PANA Working Group Y. Ohba Internet-Draft Toshiba Intended status: Standards Track A. Yegin Expires: July 11, 2010 Samsung January 7, 2010 Definition of Master Key between PANA Client and Enforcement Point draft-ohba-pana-pemk-04 Abstract This document defines a master key used between a client of the Protocol for carrying Authentication for Network Access (PANA) and an enforcement point, for bootstrapping lower-layer ciphering. The master key is derived from the Master Session Key of Extensible Authentication Protocol as a result of successful PANA authentication. The master key guarantees cryptographic independence among enforcement points bootstrapped from PANA authentication across different address families. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on July 11, 2010. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. Ohba & Yegin Expires July 11, 2010 [Page 1] Internet-Draft PaC-EP Master Key January 2010 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 BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Specification of Requirements . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. PaC-EP Master Key . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Key Name of PEMK . . . . . . . . . . . . . . . . . . . . . 5 3.2. Scope of PEMK . . . . . . . . . . . . . . . . . . . . . . . 5 3.3. Context of PEMK . . . . . . . . . . . . . . . . . . . . . . 5 3.4. Lifetime of PEMK . . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 4.1. Channel Binding . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Guideline for distributing PEMK from PAA to EP . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Ohba & Yegin Expires July 11, 2010 [Page 2] Internet-Draft PaC-EP Master Key January 2010 1. Introduction PANA (Protocol for carrying Authentication for Network Access) [RFC5191] is designed to facilitate network access authentication and authorization of clients in access networks. It carries EAP [RFC3748] between a PaC (PANA Client) and a PAA (PANA Authentication Agent) where the PAA functions as an authentication gateway to the Authentication Server (AS). The PANA framework [RFC5193] defines an another entity referred to as an EP (Enforcement Point) which resides in the access network and allows access (data traffic) of authorized PaCs while preventing access of others depending on the PANA authentication and authorization result (Figure 1). The EP and PAA may be implemented on the same device or separate devices. RADIUS, Diameter, +-----+ PANA +-----+ LDAP, API, etc. +-----+ | PaC |<----------------->| PAA |<------------------->| AS | +-----+ +-----+ +-----+ ^ ^ | | | +-----+ | IKE, +-------->| EP |<--------+ ANCP, API, etc. 4-way handshake, +-----+ etc. . . . v Data traffic Figure 1: PANA Functional Model The EP uses non-cryptographic or cryptographic filters to selectively allow and discard data packets. These filters may be applied at the link-layer or the IP-layer [I-D.ietf-pana-ipsec]. When cryptographic access control is used, a secure association protocol [RFC3748] needs to run between the PaC and EP. After completion of the secure association protocol, link or network layer per-packet security (for example IPsec ESP) is enabled for integrity protection, data origin authentication, replay protection and optionally confidentiality protection. This document defines PaC-EP Master Key (PEMK) that is used by a secure association protocol as the pre-shared secret between the PaC and EP to enable cryptographic filters in the access network. The PEMK is defined to guarantee cryptographic independence among EPs bootstrapped from PANA authentication across different address families. This document also describes a guideline for distributing Ohba & Yegin Expires July 11, 2010 [Page 3] Internet-Draft PaC-EP Master Key January 2010 PEMKs from the PAA to EP. This document does not specify a mechanism for a PaC to know whether the lower-layer requires a secure association protocol or the pre- shared secret for the secure association protocol needs to be bootstrapped from PANA authentication. Such a mechanism may be defined by each lower-layer protocol. 1.1. Specification of Requirements In this document, several words are used to signify the requirements of the specification. These words are often capitalized. 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. Terminology This document reuses the following terms defined in [RFC5191]: PaC (PANA Client), PAA (PANA Authentication Agent), EP (Enforcement Point), MSK (Master Session Key), PANA Session, and Session Identifier. 