count, int ttl,
- void *addresses, void *arg)
- {
- (void)ttl;
- ++n_wildcard_requests;
- if (result == DNS_ERR_NONE && count) {
- char *string_address = arg;
- int i;
- if (type == DNS_IPv4_A) {
- const uint32_t *addrs = addresses;
- for (i = 0; i < count; ++i) {
- char answer_buf[INET_NTOA_BUF_LEN+1];
- struct in_addr in;
- in.s_addr = addrs[i];
- tor_inet_ntoa(&in, answer_buf, sizeof(answer_buf));
- wildcard_increment_answer(answer_buf);
- }
- } else if (type == DNS_IPv6_AAAA) {
- const struct in6_addr *addrs = addresses;
- for (i = 0; i < count; ++i) {
- char answer_buf[TOR_ADDR_BUF_LEN+1];
- tor_inet_ntop(AF_INET6, &addrs[i], answer_buf, sizeof(answer_buf));
- wildcard_increment_answer(answer_buf);
- }
- }
- tor_log(dns_wildcard_one_notice_given ? LOG_INFO : LOG_NOTICE, LD_EXIT,
- "Your DNS provider gave an answer for \"%s\", which "
- "is not supposed to exist. Apparently they are hijacking "
- "DNS failures. Trying to correct for this. We've noticed %d "
- "possibly bad address%s so far.",
- string_address, strmap_size(dns_wildcard_response_count),
- (strmap_size(dns_wildcard_response_count) == 1) ? "" : "es");
- dns_wildcard_one_notice_given = 1;
- }
- tor_free(arg);
- }
- /** Launch a single request for a nonexistent hostname consisting of between
- * <b>min_len</b> and <b>max_len</b> random (plausible) characters followed by
- * <b>suffix</b> */
- static void
- launch_wildcard_check(int min_len, int max_len, int is_ipv6,
- const char *suffix)
- {
- char *addr;
- struct evdns_request *req;
- addr = crypto_random_hostname(min_len, max_len, "", suffix);
- log_info(LD_EXIT, "Testing whether our DNS server is hijacking nonexistent "
- "domains with request for bogus hostname \"%s\"", addr);
- tor_assert(the_evdns_base);
- if (is_ipv6)
- req = evdns_base_resolve_ipv6(
- the_evdns_base,
- /* This "addr" tells us which address to resolve */
- addr,
- DNS_QUERY_NO_SEARCH, evdns_wildcard_check_callback,
- /* This "addr" is an argument to the callback*/ addr);
- else
- req = evdns_base_resolve_ipv4(
- the_evdns_base,
- /* This "addr" tells us which address to resolve */
- addr,
- DNS_QUERY_NO_SEARCH, evdns_wildcard_check_callback,
- /* This "addr" is an argument to the callback*/ addr);
- if (!req) {
- /* There is no evdns request in progress; stop addr from getting leaked */
- tor_free(addr);
- }
- }
- /** Launch attempts to resolve a bunch of known-good addresses (configured in
- * ServerDNSTestAddresses). [Callback for a libevent timer] */
- static void
- launch_test_addresses(evutil_socket_t fd, short event, void *args)
- {
- const or_options_t *options = get_options();
- (void)fd;
- (void)event;
- (void)args;
- if (net_is_disabled())
- return;
- log_info(LD_EXIT, "Launching checks to see whether our nameservers like to "
- "hijack *everything*.");
- /* This situation is worse than the failure-hijacking situation. When this
- * happens, we're no good for DNS requests at all, and we shouldn't really
- * be an exit server.*/
- if (options->ServerDNSTestAddresses) {
- tor_assert(the_evdns_base);
- SMARTLIST_FOREACH_BEGIN(options->ServerDNSTestAddresses,
- const char *, address) {
- if (launch_one_resolve(address, DNS_IPv4_A, NULL) < 0) {
- log_info(LD_EXIT, "eventdns rejected test address %s",
