mirror of
https://gitlab.torproject.org/tpo/core/tor.git
synced 2024-09-21 13:34:59 +02:00
Bug 7691: Send a probe cell down certain types of circs.
In general, if we tried to use a circ for a stream, but then decided to place that stream on a different circuit, we need to probe the original circuit before deciding it was a "success". We also need to do the same for cannibalized circuits that go unused.
This commit is contained in:
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3458d904f6
commit
15fdfc2993
@ -39,6 +39,7 @@
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#include "routerparse.h"
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#include "routerset.h"
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#include "crypto.h"
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#include "connection_edge.h"
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#ifndef MIN
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#define MIN(a,b) ((a)<(b)?(a):(b))
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@ -1503,6 +1504,149 @@ pathbias_count_build_success(origin_circuit_t *circ)
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}
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}
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/**
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* Send a probe down a circuit that wasn't usable.
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*
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* Returns -1 if we couldn't probe, 0 otherwise.
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*/
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static int
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pathbias_send_usable_probe(circuit_t *circ)
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{
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/* Based on connection_ap_handshake_send_begin() */
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char payload[CELL_PAYLOAD_SIZE];
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int payload_len;
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origin_circuit_t *ocirc = TO_ORIGIN_CIRCUIT(circ);
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crypt_path_t *cpath_layer = NULL;
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// XXX: Generate a random 0.a.b.c adddress
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const char *probe_nonce = "0.1.2.3";
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tor_assert(ocirc);
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cpath_layer = ocirc->cpath->prev;
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if (cpath_layer->state != CPATH_STATE_OPEN) {
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/* This can happen for cannibalized circuits. Their
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* last hop isn't yet open */
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log_info(LD_CIRC,
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"Got pathbias probe request for unopened circuit %d. "
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"Opened %d, len %d", ocirc->global_identifier,
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ocirc->has_opened, ocirc->build_state->desired_path_len);
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return -1;
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}
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/* We already went down this road. */
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if (circ->purpose == CIRCUIT_PURPOSE_PATH_BIAS_TESTING &&
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ocirc->pathbias_probe_id) {
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log_info(LD_CIRC,
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"Got pathbias probe request for circuit %d with "
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"outstanding probe", ocirc->global_identifier);
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return -1;
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}
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circuit_change_purpose(circ, CIRCUIT_PURPOSE_PATH_BIAS_TESTING);
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/* Update timestamp for circuit_expire_building to kill us */
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tor_gettimeofday(&circ->timestamp_began);
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tor_snprintf(payload,RELAY_PAYLOAD_SIZE, "%s:25", probe_nonce);
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tor_addr_parse(ô->pathbias_probe_nonce, probe_nonce);
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payload_len = (int)strlen(payload)+1;
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// XXX: need this? Can we assume ipv4 will always be supported?
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// If not, how do we tell?
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//if (payload_len <= RELAY_PAYLOAD_SIZE - 4 && edge_conn->begincell_flags) {
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// set_uint32(payload + payload_len, htonl(edge_conn->begincell_flags));
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// payload_len += 4;
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//}
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/* Generate+Store stream id, make sure it's non-zero */
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ocirc->pathbias_probe_id = get_unique_stream_id_by_circ(ocirc);
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if (ocirc->pathbias_probe_id==0) {
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log_warn(LD_CIRC,
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"Ran out of stream IDs on circuit %u during "
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"pathbias probe attempt.", ocirc->global_identifier);
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return -1;
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}
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log_info(LD_CIRC,
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"Sending pathbias testing cell to %s:25 on stream %d for circ %d.",
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probe_nonce, ocirc->pathbias_probe_id, ocirc->global_identifier);
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/* Send a test relay cell */
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if (relay_send_command_from_edge(ocirc->pathbias_probe_id, circ,
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RELAY_COMMAND_BEGIN, payload,
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payload_len, cpath_layer) < 0) {
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log_notice(LD_CIRC,
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"Failed to send pathbias probe cell on circuit %d.",
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ocirc->global_identifier);
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return -1;
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}
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/* Mark it freshly dirty so it doesn't get expired in the meantime */
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circ->timestamp_dirty = time(NULL);
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return 0;
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}
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/**
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* Check the response to a pathbias probe.
