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

"Glen Zorn" <gwz@net-zen.net> Fri, 03 December 2010 04:43 UTC

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From: "Glen Zorn" <gwz@net-zen.net>
To: <mrex@sap.com>
References: <000001cb9229$6a09e960$3e1dbc20$@net> from "Glen Zorn" at Dec 2, 10 09:01:23 pm <201012021846.oB2IkTCi019858@fs4113.wdf.sap.corp>
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Date: Fri, 3 Dec 2010 11:44:18 +0700
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Subject: Re: [TLS] Last Call: <draft-ietf-tls-ssl2-must-not-03.txt>
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Martin Rex [mailto:mrex@sap.com] writes:

> 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}.

Maybe you could spell these things out in the draft just as you have above?

> 
> 
> The Server accepts the SSL 2.0 CLIENT-HELLO protocol data unit (PDU),
> but not the SSL 2.0 protocol.  

I see.  Perhaps the distinction between PDU and "protocol" is just too
subtle for me, but assuming (maybe too generously ;-) that I'm not a total
moron, others might find it a little bit confusing as well.


> 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