[Operators] SSLv3 is out.

Thijs Alkemade thijs at xnyhps.nl
Wed Oct 15 09:16:01 UTC 2014


On 15 okt. 2014, at 10:57, Matthew Wild <mwild1 at gmail.com> wrote:

> On 15 October 2014 08:47, Jonas Wielicki <xmpp-operators at sotecware.net> wrote:
> I’m not confident that this attack is (like BEAST and CRIME) relevant
> for XMPP.
> 
> It requires that the attacker is able to induce several SSL connections,
> with the offset of the data to be attacked (which must be the same for
> all attempts) and the size of the packet under the attackers precise
> control.
> 
> I can only think this would apply to s2s connections, if you had an account on the server. As an active attacker you could break an s2s connection and send a new stanza to re-establish. The stanza is under your control. Whether this constitutes "precise control" I don't know.
>  
> I don’t know of a scenario in XMPP C2S, nor can I imagine one for XMPP
> S2S, where this would be plausibly possible. So I think it is not
> relevant for XMPP (also, the usual opportunistic encryption argument for
> s2s applies).
> 
> Also, do XMPP S2S connections the “downgrade dance” mentioned in the paper?
> 
> I know of no XMPP implementations that do this. So basically it would work only if SSLv3 is the only protocol supported by one of the parties (I don't think I've seen any servers that only support SSLv3).

There are about 199 SSLv3 only servers seen by xmpp.net:

https://xmpp.net/reports.php#sslv3butnottls1

(though many test results on that list are more than a couple of weeks old,
and I wouldn’t trust those too much)

IIRC, the last time this was brought up someone mentioned that tkabber only
recently started supporting TLS 1.0. That's the only client I can think of
that only supported SSLv3. http://tkabber.jabber.ru/tkabber-1.0 mentions
"Disabled SSLv2 and enabled TLSv1 TLS options"... that’s from january 1st this
year.

Regards,
Thijs

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