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*
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* If the response is valid, return 0. Otherwise return < 0.
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*/
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int
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pathbias_check_probe_response(circuit_t *circ, cell_t *cell)
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{
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/* Based on connection_edge_process_relay_cell() */
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relay_header_t rh;
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int reason;
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uint32_t ipv4_host;
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tor_addr_t host;
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origin_circuit_t *ocirc = TO_ORIGIN_CIRCUIT(circ);
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tor_assert(cell);
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tor_assert(ocirc);
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tor_assert(circ->purpose == CIRCUIT_PURPOSE_PATH_BIAS_TESTING);
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relay_header_unpack(&rh, cell->payload);
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reason = rh.length > 0 ?
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get_uint8(cell->payload+RELAY_HEADER_SIZE) : END_STREAM_REASON_MISC;
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if (rh.command == RELAY_COMMAND_END &&
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reason == END_STREAM_REASON_EXITPOLICY &&
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ocirc->pathbias_probe_id == rh.stream_id) {
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/* Check length+extract host: It is in network order after the reason code.
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* See connection_edge_end(). */
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if (rh.length != 9) { /* reason+ipv4+dns_ttl */
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log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
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"Path bias probe response length field is insane (%d).",
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rh.length);
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return - END_CIRC_REASON_TORPROTOCOL;
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}
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ipv4_host = get_uint32(cell->payload+RELAY_HEADER_SIZE+1);
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tor_addr_from_ipv4n(&host, ipv4_host);
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/* Check nonce */
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if (memcmp(&host, ô->pathbias_probe_nonce, sizeof(tor_addr_t)) == 0) {
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ocirc->path_state = PATH_STATE_USE_SUCCEEDED;
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circuit_mark_for_close(circ, END_CIRC_REASON_FINISHED);
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log_info(LD_CIRC,
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"Got valid path bias probe back for circ %d, stream %d.",
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ocirc->global_identifier, ocirc->pathbias_probe_id);
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return 0;
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}
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}
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log_info(LD_CIRC,
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"Got another cell back back on pathbias probe circuit %d: "
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"Command: %d, Reason: %d, Stream-id: %d",
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ocirc->global_identifier, rh.command, reason, rh.stream_id);
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return -1;
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}
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/**
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* Check if a circuit was used and/or closed successfully.
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*
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@ -1512,18 +1656,26 @@ pathbias_count_build_success(origin_circuit_t *circ)
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*
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* If we *have* successfully used the circuit, or it appears to
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* have been closed by us locally, count it as a success.
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*
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* Returns 0 if we're done making decisions with the circ,
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* or -1 if we want to probe it first.
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*/
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void
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int
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pathbias_check_close(origin_circuit_t *ocirc, int reason)
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{
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circuit_t *circ = ô->base_;
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if (!pathbias_should_count(ocirc)) {
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return;
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return 0;
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}
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if (ocirc->path_state == PATH_STATE_BUILD_SUCCEEDED) {
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if (circ->timestamp_dirty) {
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if (pathbias_send_usable_probe(circ) == 0)
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return -1;
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else
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pathbias_count_unusable(ocirc);
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/* Any circuit where there were attempted streams but no successful
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* streams could be bias */
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log_info(LD_CIRC,
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@ -1533,7 +1685,7 @@ pathbias_check_close(origin_circuit_t *ocirc, int reason)
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reason, circ->purpose, ocirc->has_opened,
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circuit_state_to_string(circ->state),
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ocirc->build_state->desired_path_len);
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pathbias_count_unusable(ocirc);
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} else {
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if (reason & END_CIRC_REASON_FLAG_REMOTE) {
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/* Unused remote circ close reasons all could be bias */
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@ -1569,6 +1721,8 @@ pathbias_check_close(origin_circuit_t *ocirc, int reason)
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} else if (ocirc->path_state == PATH_STATE_USE_SUCCEEDED) {
