circuitbuild.c

关于tor匿名通信的源代码

    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
           "Wrong length %d on extend cell. Closing circuit.",
           rh.length);
    return -1;
  }

  circ->n_addr = ntohl(get_uint32(cell->payload+RELAY_HEADER_SIZE));
  circ->n_port = ntohs(get_uint16(cell->payload+RELAY_HEADER_SIZE+4));

  onionskin = cell->payload+RELAY_HEADER_SIZE+4+2;
  id_digest = cell->payload+RELAY_HEADER_SIZE+4+2+ONIONSKIN_CHALLENGE_LEN;
  n_conn = connection_or_get_by_identity_digest(id_digest);

  /* If we don't have an open conn, or the conn we have is obsolete
   * (i.e. old or broken) and the other side will let us make a second
   * connection without dropping it immediately... */
  if (!n_conn || n_conn->_base.state != OR_CONN_STATE_OPEN ||
    (n_conn->_base.or_is_obsolete &&
     router_digest_version_as_new_as(id_digest,"0.1.1.9-alpha-cvs"))) {
    struct in_addr in;
    char tmpbuf[INET_NTOA_BUF_LEN];
    in.s_addr = htonl(circ->n_addr);
    tor_inet_ntoa(&in,tmpbuf,sizeof(tmpbuf));
    log_debug(LD_CIRC|LD_OR,"Next router (%s:%d) not connected. Connecting.",
              tmpbuf, circ->n_port);

    circ->n_conn_onionskin = tor_malloc(ONIONSKIN_CHALLENGE_LEN);
    memcpy(circ->n_conn_onionskin, onionskin, ONIONSKIN_CHALLENGE_LEN);
    circuit_set_state(circ, CIRCUIT_STATE_OR_WAIT);

    /* imprint the circuit with its future n_conn->id */
    memcpy(circ->n_conn_id_digest, id_digest, DIGEST_LEN);

    if (n_conn && !n_conn->_base.or_is_obsolete) {
      circ->n_addr = n_conn->_base.addr;
      circ->n_port = n_conn->_base.port;
    } else {
     /* we should try to open a connection */
      n_conn = connection_or_connect(circ->n_addr, circ->n_port, id_digest);
      if (!n_conn) {
        log_info(LD_CIRC,"Launching n_conn failed. Closing circuit.");
        circuit_mark_for_close(circ, END_CIRC_REASON_CONNECTFAILED);
        return 0;
      }
      log_debug(LD_CIRC,"connecting in progress (or finished). Good.");
    }
    /* return success. The onion/circuit/etc will be taken care of
     * automatically (may already have been) whenever n_conn reaches
     * OR_CONN_STATE_OPEN.
     */
    return 0;
  }

  /* these may be different if the router connected to us from elsewhere */
  circ->n_addr = n_conn->_base.addr;
  circ->n_port = n_conn->_base.port;

  circ->n_conn = n_conn;
  memcpy(circ->n_conn_id_digest, n_conn->identity_digest, DIGEST_LEN);
  log_debug(LD_CIRC,"n_conn is %s:%u",
            n_conn->_base.address,n_conn->_base.port);

  if (circuit_deliver_create_cell(circ, CELL_CREATE, onionskin) < 0)
    return -1;
  return 0;
}

/** Initialize cpath-\>{f|b}_{crypto|digest} from the key material in
 * key_data.  key_data must contain CPATH_KEY_MATERIAL bytes, which are
 * used as follows:
 *   - 20 to initialize f_digest
 *   - 20 to initialize b_digest
 *   - 16 to key f_crypto
 *   - 16 to key b_crypto
 *
 * (If 'reverse' is true, then f_XX and b_XX are swapped.)
 */
int
circuit_init_cpath_crypto(crypt_path_t *cpath, const char *key_data,
                          int reverse)
{
  crypto_digest_env_t *tmp_digest;
  crypto_cipher_env_t *tmp_crypto;

  tor_assert(cpath);
  tor_assert(key_data);
  tor_assert(!(cpath->f_crypto || cpath->b_crypto ||
             cpath->f_digest || cpath->b_digest));

  cpath->f_digest = crypto_new_digest_env();
  crypto_digest_add_bytes(cpath->f_digest, key_data, DIGEST_LEN);
  cpath->b_digest = crypto_new_digest_env();
  crypto_digest_add_bytes(cpath->b_digest, key_data+DIGEST_LEN, DIGEST_LEN);

  if (!(cpath->f_crypto =
        crypto_create_init_cipher(key_data+(2*DIGEST_LEN),1))) {
    log_warn(LD_BUG,"Forward cipher initialization failed.");
    return -1;
  }
  if (!(cpath->b_crypto =
        crypto_create_init_cipher(key_data+(2*DIGEST_LEN)+CIPHER_KEY_LEN,0))) {
    log_warn(LD_BUG,"Backward cipher initialization failed.");
    return -1;
  }

