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Versions: 00 01 02 03                                                   
Network Working Group                                         V. Smyslov
Internet-Draft                                                ELVIS-PLUS
Intended status: Standards Track                           March 3, 2014
Expires: September 4, 2014


            The NULL Authentication Method in IKEv2 Protocol
                draft-smyslov-ipsecme-ikev2-null-auth-01

Abstract

   This document defines the NULL Authentication Method for the IKEv2
   Protocol.  This method provides a way to omit peer authentication in
   IKEv2 and to explicitely indicate it in the protocol run.  This
   method may be used to preserve anonymity or in situations, where no
   trust relationship exists between the parties.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on September 4, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Conventions Used in This Document . . . . . . . . . . . . . 3
   2.  Using the NULL Authentication Method  . . . . . . . . . . . . . 4
     2.1.  Authentication Payload  . . . . . . . . . . . . . . . . . . 4
     2.2.  Identity Payload  . . . . . . . . . . . . . . . . . . . . . 4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   4.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9







































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1.  Introduction

   The Internet Key Exchange Protocol version 2 (IKEv2), specified in
   [RFC5996], provides a way for two parties to perform authenticated
   key exchange.  Mutual authentication is mandatory in the IKEv2, so
   that each party must be authenticated by the other, but
   authentication methods, used by the peers, need not be the same.

   In some situations mutual authentication is undesirable or
   impossible.  For example:

   o  User wants to get anonymous access to some resource.  In this
      situation he/she should be able to authenticate server, but to
      leave out his/her own authentication to prevent anonymity.  In
      this case one-way authentication is desirable.

   o  User wants to get some simple action from remote device.  Consider
      garage door opener: it must authenticate user to open the door,
      but it is not necessary for the user to authenticate the door
      opener.  In this case one-way authentication is sufficient.

   o  Two peers without any trust relationship want to get some level of
      security in their communications.  Without trust relationship they
      cannot prevent active Man-in-the-Middle attacks, but it is still
      possible to prevent passive eavesdropping with opportunistic
      encryption.  In this case they have to perform unauthenticated key
      exchange.

   To meet this needs the document introduces the NULL Authentication
   Method, which is effectively a "dummy" method, that provides no
   authentication.  This allows peer to explicitely indicate to the
   other side that he/she is unwilling or unable to certify his/her
   identity.

1.1.  Conventions Used in This Document

   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.  Using the NULL Authentication Method

   In IKEv2 each peer independently selects the method to authenticate
   himself/herself to the other side.  It means that any peer may choose
   to omit his/her authentication by using the NULL Authentication
   Method.  If it is not acceptable for the peer, he/she MUST return
   AUTHENTICATION_FAILED Notification.  Note, that when initiator uses
   EAP, responder MUST NOT use the NULL Authentication Method (in
   conformance with the section 2.16 of [RFC5996]).

   The NULL Authentication Method affects how Authentication and
   Identity Payloads are formed in IKE_AUTH Exchange.

2.1.  Authentication Payload

   Even when implementation uses the NULL Authentication, the AUTH
   Payload must still be present in IKE_AUTH Exchange and must be
   properly formed, as it cryptographically links IKE_SA_INIT Messages
   with the other Messages sent over IKE SA.

   With the NULL Authentication Method the content of AUTH Payload MUST
   be computed using the syntax for pre-shared secret authentication,
   described in Section 2.15 of [RFC5996].  The values SK_pi and SK_pr
   MUST be used as shared secrets for AUTH Payloads generated by
   Initiator and Responder respectively.  Note, that this is exactly how
   content of the two last AUTH Payloads is calculated in case of using
   non-key generating EAP Method (see Section 2.16 of [RFC5996] for
   details).  The field Auth Method MUST be set to <TBA by IANA>.

2.2.  Identity Payload

   The NULL Authentication Method provides no authentication of the
   party using it.  For that reason Identity Payload content cannot be
   verified by the other party and MUST be ignored by IKE.  As peer
   identity is meaningless in this case, Identification Data SHOULD be
   omited from ID Payload, in which case ID Type MAY be set to any
   value.  Implementations supporting the NULL Authentication Method
   MUST NOT fail if they receive such "empty" ID Payload.













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3.  Security Considerations

   IKEv2 protocol provides mutual authentication of the peers.  If one
   peer uses the NULL Authentication Method, then this peer cannot be
   authenticated by the other side, and it makes authentication in IKEv2
   to become one-way.  If both peers use the NULL Authentication method,
   key exchange becomes unauthenticated, that makes it subject to the
   Man-in-the-Middle attack.

   The identity of the peer using the NULL Authenticated Method cannot
   be verified by the other side and, therefore, MUST NOT be used
   neither for authorization purposes, nor for policy decisions.  All
   peers who use the NULL Authenticated Method should be considered by
   the other party as "guests" and get the least possible privileges.





































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4.  Acknowledgments

   The author would like to thank Paul Wouters and Yaron Sheffer for
   their reviews and valueable comments.















































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5.  IANA Considerations

   This document defines new value in the "IKEv2 Authentication Method"
   registry:

     <TBA>       NULL Authentication Method













































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6.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 5996, September 2010.











































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Author's Address

   Valery Smyslov
   ELVIS-PLUS
   PO Box 81
   Moscow (Zelenograd)  124460
   Russian Federation

   Phone: +7 495 276 0211
   Email: svan@elvis.ru









































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