Re: [TLS] CCS and key reset and renegotiation

Martin Thomson <martin.thomson@gmail.com> Thu, 05 June 2014 15:54 UTC

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Date: Thu, 5 Jun 2014 08:53:52 -0700
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From: Martin Thomson <martin.thomson@gmail.com>
To: "Salz, Rich" <rsalz@akamai.com>
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Subject: Re: [TLS] CCS and key reset and renegotiation
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On 5 June 2014 08:41, Salz, Rich <rsalz@akamai.com> wrote:
>> I don't see why the incompetence of implementors should govern our
>> decisions. If something cannot be implemented correctly it must be removed,
>> but why is rekeying such a thing?
>
> Because the line between “often get it wrong” and “cannot be implemented” is
> often a very thin one and it’s better to be cautious and safe, then
> pedantically correct and usually broken.


I tend to agree with Watson here.  This is a problem that happens
during the initial handshake only.  Maybe we can design the handshake
to ensure that CCS cannot be abused for TLS 1.3.  But I don't see how
this vulnerability extends to subsequent handshakes or rekeying
exchanges.