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Diffstat (limited to 'src/feature/relay/dns.c')
| -rw-r--r-- | src/feature/relay/dns.c | 2143 |
1 files changed, 2143 insertions, 0 deletions
diff --git a/src/feature/relay/dns.c b/src/feature/relay/dns.c new file mode 100644 index 0000000000..4ac58552f4 --- /dev/null +++ b/src/feature/relay/dns.c @@ -0,0 +1,2143 @@ +/* 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 "or/or.h" +#include "or/circuitlist.h" +#include "or/circuituse.h" +#include "or/config.h" +#include "or/connection.h" +#include "or/connection_edge.h" +#include "or/control.h" +#include "lib/crypt_ops/crypto_rand.h" +#include "or/dns.h" +#include "or/main.h" +#include "or/policies.h" +#include "or/relay.h" +#include "or/router.h" +#include "ht.h" +#include "lib/sandbox/sandbox.h" +#include "lib/evloop/compat_libevent.h" + +#include "or/edge_connection_st.h" +#include "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); +} |