Re: [TLS] Last Call: <draft-ietf-tls-ssl2-must-not-03.txt>

Martin Rex <mrex@sap.com> Thu, 02 December 2010 18:45 UTC

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From: Martin Rex <mrex@sap.com>
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To: gwz@net-zen.net
Date: Thu, 02 Dec 2010 19:46:29 +0100
In-Reply-To: <000001cb9229$6a09e960$3e1dbc20$@net> from "Glen Zorn" at Dec 2, 10 09:01:23 pm
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Cc: ietf@ietf.org, tls@ietf.org
Subject: Re: [TLS] Last Call: <draft-ietf-tls-ssl2-must-not-03.txt>
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Glen Zorn wrote:
> 
> > Glen Zorn wrote:
> > > Section 3 says "TLS clients MUST NOT send SSL 2.0 CLIENT-HELLO
> > messages."
> > > and "TLS servers MUST NOT negotiate or use SSL 2.0" and later "TLS
> > servers
> > > that do not support SSL 2.0 MAY accept version 2.0 CLIENT-HELLO
> > messages as
> > > the first message of a TLS handshake for interoperability with old
> > clients."
> > > Taken together, I find these statements quite confusing, if not
> > outright
> > > self-contradictory.  Maybe, a "However" might fix the problem, though:
> > >
> > > 	TLS servers MUST NOT negotiate or use SSL 2.0; however, TLS
> > servers
> > > 	MAY accept SSL 2.0 CLIENT-HELLO messages as the first message of a
> > > 	TLS handshake in order to maintain interoperability with legacy
> > > 	clients.
> 
> Maybe I just don't understand the word "use".  It seems like if a server
> accepts a protocol message it's using the protocol...


With "negotiate" I meant returning a ServerHello handshake message with
that version number (neither an SSL 2.0 SERVER-HELLO, nor an SSLv3
ServerHello with a server version of { 0x02,0x00 }).

With "use" I meant to successfully complete the handshake and start
exchanging application data protected under protocol version {0x02,0x00}.


The Server accepts the SSL 2.0 CLIENT-HELLO protocol data unit (PDU),
but not the SSL 2.0 protocol.  If there are no SSLv3 or TLS cipher
suites in that CLIENT-HELLO, or if the (version) field of the
SSL 2.0 CLIENT-HELLO does not indicate at least 3.0, then the server
still MUST abort.


-Martin