RFC 5580
Carrying Location Objects in RADIUS and Diameter
5. Table of Attributes
The following table provides a guide to which attributes may be found in which RADIUS messages, and in what quantity.
Request Accept Reject Challenge Accounting # Attribute Request 0-1 0-1 0 0 0+ 126 Operator-Name 0+ 0 0 0 0+ 127 Location-Information 0+ 0 0 0 0+ 128 Location-Data 0-1 0-1 0-1 0-1 0-1 129 Basic-Location- Policy-Rules 0-1 0-1 0-1 0-1 0-1 130 Extended-Location- Policy-Rules 0-1 0 0 0 0 131 Location-Capable 0 0-1 0 0-1 0 132 Requested-Location-Info 0 0 0-1 0 0 101 Error-Cause (*) (*) Note: The Error-Cause Attribute contains the value for the 'Location-Info-Required' error. Change-of-Authorization Messages Request ACK NAK # Attribute 0-1 0 0 129 Basic-Location-Policy-Rules 0-1 0 0 130 Extended-Location-Policy-Rules 0-1 0 0 132 Requested-Location-Info Legend: 0 This attribute MUST NOT be present. 0+ Zero or more instances of this attribute MAY be present. 0-1 Zero or one instance of this attribute MAY be present. 1 Exactly one instance of this attribute MUST be present. 1+ One or more of these attributes MUST be present. Figure 7: Table of Attributes The Error-Cause Attribute is defined in [RFC5176]. The Location-Information and the Location-Data Attribute MAY appear more than once. For example, if the server asks for civic and geospatial location information, two Location-Information Attributes need to be sent. The attributes defined in this document are not used in any messages other than the ones listed in Figure 7. IANA allocated a new value (509) from the Error-Cause registry with the semantics of 'Location-Info-Required'.
6. Diameter RADIUS Interoperability
When used in Diameter, the attributes defined in this specification can be used as Diameter attribute-value pairs (AVPs) from the code space 1-255 (RADIUS attribute-compatibility space). No additional Diameter code values are therefore allocated. The data types and flag rules, as defined in [RFC3588], for the Diameter AVPs are as follows: +---------------------+ | AVP Flag rules | +----+-----+------+-----+----+ | | |SHOULD| MUST| | Attribute Name Value Type |MUST| MAY | NOT | NOT|Encr| +---------------------------------+----+-----+------+-----+----+ |Operator-Name OctetString| | P | | V,M | Y | |Location-Information OctetString| | P | | V,M | Y | |Location-Data OctetString| | P | | V,M | Y | |Basic-Location- | | | | | | | Policy-Rules OctetString| | P | | V,M | Y | |Extended-Location- | | | | | | | Policy-Rules OctetString| | P | | V,M | Y | |Requested- | | | | | | | Location-Info OctetString| | P | | V,M | Y | |Location-Capable OctetString| | P | | V,M | Y | +---------------------------------+----+-----+------+-----+----+ The RADIUS attributes in this specification have no special translation requirements for Diameter-to-RADIUS or RADIUS-to-Diameter gateways; they are copied as is, except for changes relating to headers, alignment, and padding. See also Section 4.1 of [RFC3588] and Section 9 of [RFC4005]. What this specification says about the applicability of the attributes for RADIUS Access-Request packets applies in Diameter to AA-Request [RFC4005] or Diameter-EAP-Request [RFC4072]. What is said about Access-Challenge applies in Diameter to AA-Answer [RFC4005] or Diameter-EAP-Answer [RFC4072] with the Result-Code AVP set to DIAMETER_MULTI_ROUND_AUTH. What is said about Access-Accept applies in Diameter to AA-Answer or Diameter-EAP-Answer messages that indicate success. Similarly, what is said about RADIUS Access-Reject packets applies in Diameter to AA-Answer or Diameter-EAP-Answer messages that indicate failure. What is said about CoA-Request applies in Diameter to Re-Auth-Request [RFC4005].
