Network Working Group V. Cakulev Internet-Draft Alcatel Lucent Intended status: Standards Track A. Lior Expires: August 27, 2011 Bridgewater Systems February 23, 2011 Diameter IKEv2 PSK: Pre-Shared Secret-based Support for IKEv2 Server to Diameter Server Interaction draft-ietf-dime-ikev2-psk-diameter-04.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 This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on August 27, 2011. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the Cakulev & Lior Expires August 27, 2011 [Page 1] Internet-Draft Diameter IKEv2 PSK February 2011 document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements notation . . . . . . . . . . . . . . . . . . . . 4 3. Application Identifier . . . . . . . . . . . . . . . . . . . . 5 4. Protocol Description . . . . . . . . . . . . . . . . . . . . . 6 4.1. Support for IKEv2 and Pre-Shared Secrets . . . . . . . . . 6 4.2. Session Management . . . . . . . . . . . . . . . . . . . . 6 4.2.1. Session-Termination-Request/Answer . . . . . . . . . . 7 4.2.2. Abort-Session-Request/Answer . . . . . . . . . . . . . 7 5. Command Codes for Diameter IKEv2 with PSK . . . . . . . . . . 8 5.1. IKEv2-PSK-Request (IKEPSKR) Command . . . . . . . . . . . 8 5.2. IKEv2-PSK-Answer (IKEPSKA) Command . . . . . . . . . . . . 9 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 Cakulev & Lior Expires August 27, 2011 [Page 2] Internet-Draft Diameter IKEv2 PSK February 2011 1. Introduction [RFC4306] defines the version 2 of Internet Key Exchange (IKE) 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. [RFC5778] 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 (EAP) [RFC3748] or using the Mobile IPv6 Authentication Protocol [RFC4285]. This document extends the functionality described by [RFC5778] 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. Cakulev & Lior Expires August 27, 2011 [Page 3] Internet-Draft Diameter IKEv2 PSK February 2011 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]. Cakulev & Lior Expires August 27, 2011 [Page 4] Internet-Draft Diameter IKEv2 PSK February 2011 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. Cakulev & Lior Expires August 27, 2011 [Page 5] Internet-Draft Diameter IKEv2 PSK February 2011 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/Answer defined in this document are used between IKEv2 server and a Home AAA server (HAAA) 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 and the SPI if available, 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 and SPI if available to the HAAA to obtain the PSK. The IDi payload extracted from the IKE_AUTH message MUST 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. The IKEv2-PSK-Request 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 and the Key-SPI AVP if included to retrieve the associated keying material. The HAAA SHALL use the nonces Ni and Nr received in IKEv2-Nonces AVP to generate the PSK. The HAAA returns the PSK to the IKEv2 Server using the Key AVP as specified in [I-D.ietf-dime-local-keytran]. 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]. 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 Cakulev & Lior Expires August 27, 2011 [Page 6] Internet-Draft Diameter IKEv2 PSK February 2011 successful IKEv2 negotiation exchange together with CHILD_SAs set up 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. Abort-Session-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. Cakulev & Lior Expires August 27, 2011 [Page 7] Internet-Draft Diameter IKEv2 PSK February 2011 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 ::= < 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 } [ Key-SPI ] [ Auth-Session-State ] { IKEv2-Nonces } * [ Proxy-Info ] * [ Route-Record ] ... * [ AVP ] Cakulev & Lior Expires August 27, 2011 [Page 8] Internet-Draft Diameter IKEv2 PSK February 2011 IKEv2-PSK-Request message MUST include a IKEv2-Nonces AVP containing Ni and Nr nonces exchanged during initial IKEv2 exchange. IKEv2-PSK- Request message MAY contain a Key-SPI AVP specified in [I-D.ietf-dime-local-keytran]. If included, it contains Security Parameter Index (SPI) that SHALL be used to identify the appropriate PSK. 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 ::= < Diameter Header: TBD3, PXY > < Session-Id > { Auth-Application-Id } { Auth-Request-Type } { Result-Code } { Origin-Host } { Origin-Realm } [ User-Name ] [ Key ] [ Auth-Session-State ] [ 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 is 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. If Key-SPI AVP is received in IKEv2-PSK-Request, Key-SPI AVP SHALL be included in Key AVP. Exactly how the PSK is derived is beyond the scope of this document. The Key-Lifetime AVP may be included and if Cakulev & Lior Expires August 27, 2011 [Page 9] Internet-Draft Diameter IKEv2 PSK February 2011 it is included then the associated key SHALL NOT be used if the lifetime has expired. Cakulev & Lior Expires August 27, 2011 [Page 10] Internet-Draft Diameter IKEv2 PSK February 2011 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. Cakulev & Lior Expires August 27, 2011 [Page 11] Internet-Draft Diameter IKEv2 PSK February 2011 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 | 0-1 | Key-SPI | 0-1 | 0 | IKEv2-Nonces | 1 | 0 | +---------+---------+ IKEPSKR and IKEPSKA Commands AVP Table Cakulev & Lior Expires August 27, 2011 [Page 12] Internet-Draft Diameter IKEv2 PSK February 2011 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]. Cakulev & Lior Expires August 27, 2011 [Page 13] Internet-Draft Diameter IKEv2 PSK February 2011 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 Cakulev & Lior Expires August 27, 2011 [Page 14] Internet-Draft Diameter IKEv2 PSK February 2011 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 IKEv2 Server 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 Key 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 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. Cakulev & Lior Expires August 27, 2011 [Page 15] Internet-Draft Diameter IKEv2 PSK February 2011 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. [RFC4285] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K. Chowdhury, "Authentication Protocol for Mobile IPv6", RFC 4285, January 2006. [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. [RFC5778] Korhonen, J., Tschofenig, H., Bournelle, J., Giaretta, G., and M. Nakhjiri, "Diameter Mobile IPv6: Support for Home Agent to Diameter Server Interaction", RFC 5778, February 2010. Cakulev & Lior Expires August 27, 2011 [Page 16] Internet-Draft Diameter IKEv2 PSK February 2011 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 Cakulev & Lior Expires August 27, 2011 [Page 17]