One document matched: draft-nir-ipsecme-erx-03.xml
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<rfc ipr="trust200902" docName="draft-nir-ipsecme-erx-03" category="std">
<front>
<title abbrev="ERX for IKE">An IKEv2 Extension for Supporting ERP</title>
<author initials="Y." surname="Nir" fullname="Yoav Nir">
<organization abbrev="Check Point">Check Point Software Technologies Ltd.</organization>
<address>
<postal>
<street>5 Hasolelim st.</street>
<city>Tel Aviv</city>
<code>67897</code>
<country>Israel</country>
</postal>
<email>ynir@checkpoint.com</email>
</address>
</author>
<author initials="Q." surname="Wu" fullname="Qin Wu">
<organization abbrev="Huawei">Huawei Technologies Co., Ltd.</organization>
<address>
<postal>
<street>101 Software Avenue, Yuhua District</street>
<city>Nanjing, JiangSu</city>
<code>210012</code>
<country>China</country>
</postal>
<email>sunseawq@huawei.com</email>
</address>
</author>
<date year="2012"/>
<area>Security Area</area>
<keyword>Internet-Draft</keyword>
<abstract>
<t> 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 5296bis.</t>
<t> NOTE TO RFC EDITOR: Replace 5296bis in the previous paragraph with the RFC number
assigned to that document.</t>
</abstract>
</front>
<middle>
<!-- ====================================================================== -->
<section anchor="introduction" title="Introduction">
<t> IKEv2, as specified in section 2.16 of <xref target="RFC5996"/>, allows authentication of
the initiator using an EAP method. 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.</t>
<t> The EAP Re-authentication Protocol (ERP), as described in <xref target="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.</t>
<t> 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.</t>
<section anchor="mustshouldmay" title="Conventions Used in This Document">
<t>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 <xref target="RFC2119"/>.</t>
</section>
</section>
<section anchor="scenarios" title="Usage Scenarios">
<t> This work is motivated by the following several scenarios.<list style="symbols">
<t> 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.</t>
<t> 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
access point are authenticators that connect to the same AAA servers. So it makes sense
to make the transition smooth, without requiring user interaction.
<xref target="SecureBeacon"/> is a now-abandoned attempt to allow detecting whether the
client should connect using VPN or not.</t></list></t>
</section>
<section anchor="outline" title="Protocol Outline">
<t> 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 <xref target="RFC5296bis"/>.</t>
<t> 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.</t>
<t> The responder sends the EAP payload content to a backend AAA server, and receives the
rMSK and an EAP-Finish/Re-auth message. It then forwards the EAP-Finish/Re-auth message
to the Initiator in an EAP payload within the first IKE_AUTH response.</t>
<t> 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 of <xref target="RFC5996"/>. The responder replies similarly, and the
IKE_AUTH exchange is finished.</t>
<t> 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.</t>
<figure>
<artwork><![CDATA[
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+]
]]></artwork>
</figure>
<section anchor="eap_clarif" title="Clarification About EAP Codes">
<t> Section 3.16 of <xref target="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.</t>
<t> 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), in addition to
the four codes enumerated in RFC 5996.</t>
</section>
<section anchor="keyname_nai" title="User Name in the Protocol">
<t> 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.</t>
<t> This section addresses instances where this is not the case.</t>
<t> Section 5.3.2 of <xref target="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 AAA server in the AccessRequest message, and is
returned from the AAA server in the AccessAccept message.</t>
<t> 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 identification for the purposes of logging.</t>
<t> 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: <list style="symbols">
<t> 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.</t>
<t> 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.</t>
<t> 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.</t></list></t>
<t> In any case authorization is a major issue in deployments, if the backend AAA server
supporting the re-authentication is different from the AAA server that had supported
the original authentication. It is up to the re-authenticating AAA server to provide
the necessary information for authorization.</t>
</section>
</section>
<section anchor="vid" title="ERX_SUPPORTED Notification">
<t> The Notify payload is as described in <xref target="RFC5996"/></t>
<figure>
<artwork><![CDATA[
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 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
