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Re: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00

Brian Smith <brian@briansmith.org> Fri, 26 September 2014 20:31 UTC

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Date: Fri, 26 Sep 2014 13:31:19 -0700
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From: Brian Smith <brian@briansmith.org>
To: Bodo Moeller <bmoeller@acm.org>
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Subject: Re: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00
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On Fri, Sep 26, 2014 at 1:21 PM, Bodo Moeller <bmoeller@acm.org> wrote:
> If the server is version-intolerant for new sessions, why would it be
> tolerant on (attempted) resumption?

First, the client tries to handshake with client_version == TLS 1.2 and fails .

Then the client tries to handshake with client_version == TLS 1.1 and
succeeds, with the server choosing TLS 1.0.

Later, the client tries to resume the previously negotiated session.
It could choose client_version == TLS 1.1 (ignoring the session
version, but remembering the version intolerance), or it could choose
client_version == TLS 1.0 (using the session version). My argument is
that the client should choose client_version == TLS 1.1 and send the
SCSV.

Cheers,
Brian

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