- escaped_safe_str(address));
- }
- if (launch_one_resolve(address, DNS_IPv6_AAAA, NULL) < 0) {
- log_info(LD_EXIT, "eventdns rejected test address %s",
- escaped_safe_str(address));
- }
- } SMARTLIST_FOREACH_END(address);
- }
- }
- #define N_WILDCARD_CHECKS 2
- /** Launch DNS requests for a few nonexistent hostnames and a few well-known
- * hostnames, and see if we can catch our nameserver trying to hijack them and
- * map them to a stupid "I couldn't find ggoogle.com but maybe you'd like to
- * buy these lovely encyclopedias" page. */
- static void
- dns_launch_wildcard_checks(void)
- {
- int i, ipv6;
- log_info(LD_EXIT, "Launching checks to see whether our nameservers like "
- "to hijack DNS failures.");
- for (ipv6 = 0; ipv6 <= 1; ++ipv6) {
- for (i = 0; i < N_WILDCARD_CHECKS; ++i) {
- /* RFC2606 reserves these. Sadly, some DNS hijackers, in a silly
- * attempt to 'comply' with rfc2606, refrain from giving A records for
- * these. This is the standards-compliance equivalent of making sure
- * that your crackhouse's elevator inspection certificate is up to date.
- */
- launch_wildcard_check(2, 16, ipv6, ".invalid");
- launch_wildcard_check(2, 16, ipv6, ".test");
- /* These will break specs if there are ever any number of
- * 8+-character top-level domains. */
- launch_wildcard_check(8, 16, ipv6, "");
- /* Try some random .com/org/net domains. This will work fine so long as
- * not too many resolve to the same place. */
- launch_wildcard_check(8, 16, ipv6, ".com");
- launch_wildcard_check(8, 16, ipv6, ".org");
- launch_wildcard_check(8, 16, ipv6, ".net");
- }
- }
- }
- /** If appropriate, start testing whether our DNS servers tend to lie to
- * us. */
- void
- dns_launch_correctness_checks(void)
- {
- static struct event *launch_event = NULL;
- struct timeval timeout;
- if (!get_options()->ServerDNSDetectHijacking)
- return;
- dns_launch_wildcard_checks();
- /* Wait a while before launching requests for test addresses, so we can
- * get the results from checking for wildcarding. */
- if (! launch_event)
- launch_event = tor_evtimer_new(tor_libevent_get_base(),
- launch_test_addresses, NULL);
- timeout.tv_sec = 30;
- timeout.tv_usec = 0;
- if (evtimer_add(launch_event, &timeout)<0) {
- log_warn(LD_BUG, "Couldn't add timer for checking for dns hijacking");
- }
- }
- /** Return true iff our DNS servers lie to us too much to be trusted. */
- int
- dns_seems_to_be_broken(void)
- {
- return dns_is_completely_invalid;
- }
- /** Return true iff we think that IPv6 hostname lookup is broken */
- int
- dns_seems_to_be_broken_for_ipv6(void)
- {
- return dns_is_broken_for_ipv6;
- }
- /** Forget what we've previously learned about our DNS servers' correctness. */
- void
- dns_reset_correctness_checks(void)
- {
- strmap_free(dns_wildcard_response_count, tor_free_);
- dns_wildcard_response_count = NULL;
- n_wildcard_requests = 0;
- n_ipv6_requests_made = n_ipv6_timeouts = 0;
- if (dns_wildcard_list) {
- SMARTLIST_FOREACH(dns_wildcard_list, char *, cp, tor_free(cp));
- smartlist_clear(dns_wildcard_list);
- }
- if (dns_wildcarded_test_address_list) {
- SMARTLIST_FOREACH(dns_wildcarded_test_address_list, char *, cp,
- tor_free(cp));
- smartlist_clear(dns_wildcarded_test_address_list);
