One document matched: draft-walker-ieee802-req-01.txt
Differences from draft-walker-ieee802-req-00.txt
Network Working Group Dorothy Stanley
INTERNET-DRAFT Agere
Category: Best Current Practice Jesse Walker
<draft-walker-ieee802-req-01.txt> Intel Corporation
11 May 2004 Bernard Aboba
Microsoft Corporation
EAP Method Requirements for Wireless LANs
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026.
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
The IEEE 802.11i MAC Security Enhancements Amendment makes use of
IEEE 802.1X which in turn relies on the Extensible Authentication
Protocol (EAP). This document defines requirements for EAP methods
used in IEEE 802.11 wireless LAN deployments. The material in this
document has been approved by IEEE 802.11 and it is being presented
as an IETF RFC for informational purposes.
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1. Introduction
The IEEE 802.11i MAC Security Enhancements Amendment [IEEE802.11i]
makes use of IEEE 802.1X [IEEE8021X-REV] which in turn relies on the
Extensible Authentication Protocol (EAP), defined in [RFC3748].
Deployments of IEEE 802.11 wireless LANs today are based on EAP, and
use several EAP methods, including EAP-TLS [RFC2716], EAP-TTLS
[TTLS], PEAP [PEAP] and EAP-SIM [SIM]. These methods support
authentication credentials that include digital certificates, user-
names and passwords, secure tokens, and SIM secrets.
This document defines requirements for EAP methods used in IEEE
802.11 wireless LAN deployments. EAP methods claiming conformance to
the IEEE 802.11 wireless LAN requirements for EAP methods must
complete IETF last call review.
1.1. Requirements specification
In this document, several words are used to signify the requirements
of the specification. 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].
An EAP authentication method is not compliant with this specification
if it fails to satisfy one or more of the MUST or MUST NOT
requirements. An EAP authentication method that satisfies all the
MUST, MUST NOT, SHOULD and SHOULD NOT requirements is said to be
"unconditionally compliant"; one that satisfies all the MUST and MUST
NOT requirements but not all the SHOULD or SHOULD NOT requirements is
said to be "conditionally compliant".
1.2. Terminology
authenticator
The end of the link initiating EAP authentication. The term
Authenticator is used in [IEEE-802.1X], and authenticator has the
same meaning in this document.
peer The end of the link that responds to the authenticator. In
[IEEE-802.1X], this end is known as the Supplicant.
Supplicant
The end of the link that responds to the authenticator in
[IEEE-802.1X].
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backend authentication server
A backend authentication server is an entity that provides an
authentication service to an authenticator. When used, this server
typically executes EAP methods for the authenticator. This
terminology is also used in [IEEE-802.1X].
EAP server
The entity that terminates the EAP authentication method with the
peer. In the case where no backend authentication server is used,
the EAP server is part of the authenticator. In the case where the
authenticator operates in pass-through mode, the EAP server is
located on the backend authentication server.
Master Session Key (MSK)
Keying material that is derived between the EAP peer and server and
exported by the EAP method. The MSK is at least 64 octets in
length. In existing implementations a AAA server acting as an EAP
server transports the MSK to the authenticator.
Extended Master Session Key (EMSK)
Additional keying material derived between the EAP client and
server that is exported by the EAP method. The EMSK is at least 64
octets in length. The EMSK is not shared with the authenticator or
any other third party. The EMSK is reserved for future uses that
are not defined yet.
4-Way Handshake
A pairwise Authentication and Key Management Protocol (AKMP)
defined in [IEEE802.11i], which confirms mutual possession of a
Pairwise Master Key by two parties and distributes a Group Key.
2. Method requirements
2.1. Credential types
The IEEE 802.11i MAC Security Enhancements Amendment requires that
EAP authentication methods are available. Wireless LAN deployments
are expected to use different credentials types, including digital
certificates, user-names and passwords, existing secure tokens, and
mobile network credentials (GSM and UMTS secrets). Other credential
types that may be used include public/private key (without
necessarily requiring certificates), and asymmetric credential
support (such as password on one side, public/private key on the
other).
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2.2. Mandatory requirements
EAP authentication methods suitable for use in wireless LAN
authentication MUST satisfy the following criteria:
[1] Generation of symmetric keying material. This corresponds to the
"Key derivation" security claim defined in [RFC3748], Section
7.2.1.
