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Versions: 00 01 02 03 04 05 06 07 RFC 5386

NETWORK WORKING GROUP                                        N. Williams
Internet-Draft                                                       Sun
Expires: August 26, 2006                               February 22, 2006


     Better-Than-Nothing-Security: An Unauthenticated Mode of IPsec
                      draft-ietf-btns-core-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   This document specifies how to use the Internet Key Exchange (IKE)
   protocols, such as IKEv1 and IKEv2, to setup "unauthenticated"
   security associations (SAs) for use with the IPsec Encapsulating
   Security Payload (ESP) and the IPsec Authentication Header (AH).  No
   IKE extensions are needed, but Peer Authorization Database (PAD) and
   Security Policy Database (SPD) extensions are specified.
   Unauthenticated IPsec is herein referred to by its popular acronym,
   "BTNS" (Better Than Nothing Security).




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Table of Contents

   1.    Introduction  . . . . . . . . . . . . . . . . . . . . . . . . 3
   1.1.  Conventions used in this document . . . . . . . . . . . . . . 3
   2.    BTNS  . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.    Security Considerations . . . . . . . . . . . . . . . . . . . 5
   4.    Normative . . . . . . . . . . . . . . . . . . . . . . . . . . 5
         Author's Address  . . . . . . . . . . . . . . . . . . . . . . 6
         Intellectual Property and Copyright Statements  . . . . . . . 7










































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1.  Introduction

   Here we describe how to establish unauthenticated IPsec SAs using
   IKEv1 [RFC2408] [RFC2409] or IKEv2 [RFC4306] and unauthenticated
   public keys.  No new on-the-wire protocol elements are added to IKE
   or IKEv2.

   The [RFC4301] processing model is assumed.

   This document does not define an opportunistic BTNS mode of IPsec
   whereby nodes may fallback on unprotected IP when their peers do not
   support IKE or IKEv2, nor does it describe "leap-of-faith" modes, or
   "connection latching."

   See [I-D.ietf-btns-prob-and-applic] for the applicability and uses of
   BTNS.

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.  BTNS

   The IPsec processing model, IKE and IKEv2 are hereby modified as
   follows:

   o  A new ID type is added, 'PUBLICKEY'; IDs of this type have public
      keys as values.  This ID type is not used on the wire.

   o  A BTNS-specific PAD entry.  This entry is intended to be the last
      entry in the PAD when BTNS is enabled.  A peer that matches no
      other PAD entries is to be "authenticated" by verifying that the
      signature in its AUTH (or SIG) payload in the IKEv2 (or v1)
      exchange with the public key from the peer's CERT payload.  The
      peer's ID MUST then be coerced to be of 'PUBLICKEY' type with the
      peer's public key as its value.

   o  A new flag for SPD entries: 'BTNS_OK'.  Traffic to/from peers that
      match the BTNS PAD entry will only match SPD entries that have the
      BTNS_OK flag set.  The SPD may be searched done by address or by
      ID (of typ PUBLICKEY, of course, for BTNS peers), as per the IPsec
      processing model [RFC4301]; searching by ID in this case requires
      creation of SPD entries that are bound to public key values (this
      could be used to build "leap-of-faith" behaviour, for example).

   Nodes MUST reject IKE_SA proposals from peers that match non-BTNS PAD
   entries but fail to authenticated properly.

   Nodes wishing to be treated as BTNS nodes by their peers SHOULD use
   CERT payloads generated for the purpose (i.e., ephemeral, non-pre-
   shared self-signed certificates or bare RSA public keys).

   Note that nodes may unwittingly match peers' BTNS PAD entries and be
   authenticated as BTNS nodes, as long as they do not match any non-
   BTNS PAD entries.

















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3.  Security Considerations

   Unauthenticated security association negotiation is subject to MITM
   attacks and should be used with care.  Where security infrastructures
   are lacking this may indeed be better than nothing.

   Use with applications that bind authentication at higher network
   layers to secure channels at lower layers may provide one secure way
   to use unauthenticated IPsec, but this is not specified herein.

   [...]

4.  Normative

   [I-D.ietf-btns-prob-and-applic]
              Touch, J., "Problem and Applicability Statement for Better
              Than Nothing Security  (BTNS)",
              draft-ietf-btns-prob-and-applic-00 (work in progress),
              July 2005.

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

   [RFC2408]  Maughan, D., Schneider, M., and M. Schertler, "Internet
              Security Association and Key Management Protocol
              (ISAKMP)", RFC 2408, November 1998.

   [RFC2409]  Harkins, D. and D. Carrel, "The Internet Key Exchange
              (IKE)", RFC 2409, November 1998.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4306]  Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.
















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Author's Address

   Nicolas Williams
   Sun Microsystems
   5300 Riata Trace Ct
   Austin, TX  78727
   US

   Email: Nicolas.Williams@sun.com










































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