Bug#623001: libgnutls26: fails to handshake on a number of sites (firefox works)

Nikos Mavrogiannopoulos nmav at gnutls.org
Sun Apr 17 10:06:20 CEST 2011

On 04/17/2011 09:45 AM, Simon Josefsson wrote:

>>> thank you for taking the time to test the packages in experimental. I
>>> can reproduce the bug.
>>> For clarification it is not caused by libgcrypt11 from experimental,
>>> libgnutls26 2.12.2-1 with stable libgcrypt11 also fails.  Attached
>>> verbose log is not a lot more enlightening.
>> d3nwyuy0nl342s.cloudfront.net seems to support only one ciphersuite.
>> That is ARCFOUR-128 with HMAC-MD5. I disabled HMAC-MD5 from the default
>> set in 2.12.0 because it is not really trusted as an HMAC any more.
>> If however this is widespread issue I'll reinstate HMAC-MD5 and
>> remove it when a real attack is known.
> I thought there weren't any attacks on HMAC-MD5, have I missed anything?

That's what I say above. No real attacks exist although its security
is questioned (ECRYPT II report on algorithms and key sizes). The text
mentions: "The recent advances in the cryptanalysis of MD5 (see Section
10.3), and specifically HMAC-MD5 (e.g. [58, 143, 213, 83, 256]), suggest
that implementers should move away from HMAC-MD5 as soon as possible."


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