Commit message: Add option to give guard flag to relays without the CVE-2011-2768 fix

This way, all of the DA operators can upgrade immediately, without nuking
every client's set of entry guards as soon as a majority of them upgrade.

Until enough guards have upgraded, a majority of dirauths should set this
config option so that there are still enough guards in the network. After
a few days pass, all dirauths should use the default.
CVE: CVE-2011-2768
CWE: CWE-264
Vulnerability description: Tor before 0.2.2.34, when configured as a client or bridge, sends a TLS certificate chain as part of an outgoing OR connection, which allows remote relays to bypass intended anonymity properties by reading this chain and then determining the set of entry guards that the client or bridge had selected.

Project: tor
File: dirserv.c

set_routerstatus_from_routerinfo(routerstatus_t *rs,
                                 routerinfo_t *ri, time_t now,
                                 int naming, int listbadexits,
                                 int listbaddirs, int vote_on_hsdirs)
{
  int unstable_version =
    !tor_version_as_new_as(ri->platform,"0.1.1.16-rc-cvs");
  memset(rs, 0, sizeof(routerstatus_t));

  rs->is_authority =
    router_digest_is_trusted_dir(ri->cache_info.identity_digest);

  /* Already set by compute_performance_thresholds. */
  rs->is_exit = ri->is_exit;
  rs->is_stable = ri->is_stable =
    router_is_active(ri, now) &&
    !dirserv_thinks_router_is_unreliable(now, ri, 1, 0) &&
    !unstable_version;
  rs->is_fast = ri->is_fast =
    router_is_active(ri, now) &&
    !dirserv_thinks_router_is_unreliable(now, ri, 0, 1);
  rs->is_running = ri->is_running; /* computed above */

  if (naming) {
    uint32_t name_status = dirserv_get_name_status(
                         ri->cache_info.identity_digest, ri->nickname);
    rs->is_named = (naming && (name_status & FP_NAMED)) ? 1 : 0;
    rs->is_unnamed = (naming && (name_status & FP_UNNAMED)) ? 1 : 0;
  }
  rs->is_valid = ri->is_valid;

  if (rs->is_fast &&
      (router_get_advertised_bandwidth(ri) >= BANDWIDTH_TO_GUARANTEE_GUARD ||
       router_get_advertised_bandwidth(ri) >=
                              MIN(guard_bandwidth_including_exits,
                                  guard_bandwidth_excluding_exits)) &&
      is_router_version_good_for_possible_guard(ri->platform)) {
    long tk = rep_hist_get_weighted_time_known(
                                      ri->cache_info.identity_digest, now);
    double wfu = rep_hist_get_weighted_fractional_uptime(
                                      ri->cache_info.identity_digest, now);
    rs->is_possible_guard = (wfu >= guard_wfu && tk >= guard_tk) ? 1 : 0;
  } else {
    rs->is_possible_guard = 0;
  }
  rs->is_bad_directory = listbaddirs && ri->is_bad_directory;
  rs->is_bad_exit = listbadexits && ri->is_bad_exit;
  ri->is_hs_dir = dirserv_thinks_router_is_hs_dir(ri, now);
  rs->is_hs_dir = vote_on_hsdirs && ri->is_hs_dir;
  rs->is_v2_dir = ri->dir_port != 0;

  if (!strcasecmp(ri->nickname, UNNAMED_ROUTER_NICKNAME))
    rs->is_named = rs->is_unnamed = 0;

  rs->published_on = ri->cache_info.published_on;
  memcpy(rs->identity_digest, ri->cache_info.identity_digest, DIGEST_LEN);
  memcpy(rs->descriptor_digest, ri->cache_info.signed_descriptor_digest,
         DIGEST_LEN);
  rs->addr = ri->addr;
  strlcpy(rs->nickname, ri->nickname, sizeof(rs->nickname));
  rs->or_port = ri->or_port;
  rs->dir_port = ri->dir_port;
}