[secdir] SECDIR review of draft-ietf-xmpp-3921bis-15.txt

["Richard L. Barnes" <[e-mail]>]

I have reviewed this document as part of the security directorate's 
ongoing effort to review all IETF documents being processed by the IESG. 
  These comments were written primarily for the benefit of the security 
area directors.  Document editors and WG chairs should treat these 
comments just like any other last call comments.

This document describes an instant-messaging and presence system based 
on the core system of exchanging XML stanzas described in RFC 3920 and 
draft-ietf-xmpp-3920bis.  As the document rightly notes, the underlying 
transport protocol addresses most of the security considerations for 
this document, and that document seems to have a thorough discussion of 
security considerations (although I have not done a thorough review). In 
general, I think that the security considerations in this document 
adequately describe the additional risks posed by the instant-messaging- 
and presence-specific parts of the protocol (beyond those of the base 
protocol), and corresponding mitigations.

One thing that might merit clarification: The overriding 
application-layer security concern here is the proper routing of 
presence and instant messaging stanzas through the XMPP system. 
(Underlying communications security concerns are addressed by the core 
spec.)  For the most part, these concerns with requirements on servers 
to act in certain ways on behalf of the user.  It could be helpful to 
the reader to re-state some of the communications patterns from Section 
13.1 of draft-ietf-xmpp-3920bis and comment on the particular roles that 
the entities play in the context of instant messaging and presence 
(e.g., routing unicast <message> stanzas, fan-out of broadcast presence 
messages).

--Richard