circuituse.c

关于tor匿名通信的源代码

                                            conn->socks_request->port);
          } else {
            /* We will need an onion key for the router, and we
             * don't have one. Refuse or relax requirements. */
            log_fn(opt ? LOG_INFO : LOG_WARN, LD_APP,
                   "Requested exit point '%s' is not known. %s.",
                   conn->chosen_exit_name, opt ? "Trying others" : "Closing");
            if (opt) {
              conn->_base.chosen_exit_optional = 0;
              tor_free(conn->chosen_exit_name);
              return 0;
            }
            return -1;
          }
        }
      }
    }

    if (desired_circuit_purpose == CIRCUIT_PURPOSE_C_REND_JOINED)
      new_circ_purpose = CIRCUIT_PURPOSE_C_ESTABLISH_REND;
    else if (desired_circuit_purpose == CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT)
      new_circ_purpose = CIRCUIT_PURPOSE_C_INTRODUCING;
    else
      new_circ_purpose = desired_circuit_purpose;

    {
      int flags = CIRCLAUNCH_NEED_CAPACITY;
      if (want_onehop) flags |= CIRCLAUNCH_ONEHOP_TUNNEL;
      if (need_uptime) flags |= CIRCLAUNCH_NEED_UPTIME;
      if (need_internal) flags |= CIRCLAUNCH_IS_INTERNAL;
      circ = circuit_launch_by_extend_info(new_circ_purpose, extend_info,
                                           flags);
    }

    if (extend_info)
      extend_info_free(extend_info);

    if (desired_circuit_purpose != CIRCUIT_PURPOSE_C_GENERAL) {
      /* help predict this next time */
      rep_hist_note_used_internal(time(NULL), need_uptime, 1);
      if (circ) {
        /* write the service_id into circ */
        strlcpy(circ->rend_query, conn->rend_query, sizeof(circ->rend_query));
        if (circ->_base.purpose == CIRCUIT_PURPOSE_C_ESTABLISH_REND &&
            circ->_base.state == CIRCUIT_STATE_OPEN)
          rend_client_rendcirc_has_opened(circ);
      }
    }
  }
  if (!circ)
    log_info(LD_APP,
             "No safe circuit (purpose %d) ready for edge "
             "connection; delaying.",
             desired_circuit_purpose);
  *circp = circ;
  return 0;
}

/** Return true iff <b>crypt_path</b> is one of the crypt_paths for
 * <b>circ</b>. */
static int
cpath_is_on_circuit(origin_circuit_t *circ, crypt_path_t *crypt_path)
{
  crypt_path_t *cpath, *cpath_next = NULL;
  for (cpath = circ->cpath; cpath_next != circ->cpath; cpath = cpath_next) {
    cpath_next = cpath->next;
    if (crypt_path == cpath)
      return 1;
  }
  return 0;
}

/** Attach the AP stream <b>apconn</b> to circ's linked list of
 * p_streams. Also set apconn's cpath_layer to <b>cpath</b>, or to the last
 * hop in circ's cpath if <b>cpath</b> is NULL.
 */
static void
link_apconn_to_circ(edge_connection_t *apconn, origin_circuit_t *circ,
                    crypt_path_t *cpath)
{
  /* add it into the linked list of streams on this circuit */
  log_debug(LD_APP|LD_CIRC, "attaching new conn to circ. n_circ_id %d.",
            circ->_base.n_circ_id);
  /* reset it, so we can measure circ timeouts */
  apconn->_base.timestamp_lastread = time(NULL);
  apconn->next_stream = circ->p_streams;
  apconn->on_circuit = TO_CIRCUIT(circ);
  /* assert_connection_ok(conn, time(NULL)); */
  circ->p_streams = apconn;

  if (cpath) { /* we were given one; use it */
    tor_assert(cpath_is_on_circuit(circ, cpath));
    apconn->cpath_layer = cpath;
  } else { /* use the last hop in the circuit */
    tor_assert(circ->cpath);
    tor_assert(circ->cpath->prev);
    tor_assert(circ->cpath->prev->state == CPATH_STATE_OPEN);
    apconn->cpath_layer = circ->cpath->prev;
  }
}

/** If an exit wasn't specifically chosen, save the history for future
 * use. */
static void
consider_recording_trackhost(edge_connection_t *conn, origin_circuit_t *circ)
{
  int found_needle = 0;
  or_options_t *options = get_options();
  size_t len;
  char *new_address;
  char fp[HEX_DIGEST_LEN+1];

  /* Search the addressmap for this conn's destination. */
  /* If he's not in the address map.. */
  if (!options->TrackHostExits ||
      addressmap_have_mapping(conn->socks_request->address))
    return; /* nothing to track, or already mapped */

