Internet DRAFT - draft-cakulev-ikev2-psk-diameter
draft-cakulev-ikev2-psk-diameter
Network Working Group V. Cakulev
Internet-Draft Alcatel Lucent
Intended status: Standards Track A. Lior
Expires: June 25, 2010 Bridgewater Systems
December 22, 2009
Diameter IKEv2: Support for Interaction between IKEv2 Server and
Diameter Server
draft-cakulev-ikev2-psk-diameter-01.txt
Abstract
Internet Key Exchange is a component of IPsec used for performing
mutual authentication as well as establishing and maintaining
security associations (SAs) between two parties such as a user and a
network entity. Internet Key Exchange v2 (IKEv2) protocol allows
several different mechanisms for authenticating a user, namely the
Extensible Authentication Protocol, certificates, and pre-shared
secrets. To authenticate and/or authorize the user, the network
element such as the Access Gateway may need to dynamically bootstrap
a security association based on interaction with the Diameter server.
This document specifies the interaction between the Access Gateway
and Diameter server for the IKEv2 based on pre-shared secrets.
Status of this Memo
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This Internet-Draft will expire on June 25, 2010.
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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. The Master-Security-Association . . . . . . . . . . . . . 11
6.1.1. Key . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1.2. MSA-Lifetime . . . . . . . . . . . . . . . . . . . . . 11
6.1.3. MSA-SPI . . . . . . . . . . . . . . . . . . . . . . . 11
6.2. IKEv2-Nonces . . . . . . . . . . . . . . . . . . . . . . . 11
6.2.1. Ni . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.2.2. Nr . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7. AVP Occurrence Tables . . . . . . . . . . . . . . . . . . . . 13
8. AVP Flag Rules . . . . . . . . . . . . . . . . . . . . . . . . 14
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9.1. Command Codes . . . . . . . . . . . . . . . . . . . . . . 15
9.2. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 15
9.3. Application Identifier . . . . . . . . . . . . . . . . . . 15
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
[RFC4306] defines IKEv2 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. Moreover, 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. This document
specifies the Diameter support for shared secrets (PSK) based IKEv2.
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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) TBD 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 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 Master-Security-Association AVP.
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
through that particular IKE_SA correspond to one currently active PSK
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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 | TBD | Section 5.1 | IKEPSK |
| | | | | |
| IKEv2-PSK-Answer | IKEPSKA | TBD | 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
TBD 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 TDB).
Message format
<IKEv2-PSK-Request> ::= < Diameter Header: TBD, 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 TBD 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 Mobile IPv6 IKE PSK Application ID
(value of TDB).
Message format
<IKEv2-PSK-Answer> ::= < Diameter Header: TBD, PXY >
< Session-Id >
{ Auth-Application-Id }
{ Auth-Request-Type }
{ Result-Code }
{ Origin-Host }
{ Origin-Realm }
[ User-Name ]
[Master-Security-Association ]
[ 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 Master-Security-Association.
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6. Attribute Value Pair Definitions
This section defines new AVPs for the IKEv2 with PSK.
6.1. The Master-Security-Association
The Master-Security-Association AVP (AVP Code TBD) is of type Grouped
and contains the session related information for use with the PSK
based IKEv2.
Master-Security-Association::= < AVP Header: TBD >
{ Key }
[ MSA-Lifetime ]
[ MSA-SPI ]
* [ AVP ]
6.1.1. Key
Key AVP (AVP Code TBD) is of type OctetString and contains the PSK.
The PSK is placed in this AVP most significant byte first. Exactly
how the PSK is derived is beyond the scope of this document.
6.1.2. MSA-Lifetime
MSA-Lifetime AVP (AVP Code TBD) is of type Unsigned32 and represents
the period of time (in seconds) for which the PSK is valid. The
associated PSK shall not be used if the lifetime has expired.
6.1.3. MSA-SPI
MSA-SPI AVP (AVP Code TBD) is of is of type Unsigned32 and contains
an SPI associated with the PSK.
6.2. IKEv2-Nonces
The IKEv2-Nonces AVP (Code TBD) 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: TBD>
{Ni}
{Nr}
*[AVP]
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6.2.1. Ni
The Ni AVP (AVP Code TBD) is of type Unsigned32 and contains the
IKEv2 initiator nonce.
6.2.2. Nr
The Nr AVP (AVP Code TBD) 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 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 |
-------------------------------|---------+---------+
Master-Security-Association | 0 | 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|
+-------------------------------------------+----+---+------+----+----+
|Master-Security- TBD 6.1 Grouped | M | P | | V | Y |
| Association | | | | | |
+-------------------------------------------+----+---+------+----+----+
|Key TBD 6.1.1 OctetString| M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|MSA-Lifetime TBD 6.1.2 Unsigned32 | M | P | | | |
+-------------------------------------------+----+---+------+----+----+
|MSA-SPI TBD 6.1.3 Unsigned32 | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|IKEv2-Nonces TBD 6.2 Grouped | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Ni TBD 6.2.1 Unsigned32 | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
|Nr TBD 6.2.2 Unsigned32 | M | P | | V | Y |
+-------------------------------------------+----+---+------+----+----+
AVP Flag Rules Table
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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 Master-Security-Association
o Key
o MSA-Lifetime
o MSA-SPI
o IKEv2-Nonces
o Ni
o Nr
The AVPs are defined in Section 6.
9.3. 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) | TBD
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10. Security Considerations
Any authentication and key agreement protocol with pre-shared keys
between an end-user client and AAA infrastructure relies on the
assumption that the client and network can mutually authenticate each
other. In context of, for example, 3GPP networks, the HAAA sharing a
PSK with the IKEv2 Server is similar to the HSS sharing an
authentication vector with the SGSN or MME in AKA based mutual
authentication protocols.
The basic security assumptions in sharing the PSK are based on the
following standard considerations.
o The security tunnel between the HAAA and the IKEv2 Server is
typically a mutually authenticated tunnel, with ciphering and
integrity protection for every packet. The existence of such
tunnels ensures that on-going trust and security are enforced, and
in particular the HAAA can guarantee that the IKEv2 Server is not
misbehaving.
o The protocol under discussion relies on the fact an IKEv2 Peer has
successfully authenticated with the system and has, for example,
an EMSK stored in the HAAA. The fact that the PSK is derived from
the EMSK proves to the HAAA of the existence of an authenticated
and active IKEv2 Peer.
o If the HAAA is to treat an IKEv2 Server as adversarial, then we
claim that under no circumstances can an IKEv2 Peer communicate
with that IKEv2 Server. Recall that any authentication and key
agreement protocol with pre-shared keys between an end-user client
and AAA infrastructure relies on the assumption that the client
and network can mutually authenticate each other, and furthermore
the client trusts the network elements that the AAA communicates
with and delegates post authentication security parameters to be
legitimate. If the HAAA is to treat the IKEv2 Server as
adversarial, then the trust assumption is no longer valid. This
in turn implies that the IKEv2 Peer is no longer guaranteed that
the network elements it is communicating with are trusted.
Hence the following two assumptions are critical to ensure secure
communications:
o The HAAA server and the IKEv2 Server share a trust relationship;
for instance, may be owned and managed by the same network
operator.
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o Moreover, transfer of keys between the HAAA and the IKEv2 Server
rely on an existing security association between the above network
elements.
In addition, the security considerations of the Diameter Base
protocol [RFC3588] are applicable to this document.
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11. References
11.1. Normative References
[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.
[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: 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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