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Independent Submission                                            Y. NirRequest for Comments: 6023                                   Check PointCategory: Experimental                                     H. TschofenigISSN: 2070-1721                                                      NSN                                                                 H. Deng                                                            China Mobile                                                                R. Singh                                                                   Cisco                                                            October 2010A Childless Initiation ofthe Internet Key Exchange Version 2 (IKEv2) Security Association (SA)Abstract   This document describes an extension to the Internet Key Exchange   version 2 (IKEv2) protocol that allows an IKEv2 Security Association   (SA) to be created and authenticated without generating a Child SA.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for examination, experimental implementation, and   evaluation.   This document defines an Experimental Protocol for the Internet   community.  This is a contribution to the RFC Series, independently   of any other RFC stream.  The RFC Editor has chosen to publish this   document at its discretion and makes no statement about its value for   implementation or deployment.  Documents approved for publication by   the RFC Editor are not a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6023.Nir, et al.                   Experimental                      [Page 1]

RFC 6023               Childless IKEv2 Initiation           October 2010Copyright Notice   Copyright (c) 2010 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (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.1.  Introduction   IKEv2, as specified in [RFC5996], requires that the IKE_AUTH exchange   try to create a Child SA along with the IKEv2 SA.  This requirement   is sometimes inconvenient or superfluous, as some implementations   need to use IKEv2 for authentication only, while others would like to   set up the IKEv2 SA before there is any actual traffic to protect.   The extension described in this document allows the creation of an   IKEv2 SA without also attempting to create a Child SA.  The terms   IKEv2, IKEv2 SA, and Child SA and the various IKEv2 exchanges are   defined in [RFC5996]   An IKEv2 SA without any Child SA is not a fruitless endeavor.  Even   without Child SAs, an IKEv2 SA allows:   o  Checking the liveness status of the peer via liveness checks.   o  Quickly setting up Child SAs without public key operations and      without user interaction.   o  Authentication of the peer.   o  Detection of NAT boxes between two hosts on the Internet.1.1.  Conventions Used in This Document   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].Nir, et al.                   Experimental                      [Page 2]

RFC 6023               Childless IKEv2 Initiation           October 20102.  Usage Scenarios   Several scenarios motivated this proposal:   o  Interactive remote access VPN: the user tells the client to      "connect", which may involve interactive authentication.  There is      still no traffic, but some may come later.  Since there is no      traffic, it is impossible for the gateway to know what selectors      to use (how to narrow down the client's proposal).   o  Location-aware security, as in [SecureBeacon].  The user is      roaming between trusted and untrusted networks.  While in an      untrusted network, all traffic should be encrypted, but on the      trusted network, only the IKEv2 SA needs to be maintained.   o  An IKEv2 SA may be needed between peers even when there is not      IPsec traffic.  Such IKEv2 peers use liveness checks, and report      to the administrator the status of the "VPN links".   o  IKEv2 may be used on some physically secure links, where      authentication is necessary but traffic protection is not.  An      example of this is the Passive Optical Network (PON) links as      described in [3GPP.33.820].   o  Childless IKEv2 can be used for [RFC5106] where we use IKEv2 as a      method for user authentication.   o  A node receiving IPsec traffic with an unrecognized Security      Parameter Index (SPI) should send an INVALID_SPI notification.  If      this traffic comes from a peer, which it recognizes based on its      IP address, then this node may set up an IKEv2 SA so as to be able      to send the notification in a protected INFORMATIONAL exchange.   o  A future extension may have IKEv2 SAs used for generating keying      material for applications, without ever requiring Child SAs.  This      is similar to what [RFC5705] is doing in Transport Layer Security      (TLS).   In some of these cases, it may be possible to create a dummy Child SA   and then remove it, but this creates undesirable side effects and   race conditions.  Moreover, the IKEv2 peer might see the deletion of   the Child SA as a reason to delete the IKEv2 SA.Nir, et al.                   Experimental                      [Page 3]

