Subject: RE: [Geopriv] Consensus on changes to location-conveyance

From: Ted Hardie <[email-masked]>
Date: Tue, 25 Jul 2006 13:33:31 -0700

At 2:45 PM -0400 7/25/06, Rosen, Brian wrote:
>Summarizing, you think hop-by-hop security (TLS) is acceptable when the
>location is sent for the purposes of location based routing, but you are
>not in favor of defining "retransmission=no" to permit sending the
>location to the routing database (e.g. LoST).  You want a more explicit
>permission.

Yes.

>I don't think a cid: with a ruleset is acceptable, as it would not
>permit location by reference added by a proxy to specify this.

Fair enough.

>If this is the consensus, I think we would have to add a bit to the PIDF
>to explicitly control this behavior.

I think an extension that says "retransmission for routing=yes" is the cleanest
way to go.

>Why do you think we must specify an HTTP dereference procedure in this
>document?  What is the purpose when the SIP based method is available?
>We had believed we had to have SOME method of dereferencing to make
>location-by-reference meaningful in the document.  If we have one sip
>based method, we meet the requirement.  Having more options, especially
>completely new HTTP based protocols IN THIS DOCUMENT seems unnecessary
>and unwise.  For example, if we define such a protocol, it becomes a
>geopriv "using protocol" and needs an explicit analysis against the
>geopriv criteria.

I don't think we have to do it in this document, but I read your previous
message as a statement of consensus about the HTTP dereference mechanisms
that have been discussed.   I don't agree with that statement, since I think the
HTTP discussions somewhat over-thought the potential problems.  In particular, a
lot of the discussion was around the idea that http://dereference.example.org/foo-pidf-lo
might mean lots of different things, depending on what http meant.  There are
already ways to deal with that; none of them are perfect (see, for example,
the discussion in draft-reschke-webdav-mount-05.txt and its appendix A for a similar
problem in a different context), but they can work, especially if you set a baseline
approach.

				regards,
					Ted Hardie

>Brian
>
>> -----Original Message-----
>> From: Ted Hardie [mailto:[email-masked]]
>> Sent: Tuesday, July 25, 2006 2:19 PM
>> To: Rosen, Brian; [email-masked]
>> Cc: [email-masked]
>> Subject: 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

_______________________________________________
Geopriv mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/geopriv

---

From: "Rosen, Brian" <[email-masked]>
Date: Tue, 25 Jul 2006 14:45:15 -0400

Brian

location
further
of
pointed
the
database,
before
thread.
the
route
may be
the
encrypt
encrypting
actually
network
communication),
path.
emergency
really
way
retention
routing
routing
to
you
transport.
baseline.
dereferencing
not
feature-
often
list
any

---

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 26 Jul 2006 11:07:39 -0400

> document?  What is the purpose when the SIP based method is available?

Unless you care about performance. I suspect that the SIP approach  
will take at least twice as many server resources as the HTTP  
approach (which will, in turn, take twice as much server capacity as  
the by-value approach). Strangely, ease of implementation and speed  
don't seem to matter in this discussion, so maybe that's a non-issue.