Re: [secdir] [xmpp] SecDir review of draft-ietf-xmpp-3920bis-17

Kurt Zeilenga <Kurt.Zeilenga@Isode.COM> Tue, 02 November 2010 19:03 UTC

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From: Kurt Zeilenga <Kurt.Zeilenga@Isode.COM>
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To: Peter Saint-Andre <stpeter@stpeter.im>
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Subject: Re: [secdir] [xmpp] SecDir review of draft-ietf-xmpp-3920bis-17
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On Nov 2, 2010, at 9:37 AM, Peter Saint-Andre wrote:

>> 
>> I suspect I'm in the rough on both points.  Oh well.
>> 
>>> 2. The technology that the XMPP community uses for account
>>> registration (XEP-0077) could benefit from an update, or even a
>>> replacement, and when that work is completed I'd like to include a
>>> method by which a client could register a key or cert with the
>>> server, thus smoothing the path toward password-less
>>> authentication. IMHO that will be the best approach in the longer
>>> term, instead of continually tweaking the password-based methods.
>>> But that's a topic for another time...
>> 
>> I also think transition-needed needs to be deprecated in favor of
>> transition within the bound channel (e.g., today via XEP 77, tomorrow
>> ?).
> 
> I'm not sure exactly what "transition within the bound channel" is, but
> it sounds worthy of discussion when we work on 3920ter.

The problem with transition-needed is that the error is sent outside the bound channel.

By "within the bound channel", I mean a transitioning method, including any necessary signaling, would be performed inside the bound channel, that is, within the new <stream:stream/> protected by the SASL exchange.

> At this point I
> don't think the XMPP community has a great deal of experience with, or
> even understanding of, channel binding, so it's difficult for us to make
> strong recommendations that depend on channel binding.

It would be same issue of doing transition outside of a SASL negotiated security layer.  It's prone to attack.  And the fix is the same.

-- Kurt