Re: [TLS] Negotiating with known_configuration

Eric Rescorla <ekr@rtfm.com> Tue, 21 July 2015 11:13 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Tue, 21 Jul 2015 13:12:38 +0200
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To: Martin Thomson <martin.thomson@gmail.com>
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Subject: Re: [TLS] Negotiating with known_configuration
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On Tue, Jul 21, 2015 at 1:10 PM, Martin Thomson <martin.thomson@gmail.com>
wrote:

> On 21 July 2015 at 04:04, Eric Rescorla <ekr@rtfm.com> wrote:
> > - The client indicates configuration ID and cryptographic configuration,
> >   including the cipher suites and cryptographic extensions. This
> >   MUST replicate the server's selection from a previous handshake
>
>
> That's not going to work if there was no previous session.  For
> instance, if the configuration was learned out of band.


Yes, that's an issue. Not entirely sure what to do about other than
have the server provide its negotiation preferences out of band
in that case.


 It also

implies that the selection can come from ANY previous session, where I
> think that it only makes sense to identify the session where the
> configuration was learned.
>

I agree with this point.

-Ekr