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

Alan Johnston <alan.b.johnston@gmail.com> Sat, 25 January 2014 18:09 UTC

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Date: Sat, 25 Jan 2014 12:09:11 -0600
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From: Alan Johnston <alan.b.johnston@gmail.com>
To: "Scott G. Kelly" <scott@hyperthought.com>
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Cc: draft-ietf-cuss-sip-uui.all@tools.ietf.org, "secdir@ietf.org" <secdir@ietf.org>
Subject: Re: [secdir] secdir review of draft-ietf-cuss-sip-uui-10
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Scott,

Thanks for reviewing the draft again.  We will fix that mistake.

- Alan -


On Sat, Jan 25, 2014 at 9:18 AM, Scott G. Kelly <scott@hyperthought.com>wrote;wrote:

> Hi Alan,
>
> It appears that the modifications answer the questions I raised, but I
> again want to emphasize my lack of experience with SIP. One nit with the
> second paragraph of the security considerations section - it says
>
>    One model treats the SIP layer as untrusted and requires end-to-end
>    integrity protection and/or encryption.  This model can be achieved
>    by providing these security services at a layer above SIP.  In this
>    case, applications are encouraged to use their own integrity
>    mechanisms such as encrypting the UUI data before passing it to the
>    SIP layer.
>
> Encryption is not an integrity mechanism. One way to fix this would be to
> change that last sentence to something like
>
>    In this case, applications are encouraged to use their own integrity
>    and/or encryption mechanisms.
>
> Thanks,
>
> Scott
>
> On Thursday, January 23, 2014 11:44am, "Alan Johnston" <
> alan.b.johnston@gmail.com> said:
>
> > Scott,
> >
> > 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
> > concerns.
> >
> >      http://tools.ietf.org/html/draft-ietf-cuss-sip-uui
> >
> > Thanks!
> > - Alan -
> >
> >
> > On Thu, May 30, 2013 at 7:47 PM, Scott G. Kelly <scott@hyperthought.com
> >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
> >>
> >>
> >>
> >
>
>
>