Internet DRAFT - draft-ietf-emu-eap-session-id
draft-ietf-emu-eap-session-id
Network Working Group DeKok, Alan
INTERNET-DRAFT FreeRADIUS
Updates: 5247 (if approved) 3 September 2020
Intended status: Standards Track
Expires: March 03, 2021
EAP Session-Id Derivation for EAP-SIM, EAP-AKA, and PEAP
draft-ietf-emu-eap-session-id-07.txt
Abstract
RFC 5247 is updated to define and clarity EAP Session-Id derivation
for multiple EAP methods. The derivation of Session-Id was not given
for EAP-SIM or EAP-AKA when using the fast reconnect exchange instead
of full authentication. The derivation of Session-Id for full
authentication is clarified for both EAP-SIM and EAP-AKA. The
deriviation of Session-Id for PEAP is also given. The definition for
PEAP follows the definition for other TLS-based EAP methods.
Status of this Memo
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Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
DeKok, Alan Proposed Standard [Page 1]
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DeKok, Alan Proposed Standard [Page 2]
INTERNET-DRAFT EAP Session-Id Derivation 3 September 2020
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 for EAP-AKA and EAP-SIM updates ........... 6
3. Session-Id for PEAP ...................................... 7
4. Security Considerations .................................. 7
5. IANA Considerations ...................................... 8
6. References ............................................... 8
6.1. Normative References ................................ 8
6.2. Informative References .............................. 8
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INTERNET-DRAFT EAP Session-Id Derivation 3 September 2020
1. Introduction
EAP [RFC3748] Session-Id derivation has not been defined for EAP-SIM
and EAP-AKA when using the fast reconnect 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 Session-Id derivation was not defined for
EAP-AKA', but [AKAP] now defines it, along with other updates. As
such, the definition for EAP-AKA' is not included here.
Further, the deriviation of Session-Id for full authentication is
clarified, as the text in [RFC5247] is ambiguousl
The IEEE has defined Fast Initial Link Setup (FILS) authentication
[FILS], which needs the EAP Session-Id in order for the EAP Re-
authentication Protocol (ERP) [RFC6696] to work. It is therefore
important to address the existing deficiencies in the definition of
EAP Session-Id.
Finally, [RFC5247] did not define Session-Id for PEAP [MS-PEAP],
[PEAP]. We correct these deficiencies here by updating [RFC5247] with
the Session-Id derivation during fast-reconnect exchange for EAP-SIM
and EAP-AKA; clarfying the Session-Id derivation during full
authentication for EAP-SIM and EAP-AKA; and defining the Session-Id
derivation for PEAP which is the same for both full authentication
and fast reconnect.
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 reconnect exchange for EAP-AKA and EAP-SIM.
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 reconnect, 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, [RFC5247] Appendix A 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
RAND field from the AT_RAND attribute, followed by the contents of
the NONCE_MT field in the AT_NONCE_MT attribute:
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Session-Id = 0x12 || RAND || NONCE_MT
It should say:
EAP-SIM
EAP-SIM is defined in [RFC4186]. When using full authentication,
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.
Where RAND1, RAND2 and RAND3 correspond to the RAND value from the
first, second and third GSM triplet respectively.
When using fast reconnect, 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
contents of the MAC field from the AT_MAC attribute from EAP-
Request/SIM/Reauthentication:
Session-Id = 0x12 || NONCE_S || MAC
which is 33 octets in length.
2.3. Rationale for EAP-AKA and EAP-SIM updates
[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 reconnect case is used since the used
parameters (RAND, AUTN, NONCE_MT) are not used in the fast reconnect
case. Based on [RFC4187] Section 5.2, and similar text in [RFC4186]
Section 5.2, NONCE_S corresponds to RAND and MAC in EAP-Request/AKA-
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Reauthentication and EAP-Request/SIM/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.
This deriviation is done via a random value created by the server,
along with a secret key and the peer's identity. We believe that
this deriviation is secure, though no formal analysis has been done.
3. Session-Id for PEAP
[RFC5247] did not define Session-Id for Microsoft's Protected EAP
(PEAP). For consistency with the EAP-TLS definition given in
[RFC5216] Section 2.3, we define it as:
Session-Id = 0x19 || client.random || server.random
This definition is that same for both full authentication, and for
fast reconnect.
This definition is already in wide-spread use in all known 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 in
[TLS-EAP-TYPES].
4. 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 reconnect with EAP-SIM and EAP-AKA.
The Session-Id definitions given here are unique per session and
unforgeable and unguessable by an outside party, as per the
requirements of [RFC5247] Section 10.
The definitions used here have been widely deployed for years, in
all major EAP implementations. However, we acknowledge that very
little security analysis has been done for these definitions. As a
result, any security issues would result in serious issues for the
Internet as a whole.
These updates do not modify the Security Considerations outlined in
RFC5247.
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5. IANA Considerations
There are no actions for IANA. RFC EDITOR: This section may be
removed before publication.
6. References
6.1. 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,
[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.
6.2. Informative References
[RFC4186]
Haverinen, H. (Ed), Salowey, J., "Extensible Authentication
Protocol Method for Global System for Mobile Communications (GSM)
Subscriber Identity Modules (EAP-SIM)", RFC 4186, January 2006.
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[RFC4187]
Arkko, J., Haverinen, H., "Extensible Authentication Protocol
Method for 3rd Generation Authentication and Key Agreement (EAP-
AKA)", RFC 4187, January 2006.
[RFC6696]
Cao, Z. et al, "EAP Extensions for EAP Re-authentication Protocol
(ERP)", RFC 6696, July 2012.
[AKAP]
Arkko, J., et al, "Improved Extensible Authentication Protocol
Method for 3rd Generation Authentication and Key Agreement (EAP-
AKA')", draft-ietf-emu-rfc5448bis-07.txt, March 2020.
[TLS-EAP-TYPES]
DeKok, A., "TLS-based EAP types and TLS 1.3" draft-dekok-emu-tls-
eap-types-02, April 2020.
[MS-PEAP]
Microsoft, "[MS-PEAP]: Protected Extensible Authentication Protocol
(PEAP)", https://docs.microsoft.com/en-
us/openspecs/windows_protocols/ms-peap/5308642b-90c9-4cc4-beec-
fb367325c0f9
[PEAP]
Andersson, H., et al, "Protected EAP Protocol (PEAP)", draft-
josefsson-pppext-eap-tls-eap-05.txt, September 2002.
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 Jouni's suggestions.
Authors' Addresses
Alan DeKok
The FreeRADIUS Server Project
Email: aland@freeradius.org
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