PANA Working Group Y. Ohba Internet-Draft Toshiba Intended status: Experimental A. Yegin Expires: June 17, 2010 Samsung December 14, 2009 Pre-authentication Support for PANA draft-ietf-pana-preauth-08 Abstract This document defines an extension to the Protocol for carrying Authentication for Network Access (PANA) for proactively establishing a PANA security association between a PANA client in one access network and a PANA authentication agent in another access network to which the PANA client may move. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 June 17, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents Ohba & Yegin Expires June 17, 2010 [Page 1] Internet-Draft Pre-authentication Support for PANA December 2009 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Specification of Requirements . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Pre-authentication Procedure . . . . . . . . . . . . . . . . . 4 4. PANA Extensions . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Backward Compatibility . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Ohba & Yegin Expires June 17, 2010 [Page 2] Internet-Draft Pre-authentication Support for PANA December 2009 1. Introduction The Protocol for carrying Authentication for Network Access (PANA) [RFC5191] carries EAP messages between a PaC (PANA Client) and a PAA (PANA Authentication Agent) in the access network. If the PaC is a mobile device and is capable of moving from one access network to another while running its applications, it is critical for the PaC to perform a handover seamlessly without degrading the performance of the applications during the handover period. When the handover requires the PaC to establish a PANA session with the PAA in the new access network, the signaling to establish the PANA session should be completed as fast as possible. See [I-D.ietf-hokey-preauth-ps] for the handover latency requirements. This document defines an extension to the PANA protocol [RFC5191] used for proactively executing EAP authentication and establishing a PANA SA (Security Association) between a PaC in an access network and a PAA in another access network to which the PaC may move. The extension to the PANA protocol is designed to realize direct pre- authentication defined in [I-D.ietf-hokey-preauth-ps]. How to realize authorization and accounting with the use of the pre- authentication extension is out of the scope of this document. 1.1. Specification of Requirements 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. Terminology The following terms are used in this document in addition to the terms defined in [RFC5191]. Serving Network: The access network to which the host is currently attached. Candidate Network: An access network that is a potential target of host's handover. Serving PAA (SPAA): A PAA that resides in the serving network and provides network access authentication for a particular PaC. Ohba & Yegin Expires June 17, 2010 [Page 3] Internet-Draft Pre-authentication Support for PANA December 2009 Candidate PAA (CPAA): A PAA that resides in a candidate network to which the PaC may move. A CPAA for a particular PaC may be a SPAA for another PaC. Pre-authentication: Pre-authentication refers to EAP pre- authentication and defined as the utilization of EAP to pre- establish EAP keying material on an authenticator prior to arrival of the peer at the access network served by that authenticator [I-D.ietf-hokey-preauth-ps]. In this draft, EAP pre- authentication is performed between a PaC and a CPAA. 3. Pre-authentication Procedure A PaC that supports pre-authentication may establish a PANA session for each CPAA. There may be several mechanisms for a PaC to discover a CPAA. An IP address of the discovered CPAA is the output of those mechanisms. PANA pre-authentication is performed between the PaC and CPAA using the discovered IP address of the CPAA. IEEE 802.21 [802.21] Information Service MAY be used as a CPAA discovery mechanism. There may be a number of criteria for CPAA selection, the timing to start pre-authentication and the timing as to when the CPAA becomes the SPAA. Such criteria can be implementation specific and thus are outside the scope of this document. Pre-authentication is initiated by a PaC in a similar way as normal authentication. A new 'E' (prE-authentication) bit is defined in the PANA header. When pre-authentication is performed, the 'E' (prE- authentication) bit of PANA messages is set in order to indicate that this PANA run is for pre-authentication. Use of pre-authentication is negotiated as follows. o When a PaC initiates pre-authentication, it sends a PANA-Client- Initiation (PCI) message with the 'E' (prE-authentication) bit set. The CPAA responds with a PANA-Auth-Request (PAR) message with the 'S' (Start) and 'E' (prE-authentication) bits set only if it supports pre-authentication. Otherwise, the 'E' (prE- authentication) bit of the PAR message will be cleared according to Section 6.2 of [RFC5191], which results in a negotiation failure. o Once the PaC and CPAA have successfully negotiated on performing pre-authentication using the 'S' (Start) and 'E' (prE- authentication) bits, the subsequent PANA messages exchanged between them MUST have the 'E' (prE-authentication) bit set until Ohba & Yegin Expires June 17, 2010 [Page 4] Internet-Draft Pre-authentication Support for PANA December 2009 CPAA becomes SPAA of the PaC. The PaC may conduct this exchange with more than one CPAA. If the PaC and CPAA have failed to negotiate on performing pre-authentication, the PaC or CPAA that sent a message with both the 'S' (Start) and 'E' (prE- authentication) bits set MUST discard the message received from the peer with 'S' (Start) bit set and the 'E' (prE-authentication) bit cleared, which will eventually result in PANA session termination. When a CPAA of the