  SMARTLIST_FOREACH(options->TrackHostExits, const char *, cp, {
    if (cp[0] == '.') { /* match end */
      if (cp[1] == '\0' ||
          !strcasecmpend(conn->socks_request->address, cp) ||
          !strcasecmp(conn->socks_request->address, &cp[1]))
          found_needle = 1;
    } else if (strcasecmp(cp, conn->socks_request->address) == 0) {
      found_needle = 1;
    }
  });

  if (!found_needle || !circ->build_state->chosen_exit)
    return;

  /* write down the fingerprint of the chosen exit, not the nickname,
   * because the chosen exit might not be named. */
  base16_encode(fp, sizeof(fp),
                circ->build_state->chosen_exit->identity_digest, DIGEST_LEN);

  /* Add this exit/hostname pair to the addressmap. */
  len = strlen(conn->socks_request->address) + 1 /* '.' */ +
        strlen(fp) + 1 /* '.' */ +
        strlen("exit") + 1 /* '\0' */;
  new_address = tor_malloc(len);

  tor_snprintf(new_address, len, "%s.%s.exit",
               conn->socks_request->address, fp);

  addressmap_register(conn->socks_request->address, new_address,
                      time(NULL) + options->TrackHostExitsExpire,
                      ADDRMAPSRC_TRACKEXIT);
}

/** Attempt to attach the connection <b>conn</b> to <b>circ</b>, and send a
 * begin or resolve cell as appropriate.  Return values are as for
 * connection_ap_handshake_attach_circuit.  The stream will exit from the hop
 * indicated by <b>cpath</b>, or from the last hop in circ's cpath if
 * <b>cpath</b> is NULL. */
int
connection_ap_handshake_attach_chosen_circuit(edge_connection_t *conn,
                                              origin_circuit_t *circ,
                                              crypt_path_t *cpath)
{
  tor_assert(conn);
  tor_assert(conn->_base.state == AP_CONN_STATE_CIRCUIT_WAIT ||
             conn->_base.state == AP_CONN_STATE_CONTROLLER_WAIT);
  tor_assert(conn->socks_request);
  tor_assert(circ);
  tor_assert(circ->_base.state == CIRCUIT_STATE_OPEN);

  conn->_base.state = AP_CONN_STATE_CIRCUIT_WAIT;

  if (!circ->_base.timestamp_dirty)
    circ->_base.timestamp_dirty = time(NULL);

  link_apconn_to_circ(conn, circ, cpath);
  tor_assert(conn->socks_request);
  if (conn->socks_request->command == SOCKS_COMMAND_CONNECT) {
    if (!conn->use_begindir)
      consider_recording_trackhost(conn, circ);
    if (connection_ap_handshake_send_begin(conn) < 0)
      return -1;
  } else {
    if (connection_ap_handshake_send_resolve(conn) < 0)
      return -1;
  }

  return 1;
}

/** Try to find a safe live circuit for CONN_TYPE_AP connection conn. If
 * we don't find one: if conn cannot be handled by any known nodes,
 * warn and return -1 (conn needs to die, and is maybe already marked);
 * else launch new circuit (if necessary) and return 0.
 * Otherwise, associate conn with a safe live circuit, do the
 * right next step, and return 1.
 */
/* XXXX021 this function should mark for close whenever it returns -1;
 * its callers shouldn't have to worry about that. */
int
connection_ap_handshake_attach_circuit(edge_connection_t *conn)
{
  int retval;
  int conn_age;
  int want_onehop;

  tor_assert(conn);
  tor_assert(conn->_base.state == AP_CONN_STATE_CIRCUIT_WAIT);
  tor_assert(conn->socks_request);
  want_onehop = conn->want_onehop;

  conn_age = (int)(time(NULL) - conn->_base.timestamp_created);

  if (conn_age >= get_options()->SocksTimeout) {
    int severity = (!conn->_base.addr && !conn->_base.port) ?
                     LOG_INFO : LOG_NOTICE;
    log_fn(severity, LD_APP,
           "Tried for %d seconds to get a connection to %s:%d. Giving up.",
           conn_age, safe_str(conn->socks_request->address),
           conn->socks_request->port);
    return -1;
  }

  if (!connection_edge_is_rendezvous_stream(conn)) { /* we're a general conn */
    origin_circuit_t *circ=NULL;

    if (conn->chosen_exit_name) {
      routerinfo_t *router = router_get_by_nickname(conn->chosen_exit_name, 1);
      int opt = conn->_base.chosen_exit_optional;
      if (!router && !want_onehop) {
        log_fn(opt ? LOG_INFO : LOG_WARN, LD_APP,
               "Requested exit point '%s' is not known. %s.",
               conn->chosen_exit_name, opt ? "Trying others" : "Closing");
        if (opt) {
          conn->_base.chosen_exit_optional = 0;
          tor_free(conn->chosen_exit_name);
          return 0;
        }
        return -1;
      }
      if (router && !connection_ap_can_use_exit(conn, router)) {
        log_fn(opt ? LOG_INFO : LOG_WARN, LD_APP,
               "Requested exit point '%s' would refuse request. %s.",
               conn->chosen_exit_name, opt ? "Trying others" : "Closing");
        if (opt) {
          conn->_base.chosen_exit_optional = 0;
          tor_free(conn->chosen_exit_name);
          return 0;
        }
        return -1;
      }
    }