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pathbias_count_successful_close(ocirc);
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}
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return 0;
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}
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/**
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@ -60,7 +60,8 @@ const node_t *choose_good_entry_server(uint8_t purpose,
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double pathbias_get_extreme_rate(const or_options_t *options);
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int pathbias_get_dropguards(const or_options_t *options);
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void pathbias_count_timeout(origin_circuit_t *circ);
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void pathbias_check_close(origin_circuit_t *circ, int reason);
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int pathbias_check_close(origin_circuit_t *circ, int reason);
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int pathbias_check_probe_response(circuit_t *circ, cell_t *cell);
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#endif
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@ -414,6 +414,8 @@ circuit_purpose_to_controller_string(uint8_t purpose)
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return "MEASURE_TIMEOUT";
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case CIRCUIT_PURPOSE_CONTROLLER:
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return "CONTROLLER";
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case CIRCUIT_PURPOSE_PATH_BIAS_TESTING:
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return "PATH_BIAS_TESTING";
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default:
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tor_snprintf(buf, sizeof(buf), "UNKNOWN_%d", (int)purpose);
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@ -441,6 +443,7 @@ circuit_purpose_to_controller_hs_state_string(uint8_t purpose)
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case CIRCUIT_PURPOSE_C_MEASURE_TIMEOUT:
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case CIRCUIT_PURPOSE_TESTING:
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case CIRCUIT_PURPOSE_CONTROLLER:
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case CIRCUIT_PURPOSE_PATH_BIAS_TESTING:
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return NULL;
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case CIRCUIT_PURPOSE_INTRO_POINT:
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@ -1356,7 +1359,10 @@ circuit_mark_for_close_(circuit_t *circ, int reason, int line,
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}
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if (CIRCUIT_IS_ORIGIN(circ)) {
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pathbias_check_close(TO_ORIGIN_CIRCUIT(circ), reason);
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if (pathbias_check_close(TO_ORIGIN_CIRCUIT(circ), reason) == -1) {
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/* Don't close it yet, we need to test it first */
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return;
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}
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/* We don't send reasons when closing circuits at the origin. */
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reason = END_CIRC_REASON_NONE;
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@ -493,6 +493,8 @@ circuit_expire_building(void)
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cutoff = s_intro_cutoff;
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else if (victim->purpose == CIRCUIT_PURPOSE_C_ESTABLISH_REND)
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cutoff = stream_cutoff;
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else if (victim->purpose == CIRCUIT_PURPOSE_PATH_BIAS_TESTING)
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cutoff = close_cutoff;
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else if (TO_ORIGIN_CIRCUIT(victim)->has_opened &&
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victim->state != CIRCUIT_STATE_OPEN)
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cutoff = cannibalized_cutoff;
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@ -581,6 +583,11 @@ circuit_expire_building(void)
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victim->timestamp_dirty > cutoff.tv_sec)
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continue;
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break;
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case CIRCUIT_PURPOSE_PATH_BIAS_TESTING:
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/* Open path bias testing circuits are given a long
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* time to complete the test, but not forever */
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TO_ORIGIN_CIRCUIT(victim)->path_state = PATH_STATE_USE_FAILED;
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break;
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case CIRCUIT_PURPOSE_C_INTRODUCING:
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/* We keep old introducing circuits around for
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* a while in parallel, and they can end up "opened".
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@ -652,6 +659,18 @@ circuit_expire_building(void)
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circuit_build_times_set_timeout(&circ_times);
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}
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}
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if (TO_ORIGIN_CIRCUIT(victim)->has_opened &&
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victim->purpose != CIRCUIT_PURPOSE_PATH_BIAS_TESTING) {
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/* For path bias: we want to let these guys live for a while
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* so we get a chance to test them. */
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log_info(LD_CIRC,
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"Allowing cannibalized circuit %d time to finish building as a "
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"pathbias testing circ.",
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TO_ORIGIN_CIRCUIT(victim)->global_identifier);
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circuit_change_purpose(victim, CIRCUIT_PURPOSE_PATH_BIAS_TESTING);
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continue; /* It now should have a longer timeout next time */
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}
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}
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/* If this is a hidden service client circuit which is far enough
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@ -1232,18 +1251,6 @@ circuit_has_opened(origin_circuit_t *circ)
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{
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control_event_circuit_status(circ, CIRC_EVENT_BUILT, 0);
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/* Cannibalized circuits count as used for path bias.
