PANA Working Group Y. Ohba
Internet-Draft Toshiba
Intended status: Standards Track A. Yegin
Expires: March 12, 2010 Samsung
September 8, 2009
Definition of Master Key between PANA Client and Enforcement Point
draft-ohba-pana-pemk-03
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Abstract
This document defines a master key used between a client of the
Protocol for carrying Authentication for Network Access (PANA) and an
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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 across different types of lower-layers.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Specification of Requirements . . . . . . . . . . . . . . . 3
2. PaC-EP Master Key . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Key Name of PEMK . . . . . . . . . . . . . . . . . . . . . 4
2.2. Scope of PEMK . . . . . . . . . . . . . . . . . . . . . . . 4
2.3. Context of PEMK . . . . . . . . . . . . . . . . . . . . . . 5
2.4. Lifetime of PEMK . . . . . . . . . . . . . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
3.1. Channel Binding . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Guideline for distributing PEMK from PAA to EP . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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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. The EP and PAA may be
implemented on the same device or separate devices.
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
across different lower-layer types. 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].
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2. PaC-EP Master Key
A PEMK (PaC-EP Master Key) is derived from the 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 MSK is a Master Session Key generated by EAP and exported to PANA.
o SID is a four-octet PANA session identifier [RFC5191].
o KID is the content of the PANA Key-ID AVP associated with the MSK
[RFC5191].
o 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 address family
and address value guarantees the cryptographic independence of
PEMKs among multiple EPs across multiple lower-layer protocols.
How a PaC discovers an EPID is out of the scope of this document.
2.1. Key Name of PEMK
The key name of the PEMK is defined as follows.
PEMKname = MD5(EPID | SID | KID), where MD5 denotes Message-Digest
algorithm 5 hash function.
2.2. Scope of PEMK
A PEMK is used between a PaC and an EP. A PEMK MUST NOT be shared
among multiple PaCs or EPs.
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2.3. 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.
2.4. Lifetime of PEMK
The lifetime of a PEMK MUST be less than or equal to the lifetime of
the MSK.
3. 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 2.
3.1. 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 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.
3.2. 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.
4. IANA Considerations
This document has no actions for IANA.
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5. Acknowledgments
TBD.
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.
[IANAADFAM]
IANA, "Address Family Numbers",
http://www.iana.org/assignments/address-family-numbers.
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.
[I-D.ietf-pana-ipsec]
Parthasarathy, M., "PANA Enabling IPsec based Access
Control", draft-ietf-pana-ipsec-07 (work in progress),
July 2005.
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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
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