Network Working Group V. Cakulev
Internet-Draft Alcatel Lucent
Intended status: Standards Track A. Lior
Expires: September 9, 2010 Bridgewater Systems
March 8, 2010
Diameter IKEv2 PSK: Pre-Shared Secret-based Support for IKEv2 Server to
Diameter Server Interaction
draft-ietf-dime-ikev2-psk-diameter-02.txt
Abstract
The Internet Key Exchange protocol version 2 (IKEv2) is a component
of the IPsec architecture and is used to perform mutual
authentication as well as to establish and to maintain IPsec security
associations (SAs) between the respective parties. IKEv2 supports
several different authentication mechanisms, such as the Extensible
Authentication Protocol (EAP), certificates, and pre-shared secrets.
With [RFC 5778] the Diameter interworking for Mobile IPv6 between the
Home Agent, as a Diameter client, and the Diameter server has been
specified. However, that specification focused on the usage of EAP
and did not include support for pre-shared secret based
authentication available with IKEv2. This document therefore extends
the functionality offered by [RFC 5778] with pre-shared key based
authentication offered by IKEv2 when no EAP is used.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 5
3. Application Identifier . . . . . . . . . . . . . . . . . . . . 6
4. Protocol Description . . . . . . . . . . . . . . . . . . . . . 7
4.1. Support for IKEv2 and Pre-Shared Secrets . . . . . . . . . 7
4.2. Session Management . . . . . . . . . . . . . . . . . . . . 7
4.2.1. Session-Termination-Request/Answer . . . . . . . . . . 8
4.2.2. AbortSession-Request/Answer . . . . . . . . . . . . . 8
5. Command Codes for Diameter IKEv2 with PSK . . . . . . . . . . 9
5.1. IKEv2-PSK-Request (IKEPSKR) Command . . . . . . . . . . . 9
5.2. IKEv2-PSK-Answer (IKEPSKA) Command . . . . . . . . . . . . 10
6. Attribute Value Pair Definitions . . . . . . . . . . . . . . . 11
6.1. IKEv2-Nonces . . . . . . . . . . . . . . . . . . . . . . . 11
6.1.1. Ni . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1.2. Nr . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7. AVP Occurrence Tables . . . . . . . . . . . . . . . . . . . . 12
8. AVP Flag Rules . . . . . . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 14
9.2. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 14
9.3. AVP Values . . . . . . . . . . . . . . . . . . . . . . . . 14
9.4. Application Identifier . . . . . . . . . . . . . . . . . . 14
10. Security Considerations . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
[RFC4306] defines Internet Key Exchange v2 as a protocol that
performs mutual authentication between two parties and establishes a
security association (SA) that includes shared secret information
that can be used to efficiently establish SAs for Encapsulating
Security Payload (ESP) [RFC4303] and/or Authentication Header (AH)
[RFC4302], and a set of cryptographic algorithms to be used by the
SAs to protect the traffic that they carry. IKEv2 protocol allows
several different mechanisms for authenticating a IKEv2 Peer to be
used, such as the Extensible Authentication Protocol, certificates,
and pre-shared secrets.
From a service provider perspective it is important to ensure that a
user is authorized to use the services. Therefore, the IKEv2 Server
must verify that the IKEv2 Peer is authorized for the requested
services possibly with the assistance of the operator's Diameter
servers. [RFC 5778] defines the home agent as a Diameter client to
the Diameter server communication when the mobile node authenticates
using the IKEv2 protocol with the Extensible Authentication Protocol
or using the Mobile IPv6 Authentication Protocol. This document
extends the functionality offered by [RFC 5778] with pre-shared key
based authentication offered by IKEv2. This document does not assume
that the IKEv2 Server has the pre-shared secrets (PSK) with the IKEv2
Peer. Instead, it allows for PSK to be derived for a specific IKEv2
session and exchanged between IKEv2 Server and HAAA. This is
accomplished through the use of a new Diameter application
specifically designed for performing IKEv2 authorization decisions.
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2. Requirements notation
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].
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3. Application Identifier
This specification defines a new Diameter application and its
respective Application Identifier:
Diameter IKE PSK (IKEPSK) TBD1 by IANA
The IKEPSK Application Identifier is used when the IKEv2 Peer is to
be authenticated and authorized using IKEv2 with PSK-based
authentication.
