dirserv.c

关于tor匿名通信的源代码

{
  char *s=NULL;
  char digest[DIGEST_LEN];
  char published[ISO_TIME_LEN+1];
  size_t len;
  crypto_pk_env_t *private_key = get_identity_key();
  char *identity_pkey; /* Identity key, DER64-encoded. */
  size_t identity_pkey_len;

  if (crypto_pk_write_public_key_to_string(private_key,&identity_pkey,
                                           &identity_pkey_len)<0) {
    log_warn(LD_BUG,"write identity_pkey to string failed!");
    goto err;
  }
  format_iso_time(published, time(NULL));

  len = 2048;
  s = tor_malloc_zero(len);
  tor_snprintf(s, len,
               "network-status\n"
               "published %s\n"
               "router-status %s\n"
               "dir-signing-key\n%s"
               "directory-signature %s\n",
               published, "", identity_pkey,
               get_options()->Nickname);
  tor_free(identity_pkey);
  if (router_get_runningrouters_hash(s,digest)) {
    log_warn(LD_BUG,"couldn't compute digest");
    goto err;
  }
  note_crypto_pk_op(SIGN_DIR);
  if (router_append_dirobj_signature(s, len, digest, private_key)<0)
    goto err;

  set_cached_dir(&the_runningrouters, s, time(NULL));
  runningrouters_is_dirty = 0;

  return &the_runningrouters;
 err:
  tor_free(s);
  return NULL;
}

/** Set *<b>rr</b> to the most recently generated encoded signed
 * running-routers list, generating a new one as necessary.  Return the
 * size of the directory on success, and 0 on failure. */
cached_dir_t *
dirserv_get_runningrouters(void)
{
  return dirserv_pick_cached_dir_obj(
                         &cached_runningrouters, &the_runningrouters,
                         runningrouters_is_dirty,
                         generate_runningrouters,
                         "v1 network status list", V1_AUTHORITY);
}

cached_dir_t *
dirserv_get_consensus(void)
{
  return cached_v3_networkstatus;
}

/** For authoritative directories: the current (v2) network status. */
static cached_dir_t *the_v2_networkstatus = NULL;

/** Return true iff our opinion of the routers has been stale for long
 * enough that we should generate a new v2 network status doc. */
static int
should_generate_v2_networkstatus(void)
{
  return authdir_mode_v2(get_options()) &&
    the_v2_networkstatus_is_dirty &&
    the_v2_networkstatus_is_dirty + DIR_REGEN_SLACK_TIME < time(NULL);
}

/** If a router's uptime is at least this value, then it is always
 * considered stable, regardless of the rest of the network. This
 * way we resist attacks where an attacker doubles the size of the
 * network using allegedly high-uptime nodes, displacing all the
 * current guards. */
#define UPTIME_TO_GUARANTEE_STABLE (3600*24*30)
/** If a router's MTBF is at least this value, then it is always stable.
 * See above.  (Corresponds to about 7 days for current decay rates.) */
#define MTBF_TO_GUARANTEE_STABLE (60*60*24*5)
/** Similarly, we protect sufficiently fast nodes from being pushed
 * out of the set of Fast nodes. */
#define BANDWIDTH_TO_GUARANTEE_FAST (100*1024)
/** Similarly, every node with sufficient bandwidth can be considered
 * for Guard status. */
#define BANDWIDTH_TO_GUARANTEE_GUARD (250*1024)
/** Similarly, every node with at least this much weighted time known can be
 * considered familiar enough to be a guard.  Corresponds to about 20 days for
 * current decay rates.
 */
#define TIME_KNOWN_TO_GUARANTEE_FAMILIAR (8*24*60*60)
/** Similarly, every node with sufficient WFU is around enough to be a guard.
 */
#define WFU_TO_GUARANTEE_GUARD (0.995)

/* Thresholds for server performance: set by
 * dirserv_compute_performance_thresholds, and used by
 * generate_v2_networkstatus */
/* XXXX stick these all in a struct. */
static uint32_t stable_uptime = 0; /* start at a safe value */
static double stable_mtbf = 0.0;
static int enough_mtbf_info = 0;
static double guard_wfu = 0.0;
static long guard_tk = 0;
static uint32_t fast_bandwidth = 0;
static uint32_t guard_bandwidth_including_exits = 0;
static uint32_t guard_bandwidth_excluding_exits = 0;
static uint64_t total_bandwidth = 0;
static uint64_t total_exit_bandwidth = 0;

/** Helper: estimate the uptime of a router given its stated uptime and the
 * amount of time since it last stated its stated uptime. */
static INLINE long
real_uptime(routerinfo_t *router, time_t now)
{
  if (now < router->cache_info.published_on)
    return router->uptime;
  else
    return router->uptime + (now - router->cache_info.published_on);
}