What is said about Accounting-Request applies in Diameter to Accounting-Request [RFC4005] as well. Note that these AVPs may be used by Diameter applications other than RFC 4005 [RFC4005] and RFC 4072 [RFC4072]. The above-mentioned applications are, however, likely to be relevant in the context of this document.7. Security Considerations
A number of security aspects are relevant for the distribution of location information via RADIUS. These aspects are discussed in separate subsections.7.1. Communication Security
Requirements for the protection of a Location Object are defined in [RFC3693] -- namely, mutual end-point authentication, data object integrity, data object confidentiality, and replay protection. If no authentication, integrity, and replay protection between the participating RADIUS entities is provided, then adversaries can spoof and modify transmitted attributes. Two security mechanisms are proposed for RADIUS: o [RFC2865] proposes the usage of a static key that raised concerns regarding the lack of dynamic key management. At the time of writing, work is ongoing to address some shortcomings of the [RFC2865] attribute regarding security protection. o RADIUS over IPsec [RFC3579] enables the use of standard key- management mechanisms, such as Kerberized Internet Negotiation of Keys (KINK), the Internet Key Exchange Protocol (IKE), and IKEv2 [RFC4306], to establish IPsec security associations. Confidentiality protection MUST be used to prevent an eavesdropper from gaining access to location information. Confidentiality protection is already present for other reasons in many environments, such as for the transport of keying material in the context of Extensible Authentication Protocol (EAP) authentication and authorization. Hence, this requirement is, in many environments, already fulfilled. Mutual authentication MUST be provided between neighboring RADIUS entities to prevent man-in- the-middle attacks. Since mutual authentication is already required for key transport within RADIUS messages, it does not represent a deployment obstacle. Since IPsec protection is already suggested as a mechanism to protect RADIUS, no additional considerations need to be addressed beyond those described in [RFC3579].
In case IPsec protection is not available for some reason and RADIUS- specific security mechanisms have to be used, then the following considerations apply. The Access-Request message is not integrity protected. This would allow an adversary to change the contents of the Location Object or to insert, modify, and delete attributes or individual fields. To address these problems, the Message- Authenticator (80) can be used to integrity protect the entire Access-Request packet. The Message-Authenticator (80) is also required when EAP is used and, hence, is supported by many modern RADIUS servers. Access-Request packets including location attribute(s) without a Message-Authenticator (80) Attribute SHOULD be silently discarded by the RADIUS server. A RADIUS server supporting location attributes MUST calculate the correct value of the Message-Authenticator (80) and MUST silently discard the packet if it does not match the value sent. Access-Accept messages, including location attribute(s), without a Message-Authenticator (80) Attribute SHOULD be silently discarded by the NAS. An NAS supporting location attributes MUST calculate the correct value of a received Message-Authenticator (80) and MUST silently discard the packet if it does not match the value sent. RADIUS and Diameter make some assumptions about the trust between traversed RADIUS entities in the sense that object-level security is not provided by either RADIUS or Diameter. Hence, some trust has to be placed on the RADIUS entities to behave according to the defined rules. Furthermore, the RADIUS protocol does not involve the user in their protocol interaction except for tunneling authentication information (such as EAP messages) through their infrastructure. RADIUS and Diameter have even become a de facto protocol for key distribution for network-access authentication applications. Hence, in the past there were some concerns about the trust placed into the infrastructure -- particularly from the security area -- when it comes to keying. The EAP keying infrastructure is described in [RFC4282].7.2. Privacy Considerations
This section discusses privacy implications for the distribution of location information within RADIUS. Note also that it is possible for the RADIUS server to obtain some amount of location information from the NAS identifier. This document, however, describes procedures to convey more accurate location information about the end host and/or the network. In a number of deployment environments, location information about the network also reveals the current
location of the user with a certain degree of precision, depending on
the location-determination mechanism used, the update frequency, the
size of the network, and other factors, such as movement traces.
Three types of use cases have to be differentiated:
o The RADIUS server does not want to receive location information
from the RADIUS client.
o In case there is an out-of-band agreement between the entity
responsible for the NAS and the entity operating the RADIUS
server, location information may be sent without an explicit
request from the RADIUS server.
o The RADIUS server dynamically requests location information from
the NAS.
7.2.1. RADIUS Client
The RADIUS client MUST behave according to the following guidelines:
o If neither an out-of-band agreement exists nor location
information is requested by the RADIUS server, then location
information is not disclosed by the RADIUS client.
o The RADIUS client MUST pass location information to other entities
(e.g., when information is written to a local database or to the
log files) only together with the policy rules. The entity
receiving the location information (together with the policies)
MUST follow the guidance given with these rules.
o A RADIUS client MUST include Basic-Location-Policy-Rules and
Extended-Location-Policy-Rules Attributes that are configured
within an Access-Request packet.
o NAS implementations supporting this specification, which are
configured to provide location information, MUST echo Basic-
Location-Policy-Rules and Extended-Location-Policy-Rules
Attributes unmodified within a subsequent Access-Request packet.
In addition, an Access-Request packet sent with a Service-Type
value of "Authorize Only" MUST include the Basic-Location-Policy-
Rules or Extended-Location-Policy-Rules Attributes that were
received in a previous Access-Accept if the FUTURE_REQUESTS flag
was set in the Requested-Location-Info Attribute.
