Re: [secdir] [xmpp] SecDir review of draft-ietf-xmpp-3920bis-17
Peter Saint-Andre <stpeter@stpeter.im> Wed, 03 November 2010 21:53 UTC
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Cc: Security Area Directorate <secdir@ietf.org>, "draft-ietf-xmpp-3920bis.all@tools.ietf.org" <draft-ietf-xmpp-3920bis.all@tools.ietf.org>, XMPP Working Group <xmpp@ietf.org>, The IESG <iesg@ietf.org>, Matthew Wild <mwild1@gmail.com>
Subject: Re: [secdir] [xmpp] SecDir review of draft-ietf-xmpp-3920bis-17
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On 11/3/10 3:03 PM, Kurt Zeilenga wrote: > > On Nov 3, 2010, at 11:10 AM, Matthew Wild wrote: > >> On 3 November 2010 17:31, Peter Saint-Andre <stpeter@stpeter.im> >> wrote: >>> >> >>> as described under Section 13.7.2.1 (however, the lack of >>> channel binding in the PLAIN mechanism implies that even >>> authenticated TLS cannot fully protect the SASL negotiation and >>> subsequent communications when PLAIN is used). >>> >> >> I'm no expert on this, but is this text technically true? I >> thought channel binding would only be beneficial where there is not >> full TLS authentication. > > Channel binding is beneficial regardless of whether there the client > performed TLS server cert/subject checks. Note that the server has > no clue what checks, if any, the client (or its user) performed. > With channel bindings, it becomes irrelevant to the server whether > the client performed these checks or not. That is, (amongst other > things) channel bindings provide a means for the server itself to > protect against MITM attacks. > > I do agree, however, that he wording of the however comment is > confusing and seems should either be removed or replaced. Removed in my working copy. > My main concern is that Unauthenticated TLS is subject to downgrade > to PLAIN by two vectors, spoofing mechanisms and spoofing transition > required. > > Removing <transition-needed/> (in favor of a yet to be specified > extension) addresses one vector. > > There seems no good way to address the other vector at this time. I > do suggest however that the 13.9.4 text: To help prevent this attack, > the parties SHOULD protect the channel using TLS before attempting > SASL negotiation. be replaced with: To mitigate this attack, the > partied SHOULD protect the channel using TLS before attempting SASL > negotiation and either perform full certificate validation as > described in Section 13.7.2.1 or utilize a mechanism which provides > channel bindings, such as SCRAM-SHA-1-PLUS. Text incorporated, with minor tweaks. Peter -- Peter Saint-Andre https://stpeter.im/
- [secdir] SecDir review of draft-ietf-xmpp-3920bis… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Florian Zeitz
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Dave Cridland
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Dave Cridland
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Yaron Sheffer
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Jeffrey Hutzelman
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Yaron Sheffer
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Ben Campbell
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Ben Campbell
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Matthew Wild
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Philipp Hancke
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre