commit a83650852d3cd00c9916cae74d755ae55a6b506d Author: Nick Mathewson nickm@torproject.org Date: Wed Feb 14 10:45:57 2018 -0500

Add another NULL-pointer fix for protover.c.

This one can only be exploited if you can generate a correctly signed consensus, so it's not as bad as 25074.

Fixes bug 25251; also tracked as TROVE-2018-004. --- changes/trove-2018-004 | 8 ++++++++ src/or/protover.c | 5 +++++ 2 files changed, 13 insertions(+)

diff --git a/changes/trove-2018-004 b/changes/trove-2018-004 new file mode 100644 index 000000000..37e0a89b0 --- /dev/null +++ b/changes/trove-2018-004 @@ -0,0 +1,8 @@ + o Minor bugfixes (denial-of-service): + - Fix a possible crash on malformed consensus. If a consensus had + contained an unparseable protocol line, it could have made clients + and relays crash with a null-pointer exception. To exploit this + issue, however, an attacker would need to be able to subvert the + directory-authority system. Fixes bug 25251; bugfix on + 0.2.9.4-alpha. Also tracked as TROVE-2018-004. + diff --git a/src/or/protover.c b/src/or/protover.c index a75077462..e63036f78 100644 --- a/src/or/protover.c +++ b/src/or/protover.c @@ -624,6 +624,11 @@ protover_all_supported(const char *s, char **missing_out) }

smartlist_t *entries = parse_protocol_list(s); + if (BUG(entries == NULL)) { + log_warn(LD_NET, "Received an unparseable protocol list %s" + " from the consensus", escaped(s)); + return 1; + }

missing = smartlist_new();