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Date: Wed, 29 Apr 2015 22:46:13 +1200
From: Amos Jeffries <squid3@...enet.co.nz>
To: oss-security@...ts.openwall.com
Subject: CVE policy clarification request

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Hi,
 I have had a potential security issue reported with Squid proxy. But
have been questioned about deciding not to seek a CVE.


The situation is that Squid has a TLS/SSL MITM mode "client-first"
whereby a blatantly fake server certificate is sent to the client. If
the client accepts this certificate the proxy happily does whatever it
wants with the HTTPS traffic. Which may (or not) involve TLS to some
backend server.
 NP: we have this documented with danger warnings, caveat admin, its
operating as designed despite the nastiness, and its already now a
deprecated feature.


Now we have a report that the server cert validation was a bit naive,
in a way which I would go straight to CVE request had it been occuring
in normal proxying of https:// URLs.

However the bug found is only exploitable in this case when the
client-first MITM has already exploited the client security fail.


My observation of Mitre allocations has been that when a bug B is only
acting because of another A exploited first the CVE gets assigned to
the A. In this case the client willingness to accept fake certificate
makes it vulnerable to mistakes in the proxy.

Is my observation correct or does the server validation bug get a CVE
assignment anyway?

And if so, should I seek CVE for other issues also hiding behind that
client-first nasty?


PS. for those wanting to jump on the bug, it's present in all Squid
3.2 and later. The workaround so far is to upgrade to 3.3 or later
*and* configure server-first bumping mode instead of client-first (or
ensure a peek is done before bumping in 3.5+). More details can follow
once we have confirmed the patch fix.

AYJ
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