tor

rendmid.c (6852B)

---

/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2021, The Tor Project, Inc. */
/* See LICENSE for licensing information */

/**
* \file rendmid.c
* \brief Implement introductions points and rendezvous points.
**/

#include "core/or/or.h"
#include "core/or/channel.h"
#include "core/or/circuitlist.h"
#include "core/or/circuituse.h"
#include "app/config/config.h"
#include "lib/crypt_ops/crypto_cipher.h"
#include "core/or/dos.h"
#include "core/or/relay.h"
#include "feature/rend/rendmid.h"
#include "feature/hs/hs_circuitmap.h"
#include "feature/hs/hs_dos.h"
#include "feature/hs/hs_intropoint.h"
#include "feature/relay/relay_metrics.h"

#include "core/or/or_circuit_st.h"

/** 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) {
   relay_increment_est_rend_action(EST_REND_UNSUITABLE_CIRCUIT);
   log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
          "Tried to establish rendezvous on non-OR circuit with purpose %s",
          circuit_purpose_to_string(circ->base_.purpose));
   goto err;
 }

 /* Check if we are configured to defend ourselves from clients that
  * attempt to establish rendezvous points directly to us. */
 if (channel_is_client(circ->p_chan) &&
     dos_should_refuse_single_hop_client()) {
   relay_increment_est_rend_action(EST_REND_SINGLE_HOP);
   /* Note it down for the heartbeat log purposes. */
   dos_note_refuse_single_hop_client();
   /* Silent drop so the client has to time out before moving on. */
   return 0;
 }

 if (circ->base_.n_chan) {
   relay_increment_est_rend_action(EST_REND_UNSUITABLE_CIRCUIT);
   log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
            "Tried to establish rendezvous on non-edge circuit");
   goto err;
 }

 if (request_len != REND_COOKIE_LEN) {
   relay_increment_est_rend_action(EST_REND_MALFORMED);
   log_fn(LOG_PROTOCOL_WARN,
          LD_PROTOCOL, "Invalid length on ESTABLISH_RENDEZVOUS.");
   goto err;
 }

 if (hs_circuitmap_get_rend_circ_relay_side(request)) {
   relay_increment_est_rend_action(EST_REND_DUPLICATE_COOKIE);
   log_fn(LOG_PROTOCOL_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) {
   relay_increment_est_rend_action(EST_REND_CIRCUIT_DEAD);
   log_warn(LD_PROTOCOL, "Couldn't send RENDEZVOUS_ESTABLISHED cell.");
   /* Stop right now, the circuit has been closed. */
   return -1;
 }

 relay_increment_est_rend_action(EST_REND_SUCCESS);
 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) {
   relay_increment_rend1_action(REND1_UNSUITABLE_CIRCUIT);
   log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
          "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) {
   relay_increment_rend1_action(REND1_MALFORMED);
   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) {
   /* Once this was a LOG_PROTOCOL_WARN, but it can happen naturally if a
    * client gives up on a rendezvous circuit after sending INTRODUCE1, but
    * before the onion service sends the RENDEZVOUS1 cell.
    */
   relay_increment_rend1_action(REND1_UNKNOWN_COOKIE);
   log_fn(LOG_DEBUG, LD_PROTOCOL,
        "Rejecting RENDEZVOUS1 cell with unrecognized rendezvous cookie %s.",
        hexid);
   reason = END_CIRC_REASON_TORPROTOCOL;
   goto err;
 }

 /* Statistics: Mark circuits as RP circuits */
 if (options->HiddenServiceStatistics) {
   /* `circ` is the RP <-> service circuit */
   circ->circuit_carries_hs_traffic_stats = 1;
   /* `rend_circ` is the client <-> RP circuit */
   rend_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)) {
   relay_increment_rend1_action(REND1_CIRCUIT_DEAD);
   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;
 }

 relay_increment_rend1_action(REND1_SUCCESS);
 /* 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;
}