Re: [TLS] Last Call: <draft-ietf-tls-ssl2-must-not-03.txt> (Prohibiting SSL Version 2.0) to Proposed Standard

Nikos Mavrogiannopoulos <> Thu, 02 December 2010 08:20 UTC

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Date: Thu, 02 Dec 2010 09:22:03 +0100
From: Nikos Mavrogiannopoulos <>
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Subject: Re: [TLS] Last Call: <draft-ietf-tls-ssl2-must-not-03.txt> (Prohibiting SSL Version 2.0) to Proposed Standard
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On 12/02/2010 07:15 AM, Michael D'Errico wrote:
> Matt McCutchen wrote:
>> On Wed, 2010-12-01 at 21:49 -0800, Michael D'Errico wrote:
>>> If you couldn't put the SCSV into the CLIENT-HELLO, then it would not
>>> be OK for servers to accept that message; it would have to be a MUST
>>> NOT.
>> You have just said the same thing again.  Why?  What potential security
>> problem be prevented by the server not accepting a SSL 2.0 CLIENT-HELLO?
> I'm not sure why you're objecting to my comment.
> We are deprecating SSL version 2.0.  However, we are allowing the
> continued acceptance of the SSL 2.0 CLIENT-HELLO by TLS servers.
> It would be irresponsible for us to do that if it left open the
> renegotiation hole that was closed via the RenegotiationInfo
> extension (and SCSV), and I wouldn't support it if that were the
> case.
> I was merely pointing that out.

Indeed but this is an argument not mentioned in the document at all.
Maybe a paragraph of security considerations could be added (or is it
too late?), that will mention that certain (current or future)
security-related extensions is not possible to be supported by an SSL 2
hello message, although this is not the case with SCSV.

Merely as an argumentation on why accepting SSL 2 hello messages is a