rendclient.c

关于tor匿名通信的源代码

/* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
 * Copyright (c) 2007-2008, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/* $Id$ */
const char rendclient_c_id[] =
  "$Id$";

/**
 * \file rendclient.c
 * \brief Client code to access location-hidden services.
 **/

#include "or.h"

/** Called when we've established a circuit to an introduction point:
 * send the introduction request. */
void
rend_client_introcirc_has_opened(origin_circuit_t *circ)
{
  tor_assert(circ->_base.purpose == CIRCUIT_PURPOSE_C_INTRODUCING);
  tor_assert(circ->cpath);

  log_info(LD_REND,"introcirc is open");
  connection_ap_attach_pending();
}

/** Send the establish-rendezvous cell along a rendezvous circuit. if
 * it fails, mark the circ for close and return -1. else return 0.
 */
static int
rend_client_send_establish_rendezvous(origin_circuit_t *circ)
{
  tor_assert(circ->_base.purpose == CIRCUIT_PURPOSE_C_ESTABLISH_REND);
  log_info(LD_REND, "Sending an ESTABLISH_RENDEZVOUS cell");

  if (crypto_rand(circ->rend_cookie, REND_COOKIE_LEN) < 0) {
    log_warn(LD_BUG, "Internal error: Couldn't produce random cookie.");
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
    return -1;
  }
  if (relay_send_command_from_edge(0, TO_CIRCUIT(circ),
                                   RELAY_COMMAND_ESTABLISH_RENDEZVOUS,
                                   circ->rend_cookie, REND_COOKIE_LEN,
                                   circ->cpath->prev)<0) {
    /* circ is already marked for close */
    log_warn(LD_GENERAL, "Couldn't send ESTABLISH_RENDEZVOUS cell");
    return -1;
  }

  return 0;
}

/** Called when we're trying to connect an ap conn; sends an INTRODUCE1 cell
 * down introcirc if possible.
 */
int
rend_client_send_introduction(origin_circuit_t *introcirc,
                              origin_circuit_t *rendcirc)
{
  size_t payload_len;
  int r;
  char payload[RELAY_PAYLOAD_SIZE];
  char tmp[RELAY_PAYLOAD_SIZE];
  rend_cache_entry_t *entry;
  crypt_path_t *cpath;
  off_t dh_offset;
  crypto_pk_env_t *intro_key; /* either Bob's public key or an intro key. */

  tor_assert(introcirc->_base.purpose == CIRCUIT_PURPOSE_C_INTRODUCING);
  tor_assert(rendcirc->_base.purpose == CIRCUIT_PURPOSE_C_REND_READY);
  tor_assert(!rend_cmp_service_ids(introcirc->rend_query,
                                   rendcirc->rend_query));

  if (rend_cache_lookup_entry(introcirc->rend_query, -1, &entry) < 1) {
    log_warn(LD_REND,
             "query %s didn't have valid rend desc in cache. Failing.",
             escaped_safe_str(introcirc->rend_query));
    goto err;
  }

  /* first 20 bytes of payload are the hash of bob's pk */
  if (entry->parsed->version == 0) { /* unversioned descriptor */
    intro_key = entry->parsed->pk;
  } else { /* versioned descriptor */
    intro_key = NULL;
    SMARTLIST_FOREACH(entry->parsed->intro_nodes, rend_intro_point_t *,
                      intro, {
      if (!memcmp(introcirc->build_state->chosen_exit->identity_digest,
                  intro->extend_info->identity_digest, DIGEST_LEN)) {
        intro_key = intro->intro_key;
        break;
      }
    });
    if (!intro_key) {
      log_warn(LD_BUG, "Internal error: could not find intro key.");
      goto err;
    }
  }
  if (crypto_pk_get_digest(intro_key, payload)<0) {
    log_warn(LD_BUG, "Internal error: couldn't hash public key.");
    goto err;
  }

  /* Initialize the pending_final_cpath and start the DH handshake. */
  cpath = rendcirc->build_state->pending_final_cpath;
  if (!cpath) {
    cpath = rendcirc->build_state->pending_final_cpath =
      tor_malloc_zero(sizeof(crypt_path_t));
    cpath->magic = CRYPT_PATH_MAGIC;
    if (!(cpath->dh_handshake_state = crypto_dh_new())) {
      log_warn(LD_BUG, "Internal error: couldn't allocate DH.");
      goto err;
    }
    if (crypto_dh_generate_public(cpath->dh_handshake_state)<0) {
      log_warn(LD_BUG, "Internal error: couldn't generate g^x.");
      goto err;
    }
  }