RFC 6023               Childless IKEv2 Initiation           October 20103.  Protocol Outline   The decision of whether or not to support an IKE_AUTH exchange   without the piggy-backed Child SA negotiation is ultimately up to the   responder.  A supporting responder MUST include the Notify payload,   described inSection 4, within the IKE_SA_INIT response.   A supporting initiator MAY send the modified IKE_AUTH request,   described inSection 5, if the notification was included in the   IKE_SA_INIT response.  The initiator MUST NOT send the modified   IKE_AUTH request if the notification was not present.   A supporting responder that has advertised support by including the   notification in the IKE_SA_INIT response MUST process a modified   IKE_AUTH request, and MUST reply with a modified IKE_AUTH response.   Such a responder MUST NOT reply with a modified IKE_AUTH response if   the initiator did not send a modified IKE_AUTH request.   A supporting responder that has been configured not to support this   extension to the protocol MUST behave as the same as if it didn't   support this extension.  It MUST NOT advertise the capability with a   notification, and it SHOULD reply with an INVALID_SYNTAX Notify   payload if the client sends an IKE_AUTH request that is modified as   described inSection 5.4.  CHILDLESS_IKEV2_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    ! Childless Notify Message Type !       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   o  Protocol ID (1 octet) MUST be 1, as this message is related to an      IKEv2 SA.   o  SPI Size (1 octet) MUST be zero, in conformance withsection 3.10      of [RFC5996].   o  Childless Notify Message Type (2 octets) - MUST be 16418, the      value assigned for CHILDLESS_IKEV2_SUPPORTED.Nir, et al.                   Experimental                      [Page 4]

RFC 6023               Childless IKEv2 Initiation           October 20105.  Modified IKE_AUTH Exchange   For brevity, only the Extensible Authentication Protocol (EAP)   version of an AUTH exchange will be presented here.  The non-EAP   version is very similar.  The figures below are based onAppendix C.3   of [RFC5996].    first request       --> IDi,                            [N(INITIAL_CONTACT)],                            [[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+],                            [IDr],                            [CP(CFG_REQUEST)],                            [V+][N+]    first response      <-- IDr, [CERT+], AUTH,                            EAP,                            [V+][N+]                      / --> EAP    repeat 1..N times |                      \ <-- EAP    last request        --> AUTH    last response       <-- AUTH,                            [CP(CFG_REPLY)],                            [V+][N+]   Note what is missing:   o  The optional notifications: IPCOMP_SUPPORTED, USE_TRANSPORT_MODE,      ESP_TFC_PADDING_NOT_SUPPORTED, and NON_FIRST_FRAGMENTS_ALSO.   o  The SA payload.   o  The traffic selector payloads.   o  Any notification, extension payload or VendorID that has to do      with Child SA negotiation.6.  Security Considerations   This protocol variation inherits all the security properties of   regular IKEv2 as described in [RFC5996].   The new notification carried in the initial exchange advertises the   capability, and cannot be forged or added by an adversary without   being detected, because the response to the initial exchange isNir, et al.                   Experimental                      [Page 5]

RFC 6023               Childless IKEv2 Initiation           October 2010   authenticated with the AUTH payload of the IKE_AUTH exchange.   Furthermore, both peers have to be configured to use this variation   of the exchange in order for the responder to accept a childless   proposal from the initiator.7.  IANA Considerations   IANA has assigned a notify message type from the "IKEv2 Notify   Message Types" registry with the name "CHILDLESS_IKEV2_SUPPORTED" and   the value "16418".8.  References8.1.  Normative References   [RFC2119]       Bradner, S., "Key words for use in RFCs to Indicate                   Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC5996]       Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,                   "Internet Key Exchange Protocol Version 2 (IKEv2)",RFC 5996, September 2010.8.2.  Informative References   [3GPP.33.820]   3GPP, "Security of H(e)NB", 3GPP TR 33.820 8.0.0,                   March 2009.   [RFC5106]       Tschofenig, H., Kroeselberg, D., Pashalidis, A.,                   Ohba, Y., and F. Bersani, "The Extensible                   Authentication Protocol-Internet Key Exchange                   Protocol version 2 (EAP-IKEv2) Method",RFC 5106,                   February 2008.   [RFC5705]       Rescorla, E., "Keying Material Exporters for                   Transport Layer Security (TLS)",RFC 5705,                   March 2010.   [SecureBeacon]  Sheffer, Y. and Y. Nir, "Secure Beacon: Securely                   Detecting a Trusted Network", Work in Progress,                   June 2009.Nir, et al.                   Experimental                      [Page 6]

RFC 6023               Childless IKEv2 Initiation           October 2010Authors' Addresses   Yoav Nir   Check Point Software Technologies Ltd.   5 Hasolelim st.   Tel Aviv  67897   Israel   EMail: ynir@checkpoint.com   Hannes Tschofenig   Nokia Siemens Networks   Linnoitustie 6   Espoo  02600   Finland   Phone: +358 (50) 4871445   EMail: Hannes.Tschofenig@gmx.net   URI:http://www.tschofenig.priv.at   Hui Deng   China Mobile   53A,Xibianmennei Ave.   Xuanwu District   Beijing  100053   China   EMail: denghui02@gmail.com   Rajeshwar Singh Jenwar   Cisco Systems, Inc.   O'Shaugnessy Road   Bangalore, Karnataka  560025   India   Phone: +91 80 4103 3563   EMail: rsj@cisco.comNir, et al.                   Experimental                      [Page 7]