7.2.2. RADIUS Server
The RADIUS server is a natural place for storing authorization policies since the user typically has some sort of trust relationship with the entity operating the RADIUS server. Once the infrastructure is deployed and location-aware applications are available, there might be a strong desire to use location information for other purposes as well. The Common Policy framework [RFC4745] that was extended for geolocation privacy [GEO-POLICY] is tailored for this purpose. The Extensible Markup Language (XML) Configuration Access Protocol (XCAP) [RFC4825] gives users the ability to change their privacy policies using a standardized protocol. These policies are an important tool for limiting further distribution of the user's location to other location-based services. The RADIUS server MUST behave according to the following guidelines: o The RADIUS server MUST attach available rules to the Access- Accept, Access-Reject, or Access-Challenge message when the RADIUS client is supposed to provide location information. o When location information is made available to other entities (e.g., writing to stable storage for later billing processing), then the RADIUS server MUST attach the privacy rules to location information.7.2.3. RADIUS Proxy
A RADIUS proxy, behaving as a combined RADIUS client and RADIUS server, MUST follow the rules described in Sections 7.2.1 and 7.2.2.7.3. Identity Information and Location Information
For the envisioned usage scenarios, the identity of the user and his device is tightly coupled to the transfer of location information. If the identity can be determined by the visited network or RADIUS brokers, then it is possible to correlate location information with a particular user. As such, it allows the visited network and brokers to learn the movement patterns of users. The user's identity can be "leaked" to the visited network or RADIUS brokers in a number of ways: o The user's device may employ a fixed Media Access Control (MAC) address or base its IP address on such an address. This enables the correlation of the particular device to its different
locations. Techniques exist to avoid the use of an IP address
that is based on a MAC address [RFC4941]. Some link layers make
it possible to avoid MAC addresses or change them dynamically.
o Network-access authentication procedures, such as the PPP
Challenge Handshake Authentication Protocol (CHAP) [RFC1994] or
EAP [RFC4187], may reveal the user's identity as a part of the
authentication procedure. Techniques exist to avoid this problem
in EAP methods, for instance by employing private Network Access
Identifiers (NAIs) [RFC4282] in the EAP Identity Response message
and by method-specific private identity exchanges in the EAP
method (e.g., [RFC4187], [RFC5281], [PEAP], and [RFC5106]).
Support for identity privacy within CHAP is not available.
o RADIUS may return information from the home network to the visited
one in a manner that makes it possible to either identify the user
or at least correlate his session with other sessions, such as the
use of static data in a Class Attribute [RFC2865] or in some
accounting attribute usage scenarios [RFC4372].
o Mobility protocols may reveal some long-term identifier, such as a
home address.
o Application-layer protocols may reveal other permanent
identifiers.
To prevent the correlation of identities with location information,
it is necessary to prevent leakage of identity information from all
sources, not just one.
Unfortunately, most users are not educated about the importance of
identity confidentiality, and some protocols lack support for
identity-privacy mechanisms. This problem is made worse by the fact
that users may be unable to choose particular protocols, as the
choice is often dictated by the type of network operator they use,
the type of network they wish to access, the kind of equipment they
have, or the type of authentication method they are using.
A scenario where the user is attached to the home network is, from a
privacy point of view, simpler than a scenario where a user roams
into a visited network, since the NAS and the home RADIUS server are
in the same administrative domain. No direct relationship between
the visited and the home network operator may be available, and some
RADIUS brokers need to be consulted. With subscription-based network
access as used today, the user has a contractual relationship with
the home network provider that could (theoretically) allow higher
privacy considerations to be applied (including policy rules stored at the home network itself, for the purpose of restricting further distribution). In many cases it is necessary to secure the transport of location information along the RADIUS infrastructure. Mechanisms to achieve this functionality are discussed in Section 7.1.8. IANA Considerations
The Attribute Types and Attribute Values defined in this document have been registered by the Internet Assigned Numbers Authority (IANA) from the RADIUS namespaces as described in the "IANA Considerations" section of RFC 3575 [RFC3575], in accordance with BCP 26 [RFC5226]. Additionally, the Attribute Type has been registered in the Diameter namespace. For RADIUS attributes and registries created by this document, IANA placed them in the Radius Types registry. This document defines the following attributes: Operator-Name Location-Information Location-Data Basic-Location-Policy-Rules Extended-Location-Policy-Rules Location-Capable Requested-Location-Info Please refer to Section 5 for the registered list of numbers. IANA has also assigned a new value (509) for the Error-Cause Attribute [RFC5176] of "Location-Info-Required" according to this document. Additionally, IANA created the following new registries listed in the subsections below.8.1. New Registry: Operator Namespace Identifier
This document also defines an Operator Namespace Identifier registry (used in the Namespace ID field of the Operator-Name Attribute). Note that this document requests IANA only to maintain a registry of existing namespaces for use in this identifier field, and not to establish any namespaces or place any values within namespaces.
