Network Working Group Farid Adrangi INTERNET DRAFT Intel Corporation Category: Informational (or standards?) Avi Lior Expires: Feb 27, 2005 Bridgewater Systems Jouni Korhonen Teliasonera Sept 27, 2004 Chargeable User Identity draft-adrangi-radius-chargeable-user-identity-01.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. 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 become aware will be disclosed, in accordance with RFC 3668. 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. Copyright Notice Copyright (C) The Internet Society (2004). Abstract This document describes a new RADIUS attribute used by a home RADIUS to indicate Chargeable User Identity to all parties involved in the roaming transaction outside the home network. Table of Contents 1. Introduction...................................................2 Adrangi, et al. Expires Feb 27, 2005 [Page 1] Internet Draft RADIUS Chargeable User Identity 27 Sept 2004 1.1 Requirements language..........................................3 2. Operation.......................................................3 2.1 Chargeable User Identity Attribute.............................3 3. Diameter RADIUS Interoperability................................6 4. IANA Considerations.............................................6 5. Security Considerations.........................................6 6. Acknowledgements................................................6 7. References......................................................6 AuthorsÆ Addresses.................................................7 1. Introduction In certain authentication methods such as, EAP-PEAP or EAP-TTLS, EAP-SIM, and EAP-AKA, the true identity of the subscriber can be hidden from the RADIUS AAA servers outside the subscriberÆs home network. In these methods the User-Name(1) attribute contains an anonymous identity (e.g., @example.com) sufficient to route the RADIUS packets to the home network but otherwise insufficient to identify the subscriber. While this mechanism is good practice there could be problems. Because Local and intermediate networks may require a user identity in order to enforce usage policies. For example, local or intermediate networks may wish to implement a limit on simultaneous sessions, and/or may require a billable user identity in order to demonstrate willingness to pay and limit the potential for fraud. This basically implies that a unique identity known by the home network needs to be conveyed to all parties involved in the roaming transaction for correlating the authentication and accounting packets. Providing a unique identity to intermediaries is therefore a requirement to fulfill certain business needs. This fulfillment need not undermine the need to protect the anonymity of the user. The mechanism provided by this draft allows the home operator to meet these business requirements by providing a temporal identity representing the subscriber and at the same time protecting the anonymity of the subscriber. Standard RADIUS Class(25) or User-Name(1) attributes could be used to indicate the CUI. However, in a complex global roaming environment where there could be one or more intermediary between the NAS and the home RADIUS server, the use of aforementioned attributes could lead to problems as described below. O On use of RADIUS Class (25) attribute, [1] states ôThis Attribute is available to be sent by the server to the client in an Access-Accept and SHOULD be sent unmodified by the client to the accounting server as part of the Accounting-Request Adrangi, et al. Expires February 27, 2005 [Page 2] Internet Draft RADIUS Chargeable User Identity 27 Sept 2004 packet if accounting is supported. The client MUST NOT interpret the attribute locally.ö So RADIUS clients MUST NOT interpret the Class attribute, which precludes determining whether it contains a chargeable identity. O On use of RADIUS UserName(1), the home network could use UserName(1) in the Access Accept message to convey the chargeable user identity to intermediaries and the NAS. However, as the Access-Accept packet is routed to the NAS, the UserName(1) attribute could be (completely) rewritten by an intermediary and therefore the NAS or other intermediaries along the way will not have access to the CUI. Furthermore, the NAS may use the original value of the UserName attribute ( the one sent in the Access-Request packet) in the Accounting- Request packets. In this case, intermediaries will not have access to the CUI. The Chargeable User Identity (CUI) attribute provides a solution to the above problem and avoids overloading the use of current RADIUS attributes (e.g., UserName(1) re-write). When the home network assigns a value to the CUI it asserts that this value represents a user in the home network. The assertion should be temporary. Long enough to be useful for the external applications and not too long to such that it can be used to identify the user. 1.1 Requirements language In this document, several words are used to signify the requirements of the specification. These words are often capitalized. 