/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. * Copyright (c) 2007-2013, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** * \file rendmid.c * \brief Implement introductions points and rendezvous points. **/ #include "or.h" #include "circuitlist.h" #include "circuituse.h" #include "config.h" #include "relay.h" #include "rendmid.h" #include "rephist.h" /** Respond to an ESTABLISH_INTRO cell by checking the signed data and * setting the circuit's purpose and service pk digest. */ int rend_mid_establish_intro(or_circuit_t *circ, const uint8_t *request, size_t request_len) { crypto_pk_t *pk = NULL; char buf[DIGEST_LEN+9]; char expected_digest[DIGEST_LEN]; char pk_digest[DIGEST_LEN]; size_t asn1len; char serviceid[REND_SERVICE_ID_LEN_BASE32+1]; int reason = END_CIRC_REASON_INTERNAL; log_info(LD_REND, "Received an ESTABLISH_INTRO request on circuit %u", (unsigned) circ->p_circ_id); if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) { log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, "Rejecting ESTABLISH_INTRO on non-OR or non-edge circuit."); reason = END_CIRC_REASON_TORPROTOCOL; goto err; } if (request_len < 2+DIGEST_LEN) goto truncated; /* First 2 bytes: length of asn1-encoded key. */ asn1len = ntohs(get_uint16(request)); /* Next asn1len bytes: asn1-encoded key. */ if (request_len < 2+DIGEST_LEN+asn1len) goto truncated; pk = crypto_pk_asn1_decode((char*)(request+2), asn1len); if (!pk) { reason = END_CIRC_REASON_TORPROTOCOL; log_warn(LD_PROTOCOL, "Couldn't decode public key."); goto err; } /* Next 20 bytes: Hash of rend_circ_nonce | "INTRODUCE" */ memcpy(buf, circ->rend_circ_nonce, DIGEST_LEN); memcpy(buf+DIGEST_LEN, "INTRODUCE", 9); if (crypto_digest(expected_digest, buf, DIGEST_LEN+9) < 0) { log_warn(LD_BUG, "Internal error computing digest."); goto err; } if (tor_memneq(expected_digest, request+2+asn1len, DIGEST_LEN)) { log_warn(LD_PROTOCOL, "Hash of session info was not as expected."); reason = END_CIRC_REASON_TORPROTOCOL; goto err; } /* Rest of body: signature of previous data */ note_crypto_pk_op(REND_MID); if (crypto_pk_public_checksig_digest(pk, (char*)request, 2+asn1len+DIGEST_LEN, (char*)(request+2+DIGEST_LEN+asn1len), request_len-(2+DIGEST_LEN+asn1len))<0) { log_warn(LD_PROTOCOL, "Incorrect signature on ESTABLISH_INTRO cell; rejecting."); reason = END_CIRC_REASON_TORPROTOCOL; goto err; } /* The request is valid. First, compute the hash of Bob's PK.*/ if (crypto_pk_get_digest(pk, pk_digest)<0) { log_warn(LD_BUG, "Internal error: couldn't hash public key."); goto err; } crypto_pk_free(pk); /* don't need it anymore */ pk = NULL; /* so we don't free it again if err */ base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1, pk_digest, REND_SERVICE_ID_LEN); if (!get_options()->IntroPointAcceptMutipleConnections) { log_info(LD_REND, "Checking for existing circuits to remove %s as " "IntroPointAcceptMutipleConnections is not set", safe_str(serviceid)); smartlist_t *circuits = circuits_get_intro_point(pk_digest); /* Close any other intro circuits with the same pk. */ SMARTLIST_FOREACH_BEGIN(circuits, or_circuit_t *, circ) { log_info(LD_REND, "Replacing old circuit for service %s", safe_str(serviceid)); circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_FINISHED); } SMARTLIST_FOREACH_END(circ); } else { log_info(LD_REND, "Not removing existing circuits for %s as " "IntroPointAcceptMutipleConnections is set", safe_str(serviceid)); } /* Acknowledge the request. */ if (relay_send_command_from_edge(0, TO_CIRCUIT(circ), RELAY_COMMAND_INTRO_ESTABLISHED, "", 0, NULL)<0) { log_info(LD_GENERAL, "Couldn't send INTRO_ESTABLISHED cell."); goto err; } /* Now, set up this circuit. */ circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_INTRO_POINT); memcpy(circ->rend_token, pk_digest, DIGEST_LEN); log_info(LD_REND, "Established