[tor-bugs] #7277 [Tor]: timestamp leaked in TLS client hello
Tor Bug Tracker & Wiki
blackhole at torproject.org
Fri Nov 23 14:49:32 UTC 2012
#7277: timestamp leaked in TLS client hello
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Reporter: proper | Owner:
Type: defect | Status: new
Priority: normal | Milestone: Tor: 0.2.4.x-final
Component: Tor | Version:
Keywords: tor-client | Parent:
Points: | Actualpoints:
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Comment(by asn):
Replying to [comment:1 nickm]:
> Interesting idea. Probably this would require an OpenSSL patch. The
impact here, if I understand right, would be that the guard (or anybody
else who can see the initial connection) can probabilistically track a
client with a skewed clock even as it changes IPs.
>
> Of course, the set of guards also makes that possible right now, as does
the NETINFO time, as other stuff probably does too.
>
True. Although, the whole set of guards of a client is not visible by a
single evil guard (in contrast with NETINFO or the TLS handshake).
Talking about NETINFO, is the `timestamp` on the `NETINFO` cell of clients
actually used anywhere? It seems like no:
{{{
if (labs(apparent_skew) > NETINFO_NOTICE_SKEW &&
router_get_by_id_digest(chan->conn->identity_digest)) {
}}}
I know that we like protocol properties to be symmetric on clients and
servers, but since we agree that timestamp leaking is potentially
dangerous, would it make sense to wipe the NETINFO `timestamp` in the case
of clients/bridges?
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7277#comment:2>
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