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Re: [TLS] Analysis of Interop scenarios TLS extension RI w/MCSV

Marsh Ray <marsh@extendedsubset.com> Fri, 11 December 2009 16:33 UTC

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Date: Fri, 11 Dec 2009 10:33:28 -0600
From: Marsh Ray <marsh@extendedsubset.com>
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To: David-Sarah Hopwood <david-sarah@jacaranda.org>, "tls@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] Analysis of Interop scenarios TLS extension RI w/MCSV
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David-Sarah Hopwood wrote:
> 
> Why? What is the point of allowing the client to send an empty extension,
> when a patched client MUST send the MSCV, and a patched server MUST use
> *only* the MSCV to determine whether the client is patched? You'd just be
> adding the option to send an extension that has no defined meaning.

I would like for the decisions we make today to allow the MCSV hack to
be retired at some point in the future. MCSV represents extra complexity
that we added as a concession for interoperability with obsolete and
out-of-spec systems. We all have to make compromises in life and
protocol design, but it is better to do it in such a way that they
eventually pass into history rather than build up over time.

Today there are many clients which never interoperate with
extensions-intolerant servers. If at all possible, these should have the
option of not sending the MCSV hack from the beginning.

- Marsh

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