text: /* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   * Copyright (c) 2007-2017, 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 "crypto.h"
  #include "relay.h"
  #include "rendmid.h"
  #include "rephist.h"
  #include "hs_circuitmap.h"
  #include "hs_intropoint.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_legacy(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 a legacy ESTABLISH_INTRO request on circuit %u",
             (unsigned) circ->p_circ_id);
  
    if (!hs_intro_circuit_is_suitable_for_establish_intro(circ)) {
      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 */
    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_relay_side(
                                                  (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 (hs_intro_send_intro_established_cell(circ) < 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_relay_side(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_legacy(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);
  
    /* At this point, we know that the circuit is valid for an INTRODUCE1
     * because the validation has been made before calling this function. */
    tor_assert(circ->base_.purpose == CIRCUIT_PURPOSE_OR);
    tor_assert(!circ->base_.n_chan);
  
    /* 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_relay_side(
                                                        (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_relay_side(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_relay_side(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_relay_side(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(TO_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;
  }
  
  