/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. * Copyright (c) 2007-2016, 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; or_circuit_t *c; 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 the service'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); /* Close any other intro circuits with the same pk. */ c = NULL; while ((c = hs_circuitmap_get_intro_circ_v2((const uint8_t *)pk_digest))) { log_info(LD_REND, "Replacing old circuit for service %s", safe_str(serviceid)); circuit_mark_for_close(TO_CIRCUIT(c), END_CIRC_REASON_FINISHED); /* Now it's marked, and it won't be returned next time. */ } /* 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_no_close; } /* Now, set up this circuit. */ circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_INTRO_POINT); hs_circuitmap_register_intro_circ_v2(circ, (uint8_t *)pk_digest); 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: circuit_mark_for_close(TO_CIRCUIT(circ), reason); err_no_close: if (pk) crypto_pk_free(pk); 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 have already done an introduction on this circuit but we just received a request for another one. We block it since this might be an attempt to DoS a hidden service (#15515). */ if (circ->already_received_introduce1) { log_fn(LOG_PROTOCOL_WARN, LD_REND, "Blocking multiple introductions on the same circuit. " "Someone might be trying to attack a hidden service through " "this relay."); circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL); return -1; } circ->already_received_introduce1 = 1; /* 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 the service's * PK. */ intro_circ = hs_circuitmap_get_intro_circ_v2((const uint8_t*)request); if (!intro_circ) { 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; } 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."); /* Stop right now, the circuit has been closed. */ return -1; } /* And send an ack down the client'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."); /* Stop right now, the circuit has been closed. */ return -1; } return 0; err: /* Send the client a 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."); } 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) { log_warn(LD_PROTOCOL, "Tried to establish rendezvous on non-OR circuit with purpose %s", circuit_purpose_to_string(circ->base_.purpose)); goto err; } if (circ->base_.n_chan) { log_warn(LD_PROTOCOL, "Tried to establish rendezvous on non-edge circuit"); goto err; } if (request_len != REND_COOKIE_LEN) { log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS."); goto err; } if (hs_circuitmap_get_rend_circ(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."); /* Stop right now, the circuit has been closed. */ return -1; } circuit_change_purpose(TO_CIRCUIT(circ), CIRCUIT_PURPOSE_REND_POINT_WAITING); hs_circuitmap_register_rend_circ(circ, request); 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) { const or_options_t *options = get_options(); 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) { 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 = hs_circuitmap_get_rend_circ(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; } /* Statistics: Mark this circuit as an RP circuit so that we collect stats from it. */ if (options->HiddenServiceStatistics) { circ->circuit_carries_hs_traffic_stats = 1; } /* Send the RENDEZVOUS2 cell to the client. */ 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); /* Stop right now, the circuit has been closed. */ return -1; } /* 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); hs_circuitmap_remove_circuit(circ); rend_circ->rend_splice = circ; circ->rend_splice = rend_circ; return 0; err: circuit_mark_for_close(TO_CIRCUIT(circ), reason); return -1; }