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4. Protocol Description
4.1. Support for IKEv2 and Pre-Shared Secrets
When IKEv2 is used with PSK-based initiator authentication, the
Diameter commands IKEv2-PSK-Request and IKEv2-PSK-Answer defined in
this document are used to authorize the IKEv2 Peer for the services.
Upon receiving the IKE_AUTH message from the IKEv2 Peer, the IKEv2
Server uses the information received in IDi to determine if it has
the PSK for this IKEv2 Peer. If there is no PSK found associated
with this IKEv2 Peer, the IKEv2 Server MUST send an Authorize-Only
(Auth-Request-Type set to "Authorize-Only") Diameter IKEv2-PSK
message with the IKEv2 Peer's IDi payload to the HAAA to obtain the
PSK. The IDi payload extracted from the IKE_AUTH message has to
contain an identity that is meaningful for the Diameter
infrastructure, such as a Network Access Identifier (NAI), since it
is used by the IKEv2 Server to populate the User-Name AVP in the
Diameter message. The IKEv2 Server also includes in the IKEv2-Nonces
AVP of the same Diameter message the initiator and responder nonces
(Ni and Nr) exchanged during initial IKEv2 exchange.
This message is routed to the IKEv2 Peer's HAAA. Upon receiving
Diameter IKEv2-PSK-Request message from the IKEv2 Server, the HAAA
SHALL use the User-Name AVP to retrieve the associated keying
material. The HAAA SHALL use the nonces Ni and Nr received in IKEv2-
Nonces AVP to generate the PSK. It is outside of scope of this
document how the HAAA obtains or generates the PSK. For example, if
the HAAA previously performed EAP based access authentication and
authorization of the IKEv2 Peer, it can use the available EMSK to
generate the PSK [RFC5295]. The HAAA returns the PSK to the IKEv2
Server using the Key AVP as specified in
[I-D.ietf-dime-local-keytran].
Once the IKEv2 Server receives the PSK from the HAAA, the IKEv2
Server verifies the IKE_AUTH message received from the IKEv2 Peer.
If the verification of AUTH is successful, the IKEv2 Server sends the
IKE message back to the IKEv2 Peer.
4.2. Session Management
The HAAA may maintain state or may be stateless. This is indicated
by presence or absence of the Auth-Session-State AVP. The IKEv2
Server MUST support the Authorization Session State Machine defined
in [RFC3588].
This specification makes an assumption that each IKE_SA created
between the IKEv2 Peer and the IKEv2 Server as a result of a
successful IKEv2 negotiation exchange together with CHILD_SAs set up
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through that particular IKE_SA correspond to one currently active PSK
and one active Diameter session.
4.2.1. Session-Termination-Request/Answer
In the case where session tracking is being used, when the IKEv2
Server terminates the SA it SHALL send a Session-Termination-Request
(STR) message [RFC3588] to inform the HAAA that the authorized
session has been terminated.
The Session-Termination-Answer (STA) message [RFC3588] is sent by the
HAAA to acknowledge the notification that the session has been
terminated.
4.2.2. AbortSession-Request/Answer
The Abort-Session-Request (ASR) message [RFC3588] is sent by the HAAA
to the IKEv2 Server to terminate the authorized session. When the
IKEv2 Server receives the ASR message, it MUST delete the
corresponding IKE_SA and all CHILD_SAs set up through it.
The Abort-Session-Answer (ASA) message [RFC3588] is sent by the IKEv2
Server in response to an ASR message.
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5. Command Codes for Diameter IKEv2 with PSK
This section defines new Command-Code values that MUST be supported
by all Diameter implementations conforming to this specification.
+-------------------+---------+------+-------------+-------------+
| Command-Name | Abbrev. | Code | Reference | Application |
+-------------------+---------+------+-------------+-------------+
| IKEv2-PSK-Request | IKEPSKR | TBD2 | Section 5.1 | IKEPSK |
| | | | | |
| IKEv2-PSK-Answer | IKEPSKA | TBD3 | Section 5.2 | IKEPSK |
+-------------------+---------+------+-------------+-------------+
Table 1: Command Codes
5.1. IKEv2-PSK-Request (IKEPSKR) Command
The IKEv2-PSK-Request message, indicated with the Command-Code set to
TBD2 and the 'R' bit set in the Command Flags field is sent from the
IKEv2 Server to the HAAA to initiate IKEv2 with PSK authorization.
