Network Working Group Y. Nir
Internet-Draft Check Point
Intended status: Experimental H. Tschofenig
Expires: February 13, 2011 NSN
H. Deng
China Mobile
R. Singh
Cisco
August 12, 2010
A Childless Initiation of the IKE SA
draft-nir-ipsecme-childless-05
Abstract
This document describes an extension to the IKEv2 protocol that
allows an IKE SA to be created and authenticated without generating a
Child SA.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on February 13, 2011.
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document authors. All rights reserved.
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
IKEv2, as specified in [IKEv2bis], 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. The extension described in this document allows the
creation of an IKE SA without also attempting to create a Child SA.
An IKE SA without any Child SA is not a fruitless endeavor. Even
without Child SAs, an IKE 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].
2. 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 IKE SA needs to be maintained.
o An IKE SA may be needed between peers even when there is not IPsec
traffic. Such IKE peers use liveness checks, and report to the
administrator the status of the "VPN links".
o IKE may be used on some physically secure links, where
authentication is necessary, but traffic protection is not. An
example of this in the PON links as described in [3GPP.33.820].
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o Childless IKE can be used for [EAP-IKEv2] where we use IKEv2 as a
method for user authentication.
o A node receiving IPsec traffic with an unrecognized 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 IKE SA so as to be able to send the notification in
a protected IKE_INFORMATIONAL exchange.
o A future extension may have IKE SAs used for generating keying
material for applications, without ever requiring Child SAs. This
is similar to what [extractors] is doing in 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 IKE peer might see the deletion of
the Child SA as a reason to delete the IKE SA.
3. 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 in Section 4, within the IKE_SA_INIT response.
A supporting initiator MAY send the modified IKE_AUTH request,
described in Section 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 in Section 5.
4. CHILDLESS_IKE_SUPPORTED Notification
The Notify payload is as described in [IKEv2bis]
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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
IKE SA.
o SPI Size (1 octet) MUST be zero, in conformance with section 3.10
of [IKEv2bis].
o Childless Notify Message Type (2 octets) - MUST be xxxxx, the
value assigned for CHILDLESS_IKE_SUPPORTED. TBA by IANA.
5. Modified IKE_AUTH Exchange
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 C.3 of [IKEv2bis].
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.
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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 [IKEv2bis].
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 is
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 is requested to assign a notify message type from the status
types range (16418-40959) of the "IKEv2 Notify Message Types"
registry with name "CHILDLESS_IKE_SUPPORTED".
8. References
8.1. Normative References
[IKEv2bis]
Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol: IKEv2",
draft-ietf-ipsecme-ikev2bis-11 (work in progress),
May 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[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.,
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and F. Bersani, "The Extensible Authentication Protocol-
Internet Key Exchange Protocol version 2 (EAP-IKEv2)
Method", RFC 5106, February 2008.
[SecureBeacon]
Sheffer, Y. and Y. Nir, "Secure Beacon: Securely Detecting
a Trusted Network", draft-sheffer-ipsecme-secure-beacon
(work in progress), June 2009.
[]
Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", draft-ietf-tls-extractor (work in
progress), March 2009.
Authors' 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
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Rajeshwar Singh Jenwar
Cisco Systems, Inc.
O'Shaugnessy Road
Bangalore, Karnataka 560025
India
Phone: +91 80 4103 3563
Email: rsj@cisco.com
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