Network Working Group Y. Nir
Internet-Draft Check Point
Intended status: Standards Track H. Tschofenig
Expires: August 4, 2010 NSN
H. Deng
China Mobile
R. Singh
Cisco
January 31, 2010
A Childless Initiation of the IKE SA
draft-nir-ipsecme-childless-02
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
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Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . . 3
2. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Outline . . . . . . . . . . . . . . . . . . . . . . . 4
4. VID Payload . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Modified IKE_AUTH Exchange . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
IKEv2, as specified in [RFC4306] 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:
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].
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.
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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 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, within the IKE_SA_INIT response.
A supporting initiator MAY send the modified IKE_AUTH request,
described in Section 5, 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.
4. VID Payload
The VID payload is as described in [RFC4306] with a 16-octets data
field as follows:
73da4b423dd9f75563b15b9f918650fc
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.
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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 A.3 of [RFC4718].
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:
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
TBA
7. IANA Considerations
There are no IANA considerations for this document.
8. References
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8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.
[RFC4718] Eronen, P. and P. Hoffman, "IKEv2 Clarifications and
Implementation Guidelines", RFC 4718, October 2006.
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.,
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
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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.com
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