diff options
| -rw-r--r-- | changes/bug17604 | 14 | ||||
| -rw-r--r-- | src/or/channel.c | 137 | ||||
| -rw-r--r-- | src/or/channel.h | 8 | ||||
| -rw-r--r-- | src/or/channeltls.c | 42 | ||||
| -rw-r--r-- | src/or/connection_or.c | 14 | ||||
| -rw-r--r-- | src/or/main.c | 19 |
6 files changed, 190 insertions, 44 deletions
diff --git a/changes/bug17604 b/changes/bug17604 new file mode 100644 index 0000000000..20ac2c38e9 --- /dev/null +++ b/changes/bug17604 @@ -0,0 +1,14 @@ + o Minor bugfixes (connection usage) + - Use NETINFO cells to try to determine if both relays involved in + a connection will agree on the canonical status of that connection. + Prefer the connections where this is the case for extend cells, + and try to close connections where relays disagree on canonical + status early. Also, additionally alter the connection selection + logic to prefer the oldest valid connection for extend cells. + These two changes should reduce the number of long-term connections + that are kept open between relays. Fixes bug #17604. + - Relays will now log hourly statistics on the total number of + connections to other relays. If the number of connections per relay + unexpectedly large, this log message is at notice level. Otherwise + it is at info. + diff --git a/src/or/channel.c b/src/or/channel.c index 74793436da..a806c4c93b 100644 --- a/src/or/channel.c +++ b/src/or/channel.c @@ -837,6 +837,83 @@ channel_next_with_rsa_identity(channel_t *chan) } /** + * Relays run this once an hour to look over our list of channels to other + * relays. It prints out some statistics if there are multiple connections + * to many relays. + * + * This function is similar to connection_or_set_bad_connections(), + * and probably could be adapted to replace it, if it was modified to actually + * take action on any of these connections. + */ +void +channel_check_for_duplicates(void) +{ + channel_idmap_entry_t **iter; + channel_t *chan; + int total_relay_connections = 0, total_relays = 0, total_canonical = 0; + int total_half_canonical = 0; + int total_gt_one_connection = 0, total_gt_two_connections = 0; + int total_gt_four_connections = 0; + + HT_FOREACH(iter, channel_idmap, &channel_identity_map) { + int connections_to_relay = 0; + + /* Only consider relay connections */ + if (!connection_or_digest_is_known_relay((char*)(*iter)->digest)) + continue; + + total_relays++; + + for (chan = TOR_LIST_FIRST(&(*iter)->channel_list); chan; + chan = channel_next_with_rsa_identity(chan)) { + + if (CHANNEL_CONDEMNED(chan) || !CHANNEL_IS_OPEN(chan)) + continue; + + connections_to_relay++; + total_relay_connections++; + + if (chan->is_canonical(chan, 0)) total_canonical++; + + if (!chan->is_canonical_to_peer && chan->is_canonical(chan, 0) + && chan->is_canonical(chan, 1)) { + total_half_canonical++; + } + } + + if (connections_to_relay > 1) total_gt_one_connection++; + if (connections_to_relay > 2) total_gt_two_connections++; + if (connections_to_relay > 4) total_gt_four_connections++; + } + +#define MIN_RELAY_CONNECTIONS_TO_WARN 5 + + /* If we average 1.5 or more connections per relay, something is wrong */ + if (total_relays > MIN_RELAY_CONNECTIONS_TO_WARN && + total_relay_connections >= 1.5*total_relays) { + log_notice(LD_OR, + "Your relay has a very large number of connections to other relays. " + "Is your outbound address the same as your relay address? " + "Found %d connections to %d relays. Found %d current canonical " + "connections, in %d of which we were a non-canonical peer. " + "%d relays had more than 1 connection, %d had more than 2, and " + "%d had more than 4 connections.", + total_relay_connections, total_relays, total_canonical, + total_half_canonical, total_gt_one_connection, + total_gt_two_connections, total_gt_four_connections); + } else { + log_info(LD_OR, "Performed connection pruning. " + "Found %d connections to %d relays. Found %d current canonical " + "connections, in %d of which we were a non-canonical peer. " + "%d relays had more than 1 connection, %d had more than 2, and " + "%d had more than 4 connections.", + total_relay_connections, total_relays, total_canonical, + total_half_canonical, total_gt_one_connection, + total_gt_two_connections, total_gt_four_connections); + } +} + +/** * Initialize a channel * * This function should be called by subclasses to set up some per-channel @@ -3323,22 +3400,20 @@ channel_connect(const tor_addr_t *addr, uint16_t port, */ int -channel_is_better(time_t now, channel_t *a, channel_t *b, - int forgive_new_connections) +channel_is_better(channel_t *a, channel_t *b) { - int a_grace, b_grace; int a_is_canonical, b_is_canonical; - int a_has_circs, b_has_circs; - - /* - * Do not definitively deprecate a new channel with no circuits on it - * until this much time has passed. - */ -#define NEW_CHAN_GRACE_PERIOD (15*60) tor_assert(a); tor_assert(b); + /* If one channel is bad for new circuits, and the other isn't, + * use the one that is still good. */ + if (!channel_is_bad_for_new_circs(a) && channel_is_bad_for_new_circs(b)) + return 1; + if (channel_is_bad_for_new_circs(a) && !channel_is_bad_for_new_circs(b)) + return 0; + /* Check if one is canonical and the other isn't first */ a_is_canonical = channel_is_canonical(a); b_is_canonical = channel_is_canonical(b); @@ -3346,26 +3421,31 @@ channel_is_better(time_t now, channel_t *a, channel_t *b, if (a_is_canonical && !b_is_canonical) return 1; if (!a_is_canonical && b_is_canonical) return 0; + /* Check if we suspect that one of the channels will be preferred + * by the peer */ + if (a->is_canonical_to_peer && !b->is_canonical_to_peer) return 1; + if (!a->is_canonical_to_peer && b->is_canonical_to_peer) return 0; + /* - * Okay, if we're here they tied on canonicity. Next we check if - * they have any circuits, and if one does and the other doesn't, - * we prefer the one that does, unless we are forgiving and the - * one that has no circuits is in its grace period. + * Okay, if we're here they tied on canonicity, the prefer the older + * connection, so that the adversary can't create a new connection + * and try to switch us over to it (which will leak information + * about long-lived circuits). Additionally, switching connections + * too often makes us more vulnerable to attacks like Torscan and + * passive netflow-based equivalents. + * + * Connections will still only live for at most a week, due to + * the check in connection_or_group_set_badness() against + * TIME_BEFORE_OR_CONN_IS_TOO_OLD, which marks old connections as + * unusable for new circuits after 1 week. That check sets + * is_bad_for_new_circs, which is checked in channel_get_for_extend(). + * + * We check channel_is_bad_for_new_circs() above here anyway, for safety. */ + if (channel_when_created(a) < channel_when_created(b)) return 1; + else if (channel_when_created(a) > channel_when_created(b)) return 0; - a_has_circs = (channel_num_circuits(a) > 0); - b_has_circs = (channel_num_circuits(b) > 0); - a_grace = (forgive_new_connections && - (now < channel_when_created(a) + NEW_CHAN_GRACE_PERIOD)); - b_grace = (forgive_new_connections && - (now < channel_when_created(b) + NEW_CHAN_GRACE_PERIOD)); - - if (a_has_circs && !b_has_circs && !b_grace) return 1; - if (!a_has_circs && b_has_circs && !a_grace) return 0; - - /* They tied on circuits too; just prefer whichever is newer */ - - if (channel_when_created(a) > channel_when_created(b)) return 