INTERNET DRAFT Yoav Nir draft-nir-ikev2-auth-lt-00.txt Check Point Expires: October 2004 Intended status: Informational May 11, 2004 Repeated Authentication in IKEv2 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Abstract 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 an IKE SA can be used by a third party who has gained control of the IPsec peer. This is not the same as IKE SA rekeying. At the end of the IKE_AUTH negotiation, the Responder sends a notification to the Initiator with the number of seconds before the authentication needs to be repeated. The Initiator will repeat the Initial exchange before that time is expired. 1. Introduction This document extends the IKEv2 document [IKEv2]. It describes the authentication lifetime notification and its processing. 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. Nir [Page 1]
INTERNET-DRAFT Repeated Authentication in IKEv2 April 2004 The Informational exchange follows the IKE_AUTH exchange, and is formed 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} <-- HDR, SK {N(AUTH_LIFETIME)} HDR --> The AUTH_LIFETIME notification is described in section 3. The original Responder that sends the AUTH_LIFETIME notification SHOULD send a DELETE notification when the end of the lifetime period. An Initiator that received an AUTH_LIFETIME notification SHOULD start an Initial exchange within the time indicated in the notification. 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 will look like this: Initiator Responder ----------------------------- -------------------------- HDR, SAi1, KEi, Ni --> <-- HDR, SAr1, KEr, Nr, [CERTREQ] HDR, SK {IDi, [CERT,] [CERTREQ,] [IDr,] AUTH, N(REKEY_SA)} --> <-- HDR, SK {IDr, [CERT,] AUTH} The REKEY_SA notification MUST contain the IKE SPI of the old SA. The Responder MUST check that the the IDi and SAi1 payloads match those of the old SA. The AUTH payloads sign the first and second messages of this 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 ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Nir [Page 2]
INTERNET-DRAFT Repeated Authentication in IKEv2 April 2004 o Payload Length is 12. o Protocol ID (1 octet) MUST be 1 (IKE_SA). o SPI size is 0 (SPI is in message header). o Notify Message type is to be assigned by IANA o Lifetime is the amount of time in seconds left before the peer should repeat the Initial exchange. 4. Interoperability with non-compliant 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. Non-compliant 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, in the remote-access scenario, it may be unreasonable for the lifetime to be lower than 300 seconds. 6. References [IKEv2] "Internet Key Exchange (IKEv2) Protocol", draft-ietf-ipsec-ikev2, work in progress. 7. IANA Considerations IANA is asked to assign a notification payload type for the AUTH_LIFETIME notifications from the IKEv2 Notification Payload Types registry. 8. Author's address Yoav Nir Check Point Software Technologies ynir@checkpoint.com Nir [Page 3]
