command.c

关于tor匿名通信的源代码

 * extend to the next hop in the circuit if necessary.
 */
static void
command_process_created_cell(cell_t *cell, or_connection_t *conn)
{
  circuit_t *circ;

  circ = circuit_get_by_circid_orconn(cell->circ_id, conn);

  if (!circ) {
    log_info(LD_OR,
             "(circID %d) unknown circ (probably got a destroy earlier). "
             "Dropping.", cell->circ_id);
    return;
  }

  if (circ->n_circ_id != cell->circ_id) {
    log_fn(LOG_PROTOCOL_WARN,LD_PROTOCOL,
           "got created cell from Tor client? Closing.");
    circuit_mark_for_close(circ, END_CIRC_REASON_TORPROTOCOL);
    return;
  }

  if (CIRCUIT_IS_ORIGIN(circ)) { /* we're the OP. Handshake this. */
    origin_circuit_t *origin_circ = TO_ORIGIN_CIRCUIT(circ);
    int err_reason = 0;
    log_debug(LD_OR,"at OP. Finishing handshake.");
    if ((err_reason = circuit_finish_handshake(origin_circ, cell->command,
                                 cell->payload)) < 0) {
      log_warn(LD_OR,"circuit_finish_handshake failed.");
      circuit_mark_for_close(circ, -err_reason);
      return;
    }
    log_debug(LD_OR,"Moving to next skin.");
    if ((err_reason = circuit_send_next_onion_skin(origin_circ)) < 0) {
      log_info(LD_OR,"circuit_send_next_onion_skin failed.");
      /* XXX push this circuit_close lower */
      circuit_mark_for_close(circ, -err_reason);
      return;
    }
  } else { /* pack it into an extended relay cell, and send it. */
    log_debug(LD_OR,
              "Converting created cell to extended relay cell, sending.");
    relay_send_command_from_edge(0, circ, RELAY_COMMAND_EXTENDED,
                                 cell->payload, ONIONSKIN_REPLY_LEN,
                                 NULL);
  }
}

/** Process a 'relay' <b>cell</b> that just arrived from <b>conn</b>. Make sure
 * it came in with a recognized circ_id. Pass it on to
 * circuit_receive_relay_cell() for actual processing.
 */
static void
command_process_relay_cell(cell_t *cell, or_connection_t *conn)
{
  circuit_t *circ;
  int reason, direction;

  circ = circuit_get_by_circid_orconn(cell->circ_id, conn);

  if (!circ) {
    log_debug(LD_OR,
              "unknown circuit %d on connection from %s:%d. Dropping.",
              cell->circ_id, conn->_base.address, conn->_base.port);
    return;
  }

  if (circ->state == CIRCUIT_STATE_ONIONSKIN_PENDING) {
    log_fn(LOG_PROTOCOL_WARN,LD_PROTOCOL,"circuit in create_wait. Closing.");
    circuit_mark_for_close(circ, END_CIRC_REASON_TORPROTOCOL);
    return;
  }

  if (CIRCUIT_IS_ORIGIN(circ)) {
    /* if we're a relay and treating connections with recent local
     * traffic better, then this is one of them. */
    conn->client_used = time(NULL);
  }

  if (!CIRCUIT_IS_ORIGIN(circ) &&
      cell->circ_id == TO_OR_CIRCUIT(circ)->p_circ_id)
    direction = CELL_DIRECTION_OUT;
  else
    direction = CELL_DIRECTION_IN;

  if ((reason = circuit_receive_relay_cell(cell, circ, direction)) < 0) {
    log_fn(LOG_PROTOCOL_WARN,LD_PROTOCOL,"circuit_receive_relay_cell "
           "(%s) failed. Closing.",
           direction==CELL_DIRECTION_OUT?"forward":"backward");
    circuit_mark_for_close(circ, -reason);
  }
}