3. PaC-EP Master Key A PEMK (PaC-EP Master Key) is derived from an available MSK. The PEMK is 64 octets in length and it is calculated as follows: PEMK = prf+(MSK, "IETF PEMK" | SID | KID | EPID) where | denotes concatenation. o The prf+ function is defined in IKEv2 [RFC4306]. The pseudo- random function used for the prf+ function is specified in the PRF-Algorithm AVP carried in a PANA-Auth-Request message with 'S' (Start) bit set. o "IETF PEMK" is the ASCII code representation of the non-NULL terminated string (excluding the double quotes around it). o SID is a four-octet Session Identifier [RFC5191]. o KID is the content of the Key-ID AVP [RFC5191] associated with the MSK. o EPID is the identifier of the EP. The first two octets represents the AddressType, which contains an Address Family defined in Ohba & Yegin Expires July 11, 2010 [Page 4] Internet-Draft PaC-EP Master Key January 2010 [IANAADFAM]. The remaining octets encode the address value. The length of the address value is determined by the AddressType. The AddressType is used to discriminate the content and format of the remaining octets for the address value. The use of the combination of address family and address value guarantees the cryptographic independence of PEMKs among multiple EPs that are bootstrapped from PANA authentication across multiple address families. How a PaC discovers an EPID is out of the scope of this document. 3.1. Key Name of PEMK The key name of the PEMK is defined as follows. PEMKname = SHA1(EPID | SID | KID), where SHA1 denotes the SHA-1 algorithm specified in [SHS]. Inclusion of the EPID, SID and KID provides uniqueness of PEMK names among multiple PaC-EP pairs under a given PAA. 3.2. Scope of PEMK One PEMK is used between one PaC and one EP. A PEMK MUST NOT be shared among multiple PaCs or EPs. 3.3. Context of PEMK A PEMK is used as the pre-shared key of the secure association protocol in the scope of the PEMK. A PEMK MUST NOT be used for any other usage. 3.4. Lifetime of PEMK The lifetime of a PEMK MUST be less than or equal to the lifetime of the MSK from which it is derived. At the end of the lifetime, the PEMK and its associated states MUST be deleted. 4. Security Considerations The following considerations are specifically made to follow the AAA key management guidance [RFC4962]. Other AAA key management requirements such as key lifetime, key scope, key context and key name are described under Section 3. 4.1. Channel Binding Since the device identifier of the EP is involved in the key derivation function, Channel Binding on a PEMK is made between the Ohba & Yegin Expires July 11, 2010 [Page 5] Internet-Draft PaC-EP Master Key January 2010 PaC and PAA at the time when the PEMK is generated. If a malicious EP advertises a different device identifier than that is registered with the PAA, the malicious attempt will not succeed since the secure association protocol will fail due to the difference in the PEMK values calculated by the PaC and the EP. 4.2. Guideline for distributing PEMK from PAA to EP When an EP is implemented on the same device as the PAA, no protocol needs to be used for distributing a PEMK from the PAA to the EP. In the case where the EP is implemented on a separate device from the PAA, a protocol is needed to distribute a PEMK from the PAA to the EP. Such a key distribution protocol may depend on the architecture and deployment using PANA. A key distribution protocol for a PEMK MUST ensure that the PEMK is encrypted as well as integrity and replay protected, with a security association between the PAA and EP, where the security association MUST be cryptographically bound to the identities of the PAA and EP known to the PaC. 5. IANA Considerations This document has no actions for IANA. 6. Acknowledgments We would like to thank Jari Arkko, Basavaraj Patil, Pasi Eronen, Russ Mundy, Alexey Melnikov and all members of the PANA working group for their valuable comments to this document. 7. References 7.1. Normative References [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748, June 2004. [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [RFC5191] Forsberg, D., Ohba, Y., Patil, B., Tschofenig, H., and A. Yegin, "Protocol for Carrying Authentication for Network Access (PANA)", RFC 5191, May 2008. Ohba & Yegin Expires July 11, 2010 [Page 6] Internet-Draft PaC-EP Master Key January 2010 [SHS] National Institute of Standards and Technology, U.S. Department of Commerce, "Secure Hash Standard", NIST FIPS PUB 180-2, August 2002. [IANAADFAM] IANA, "Address Family Numbers", http://www.iana.org/assignments/address-family-numbers. 7.2. Informative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4962] Housley, R. and B. Aboba, "Guidance for Authentication, Authorization, and Accounting (AAA) Key Management", BCP 132, RFC 4962, July 2007. [RFC5193] Jayaraman, P., Lopez, R., Ohba, Y., Parthasarathy, M., and A. Yegin, "Protocol for Carrying Authentication for Network Access (PANA) Framework", RFC 5193, May 2008. [I-D.ietf-pana-ipsec] Parthasarathy, M., "PANA Enabling IPsec based Access Control", draft-ietf-pana-ipsec-07 (work in progress), July 2005. Authors' Addresses Yoshihiro Ohba Toshiba Corporate Research and Development Center 1 Komukai-Toshiba-cho Saiwai-ku, Kawasaki, Kanagawa 212-8582 Japan Phone: +81 44 549 2230 Email: yoshihiro.ohba@toshiba.co.jp Alper Yegin Samsung Istanbul Turkey Email: alper.yegin@yegin.org Ohba & Yegin Expires July 11, 2010 [Page 7]