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

Florian Weimer <fweimer@redhat.com> Wed, 15 October 2014 15:35 UTC

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Date: Wed, 15 Oct 2014 17:35:17 +0200
From: Florian Weimer <fweimer@redhat.com>
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Subject: Re: [TLS] Working Group Last Call for draft-ietf-tls-downgrade-scsv-00
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On 10/11/2014 08:36 AM, Andrey Jivsov wrote:
> On 09/25/2014 09:00 PM, Joseph Salowey (jsalowey) wrote:
>> This is an announcement for the working group last call for
>> draft-ietf-tls-downgrade-scsv-00.  Please review the document and send
>> your comments to the list by Friday, October 17, 2014.
>>
>> Thanks,
>> J&S
>
>
>> 3. Server behavior
>
> Suppose a server and a client support TLS1.2, client starts with TLS1.2
> but network failure makes the client reconnect with TLS1.1. Or perhaps
> there is an occasional bug in TLS1.2 path on the client or the server,
> leading to the same TLS1.1 reconnect.
>
> In this case the server is prescribed to fail with
> inappropriate_fallback for TLS1.1 + SCSV.

This scenario is described here:

<https://bugzilla.mozilla.org/show_bug.cgi?id=450280>

SCSV implementation would make things worse for Firefox users because it 
results in a reliable connection failure instead of a downgrade from TLS 
1.1 to TLS 1.2.

-- 
Florian Weimer / Red Hat Product Security

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