rendservice.c

关于tor匿名通信的源代码

    service->desc = NULL;
  }
  d = service->desc = tor_malloc_zero(sizeof(rend_service_descriptor_t));
  d->pk = crypto_pk_dup_key(service->private_key);
  d->timestamp = time(NULL);
  d->version = service->descriptor_version;
  d->intro_nodes = smartlist_create();
  /* Whoever understands descriptor version 2 also understands intro
   * protocol 2. So we only support 2. */
  d->protocols = 1 << 2;

  for (i = 0; i < smartlist_len(service->intro_nodes); ++i) {
    rend_intro_point_t *intro_svc = smartlist_get(service->intro_nodes, i);
    rend_intro_point_t *intro_desc;
    circ = find_intro_circuit(intro_svc, service->pk_digest, d->version);
    if (!circ || circ->_base.purpose != CIRCUIT_PURPOSE_S_INTRO)
      continue;

    /* We have an entirely established intro circuit. */
    intro_desc = tor_malloc_zero(sizeof(rend_intro_point_t));
    intro_desc->extend_info = extend_info_dup(intro_svc->extend_info);
    if (intro_svc->intro_key)
      intro_desc->intro_key = crypto_pk_dup_key(intro_svc->intro_key);
    smartlist_add(d->intro_nodes, intro_desc);
  }
}

/** Load and/or generate private keys for all hidden services.  Return 0 on
 * success, -1 on failure.
 */
int
rend_service_load_keys(void)
{
  int i;
  rend_service_t *s;
  char fname[512];
  char buf[128];

  for (i=0; i < smartlist_len(rend_service_list); ++i) {
    s = smartlist_get(rend_service_list,i);
    if (s->private_key)
      continue;
    log_info(LD_REND, "Loading hidden-service keys from \"%s\"",
             s->directory);

    /* Check/create directory */
    if (check_private_dir(s->directory, CPD_CREATE) < 0)
      return -1;

    /* Load key */
    if (strlcpy(fname,s->directory,sizeof(fname)) >= sizeof(fname) ||
        strlcat(fname,PATH_SEPARATOR"private_key",sizeof(fname))
                                                  >= sizeof(fname)) {
      log_warn(LD_CONFIG, "Directory name too long to store key file: \"%s\".",
               s->directory);
      return -1;
    }
    s->private_key = init_key_from_file(fname, 1, LOG_ERR);
    if (!s->private_key)
      return -1;

    /* Create service file */
    if (rend_get_service_id(s->private_key, s->service_id)<0) {
      log_warn(LD_BUG, "Internal error: couldn't encode service ID.");
      return -1;
    }
    if (crypto_pk_get_digest(s->private_key, s->pk_digest)<0) {
      log_warn(LD_BUG, "Couldn't compute hash of public key.");
      return -1;
    }
    if (strlcpy(fname,s->directory,sizeof(fname)) >= sizeof(fname) ||
        strlcat(fname,PATH_SEPARATOR"hostname",sizeof(fname))
                                                  >= sizeof(fname)) {
      log_warn(LD_CONFIG, "Directory name too long to store hostname file:"
               " \"%s\".", s->directory);
      return -1;
    }
    tor_snprintf(buf, sizeof(buf),"%s.onion\n", s->service_id);
    if (write_str_to_file(fname,buf,0)<0)
      return -1;
  }
  return 0;
}

/** Return the service whose public key has a digest of <b>digest</b> and
 * which publishes the given descriptor <b>version</b>.  Return NULL if no
 * such service exists.
 */
static rend_service_t *
rend_service_get_by_pk_digest_and_version(const char* digest,
                                          uint8_t version)
{
  SMARTLIST_FOREACH(rend_service_list, rend_service_t*, s,
                    if (!memcmp(s->pk_digest,digest,DIGEST_LEN) &&
                        s->descriptor_version == version) return s);
  return NULL;
}

/** Return 1 if any virtual port in <b>service</b> wants a circuit
 * to have good uptime. Else return 0.
 */
static int
rend_service_requires_uptime(rend_service_t *service)
{
  int i;
  rend_service_port_config_t *p;

  for (i=0; i < smartlist_len(service->ports); ++i) {
    p = smartlist_get(service->ports, i);
    if (smartlist_string_num_isin(get_options()->LongLivedPorts,
                                  p->virtual_port))
      return 1;
  }
  return 0;
}

