Last Call Review of draft-ietf-xmpp-address-
review-ietf-xmpp-address-secdir-lc-barnes-2010-10-29-00

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 a data structure for addressing XMPP resources. 


 As such, it has the potential to create authentication issues, in 


particular related to spoofing and mimicry of addresses.  The document 


does a good job of describing these risks and available mitigations, but 


could use a little bit of clarification on a few points.




Detailed comments follow.

--Richard




Major issues:



General: It's not clear to me from the text in this document JIDs differ 


from XMPP URIs.  My naïve assumption would be that an XMPP URI would 


simply be a JID with the scheme "xmpp:" prepended, but the last 


paragraph of Section 2.1 made me uncertain about this.  (I have not 


checked RFC 5122 to verify whether this is the case syntactically.) 


Since many client applications will have to convert from XMPP URIs to 


JIDs -- and because this is a security-sensitive operation -- it seems 


like it would be helpful for this document to specify conversions 


between XMPP URIs and JIDs, even if only by reference to RFC 5122.




S4.3:


It seems like there should be some discussion here about how entities 


that create JIDs can help mitigate issues of confusability.  For 


example, the existence of confusable characters in the domainpart is 


mitigated by proper registry policies (which I presume could be 


incorporated by reference to some IDNA documents).  Localparts and 


resourceparts are not constrained  to be domain names, but they are 


controlled or at least approved by a server, so the server can apply 


similar policies to these parts.




S4.4.1 P2:


The observation that only part of an identifier can be authenticated is 


a good one to make, but there's one subtlety: The remote server is 


actually authoritative for the localpart and resourcepart of the JID, so 


the fact that the remote domain has assigned a particular 'from' address 


effectively authenticates those fields when the domain is authenticated. 


 It might help to note that end-to-end authentication of XMPP stanzas 


could help mitigate this risk, since it would require the rogue server 


to generate false credentials in addition to modifying 'from' addresses.





Minor issues:



S2.2 P2: For clarity, I would change the "SHOULD be an FQDN, can be an 


IP address or unqualified host name" to "MUST be an FQDN, IPv4 address 


literal, IPv6 address literal, or unqualified host name".  If the 


intention here is that unqualified host names should have the same 


syntax as FQDNs, then that should be stated.






S2.2 P3: Not clear why this is a "Note:" paragraph, especially since it 


has "MUST" requirements in it.