/** Process a 'destroy' <b>cell</b> that just arrived from
 * <b>conn</b>. Find the circ that it refers to (if any).
 *
 * If the circ is in state
 * onionskin_pending, then call onion_pending_remove() to remove it
 * from the pending onion list (note that if it's already being
 * processed by the cpuworker, it won't be in the list anymore; but
 * when the cpuworker returns it, the circuit will be gone, and the
 * cpuworker response will be dropped).
 *
 * Then mark the circuit for close (which marks all edges for close,
 * and passes the destroy cell onward if necessary).
 */
static void
command_process_destroy_cell(cell_t *cell, or_connection_t *conn)
{
  circuit_t *circ;
  int reason;

  circ = circuit_get_by_circid_orconn(cell->circ_id, conn);
  reason = (uint8_t)cell->payload[0];
  if (!circ) {
    log_info(LD_OR,"unknown circuit %d on connection from %s:%d. Dropping.",
             cell->circ_id, conn->_base.address, conn->_base.port);
    return;
  }
  log_debug(LD_OR,"Received for circID %d.",cell->circ_id);

  if (!CIRCUIT_IS_ORIGIN(circ) &&
      cell->circ_id == TO_OR_CIRCUIT(circ)->p_circ_id) {
    /* the destroy came from behind */
    circuit_set_p_circid_orconn(TO_OR_CIRCUIT(circ), 0, NULL);
    circuit_mark_for_close(circ, reason|END_CIRC_REASON_FLAG_REMOTE);
  } else { /* the destroy came from ahead */
    circuit_set_n_circid_orconn(circ, 0, NULL);
    if (CIRCUIT_IS_ORIGIN(circ)) {
      circuit_mark_for_close(circ, reason|END_CIRC_REASON_FLAG_REMOTE);
    } else {
      char payload[1];
      log_debug(LD_OR, "Delivering 'truncated' back.");
      payload[0] = (char)reason;
      relay_send_command_from_edge(0, circ, RELAY_COMMAND_TRUNCATED,
                                   payload, sizeof(payload), NULL);
    }
  }
}

/** Process a 'versions' cell.  The current link protocol version must be 0
 * to indicate that no version has yet been negotiated.  We compare the
 * versions in the cell to the list of versions we support, pick the
 * highest version we have in common, and continue the negotiation from
 * there.
 */
static void
command_process_versions_cell(var_cell_t *cell, or_connection_t *conn)
{
  int highest_supported_version = 0;
  const char *cp, *end;
  if (conn->link_proto != 0 ||
      conn->_base.state != OR_CONN_STATE_OR_HANDSHAKING ||
      (conn->handshake_state && conn->handshake_state->received_versions)) {
    log_fn(LOG_PROTOCOL_WARN, LD_OR,
           "Received a VERSIONS cell on a connection with its version "
           "already set to %d; dropping", (int) conn->link_proto);
    return;
  }
  tor_assert(conn->handshake_state);
  end = cell->payload + cell->payload_len;
  for (cp = cell->payload; cp+1 < end; ++cp) {
    uint16_t v = ntohs(get_uint16(cp));
    if (is_or_protocol_version_known(v) && v > highest_supported_version)
      highest_supported_version = v;
  }
  if (!highest_supported_version) {
    log_fn(LOG_PROTOCOL_WARN, LD_OR,
           "Couldn't find a version in common between my version list and the "
           "list in the VERSIONS cell; closing connection.");
    connection_mark_for_close(TO_CONN(conn));
    return;
  } else if (highest_supported_version == 1) {
    /* Negotiating version 1 makes no sense, since version 1 has no VERSIONS
     * cells. */
    log_fn(LOG_PROTOCOL_WARN, LD_OR,
           "Used version negotiation protocol to negotiate a v1 connection. "
           "That's crazily non-compliant. Closing connection.");
    connection_mark_for_close(TO_CONN(conn));
    return;
  }
  conn->link_proto = highest_supported_version;
  conn->handshake_state->received_versions = 1;

  log_info(LD_OR, "Negotiated version %d with %s; sending NETINFO.",
           highest_supported_version, safe_str(conn->_base.address));
  tor_assert(conn->link_proto >= 2);

  if (connection_or_send_netinfo(conn) < 0) {
    connection_mark_for_close(TO_CONN(conn));
    return;
  }
}