IANA added the following values to the Operator Namespace Identifier registry using a numerical identifier (allocated in sequence), a token for the operator namespace, and a contact person for the registry. +----------+--------------------+------------------------------------+ |Identifier| Operator Namespace | Contact Person | | | Token | | +----------+--------------------+------------------------------------+ | 0x30 | TADIG | TD.13 Coordinator | | | | (td13@gsm.org) | | 0x31 | REALM | IETF O&M Area Directors | | | | (ops-ads@ietf.org) | | 0x32 | E212 | ITU Director | | | | (tsbdir@itu.int) | | 0x33 | ICC | ITU Director | | | | (tsbdir@itu.int) | +----------+--------------------+------------------------------------+ Note that the above identifier values represent the ASCII value '0' (decimal 48 or hex 0x30), '1' (decimal 49, or hex 0x31), '2' (decimal 50, or hex 0x32), and '3' (decimal 51, or hex 0x33). This encoding was chosen to simplify parsing. Requests to IANA for a new value for a Namespace ID, i.e., values from 0x34 to 0xFE, will be approved by Expert Review. A designated expert will be appointed by the IESG. The Expert Reviewer should ensure that a new entry is indeed required or could fit within an existing database, e.g., whether there is a real requirement to provide a token for a Namespace ID because one is already up and running, or whether the REALM identifier plus the name should be recommended to the requester. In addition, the Expert Reviewer should ascertain to some reasonable degree of diligence that a new entry is a correct reference to an operator namespace whenever a new one is registered.8.2. New Registry: Location Profiles
Section 4.2 defines the Location-Information Attribute and a Code field that contains an 8-bit integer value. Two values, zero and one, are defined in this document, namely: Value (0): Civic location profile described in Section 4.3.1 Value (1): Geospatial location profile described in Section 4.3.2 The remaining values are reserved for future use.
Following the policies outlined in [RFC3575], the available bits with a description of their semantics will be assigned after the Expert Review process. Updates can be provided based on expert approval only. Based on expert approval, it is possible to mark entries as "deprecated". A designated expert will be appointed by the IESG. Each registration must include the value and the corresponding semantics of the defined location profile.8.3. New Registry: Location-Capable Attribute
Section 4.6 defines the Location-Capable Attribute that contains a bit map. 32 bits are available, from which 4 bits are defined by this document. This document creates a new IANA registry for the Location-Capable Attribute. IANA added the following values to this registry: +----------+----------------------+ | Value | Capability Token | +----------+----------------------+ | 1 | CIVIC_LOCATION | | 2 | GEO_LOCATION | | 4 | USERS_LOCATION | | 8 | NAS_LOCATION | +----------+----------------------+ Following the policies outlined in [RFC3575], the available bits with a description of their semantics will be assigned after the Expert Review process. Updates can be provided based on expert approval only. Based on expert approval, it is possible to mark entries as "deprecated". A designated expert will be appointed by the IESG. Each registration must include: Name: Capability Token (i.e., an identifier of the capability) Description: Brief description indicating the meaning of the 'info' element. Numerical Value: A numerical value that is placed into the Capability Attribute representing a bit in the bit-string of the Requested-Location- Info Attribute.
8.4. New Registry: Entity Types
Section 4.2 defines the Location-Information Attribute that contains an 8-bit Entity field. Two values are registered by this document, namely: Value (0) describes the location of the user's client device. Value (1) describes the location of the RADIUS client. All other values are reserved for future use. Following the policies outlined in [RFC3575], the available bits with a description of their semantics will be assigned after the Expert Review process. Updates can be provided based on expert approval only. Based on expert approval, it is possible to mark entries as "deprecated". A designated expert will be appointed by the IESG. Each registration must include the value and a corresponding description.8.5. New Registry: Privacy Flags
Section 4.4 defines the Basic-Location-Policy-Rules Attribute that contains flags indicating privacy settings. 16 bits are available, from which a single bit, bit (0), indicating 'retransmission allowed' is defined by this document. Bits 1-15 are reserved for future use. Following the policies outline in [RFC3575], the available bits with a description of their semantics will be assigned after the Expert Review process. Updates can be provided based on expert approval only. Based on expert approval, it is possible to mark entries as "deprecated". A designated expert will be appointed by the IESG. Each registration must include the bit position and the semantics of the bit.8.6. New Registry: Requested-Location-Info Attribute
Section 4.7 defines the Requested-Location-Info Attribute that contains a bit map. 32 bits are available, from which 6 bits are defined by this document. This document creates a new IANA registry for the Requested-Location-Info Attribute. IANA added the following values to this registry:
+----------+----------------------+
| Value | Capability Token |
+----------+----------------------+
| 1 | CIVIC_LOCATION |
| 2 | GEO_LOCATION |
| 4 | USERS_LOCATION |
| 8 | NAS_LOCATION |
| 16 | FUTURE_REQUESTS |
| 32 | NONE |
+----------+----------------------+
The semantics of these values are defined in Section 4.7.
