Re: [TLS] [mogul-open] Interoperability testing
Martin Rex <mrex@sap.com> Fri, 08 January 2010 01:11 UTC
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From: Martin Rex <mrex@sap.com>
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To: mogul-open@lists.links.org
Date: Fri, 08 Jan 2010 02:10:32 +0100
In-Reply-To: <4B451355.4010108@bolyard.me> from "Nelson B Bolyard" at Jan 6, 10 02:48:53 pm
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Cc: iab@iab.org, tls@ietf.org, iesg@iesg.org
Subject: Re: [TLS] [mogul-open] Interoperability testing
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Nelson B Bolyard wrote: > > On 2010-01-06 14:30 PST, Eric Rescorla wrote: > > I agree with Marsh here. > > > > Any server which is going to implement this draft, SSLv3 or otherwise > > is going to need to process RI correctly (whehter empty or not, > > but especially if not because otherwise it can't renegotiate at all). > > The only reason to send SCSV is if you're afraid to send RI because > > you think an unupgraded server might break on it. > > My understanding of this draft is that it does NOT require upgraded SSL 3.0 > servers to understand any extensions in _initial_ handshakes. An SSL 3.0 > server that ignores all handshakes (per the "draft-02" version of the 3.0 > spec), but understands SCSV, can be fully compliant with this draft. > > I have come to expect that that will be the norm for upgraded SSL 3.0 > servers. They will not, in general, understand any extensions in initial > client hellos, and will only understand one extension in renegotiation > client hellos, namely a non-empty RI. > > Consistent with that expectation, I believe SCSV is the only reliable way to > request renegotiation protection from upgraded SSL 3.0 servers. > > Is that not the compromise we reached with Martin Rex? I'm similarly confused. The -03 document does not reflect WG consensus on the use of SCSV. And the document is unnecessarily complicated and inconsistent. OK: 3.3 "... the SCSV may be safely sent to any server." OK: 3.4 "MUST include ... TLS_RENEGO_PROTECTION_REQUEST signal(l)ing cipher suite value in every ClientHello. not good: 3.4 "MUST include and empty "renegotiation_info" extension ... in every ClientHello" because the empty renegotiation_info applies only to ClientHellos of initial handshakes. bad: 3.4 "Including both is not recommended." Working group consensus is that both may be included. very bad: 3.5 "The SCSV MUST NOT be included." There is no working group consensus for this MUST NOT, and not a single technical argument for this MUST NOT has been given during the last 2 months. Simply removing the two last mentioned sentences will improve the document and reflect working group consensus. -Martin