Internet DRAFT - draft-dekok-emu-eap-session-id
draft-dekok-emu-eap-session-id
Network Working Group DeKok, Alan
INTERNET-DRAFT FreeRADIUS
Updates: 5247
Category: Standards Track
<draft-dekok-emu-eap-session-id-01.txt>
23 July 2019
EAP Session-Id Derivation
draft-dekok-emu-eap-session-id-01.txt
Abstract
EAP Session-Id derivation has not been defined for EAP-SIM, EAP-AKA,
and EAP-AKA' when using the fast re-authentication exchange instead
of full authentication. This document updates [RFC5247] to define
those derivations for EAP-SIM, and EAP-AKA. Since [AKAP] defines the
Session-ID for EAP-AKA', the definition for EAP-AKA' is not included
here. [RFC5247] also does not define Session-Id derivation for PEAP.
A definition is given here which follows the definition for other
TLS-based EAP methods.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
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This Internet-Draft will expire on July 22, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
DeKok, Alan Proposed Standard [Page 1]
INTERNET-DRAFT EAP Session-ID Derivation 23 July 2019
document authors. All rights reserved.
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DeKok, Alan Proposed Standard [Page 2]
INTERNET-DRAFT EAP Session-ID Derivation 23 July 2019
Table of Contents
1. Introduction ............................................. 4
1.1. Requirements Language ............................... 4
2. Updates to RFC 5247 Appendix A ........................... 5
2.1. EAP-AKA ............................................. 5
2.2. EAP-SIM ............................................. 5
2.3. Rationale ........................................... 7
2.4. Session-Id for PEAP ................................. 7
3. Security Considerations .................................. 7
4. IANA Considerations ...................................... 8
5. References ............................................... 8
5.1. Normative References ................................ 8
5.2. Informative References .............................. 8
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1. Introduction
EAP [RFC3748] Session-Id derivation has not been defined for EAP-SIM,
EAP-AKA, and EAP-AKA' when using the fast re-authentication exchange
instead of full authentication. [RFC5247] defines the Session-Id for
these EAP methods, but that derivation is only applicable for the
full authentication case.
The IEEE is defining FILS authentication [FILS], which needs the EAP
Session-Id for in order for the EAP Re-authentication Protocol (ERP)
[RFC5296] to work, it would be important to get this resolved with a
clearly defined and agreed derivation rules to allow fast re-
authentication cases to be used to derive ERP key hierarchy.
Further, [RFC5247] did not define Session-Id for PEAP. We correct
that deficiency here.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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2. Updates to RFC 5247 Appendix A
This section updates [RFC5247] Appendix A to define Session-Id for
fast re-authentication exchange for EAP-AKA and EAP-SIM. It further
defines Session-ID derivation for PEAP.
2.1. EAP-AKA
For EAP-AKA, [RFC5247] Appendix A says:
EAP-AKA
EAP-AKA is defined in [RFC4187]. The EAP-AKA Session-Id is the
concatenation of the EAP Type Code (0x17) with the contents of the
RAND field from the AT_RAND attribute, followed by the contents of
the AUTN field in the AT_AUTN attribute:
Session-Id = 0x17 || RAND || AUTN
It should say:
EAP-AKA
EAP-AKA is defined in [RFC4187]. When using full authentication,
the EAP-AKA Session-Id is the concatenation of the EAP Type Code
(0x17) with the contents of the RAND field from the AT_RAND
attribute, followed by the contents of the AUTN field in the
AT_AUTN attribute:
Session-Id = 0x17 || RAND || AUTN
When using fast re-authentication, the EAP-AKA Session-Id is the
concatenation of the EAP Type Code (0x17) with the contents of the
NONCE_S field from the AT_NONCE_S attribute, followed by the
contents of the MAC field from the AT_MAC attribute from EAP-
Request/AKA-Reauthentication:
Session-Id = 0x17 || NONCE_S || MAC
2.2. EAP-SIM
Similarly for EAP-SIM, it says:
EAP-SIM
EAP-SIM is defined in [RFC4186]. The EAP-SIM Session-Id is the
concatenation of the EAP Type Code (0x12) with the contents of the
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RAND field from the AT_RAND attribute, followed by the contents of
the NONCE_MT field in the AT_NONCE_MT attribute:
Session-Id = 0x12 || RAND || NONCE_MT
The Peer-Id is the contents of the Identity field from the
AT_IDENTITY attribute, using only the Actual Identity Length
octets from the beginning, however. Note that the contents are
used as they are transmitted, regardless of whether the
transmitted identity was a permanent, pseudonym, or fast EAP re-
authentication identity. The Server-Id is the null string (zero
length).
