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Re: [TLS] advertizing the minimum TLS supported version [was: Last Call: <draft-ietf-tls-downgrade-scsv-03.txt>]

Michael Clark <michael@metaparadigm.com> Thu, 22 January 2015 10:40 UTC

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Date: Thu, 22 Jan 2015 18:40:17 +0800
From: Michael Clark <michael@metaparadigm.com>
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To: Nikos Mavrogiannopoulos <nmav@redhat.com>
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Subject: Re: [TLS] advertizing the minimum TLS supported version [was: Last Call: <draft-ietf-tls-downgrade-scsv-03.txt>]
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On 22/1/15 6:24 pm, Nikos Mavrogiannopoulos wrote:
> On Thu, 2015-01-22 at 18:11 +0800, Michael Clark wrote:
>>> 3. Forbidding SSL 3.0 version from the record layer breaks perfectly
>>> valid clients, which advertise TLS 1.2. These clients can only use a
>>> variant of fallback dance to connect to broken servers which impose
>>> those limits. Please _DON'T CREATE MORE REASONS FOR FALLBACK DANCES_.
>> OK. Then an extension to indicate supported versions would in fact be an
>> improvement as it would be protected by verify_data.
> 
> Some time ago, I had proposed a method for clients to advertise the list
> of protocols they support, for the same reason. To allow the server to
> fallback to their preferred protocol:
> https://tools.ietf.org/html/draft-mavrogiannopoulos-tls-more-extensions-00#section-4

Good idea. Thanks I understand now. More logical than SCSV to have the
minimum version in the handshake hash.

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