Re: [secdir] secdir review of draft-ietf-cuss-sip-uui-10

Alan Johnston <> Thu, 23 January 2014 19:44 UTC

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Date: Thu, 23 Jan 2014 13:44:31 -0600
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From: Alan Johnston <>
To: "Scott G. Kelly" <>
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Subject: Re: [secdir] secdir review of draft-ietf-cuss-sip-uui-10
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Thanks for your review of the draft.  We made some edits based on your
comments a while back, so I'm pinging you to make sure they address your

- Alan -

On Thu, May 30, 2013 at 7:47 PM, Scott G. Kelly <>wrote;wrote:

> 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 have no expertise in SIP, and am providing this review as a first-level
> filter for our over-worked security ADs. So, please take my comments
> accordingly. Also, this review is a day late -- I hope it is still useful.
> This document defines a method for exchanging a blob of information
> between user agents during SIP session establishment (User to User
> Information, or UUI data) by adding a new SIP header. The data is intended
> to be opaque to SIP.
> There is a related problem statement RFC (6567) that briefly describes 3
> different approaches to security, but neither document describes likely
> threats. They are implicit in the 3 models described in 6567 (e.g. treat
> the sip layer as "untrusted", treat the sip layer as "trusted", treat the
> transport domain as "trusted"), but I found myself wishing I had more info
> about real-world threats and countermeasures.
> Given that I am not a SIP expert (and don't have time to become one as
> part of this review), I don't know if this is an issue or not, but this is
> an impression I think worth mentioning.
> A second question relates to the binding of the UUI to its originator. The
> security considerations section suggests that the UUI might carry sensitive
> info requiring privacy or integrity protection, but does not mention origin
> authentication. There is a hint in the next paragraph (it says
> "History-Info can be used to determine the identity of the inserter"), but
> the relative security of this mechanism is not clear to me. Could an
> attacker forge History-Info? I don't know. What are the consequences of
> such behavior? I don't know. Seems like a well-written security
> considerations section would lay these questions to rest.
> Again, I have almost zero knowledge of SIP, so maybe answers are obvious
> to someone steeped in SIP lore, and I apologize if this is the case. But,
> these are my impressions.
> --Scott