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Versions: (draft-dekok-emu-eap-session-id) 00 01 02 06 Draft is active
In: Publication_Requested
Network Working Group                                        DeKok, Alan
INTERNET-DRAFT                                                FreeRADIUS
Updates: 5247 (if approved)                                 29 July 2020
Intended status: Standards Track
Expires: January 29, 2021


        EAP Session-Id Derivation for EAP-SIM, EAP-AKA, and PEAP
                  draft-ietf-emu-eap-session-id-06.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

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
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   The list of Internet-Draft Shadow Directories can be accessed at
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   This Internet-Draft will expire on January 29, 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
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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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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 re-
   authentication case. Based on [RFC4187] Section 5.2, and similar text
   in [RFC4186] Section 5.2, NONCE_S corresponds to RAND and MAC in EAP-



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   Request/AKA-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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