In this case, the Application-ID field of the Diameter Header MUST be
set to the Diameter IKE PSK Application ID (value of TDB1).
Message format
<IKEv2-PSK-Request> ::= < Diameter Header: TBD2, REQ, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Origin-Host }
{ Origin-Realm }
{ Destination-Realm }
{ Auth-Request-Type }
[ Destination-Host ]
[ NAS-Identifier ]
[ NAS-IP-Address ]
[ NAS-IPv6-Address ]
[ NAS-Port ]
[ Origin-State-Id ]
{ User-Name }
[ Auth-Session-State ]
{ IKEv2-Nonces }
* [ Proxy-Info ]
* [ Route-Record ]
...
* [ AVP ]
IKEv2-PSK-Request message MUST include a IKEv2-Nonces AVP containing
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Ni and Nr nonces exchanged during initial IKEv2 exchange.
5.2. IKEv2-PSK-Answer (IKEPSKA) Command
The IKEv2-PSK-Answer (IKEPSKA) message, indicated by the Command-Code
field set to TBD3 and the 'R' bit cleared in the Command Flags field,
is sent by the HAAA to the IKEv2 Server in response to the IKEPSKR
command. In this case, the Application-ID field of the Diameter
Header MUST be set to the Diameter IKE PSK Application ID (value of
TDB1).
Message format
<IKEv2-PSK-Answer> ::= < Diameter Header: TBD3, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Request-Type }
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
[ User-Name ]
[ Key ]
[ Error-Message ]
[ Error-Reporting-Host ]
* [ Failed-AVP ]
[ Origin-State-Id ]
* [ Redirect-Host ]
[ Redirect-Host-Usage ]
[ Redirect-Max-Cache-Time ]
* [ Proxy-Info ]
* [ Route-Record ]
...
* [ AVP ]
If the authorization procedure was successful then the IKEv2-PSK-
Answer message SHALL include the Key AVP as specified in
[I-D.ietf-dime-local-keytran]. The value of the Key-Type AVP SHALL
be set to TBD4. The Keying-Material AVP SHALL contain the PSK.
Exactly how the PSK is derived is beyond the scope of this document.
The Key-Lifetime AVP may be included and if it is included then the
associated key shall not be used if the lifetime has expired.
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6. Attribute Value Pair Definitions
This section defines new AVPs for the IKEv2 with PSK.
6.1. IKEv2-Nonces
The IKEv2-Nonces AVP (Code TBD5) is of type Grouped and contains the
nonces exchanged between the IKEv2 Peer and the IKEv2 Server during
IKEv2 initial exchange. The nonces are used for PSK generation.
IKEv2-Nonces ::= < AVP Header: TBD5>
{Ni}
{Nr}
*[AVP]
6.1.1. Ni
The Ni AVP (AVP Code TBD6) is of type Unsigned32 and contains the
IKEv2 initiator nonce.
6.1.2. Nr
The Nr AVP (AVP Code TBD7) is of type Unsigned32 and contains the
IKEv2 responder nonce.
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7. AVP Occurrence Tables
The following tables present the AVPs defined or used in this
document and their occurrences in Diameter messages. Note that AVPs
that can only be present within a Grouped AVP are not represented in
this table.
The table uses the following symbols:
0:
The AVP MUST NOT be present in the message.
0+:
Zero or more instances of the AVP MAY be present in the message.
0-1:
Zero or one instance of the AVP MAY be present in the message.
1:
One instance of the AVP MUST be present in the message.
+-------------------+
| Command-Code |
|---------+---------+
AVP Name | IKEPSKR | IKEPSKA |
-------------------------------|---------+---------+
Key | 0-1 | 0-1 |
IKEv2-Nonces | 0-1 | 0 |
+---------+---------+
IKEPSKR and IKEPSKA Commands AVP Table
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8. AVP Flag Rules
The following table describes the Diameter AVPs, their AVP Code
values, types, possible flag values, and whether the AVP MAY be
encrypted. The Diameter base [RFC3588] specifies the AVP Flag rules
for AVPs in Section 4.5.