- }
- dns_wildcard_one_notice_given = dns_wildcard_notice_given =
- dns_wildcarded_test_address_notice_given = dns_is_completely_invalid =
- dns_is_broken_for_ipv6 = 0;
- }
- /** Return true iff we have noticed that the dotted-quad <b>ip</b> has been
- * returned in response to requests for nonexistent hostnames. */
- static int
- answer_is_wildcarded(const char *ip)
- {
- return dns_wildcard_list && smartlist_contains_string(dns_wildcard_list, ip);
- }
- /** Exit with an assertion if <b>resolve</b> is corrupt. */
- static void
- assert_resolve_ok(cached_resolve_t *resolve)
- {
- tor_assert(resolve);
- tor_assert(resolve->magic == CACHED_RESOLVE_MAGIC);
- tor_assert(strlen(resolve->address) < MAX_ADDRESSLEN);
- tor_assert(tor_strisnonupper(resolve->address));
- if (resolve->state != CACHE_STATE_PENDING) {
- tor_assert(!resolve->pending_connections);
- }
- if (resolve->state == CACHE_STATE_PENDING ||
- resolve->state == CACHE_STATE_DONE) {
- #if 0
- tor_assert(!resolve->ttl);
- if (resolve->is_reverse)
- tor_assert(!resolve->hostname);
- else
- tor_assert(!resolve->result_ipv4.addr_ipv4);
- #endif /* 0 */
- /*XXXXX ADD MORE */
- }
- }
- /** Return the number of DNS cache entries as an int */
- static int
- dns_cache_entry_count(void)
- {
- return HT_SIZE(&cache_root);
- }
- /** Log memory information about our internal DNS cache at level 'severity'. */
- void
- dump_dns_mem_usage(int severity)
- {
- /* This should never be larger than INT_MAX. */
- int hash_count = dns_cache_entry_count();
- size_t hash_mem = sizeof(struct cached_resolve_t) * hash_count;
- hash_mem += HT_MEM_USAGE(&cache_root);
- /* Print out the count and estimated size of our &cache_root. It undercounts
- hostnames in cached reverse resolves.
- */
- tor_log(severity, LD_MM, "Our DNS cache has %d entries.", hash_count);
- tor_log(severity, LD_MM, "Our DNS cache size is approximately %u bytes.",
- (unsigned)hash_mem);
- }
- #ifdef DEBUG_DNS_CACHE
- /** Exit with an assertion if the DNS cache is corrupt. */
- static void
- assert_cache_ok_(void)
- {
- cached_resolve_t **resolve;
- int bad_rep = HT_REP_IS_BAD_(cache_map, &cache_root);
- if (bad_rep) {
- log_err(LD_BUG, "Bad rep type %d on dns cache hash table", bad_rep);
- tor_assert(!bad_rep);
- }
- HT_FOREACH(resolve, cache_map, &cache_root) {
- assert_resolve_ok(*resolve);
- tor_assert((*resolve)->state != CACHE_STATE_DONE);
- }
- if (!cached_resolve_pqueue)
- return;
- smartlist_pqueue_assert_ok(cached_resolve_pqueue,
- compare_cached_resolves_by_expiry_,
- offsetof(cached_resolve_t, minheap_idx));
- SMARTLIST_FOREACH(cached_resolve_pqueue, cached_resolve_t *, res,
- {
- if (res->state == CACHE_STATE_DONE) {
- cached_resolve_t *found = HT_FIND(cache_map, &cache_root, res);
- tor_assert(!found || found != res);
- } else {
- cached_resolve_t *found = HT_FIND(cache_map, &cache_root, res);
- tor_assert(found);
- }
- });
- }
- #endif /* defined(DEBUG_DNS_CACHE) */
- cached_resolve_t *
- dns_get_cache_entry(cached_resolve_t *query)
- {
- return HT_FIND(cache_map, &cache_root, query);
- }
- void
- dns_insert_cache_entry(cached_resolve_t *new_entry)
- {
- HT_INSERT(cache_map, &cache_root, new_entry);
- }
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