Re: [rtcweb] Text proposal for CNAME in draft-ietf-rtcweb-rtp-usage

Martin Thomson <martin.thomson@gmail.com> Tue, 15 April 2014 17:33 UTC

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Date: Tue, 15 Apr 2014 10:33:04 -0700
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From: Martin Thomson <martin.thomson@gmail.com>
To: Magnus Westerlund <magnus.westerlund@ericsson.com>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>, Colin Perkins <csp@csperkins.org>
Subject: Re: [rtcweb] Text proposal for CNAME in draft-ietf-rtcweb-rtp-usage
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The text looks fine, with one comment.

On 15 April 2014 05:10, Magnus Westerlund
<magnus.westerlund@ericsson.com> wrote:
>       Note: It is important that the same CNAME is not used in different
>       communication session contexts or origins, as that could enable
>       tracking of a user and its device usage of different services.
>       See Section 4.4.1 of Security Considerations for WebRTC
>       [I-D.ietf-rtcweb-security] for further discussion.

I'd rather not have this hidden in a "Note", and I'd prefer if it were
more concrete.  I think that we need to say something like:

A different CNAME MUST be used for different RTCPeerConnection
instances.  Having two communication sessions with the same CNAME
could enable tracking of a user or device across different services
(see Section 4.4.1 of [security] for details).  A web application MAY
override the CNAME that is selected using the process in [RFC7022] to
allow for synchronization of disjoint sessions; [[this doesn't result
in a tracking issue, since the creation of matching CNAMEs depends on
existing tracking]].