rendclient.c

关于tor匿名通信的源代码

                desc_id, DIGEST_LEN);

  /* Only select those hidden service directories to which we did not send
   * a request recently. */
  directory_clean_last_hid_serv_requests(); /* Clean request history first. */

  SMARTLIST_FOREACH(responsible_dirs, routerstatus_t *, dir, {
    if (lookup_last_hid_serv_request(dir, desc_id_base32, 0, 0) +
        REND_HID_SERV_DIR_REQUERY_PERIOD >= now)
      SMARTLIST_DEL_CURRENT(responsible_dirs, dir);
  });

  hs_dir = smartlist_choose(responsible_dirs);
  smartlist_free(responsible_dirs);
  if (!hs_dir) {
    log_info(LD_REND, "Could not pick one of the responsible hidden "
                      "service directories, because we requested them all "
                      "recently without success.");
    return 0;
  }

  /* Remember, that we are requesting a descriptor from this hidden service
   * directory now. */
  lookup_last_hid_serv_request(hs_dir, desc_id_base32, now, 1);

  /* Send fetch request. (Pass query as payload to write it to the directory
   * connection so that it can be referred to when the response arrives.) */
  directory_initiate_command_routerstatus(hs_dir,
                                          DIR_PURPOSE_FETCH_RENDDESC_V2,
                                          ROUTER_PURPOSE_GENERAL,
                                          1, desc_id_base32, query, 0, 0);
  log_info(LD_REND, "Sending fetch request for v2 descriptor for "
                    "service '%s' with descriptor ID '%s' to hidden "
                    "service directory '%s' on port %d.",
           safe_str(query), safe_str(desc_id_base32), hs_dir->nickname,
           hs_dir->dir_port);
  return 1;
}

/** If we are not currently fetching a rendezvous service descriptor
 * for the service ID <b>query</b>, start a directory connection to fetch a
 * new one.
 */
void
rend_client_refetch_renddesc(const char *query)
{
  if (!get_options()->FetchHidServDescriptors)
    return;
  log_info(LD_REND, "Fetching rendezvous descriptor for service %s",
           escaped_safe_str(query));
  if (connection_get_by_type_state_rendquery(CONN_TYPE_DIR, 0, query, 0)) {
    log_info(LD_REND,"Would fetch a new renddesc here (for %s), but one is "
             "already in progress.", escaped_safe_str(query));
  } else {
    /* not one already; initiate a dir rend desc lookup */
    directory_get_from_dirserver(DIR_PURPOSE_FETCH_RENDDESC,
                                 ROUTER_PURPOSE_GENERAL, query, 1);
  }
}

/** Start a connection to a hidden service directory to fetch a v2
 * rendezvous service descriptor for the base32-encoded service ID
 * <b>query</b>.
 */
void
rend_client_refetch_v2_renddesc(const char *query)
{
  char descriptor_id[DIGEST_LEN];
  int replicas_left_to_try[REND_NUMBER_OF_NON_CONSECUTIVE_REPLICAS];
  int i, tries_left;
  rend_cache_entry_t *e = NULL;
  tor_assert(query);
  tor_assert(strlen(query) == REND_SERVICE_ID_LEN_BASE32);
  /* Are we configured to fetch descriptors? */
  if (!get_options()->FetchHidServDescriptors) {
    log_warn(LD_REND, "We received an onion address for a v2 rendezvous "
        "service descriptor, but are not fetching service descriptors.");
    return;
  }
  /* Before fetching, check if we already have the descriptor here. */
  if (rend_cache_lookup_entry(query, -1, &e) > 0) {
    log_info(LD_REND, "We would fetch a v2 rendezvous descriptor, but we "
                      "already have that descriptor here. Not fetching.");
    return;
  }
  log_debug(LD_REND, "Fetching v2 rendezvous descriptor for service %s",
            safe_str(query));
  /* Randomly iterate over the replicas until a descriptor can be fetched
   * from one of the consecutive nodes, or no options are left. */
  tries_left = REND_NUMBER_OF_NON_CONSECUTIVE_REPLICAS;
  for (i = 0; i < REND_NUMBER_OF_NON_CONSECUTIVE_REPLICAS; i++)
    replicas_left_to_try[i] = i;
  while (tries_left > 0) {
    int rand = crypto_rand_int(tries_left);
    int chosen_replica = replicas_left_to_try[rand];
    replicas_left_to_try[rand] = replicas_left_to_try[--tries_left];

    if (rend_compute_v2_desc_id(descriptor_id, query, NULL, time(NULL),
                                chosen_replica) < 0) {
      log_warn(LD_REND, "Internal error: Computing v2 rendezvous "
                        "descriptor ID did not succeed.");
      return;
    }
    if (directory_get_from_hs_dir(descriptor_id, query) != 0)
      return; /* either success or failure, but we're done */
  }
  /* If we come here, there are no hidden service directories left. */
  log_info(LD_REND, "Could not pick one of the responsible hidden "
                    "service directories to fetch descriptors, because "
                    "we already tried them all unsuccessfully.");
  return;
}

