GEOPRIV H. Schulzrinne Internet-Draft Columbia U. Expires: December 20, 2006 June 18, 2006 RELO: Retrieving End System Location Information draft-schulzrinne-geopriv-relo-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 20, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract In some network configurations, it is desirable for the end system to be able to obtain its geodetic or civic location using an application-layer protocol. This document describes RELO; a simple, HTTP-based stateless protocol that fulfills this need. Schulzrinne Expires December 20, 2006 [Page 1] Internet-Draft RELO June 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1 Discovery . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2 Query . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3 Response . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. XML Schema Definition . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.1 Normative References . . . . . . . . . . . . . . . . . . . 10 8.2 Informative References . . . . . . . . . . . . . . . . . . 11 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . 12 Schulzrinne Expires December 20, 2006 [Page 2] Internet-Draft RELO June 2006 1. Introduction The RELO protocol allows end systems (devices) to obtain information about their current geodetic (longitude, latitude) or civic (jurisdictional or postal street address) location, based on their Internet Protocol address or possibly other identifiers. The protocol uses HTTP [3] to retrieve the information. The location information can be returned by value or by reference, either for retrieval or for event notification by subscription. The protocol is motivated by the requirement that end user network- layer equipment, such as DSL modems, routers, NATs and wireless access points, cannot be modified. Hence, a DHCP or PPP based solution cannot be reused. A more detailed problem statement is provided in [11]. To reduce privacy risks, RELO is designed for "first-party" retrieval, i.e., the device obtains its own location or a reference thereto. It is not designed for a third party to retrieve location information about a device. However, RELO may retrieve a reference to location information that can be passed to third parties. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT","RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [1]. This document reuses terminology introduced by RFC 3693 [6] and [11]. 3. Overview This section describes the Location Information Server (LIS) discovery procedure (see Section 3.1), the query message (see Section 3.2) and the response message (see Section 3.3). 3.1 Discovery The URI for the location server is conveyed via DNS (S-NAPTR) [8]. The domain is determined from the domain name of the end host, typically conveyed as part of the configuration information or obtainable from the public IP address via DNS PTR records. dhcp-17.example.com. ; order pref flags service regexp IN NAPTR 50 50 "a" "Location.relo" "" ; replacement relo.example.org Schulzrinne Expires December 20, 2006 [Page 3] Internet-Draft RELO June 2006 3.2 Query The query is transmitted to the server in an HTTP GET request, using the media type application/relo+xml. The use of TLS [10] is RECOMMENDED. The end system is identified by default by its IP address, contained in the IP packets carrying the HTTP request. If the querier is behind a NAT or firewall, the server will see the querier's public IP address and use that address to identify the end system. In those cases, the location of the network termination equipment, such as the DSL modem or 802.11 access point, will be returned, not the actual location of the querier since the LIS generally has no way to estimate that location. Other identifiers, such as switch and port information, are for further study. The format of the location information is contained in the element of the query and can indicate that either civic or geo(spatial) information is desired and whether the client wishes to obtain the value ("value"), a reference to the current value ("reference") or a subscription to change notifications for the value ("events"). A query example is shown below: This protocol does not provide the ability for the end host to transmit a location estimate as, for example, obtained from a local GPS receiver, to the LIS. 3.3 Response A successful response contains the civic and or geospatial location information related to the identifier of the querier. Note that this proposal does not return a PIDF-LO [12] since most of the values carried by the PIDF-LO cannot be meaningfully instantiated by the network without the help of the end host. This proposal allows the end host to instantiate the values byself without introducing security challenges and privacy risks. If the querier indicated a preference for location-by-reference, the answer simply contains a URI-list, i.e., media type text/uri-list [2]. Normal HTTP status responses are used to indicate failure conditions, e.g., when the information is unavailable. Schulzrinne Expires December 20, 2006 [Page 4] Internet-Draft RELO June 2006 The server indicates the validity period of the information using the HTTP Expires header field. If a reference is returned, the reference URL itself is not guaranteed to be valid beyond the expiration time. The server MAY provide one or more URLs in a new HTTP header field, Subscribe, that the client can subscribe to if it wants to receive updates for the object retrieved via HTTP. At least one of the URLs MUST be a SIP URL. For SIP, the event name to be used in the subscription can be encoded in the URL. (An HTTP header field was chosen since the subscription mechanism does not depend on the media type and also applies to media types that would make it difficult to embed such subscription URLs, such as a JPEG image.) The server makes no guarantees that the client has the appropriate credentials to subscribe to the object. Clients MAY support this mechanism; all clients that do support subscriptions MUST support the SIP SUBSCRIBE and NOTIFY methods. The field value consists of one or more absolute URIs: Subcribe = "Subscribe" ":" 1#absoluteURI An example is: Subscribe: sip:data@example.com?Event=location [TBD: Since this mechanism is not limited to location delivery, this might be better separated into a stand-alone draft.] The response containing the location information is not signed. Response message examples are shown below starting with a response providing geospatial location information and followed by civic location information. Finally, we show an example with location-by- referency. 