  /* write the remaining items into tmp */
  if (entry->parsed->protocols & (1<<2)) {
    /* version 2 format */
    extend_info_t *extend_info = rendcirc->build_state->chosen_exit;
    int klen;
    tmp[0] = 2; /* version 2 of the cell format */
    /* nul pads */
    set_uint32(tmp+1, htonl(extend_info->addr));
    set_uint16(tmp+5, htons(extend_info->port));
    memcpy(tmp+7, extend_info->identity_digest, DIGEST_LEN);
    klen = crypto_pk_asn1_encode(extend_info->onion_key, tmp+7+DIGEST_LEN+2,
                                 sizeof(tmp)-(7+DIGEST_LEN+2));
    set_uint16(tmp+7+DIGEST_LEN, htons(klen));
    memcpy(tmp+7+DIGEST_LEN+2+klen, rendcirc->rend_cookie,
           REND_COOKIE_LEN);
    dh_offset = 7+DIGEST_LEN+2+klen+REND_COOKIE_LEN;
  } else {
    /* Version 0. */
    strncpy(tmp, rendcirc->build_state->chosen_exit->nickname,
            (MAX_NICKNAME_LEN+1)); /* nul pads */
    memcpy(tmp+MAX_NICKNAME_LEN+1, rendcirc->rend_cookie,
           REND_COOKIE_LEN);
    dh_offset = MAX_NICKNAME_LEN+1+REND_COOKIE_LEN;
  }

  if (crypto_dh_get_public(cpath->dh_handshake_state, tmp+dh_offset,
                           DH_KEY_LEN)<0) {
    log_warn(LD_BUG, "Internal error: couldn't extract g^x.");
    goto err;
  }

  note_crypto_pk_op(REND_CLIENT);
  /*XXX maybe give crypto_pk_public_hybrid_encrypt a max_len arg,
   * to avoid buffer overflows? */
  r = crypto_pk_public_hybrid_encrypt(intro_key, payload+DIGEST_LEN,
                                      tmp,
                                      (int)(dh_offset+DH_KEY_LEN),
                                      PK_PKCS1_OAEP_PADDING, 0);
  if (r<0) {
    log_warn(LD_BUG,"Internal error: hybrid pk encrypt failed.");
    goto err;
  }

  payload_len = DIGEST_LEN + r;
  tor_assert(payload_len <= RELAY_PAYLOAD_SIZE); /* we overran something */

  log_info(LD_REND, "Sending an INTRODUCE1 cell");
  if (relay_send_command_from_edge(0, TO_CIRCUIT(introcirc),
                                   RELAY_COMMAND_INTRODUCE1,
                                   payload, payload_len,
                                   introcirc->cpath->prev)<0) {
    /* introcirc is already marked for close. leave rendcirc alone. */
    log_warn(LD_BUG, "Couldn't send INTRODUCE1 cell");
    return -1;
  }

  /* Now, we wait for an ACK or NAK on this circuit. */
  introcirc->_base.purpose = CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT;

  return 0;
err:
  circuit_mark_for_close(TO_CIRCUIT(introcirc), END_CIRC_REASON_INTERNAL);
  circuit_mark_for_close(TO_CIRCUIT(rendcirc), END_CIRC_REASON_INTERNAL);
  return -1;
}

/** Called when a rendezvous circuit is open; sends a establish
 * rendezvous circuit as appropriate. */
void
rend_client_rendcirc_has_opened(origin_circuit_t *circ)
{
  tor_assert(circ->_base.purpose == CIRCUIT_PURPOSE_C_ESTABLISH_REND);

  log_info(LD_REND,"rendcirc is open");

  /* generate a rendezvous cookie, store it in circ */
  if (rend_client_send_establish_rendezvous(circ) < 0) {
    return;
  }
}

/** Called when get an ACK or a NAK for a REND_INTRODUCE1 cell.
 */
int
rend_client_introduction_acked(origin_circuit_t *circ,
                               const char *request, size_t request_len)
{
  origin_circuit_t *rendcirc;
  (void) request; // XXXX Use this.

  if (circ->_base.purpose != CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT) {
    log_warn(LD_PROTOCOL,
             "Received REND_INTRODUCE_ACK on unexpected circuit %d.",
             circ->_base.n_circ_id);
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_TORPROTOCOL);
    return -1;
  }

  tor_assert(circ->build_state->chosen_exit);

  if (request_len == 0) {
    /* It's an ACK; the introduction point relayed our introduction request. */
    /* Locate the rend circ which is waiting to hear about this ack,
     * and tell it.
     */
    log_info(LD_REND,"Received ack. Telling rend circ...");
    rendcirc = circuit_get_by_rend_query_and_purpose(
               circ->rend_query, CIRCUIT_PURPOSE_C_REND_READY);
    if (rendcirc) { /* remember the ack */
      rendcirc->_base.purpose = CIRCUIT_PURPOSE_C_REND_READY_INTRO_ACKED;
    } else {
      log_info(LD_REND,"...Found no rend circ. Dropping on the floor.");
    }
    /* close the circuit: we won't need it anymore. */
    circ->_base.purpose = CIRCUIT_PURPOSE_C_INTRODUCE_ACKED;
    circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_FINISHED);
  } else {
    /* It's a NAK; the introduction point didn't relay our request. */
    circ->_base.purpose = CIRCUIT_PURPOSE_C_INTRODUCING;
    /* Remove this intro point from the set of viable introduction
     * points. If any remain, extend to a new one and try again.
     * If none remain, refetch the service descriptor.
     */
    if (rend_client_remove_intro_point(circ->build_state->chosen_exit,
                                       circ->rend_query) > 0) {
      /* There are introduction points left. Re-extend the circuit to
       * another intro point and try again. */
      extend_info_t *extend_info;
      int result;
      extend_info = rend_client_get_random_intro(circ->rend_query);
      if (!extend_info) {
        log_warn(LD_REND, "No introduction points left for %s. Closing.",
                 escaped_safe_str(circ->rend_query));
        circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_INTERNAL);
        return -1;
      }
      log_info(LD_REND,
               "Got nack for %s from %s. Re-extending circ %d, "
               "this time to %s.",
               escaped_safe_str(circ->rend_query),
               circ->build_state->chosen_exit->nickname, circ->_base.n_circ_id,
               extend_info->nickname);
      result = circuit_extend_to_new_exit(circ, extend_info);
      extend_info_free(extend_info);
      return result;
    }
  }
  return 0;
}