It should say:
EAP-SIM
EAP-SIM is defined in [RFC4186]. The EAP-SIM Session-Id is the
concatenation of the EAP Type Code (0x12) with the contents of the
RAND field from the AT_RAND attribute, followed by the contents of
the NONCE_MT field in the AT_NONCE_MT attribute. RFC 4186 says
that EAP server should obtain "n" GSM triplets where "n=2" or
"n=3".
For "n=2", the Session-Id is therefore defined as
Session-Id = 0x12 || RAND1 || RAND2 || NONCE_MT
which is 49 octets in length.
For "n=3", the Session-Id is therefore defined as
Session-Id = 0x12 || RAND1 || RAND2 || RAND3 || NONCE_MT
which is 65 octets in length.
The Peer-Id is the contents of the Identity field from the
AT_IDENTITY attribute, using only the Actual Identity Length
octets from the beginning, however. Note that the contents are
used as they are transmitted, regardless of whether the
transmitted identity was a permanent, pseudonym, or fast EAP re-
authentication identity. The Server-Id is the null string (zero
length).
When using fast re-authentication, the EAP-SIM Session-Id is the
concatenation of the EAP Type Code (0x12) with the contents of the
NONCE_S field from the AT_NONCE_S attribute, followed by the
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contents of the MAC field from the AT_MAC attribute from EAP-
Request/AKA-Reauthentication:
Session-Id = 0x12 || NONCE_S || MAC
which is 33 octets in length.
2.3. Rationale
[RFC5247] was supposed to define exported parameters for existing EAP
methods in Appendix A. The way Session-Id was defined for EAP-AKA and
EAP-SIM works only for the full authentication case, i.e., it cannot
be used when the optional fast re-authentication case is used since
the used parameters (RAND, AUTN, NONCE_MT) are not used in the fast
re-authentication case. Based on [RFC4187] Section 5.2, and similar
text in [RFC4186], NONCE_S corresponds to RAND and MAC in EAP-
Request/AKA-Reauthentication corresponds to AUTN. That would seem to
imply that the Session-Id could be defined using NONCE_S and MAC
instead of RAND and AUTN/NONCE_MT.
2.4. Session-Id for PEAP
[RFC5247] did not define Session-Id definition for Microsoft's
Protected EAP (PEAP). Similar to the definition in [RFC5216] Section
2.3, we define it as:
Session-Id = 0x19 || client.random || server.random
This definition is already in wide-spread use in multiple PEAP
implementations.
Note that this definition for Session-Id only applies when TLS 1.2 or
earlier is used. A different derivation is defined for TLS 1.3.
3. Security Considerations
This specification defines EAP Session-Ids for ERP with EAP-SIM and
EAP-AKA. It therefore enables ERP key hierarchy establishment using
fast re-authentication with EAP-SIM and EAP-AKA.
There are no known security issues from using the NONCE_S and MAC as
defined above.
This specification also defines the EAP Session-Id for PEAP. That
deriviation has no known security issues.
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4. IANA Considerations
There are no actions for IANA. RFC EDITOR: This section may be
removed before publication.
5. References
5.1. Normative References
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March, 1997, <http://www.rfc-
editor.org/info/rfc2119>.
[RFC3748]
Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748,
June 2004.
[RFC5216]
Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS Authentication
Protocol", RFC 5216, March 2008
[RFC5247]
Aboba, B., Simon, D., and P. Eronen, "Extensible Authentication
Protocol (EAP) Key Management Framework", RFC 5247, August 2008,
[RFC5296]
Narayanan, V. and L. Dondeti, "EAP Extensions for EAP Re-
authentication Protocol (ERP)", RFC 5296, August 2008.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key
Words", RFC 8174, May 2017, <http://www.rfc-
editor.org/info/rfc8174>.
[FILS]
"IEEE Standard for 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 -
Amendment 1: Fast Initial Link Setup", IEEE Std 802.11ai-2016,
2016.
5.2. Informative References
[RFC4186]
Haverinen, H. (Ed), Salowey, J., "Extensible Authentication
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Protocol Method for Global System for Mobile Communications (GSM)
Subscriber Identity Modules (EAP-SIM)", RFC 4186, January 2006.
[RFC4187]
Arkko, J., Haverinen, H., "Extensible Authentication Protocol
Method for 3rd Generation Authentication and Key Agreement (EAP-
AKA)", RFC 4187, January 2006.
[AKAP]
Arkko, J., et al, "Improved Extensible Authentication Protocol
Method for 3rd Generation Authentication and Key Agreement (EAP-
AKA')", draft-arkko-eap-rfc5448bis-04.txt, January 2019.
Acknowledgments
The issue corrected in this specification was first reported by Jouni
Malinen in a technical errata at https://www.rfc-
editor.org/errata_search.php?rfc=5247
The text in this document follows his suggestions.
Authors' Addresses
Alan DeKok
The FreeRADIUS Server Project
Email: aland@freeradius.org
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