commit 00fffbc1a15e2696a89c721d0c94dc333ff419ef Author: Robert Ransom <rransom.8774@gmail.com> Date: Tue Oct 25 00:24:15 2011 -0700 Don't give the Guard flag to relays without the CVE-2011-2768 fix --- changes/issue-2011-10-19L | 7 ++++ src/or/dirserv.c | 71 ++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 77 insertions(+), 1 deletions(-) diff --git a/changes/issue-2011-10-19L b/changes/issue-2011-10-19L index 1fefd72..b879c9d 100644 --- a/changes/issue-2011-10-19L +++ b/changes/issue-2011-10-19L @@ -19,3 +19,10 @@ client is connected to a patched relay. Bugfix on FIXME; found by frosty_un. + - Don't assign the Guard flag to relays running a version of Tor + which would use an OR connection on which it has received a + CREATE_FAST cell to satisfy an EXTEND request. Mitigates + CVE-2011-2768, by ensuring that clients will not connect + directly to any relay which an attacker could probe for an + unpatched client's connections. + diff --git a/src/or/dirserv.c b/src/or/dirserv.c index 6607901..fa7f693 100644 --- a/src/or/dirserv.c +++ b/src/or/dirserv.c @@ -2251,6 +2251,74 @@ get_possible_sybil_list(const smartlist_t *routers) return omit_as_sybil; } +/** Return non-zero iff a relay running the Tor version specified in + * <b>platform</b> is suitable for use as a potential entry guard. */ +static int +is_router_version_good_for_possible_guard(const char *platform) +{ + static int parsed_versions_initialized = 0; + static tor_version_t first_good_0_2_1_guard_version; + static tor_version_t first_good_0_2_2_guard_version; + static tor_version_t first_good_later_guard_version; + + tor_version_t router_version; + + /* XXX023 This block should be extracted into its own function. */ + /* XXXX Begin code copied from tor_version_as_new_as (in routerparse.c) */ + { + char *s, *s2, *start; + char tmp[128]; + + tor_assert(platform); + + if (strcmpstart(platform,"Tor ")) /* nonstandard Tor; be safe and say yes */ + return 1; + + start = (char *)eat_whitespace(platform+3); + if (!*start) return 0; + s = (char *)find_whitespace(start); /* also finds '\0', which is fine */ + s2 = (char*)eat_whitespace(s); + if (!strcmpstart(s2, "(r") || !strcmpstart(s2, "(git-")) + s = (char*)find_whitespace(s2); + + if ((size_t)(s-start+1) >= sizeof(tmp)) /* too big, no */ + return 0; + strlcpy(tmp, start, s-start+1); + + if (tor_version_parse(tmp, &router_version)<0) { + log_info(LD_DIR,"Router version '%s' unparseable.",tmp); + return 1; /* be safe and say yes */ + } + } + /* XXXX End code copied from tor_version_as_new_as (in routerparse.c) */ + + if (!parsed_versions_initialized) { + /* CVE-2011-2769 was fixed on the relay side in Tor versions + * 0.2.1.31, 0.2.2.34, and 0.2.3.6-alpha. */ + tor_assert(tor_version_parse("0.2.1.31", + &first_good_0_2_1_guard_version)>=0); + tor_assert(tor_version_parse("0.2.2.34", + &first_good_0_2_2_guard_version)>=0); + tor_assert(tor_version_parse("0.2.3.6-alpha", + &first_good_later_guard_version)>=0); + + /* Don't parse these constant version strings once for every relay + * for every vote. */ + parsed_versions_initialized = 1; + } + + return ((tor_version_same_series(&first_good_0_2_1_guard_version, + &router_version) && + tor_version_compare(&first_good_0_2_1_guard_version, + &router_version) <= 0) || + (tor_version_same_series(&first_good_0_2_2_guard_version, + &router_version) && + tor_version_compare(&first_good_0_2_2_guard_version, + &router_version) <= 0) || + (tor_version_compare(&first_good_later_guard_version, + &router_version) <= 0)); +} + /** Extract status information from <b>ri</b> and from other authority * functions and store it in <b>rs</b>>. If <b>naming</b>, consider setting * the named flag in <b>rs</b>. @@ -2294,7 +2362,8 @@ set_routerstatus_from_routerinfo(routerstatus_t *rs, (router_get_advertised_bandwidth(ri) >= BANDWIDTH_TO_GUARANTEE_GUARD || router_get_advertised_bandwidth(ri) >= MIN(guard_bandwidth_including_exits, - guard_bandwidth_excluding_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(