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Optimizing BFD Authentication

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Document Type
This is an older version of an Internet-Draft whose latest revision state is "Active".
Authors Mahesh Jethanandani , Ashesh Mishra , Ankur Saxena , Manav Bhatia
Last updated 2015-12-10 (Latest revision 2015-12-08)
Replaces draft-mahesh-bfd-authentication
RFC stream Internet Engineering Task Force (IETF)
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Network Working Group                                    M. Jethanandani
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                               A. Mishra
Expires: June 8, 2016                                  Ciena Corporation
                                                               A. Saxena
                                                               M. Bhatia
                                                          Ionos Networks
                                                        December 6, 2015

                     Optimizing BFD Authentication


   This document describes an optimization to BFD Authentication as
   described in Section 6.7 of BFD [RFC5880].

Requirements Language

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

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 8, 2016.

Copyright Notice

   Copyright (c) 2015 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
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Authentication Mode . . . . . . . . . . . . . . . . . . . . .   3
   3.  NULL Auth TLV . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Authenticating every BFD [RFC5880] packet with a Simple Password, or
   with a MD5 Message-Digest Algorithm [RFC1321] , or Secure Hash
   Algorithm (SHA-1) algorithms is computationally intensive process,
   making it difficult if not impossible to authenticate every packet -
   particularly at faster rates.  Also, the recent escalating series of
   attacks on MD5 and SHA-1 [SHA-1-attack1] [SHA-1-attack2] raise
   concerns about their remaining useful lifetime as outlined in Updated
   Security Considerations for the MD5 Message-Digest and the HMAC-MD5
   Algorithm [RFC6151] and Security Considerations for the SHA-0 and
   SHA-1 Message-Digest Algorithm [RFC6194].  If replaced by stronger
   algorithms, the computational overhead, will make the task of
   authenticating every packet even more difficult to achieve.

   This document proposes that only BFD frames that signal a state
   change in BFD be authenticated.  Rest of the frames can be
   transmitted and received without authentication enabled.  Most frames
   that are transmitted and received have no state change associated
   with them.  Limiting authentication to frames that affect a BFD
   session state allows more sessions to be supported for
   authentication.  Moreover, most BFD frames that signal a state change
   are generally transmitted at a slower interval of 1s leaving enough
   time to compute the hash.

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   Section 2 talks about the changes to authentication mode as described
   in BFD [RFC5880].

2.  Authentication Mode

   The cryptographic authentication mechanisms specified in BFD
   [RFC5880] describes enabling and disabling of authentication as a one
   time operation.  As a security precaution, it mentions that
   authentication state be allowed to change at most once.  Once
   enabled, every packet must have Authentication Bit set and the
   associated Authentication TLV appended.  In addition, it states that
   an implementation SHOULD NOT allow the authentication state to be
   changed based on the receipt of a BFD Control packet.

   This document proposes that the authentication mode be modified to be
   enabled on demand.  Instead of authenticating every packet, BFD peers
   decide which frames need to be authenticated, and authenticate only
   those frames.  For example, the two ends can decide that BFD frames
   that indicate a state change should be authenticated and enable
   authentication on those frames only.  If the two ends have not
   previously negotiated which frames they will transmit or receive with
   authentication enabled, then the BFD session will fail to come up,
   because at least one end will expect every frame to be authenticated.
   The state changes for which authentication is being suggested

      Poll Sequence

      Demand Mode

      BFD packet with the Diag flag set

   Authenticated frames already carry the sequence number.  The rest of
   the frames MUST contain the TLV specified in Section 3.  This enables
   a monotonically increasing sequence number to be carried in each
   frame, and prevents man-in-the-middle from capturing and replaying
   the same frame again.

3.  NULL Auth TLV

   This section describes a new Authentication TLV as:

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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       |          TLV Type             |             TLV Len           |
       |                        Sequence Number                        |
       |                        Sender timestamp                       |

                               NULL Auth TLV


   TLV Type: The TLV Type.  This field MUST be set to <IANA assigned>.

