IPv6 maintenance Working Group (6man)                            F. Gont
Internet-Draft                                                   UK CPNI
Updates: 4861 (if approved)                                 May 31, 2011
Intended status: Standards Track
Expires: December 2, 2011


  Security Implications of the Use of IPv6 Extension Headers with IPv6
                           Neighbor Discovery
                draft-gont-6man-nd-extension-headers-00

Abstract

   IPv6 Extension Headers with Neighbor Discovery messages can be
   leveraged to circumvent simple local network protections, such as
   "Router Advertisement Guard".  Since there is no legitimate use for
   IPv6 Extension Headers in Neighbor Discovery messages, and such use
   greatly complicates network monitoring and simple security
   mitigations such as RA-Guard, this document proposes that hosts
   silently ignore Neighbor Discovery messages that use IPv6 Extension
   Headers.

Status of this Memo

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   This Internet-Draft will expire on December 2, 2011.

Copyright Notice

   Copyright (c) 2011 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
   Provisions Relating to IETF Documents



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   (http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Specification . . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     5.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     5.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8
































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1.  Introduction

   IPv6 Router Advertisement Guard (RA-Guard) is a mitigation technique
   for attack vectors based on ICMPv6 Router Advertisement messages.
   describes the problem statement of "Rogue IPv6 Router
   Advertisements", and specifies the "IPv6 Router Advertisement Guard"
   functionality.

   [draft-gont-v6ops-ra-guard-evasion] describes how IPv6 Extension
   Headers can be leveraged to circumvent the RA-Guard protection.
   Additionally, the use of Extension Headers (and of the Fragmentation
   Header in particularly) greatly increases the difficulty to monitor
   Neighbor Discovery traffic (e.g., with tools such as NDPMon).

   Since there is no current legitimate use for IPv6 Extension Headers
   in IPv6 Neighbor Discovery packets, and since avoiding their use for
   such packets greatly simplifies monitoring of Neighbor Discovery
   traffic and the possible mitigations for Neighbor Discovery attacks,
   this document proposes that hosts silently ignore Neighbor Discovery
   messages that employ IPv6 Extension Headers.

   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 RFC 2119 [RFC2119].



























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2.  Specification

   Hosts SHOULD silently ignore Neighbor Discovery messages (Neighbor
   Solicitation, Neighbor Advertisement, Router Solcicitation, and
   Router Advertisement messages) that employ IPv6 Extension Headers.














































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3.  Security Considerations

   IPv6 Extension Headers can be leveraged to circumvent network
   monitoring and mechanisms such as RA-Guard
   [draft-gont-v6ops-ra-guard-evasion].  By updating the relevant
   specifications such that IPv6 Extension Headers are not allowed in
   Neighbor Discovery messages, protection of local network against
   Neighbor Discovery attacks, and monitoring of Neighbor Discovery
   traffic is greatly simplified.

   [draft-gont-v6ops-ra-guard-evasion] discusses possible filtering
   rules that could be enforced to mitigate Neighbor Discovery attacks
   that employ IPv6 Extension Headers.






































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4.  Acknowledgements

   This document resulted from the project "Security Assessment of the
   Internet Protocol version 6 (IPv6)" [CPNI-IPv6], carried out by
   Fernando Gont on behalf of the UK Centre for the Protection of
   National Infrastructure (CPNI).  The author would like to thank the
   UK CPNI, for their continued support.












































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5.  References

5.1.  Normative References

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

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

5.2.  Informative References

   [RFC6104]  Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
              Problem Statement", RFC 6104, February 2011.

   [RFC6105]  Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
              Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
              February 2011.

   [draft-gont-v6ops-ra-guard-evasion]
              Gont, F., "IPv6 Router Advertisement Guard (RA Guard)
              Evasion",  IETF Internet Draft,
              draft-gont-v6ops-ra-guard-evasion, work in progress,
              May 2011.

   [CPNI-IPv6]
              Gont, F., "Security Assessment of the Internet Protocol
              version 6 (IPv6)",  UK Centre for the Protection of
              National Infrastructure, (to be published).





















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Author's Address

   Fernando Gont
   Centre for the Protection of National Infrastructure

   Email: fernando@gont.com.ar
   URI:   http://www.gont.com.ar












































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