RFC 5807: Definition of Master Key between PANA Client and Enforcement Point

Text version

Internet Engineering Task Force (IETF)
Request for Comments: 5807
Category: Standards Track
ISSN: 2070-1721

Y. Ohba
Toshiba
A. Yegin
Samsung
March 2010

Definition of Master Key between PANA Client and Enforcement Point

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 the 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 is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc5807.

Copyright Notice

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.

   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.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 7

1. Introduction

The Protocol for carrying Authentication for Network Access (PANA) [RFC5191] is designed to facilitate network access authentication and authorization of clients in access networks. It carries Extensible Authentication Protocol (EAP) [RFC3748] between a PANA Client (PaC) and a PANA Authentication Agent (PAA) 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 Enforcement Point (EP), 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 [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 the 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 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 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.

"IETF PEMK" is the ASCII code representation of the non-NULL terminated string (excluding the double quotes around it).

SID is a four-octet Session Identifier [RFC5191].

KID is the content of the Key-ID AVP [RFC5191] associated with the MSK.

EPID is the identifier of the EP. The first two octets represents the AddressType, which contains an Address Family defined in [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 Authentication, Authorization, and Accounting (AAA) key management guidance [RFC4962]. Other AAA key management requirements such as key lifetime, key scope, key context, and key name are described in 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 PaC and PAA at the time when the PEMK is generated. If a malicious

EP advertises a different device identifier than that 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. 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.

6. References

6.1. 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.
   
   [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.

6.2. 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.
   
   [PANA-IPSEC]  Parthasarathy, M., "PANA Enabling IPsec based Access
                 Control", 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