An IKEv2 Extension for Supporting ERP
draft-nir-ipsecme-erx-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 6867.
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|---|---|---|---|
| Author | Yoav Nir | ||
| Last updated | 2011-11-19 (Latest revision 2011-07-11) | ||
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| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | Became RFC 6867 (Experimental) | |
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draft-nir-ipsecme-erx-02
Network Working Group Y. Nir
Internet-Draft Check Point
Intended status: Standards Track Q. Wu
Expires: May 22, 2012 Huawei
November 19, 2011
An IKEv2 Extension for Supporting ERP
draft-nir-ipsecme-erx-02
Abstract
This document describes an extension to the IKEv2 protocol that
allows an IKE Security Association (SA) to be created and
authenticated using the EAP Re-authentication Protocol extension as
described in RFC 5296 and its bis document.
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 May 22, 2012.
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Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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1. Introduction
IKEv2, as specified in [RFC5996], allows authentication of the
initiator using an EAP method. This is described in section 2.16.
Using EAP significantly increases the count of round-trips required
to establish the IPsec SA, and also may require user interaction.
This makes it inconvenient to allow a single remote access client to
create multiple IPsec tunnels with multiple IPsec gateways that
belong to the same domain.
The EAP Re-authentication Protocol (ERP), as descripted in
[RFC5296bis], allows an EAP peer to authenticate to multiple
authenticators, while performing the full EAP method only once.
Subsequent authentications require fewer round-trips and no user
interaction.
Bringing these two technologies together allows a remote access IPsec
client to create multiple tunnels with different gateways that belong
to a single domain, as well as using the keys from other contexts of
using EAP, such as network access within the same domain, to
transparently connect to VPN gateways within this domain.
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 Multiple tunnels for a single remote access VPN client. Suppose a
company has offices in New York City, Paris, and Shanghai. For
historical reasons, the email server is located in the Paris
office, while most of the servers hosting the company's intranet
are located in Shanghai, and the finance department servers are in
NYC. An employee using remote access VPN may need to connect to
servers from all three locations. While it is possible to connect
to a single gateway, and have that gateway route the requests to
the other gateways (perhaps through site-2-site VPN), this is not
efficient, and it is more desirable to have the client initiate
three different tunnels. It is, however, not desirable to have
the user type in a password three times.
o Roaming. In these days of mobile phones and tablets, users often
move from the wireless LAN in their office, where access may be
granted through 802.1x, to a cellular network where VPN is
necessary and back again. Both the VPN server and the 802.1x
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access point are authenticators that connect to the same AAA
servers. So it makes sense to make the transition smooth, without
requiring user interaction. [SecureBeacon] is an attempt to allow
detecting whether the client should connect using VPN or not.
3. Protocol Outline
Supporting ERX requires an EAP payload in the first IKE_AUTH request.
This is a deviation from the rules in RFC 5996, so support needs to
be indicated through a Notify payload in the IKE_SA_INIT response.
This Notify replaces the EAP-Initiate/Re-auth-Start message of ERX,
and therefore contains the domain name, as specified in section
5.3.1.1 of [RFC5296bis].
A supporting initiator that has unexpired keys for this domain will
send the EAP_Initiate/Re-auth message in an EAP payload in the first
IKE_AUTH request.
The responder sends the EAP payload content to a backend AAA server,
and receives the rMSK and an EAP-Finish/Re-auth message. If forwards
that to the initiator in an EAP payload within the first IKE_AUTH
response.
The initiator then sends an additional IKE_AUTH request, that
includes the AUTH payload which has been calculated using the rMSK in
the role of the MSK as described in sections 2.15 and 2.16 or
[RFC5996]. The responder replies similarly, and the IKE_AUTH
exchange is finished.
The following figure is adapted from appendixes C.1 and C.3 of RFC
5996, with most of the optional payloads removed. Note that the
EAP_Initiate/Re-auth message replaces the IDi payload.