37:46:30N 122:25:10W Schulzrinne Expires December 20, 2006 [Page 5] Internet-Draft RELO June 2006 Deutschland Bayern Muenchen Neu Perlach 96 81675 sip:15555551002adfkafjyonqoijoyukjglky@example.com 4. XML Schema Definition This section provides the XML schema. Schulzrinne Expires December 20, 2006 [Page 6] Internet-Draft RELO June 2006 5. IANA Considerations This document registers the label "RELO" as the S-NAPTR application service tag according to [8] for location lookup services and defines the intended usage, interoperability considerations and security considerations (Section 6). This document requests the registration of a new message header field, 'Subscribe', according to RFC 3864 [7]. Schulzrinne Expires December 20, 2006 [Page 7] Internet-Draft RELO June 2006 Header field name: Subscribe This specification also requests the registration of a new MIME type according to the procedures of RFC 4288 [9] and guidelines in RFC 3023 [4]. MIME media type name: application MIME subtype name: relo+xml Mandatory parameters: none Optional parameters: charset Indicates the character encoding of enclosed XML. Encoding considerations: Uses XML, which can employ 8-bit characters, depending on the character encoding used. See RFC 3023 [4], Section 3.2. Security considerations: This content type is designed to carry authorization policies. Appropriate precautions should be adopted to limit disclosure of this information. Please refer to Section 6 of RFCXXXX [NOTE TO IANA/RFC-EDITOR: Please replace XXXX with the RFC number of this specification.] and to the security considerations described in Section 10 of RFC 3023 [4] for more information. Interoperability considerations: None Published specification: RFCXXXX [NOTE TO IANA/RFC-EDITOR: Please replace XXXX with the RFC number of this specification.] this document Applications which use this media type: Presence- and location-based systems Additional information: Magic Number: None Schulzrinne Expires December 20, 2006 [Page 8] Internet-Draft RELO June 2006 File Extension: .reloxml Macintosh file type code: 'TEXT' Personal and email address for further information: Henning Schulzrinne, hgs@cs.columbia.edu Intended usage: LIMITED USE Author/Change controller: This specification is a work item of the IETF GEOPRIV working group, with mailing list address . 6. Security Considerations If IP addresses are used as identifiers, RELO relies on return routability to ensure that only the current owner of an IP address can obtain location information for that host, and assumes that an attacker cannot generate and intercept packets for a spoofed IP address. Note that TLS itself does not prevent client address spoofing if the attacker can intercept and generate IP packets with the victim's IP address. The victim can be protected against this privacy breach if the client and LIS share a secret, such as a username/password combination, and the LIS can associate an IP address with a particular user, e.g., based on PPP authentication. In that case, HTTP digest authentication can be used to prevent a third party from using a spoofed IP address to fraudulently obtain location information. Unfortunately, such authentication information is not generally available to wireless nodes in residential networks, for example. To prevent others from accessing location information for a particular host, the reference to a Location Object MUST NOT be guessable. For example, it may contain a random component. It is RECOMMENDED to use TLS with confidentiality protection to prevent eavesdroppers to observe the protocol exchange between the end host and the LIS. Signing of location information is beyond the scope of this document [TBD; if desired, reference to other document, since this is not specific to obtaining location information]. Thus, colluding attackers may be able to obtain and replay location information that does not correspond to their true location. Schulzrinne Expires December 20, 2006 [Page 9] Internet-Draft RELO June 2006 7. Acknowledgments This document is based on discussions with Hannes Tschofenig and inspired by protocols such as HELD. 8. References 8.1 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Mealling, M. and R. Daniel, "URI Resolution Services Necessary for URN Resolution", RFC 2483, January 1999. [3] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [4] Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types", RFC 3023, January 2001. [5] Eastlake, D., Reagle, J., and D. Solo, "(Extensible Markup Language) XML-Signature Syntax and Processing", RFC 3275, March 2002. [6] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. Polk, "Geopriv Requirements", RFC 3693, February 2004. [7] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004. [8] Daigle, L. and A. Newton, "Domain-Based Application Service Location Using SRV RRs and the Dynamic Delegation Discovery Service (DDDS)", RFC 3958, January 2005. [9] Freed, N. and J. Klensin, "Media Type Specifications and Registration Procedures", BCP 13, RFC 4288, December 2005. [10] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. [11] Tschofenig, H. and H. Schulzrinne, "Problem Statement, Requirements and Framework for a Geopriv Layer 7 Protocol", Internet-Draft to-be-published, May 2006. Schulzrinne Expires December 20, 2006 [Page 10] Internet-Draft RELO June 2006 8.2 Informative References [12] Peterson, J., "A Presence-based GEOPRIV Location Object Format", RFC 4119, December 2005. Author's Address Henning Schulzrinne Columbia University Department of Computer Science 450 Computer Science Building New York, NY 10027 US Phone: +1 212 939 7004 Email: hgs+geopriv@cs.columbia.edu URI: http://www.cs.columbia.edu Schulzrinne Expires December 20, 2006 [Page 11] Internet-Draft RELO June 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Schulzrinne Expires December 20, 2006 [Page 12]