[2] Key strength. An EAP method suitable for use with IEEE 802.11 MUST
be capable of generating keying material with 128-bits of effective
key strength, as defined in [RFC3748] Section 7.2.1. As noted in
[RFC3748] Section 7.10, an EAP method supporting key derivation
MUST export a Master Session Key (MSK) of at least 64 octets, and
an Extended Master Session Key (EMSK) of at least 64 octets.
[3] Mutual authentication support. This corresponds to the "Mutual
authentication" security claim defined in [RFC3748], Section 7.2.1.
[4] Synchronization of state. This requirement applies when the EAP
method completes successfully. The exact state attributes that are
shared may vary from method to method but typically include the
protocol both executed, what credentials were presented and
accepted by both parties, what cryptographic keys are shared and
what EAP method specific attributes were negotiated, such as cipher
suites and limitations of usage on all protocol state. Both
parties must be able to distinguish this instance of the protocol
from all other instances of the protocol and they must share the
same view of which state attributes are public and which are
private to the two parties alone.
[5] Resistance to dictionary attacks. This corresponds to the
"Dictionary attack resistance" security claim defined in [RFC3748],
Section 7.2.1.
[6] Protection against man-in-the-middle attacks. This corresponds to
the "Cryptographic binding", "Integrity protection", "Replay
protection", and "Session independence" security claims defined in
[RFC3748], Section 7.2.1.
[7] Protected ciphersuite negotiation. If the method negotiates the
ciphersuite used to protect the EAP conversation, then it MUST
support the "Protected ciphersuite negotiation" security claim
defined in [RFC3748], Section 7.2.1.
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2.3. Recommended requirements
EAP authentication methods used for wireless LAN authentication
SHOULD support the following features:
[8] Fragmentation. [RFC3748] Section 3.1 states: "EAP methods can
assume a minimum EAP MTU of 1020 octets, in the absence of other
information. EAP methods SHOULD include support for fragmentation
and reassembly if their payloads can be larger than this minimum
EAP MTU." This implies support for the "Fragmentation" claim
defined in [RFC3748], Section 7.2.1.
[9] End-user identity hiding. This corresponds to the
"Confidentiality" security claim defined in [RFC3748], Section
7.2.1.
2.4. Optional features
EAP authentication methods used for wireless LAN authentication MAY
support the following features:
[10] Channel binding. This corresponds to the "Channel binding"
security claim defined in [RFC3748], Section 7.2.1.
[11] Fast reconnect. This corresponds to the "Fast reconnect" security
claim defined in [RFC3748], Section 7.2.1.
2.5. Non-compliant EAP authentication methods
EAP-MD5-Challenge (the current mandatory-to-implement EAP
authentication method), is defined in [RFC3748] Section 5.4. EAP-
MD5-Challenge, One-Time Password (Section 5.5) and Generic Token Card
(Section 5.6), as defined in [RFC3748] are non-compliant with the
requirements specified in this document. As noted in [RFC3748],
these methods do not support any of the mandatory requirements
defined in Section 2.2 including key derivation, or mutual
authentication. In addition, these methods do not support any of the
recommended features defined in Section 2.3 or any of the optional
features defined in Section 2.4.
3. Security Considerations
Within [IEEE802.11i], EAP is used for both authentication and key
exchange between the EAP peer and server. Given that wireless local
area networks provide ready access to an attacker within range, EAP
usage within [IEEE802.11i] is subject to the threats outlined in
[RFC3748] Section 7.1. Security considerations relating to EAP are
discussed in [RFC3748] Sections 7; where an authentication server is
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utilized, the security considerations described in [RFC3579], Section
4 will apply.
The system security properties required to address the threats
described in [RFC3748] Section 7.1 are noted in [Housley56]:
Algorithm independence
Wherever cryptographic algorithms are chosen, the algorithms must
be negotiable, in order to provide resilience against compromise of
a particular cryptographic algorithm. This is addressed by
mandatory requirement [7] in Section 2.2. Algorithm independence
is one of the EAP invariants described in [KEYFRAME].
Strong, fresh session keys
Session keys must be demonstrated to be strong and fresh in all
circumstances, while at the same time retaining algorithm
independence. Key strength is addressed by mandatory requirement
[2] in Section 2.2. Recommendations for ensuring the Freshness of
keys derived by EAP methods are discussed in [RFC3748], Section
7.10.
Replay protection
All protocol exchanges must be replay protected. This is addressed
by mandatory requirement [6] in Section 2.2.