/** Return 1 if <b>router</b> is not suitable for these parameters, else 0.
 * If <b>need_uptime</b> is non-zero, we require a minimum uptime.
 * If <b>need_capacity</b> is non-zero, we require a minimum advertised
 * bandwidth.
 */
static int
dirserv_thinks_router_is_unreliable(time_t now,
                                    routerinfo_t *router,
                                    int need_uptime, int need_capacity)
{
  if (need_uptime) {
    if (!enough_mtbf_info) {
      /* XXXX Once most authorities are on v3, we should change the rule from
       * "use uptime if we don't have mtbf data" to "don't advertise Stable on
       * v3 if we don't have enough mtbf data." */
      long uptime = real_uptime(router, now);
      if ((unsigned)uptime < stable_uptime &&
          (unsigned)uptime < UPTIME_TO_GUARANTEE_STABLE)
        return 1;
    } else {
      double mtbf =
        rep_hist_get_stability(router->cache_info.identity_digest, now);
      if (mtbf < stable_mtbf)
        return 1;
    }
  }
  if (need_capacity) {
    uint32_t bw = router_get_advertised_bandwidth(router);
    if (bw < fast_bandwidth)
      return 1;
  }
  return 0;
}

/** Return true iff <b>router</b> should be assigned the "HSDir" flag.
 * Right now this means it advertises support for it, it has a high
 * uptime, and it's currently considered Running.
 *
 * This function needs to be called after router-\>is_running has
 * been set.
 */
static int
dirserv_thinks_router_is_hs_dir(routerinfo_t *router, time_t now)
{
  long uptime = real_uptime(router, now);

  return (router->wants_to_be_hs_dir &&
          uptime > get_options()->MinUptimeHidServDirectoryV2 &&
          router->is_running);
}

/** Look through the routerlist, the Mean Time Between Failure history, and
 * the Weighted Fractional Uptime history, and use them to set thresholds for
 * the Stable, Fast, and Guard flags.  Update the fields stable_uptime,
 * stable_mtbf, enough_mtbf_info, guard_wfu, guard_tk, fast_bandwidth,
 * guard_bandwidh_including_exits, guard_bandwidth_excluding_exits,
 * total_bandwidth, and total_exit_bandwidth.
 *
 * Also, set the is_exit flag of each router appropriately. */
static void
dirserv_compute_performance_thresholds(routerlist_t *rl)
{
  int n_active, n_active_nonexit, n_familiar;
  uint32_t *uptimes, *bandwidths, *bandwidths_excluding_exits;
  long *tks;
  double *mtbfs, *wfus;
  time_t now = time(NULL);

  /* initialize these all here, in case there are no routers */
  stable_uptime = 0;
  stable_mtbf = 0;
  fast_bandwidth = 0;
  guard_bandwidth_including_exits = 0;
  guard_bandwidth_excluding_exits = 0;
  guard_tk = 0;
  guard_wfu = 0;
  total_bandwidth = 0;
  total_exit_bandwidth = 0;

  /* Initialize arrays that will hold values for each router.  We'll
   * sort them and use that to compute thresholds. */
  n_active = n_active_nonexit = 0;
  /* Uptime for every active router. */
  uptimes = tor_malloc(sizeof(uint32_t)*smartlist_len(rl->routers));
  /* Bandwidth for every active router. */
  bandwidths = tor_malloc(sizeof(uint32_t)*smartlist_len(rl->routers));
  /* Bandwidth for every active non-exit router. */
  bandwidths_excluding_exits =
    tor_malloc(sizeof(uint32_t)*smartlist_len(rl->routers));
  /* Weighted mean time between failure for each active router. */
  mtbfs = tor_malloc(sizeof(double)*smartlist_len(rl->routers));
  /* Time-known for each active router. */
  tks = tor_malloc(sizeof(long)*smartlist_len(rl->routers));
  /* Weighted fractional uptime for each active router. */
  wfus = tor_malloc(sizeof(double)*smartlist_len(rl->routers));

  /* Now, fill in the arrays. */
  SMARTLIST_FOREACH(rl->routers, routerinfo_t *, ri, {
    if (router_is_active(ri, now)) {
      const char *id = ri->cache_info.identity_digest;
      uint32_t bw;
      ri->is_exit = exit_policy_is_general_exit(ri->exit_policy);
      uptimes[n_active] = (uint32_t)real_uptime(ri, now);
      mtbfs[n_active] = rep_hist_get_stability(id, now);
      tks  [n_active] = rep_hist_get_weighted_time_known(id, now);
      bandwidths[n_active] = bw = router_get_advertised_bandwidth(ri);
      total_bandwidth += bw;
      if (ri->is_exit && !ri->is_bad_exit) {
        total_exit_bandwidth += bw;
      } else {
        bandwidths_excluding_exits[n_active_nonexit] = bw;
        ++n_active_nonexit;
      }
      ++n_active;
    }
  });

