Re: [Geopriv] Consensus on changes to location-conveyance

At 1:38 PM -0400 7/25/06, Rosen, Brian wrote:
>4. We proposed to explicitly allow hop-by-hop TLS security for location
>when the endpoint wished to allow routing based on location.  We further
>proposed to interpret "Do not Distribute" flags as allowing sending of
>the location to the routing database (LoST for example).  Hannes pointed
>out that there was a proposal to allow two Location headers, one of
>which could be used for routing and another for onward forwarding to the
>recipient.  Hannes' message seemed to agree that "Do not distribute"
>would allow sending of the location to the routing-by-location database,
>but would obligate the proxy that did that to remove the location before
>it forwarded the message.  There were no other messages on this thread.

Actually, I commented on the same problem, though it may have been
connected to one of the related threads; here's the text of that message:

>At 5:23 PM -0400 7/19/06, Brian Rosen wrote:
>>NOTE: THIS MESSAGE IS COPIED TO SIP AND ECRIT, IF YOU REPLY, SEND IT ONLY TO
>>GEOPRIV
>>However, this opens up the issue of geopriv privacy concerns because the
>>sender does not know the identity of the element (proxy) that will route the
>>call using LoST.  It may be that the UAC itself does this, but it may be
>>some other intermediary.
>>
>>If the identity of the intermediary is not known, then protecting the
>>location information becomes more difficult, because we cannot encrypt using
>>keying material from the intended recipient.
>
>Just to mention this, it appears to also rule out the idea of encrypting
>with the user's key, since there is no way of knowing whether the "intended
>recipient" has that key material either.  Intended recipient is actually
>a bit of a problematic term here, since it's really the on-path network elements
>which consume the information.  They aren't the intended recipient of
>the communication, they are the recipients of the signaling (of which location
>is now a part).
>
>This is a bit confusing because it seems to be possible to include a
>"re-transmission allowed"  rule with a value of "no" (intended to be
>consumed by the "intended recipient" of the underlying communication),
>while still wanting to allow the location to be passed along the path.
>
>>In fact, we would need to use
>>hop-by-hop security, with transitive trust.  This is what the emergency case
>>does, but it also allows no channel security if necessary (usually meaning,
>>try it with TLS and if that fails, try again without TLS).
>
>While I certainly encourage hop-by-hop security, I don't think it really
>meets the geopriv privacy concerns.  I think you  have to have some way of
>expressing "re-transmission for routing permitted" (and likely retention
>limited), since that is a separate statement.
>
>Just typing aloud here, but could we come up with a way to use an
>external ruleset to express this?  With an embedded cid, that would
>not actually require dereferencing.
>					Ted
>



>We conclude that allowing hop-by-hop security for location based routing
>is acceptable, and Do Not Distribute DOES allow forwarding to a routing
>database, but requires that the proxy doing the location based route to
>remove the location it uses for that purpose.

To reiterate this, I do not believe that this is sufficient; I think you have to
have some way of saying "re-transmission for routing permitted" before
you meet the geopriv privacy concerns.

>5. We proposed to create a parameter and a registry to distinguish
>multiple ways to dereference a location where HTTP(S) was the transport.
>Resolution of this issue depends on resolution of issue 6.

I believe that an HTTP GET of a PIDF-LO object is a reasonable baseline.
Saying that other mechanisms should update this document with their
dereferencing mechanisms if they could be confused with the baseline
seems to me to be sufficient.  I'm not sure a registry is needed.  In practice,
I don't think we would hit the interoperability problems often. These days,
extensions to HTTP commonly use different  mime types to indicate the special
handling, and I expect anyone creating a more feature-rich dereferencing
mechanism built on HTTP would not end up using pidf-lo.  

That means the "uri confusion" aspects of the discussion are probably not
that severe.  The only issue is if someone supports only the more feature-rich
alternative and not a baseline GET of the pidf-lo.  I think we should
discourage that, by establishing a real baseline.

Note also that HTTP URIs don't indicate the HTTP Method directly; often they
support multiple methods (e.g. HEAD and GET).

>6. We proposed to allow sip/sips and pres: in the location header.  I
>later speculated that if we allow this, it forms a simple way to do
>location-by-reference, and we could eliminate the raw HTTP(S) Get
>proposal, with the parameter and registry entirely.  There was some list
>traffic in favor of this.  Martin Thompson is skeptical that SIP
>Presence Subscribe/Notify is actually allowed as a geopriv "using
>protocol".  Several of think that it is.  If we don't get any more
>comments on this proposal, we will allow sip/sips and pres, not have any
>http(s) resolution text, and not propose a parameter and accompanying
>registry.

I share some of Martin's skepticism here, but I won't fall on my sword
if the WG goes in this direction.

Thanks for the clear set of issues and opportunity to comment,
				
					Ted Hardie

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email protected] for questions on current sip
Use [email protected] for new developments on the application of sip