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Re: [TLS] simplistic renego protection

Marsh Ray <marsh@extendedsubset.com> Sat, 21 November 2009 23:05 UTC

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Date: Sat, 21 Nov 2009 17:04:54 -0600
From: Marsh Ray <marsh@extendedsubset.com>
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To: Ben Laurie <benl@google.com>
References: <C72BFA89.67A2%stefan@aaa-sec.com> <4B06E2D7.2040302@jacaranda.org> <1b587cab0911211147jf3f57b3y8528717b152cd8c2@mail.gmail.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] simplistic renego protection
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Ben Laurie wrote:
> 
> On Fri, Nov 20, 2009 at 10:41 AM, David-Sarah Hopwood
> <david-sarah@jacaranda.org <mailto:david-sarah@jacaranda.org>> wrote:
> 
>     I'm skeptical. How can "proper channel binding" be done correctly in a
>     layer above TLS, if the TLS library merges renegotiated sessions?
>     Since the session merging will result in the client and server's state
>     at the higher layer(s) being out of sync, nothing can be assumed about
>     the correct functioning of those layers.
> 
> 
> The depends on those layers. If, for example, clients and servers simply
> numbered their requests/responses, they would be immune to the attack.

MitM may be able to prep the client to match the sequence number of the
server at the point of splicing.

- Marsh

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