Following the policies outlined in [RFC3575], new Capability Tokens,
with a description of their semantics for usage with the Requested-
Location-Info Attribute, will be assigned after the Expert Review
process. Updates can be provided based on expert approval only.
Based on expert approval, it is possible to mark entries as
"deprecated". A designated expert will be appointed by the IESG.
Each registration must include:
Name:
Capability Token (i.e., an identifier of the capability)
Description:
Brief description indicating the meaning of the 'info' element.
Numerical Value:
A numerical value that is placed into the Capability Attribute
representing a bit in the bit-string of the Requested-Location-
Info Attribute.
9. Acknowledgments
The authors would like to thank the following people for their help
with an initial version of this document and for their input: Chuck
Black, Paul Congdon, Jouni Korhonen, Sami Ala-luukko, Farooq Bari, Ed
Van Horne, Mark Grayson, Jukka Tuomi, Jorge Cuellar, and Christian
Guenther.
Henning Schulzrinne provided the civic location information content found in this document. The geospatial location-information format is based on work done by James Polk, John Schnizlein, and Marc Linsner. The authorization policy format is based on the work done by Jon Peterson. The authors would like to thank Victor Lortz, Anthony Leibovitz, Jose Puthenkulam, Bernrad Aboba, Jari Arkko, Parviz Yegani, Serge Manning, Kuntal Chowdury, Pasi Eronen, Blair Bullock and Eugene Chang for their feedback to an initial version of this document. We would like to thank Jari Arkko for his textual contributions. Lionel Morand provided detailed feedback on numerous issues. His comments helped to improve the quality of this document. Jouni Korhonen, Victor Fajardo, Tolga Asveren, and John Loughney helped us with the Diameter RADIUS interoperability section. Andreas Pashalidis reviewed a later version document and provided a number of comments. Alan DeKok, Lionel Morand, Jouni Korhonen, David Nelson, and Emile van Bergen provided guidance on the Requested-Location-Info Attribute and participated in the capability-exchange discussions. Allison Mankin, Jouni Korhonen, and Pasi Eronen provided text for the Operator Namespace Identifier registry. Jouni Korhonen interacted with the GSMA to find a contact person for the TADIG operator namespace, and Scott Bradner consulted the ITU-T to find a contact person for the E212 and the ICC operator namespace. This document is based on the discussions within the IETF GEOPRIV Working Group. Therefore, the authors thank Henning Schulzrinne, James Polk, John Morris, Allison Mankin, Randall Gellens, Andrew Newton, Ted Hardie, and Jon Peterson for their time discussing a number of issues with us. We thank Stephen Hayes for aligning this work with 3GPP activities. We would like to thank members of the Wimax Forum Global Roaming Working Group (GRWG) for their feedback on the Operator-Name attribute. Ray Jong Kiem helped us with his detailed description to correct the document. The RADEXT Working Group chairs, David Nelson and Bernard Aboba, provided several draft reviews and we would like to thank them for the help and their patience. Finally, we would like to thank Dan Romascanu, Glen Zorn, Russ Housley, Jari Arkko, Ralph Droms, Adrial Farrel, Tim Polk, and Lars Eggert for the IETF Last Call comments; Derek Atkins for his security area directorate review; and Yoshiko Chong for spotting a bug in the IANA Considerations section.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000. [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode for Internationalized Domain Names in Applications (IDNA)", RFC 3492, March 2003. [RFC3575] Aboba, B., "IANA Considerations for RADIUS (Remote Authentication Dial In User Service)", RFC 3575, July 2003. [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko, "Diameter Base Protocol", RFC 3588, September 2003. [RFC3825] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host Configuration Protocol Option for Coordinate-based Location Configuration Information", RFC 3825, July 2004. [RFC4776] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option for Civic Addresses Configuration Information", RFC 4776, November 2006. [RFC5176] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B. Aboba, "Dynamic Authorization Extensions to Remote Authentication Dial In User Service (RADIUS)", RFC 5176, January 2008. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.10.2. Informative References
[GEO-POLICY] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J., and J. Polk, "Geolocation Policy: A Document Format for Expressing Privacy Preferences for Location Information", Work in Progress, February 2009.
