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[TLS] AES and SSLv3 (was Re: Unfortunate current practices for HTTP over TLS)

Michael D'Errico <mike-list@pobox.com> Wed, 19 January 2011 00:31 UTC

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Date: Tue, 18 Jan 2011 16:34:32 -0800
From: Michael D'Errico <mike-list@pobox.com>
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References: <AANLkTikX_9F9z0n1wfeAGX0W5ZcSupeK9v2UGO9D9KPp@mail.gmail.com> <4D362A1E.9020509@pobox.com> <op.vpi4dsxqqrq7tp@acorna.oslo.osa>
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Subject: [TLS] AES and SSLv3 (was Re: Unfortunate current practices for HTTP over TLS)
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The SHA-256 cipher suites aren't compatible with SSLv3 since the SSLv3
spec only shows what to do with MD5 and SHA-1.  But there is nothing
about AES which is incompatible with SSLv3, and indeed my server is able
to negotiate non-SHA-256 AES_CBC cipher suites with SSLv3 clients that
offer them.

So my question is now:

     If a client offers AES cipher suites in a ClientHello with a
     version of 0300, why is it wrong to choose one of them?

Mike



Yngve N. Pettersen (Developer Opera Software ASA) wrote:
> On Wed, 19 Jan 2011 01:02:38 +0100, Michael D'Errico 
> <mike-list@pobox.com> wrote:
> 
>> Adam Langley wrote:
>>>  3.  Protocol Fallback
>>>     Lastly, some servers will negotiate the use of SSLv3 but select a
>>>    TLS-only cipher suite.
> 
> The AES suites are AFAIK only defined for TLS 1.0 and higher. And there 
> are also other ciphersuites that are defined for specific versions and 
> higher, particularly the SHA-256 suites.

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