/******
 * Handle cells
 ******/

/** Respond to an INTRODUCE2 cell by launching a circuit to the chosen
 * rendezvous point.
 */
int
rend_service_introduce(origin_circuit_t *circuit, const char *request,
                       size_t request_len)
{
  char *ptr, *r_cookie;
  extend_info_t *extend_info = NULL;
  char buf[RELAY_PAYLOAD_SIZE];
  char keys[DIGEST_LEN+CPATH_KEY_MATERIAL_LEN]; /* Holds KH, Df, Db, Kf, Kb */
  rend_service_t *service;
  int r, i;
  size_t len, keylen;
  crypto_dh_env_t *dh = NULL;
  origin_circuit_t *launched = NULL;
  crypt_path_t *cpath = NULL;
  char serviceid[REND_SERVICE_ID_LEN_BASE32+1];
  char hexcookie[9];
  int circ_needs_uptime;
  int reason = END_CIRC_REASON_TORPROTOCOL;
  crypto_pk_env_t *intro_key;
  char intro_key_digest[DIGEST_LEN];

  base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
                circuit->rend_pk_digest, REND_SERVICE_ID_LEN);
  log_info(LD_REND, "Received INTRODUCE2 cell for service %s on circ %d.",
           escaped(serviceid), circuit->_base.n_circ_id);

  if (circuit->_base.purpose != CIRCUIT_PURPOSE_S_INTRO) {
    log_warn(LD_PROTOCOL,
             "Got an INTRODUCE2 over a non-introduction circuit %d.",
             circuit->_base.n_circ_id);
    return -1;
  }

  /* min key length plus digest length plus nickname length */
  if (request_len < DIGEST_LEN+REND_COOKIE_LEN+(MAX_NICKNAME_LEN+1)+
      DH_KEY_LEN+42) {
    log_warn(LD_PROTOCOL, "Got a truncated INTRODUCE2 cell on circ %d.",
             circuit->_base.n_circ_id);
    return -1;
  }

  /* look up service depending on circuit. */
  service = rend_service_get_by_pk_digest_and_version(
              circuit->rend_pk_digest, circuit->rend_desc_version);
  if (!service) {
    log_warn(LD_REND, "Got an INTRODUCE2 cell for an unrecognized service %s.",
             escaped(serviceid));
    return -1;
  }

  /* if descriptor version is 2, use intro key instead of service key. */
  if (circuit->rend_desc_version == 0) {
    intro_key = service->private_key;
  } else {
    intro_key = circuit->intro_key;
  }

  /* first DIGEST_LEN bytes of request is intro or service pk digest */
  crypto_pk_get_digest(intro_key, intro_key_digest);
  if (memcmp(intro_key_digest, request, DIGEST_LEN)) {
    base32_encode(serviceid, REND_SERVICE_ID_LEN_BASE32+1,
                  request, REND_SERVICE_ID_LEN);
    log_warn(LD_REND, "Got an INTRODUCE2 cell for the wrong service (%s).",
             escaped(serviceid));
    return -1;
  }

  keylen = crypto_pk_keysize(intro_key);
  if (request_len < keylen+DIGEST_LEN) {
    log_warn(LD_PROTOCOL,
             "PK-encrypted portion of INTRODUCE2 cell was truncated.");
    return -1;
  }
  /* Next N bytes is encrypted with service key */
  note_crypto_pk_op(REND_SERVER);
  r = crypto_pk_private_hybrid_decrypt(
       intro_key,buf,request+DIGEST_LEN,request_len-DIGEST_LEN,
       PK_PKCS1_OAEP_PADDING,1);
  if (r<0) {
    log_warn(LD_PROTOCOL, "Couldn't decrypt INTRODUCE2 cell.");
    return -1;
  }
  len = r;
  if (*buf == 2) {
    /* Version 2 INTRODUCE2 cell. */
    int klen;
    extend_info = tor_malloc_zero(sizeof(extend_info_t));
    extend_info->addr = ntohl(get_uint32(buf+1));
    extend_info->port = ntohs(get_uint16(buf+5));
    memcpy(extend_info->identity_digest, buf+7, DIGEST_LEN);
    extend_info->nickname[0] = '$';
    base16_encode(extend_info->nickname+1, sizeof(extend_info->nickname)-1,
                  extend_info->identity_digest, DIGEST_LEN);