[GMLv3] "Open Geography Markup Language (GML) Implementation Specification", OGC 02-023r4, January 2003, <http://www.opengis.org/techno/implementation.htm>. [GSM] "TADIG Naming Conventions", Version 4.1, GSM Association Official Document TD.13, June 2006. [ISO] "Codes for the representation of names of countries and their subdivisions - Part 1: Country codes", ISO 3166-1, 1997. [ITU1400] "Designations for interconnections among operators' networks", ITU-T Recommendation M.1400, January 2004. [ITU212] "The international identification plan for mobile terminals and mobile users", ITU-T Recommendation E.212, May 2004. [PEAP] Josefsson, S., Palekar, A., Simon, D., and G. Zorn, "Protected EAP Protocol (PEAP) Version 2", Work in Progress, October 2004. [RFC1305] Mills, D., "Network Time Protocol (Version 3) Specification, Implementation", RFC 1305, March 1992. [RFC1994] Simpson, W., "PPP Challenge Handshake Authentication Protocol (CHAP)", RFC 1994, August 1996. [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. [RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication Dial In User Service) Support For Extensible Authentication Protocol (EAP)", RFC 3579, September 2003. [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J. Polk, "Geopriv Requirements", RFC 3693, February 2004. [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, "Diameter Network Access Server Application", RFC 4005, August 2005. [RFC4017] Stanley, D., Walker, J., and B. Aboba, "Extensible Authentication Protocol (EAP) Method Requirements for Wireless LANs", RFC 4017, March 2005.
[RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible Authentication Protocol (EAP) Application", RFC 4072, August 2005. [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object Format", RFC 4119, December 2005. [RFC4187] Arkko, J. and H. Haverinen, "Extensible Authentication Protocol Method for 3rd Generation Authentication and Key Agreement (EAP-AKA)", RFC 4187, January 2006. [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The Network Access Identifier", RFC 4282, December 2005. [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [RFC4372] Adrangi, F., Lior, A., Korhonen, J., and J. Loughney, "Chargeable User Identity", RFC 4372, January 2006. [RFC4745] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J., Polk, J., and J. Rosenberg, "Common Policy: A Document Format for Expressing Privacy Preferences", RFC 4745, February 2007. [RFC4825] Rosenberg, J., "The Extensible Markup Language (XML) Configuration Access Protocol (XCAP)", RFC 4825, May 2007. [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 4941, September 2007. [RFC5106] Tschofenig, H., Kroeselberg, D., Pashalidis, A., Ohba, Y., and F. Bersani, "The Extensible Authentication Protocol-Internet Key Exchange Protocol version 2 (EAP- IKEv2) Method", RFC 5106, February 2008. [RFC5281] Funk, P. and S. Blake-Wilson, "Extensible Authentication Protocol Tunneled Transport Layer Security Authenticated Protocol Version 0 (EAP- TTLSv0)", RFC 5281, August 2008.
Appendix A. Matching with GEOPRIV Requirements
This section compares the requirements for a GEOPRIV using protocol, described in [RFC3693], against the approach of distributing Location Objects with RADIUS. In Appendices A.1 and A.2, we discuss privacy implications when RADIUS entities make location information available to other parties. In Appendix A.3, the requirements are matched against these two scenarios.A.1. Distribution of Location Information at the User's Home Network
When location information is conveyed from the RADIUS client to the RADIUS server, then it might subsequently be made available for different purposes. This section discusses the privacy implications for making location information available to other entities. To use a more generic scenario, we assume that the visited RADIUS and the home RADIUS server belong to different administrative domains. The Location Recipient obtains location information about a particular Target via protocols specified outside the scope of this document (e.g., SIP, HTTP, or an API). The subsequent figure shows the interacting entities graphically. visited network | home network | | +----------+ | | Rule | | | Holder | | +----+-----+ | | | rule|interface +----------+ | V +----------+ |Location | | +----------+ notification |Location | |Generator | | |Location |<------------->|Recipient | +----------+ publication |Server | interface | | |RADIUS |<------------->+----------+ +----------+ |Client | interface |RADIUS | E.g., SIP/HTTP +----------+ | |Server | | +----------+ E.g., NAS RADIUS | | Figure 8: Location Server at the Home Network
The term 'Rule Holder' in Figure 8 denotes the entity that creates the authorization ruleset.A.2. Distribution of Location Information at the Visited Network
This section describes a scenario where location information is made available to Location Recipients by a Location Server in the visited network. Some identifier needs to be used as an index within the location database. One possible identifier is the Network Access Identifier. RFC 4282 [RFC4282] and RFC 4372 [RFC4372] provide background regarding whether entities in the visited network can obtain the user's NAI in cleartext. The visited network provides location information to a Location Recipient (e.g., via SIP or HTTP). This document enables the NAS to obtain the user's privacy policy via the interaction with the RADIUS server. Otherwise, only default policies, which are very restrictive, are available. This allows the Location Server in the visited network to ensure they act according to the user's policies. The subsequent figure shows the interacting entities graphically.
visited network | home network | +----------+ | |Location | | |Recipient | | | | | +----------+ | ^ | +----------+ | | | Rule | notification | | Holder | interface | | | | | +----+-----+ | | | | | rule|interface v | | +----------+ | | |Location | | v |Server | | +----------+ +----------+ Rule Transport|RADIUS | |RADIUS |<------------->|Server | |Client | RADIUS +----------+ +----------+ | |Location | | |Generator | +----------+ Figure 9: Location Server at the Visited Network Location information always travels with privacy policies. This document enables the RADIUS client to obtain these policies. The Location Server can subsequently act according to these policies to provide access control using the Extended-Location-Policy-Rules and to adhere to the privacy statements in the Basic-Location-Policy- Rules.A.3. Requirements Matching
Section 7.1 of [RFC3693] details the requirements of a "Location Object". We discuss these requirements in the subsequent list. Req. 1. (Location Object generalities): * Regarding requirement 1.1, the syntax and semantics of the Location Object are taken from [RFC3825] and [RFC4776]. It is furthermore possible to convert it to the format used in the Geography Markup Language (GMLv3) [GMLv3], as used with PIDF-LO [RFC4119].
