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Network Working Group                                             Y. NirRequest for Comments: 4478                                   Check PointCategory: Experimental                                        April 2006Repeated Authentication in Internet Key Exchange (IKEv2) ProtocolStatus of This Memo   This memo defines an Experimental Protocol for the Internet   community.  It does not specify an Internet standard of any kind.   Discussion and suggestions for improvement are requested.   Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2006).Abstract   This document extends the Internet Key Exchange (IKEv2) Protocol   document [IKEv2].  With some IPsec peers, particularly in the remote   access scenario, it is desirable to repeat the mutual authentication   periodically.  The purpose of this is to limit the time that security   associations (SAs) can be used by a third party who has gained   control of the IPsec peer.  This document describes a mechanism to   perform this function.1.  Introduction   In several cases, such as the remote access scenario, policy dictates   that the mutual authentication needs to be repeated periodically.   Repeated authentication can usually be achieved by simply repeating   the Initial exchange by whichever side has a stricter policy.   However, in the remote access scenario it is usually up to a human   user to supply the authentication credentials, and often Extensible   Authentication Protocol (EAP) is used for authentication, which makes   it unreasonable or impossible for the remote access gateway to   initiate the IKEv2 exchange.   This document describes a new notification that the original   Responder can send to the original Initiator with the number of   seconds before the authentication needs to be repeated.  The   Initiator SHOULD repeat the Initial exchange before that time is   expired.  If the Initiator fails to do so, the Responder may close   all Security Associations.Nir                           Experimental                      [Page 1]

RFC 4478            Repeated Authentication in IKEv2          April 2006   Repeated authentication is not the same as IKE SA rekeying, and need   not be tied to it.  The key words "MUST", "MUST NOT", "SHOULD",   "SHOULD NOT", and "MAY" in this document are to be interpreted as   described in [RFC2119].2.  Authentication Lifetime   The Responder in an IKEv2 negotiation MAY be configured to limit the   time that an IKE SA and the associated IPsec SAs may be used before   the peer is required to repeat the authentication, through a new   Initial Exchange.   The Responder MUST send this information to the Initiator in an   AUTH_LIFETIME notification either in the last message of an IKE_AUTH   exchange, or in an INFORMATIONAL request, which may be sent at any   time.   When sent as part of the IKE SA setup, the AUTH_LIFETIME notification   is used as follows:      Initiator                            Responder      -------------------------------      -----------------------------      HDR, SAi1, KEi, Ni              -->                                      <--  HDR, SAr1, KEr, Nr, [CERTREQ]      HDR, SK {IDi, [CERT,] [CERTREQ,]         [IDr,] AUTH, SAi2, TSi, TSr} -->                                      <--  HDR, SK {IDr, [CERT,] AUTH,                                                    SAr2, TSi, TSr,                                                     N(AUTH_LIFETIME)}   The separate Informational exchange is formed as follows:                                      <--  HDR, SK {N(AUTH_LIFETIME)}      HDR  SK {}                      -->   The AUTH_LIFETIME notification is described inSection 3.   The original Responder that sends the AUTH_LIFETIME notification   SHOULD send a DELETE notification soon after the end of the lifetime   period, unless the IKE SA is deleted before the lifetime period   elapses.  If the IKE SA is rekeyed, then the time limit applies to   the new SA.   An Initiator that received an AUTH_LIFETIME notification SHOULD   repeat the Initial exchange within the time indicated in the   notification.  The time is measured from the time that the original   Initiator receives the notification.Nir                           Experimental                      [Page 2]

RFC 4478            Repeated Authentication in IKEv2          April 2006   A special case is where the notification is sent in an Informational   exchange, and the lifetime is zero.  In that case, the original   responder SHOULD allow a reasonable time for the repeated   authentication to occur.   The AUTH_LIFETIME notification MUST be protected and MAY be sent by   the original Responder at any time.  If the policy changes, the   original Responder MAY send it again in a new Informational.   The new Initial exchange is not altered.  The initiator SHOULD delete   the old IKE SA within a reasonable time of the new Auth exchange.3.  AUTH_LIFETIME Notification   The AUTH_LIFETIME message is a notification payload formatted as   follows:                           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    !      Notify Message Type      !      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      !                           Lifetime                            !      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      o  Payload Length is 12.      o  Protocol ID (1 octet) MUST be 0.      o  SPI size is 0 (SPI is in message header).      o  Notify Message type is 16403 by IANA.      o  Lifetime is the amount of time (in seconds) left before the         peer should repeat the Initial exchange.  A zero value         signifies that the Initial exchange should begin immediately.         It is usually not reasonable to set this value to less than 300         (5 minutes) since that is too cumbersome for a user.         It is also usually not reasonable to set this value to more         than 86400 (1 day) as that would negate the security benefit of         repeating the authentication.4.  Interoperability with Non-Supporting IKEv2 Implementations   IKEv2 implementations that do not support the AUTH_LIFETIME   notification will ignore it and will not repeat the authentication.   In that case the original Responder will send a Delete notification   for the IKE SA in an Informational exchange.  Such implementations   may be configured manually to repeat the authentication periodically.Nir                           Experimental                      [Page 3]

RFC 4478            Repeated Authentication in IKEv2          April 2006   Non-supporting Responders are not a problem because they will simply   not send these notifications.  In that case, there is no requirement   that the original Initiator re-authenticate.5.  Security Considerations   The AUTH_LIFETIME notification sent by the Responder does not   override any security policy on the Initiator.  In particular, the   Initiator may have a different policy regarding re-authentication,   requiring more frequent re-authentication.  Such an Initiator can   repeat the authentication earlier then is required by the   notification.   An Initiator MAY set reasonable limits on the amount of time in the   AUTH_LIFETIME notification.  For example, an authentication lifetime   of less than 300 seconds from SA initiation may be considered   unreasonable.6.  IANA Considerations   The IANA has assigned a notification payload type for the   AUTH_LIFETIME notifications from the IKEv2 Notify Message Types   registry.7.  Normative References   [IKEv2]    Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",RFC4306, December 2005.   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.Author's Address   Yoav Nir   Check Point Software Technologies   EMail: ynir@checkpoint.comNir                           Experimental                      [Page 4]

RFC 4478            Repeated Authentication in IKEv2          April 2006Full Copyright Statement   Copyright (C) The Internet Society (2006).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   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.Intellectual Property   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 inBCP 78 andBCP 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.Acknowledgement   Funding for the RFC Editor function is provided by the IETF   Administrative Support Activity (IASA).Nir                           Experimental                      [Page 5]