<t><list style="symbols">
<t>Protocol ID (1 octet) MUST be 1, as this message is related to an IKE SA.</t>
<t>SPI Size (1 octet) MUST be zero, in conformance with section 3.10 of
<xref target="RFC5996"/>.</t>
<t>ERX Notify Message Type (2 octets) - MUST be xxxxx, the value assigned for ERX. TBA
by IANA.</t>
<t>Domain Name (variable) - contains the domain name or realm, as these terms are used
in <xref target="RFC5296bis"/>.</t></list></t>
</section>
<section anchor="security" title="Security Considerations">
<t> The protocol extension described in this document extends the authentication from one
EAP context, which may or may not be part of IKEv2, to an IKEv2 context. Successful
completion of the protocol proves to the authenticator, which in our case is a VPN
gateway, that the supplicant, or VPN client, has authenticated in some other EAP context.</t>
<t> The protocol supplies the authenticator with the domain name with which the supplicant
has authenticated, but does not supply it with a specific identity. Instead, the gateway
receives an EMSKName, which is an ephemeral ID.</t>
<t> If the domain name is sufficient to make access control decisions, this is enough. If
not, then the gateway needs to find out either the real name or authorization information
for that particular user. This may be done using the AAA protocol or by some other
federation protocol, which is out of scope for this specification.</t>
</section>
<section anchor="iana" title="IANA Considerations">
<t> 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".</t>
</section>
</middle>
<!-- ====================================================================== -->
<back>
<references title="Normative References">
<reference anchor='RFC2119'>
<front>
<title abbrev='RFC Key Words'>Key words for use in RFCs to Indicate Requirement Levels</title>
<author initials='S.' surname='Bradner' fullname='Scott Bradner'>
<organization>Harvard University</organization>
<address>
<postal>
<street>1350 Mass. Ave.</street>
<street>Cambridge</street>
<street>MA 02138</street>
</postal>
<phone>- +1 617 495 3864</phone>
<email>sob@harvard.edu</email>
</address>
</author>
<date year='1997' month='March' />
<area>General</area>
<keyword>keyword</keyword>
</front>
<seriesInfo name='BCP' value='14' />
<seriesInfo name='RFC' value='2119' />
<format type='TXT' octets='4723' target='ftp://ftp.isi.edu/in-notes/rfc2119.txt' />
<format type='HTML' octets='16553' target='http://tools.ietf.org/html/rfc2119' />
</reference>
<reference anchor='RFC5996'>
<front>
<title>Internet Key Exchange Protocol: IKEv2</title>
<author initials='C' surname='Kaufman' fullname='Charlie Kaufman'>
<organization>Microsoft</organization>
</author>
<author initials='P' surname='Hoffman' fullname='Paul Hoffman'>
<organization>VPN Consortium</organization>
</author>
<author initials='Y' surname='Nir' fullname='Yoav Nir'>
<organization>Check Point</organization>
</author>
<author initials='P' surname='Eronen' fullname='Pasi Eronen'>
<organization>Nokia</organization>
</author>
<date month='September' year='2010' />
</front>
<seriesInfo name='RFC' value='5996' />
<format type='TXT' target='http://www.ietf.org/rfc/rfc5996.txt' />
<format type='HTML' target='http://xml.resource.org/public/rfc/html/rfc5996.html' />
<format type='XML' target='http://xml.resource.org/public/rfc/xml/rfc5996.xml' />
</reference>
<reference anchor='RFC5296bis'>
<front>
<title>EAP Extensions for EAP Re-authentication Protocol (ERP)</title>
<author initials='W' surname='Wu' fullname='Wenson Wu'><organization /></author>
<author initials='Z' surname='Cao' fullname='Zhen Cao'><organization /></author>
<author initials='G' surname='Zorn' fullname='Glen Zorn'><organization /></author>
<author initials='Y' surname='Shi' fullname='Yang Shi'><organization /></author>
<author initials='B' surname='He' fullname='Baohong He'><organization /></author>
<date month='May' day='31' year='2011' />
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-hokey-rfc5296bis-06' />
<format type='TXT' target='http://www.ietf.org/internet-drafts/draft-ietf-hokey-rfc5296bis-06.txt' />
</reference>
</references>
<references title="Informative References">
<reference anchor='SecureBeacon'>
<front>
<title>Secure Beacon: Securely Detecting a Trusted Network</title>
<author initials='Y.' surname='Sheffer' fullname='Yaron Sheffer'>
<organization>Check Point</organization></author>
<author initials='Y.' surname='Nir' fullname='Yoav Nir'>
<organization>Check Point</organization></author>
<date year='2009' month='June' />
</front>
<seriesInfo name='Internet-Draft' value='draft-sheffer-ipsecme-secure-beacon' />
<format type='TXT'
target='http://tools.ietf.org/id/draft-sheffer-ipsecme-secure-beacon' />
<format type='HTML'
target='http://tools.ietf.org/html/draft-sheffer-ipsecme-secure-beacon' />
</reference>
</references>
<!-- ====================================================================== -->
</back>
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