* Regarding requirement 1.2, a number of fields in the civic
location-information format are optional.
* Regarding requirement 1.3, the inclusion of type of place item
(CAtype 29) used in the DHCP civic format gives a further
classification of the location. This attribute can be seen as
an extension.
* Regarding requirement 1.4, this document does not define the
format of the location information.
* Regarding requirement 1.5, location information is only sent
from the RADIUS client to the RADIUS server.
* Regarding requirement 1.6, the Location Object contains both
location information and privacy rules. Location information
is described in Sections 4.2, 4.3.1, and 4.3.2. The
corresponding privacy rules are detailed in Sections 4.4 and
4.5.
* Regarding requirement 1.7, the Location Object is usable in a
variety of protocols. The format of the object is reused from
other documents, as detailed in Sections 4.2, 4.3.1, 4.3.2,
4.4, and 4.5.
* Regarding requirement 1.8, the encoding of the Location Object
has an emphasis on a lightweight encoding format to be used
with RADIUS.
Req. 2. (Location Object fields):
* Regarding requirement 2.1, the target identifier is carried
within the network-access authentication protocol (e.g., within
the EAP-Identity Response when EAP is used and/or within the
EAP method itself). As described in Section 7.2 of this
document, it has a number of advantages if this identifier is
not carried in clear. This is possible with certain EAP
methods whereby the identity in the EAP-Identity Response only
contains information relevant for routing the response to the
user's home network. The user identity is protected by the
authentication and key exchange protocol.
* Regarding requirement 2.2, the Location Recipient is, in the
main scenario, the home RADIUS server. For a scenario where
the Location Recipient is obtaining location information from
the Location Server via HTTP or SIP, the respective mechanisms
defined in these protocols are used to identify the recipient.
The Location Generator cannot, a priori, know the recipients if
they are not defined in this protocol.
* Regarding requirement 2.3, the credentials of the Location
Recipient are known to the RADIUS entities based on the
security mechanisms defined in the RADIUS protocol itself.
Section 7 of this document describes these security mechanisms
offered by the RADIUS protocol. The same is true for
requirement 2.4.
* Regarding requirement 2.5, Sections 4.2, 4.3.1, and 4.3.2
describe the content of the Location fields. Since the
location format itself is not defined in this document, motion
and direction vectors as listed in requirement 2.6 are not
defined.
* Regarding requirement 2.6, this document provides the
capability for the RADIUS server to indicate what type of
location information it would like to see from the RADIUS
client.
* Regarding requirement 2.7, timing information is provided with
the 'Sighting Time' and 'Time-to-Live' fields defined in
Section 4.2.
* Regarding requirement 2.8, a reference to an external (more
detailed ruleset) is provided with the Extended-Location-
Policy-Rules Attribute in Section 4.5.
* Regarding requirement 2.9, security headers and trailers are
provided as part of the RADIUS protocol or even as part of
IPsec.
* Regarding requirement 2.10, a version number in RADIUS is
provided with the IANA registration of the attributes. New
attributes are assigned a new IANA number.
Req. 3. (Location Data Types):
* Regarding requirement 3.1, this document reuses civic and
geospatial location information as described in Sections 4.3.2
and 4.3.1.
* With the support of civic and geospatial location information,
support of requirement 3.2 is fulfilled.
* Regarding requirement 3.3, the geospatial location information
used by this document only refers to absolute coordinates.
However, the granularity of the location information can be
reduced with the help of the AltRes, LoRes, and LaRes fields
described in [RFC3825].
* Regarding requirement 3.4, further Location Data Types can be
added via new coordinate reference systems (CRSs -- see the
Datum field in [RFC3825]) and via extensions to [RFC3825] and
[RFC4776].
Section 7.2 of [RFC3693] details the requirements of a "using
protocol". These requirements are listed below.
Req. 4.: The using protocol has to obey the privacy and security
instructions coded in the Location Object (LO) regarding the
transmission and storage of the LO. This document requires that
entities that aim to make location information available to third
parties be required to obey the privacy instructions.
