Last Call Review of draft-ietf-mmusic-msrp-usage-data-channel-22
review-ietf-mmusic-msrp-usage-data-channel-22-secdir-lc-melnikov-2020-07-20-00

Reviewer: Alexey Melnikov
Review result: Ready with Nits

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.

The subject matter is outside my area of expertise and proper 
understanding of the document requires reading of several referenced 
documents. But I think I got the gist of what the document is trying to do.

The Security Consideration talks about data channels providing 
confidentiality, integrity and source authentication for MSRP traffic, 
which is good. It also points out to discussion of MSRP message 
attribution in RFC 4975.

However, session setup is done over SIP, which has different security 
considerations and nothing is mentioned about that. In particular, one 
of normatively referenced documents RFC 5547 has very good Security 
Considerations section (section 10) that talks about possible attacks on 
file transfer negotiation. I think this should be referenced in the 
document.

I also feel that more can be said about possible use of MSRP for 
transferring of malicious files/images.

In Section 6:

  o  The gateway SHALL use CEMA towards the non-data channel endpoint.

Please explain and/or add a reference for CEMA.