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 [RFC2119]. 2. Operation This document assumes that the RADIUS protocol operates as specified in [1, 2] and the Diameter protocol as specified in[RFC 3588, NASREQ]. 2.1 Chargeable User Identity Attribute This attribute serves as an alias to the userÆs identity. It is assigned by the home RADIUS server and MAY be sent in Access- Accept message. The NAS or the access network AAA server MUST include this attribute in the Accounting Requests (Start, Interim, and Stop) messages if it was included in the Access Accept message. Entities (e.g., NASes, proxies) outside the home network MUST NOT modify the Chargeable User Identity attribute. Adrangi, et al. Expires February 27, 2005 [Page 3] Internet Draft RADIUS Chargeable User Identity 27 Sept 2004 In cases where the home RADIUS server cannot determine the NAS support for CUI attribute, it MUST send both the UserName (1) attribute and CUI attribute, with the understanding that if the NAS supports the CUI attribute the CUI attribute will override the identity portion the UserName (1) attribute. That is, the UserName(1) attribute will be used for routing and the CUI attribute will be used for identity purposes. If the RADIUS server includes this attribute in an Access-Accept message it MAY also use this attribute as one of the identity attributes in a Disconnect Message and Change of Authorization message defined by [4]. A summary of the RADIUS Chargeable User Identity Attribute is given below. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | String... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Name Chargeable User Identity Type To be assigned by IANA Length >= 6 String The string identifies the CUI of the end-user and is of type UTF8String. It consists of two colon separated parts. The first part determines the Chargeable-User-Identity type and the second part is the actual Chargeable-User-Identity value. The Chargeable-User-Identity type is coded as two octet string. The Chargeable-User-Identity value must be at least one octet. The following User-Identity types have been defined: 00 û E.164 number The identifier is in international E.164 format (e.g. MSISDN, according to the ITU-T E.164 numbering plan as defined in [6] and [7]). 01 û IMSI Adrangi, et al. Expires February 27, 2005 [Page 4] Internet Draft RADIUS Chargeable User Identity 27 Sept 2004 The is in international IMSI format according to the ITU-T E.212 numbering plan as defined in [8] and [9]). 02 û SIP URL The identifier is in the form of a SIP URI as defined (as defined in [10]). 03 û NAI The identifier is in the form of a Network Access Identifier as defined in [5]. 04 û Opaque string Opaque string is a value that is assigned to the user by the home network in an unspecified format. where the home network asserts that this value represents a particular user û itÆs a handle to the user. 05 û reserved The length of time for which the Chargeable User Identity is valid is unspecified by this specification and typically would be long enough to serve some business needs and short enough such that it minimizes the chance of revealing the true identity of the user (either directly or indirectly). Below are examples of Chargeable User Identity strings with NAI and E.164 Charging Types: ö02:charging-id@realm.orgö ö03:+4689761234ö ö05:charging-idö Ideally, the real user identity should not be revealed through this attribute. However, the operators will have the final word on the used charging type and its identifier. The following table provides a guide to which attribute(s) may be found in which kinds of packets, and in what quantity. Request Accept Reject Challenge Accounting # Attribute Request 0 0-1 0 0 0-1 TBD Chargeable User ID [Note 1] If the Access Accept contains Chargeable-User-Identity then the NAS MUST include the Chargeable-User-Identity in Accounting Requests (Start, Interim and Stop) packets. Change of Authorization and Disconnect-Request Request ACK NAK # Attribute 0-1 0 0 TBD Chargeable User Adrangi, et al. Expires February 27, 2005 [Page 5] Internet Draft RADIUS Chargeable User Identity 27 Sept 2004 [Note 2] Where Chargeable-User-Identity attribute is included in Disconnect-Request or CoA-Request messages, it is used for session identification purposes only. This attribute MUST NOT be used for purposes other than identification (e.g. within CoA-Request messages to request authorization changes). 