Subject: [secdir] secdir review of draft-ietf-avtext-rtp-stream-pause-08

From: David Mandelberg <[email-masked]>
Date: Tue, 11 Aug 2015 00:45:25 -0400

Hi,

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.

I think this draft is Ready with issues, though the two issues are 
relatively minor:

1. The Security Considerations section talks about protecting against 
injection of PAUSE requests:

    The way of protecting the RTP session from these injections is to
    perform source authentication combined with message integrity, to
    prevent other than intended session participants from sending these
    messages.

I think this paragraph should also mention replay protection, which is 
needed if the 16-bit PauseID wraps around and the attacker has access to 
old PAUSE requests.

2. The next paragraph in Security Considerations talks about protecting 
the multi-party use case against a single malicious participant by 
individually authenticating participants. In addition to per-participant 
authentication, I think there also needs to be a requirement for 
attempted delivery of PAUSE requests to all participants. Without that 
requirement, an attacker could cause the session to cycle through the 
Playing, Pausing, and Paused states. To do that, the attacker would send 
PAUSE requests only to the stream sender, instead of to the whole group. 
Since no other participants receive the PAUSE request, they do not know 
to send disapproving RESUMEs until after the stream sender has already 
paused the stream. (I should note that I'm not particularly familiar 
with multicast network operations. If it's infeasible for one 
participant to send a message to another participant without the rest of 
the group also receiving the message, then I apologize for bringing up a 
non-issue.)

-----

I also have a few nits:

Abstract: The RTCP initialism is used without definition.

Section 5.4: The SR initialism is used without definition.

Section 6.4: I'd suggest changing "As for Paused State" to "As with 
Paused State". That sentence could also be split up for better 
readability.

-- 
David Eric Mandelberg / dseomn
http://david.mandelberg.org/