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* (PURPOSE_GENERAL circs especially, since they are
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* marked dirty and often go unused after preemptive
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* building). */
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// XXX: Cannibalized now use RELAY_EARLY, which is visible
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// to taggers end-to-end! We really need to probe these instead.
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// Don't forget to remove this check once that's done!
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if (circ->has_opened &&
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circ->build_state->desired_path_len > DEFAULT_ROUTE_LEN) {
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circ->path_state = PATH_STATE_USE_SUCCEEDED;
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}
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/* Remember that this circuit has finished building. Now if we start
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* it building again later (e.g. by extending it), we will know not
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* to consider its build time. */
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@ -1661,7 +1661,7 @@ connection_ap_process_natd(entry_connection_t *conn)
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/** Iterate over the two bytes of stream_id until we get one that is not
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* already in use; return it. Return 0 if can't get a unique stream_id.
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*/
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static streamid_t
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streamid_t
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get_unique_stream_id_by_circ(origin_circuit_t *circ)
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{
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edge_connection_t *tmpconn;
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@ -90,6 +90,7 @@ int connection_edge_update_circuit_isolation(const entry_connection_t *conn,
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origin_circuit_t *circ,
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int dry_run);
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void circuit_clear_isolation(origin_circuit_t *circ);
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streamid_t get_unique_stream_id_by_circ(origin_circuit_t *circ);
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/** @name Begin-cell flags
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*
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12
src/or/or.h
12
src/or/or.h
@ -522,7 +522,9 @@ typedef enum {
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#define CIRCUIT_PURPOSE_TESTING 18
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/** A controller made this circuit and Tor should not use it. */
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#define CIRCUIT_PURPOSE_CONTROLLER 19
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#define CIRCUIT_PURPOSE_MAX_ 19
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/** This circuit is used for path bias probing only */
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#define CIRCUIT_PURPOSE_PATH_BIAS_TESTING 20
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#define CIRCUIT_PURPOSE_MAX_ 20
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/** A catch-all for unrecognized purposes. Currently we don't expect
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* to make or see any circuits with this purpose. */
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#define CIRCUIT_PURPOSE_UNKNOWN 255
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@ -2887,6 +2889,14 @@ typedef struct origin_circuit_t {
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* debug why we are not seeing first hops in some cases. */
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path_state_t path_state : 3;
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/** For path probing. Store the temporary probe stream ID
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* for response comparison */
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streamid_t pathbias_probe_id;
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/** For path probing. Store the temporary probe address nonce
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* for response comparison. */
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tor_addr_t pathbias_probe_nonce;
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/** Set iff this is a hidden-service circuit which has timed out
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* according to our current circuit-build timeout, but which has
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* been kept around because it might still succeed in connecting to
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@ -186,7 +186,17 @@ circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
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}
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if (recognized) {
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edge_connection_t *conn = relay_lookup_conn(circ, cell, cell_direction,
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edge_connection_t *conn = NULL;
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if (circ->purpose == CIRCUIT_PURPOSE_PATH_BIAS_TESTING) {
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pathbias_check_probe_response(circ, cell);
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/* We need to drop this cell no matter what to avoid code that expects
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* a certain purpose (such as the hidserv code). */
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return 0;
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}
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conn = relay_lookup_conn(circ, cell, cell_direction,
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layer_hint);
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if (cell_direction == CELL_DIRECTION_OUT) {
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++stats_n_relay_cells_delivered;
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@ -222,8 +232,16 @@ circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
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} else {
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log_fn(LOG_PROTOCOL_WARN, LD_OR,
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"Dropping unrecognized inbound cell on origin circuit.");
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/* If we see unrecognized cells on path bias testing circs,
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* it's bad mojo. Those circuits need to die.
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* XXX: Shouldn't they always die? */
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if (circ->purpose == CIRCUIT_PURPOSE_PATH_BIAS_TESTING) {
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TO_ORIGIN_CIRCUIT(circ)->path_state = PATH_STATE_USE_FAILED;
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return -END_CIRC_REASON_TORPROTOCOL;
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} else {
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return 0;
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}
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}
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if (!chan) {
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// XXXX Can this splice stuff be done more cleanly?
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