Re: R: R: [Sip] a question about IETF draft location conveyance 09

[Matt Lepinski <[e-mail]>]

James,

I do believe that the intent of Ted (as well as others in the GEOPRIV 
working group, including myself) is that if a UAC specifies 
"recipient=endpoint" then a compliant proxy will not 'read' the location 
body. In particular, "recipient=endpoint" indicates that a SIP proxy in 
the signaling path does not have permission to store the location (or 
any derived information) for longer than is necessary to forward the SIP 
message and does not have permission to send the location to any third 
party (for any reason including location-based routing) other than the 
next-hop SIP proxy. That is, the intent of "recipient=endpoint" that if 
a call requires location-based routing in order to succeed, then the 
call should fail.

Personally, I believe (and I think this is a point Ted was trying to 
make) that a UAC must have a way to indicate that a location is to be 
read by the endpoint and no one else. This goes back to RFC 3693 which 
dictates that a target must have a way of articulating privacy rules and 
that using protocols must enforce those rules. In particular, see 
requirements 7, 10 and 11 in RFC 3693. (Note that RFC 3693 explicitly 
makes an exception for the emergency case, and so this discussion is in 
the context of non-emergency conveyance of location information ... e.g. 
Pizza Hut.)

(Also note: there is always the issue that a malicious proxy might not 
obey the wishes expressed by the UAC, but SIP is an architecture in 
which there is implicit trust by the UAC that the proxy acting on his 
behave properly and comply with all relevant specifications. 
Implications of the SIP trust model are a topic for another thread ... 
See for example:  
http://www1.ietf.org/mail-archive/web/sip/current/msg20319.html)

Clearly, there are many mechanisms that satisfy the desideratum that a 
target be able to indicate that its location is to be read only by the 
SIP endpoint. For example, this desire could be encoded as a privacy 
rule within the PIDF-LO and each SIP proxy could parse the privacy rules 
in a PIDF-LO to determine the target's intent. Alternatively, a 
location-by-value could be encrypted end-to-end; or location could be 
conveyed by-reference using an LIS with certificate-based access 
controls. The GEOPRIV working group discussed various mechanisms last 
May (See the thread beginning with: 
http://www1.ietf.org/mail-archive/web/geopriv/current/msg03521.html) and 
I believe there was rough consensus that the "recipient=endpoint" 
mechanism described in the current conveyance draft was the best 
mechanism for achieving the above desideratum.

This seems to leave us with three options going forward:

1) Deny the UAC the opertunity to indicate that location is to be read 
only by the SIP endpoint. (That is, declare that SIP is not a GEOPRIV 
using protocol in sense of RFC 3693).

2) Revisit the mechanism discussion and attempt to reach consensus on a 
better mechanism for indicating that location is to be read only by the 
SIP endpoint.

3) Craft text explaining that when the "recipient=endpoint" parameter is 
used that a compliant SIP proxy is not to 'read' the location 
information. (Note that this text should also indicate that when 
"recipient=endpoint" is used that calls requiring location-based routing 
will fail, and thus should only be used when call failure is preferred 
over disclosure of location information to a routing entity.)

- Matt Lepinski


James M. Polk wrote:

> This also gets back to one of my original points, does SIP expect a 
> UAC to understand the topology of a message's path to the ultimate 
> destination?
>
> Is Ted's intent of the "recipient=endpoint" parameter to prevent 
> proxies from reading location in a message *and* a "recipient=server" 
> parameter to prevent endpoints from reading location in a message?
>
> Does the UAC always know that there are only proxies between it and 
> the destination UAS?
>
> Does the UAC always understand a particular message does or does not 
> need to be routed based on the location within the request?
>
> Emergency services is an example of, always allow proxy routing when 
> the UAC knows this is an emergency request.  But will this be true for 
> all applications of location conveyance in the (relatively near-term) 
> future?  I'm not so sure.
>
> The UAC has a mechanism for making location not readable by proxies if 
> it doesn't want them to, use encryption e2e.  But this has interesting 
> properties in at least one case, the a user calls the nearest Pizza Hut.
>
> A UAC can encrypt its location in the first INVITE, but if Pizza Hut 
> has a national or regional number, that routes on the location of the 
> caller, the message will probably return a 493 (undecipherable).
>
> Does the UAC then send location to PizzaHut.com unencrypted, knowing 
> this is required to get the INVITE to the right store?
>
> There are other usages of this, other than Pizza Hut.
>
> Does anyone have a suggestion for informative text that can address 
> each of these two (or more) situations?
>
> At the moment, all text around "recipient=" is suggestive, and not 
> definitive, because of what Dean says below.
>
> That said, I could put something in like "unless a future standards 
> track RFC says otherwise, the use of "recipient=" parameter within any 
> locationValue is informative in nature", thus leaving the door open 
> for ECRIT's phoneBCP doc to refine usage in the emergency context, as 
> well as any other service defining document to do the same type of 
> refinement.
>
> James
>
> At 08:28 AM 11/26/2007, DRAGE, Keith \(Keith\) wrote:
>
>> This just seems to me to be an inappropriate change of RFC 2119 
>> language.
>>
>> If we really mean either of these, then we should be specifying that 
>> the message is encrypted in the first place.
>>
>> What we probably mean is something informative (because we cannot 
>> make a normative statement on what applications do with the data), 
>> stating that usage of the message so tagged is inappropriate because 
>> the sender did not intend it to be used for this purpose.
>>
>> Regards
>>
>> Keith
>>
>> > -----Original Message-----
>> > From: daniel grotti [mailto:[e-mail]]
>> > Sent: Saturday, November 24, 2007 11:38 AM
>> > To: Dean Willis
>> > Cc: IETF SIP List; James M. Polk
>> > Subject: R: R: R: [Sip] a question about IETF draft location
>> > conveyance 09
>> >
>> > I know.
>> > May be SHOULD NOT instead MUST NOT could be better.
>> >
>> > daniel
>> >
>> >
>> > ----------------------------------
>> >        Daniel  Grotti
>> > D.E.I.S. - University of Bologna
>> > ----------------------------------
>> >        Via Venezia, 52
>> >   47023 Cesena (FC) - ITALY
>> > ----------------------------------
>> > e-mail: [e-mail]
>> > ----------------------------------
>> >
>> >
>> >
>> > -----Messaggio originale-----
>> > Da: Dean Willis [mailto:[e-mail]]
>> > Inviato: sab 24/11/2007 2.32
>> > A: daniel grotti
>> > Cc: Hannes Tschofenig; IETF SIP List; James M. Polk
>> > Oggetto: Re: R: R: [Sip] a question about IETF draft location
>> > conveyance 09
>> >
>> >
>> > On Nov 22, 2007, at 12:08 PM, daniel grotti wrote:
>> >
>> > > Hi all,
>> > > so why don't emphasize this point in the next draft, saying :
>> > > "Proxy server MUST not read messages with "recipient=endpoint"
>> > > paramenter setted".
>> > > This is my point of you.
>> > >
>> > >
>> >
>> >
>> > because from a security standpoint, this prohibition is meaningless.
>> > Intermediate nodes can and will read anything that's in
>> > plaintext, and SOMEBODY will come up with a rationale, in
>> > some context or another, for doing so.
>> >
>> > And has been pointed out, doing so does not appear to create
>> > a compatibility problem. It doesn't break the protocol. It
>> > might defeat security-through-obscurity. It might be rude, or
>> > otherwise socially unacceptable. But those don't qualify for
>> > a MUST level protocol prohibition.
>> >
>> > --
>> > Dean
>> >
>> >
>> >
>> >
>> > _______________________________________________
>> > Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
>> > This list is for NEW development of the core SIP Protocol Use
>> > [e-mail] for questions on current sip
>> > Use [e-mail] for new developments on the application of sip
>> >
>
>
>
> _______________________________________________
> Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
> This list is for NEW development of the core SIP Protocol
> Use [e-mail] for questions on current sip
> Use [e-mail] for new developments on the application of sip
>




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