Authentication
All parties need to be authenticated. Mutual authentication is
required as part of mandatory requirement [3] in Section 2.2. The
confidentiality of the authenticator must be maintained. Identity
protection is a recommended capability, described in requirement
[9] in Section 2.3. No plaintext passwords are allowed. EAP does
not support plaintext passwords, as noted in [RFC3748] Section
7.14.
Authorization
EAP peer and authenticator authorization must be performed. Issues
relating to authorization are discussed in [RFC3748] Section 7.15,
and [RFC3579] Section 4.3.7.
Session keys
Confidentiality of session keys must be maintained. Issues
relating to Key Derivation are described in [RFC3748] Section 7.10,
as well as in [KEYFRAME].
Ciphersuite negotiation
The selection of the "best" ciphersuite must be securely confirmed.
This is addressed in mandatory requirement [7] in Section 2.2.
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Unique naming
Session keys must be uniquely named. Key naming issues are
addressed in [KEYFRAME].
Domino effect
Compromise of a single authenticator cannot compromise any other
part of the system, including session keys and long-term secrets.
This issue is addressed by mandatory requirement [6] in Section
2.2.
Key binding
The key must be bound to the appropriate context. This issue is
addressed in optional requirement [10] in Section 2.4. Channel
binding is also discussed in Section 7.15 of [RFC3748].
4. References
4.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March, 1997.
[RFC3748] Blunk, L. , et al., "Extensible Authentication Protocol
(EAP)", RFC 3748, May 2004.
[802.11] Information technology - Telecommunications and information
exchange between systems - Local and metropolitan area
networks - Specific Requirements Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY) Specifications,
IEEE Std. 802.11-1999, 1999.
[IEEE8021X-REV]
IEEE Standards for Local and Metropolitan Area Networks: Port
based Network Access Control, IEEE Std 802.1X-REV, Draft 9,
March 2004.
[IEEE802.11i]
Institute of Electrical and Electronics Engineers, "Unapproved
Draft Supplement to Standard for Telecommunications and
Information Exchange Between Systems - LAN/MAN Specific
Requirements - Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications: Specification
for Enhanced Security", IEEE Draft 802.11i (work in progress),
2003.
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4.2. Informative References
[Housley56]
Housley, R., "Key Management in AAA", Presentation to the AAA
WG at IETF 56,
http://www.ietf.org/proceedings/03mar/slides/aaa-5/index.html,
March 2003.
[RFC2716] Aboba, B. and D. Simon, "PPP EAP TLS Authentication Protocol",
RFC 2716, October 1999.
[RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication Dial
In User Service) Support For Extensible Authentication
Protocol (EAP)", RFC 3579, September 2003.
[PEAP] Palekar, A., et al., "Protected EAP Protocol (PEAP)", draft-
josefsson-pppext-eap-tls-eap-08.txt, Internet draft (work in
progress), May 2004.
[TTLS] Funk, P. and S. Blake-Wilson, "EAP Tunneled TLS Authentication
Protocol (EAP-TTLS)", draft-ietf-pppext-eap-ttls-03.txt,
August 2003.
[EAPSIM] Haverinen, H. and J. Salowey, "EAP SIM Authentication", draft-
haverinen-pppext-eap-sim-12.txt, Internet draft (work in
progress), October 2003.
[IEEE802] IEEE Standards for Local and Metropolitan Area Networks:
Overview and Architecture, ANSI/IEEE Std 802, 1990.
[KEYFRAME]
Aboba, B., "EAP Key Management Framework", draft-ietf-eap-
keying-02 (work in progress), May 2004.
Acknowledgments
The authors would like to acknowledge contributions to this document
from members of the IEEE 802.11i Task Group, including Russ Housley
of Vigil Security, David Nelson of Enterasys Networks and Clint
Chaplin of Symbol Technologies, as well as members of the EAP WG
including Joe Salowey of Cisco Systems, Pasi Eronen of Nokia, Jari
Arkko of Ericsson, and Florent Bersani of France Telecom.
Authors' Addresses
Dorothy Stanley
Agere Systems
2000 North Naperville Rd.
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Naperville, IL 60566
EMail: dstanley@agere.com
Phone: +1 630 979 1572
Jesse R. Walker
Intel Corporation
2111 N.E. 25th Avenue
Hillsboro, OR 97214
EMail: jesse.walker@intel.com
Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
EMail: bernarda@microsoft.com
Phone: +1 425 706 6605
Fax: +1 425 936 7329
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Expiration Date
This memo is filed as <draft-walker-ieee802-req-01.txt>, and
expires November 22, 2004.
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