1; + if (channel_num_circuits(a) > channel_num_circuits(b)) return 1; else return 0; } @@ -3390,7 +3470,6 @@ channel_get_for_extend(const char *rsa_id_digest, channel_t *chan, *best = NULL; int n_inprogress_goodaddr = 0, n_old = 0; int n_noncanonical = 0, n_possible = 0; - time_t now = approx_time(); tor_assert(msg_out); tor_assert(launch_out); @@ -3460,7 +3539,7 @@ channel_get_for_extend(const char *rsa_id_digest, continue; } - if (channel_is_better(now, chan, best, 0)) + if (channel_is_better(chan, best)) best = chan; } diff --git a/src/or/channel.h b/src/or/channel.h index 21211dc8bd..f03fabb7c2 100644 --- a/src/or/channel.h +++ b/src/or/channel.h @@ -85,6 +85,9 @@ struct channel_s { /** Is there a pending netflow padding callback? */ unsigned int pending_padding_callback:1; + /** Is our peer likely to consider this channel canonical? */ + unsigned int is_canonical_to_peer:1; + /** Has this channel ever been used for non-directory traffic? * Used to decide what channels to pad, and when. */ channel_usage_info_t channel_usage; @@ -599,9 +602,7 @@ channel_t * channel_get_for_extend(const char *rsa_id_digest, int *launch_out); /* Ask which of two channels is better for circuit-extension purposes */ -int channel_is_better(time_t now, - channel_t *a, channel_t *b, - int forgive_new_connections); +int channel_is_better(channel_t *a, channel_t *b); /** Channel lookups */ @@ -684,6 +685,7 @@ void channel_listener_dump_statistics(channel_listener_t *chan_l, int severity); void channel_listener_dump_transport_statistics(channel_listener_t *chan_l, int severity); +void channel_check_for_duplicates(void); void channel_update_bad_for_new_circs(const char *digest, int force); diff --git a/src/or/channeltls.c b/src/or/channeltls.c index 155684c0ce..4f2663adab 100644 --- a/src/or/channeltls.c +++ b/src/or/channeltls.c @@ -739,6 +739,15 @@ channel_tls_matches_target_method(channel_t *chan, return 0; } + /* real_addr is the address this connection came from. + * base_.addr is updated by connection_or_init_conn_from_address() + * to be the address in the descriptor. It may be tempting to + * allow either address to be allowed, but if we did so, it would + * enable someone who steals a relay's keys to impersonate/MITM it + * from anywhere on the Internet! (Because they could make long-lived + * TLS connections from anywhere to all relays, and wait for them to + * be used for extends). + */ return tor_addr_eq(&(tlschan->conn->real_addr), target); } @@ -1667,6 +1676,7 @@ channel_tls_process_netinfo_cell(cell_t *cell, channel_tls_t *chan) const uint8_t *cp, *end; uint8_t n_other_addrs; time_t now = time(NULL); + const routerinfo_t *me = router_get_my_routerinfo(); long apparent_skew = 0; tor_addr_t my_apparent_addr = TOR_ADDR_NULL; @@ -1745,8 +1755,20 @@ channel_tls_process_netinfo_cell(cell_t *cell, channel_tls_t *chan) if (my_addr_type == RESOLVED_TYPE_IPV4 && my_addr_len == 4) { tor_addr_from_ipv4n(&my_apparent_addr, get_uint32(my_addr_ptr)); + + if (!get_options()->BridgeRelay && me && + get_uint32(my_addr_ptr) == htonl(me->addr)) { + chan->base_.is_canonical_to_peer = 1; + } + } else if (my_addr_type == RESOLVED_TYPE_IPV6 && my_addr_len == 16) { tor_addr_from_ipv6_bytes(&my_apparent_addr, (const char *) my_addr_ptr); + + if (!get_options()->BridgeRelay && me && + !tor_addr_is_null(&me->ipv6_addr) && + tor_addr_eq(&my_apparent_addr, &me->ipv6_addr)) { + chan->base_.is_canonical_to_peer = 1; + } } n_other_addrs = (uint8_t) *cp++; @@ -1762,6 +1784,14 @@ channel_tls_process_netinfo_cell(cell_t *cell, channel_tls_t *chan) connection_or_close_for_error(chan->conn, 0); return; } + /* A relay can connect from anywhere and be canonical, so + * long