    /* find the circuit that we should use, if there is one. */
    retval = circuit_get_open_circ_or_launch(
        conn, CIRCUIT_PURPOSE_C_GENERAL, &circ);
    if (retval < 1)
      return retval;

    log_debug(LD_APP|LD_CIRC,
              "Attaching apconn to circ %d (stream %d sec old).",
              circ->_base.n_circ_id, conn_age);
    /* print the circ's path, so people can figure out which circs are
     * sucking. */
    circuit_log_path(LOG_INFO,LD_APP|LD_CIRC,circ);

    /* We have found a suitable circuit for our conn. Hurray. */
    return connection_ap_handshake_attach_chosen_circuit(conn, circ, NULL);

  } else { /* we're a rendezvous conn */
    origin_circuit_t *rendcirc=NULL, *introcirc=NULL;

    tor_assert(!conn->cpath_layer);

    /* start by finding a rendezvous circuit for us */

    retval = circuit_get_open_circ_or_launch(
       conn, CIRCUIT_PURPOSE_C_REND_JOINED, &rendcirc);
    if (retval < 0) return -1; /* failed */

    if (retval > 0) {
      tor_assert(rendcirc);
      /* one is already established, attach */
      log_info(LD_REND,
               "rend joined circ %d already here. attaching. "
               "(stream %d sec old)",
               rendcirc->_base.n_circ_id, conn_age);
      /* Mark rendezvous circuits as 'newly dirty' every time you use
       * them, since the process of rebuilding a rendezvous circ is so
       * expensive. There is a tradeoffs between linkability and
       * feasibility, at this point.
       */
      rendcirc->_base.timestamp_dirty = time(NULL);
      link_apconn_to_circ(conn, rendcirc, NULL);
      if (connection_ap_handshake_send_begin(conn) < 0)
        return 0; /* already marked, let them fade away */
      return 1;
    }

    if (rendcirc && (rendcirc->_base.purpose ==
                     CIRCUIT_PURPOSE_C_REND_READY_INTRO_ACKED)) {
      log_info(LD_REND,
               "pending-join circ %d already here, with intro ack. "
               "Stalling. (stream %d sec old)",
                rendcirc->_base.n_circ_id, conn_age);
      return 0;
    }

    /* it's on its way. find an intro circ. */
    retval = circuit_get_open_circ_or_launch(
      conn, CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT, &introcirc);
    if (retval < 0) return -1; /* failed */

    if (retval > 0) {
      /* one has already sent the intro. keep waiting. */
      tor_assert(introcirc);
      log_info(LD_REND, "Intro circ %d present and awaiting ack (rend %d). "
               "Stalling. (stream %d sec old)",
               introcirc->_base.n_circ_id,
               rendcirc ? rendcirc->_base.n_circ_id : 0,
               conn_age);
      return 0;
    }

    /* now rendcirc and introcirc are each either undefined or not finished */

    if (rendcirc && introcirc &&
        rendcirc->_base.purpose == CIRCUIT_PURPOSE_C_REND_READY) {
      log_info(LD_REND,
               "ready rend circ %d already here (no intro-ack yet on "
               "intro %d). (stream %d sec old)",
               rendcirc->_base.n_circ_id,
               introcirc->_base.n_circ_id, conn_age);

      tor_assert(introcirc->_base.purpose == CIRCUIT_PURPOSE_C_INTRODUCING);
      if (introcirc->_base.state == CIRCUIT_STATE_OPEN) {
        log_info(LD_REND,"found open intro circ %d (rend %d); sending "
                 "introduction. (stream %d sec old)",
                 introcirc->_base.n_circ_id, rendcirc->_base.n_circ_id,
                 conn_age);
        if (rend_client_send_introduction(introcirc, rendcirc) < 0) {
          return -1;
        }
        rendcirc->_base.timestamp_dirty = time(NULL);
        introcirc->_base.timestamp_dirty = time(NULL);
        assert_circuit_ok(TO_CIRCUIT(rendcirc));
        assert_circuit_ok(TO_CIRCUIT(introcirc));
        return 0;
      }
    }

    log_info(LD_REND, "Intro (%d) and rend (%d) circs are not both ready. "
             "Stalling conn. (%d sec old)",
             introcirc ? introcirc->_base.n_circ_id : 0,
             rendcirc ? rendcirc->_base.n_circ_id : 0, conn_age);
    return 0;
  }
}