  /* Now, compute thresholds. */
  if (n_active) {
    /* The median uptime is stable. */
    stable_uptime = median_uint32(uptimes, n_active);
    /* The median mtbf is stable, if we have enough mtbf info */
    stable_mtbf = median_double(mtbfs, n_active);
    /* The 12.5th percentile bandwidth is fast. */
    fast_bandwidth = find_nth_uint32(bandwidths, n_active, n_active/8);
    /* (Now bandwidths is sorted.) */
    if (fast_bandwidth < ROUTER_REQUIRED_MIN_BANDWIDTH)
      fast_bandwidth = bandwidths[n_active/4];
    guard_bandwidth_including_exits = bandwidths[(n_active-1)/2];
    guard_tk = find_nth_long(tks, n_active, n_active/8);
  }

  if (guard_tk > TIME_KNOWN_TO_GUARANTEE_FAMILIAR)
    guard_tk = TIME_KNOWN_TO_GUARANTEE_FAMILIAR;

  if (fast_bandwidth > BANDWIDTH_TO_GUARANTEE_FAST)
    fast_bandwidth = BANDWIDTH_TO_GUARANTEE_FAST;

  /* Now that we have a time-known that 7/8 routers are known longer than,
   * fill wfus with the wfu of every such "familiar" router. */
  n_familiar = 0;
  SMARTLIST_FOREACH(rl->routers, routerinfo_t *, ri, {
      if (router_is_active(ri, now)) {
        const char *id = ri->cache_info.identity_digest;
        long tk = rep_hist_get_weighted_time_known(id, now);
        if (tk < guard_tk)
          continue;
        wfus[n_familiar++] = rep_hist_get_weighted_fractional_uptime(id, now);
      }
    });
  if (n_familiar)
    guard_wfu = median_double(wfus, n_familiar);
  if (guard_wfu > WFU_TO_GUARANTEE_GUARD)
    guard_wfu = WFU_TO_GUARANTEE_GUARD;

  enough_mtbf_info = rep_hist_have_measured_enough_stability();

  if (n_active_nonexit) {
    guard_bandwidth_excluding_exits =
      median_uint32(bandwidths_excluding_exits, n_active_nonexit);
  }

  log(LOG_INFO, LD_DIRSERV,
      "Cutoffs: For Stable, %lu sec uptime, %lu sec MTBF. "
      "For Fast: %lu bytes/sec. "
      "For Guard: WFU %.03lf%%, time-known %lu sec, "
      "and bandwidth %lu or %lu bytes/sec.",
      (unsigned long)stable_uptime,
      (unsigned long)stable_mtbf,
      (unsigned long)fast_bandwidth,
      guard_wfu*100,
      (unsigned long)guard_tk,
      (unsigned long)guard_bandwidth_including_exits,
      (unsigned long)guard_bandwidth_excluding_exits);

  tor_free(uptimes);
  tor_free(mtbfs);
  tor_free(bandwidths);
  tor_free(bandwidths_excluding_exits);
  tor_free(tks);
  tor_free(wfus);
}

/** Given a platform string as in a routerinfo_t (possibly null), return a
 * newly allocated version string for a networkstatus document, or NULL if the
 * platform doesn't give a Tor version. */
static char *
version_from_platform(const char *platform)
{
  if (platform && !strcmpstart(platform, "Tor ")) {
    const char *eos = find_whitespace(platform+4);
    if (eos && !strcmpstart(eos, " (r")) {
      /* XXXX021 Unify this logic with the other version extraction
       * logic */
      eos = find_whitespace(eos+1);
    }
    if (eos) {
      return tor_strndup(platform, eos-platform);
    }
  }
  return NULL;
}

/** Helper: write the router-status information in <b>rs</b> into <b>buf</b>,
 * which has at least <b>buf_len</b> free characters.  Do NUL-termination.
 * Use the same format as in network-status documents.  If <b>version</b> is
 * non-NULL, add a "v" line for the platform.  Return 0 on success, -1 on
 * failure.  If <b>first_line_only<b> is true, don't include any flags
 * or version line.
 */
int
routerstatus_format_entry(char *buf, size_t buf_len,
                          routerstatus_t *rs, const char *version,
                          int first_line_only)
{
  int r;
  struct in_addr in;
  char *cp;

  char published[ISO_TIME_LEN+1];
  char ipaddr[INET_NTOA_BUF_LEN];
  char identity64[BASE64_DIGEST_LEN+1];
  char digest64[BASE64_DIGEST_LEN+1];

  format_iso_time(published, rs->published_on);
  digest_to_base64(identity64, rs->identity_digest);
  digest_to_base64(digest64, rs->descriptor_digest);
  in.s_addr = htonl(rs->addr);
  tor_inet_ntoa(&in, ipaddr, sizeof(ipaddr));

  r = tor_snprintf(buf, buf_len,
                   "r %s %s %s %s %s %d %d\n",
                   rs->nickname,
                   identity64,
                   digest64,
                   published,
                   ipaddr,
                   (int)rs->or_port,
                   (int)rs->dir_port);
  if (r<0) {
    log_warn(LD_BUG, "Not enough space in buffer.");
    return -1;
  }
  if (first_line_only)
    return 0;
  cp = buf + strlen(buf);
  /* NOTE: Whenever this list expands, be sure to increase MAX_FLAG_LINE_LEN*/
  r = tor_snprintf(cp, buf_len - (cp-buf),
                   "s%s%s%s%s%s%s%s%s%s%s%s%s%s\n",
                  /* These must stay in al