/** The period for which a hidden service directory cannot be queried for
 * the same descriptor ID again. */
#define REND_HID_SERV_DIR_REQUERY_PERIOD (15 * 60)

/** Contains the last request times to hidden service directories for
 * certain queries; keys are strings consisting of base32-encoded
 * hidden service directory identities and base32-encoded descriptor IDs;
 * values are pointers to timestamps of the last requests. */
static strmap_t *last_hid_serv_requests = NULL;

/** Look up the last request time to hidden service directory <b>hs_dir</b>
 * for descriptor ID <b>desc_id_base32</b>. If <b>set</b> is non-zero,
 * assign the current time <b>now</b> and return that. Otherwise, return
 * the most recent request time, or 0 if no such request has been sent
 * before. */
static time_t
lookup_last_hid_serv_request(routerstatus_t *hs_dir,
                             const char *desc_id_base32, time_t now, int set)
{
  char hsdir_id_base32[REND_DESC_ID_V2_LEN_BASE32 + 1];
  char hsdir_desc_comb_id[2 * REND_DESC_ID_V2_LEN_BASE32 + 1];
  time_t *last_request_ptr;
  base32_encode(hsdir_id_base32, sizeof(hsdir_id_base32),
                hs_dir->identity_digest, DIGEST_LEN);
  tor_snprintf(hsdir_desc_comb_id, sizeof(hsdir_desc_comb_id), "%s%s",
               hsdir_id_base32, desc_id_base32);
  if (set) {
    last_request_ptr = tor_malloc_zero(sizeof(time_t *));
    *last_request_ptr = now;
    strmap_set(last_hid_serv_requests, hsdir_desc_comb_id, last_request_ptr);
  } else
    last_request_ptr = strmap_get_lc(last_hid_serv_requests,
                                     hsdir_desc_comb_id);
  return (last_request_ptr) ? *last_request_ptr : 0;
}

/** Clean the history of request times to hidden service directories, so that
 * it does not contain requests older than REND_HID_SERV_DIR_REQUERY_PERIOD
 * seconds any more. */
static void
directory_clean_last_hid_serv_requests(void)
{
  strmap_iter_t *iter;
  time_t cutoff = time(NULL) - REND_HID_SERV_DIR_REQUERY_PERIOD;
  if (!last_hid_serv_requests)
    last_hid_serv_requests = strmap_new();
  for (iter = strmap_iter_init(last_hid_serv_requests);
       !strmap_iter_done(iter); ) {
    const char *key;
    void *val;
    time_t *ent;
    strmap_iter_get(iter, &key, &val);
    ent = (time_t *) val;
    if (*ent < cutoff) {
      iter = strmap_iter_next_rmv(last_hid_serv_requests, iter);
      tor_free(ent);
    } else {
      iter = strmap_iter_next(last_hid_serv_requests, iter);
    }
  }
}

/** Determine the responsible hidden service directories for <b>desc_id</b>
 * and fetch the descriptor belonging to that ID from one of them. Only
 * send a request to hidden service directories that we did not try within
 * the last REND_HID_SERV_DIR_REQUERY_PERIOD seconds; on success, return 1,
 * in the case that no hidden service directory is left to ask for the
 * descriptor, return 0, and in case of a failure -1. <b>query</b> is only
 * passed for pretty log statements. */
static int
directory_get_from_hs_dir(const char *desc_id, const char *query)
{
  smartlist_t *responsible_dirs = smartlist_create();
  routerstatus_t *hs_dir;
  char desc_id_base32[REND_DESC_ID_V2_LEN_BASE32 + 1];
  time_t now = time(NULL);
  tor_assert(desc_id);
  tor_assert(query);
  tor_assert(strlen(query) == REND_SERVICE_ID_LEN_BASE32);
  /* Determine responsible dirs. Even if we can't get all we want,
   * work with the ones we have. If it's empty, we'll notice below. */
  (int) hid_serv_get_responsible_directories(responsible_dirs, desc_id);

  base32_encode(desc_id_base32, sizeof(desc_id_base32),