Bug#710657: gnutls: Negiotates an SSL v3.0 cipher when talkign to openssl using TLS 1.2

[Andreas Metzler]

On 2013-06-01 Kurt Roeckx <kurt at roeckx.be> wrote:
> Source: gnutls26
> Version: 2.12.20-6
> Severity: important
> Tags: security

> Hi,
> When using gnutls-cli to talk to apache with mod_ssl, I
> always get this when testing with SSL v3.0 to TLS v1.2:
> - Key Exchange: DHE-RSA
> - Cipher: AES-128-CBC
> - MAC: SHA1

> When talking to it with TLS 1.2, I really would like to see
> that it doesn't use SHA1.  From gnutls-cli --list, I would
> expect it to use one of the following:
> TLS_DHE_RSA_AES_128_CBC_SHA256                          0x00, 0x67 TLS1.2
> TLS_DHE_RSA_AES_256_CBC_SHA256                          0x00, 0x6b TLS1.2

> Openssl supports both of them.

> openssl also selects DHE-RSA-AES256-SHA256 when talking to itself
> when GCM is disabled, so I assume this is a gnutls problem.

Hello,

Parts of this have come up before:
* Discussion about using 128 by default instead of 256 is here:
  http://bugs.debian.org/476441

* Regarding SHA-1:
  Quoting Nikos Mavrogiannopoulos in <http://bugs.debian.org/665766>:
  "I'm not aware of weaknesses in SHA-1 when used with the HMAC
  construction."

cu Andreas
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