/** Process a 'netinfo' cell: read and act on its contents, and set the
 * connection state to "open". */
static void
command_process_netinfo_cell(cell_t *cell, or_connection_t *conn)
{
  time_t timestamp;
  uint8_t my_addr_type;
  uint8_t my_addr_len;
  const char *my_addr_ptr;
  const char *cp, *end;
  uint8_t n_other_addrs;
  time_t now = time(NULL);

  long apparent_skew = 0;
  uint32_t my_apparent_addr = 0;

  if (conn->link_proto < 2) {
    log_fn(LOG_PROTOCOL_WARN, LD_OR,
           "Received a NETINFO cell on %s connection; dropping.",
           conn->link_proto == 0 ? "non-versioned" : "a v1");
    return;
  }
  if (conn->_base.state != OR_CONN_STATE_OR_HANDSHAKING) {
    log_fn(LOG_PROTOCOL_WARN, LD_OR,
           "Received a NETINFO cell on non-handshaking connection; dropping.");
    return;
  }
  tor_assert(conn->handshake_state &&
             conn->handshake_state->received_versions);
  /* Decode the cell. */
  timestamp = ntohl(get_uint32(cell->payload));
  if (labs(now - conn->handshake_state->sent_versions_at) < 180) {
    apparent_skew = now - timestamp;
  }

  my_addr_type = (uint8_t) cell->payload[4];
  my_addr_len = (uint8_t) cell->payload[5];
  my_addr_ptr = cell->payload + 6;
  end = cell->payload + CELL_PAYLOAD_SIZE;
  cp = cell->payload + 6 + my_addr_len;
  if (cp >= end) {
    log_fn(LOG_PROTOCOL_WARN, LD_OR,
           "Addresses too long in netinfo cell; closing connection.");
    connection_mark_for_close(TO_CONN(conn));
    return;
  } else if (my_addr_type == RESOLVED_TYPE_IPV4 && my_addr_len == 4) {
    my_apparent_addr = ntohl(get_uint32(my_addr_ptr));
  }

  n_other_addrs = (uint8_t) *cp++;
  while (n_other_addrs && cp < end-2) {
    /* Consider all the other addresses; if any matches, this connection is
     * "canonical." */
    uint8_t other_addr_type = (uint8_t) *cp++;
    uint8_t other_addr_len = (uint8_t) *cp++;
    if (cp + other_addr_len >= end) {
      log_fn(LOG_PROTOCOL_WARN, LD_OR,
             "Address too long in netinfo cell; closing connection.");
      connection_mark_for_close(TO_CONN(conn));
      return;
    }
    if (other_addr_type == RESOLVED_TYPE_IPV4 && other_addr_len == 4) {
      uint32_t addr = ntohl(get_uint32(cp));
      if (addr == conn->real_addr) {
        conn->is_canonical = 1;
        break;
      }
    }
    cp += other_addr_len;
    --n_other_addrs;
  }

  /* Act on apparent skew. */
  /** Warn when we get a netinfo skew with at least this value. */
#define NETINFO_NOTICE_SKEW 3600
  if (labs(apparent_skew) > NETINFO_NOTICE_SKEW &&
      router_get_by_digest(conn->identity_digest)) {
    char dbuf[64];
    int severity;
    /*XXXX021 be smarter about when everybody says we are skewed. */
    if (router_digest_is_trusted_dir(conn->identity_digest))
      severity = LOG_WARN;
    else
      severity = LOG_INFO;
    format_time_interval(dbuf, sizeof(dbuf), apparent_skew);
    log_fn(severity, LD_GENERAL, "Received NETINFO cell with skewed time from "
           "server at %s:%d.  It seems that our clock is %s by %s, or "
           "that theirs is %s. Tor requires an accurate clock to work: "
           "please check your time and date settings.",
           conn->_base.address, (int)conn->_base.port,
           apparent_skew>0 ? "ahead" : "behind", dbuf,
           apparent_skew>0 ? "behind" : "ahead");
    control_event_general_status(LOG_WARN,
                        "CLOCK_SKEW SKEW=%ld SOURCE=OR:%s:%d",
                        apparent_skew, conn->_base.address, conn->_base.port);
  }

  /* XXX021 maybe act on my_apparent_addr, if the source is sufficiently
   * trustworthy. */

  if (connection_or_set_state_open(conn)<0)
    connection_mark_for_close(TO_CONN(conn));
  else
    log_info(LD_OR, "Got good NETINFO cell from %s; OR connection is now "
             "open, using protocol version %d",
             safe_str(conn->_base.address), (int)conn->link_proto);
  assert_connection_ok(TO_CONN(conn),time(NULL));
}