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Versions: 00 01                                                         
Network Working Group                                     S. Turner, Ed.
Internet-Draft                                                      IECA
Intended status: Standards Track                               L. Berger
Obsoletes: 2747 (if approved)                            LabN Consulting
Expires: October 19, 2013                                M. Jethanandani
                                                                K. Patel
                                                           Cisco Systems
                                                                D. Zhang
                                                          April 17, 2013

          Cryptographic Agility for the RSVP INTEGRITY Object


   This document modifies the RSVP INTEGRITY object to support algorithm
   agility by explicitly indicating the algorithm used.  It also
   provides rationale for the design choices.  Finally, it updates the
   mandatory to implement algorithm.

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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   Copyright (c) 2013 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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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect

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   to this document.  Code Components extracted from this document must
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

1.  Introduction

   RSVP Cryptographic Authentication, defined in [RFC2747] and updated
   [RFC3097], defines the INTEGRITY object format to enable RSVP message
   integrity on a hop-by-hop basis.  It also specifies the MTI
   (mandatory to implement) algorithm, HMAC-MD5 [RFC2104].

   The integrity algorithm used is not indicated in the INTEGRITY object
   and is therefore either negotiated via another mechanism or manually
   configured.  Lacking a negotiation mechanism essentially means the
   algorithm is hard coded.  Hard coding algorithms once fashionable is
   no longer de riqueur.  Instead, protocols needs to support algorithm
   agility because cryptographic protocols weaken over time as
   cryptanalysis against them improves.  This document provides a
   cryptographically agile INTEGRITY object and it also provides
   rationale for the choices.

   Spoiler Alert: The change is to use the unused fields between the
   Flags and Key Identifier fields to indicate the integrity algorithm.

   This document does not change the authentication mechanism (i.e.,
   it's still HMAC-based authentication), but it does change the
   mandatory to implement algorithm.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in RFC
   2119 [RFC2119].

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   Familiarity with [RFC2747] is assumed.

3.  Design Methodology

   This section is informative.  It may or may not be removed in the
   final version.

   HMAC-MD5 may not yet be inappropriate to use [RFC6151], but RSVP
   needs to support algorithm agility in case HMAC-MD5 ever does become

   The solution proposed in s3.2 proposed to reuse the Class Number 4
   instead of defining another Class Number for an INTEGRITYv2 object.
   In order to do this, the algorithm choice needs to be carried in the
   object itself.  Options exist:

     o Use one or more of the unused Flags fields.  A 7-bit fields would
       allow 127 additional algorithms to be specified, with 0
       indicating the existing algorithm.

     o Use the unused byte between the Flags and the Key Identifier.
       This would allow an additional 255 algorithms to be specified.

     o Use a special value in one Key Identifier, Sequence Number of
       Keyed Message Digest and add another field.  This would allow an
       almost infinite number of algorithms to be specified.

   Luckily, there's no requirement to support an infinite number of
   algorithms and besides disrupting the order of the fields seems like
   too much of an implementation burden.

   Co-opting some of the unused bits seems best.  Flags seem more
   generic and it would be better to not take them all up.  Therefore,
   using the byte between the Flags and Key Identifier was chosen.

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4.  Cryptographically Agile INTEGRITY Object

   The same INTEGRITY object type is used for both IPv4 and IPv6.

   The INTEGRITY object has the following format:

         Keyed Message Digest INTEGRITY Object: Class = 4, C-Type = 1

          |    Flags    |  Algorithm  |                           |
          +-------------+-------------+                           +
          |                    Key Identifier                     |
          |                    Sequence Number                    |
          |                                                       |
          |                                                       |
          +                                                       +
          |                                                       |
          +                  Keyed Message Digest                 |
          |                                                       |
          +                                                       +
          |                                                       |

   The Flags, Key Identifier, Sequence Number, and Keyed Message Digest
   fields are as defined in [RFC2747].

   Algorithm indicates the integrity algorithm used.

5.  Mandatory to Implement Algorithm

   [RFC2747] mandates support for HMAC-MD5.  This document specifies the
   mandatory to implement algorithm as HMAC-SHA256 [RFC2104][SHS].

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6.  IANA Considerations

   This document establishes a new sub-registry to the RSVP Class Types
   4 C-Types 1 INTEGRITY registry for integrity algorithms.  The
   assignment policy is Specification Required [RFC5226].  The initial
   table is as follows:

   | Alg Flag | Algorithm Name | Keyed Digest Size (bytes) |
   |        0 | HMAC-MD5       | 16                        |
   |        1 | HMAC-SHA1      | 20                        |
   |        1 | HMAC-SHA224    | 28                        |
   |        3 | HMAC-SHA224    | 32                        |
   |        4 | HMAC-SHA384    | 48                        |
   |        5 | HMAC-SHA512    | 64                        |

7.  Security Considerations


8.  References

8.1.  Normative References

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104, February

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

   [RFC2747]  Baker, F., Lindell, B., and M. Talwar, "RSVP Cryptographic
              Authentication", RFC 2747, January 2000.

   [RFC3097]  Braden, R. and L. Zhang, "RSVP Cryptographic
              Authentication -- Updated Message Type Value", RFC 3097,
              April 2001.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

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   [SHS]      National Institute of Standards and Technology (NIST),
              FIPS Publication 186-3: Digital Signature Standard,
              October 2008.

8.2.  Informative References

   [RFC6151]  Turner, S. and L. Chen, "Updated Security Considerations
              for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
              RFC 6151, March 2011.

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Authors' Addresses

   Lou Berger
   LabN Consulting L.L.C.

   Phone: +1-301-468-9228
   EMail: lberger@labn.net

   Mahesh Jethanandani
   Ciena Corporation
   1741 Technology Drive
   San Jose, CA  95110

   Phone: +1 (408) 436-3313
   Email: mjethanandani@gmail.com

   Keyur Patel
   Cisco Systems Inc.
   170 West Tasman Dr
   San Jose, CA  95134

   Email: keyupate@cisco.com

   Sean Turner (editor)
   IECA, Inc.
   3057 Nutley Street, Suite 106
   Fairfax, Virginia  22031

   Phone: +1 (703) 628-3180
   Email: turners@ieca.com

   Dacheng Zhang
   Huawei Technologies Co., LTD.

   Email: zhangdacheng@huawei.com

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