  if (reverse) {
    tmp_digest = cpath->f_digest;
    cpath->f_digest = cpath->b_digest;
    cpath->b_digest = tmp_digest;
    tmp_crypto = cpath->f_crypto;
    cpath->f_crypto = cpath->b_crypto;
    cpath->b_crypto = tmp_crypto;
  }

  return 0;
}

/** A created or extended cell came back to us on the circuit, and it included
 * <b>reply</b> as its body.  (If <b>reply_type</b> is CELL_CREATED, the body
 * contains (the second DH key, plus KH).  If <b>reply_type</b> is
 * CELL_CREATED_FAST, the body contains a secret y and a hash H(x|y).)
 *
 * Calculate the appropriate keys and digests, make sure KH is
 * correct, and initialize this hop of the cpath.
 *
 * Return - reason if we want to mark circ for close, else return 0.
 */
int
circuit_finish_handshake(origin_circuit_t *circ, uint8_t reply_type,
                         const char *reply)
{
  char keys[CPATH_KEY_MATERIAL_LEN];
  crypt_path_t *hop;

  if (circ->cpath->state == CPATH_STATE_AWAITING_KEYS)
    hop = circ->cpath;
  else {
    hop = onion_next_hop_in_cpath(circ->cpath);
    if (!hop) { /* got an extended when we're all done? */
      log_warn(LD_PROTOCOL,"got extended when circ already built? Closing.");
      return - END_CIRC_REASON_TORPROTOCOL;
    }
  }
  tor_assert(hop->state == CPATH_STATE_AWAITING_KEYS);

  if (reply_type == CELL_CREATED && hop->dh_handshake_state) {
    if (onion_skin_client_handshake(hop->dh_handshake_state, reply, keys,
                                    DIGEST_LEN*2+CIPHER_KEY_LEN*2) < 0) {
      log_warn(LD_CIRC,"onion_skin_client_handshake failed.");
      return -END_CIRC_REASON_TORPROTOCOL;
    }
    /* Remember hash of g^xy */
    memcpy(hop->handshake_digest, reply+DH_KEY_LEN, DIGEST_LEN);
  } else if (reply_type == CELL_CREATED_FAST && !hop->dh_handshake_state) {
    if (fast_client_handshake(hop->fast_handshake_state, reply, keys,
                              DIGEST_LEN*2+CIPHER_KEY_LEN*2) < 0) {
      log_warn(LD_CIRC,"fast_client_handshake failed.");
      return -END_CIRC_REASON_TORPROTOCOL;
    }
    memcpy(hop->handshake_digest, reply+DIGEST_LEN, DIGEST_LEN);
  } else {
    log_warn(LD_PROTOCOL,"CREATED cell type did not match CREATE cell type.");
    return -END_CIRC_REASON_TORPROTOCOL;
  }

  if (hop->dh_handshake_state) {
    crypto_dh_free(hop->dh_handshake_state); /* don't need it anymore */
    hop->dh_handshake_state = NULL;
  }
  memset(hop->fast_handshake_state, 0, sizeof(hop->fast_handshake_state));

  if (circuit_init_cpath_crypto(hop, keys, 0)<0) {
    return -END_CIRC_REASON_TORPROTOCOL;
  }

  hop->state = CPATH_STATE_OPEN;
  log_info(LD_CIRC,"Finished building %scircuit hop:",
           (reply_type == CELL_CREATED_FAST) ? "fast " : "");
  circuit_log_path(LOG_INFO,LD_CIRC,circ);
  control_event_circuit_status(circ, CIRC_EVENT_EXTENDED, 0);

  return 0;
}

/** We received a relay truncated cell on circ.
 *
 * Since we don't ask for truncates currently, getting a truncated
 * means that a connection broke or an extend failed. For now,
 * just give up: for circ to close, and return 0.
 */
int
circuit_truncated(origin_circuit_t *circ, crypt_path_t *layer)
{
//  crypt_path_t *victim;
//  connection_t *stream;

  tor_assert(circ);
  tor_assert(layer);

  /* XXX Since we don't ask for truncates currently, getting a truncated
   *     means that a connection broke or an extend failed. For now,
   *     just give up.
   */
  circuit_mark_for_close(TO_CIRCUIT(circ),
          END_CIRC_REASON_FLAG_REMOTE|END_CIRC_REASON_OR_CONN_CLOSED);
  return 0;