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init request --> SA, KE, Ni,
init response <-- SA, KE, Nr,
N[ERX_SUPPORTED]
first request --> EAP(EAP_Initiate/Re-auth),
[[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+],
[IDr],
[CP(CFG_REQUEST)],
SA, TSi, TSr,
[V+][N+]
first response <-- IDr, [CERT+], AUTH,
EAP(EAP-Finish/Re-auth),
[V+][N+]
last request --> AUTH
last response <-- AUTH,
[CP(CFG_REPLY)],
SA, TSi, TSr,
[V+][N+]
3.1. Clarification About EAP Codes
Section 3.16 of [RFC5996] enumerates the EAP codes in EAP messages
which are carried in EAP payloads. The enumeration goes only to 4.
It is not clear whether that list is supposed to be exhaustive or
not.
To clarify, an implementation supporting this specification MUST
accept and transmit EAP messages with at least the codes for Initiate
and Finish (5 and 6).
3.2. User Name in the Protocol
The authors, as well as participants of the HOKEY and IPSECME working
groups believe that all use cases for this extension to IKE have a
single backend AAA server doing both the authentication and the re-
authentication. The reasoning behind this is that IKE runs over the
Internet, and would naturally connect to the user's home network.
This section addresses instances where this is not the case.
Section 5.3.2 of [RFC5296bis] describes the EAP-Initiate/Re-auth
packet, which in the case of IKEv2 is carried in the first IKE_AUTH
request. This packet contains the KeyName-NAI TLV. This TLV
contains the username used in authentication. It is relayed to the
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AAA server in the AccessRequest message, and is returned from the AAA
server in the AccessAccept message.
The username part of the NAI within the TLV is the EMSKName encoded
in hexadecimal digits. The domain part is the domain name of the
home domain of the user. The username part is ephemeral in the sense
that a new one is generated for each full authentication. This
ephemeral value is not a good basis for making policy decisions, and
they are also a poor source of user ID for the purposes of logging.
Instead, it is up to the implementation in the IPsec gateway to make
policy decisions based on other factors. The following list is by no
means exhaustive:
o In some cases the home domain name may be enough to make policy
decisions. If all users with a particular home domain get the
same authorization, then policy does not depend on the real user
name. Logging can still be done by correlating VPN gateway IKE
events with AAA servers access records.
o Sometimes users receive different authorizations based on groups
they belong to. The AAA server can communicate such information
to the VPN gateway, for example using the CLASS attribute in
RADIUS and DIAMETER. Logging again depends on correlation with
AAA servers.
o AAA servers may support extensions that allow them to communicate
with their clients (in our case - the VPN gateway) to push user
information. For example, a certain product integrates a RADIUS
server with LDAP, so a client could query the server using LDAP
and receive the real record for this user. Others may provide
this data through vendor-specific extensions to RADIUS or
DIAMETER.
In any case authorization is a major issue in deployments, if the
peer's home EAP server does not also perform the re-authentication.
4. ERX_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 ! ERX Notify Message Type !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Domain Name !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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 [RFC5996].
o ERX Notify Message Type (2 octets) - MUST be xxxxx, the value
assigned for ERX. TBA by IANA.
o Domain Name (variable) - contains the domain name or realm, as
these terms are used in [RFC5296bis].
5. Security Considerations
TBA
6. 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 "ERX_SUPPORTED".
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5296bis]
Wu, W., Cao, Z., Zorn, G., Shi, Y., and B. He, "EAP
Extensions for EAP Re-authentication Protocol (ERP)",
draft-ietf-hokey-rfc5296bis-06 (work in progress),
May 2011.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol: IKEv2", RFC 5996,
September 2010.
7.2. Informative References
[SecureBeacon]
Sheffer, Y. and Y. Nir, "Secure Beacon: Securely Detecting
a Trusted Network", draft-sheffer-ipsecme-secure-beacon
(work in progress), June 2009.
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Authors' Addresses
Yoav Nir
Check Point Software Technologies Ltd.
5 Hasolelim st.
Tel Aviv 67897
Israel
Email: ynir@checkpoint.com
Q. Wu
Huawei Technologies Co., Ltd.
101 Software Avenue, Yuhua District
Nanjing, JiangSu 210012
China
Email: Sunseawq@huawei.com
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