   TLV Length: The length of the NULL Auth TLV, in bytes i.e. 8 bytes

   Sequence Number: is a monotonically increasing number while the
   session state is UP.  Once the session goes down the Sequence number
   SHOULD be set to 0.

   Sender timestamp: is not used by authentication, and is documented to
   be compatible with BFD Stability [I-D.ashesh-bfd-stability].  It
   should be set to 0, and should be ignored by the receiver.

4.  IANA Considerations

   IANA is requested to assign a new Auth Type for the NULL Auth TLV.

   Note to RFC Editor: this section may be removed on publication as an

5.  Security Considerations

   The approach described in this document enhances the ability to
   authentication a BFD session by taking away the onerous requirement
   that every frame be authenticated.  By authenticating frames that
   affect the state of the session, the security of the BFD session is
   maintained.  As such this document does not change the security
   considerations for BFD.

6.  References

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6.1.  Normative References

              National Institute of Standards and Technology, FIPS PUB
              180-2, "The Keyed-Hash Message Authentication Code
              (HMAC)", August 2002.

              National Institute of Standards and Technology, FIPS PUB
              198, "The Keyed-Hash Message Authentication Code (HMAC)",
              March 2002.

              Mishra, A., Jethanandani, M., Saxena, A., Networks, J.,
              Chen, M., and P. Fan, "BFD Stability", draft-ashesh-bfd-
              stability-03 (work in progress), June 2015.

              Bhatia, M., Manral, V., Zhang, D., and M. Jethanandani,
              "BFD Generic Cryptographic Authentication", draft-ietf-
              bfd-generic-crypto-auth-06 (work in progress), April 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC6039]  Manral, V., Bhatia, M., Jaeggli, J., and R. White, "Issues
              with Existing Cryptographic Protection Methods for Routing
              Protocols", RFC 6039, DOI 10.17487/RFC6039, October 2010,

   [RFC6151]  Turner, S. and L. Chen, "Updated Security Considerations
              for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
              RFC 6151, DOI 10.17487/RFC6151, March 2011,

   [RFC6194]  Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
              Considerations for the SHA-0 and SHA-1 Message-Digest
              Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,

6.2.  Informative References

   [Dobb96a]  Dobbertin, H., "Cryptanalysis of MD5 Compress", May 1996.

   [Dobb96b]  Dobbertin, H., "The Status of MD5 After a Recent Attack",
              CryptoBytes", 1996.

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              Lebovitz, G. and M. Bhatia, "Keying and Authentication for
              Routing Protocols (KARP) Design Guidelines", draft-ietf-
              karp-design-guide-10 (work in progress), December 2011.

              Wang, X., Feng, D., Lai, X., and H. Yu, "Collisions for
              Hash Functions MD4, MD5, HAVAL-128 and RIPEMD", August

              National Institute of Standards and Technology, Available
              online at,
              "NIST's Policy on Hash Functions", 2006.

   [RFC1321]  Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
              DOI 10.17487/RFC1321, April 1992,

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997,

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,

   [RFC4822]  Atkinson, R. and M. Fanto, "RIPv2 Cryptographic
              Authentication", RFC 4822, DOI 10.17487/RFC4822, February
              2007, <>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310, February
              2009, <>.

   [RFC5709]  Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
              Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
              Authentication", RFC 5709, DOI 10.17487/RFC5709, October
              2009, <>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,

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   [RFC6234]  Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and SHA-based HMAC and HKDF)", RFC 6234,
              DOI 10.17487/RFC6234, May 2011,

              Wang, X., Yin, Y., and H. Yu, "Finding Collisions in the
              Full SHA-1", 2005.

              Wang, X., Yao, A., and F. Yao, "New Collision Search for
              SHA-1", 2005.

Authors' Addresses

   Mahesh Jethanandani
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134

   Phone: +1 (408) 526-8763

   Ashesh Mishra
   Ciena Corporation
   3939 North 1st Street
   San Jose, CA  95134

   Phone: +1 (408) 904-2114

   Ankur Saxena
   4988 Great America Pkwy
   Santa Clara, CA  95054


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   Manav Bhatia
   Ionos Networks


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