PANA Working Group                                               Y. Ohba
Internet-Draft                                                   Toshiba
Intended status: Standards Track                          April 13,                           June 28, 2009
Expires: October 15, December 30, 2009

                  Pre-authentication Support for PANA
                       draft-ietf-pana-preauth-05
                       draft-ietf-pana-preauth-06

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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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Specification of Requirements . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Pre-authentication Procedure  . . . . . . . . . . . . . . . . . 4
   4.  PANA Extensions . . . . . . . . . . . . . . . . . . . . . . . . 7
   5.  Backward Compatibility  . . . . . . . . . . . . . . . . . . . . 8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 9
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9

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 through to which the host gains
      access to the Internet/intranet. 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.

   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 and a CPAA to discover each
   other.  However, such mechanisms are out of  For example, IEEE 802.21 [802.21] Information Service and
   Command Service can be used for the scope of this
   document. PaC to discover the CPAA and the
   CPAA to discover the PaC, respectively.

   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 may be initiated by both a PaC and a CPAA. CPAA 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  When a CPAA initiates pre-authentication, it sends a PAR message
      with the 'S' (Start) and 'E' (prE-authentication) bits set.  The
      PaC responds with a PANA-Auth-Answer (PAN) 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 PAN 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
      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 PaC-initiated pre-authentication and PAA-
   initiated pre-authentication are shown in Figure 1 and Figure 2,
   respectively.  Note that EAP authentication is performed over PAR and
   PAN exchanges.

        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: PaC-initiated Pre-authentication Call Flow
        PaC                                               CPAA
         |                                                 |
         |                                        +------------------+
         |                                        |Pre-authentication|
         |                                        |trigger           |
         |                                        +------------------+
         |            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 2: PAA-initiated 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|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   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.

   Similarly, when a PAA that supports the pre-authentication extension
   initiates PANA pre-authentication by sending a PAR message with the
   'E' (prE-authentication) bit set to a PaC that does not support the
   pre-authentication extension, the PaC will ignore the E-bit, and try
   to process the message as a normal authentication attempt.  As a
   result, the PAA will receive a PAN message with the 'E' (prE-
   authentication) bit cleared.

   In both cases, 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

   Since the mechanism described in this document is designed to work
   across multiple access networks, an access network may be configured
   to allow or disallow PANA messages from a set of access networks.

   When pre-authentication is initiated by CPAA, it is possible that
   multiple CPAAs simultaneously initiate pre-authentication for the
   same PaC.  In order to avoid possible resource consumption attacks on
   the PaC caused by an attacker initiating pre-authentication for the
   PaC by changing source addresses, the PaC SHOULD limit the maximum
   number of CPAAs allowed to communicate.

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 Alper Yegin, 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]
              Wu, W. and Y.
              Ohba, "EAP Pre-authentication Y. and G. Zorn, "Extensible Authentication Protocol
              (EAP) Early Authentication Problem  Statement", draft-ietf-hokey-preauth-ps-06
              draft-ietf-hokey-preauth-ps-08 (work in progress), March
              June 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.

Author's Address

   Yoshihiro Ohba
   Toshiba America Research, Inc.
   1 Telcordia Drive
   Piscateway, NJ  08854
   USA

   Phone: +1 732 699 5305
   Email: yohba@tari.toshiba.com