as it tells you from where it came. This may be a bit + * concerning.. Luckily we have another check in + * channel_tls_matches_target_method() to ensure that extends + * only go to the IP they ask for. + * + * XXX: Bleh. That check is not used if the connection is canonical. + */ if (tor_addr_eq(&addr, &(chan->conn->real_addr))) { connection_or_set_canonical(chan->conn, 1); break; @@ -1770,6 +1800,18 @@ channel_tls_process_netinfo_cell(cell_t *cell, channel_tls_t *chan) --n_other_addrs; } + if (me && !chan->base_.is_canonical_to_peer && chan->conn->is_canonical) { + log_info(LD_OR, + "We made a connection to a relay at %s (fp=%s) but we think " + "they will not consider this connection canonical. They " + "think we are at %s, but we think its %s.", + safe_str(chan->base_.get_remote_descr(&chan->base_, 0)), + safe_str(hex_str(chan->conn->identity_digest, DIGEST_LEN)), + safe_str(tor_addr_is_null(&my_apparent_addr) ? + "<none>" : fmt_and_decorate_addr(&my_apparent_addr)), + safe_str(fmt_addr32(me->addr))); + } + /* Act on apparent skew. */ /** Warn when we get a netinfo skew with at least this value. */ #define NETINFO_NOTICE_SKEW 3600 diff --git a/src/or/connection_or.c b/src/or/connection_or.c index 5d32217c86..c77e364717 100644 --- a/src/or/connection_or.c +++ b/src/or/connection_or.c @@ -1040,10 +1040,8 @@ connection_or_group_set_badness_(smartlist_t *group, int force) } if (!best || - channel_is_better(now, - TLS_CHAN_TO_BASE(or_conn->chan), - TLS_CHAN_TO_BASE(best->chan), - 0)) { + channel_is_better(TLS_CHAN_TO_BASE(or_conn->chan), + TLS_CHAN_TO_BASE(best->chan))) { best = or_conn; } } SMARTLIST_FOREACH_END(or_conn); @@ -1071,11 +1069,9 @@ connection_or_group_set_badness_(smartlist_t *group, int force) or_conn->base_.state != OR_CONN_STATE_OPEN) continue; if (or_conn != best && - channel_is_better(now, - TLS_CHAN_TO_BASE(best->chan), - TLS_CHAN_TO_BASE(or_conn->chan), 1)) { - /* This isn't the best conn, _and_ the best conn is better than it, - even when we're being forgiving. */ + channel_is_better(TLS_CHAN_TO_BASE(best->chan), + TLS_CHAN_TO_BASE(or_conn->chan))) { + /* This isn't the best conn, _and_ the best conn is better than it */ if (best->is_canonical) { log_info(LD_OR, "Marking OR conn to %s:%d as unsuitable for new circuits: " diff --git a/src/or/main.c b/src/or/main.c index e124441041..5bc132a0e3 100644 --- a/src/or/main.c +++ b/src/or/main.c @@ -1189,6 +1189,7 @@ CALLBACK(write_bridge_ns); CALLBACK(check_fw_helper_app); CALLBACK(heartbeat); CALLBACK(reset_padding_counts); +CALLBACK(check_canonical_channels); #undef CALLBACK @@ -1221,6 +1222,7 @@ static periodic_event_item_t periodic_events[] = { CALLBACK(check_fw_helper_app), CALLBACK(heartbeat), CALLBACK(reset_padding_counts), + CALLBACK(check_canonical_channels), END_OF_PERIODIC_EVENTS }; #undef CALLBACK @@ -1726,9 +1728,17 @@ write_stats_file_callback(time_t now, const or_options_t *options) return safe_timer_diff(now, next_time_to_write_stats_files); } -/** - * Periodic callback: Write bridge statistics to disk if appropriate. - */ +#define CHANNEL_CHECK_INTERVAL (60*60) +static int +check_canonical_channels_callback(time_t now, const or_options_t *options) +{ + (void)now; + if (public_server_mode(options)) + channel_check_for_duplicates(); + + return CHANNEL_CHECK_INTERVAL; +} + static int reset_padding_counts_callback(time_t now, const or_options_t *options) { @@ -1740,6 +1750,9 @@ reset_padding_counts_callback(time_t now, const or_options_t *options) return REPHIST_CELL_PADDING_COUNTS_INTERVAL; } +/** + * Periodic callback: Write bridge statistics to disk if appropriate. + */ static int record_bridge_stats_callback(time_t now, const or_options_t *options) { |