Network Working Group                                             Y. Nir
Internet-Draft                                               Check Point
Intended status: Standards Track                                   Q. Wu
Expires: November 2, 2011                                         Huawei
                                                             May 1, 2011

                 An IKEv2 Extension for Supporting ERP


   This document describes an extension to the IKEv2 protocol that
   allows an IKE Security Association (SA) to be created and
   authenticated using the EAP Re-authentication Protocol extension as
   described in RFC 5296 and its bis document.

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   This Internet-Draft will expire on November 2, 2011.

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1.  Introduction

   IKEv2, as specified in [RFC5996], allows authentication of the
   initiator using an EAP method.  This is described in section 2.16.
   Using EAP significantly increases the count of round-trips required
   to establish the IPsec SA, and also may require user interaction.
   This makes it inconvenient to allow a single remote access client to
   create multiple IPsec tunnels with multiple IPsec gateways that
   belong to the same domain.

   The EAP Re-authentication Protocol (ERP), as descripted in
   [RFC5296bis], allows an EAP peer to authenticate to multiple
   authenticators, while performing the full EAP method only once.
   Subsequent authentications require fewer round-trips and no user

   Bringing these two technologies together allows a remote access IPsec
   client to create multiple tunnels with different gateways that belong
   to a single domain, as well as using the keys from other contexts of
   using EAP, such as network access within the same domain, to
   transparently connect to VPN gateways within this domain.

1.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

2.  Usage Scenarios

   Several scenarios motivated this proposal:
   o  Multiple tunnels for a single remote access VPN client.  Suppose a
      company has offices in New York City, Paris, and Shanghai.  For
      historical reasons, the email server is located in the Paris
      office, while most of the servers hosting the company's intranet
      are located in Shanghai, and the finance department servers are in
      NYC.  An employee using remote access VPN may need to connect to
      servers from all three locations.  While it is possible to connect
      to a single gateway, and have that gateway route the requests to
      the other gateways (perhaps through site-2-site VPN), this is not
      efficient, and it is more desirable to have the client initiate
      three different tunnels.  It is, however, not desirable to have
      the user type in a password three times.
   o  Roaming.  In these days of mobile phones and tablets, users often
      move from the wireless LAN in their office, where access may be
      granted through 802.1x, to a cellular network where VPN is
      necessary and back again.  Both the VPN server and the 802.1x

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      access point are authenticators that connect to the same AAA
      servers.  So it makes sense to make the transition smooth, without
      requiring user interaction.  [SecureBeacon] is an attempt to allow
      detecting whether the client should connect using VPN or not.

3.  Protocol Outline

   Supporting ERX requires an EAP payload in the first IKE_AUTH request.
   This is a deviation from the rules in RFC 5996, so support needs to
   be indicated through a Notify payload in the IKE_SA_INIT response.
   This Notify replaces the EAP-Initiate/Re-auth-Start message of ERX,
   and therefore contains the domain name, as specified in section of [RFC5296bis].

   A supporting initiator that has unexpired keys for this domain will
   send the EAP_Initiate/Re-auth message in an EAP payload in the first
   IKE_AUTH request.

   The responder sends the EAP payload content to a backend AAA server,
   and receives the rMSK and an EAP-Finish/Re-auth message.  If forwards
   that to the initiator in an EAP payload within the first IKE_AUTH

   The initiator then sends an additional IKE_AUTH request, that
   includes the AUTH payload which has been calculated using the rMSK in
   the role of the MSK as described in sections 2.15 and 2.16 or
   [RFC5996].  The responder replies similarly, and the IKE_AUTH
   exchange is finished.

   The following figure is adapted from appendixes C.1 and C.3 of RFC
   5996, with most of the optional payloads removed.  Note that the
   EAP_Initiate/Re-auth message replaces the IDi payload.

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    init request         --> SA, KE, Ni,

    init response       <-- SA, KE, Nr,

    first request       --> EAP(EAP_Initiate/Re-auth),
                            [[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+],
                            SA, TSi, TSr,

    first response      <-- IDr, [CERT+], AUTH,

    last request        --> AUTH

    last response       <-- AUTH,
                            SA, TSi, TSr,

3.1.  Clarification About EAP Codes

   Section 3.16 of [RFC5996] enumerates the EAP codes in EAP messages
   which are carried in EAP payloads.  The enumeration goes only to 4.
   It is not clear whether that list is supposed to be exhaustive or

   To clarify, an implementation supporting this specification MUST
   accept and transmit EAP messages with at least the codes for Initiate
   and Finish (5 and 6).

4.  ERX_SUPPORTED Notification

   The Notify payload is as described in [RFC5996]

                            1                   2                   3
        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
       ! Next Payload  !C!  RESERVED   !         Payload Length        !
       !  Protocol ID  !   SPI Size    !    ERX Notify Message Type    !
       !                            Domain Name                        !

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   o  Protocol ID (1 octet) MUST be 1, as this message is related to an
      IKE SA.
   o  SPI Size (1 octet) MUST be zero, in conformance with section 3.10
      of [RFC5996].
   o  ERX Notify Message Type (2 octets) - MUST be xxxxx, the value
      assigned for ERX.  TBA by IANA.
   o  Domain Name (variable) - contains the domain name or realm, as
      these terms are used in [RFC5296bis].

5.  Security Considerations


6.  IANA Considerations

   IANA is requested to assign a notify message type from the status
   types range (16418-40959) of the "IKEv2 Notify Message Types"
   registry with name "ERX_SUPPORTED".

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

              Wu, W., Cao, Z., Shi, Y., and B. He, "EAP Extensions for
              EAP Re-authentication Protocol (ERP)",
              draft-ietf-hokey-rfc5296bis-02 (work in progress),
              March 2011.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol: IKEv2", RFC 5996,
              September 2010.

7.2.  Informative References

              Sheffer, Y. and Y. Nir, "Secure Beacon: Securely Detecting
              a Trusted Network", draft-sheffer-ipsecme-secure-beacon
              (work in progress), June 2009.

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Authors' Addresses

   Yoav Nir
   Check Point Software Technologies Ltd.
   5 Hasolelim st.
   Tel Aviv  67897


   Q. Wu
   Huawei Technologies Co., Ltd.
   101 Software Avenue, Yuhua District
   Nanjing, JiangSu  210012


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