Re: [TLS] Accept draft-turner-ssl-must-not-02 as WG item
Martin Rex <mrex@sap.com> Wed, 15 September 2010 01:55 UTC
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From: Martin Rex <mrex@sap.com>
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To: turners@ieca.com
Date: Wed, 15 Sep 2010 03:55:28 +0200
In-Reply-To: <4C8F8CBB.2090002@ieca.com> from "Sean Turner" at Sep 14, 10 10:54:51 am
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Cc: tls@ietf.org
Subject: Re: [TLS] Accept draft-turner-ssl-must-not-02 as WG item
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Sean Turner wrote: > > Michael D'Errico wrote: > > Eric Rescorla wrote: > >> In Maastricht, we saw a presentation on draft-turner-ssl-must-not: > >> > >> http://tools.ietf.org/html/draft-turner-ssl-must-not-02 > >> > >> The consensus in Maastricht was to adopt this as a WG item. If anyone > >> objects please speak up now. > > > > No objection to taking it on as a WG item, but I do have a concern > > with section 3: > > > > 3. Changes to TLS > > [...] > > o TLS servers MUST NOT accept SSL 2.0 ClientHello messages. > > > > I still see many SSLv2 ClientHellos, and none of them are SSLv2-only > > clients. So at this point in time I think MUST NOT is too strong on > > the server side. I don't think using an SSLv2 hello is a security > > problem since it supports the TLS_EMPTY_RENEGOTIATION_INFO_SCSV > > cipher suite value. > > Unless anybody else objects I'll make the following swap: > > OLD: > > o TLS servers MUST NOT accept SSL 2.0 ClientHello messages. > > NEW: > > o TLS servers SHOULD NOT accept SSL 2.0 ClientHello messages. A "SHOULD NOT" without a rationale appears not compliant with rfc-2119. Personally I can not think of a reason to move away from what rfc-5246 appendix E.2 says. AFAIK, the problem is strictly limited to negotiating and talking SSLv2. Accepting an SSL v2.0 CLIENT-HELLO as the first message of an SSLv3 or TLSv1.x handshake precludes the sending of TLS extensions and negotiating a compression alg, but does not seem to cause any harm otherwise. I would appreciate if the original wording of rfc-5246 Appendix E.2 would be retained absent a convincing rationale to change it. http://tools.ietf.org/html/rfc5246#page-89 However, even TLS servers that do not support SSL 2.0 MAY accept version 2.0 CLIENT-HELLO messages. -Martin
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Martin Rex
- [TLS] Accept draft-turner-ssl-must-not-02 as WG i… Eric Rescorla
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Peter Gutmann
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Paul Hoffman
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Michael D'Errico
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Sean Turner
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Marsh Ray
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Yoav Nir
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Peter Saint-Andre
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Martin Rex
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Russ Housley
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Martin Rex
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Geoffrey Keating
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Simon Josefsson
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Sean Turner
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Sean Turner
- Re: [TLS] Accept draft-turner-ssl-must-not-02 as … Martin Rex