introduction point on circuit %u for service %s", (unsigned) circ->p_circ_id, safe_str(serviceid)); return 0; truncated: log_warn(LD_PROTOCOL, "Rejecting truncated ESTABLISH_INTRO cell."); reason = END_CIRC_REASON_TORPROTOCOL; err: if (pk) crypto_pk_free(pk); circuit_mark_for_close(TO_CIRCUIT(circ), reason); return -1; } /** Process an INTRODUCE1 cell by finding the corresponding introduction * circuit, and relaying the body of the INTRODUCE1 cell inside an * INTRODUCE2 cell. */ int rend_mid_introduce(or_circuit_t *circ, const uint8_t *request, size_t request_len) { or_circuit_t *intro_circ; char serviceid[REND_SERVICE_ID_LEN_BASE32+1]; char nak_body[1]; log_info(LD_REND, "Received an INTRODUCE1 request on circuit %u", (unsigned)circ->p_circ_id); if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) { log_warn(LD_PROTOCOL, "Rejecting INTRODUCE1 on non-OR or non-edge circuit %u.", (unsigned)circ->p_circ_id); goto err; } /* We could change this to MAX_HEX_NICKNAME_LEN now that 0.0.9.x is * obsolete; however, there isn't much reason to do so, and we're going * to revise this protocol anyway. */ if (request_len < (DIGEST_LEN+(MAX_NICKNAME_LEN+1)+REND_COOKIE_LEN+ DH_KEY_LEN+CIPHER_KEY_LEN+PKCS1_OAEP_PADDING_OVERHEAD)) { log_warn(LD_PROTOCOL, "Impossibly short INTRODUCE1 cell on circuit %u; " "responding with nack.", (unsigned)circ->p_circ_id); goto err; } base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1, (char*)request, REND_SERVICE_ID_LEN); /* The first 20 bytes are all we look at: they have a hash of Bob's PK. */ smartlist_t *intro_circuits = circuits_get_intro_point((char*)request); log_info(LD_REND, "found %i possible introduction circuits for service %s", smartlist_len(intro_circuits), safe_str(serviceid)); if (smartlist_len(intro_circuits) == 0) { log_info(LD_REND, "No intro circ found for INTRODUCE1 cell (%s) from circuit %u; " "responding with nack.", safe_str(serviceid), (unsigned)circ->p_circ_id); goto err; } // Need to select which circuit to use int circ_selection = -1; if (strcasecmp(get_options()->IntroPointLoadBalancingAlgorithm, "random")) { circ_selection = crypto_rand_int(smartlist_len(intro_circuits)); log_info(LD_REND, "selected circuit %i randomly for service %s", circ_selection, safe_str(serviceid)); } else if (strcasecmp(get_options()->IntroPointLoadBalancingAlgorithm, "roundrobin")) { SMARTLIST_FOREACH_BEGIN(intro_circuits, or_circuit_t *, circuit) { circ_selection++; if (circuit->intro_last_used) { circuit->intro_last_used = 0; break; } } SMARTLIST_FOREACH_END(circuit); circ_selection++; if (circ_selection == smartlist_len(intro_circuits)) circ_selection = 0; log_info(LD_REND, "selected circuit %i using round robin for service %s", circ_selection, safe_str(serviceid)); } else if (strcasecmp(get_options()->IntroPointLoadBalancingAlgorithm, "weightedroundrobin")) { } intro_circ = smartlist_get(intro_circuits, circ_selection); intro_circ->intro_last_used = 1; log_info(LD_REND, "Sending introduction request for service %s " "from circ %u to circ %u", safe_str(serviceid), (unsigned)circ->p_circ_id, (unsigned)intro_circ->p_circ_id); /* Great. Now we just relay the cell down the circuit. */ if (relay_send_command_from_edge(0, TO_CIRCUIT(intro_circ), RELAY_COMMAND_INTRODUCE2, (char*)request, request_len, NULL)) { log_warn(LD_GENERAL, "Unable to send INTRODUCE2 cell to Tor client."); goto err; } /* And sent an ack down Alice's circuit. Empty body means succeeded. */ if (relay_send_command_from_edge(0,TO_CIRCUIT(circ), RELAY_COMMAND_INTRODUCE_ACK, NULL,0,NULL)) { log_warn(LD_GENERAL, "Unable to send INTRODUCE_ACK cell to Tor client."); circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL); return -1; } return 0; err: /* Send the client an NACK */ nak_body[0] = 1; if (relay_send_command_from_edge(0,TO_CIRCUIT(circ), RELAY_COMMAND_INTRODUCE_ACK, nak_body, 1, NULL)) { log_warn(LD_GENERAL, "Unable to send NAK to Tor client."); /* Is this right? */ circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL); } return -1; } /** Process an ESTABLISH_RENDEZVOUS cell by setting the circuit's purpose and * rendezvous cookie. */ int rend_mid_establish_rendezvous(or_circuit_t *circ, const uint8_t *request, size_t request_len) { char hexid[9]; int reason = END_CIRC_REASON_TORPROTOCOL; log_info(LD_REND, "Received an ESTABLISH_RENDEZVOUS request on circuit %u", (unsigned)circ->p_circ_id); if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) { log_warn(LD_PROTOCOL, "Tried to establish rendezvous on non-OR or non-edge circuit."); goto err; } if (request_len != REND_COOKIE_LEN) { log_warn(LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS."); goto err; } if (circuit_get_rendezvous((char*)request)) { log_warn(LD_PROTOCOL, "Duplicate rendezvous cookie in ESTABLISH_RENDEZVOUS."); goto err; } /* Acknowledge the request. */ if (relay_send_command_from_edge(0,TO_CIRCUIT(circ), RELAY_COMMAND_RENDEZVOUS_ESTABLISHED, "", 0, NULL)<0) { log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell."); reason = END_CIRC_REASON_INTERNAL; goto err; } circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING); memcpy(circ->rend_token, request, REND_COOKIE_LEN); base16_encode(hexid,9,(char*)request,4); log_info(LD_REND, "Established rendezvous point on circuit %u for cookie %s", (unsigned)circ->p_circ_id, hexid); return 0; err: circuit_mark_for_close(TO_CIRCUIT(circ), reason); return -1; } /** Process a RENDEZVOUS1 cell by looking up the correct rendezvous * circuit by its relaying the cell's body in a RENDEZVOUS2 cell, and * connecting the two circuits. */ int rend_mid_rendezvous(or_circuit_t *circ, const uint8_t *request, size_t request_len) { or_circuit_t *rend_circ; char hexid[9]; int reason = END_CIRC_REASON_INTERNAL; if (circ->base_.purpose != CIRCUIT_PURPOSE_OR || circ->base_.n_chan) { log_info(LD_REND, "Tried to complete rendezvous on non-OR or non-edge circuit %u.", (unsigned)circ->p_circ_id); reason = END_CIRC_REASON_TORPROTOCOL; goto err; } if (request_len != REND_COOKIE_LEN+DH_KEY_LEN+DIGEST_LEN) { log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, "Rejecting RENDEZVOUS1 cell with bad length (%d) on circuit %u.", (int)request_len, (unsigned)circ->p_circ_id); reason = END_CIRC_REASON_TORPROTOCOL; goto err; } base16_encode(hexid, sizeof(hexid), (const char*)request, 4); log_info(LD_REND, "Got request for rendezvous from circuit %u to cookie %s.", (unsigned)circ->p_circ_id, hexid); rend_circ = circuit_get_rendezvous((char*)request); if (!rend_circ) { log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.", hexid); reason = END_CIRC_REASON_TORPROTOCOL; goto err; } /* Send the RENDEZVOUS2 cell to Alice. */ if (relay_send_command_from_edge(0, TO_CIRCUIT(rend_circ), RELAY_COMMAND_RENDEZVOUS2, (char*)(request+REND_COOKIE_LEN), request_len-REND_COOKIE_LEN, NULL)) { log_warn(LD_GENERAL, "Unable to send RENDEZVOUS2 cell to client on circuit %u.", (unsigned)rend_circ->p_circ_id); goto err; } /* Join the circuits. */ log_info(LD_REND, "Completing rendezvous: circuit %u joins circuit %u (cookie %s)", (unsigned)circ->p_circ_id, (unsigned)rend_circ->p_circ_id, hexid); circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_ESTABLISHED); circuit_change_purpose(TO_CIRCUIT(rend_circ), CIRCUIT_PURPOSE_REND_ESTABLISHED); memset(circ->rend_token, 0, REND_COOKIE_LEN); rend_circ->rend_splice = circ; circ->rend_splice = rend_circ; return 0; err: circuit_mark_for_close(TO_CIRCUIT(circ), reason); return -1; }