#if 0
  while (layer->next != circ->cpath) {
    /* we need to clear out layer->next */
    victim = layer->next;
    log_debug(LD_CIRC, "Killing a layer of the cpath.");

    for (stream = circ->p_streams; stream; stream=stream->next_stream) {
      if (stream->cpath_layer == victim) {
        log_info(LD_APP, "Marking stream %d for close because of truncate.",
                 stream->stream_id);
        /* no need to send 'end' relay cells,
         * because the other side's already dead
         */
        connection_mark_unattached_ap(stream, END_STREAM_REASON_DESTROY);
      }
    }

    layer->next = victim->next;
    circuit_free_cpath_node(victim);
  }

  log_info(LD_CIRC, "finished");
  return 0;
#endif
}

/** Given a response payload and keys, initialize, then send a created
 * cell back.
 */
int
onionskin_answer(or_circuit_t *circ, uint8_t cell_type, const char *payload,
                 const char *keys)
{
  cell_t cell;
  crypt_path_t *tmp_cpath;

  tmp_cpath = tor_malloc_zero(sizeof(crypt_path_t));
  tmp_cpath->magic = CRYPT_PATH_MAGIC;

  memset(&cell, 0, sizeof(cell_t));
  cell.command = cell_type;
  cell.circ_id = circ->p_circ_id;

  circuit_set_state(TO_CIRCUIT(circ), CIRCUIT_STATE_OPEN);

  memcpy(cell.payload, payload,
         cell_type == CELL_CREATED ? ONIONSKIN_REPLY_LEN : DIGEST_LEN*2);

  log_debug(LD_CIRC,"init digest forward 0x%.8x, backward 0x%.8x.",
            (unsigned int)*(uint32_t*)(keys),
            (unsigned int)*(uint32_t*)(keys+20));
  if (circuit_init_cpath_crypto(tmp_cpath, keys, 0)<0) {
    log_warn(LD_BUG,"Circuit initialization failed");
    tor_free(tmp_cpath);
    return -1;
  }
  circ->n_digest = tmp_cpath->f_digest;
  circ->n_crypto = tmp_cpath->f_crypto;
  circ->p_digest = tmp_cpath->b_digest;
  circ->p_crypto = tmp_cpath->b_crypto;
  tmp_cpath->magic = 0;
  tor_free(tmp_cpath);

  if (cell_type == CELL_CREATED)
    memcpy(circ->handshake_digest, cell.payload+DH_KEY_LEN, DIGEST_LEN);
  else
    memcpy(circ->handshake_digest, cell.payload+DIGEST_LEN, DIGEST_LEN);

  circ->is_first_hop = (cell_type == CELL_CREATED_FAST);

  append_cell_to_circuit_queue(TO_CIRCUIT(circ),
                               circ->p_conn, &cell, CELL_DIRECTION_IN);
  log_debug(LD_CIRC,"Finished sending 'created' cell.");

  if (!is_local_IP(circ->p_conn->_base.addr) &&
      !connection_or_nonopen_was_started_here(circ->p_conn)) {
    /* record that we could process create cells from a non-local conn
     * that we didn't initiate; presumably this means that create cells
     * can reach us too. */
    router_orport_found_reachable();
  }

  return 0;
}

/** Choose a length for a circuit of purpose <b>purpose</b>.
 * Default length is 3 + the number of endpoints that would give something
 * away. If the routerlist <b>routers</b> doesn't have enough routers
 * to handle the desired path length, return as large a path length as
 * is feasible, except if it's less than 2, in which case return -1.
 */
static int
new_route_len(uint8_t purpose, extend_info_t *exit,
              smartlist_t *routers)
{
  int num_acceptable_routers;
  int routelen;

  tor_assert(routers);

  routelen = 3;
  if (exit &&
      purpose != CIRCUIT_PURPOSE_TESTING &&
      purpose != CIRCUIT_PURPOSE_S_ESTABLISH_INTRO)
    routelen++;

  log_debug(LD_CIRC,"Chosen route length %d (%d routers available).",
            routelen, smartlist_len(routers));

  num_acceptable_routers = count_acceptable_routers(routers);

  if (num_acceptable_routers < 2) {
    log_info(LD_CIRC,
             "Not enough acceptable routers (%d). Discarding this circuit.",
             num_acceptable_routers);
    return -1;
  }

  if (num_acceptable_routers < routelen) {
    log_info(LD_CIRC,"Not enough routers: cutting routelen from %d to %d.",
             routelen, num_acceptable_routers);
    routelen = num_acceptable_routers;
  }

  return routelen;
}

/** Fetch the list of predicted ports, dup it into a smartlist of
 * uint16_t's, remove the ones that are already handled by an
 * existing circuit, and return it.
 */
static smartlist_t *
circuit_get_unhandled_ports(time_t now)
{
  smartlist_t *source = rep_hist_get_predicted_ports(now);
  smartlist_t *dest = smartlist_create();
  uint16_t *tmp;
  int i;

  for (i = 0; i < smartlist_len(source); ++i) {
    tmp = tor_malloc(sizeof(uint16_t));
    memcpy(tmp, smartlist_get(source, i), sizeof(uint16_t));
    smartlist_add(dest, tmp);
  }

  circuit_remove_handled_ports(dest);
  return dest;
}

/** Return 1 if we already have circuits present or on the way for
 * all anticipated ports. Return 0 if we should make more.
 *
 * If we're returning 0, set need_uptime and need_capacity to
 * indicate any requirements that the unhandled ports have.
 */
int
circuit_all_predicted_ports_handled(time_t now, int *need_uptime,
                                    int *need_capacity)
{
  int i, enough;