Req. 5.: The using protocol will typically facilitate that the keys
associated with the credentials are transported to the respective
parties, that is, key establishment is the responsibility of the
using protocol. Section 7 of this document specifies how security
mechanisms are used in RADIUS and how they can be reused to
provide security protection for the Location Object.
Additionally, the privacy considerations (see Section 7.2) are
also relevant for this requirement.
Req. 6. (Single Message Transfer): In particular, for tracking of
small target devices, the design should allow a single message/
packet transmission of location as a complete transaction. The
encoding of the Location Object is specifically tailored towards
the inclusion into a single message that even respects the (Path)
MTU size.
Section 7.3 of [RFC3693] details the requirements of a "Rule-based
Location Data Transfer". These requirements are listed below.
Req. 7. (LS Rules): With the scenario shown in Figure 8, the
decision of a Location Server to provide a Location Recipient
access to location information is based on Rule Maker-defined
privacy rules that are stored at the home network. With regard to
the scenario shown in Figure 9, the Rule Maker-defined privacy
rules are sent from the RADIUS server to the NAS (see Sections
4.4, 4.5, and 7.2 for more details).
Req. 8. (LG Rules): For all usage scenarios, it is possible to
consider the privacy rule before transmitting location information
from the NAS to the RADIUS server or even to third parties. In
the case of an out-of-band agreement between the owner of the NAS
and the owner of the RADIUS server, privacy might be applied on a
higher granularity. For the scenario shown in Figure 8, the
visited network is already in possession of the user's location
information prior to the authentication and authorization of the
user. A correlation between the location and the user identity
might, however, still not be possible for the visited network (as
explained in Section 7.2). A Location Server in the visited
network has to evaluate available rulesets.
Req. 9. (Viewer Rules): The Rule Maker might define (via mechanisms
outside the scope of this document) which policy rules are
disclosed to other entities.
Req. 10. (Full Rule language): GEOPRIV has defined a rule language
capable of expressing a wide range of privacy rules that is
applicable in the area of the distribution of Location Objects. A
basic ruleset is provided with the Basic-Location-Policy-Rules
Attribute (Section 4.4). A reference to the extended ruleset is
carried in Section 4.5. The format of these rules is described in
[RFC4745] and [GEO-POLICY].
Req. 11. (Limited Rule language): A limited (or basic) ruleset is
provided by the Policy-Information Attribute in Section 4.4 (and
as introduced with PIDF-LO [RFC4119]).
Section 7.4 of [RFC3693] details the requirements of a "Location
Object Privacy and Security". These requirements are listed below.
Req. 12 (Identity Protection): Support for unlinkable pseudonyms is
provided by the usage of a corresponding authentication and key-
exchange protocol. Such protocols are available, for example,
with the support of EAP as network-access authentication methods.
Some EAP methods support passive user-identity confidentiality,
whereas others even support active user-identity confidentiality.
This issue is further discussed in Section 7. The importance for
user-identity confidentiality and identity protection has already
been recognized as an important property (see, for example, a
document on EAP method requirements for wireless LANs [RFC4017]).
Req. 13. (Credential Requirements): As described in Section 7 ,
RADIUS signaling messages can be protected with IPsec. This
allows a number of authentication and key exchange protocols to be
used as part of IKE, IKEv2, or KINK.
Req. 14. (Security Features): GEOPRIV defines a few security
requirements for the protection of Location Objects, such as
mutual end-point authentication, data object integrity, data
object confidentiality, and replay protection. As described in
Section 7, these requirements are fulfilled with the usage of
IPsec if mutual authentication refers to the RADIUS entities
(acting as various GEOPRIV entities) that directly communicate
with each other.
Req. 15. (Minimal Crypto): A minimum of security mechanisms are
mandated by the usage of RADIUS. Communication security for
Location Objects between RADIUS infrastructure elements is
provided by the RADIUS protocol (including IPsec and its dynamic
key-management framework), rather than relying on object security
via S/SIME (which is not available with RADIUS).
Authors' Addresses
Hannes Tschofenig (editor) Nokia Siemens Networks Linnoitustie 6 Espoo 02600 Finland Phone: +358 (50) 4871445 EMail: Hannes.Tschofenig@gmx.net URI: http://www.tschofenig.priv.at Farid Adrangi Intel Corporatation 2111 N.E. 25th Avenue Hillsboro OR USA EMail: farid.adrangi@intel.com Mark Jones Bridgewater Systems Corporation 303 Terry Fox Drive Ottawa, Ontario K2K 3J1 CANADA EMail: mark.jones@bridgewatersystems.com Avi Lior Bridgewater Systems Corporation 303 Terry Fox Drive Ottawa, Ontario K2K 3J1 CANADA EMail: avi@bridgewatersystems.com Bernard Aboba Microsoft Corporation One Microsoft Way Redmond, WA 98052 USA EMail: bernarda@microsoft.com