3. Diameter RADIUS Interoperability In deployments where both RADIUS clients talking with Diameter Servers or Diameter Client talking with RADIUS server then a translation agent will be deployed and operate in accordance to the NASREQ specification. A counterpart Diameter AVP with a similar content to Chargeable-User-Identity is Diameter Credit- Control ApplicationÆs Subscription-ID AVP [11]. 4. IANA Considerations This document requires the assignment of a new RADIUS attribute number for the Chargeable User Identity attribute. 5. Security Considerations The Chargeable-User-Identity attribute must be protected against Man-in-the-Middle attacks. The Chargeable-User-Identity appears in Access-Accept and Accounting Requests packets and is protected by the mechanisms that are defined for RADIUS [1] and [2]. Therefore there are no additional security considerations beyond those already identified in [1] and [2]. Message-Authenticator (80) and Event-Timestamp can be used to further protect against Man-in-the-middle attacks. In this document we require that entities outside the home network not modify the value of this attribute yet there are no provisions for protecting against or detecting that a RADIUS Proxy has modified the attribute. 6. Acknowledgements The authors would like to thank Jari Arkko (of Ericsson), Bernard Aboba (of Microsoft), Blair Bullock (of iPass), Sami Ala-luukko (of Teliasonera), Eugene Chang (of Funk), Mark Grayson (of Cisco), David Mariblanca for their feedback and guidance. 7. References [1] Rigney, C., Rubens, A., Simpson, W. and S. Willens, "Remote Authentication Dial In User Server (RADIUS)", RFC 2865, June 2000. Adrangi, et al. Expires February 27, 2005 [Page 6] Internet Draft RADIUS Chargeable User Identity 27 Sept 2004 [2] Rigney, C., "RADIUS Accounting", RFC 2866, June 2000. [3] Rigney, C., Willats, W., Calhoun, P., "RADIUS Extensions", RFC 2869, June 2000. [4] Chiba, M., Dommety, G., Eklud, M., Mitton, D., Aboba, B., öDynamic Authorization Extensions to Remote Authentication Dial In User Service (RADIUS)ö, RFC 3576, July 2003. [5] Aboba, B., Beadles, M., Arkko, J. and P. Eronen, "The Network Access Identifier", draft-arkko-roamops-rfc2486bis-02 (work in progress), July 2004. [6] Recommendation E.164/I.331 (05/97): The International Public Telecommunication Numbering Plan. 1997. [7] Complement to ITU-T Recommendation E.164 (05/1997):"List of ITU-T Recommendation E.164 assigned country codes", June 2000. [8] Recommendation E.212 (11/98): The international identification plan for mobile terminals and mobile users. 1998. [9] Complement to ITU-T Recommendation E.212 (11/1997):" List of mobile country or geographical area codes ", February 1999. [10] M. Handley, H. Schulzrinne, E. Schooler, J. Rosenberg, G. Camarillo, A. Johnston, J. Peterson, R. Sparks "SIP: Session Initiation Protocol", RFC 3261. June 2002. [11] Hakala, H., Mattila, L., Koskinen, J.-P., Stura M., and Loughney J., "Diameter Credit-Control Application", draft- ietf-aaa-diameter-cc-06.txt (work in progress), September 2004. AuthorsÆ Addresses Farid Adrangi Intel Corporation 2111 N.E. 25th Avenue Hillsboro OR USA Phone: 503-712-1791 Email: farid.adrangi@intel.com Avi Lior Bridgewater Systems Corporation Adrangi, et al. Expires February 27, 2005 [Page 7] Internet Draft RADIUS Chargeable User Identity 27 Sept 2004 303 Terry Fox Drive Suite 100 Ottawa, Ontario K2K 3J1 Canada Phone: 613-591-9104 ;x 6417 Email: avi@bridgewatersystems.com Jouni Korhonen Teliasonera Corporation Phone: +358405344455 Email: jouni.korhonen@teliasonera.com 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. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. 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 Adrangi, et al. Expires February 27, 2005 [Page 8] Internet Draft RADIUS Chargeable User Identity 27 Sept 2004 Copyright (C) The Internet Society (2004). 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. Adrangi, et al. Expires February 27, 2005 [Page 9]