Re: [TLS] TLS renegotiation issue

Martin Rex <mrex@sap.com> Thu, 05 November 2009 18:15 UTC

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From: Martin Rex <mrex@sap.com>
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To: Nicolas.Williams@sun.com (Nicolas Williams)
Date: Thu, 5 Nov 2009 19:16:02 +0100 (MET)
In-Reply-To: <20091105175044.GG5124@Sun.COM> from "Nicolas Williams" at Nov 5, 9 11:50:44 am
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Cc: ekr@rtfm.com, tls@ietf.org
Subject: Re: [TLS] TLS renegotiation issue
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Nicolas Williams wrote:
> 
> > The MITM can make sure they match.
>
> I should expand on this.
>  [helpful explanantion removed]

Blush -- you are correct.

The MITM can make the two previous sessions come out with the same
client.random and server.random.

So these are not a secure back pointer.

> 
> You can't use the client.random and server.random as channel bindings.

I'm trying to use terminology that is already in the TLS specs.
The generic term "channel bindings" is a little bit to fuzzy for
my taste, and the original use of channel bindings in GSS-API
is not cryptographically secure.

> 
> But the client's Finished message from the outer TLS connection works.

OK.

You win.  ;-)


-Martin