This document describes an extension to the IKEv2 protocol that allows an IKE SA to be created and authenticated without generating a child SA.
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1.1. Conventions Used in This Document
2. Usage Scenarios
3. Protocol Outline
4. VID Payload
5. Modified IKE_AUTH Exchange
6. Security Considerations
7. IANA Considerations
8.1. Normative References
8.2. Informative References
§ Authors' Addresses
IKEv2, as specified in [RFC4306] (Kaufman, C., “Internet Key Exchange (IKEv2) Protocol,” December 2005.) requires, that the IKE_AUTH exchange try to create a child SA along with the IKE SA. This requirement is sometimes inconvenient or superfluous, as some implementations need to use IKE for authentication only, while others would like to set up the IKE SA before there is any actual traffic to protect.
An IKE SA without any child SA is not a fruitless endeavor. Even without Child SAs, an IKE SA allows:
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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).
Several scenarios motivated this proposal:
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 IKE peer might see the deletion of the Child SA as a reason to delete the IKE SA.
The decision of whether or not to support an IKE_AUTH exchage without the piggy-backed child SA negotiation is ultimately up to the reponsder. A supporting resonder MUST include the VID payload, described in Section 4 (VID Payload), within the IKE_SA_INIT response.
A supporting initiator MAY send the modified IKE_AUTH request, described in Section 5 (Modified IKE_AUTH Exchange), if the VID payload was included in the IKE_SA_INIT response. The initiator MUST NOT send the modified IKE_AUTH request if the VID was not present.
A supporting responder that advertised the VID payload 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 VID payload, and it SHOULD reply with an INVALID_SYNTAX Notify payload if the client sends an IKE_AUTH request that is modified as described in Section 5 (Modified IKE_AUTH Exchange).
The VID payload is as described in [RFC4306] (Kaufman, C., “Internet Key Exchange (IKEv2) Protocol,” December 2005.) with a 16-octets data field as follows:
This value was obtained by hashing the string "Will do IKE_AUTH without child SA payloads" using the MD5 algorithms. Note that this is only an explanation, and the actual content of the VID data MUST be the value above.
For brevity, only the EAP version of an AUTH exchange will be presented here. The non-EAP version is very similar. The figures below are based on appendix A.3 of [RFC4718] (Eronen, P. and P. Hoffman, “IKEv2 Clarifications and Implementation Guidelines,” October 2006.).
first request --> IDi, [N(INITIAL_CONTACT)], [[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+], [IDr], [CP(CFG_REQUEST)], [V+] first response <-- IDr, [CERT+], AUTH, EAP, [V+] / --> EAP repeat 1..N times | \ <-- EAP last request --> AUTH last response <-- AUTH, [CP(CFG_REPLY)], [N(ADDITIONAL_TS_POSSIBLE)], [V+]
Note what is missing:
There are no IANA considerations for this document.
|[RFC2119]||Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML).|
|[RFC4306]||Kaufman, C., “Internet Key Exchange (IKEv2) Protocol,” RFC 4306, December 2005 (TXT, HTML).|
|[RFC4718]||Eronen, P. and P. Hoffman, “IKEv2 Clarifications and Implementation Guidelines,” RFC 4718, October 2006 (TXT, HTML).|
|[3GPP.33.820]||3GPP, “Security of H(e)NB,” 3GPP TR 33.820 8.0.0, March 2009.|
|[EAP-IKEv2]||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 (TXT, HTML).|
|[SecureBeacon]||Sheffer, Y. and Y. Nir, “Secure Beacon: Securely Detecting a Trusted Network,” draft-sheffer-ipsecme-secure-beacon (work in progress), June 2009 (TXT, HTML).|
|[extractors]||Rescorla, E., “Keying Material Exporters for Transport Layer Security (TLS),” draft-ietf-tls-extractor (work in progress), March 2009 (TXT, HTML).|
|Check Point Software Technologies Ltd.|
|5 Hasolelim st.|
|Tel Aviv 67897|
|Nokia Siemens Networks|
|Phone:||+358 (50) 4871445|
|Rajeshwar Singh Jenwar|
|Cisco Systems, Inc.|
|Bangalore, Karnataka 560025|
|Phone:||+91 80 4103 3563|