/** Remove failed_intro from ent. If ent now has no intro points, or
 * service is unrecognized, then launch a new renddesc fetch.
 *
 * Return -1 if error, 0 if no intro points remain or service
 * unrecognized, 1 if recognized and some intro points remain.
 */
int
rend_client_remove_intro_point(extend_info_t *failed_intro, const char *query)
{
  int i, r;
  rend_cache_entry_t *ent;
  connection_t *conn;

  r = rend_cache_lookup_entry(query, -1, &ent);
  if (r<0) {
    log_warn(LD_BUG, "Malformed service ID %s.", escaped_safe_str(query));
    return -1;
  }
  if (r==0) {
    log_info(LD_REND, "Unknown service %s. Re-fetching descriptor.",
             escaped_safe_str(query));
    /* Fetch both, v0 and v2 rend descriptors in parallel. Use whichever
     * arrives first. */
    rend_client_refetch_v2_renddesc(query);
    rend_client_refetch_renddesc(query);
    return 0;
  }

  for (i = 0; i < smartlist_len(ent->parsed->intro_nodes); i++) {
    rend_intro_point_t *intro = smartlist_get(ent->parsed->intro_nodes, i);
    if (!memcmp(failed_intro->identity_digest,
                intro->extend_info->identity_digest, DIGEST_LEN)) {
      rend_intro_point_free(intro);
      smartlist_del(ent->parsed->intro_nodes, i);
      break;
    }
  }

  if (smartlist_len(ent->parsed->intro_nodes) == 0) {
    log_info(LD_REND,
             "No more intro points remain for %s. Re-fetching descriptor.",
             escaped_safe_str(query));
    /* Fetch both, v0 and v2 rend descriptors in parallel. Use whichever
     * arrives first. */
    rend_client_refetch_v2_renddesc(query);
    rend_client_refetch_renddesc(query);

    /* move all pending streams back to renddesc_wait */
    while ((conn = connection_get_by_type_state_rendquery(CONN_TYPE_AP,
                                   AP_CONN_STATE_CIRCUIT_WAIT, query, -1))) {
      conn->state = AP_CONN_STATE_RENDDESC_WAIT;
    }

    return 0;
  }
  log_info(LD_REND,"%d options left for %s.",
           smartlist_len(ent->parsed->intro_nodes), escaped_safe_str(query));
  return 1;
}

/** Called when we receive a RENDEZVOUS_ESTABLISHED cell; changes the state of
 * the circuit to C_REND_READY.
 */
int
rend_client_rendezvous_acked(origin_circuit_t *circ, const char *request,
                             size_t request_len)
{
  (void) request;
  (void) request_len;
  /* we just got an ack for our establish-rendezvous. switch purposes. */
  if (circ->_base.purpose != CIRCUIT_PURPOSE_C_ESTABLISH_REND) {
    log_warn(LD_PROTOCOL,"Got a rendezvous ack when we weren't expecting one. "
             "Closing circ.");
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
    return -1;
  }
  log_info(LD_REND,"Got rendezvous ack. This circuit is now ready for "
           "rendezvous.");
  circ->_base.purpose = CIRCUIT_PURPOSE_C_REND_READY;
  return 0;
}

/** Bob sent us a rendezvous cell; join the circuits. */
int
rend_client_receive_rendezvous(origin_circuit_t *circ, const char *request,
                               size_t request_len)
{
  crypt_path_t *hop;
  char keys[DIGEST_LEN+CPATH_KEY_MATERIAL_LEN];

  if ((circ->_base.purpose != CIRCUIT_PURPOSE_C_REND_READY &&
       circ->_base.purpose != CIRCUIT_PURPOSE_C_REND_READY_INTRO_ACKED)
      || !circ->build_state->pending_final_cpath) {
    log_warn(LD_PROTOCOL,"Got rendezvous2 cell from hidden service, but not "
             "expecting it. Closing.");
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
    return -1;
  }

  if (request_len != DH_KEY_LEN+DIGEST_LEN) {
    log_warn(LD_PROTOCOL,"Incorrect length (%d) on RENDEZVOUS2 cell.",
             (int)request_len);
    goto err;
  }

  log_info(LD_REND,"Got RENDEZVOUS2 cell from hidden service.");

  /* first DH_KEY_LEN bytes are g^y from bob. Finish the dh handshake...*/
  tor_assert(circ->build_state);
  tor_assert(circ->build_state->pending_final_cpath);
  hop = circ->build_state->pending_final_cpath;
  tor_assert(hop->dh_handshake_state);
  if (crypto_dh_compute_secret(hop->dh_handshake_state, request, DH_KEY_LEN,
                               keys, DIGEST_LEN+CPATH_KEY_MATERIAL_LEN)<0) {
    log_warn(LD_GENERAL, "Couldn't complete DH handshake.");
    goto err;
  }
  /* ... and set up cpath. */
  if (circuit_init_cpath_crypto(hop, keys+DIGEST_LEN, 0)<0)
    goto err;