PaC becomes the SPAA due to, e.g., movement of the PaC, the PaC informs the PAA of the change using PANA-Notification- Request (PNR) and PANA-Notification-Answer (PNA) messages with the 'P' (Ping) bit set and the 'E' (prE-authentication) bit cleared. The 'E' (prE-authentication) bit MUST be cleared in subsequent PANA messages. The PANA session between the PaC and a CPAA is deleted by entering the termination phase of the PANA protocol. Example call flows for pre-authentication is shown in Figure 1. Note that EAP authentication is performed over PAR and PAN exchanges. Ohba & Yegin Expires June 17, 2010 [Page 5] Internet-Draft Pre-authentication Support for PANA December 2009 PaC CPAA | | +------------------+ | |Pre-authentication| | |trigger | | +------------------+ | | PCI w/'E' bit set | |------------------------------------------------>| | PAR w/'S' and 'E' bits set | |<------------------------------------------------| | PAN w/'S' and 'E' bits set | |------------------------------------------------>| | PAR-PAN exchange w/'E' bit set | |<----------------------------------------------->| | PAR w/'C' and 'E' bits set | |<------------------------------------------------| | PAN w/'C' and 'E' bits set | |------------------------------------------------>| . . . . . . +----------+ | | Movement | | +----------+ | | PNR w/ 'P' bit set and w/o 'E' bit set | |------------------------------------------------>| | +-----------------+ | |CPAA becomes SPAA| | +-----------------+ | PNA w/ 'P' bit set and w/o 'E' bit set | |<------------------------------------------------| | | Figure 1: Pre-authentication Call Flow 4. PANA Extensions A new 'E' (prE-authentication) bit is defined in Flags field of PANA header as follows. 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R S C A P I E r r r r r r r r r| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Ohba & Yegin Expires June 17, 2010 [Page 6] Internet-Draft Pre-authentication Support for PANA December 2009 E(PrE-authentication) When pre-authentication is performed, the 'E' (prE-authentication) bit of PANA messages is set in order to indicate whether this PANA run is for pre-authentication. The exact usage of this bit is described in Section 3. This bit is to be assigned by IANA. 5. Backward Compatibility Backward compatibility between a PANA entity that does not support the pre-authentication extension and another PANA entity that supports the pre-authentication extension is maintained as follows. When a PaC that supports the pre-authentication extension initiates PANA pre-authentication by sending a PCI message with the 'E' (prE- authentication) bit set to a PAA that does not support the pre- authentication extension, the PAA will ignore the E-bit according to Section 6.2 of [RFC5191], and try to process the message as a normal authentication attempt. As a result, the PaC will receive a PAR message with the 'E' (prE-authentication) bit cleared. In this case, the negotiation on the use of pre-authentication will fail and eventually the PANA session will be terminated as described in Section Section 3. 6. Security Considerations This specification is based on the PANA protocol and it exhibits the same security properties, except for one important difference: Pre- authenticating PaCs are not physically connected to an access network associated with the PAA, but they are connected to some other network somewhere else on the Internet. This distinction can create greater DoS vulnerability for systems using PANA pre-authentication if appropriate measures are not taken. An unprotected PAA can be forced to create state by an attacker PaC which merely sends PCI messages. It is recommended that the authorized PaCs are limited to well-known IP networks for a given PAA. A white-list of IP subnets can be implemented either on the firewall protecting the perimeter around the PAA, or on the PAA itself. That way not every host on the Internet can launch a DoS attack on the PAA. This prevention measure SHOULD be used whenever it can be practically applied to a given deployment. Furthermore, [RFC5191] describes how PAA can stay stateless while responding to incoming PCIs. PAAs using pre-authentication SHOULD be following those guidelines (see [RFC5191] Section 4.1). Ohba & Yegin Expires June 17, 2010 [Page 7] Internet-Draft Pre-authentication Support for PANA December 2009 7. IANA Considerations As described in Section 4, bit 6 of the Flags field of the PANA Header needs to be assigned by IANA for the 'E' (prE-authentication) bit. 8. Acknowledgments The author would like to thank Basavaraj Patil, Ashutosh Dutta, Julien Bournelle, Sasikanth Bharadwaj, Subir Das, Rafa Marin Lopez, Lionel Morand, Victor Fajardo, Glen Zorn and Qin Wu for their support and valuable feedback. 9. References 9.1. Normative References [RFC5191] Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A. Yegin, "Protocol for Carrying Authentication for Network Access (PANA)", RFC 5191, May 2008. 9.2. Informative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [I-D.ietf-hokey-preauth-ps] Ohba, Y., Wu, W., and G. Zorn, "Extensible Authentication Protocol (EAP) Early Authentication Problem Statement", draft-ietf-hokey-preauth-ps-10 (work in progress), December 2009. [802.21] IEEE, "Standard for Local and Metropolitan Area Networks: Media Independent Handover Services", LAN MAN Standards Committee of the IEEE Computer Society 802.21 2008. Ohba & Yegin Expires June 17, 2010 [Page 8] Internet-Draft Pre-authentication Support for PANA December 2009 Authors' Addresses Yoshihiro Ohba Toshiba Corporate Research and Development Center 1 Komukai-Toshiba-cho Saiwai-ku, Kawasaki, Kanagawa 212-8582 Japan Phone: +81 44 549 2230 Email: yoshihiro.ohba@toshiba.co.jp Alper Yegin Samsung Istanbul Turkey Email: alper.yegin@yegin.org Ohba & Yegin Expires June 17, 2010 [Page 9]