    klen = ntohs(get_uint16(buf+7+DIGEST_LEN));
    if ((int)len != 7+DIGEST_LEN+2+klen+20+128) {
      log_warn(LD_PROTOCOL, "Bad length %u for version 2 INTRODUCE2 cell.",
               (int)len);
      reason = END_CIRC_REASON_TORPROTOCOL;
      goto err;
    }
    extend_info->onion_key = crypto_pk_asn1_decode(buf+7+DIGEST_LEN+2, klen);
    if (!extend_info->onion_key) {
      log_warn(LD_PROTOCOL,
               "Error decoding onion key in version 2 INTRODUCE2 cell.");
      reason = END_CIRC_REASON_TORPROTOCOL;
      goto err;
    }
    ptr = buf+7+DIGEST_LEN+2+klen;
    len -= 7+DIGEST_LEN+2+klen;
  } else {
    char *rp_nickname;
    size_t nickname_field_len;
    routerinfo_t *router;
    int version;
    if (*buf == 1) {
      rp_nickname = buf+1;
      nickname_field_len = MAX_HEX_NICKNAME_LEN+1;
      version = 1;
    } else {
      nickname_field_len = MAX_NICKNAME_LEN+1;
      rp_nickname = buf;
      version = 0;
    }
    ptr=memchr(rp_nickname,0,nickname_field_len);
    if (!ptr || ptr == rp_nickname) {
      log_warn(LD_PROTOCOL,
               "Couldn't find a nul-padded nickname in INTRODUCE2 cell.");
      return -1;
    }
    if ((version == 0 && !is_legal_nickname(rp_nickname)) ||
        (version == 1 && !is_legal_nickname_or_hexdigest(rp_nickname))) {
      log_warn(LD_PROTOCOL, "Bad nickname in INTRODUCE2 cell.");
      return -1;
    }
    /* Okay, now we know that a nickname is at the start of the buffer. */
    ptr = rp_nickname+nickname_field_len;
    len -= nickname_field_len;
    len -= rp_nickname - buf; /* also remove header space used by version, if
                               * any */
    router = router_get_by_nickname(rp_nickname, 0);
    if (!router) {
      log_info(LD_REND, "Couldn't find router %s named in introduce2 cell.",
               escaped_safe_str(rp_nickname));
      /* XXXX Add a no-such-router reason? */
      reason = END_CIRC_REASON_TORPROTOCOL;
      goto err;
    }

    extend_info = extend_info_from_router(router);
  }

  if (len != REND_COOKIE_LEN+DH_KEY_LEN) {
    log_warn(LD_PROTOCOL, "Bad length %u for INTRODUCE2 cell.", (int)len);
    reason = END_CIRC_REASON_TORPROTOCOL;
    goto err;
  }

  r_cookie = ptr;
  base16_encode(hexcookie,9,r_cookie,4);

  /* Try DH handshake... */
  dh = crypto_dh_new();
  if (!dh || crypto_dh_generate_public(dh)<0) {
    log_warn(LD_BUG,"Internal error: couldn't build DH state "
             "or generate public key.");
    reason = END_CIRC_REASON_INTERNAL;
    goto err;
  }
  if (crypto_dh_compute_secret(dh, ptr+REND_COOKIE_LEN, DH_KEY_LEN, keys,
                               DIGEST_LEN+CPATH_KEY_MATERIAL_LEN)<0) {
    log_warn(LD_BUG, "Internal error: couldn't complete DH handshake");
    reason = END_CIRC_REASON_INTERNAL;
    goto err;
  }

  circ_needs_uptime = rend_service_requires_uptime(service);

  /* help predict this next time */
  rep_hist_note_used_internal(time(NULL), circ_needs_uptime, 1);

  /* Launch a circuit to alice's chosen rendezvous point.
   */
  for (i=0;i<MAX_REND_FAILURES;i++) {
    int flags = CIRCLAUNCH_NEED_CAPACITY | CIRCLAUNCH_IS_INTERNAL;
    if (circ_needs_uptime) flags |= CIRCLAUNCH_NEED_UPTIME;
    launched = circuit_launch_by_extend_info(
                        CIRCUIT_PURPOSE_S_CONNECT_REND, extend_info, flags);

    if (launched)
      break;
  }
  if (!launched) { /* give up */
    log_warn(LD_REND, "Giving up launching first hop of circuit to rendezvous "
             "point %s for service %s.",
             escaped_safe_str(extend_info->nickname), serviceid);
    reason = END_CIRC_REASON_CONNECTFAILED;
    goto err;
  }
  log_info(LD_REND,
           "Accepted intro; launching circuit to %s "
           "(cookie %s) for service %s.",
           escaped_safe_str(extend_info->nickname), hexcookie, serviceid);
  tor_assert(launched->build_state);
  /* Fill in the circuit's state. */
  memcpy(launched->rend_pk_digest, circuit->rend_pk_digest,
         DIGEST_LEN);
  memcpy(launched->rend_cookie, r_cookie, REND_COOKIE_LEN);
  strlcpy(launched->rend_query, service->service_id,
          sizeof(launched->rend_query));
  launched->rend_desc_version = service->descriptor_version;
  launched->build_state->pending_final_cpath = cpath =
    tor_malloc_zero(sizeof(crypt_path_t));
  cpath->magic = CRYPT_PATH_MAGIC;
  launched->build_state->expiry_time = time(NULL) + MAX_REND_TIMEOUT;

  cpath->dh_handshake_state = dh;
  dh = NULL;
  if (circuit_init_cpath_crypto(cpath,keys+DIGEST_LEN,1)<0)
    goto err;
  memcpy(cpath->handshake_digest, keys, DIGEST_LEN);
  if (extend_info) extend_info_free(extend_info);

  return 0;
 err:
  if (dh) crypto_dh_free(dh);
  if (launched)
    circuit_mark_for_close(TO_CIRCUIT(launched), reason);
  if (extend_info) extend_info_free(extend_info);
  return -1;
}

/** Called when we fail building a rendezvous circuit at some point other
 * than the last hop: launches a new circuit to the same rendezvous point.
 */