  /* Check whether the digest is right... */
  if (memcmp(keys, request+DH_KEY_LEN, DIGEST_LEN)) {
    log_warn(LD_PROTOCOL, "Incorrect digest of key material.");
    goto err;
  }

  crypto_dh_free(hop->dh_handshake_state);
  hop->dh_handshake_state = NULL;

  /* All is well. Extend the circuit. */
  circ->_base.purpose = CIRCUIT_PURPOSE_C_REND_JOINED;
  hop->state = CPATH_STATE_OPEN;
  /* set the windows to default. these are the windows
   * that alice thinks bob has.
   */
  hop->package_window = CIRCWINDOW_START;
  hop->deliver_window = CIRCWINDOW_START;

  onion_append_to_cpath(&circ->cpath, hop);
  circ->build_state->pending_final_cpath = NULL; /* prevent double-free */
  return 0;
 err:
  circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
  return -1;
}

/** Find all the apconns in state AP_CONN_STATE_RENDDESC_WAIT that
 * are waiting on query. If there's a working cache entry here
 * with at least one intro point, move them to the next state;
 * else fail them.
 */
void
rend_client_desc_here(const char *query)
{
  edge_connection_t *conn;
  rend_cache_entry_t *entry;
  time_t now = time(NULL);

  smartlist_t *conns = get_connection_array();
  SMARTLIST_FOREACH(conns, connection_t *, _conn,
  {
    if (_conn->type != CONN_TYPE_AP ||
        _conn->state != AP_CONN_STATE_RENDDESC_WAIT ||
        _conn->marked_for_close)
      continue;
    conn = TO_EDGE_CONN(_conn);
    if (rend_cmp_service_ids(query, conn->rend_query))
      continue;
    assert_connection_ok(TO_CONN(conn), now);
    if (rend_cache_lookup_entry(conn->rend_query, -1, &entry) == 1 &&
        smartlist_len(entry->parsed->intro_nodes) > 0) {
      /* either this fetch worked, or it failed but there was a
       * valid entry from before which we should reuse */
      log_info(LD_REND,"Rend desc is usable. Launching circuits.");
      conn->_base.state = AP_CONN_STATE_CIRCUIT_WAIT;

      /* restart their timeout values, so they get a fair shake at
       * connecting to the hidden service. */
      conn->_base.timestamp_created = now;
      conn->_base.timestamp_lastread = now;
      conn->_base.timestamp_lastwritten = now;

      if (connection_ap_handshake_attach_circuit(conn) < 0) {
        /* it will never work */
        log_warn(LD_REND,"Rendezvous attempt failed. Closing.");
        if (!conn->_base.marked_for_close)
          connection_mark_unattached_ap(conn, END_STREAM_REASON_CANT_ATTACH);
      }
    } else { /* 404, or fetch didn't get that far */
      log_notice(LD_REND,"Closing stream for '%s.onion': hidden service is "
                 "unavailable (try again later).", safe_str(query));
      connection_mark_unattached_ap(conn, END_STREAM_REASON_RESOLVEFAILED);
    }
  });
}

/** Return a newly allocated extend_info_t* for a randomly chosen introduction
 * point for the named hidden service.  Return NULL if all introduction points
 * have been tried and failed.
 */
extend_info_t *
rend_client_get_random_intro(const char *query)
{
  int i;
  rend_cache_entry_t *entry;
  rend_intro_point_t *intro;
  routerinfo_t *router;

  if (rend_cache_lookup_entry(query, -1, &entry) < 1) {
    log_warn(LD_REND,
             "Query '%s' didn't have valid rend desc in cache. Failing.",
             safe_str(query));
    return NULL;
  }

 again:
  if (smartlist_len(entry->parsed->intro_nodes) == 0)
    return NULL;

  i = crypto_rand_int(smartlist_len(entry->parsed->intro_nodes));
  intro = smartlist_get(entry->parsed->intro_nodes, i);
  /* Do we need to look up the router or is the extend info complete? */
  if (!intro->extend_info->onion_key) {
    router = router_get_by_nickname(intro->extend_info->nickname, 0);
    if (!router) {
      log_info(LD_REND, "Unknown router with nickname '%s'; trying another.",
               intro->extend_info->nickname);
      rend_intro_point_free(intro);
      smartlist_del(entry->parsed->intro_nodes, i);
      goto again;
    }
    extend_info_free(intro->extend_info);
    intro->extend_info = extend_info_from_router(router);
  }
  return extend_info_dup(intro->extend_info);
}