+--------------------+
| AVP Flag rules |
+----+---+------+----+----+
AVP Defined | | |SHOULD|MUST|MAY |
Attribute Name Code in Value Type |MUST|MAY| NOT | NOT|Encr|
+-------------------------------------------+----+---+------+----+----+
|Key TBD Note 1 Grouped | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Keying-Material TBD Note 1 OctetString| M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Key-Lifetime TBD Note 1 Integer64 | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Key-SPI TBD Note 1 Unsigned32 | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Key-Type TBD Note 1 Enumerated | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Key-Name TBD Note 1 OctetString| M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|IKEv2-Nonces TBD5 6.2 Grouped | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Ni TBD6 6.2.1 Unsigned32 | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Nr TBD7 6.2.2 Unsigned32 | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
AVP Flag Rules Table
Note 1: Key, Keying-Material, Key-Type, Key-SPI, Key-Name and Key-
Lifetime AVPs are defined in [I-D.ietf-dime-local-keytran].
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9. IANA Considerations
This section contains the namespaces that have either been created in
this specification or had their values assigned to existing
namespaces managed by IANA.
9.1. Command Codes
IANA is requested to allocate a command code value for the IKEv2-PSK-
Request message (IKEPSKR) and for the IKEv2-PSK-Answer message
(IKEPSKA) from the Command Code namespace defined in [RFC3588]. See
Section 5 for the assignment of the namespace in this specification.
9.2. AVP Codes
This specification requires IANA to register the following new AVPs
from the AVP Code namespace defined in [RFC3588].
o IKEv2-Nonces
o Ni
o Nr
The AVPs are defined in Section 6.
9.3. AVP Values
IANA is requested to create a new value for the Key-Type AVP. The
new value TBD4 signifies that IKEv2 PSK is being sent.
9.4. Application Identifier
This specification requires IANA to allocate one new value "Diameter
IKE PSK" from the Application Identifier namespace defined in
[RFC3588].
Application Identifier | Value
-------------------------------+------
Diameter IKE PSK (IKEPSK) | TBD1
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10. Security Considerations
The security considerations of the Diameter Base protocol [RFC3588]
are applicable to this document.
The Diameter messages between the IKEv2 Server and the HAAA may be
transported via one or more AAA brokers or Diameter agents. In this
case, the HA to the Diameter server AAA communication relies on the
security properties of the intermediating AAA inter-connection
networks, AAA brokers, and Diameter agents. Furthermore, any agents
that process IKEv2-PSK-Answer messages can see the contents of the
Master-Security-Association AVP. For this reason, this specification
strongly recommends avoiding Diameter agents when they cannot be
trusted to keep the keys secret.
This specification expects that the HAAA derives and returns the
associated session key to the IKEv2 Server. For the key derivation
this specification recommends the use of a short lived secrets,
possibly based on a previous network access authentication run if
such secrets are available. To ensure key freshness, limit the key
scope etc., this specification also recommends the use of nonces, if
nonces are included in IKEv2-PSK-Request. However, this
specification does not define how the Diameter server actually
derives required keys. The details of the key derivation depends on
the deployment where this specification is used and therefore the
security properties of the system depend on how this is done.
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11. References
11.1. Normative References
[I-D.ietf-dime-local-keytran]
Wu, W. and G. Zorn, "Diameter Attribute-Value Pairs for
Cryptographic Key Transport",
draft-ietf-dime-local-keytran-01 (work in progress),
January 2010.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
December 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005.
[RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.
11.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)",
RFC 3748, June 2004.
[RFC5295] Salowey, J., Dondeti, L., Narayanan, V., and M. Nakhjiri,
"Specification for the Derivation of Root Keys from an
Extended Master Session Key (EMSK)", RFC 5295,
August 2008.
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Authors' Addresses
Violeta Cakulev
Alcatel Lucent
600 Mountain Ave.
3D-517
Murray Hill, NJ 07974
US
Phone: +1 908 582 3207
Email: violeta.cakulev@alcatel-lucent.com
Avi Lior
Bridgewater Systems
303 Terry Fox Drive
Otawa, Ontario K2K 3J1
Canada
Phone: +1 613-591-6655
Email: avi@bridgewatersystems.com
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