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Versions: 00 01 02 03                                                   
IPv6 maintenance Working Group (6man)                            F. Gont
Internet-Draft                                                   UK CPNI
Updates: 2460 (if approved)                            December 14, 2011
Intended status: Standards Track
Expires: June 16, 2012


         Security Implications of IPv6 options of Type 10xxxxxx
                draft-gont-6man-ipv6-smurf-amplifier-00

Abstract

   When an IPv6 node processing an IPv6 packet does not support an IPv6
   option whose two-highest-order bits of the Option Type are '10', it
   is required to respond with an ICMPv6 Parameter Problem error
   message, even if the Destination Address of the packet was a
   multicast address.  This feature provides an amplification vector,
   opening the door to an IPv6 version of the 'Smurf' Denial-of-Service
   (DoS) attack found in IPv4 networks.  This document discusses the
   security implications of the aforementioned options, and formally
   updates RFC 2460 such that this attack vector is eliminated.
   Additionally, it describes a number of operational mitigations that
   could be deployed against this attack vector.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may not be modified,
   and derivative works of it may not be created, and it may not be
   published except as an Internet-Draft.

   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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   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 16, 2012.

Copyright Notice

   Copyright (c) 2011 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
   (http://trustee.ietf.org/license-info) 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  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Proposed countermeasures  . . . . . . . . . . . . . . . . . . . 4
     2.1.  Updating RFC 2460 . . . . . . . . . . . . . . . . . . . . . 4
     2.2.  Operational mitigations . . . . . . . . . . . . . . . . . . 4
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9



























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1.  Introduction

   As described in Section 4.2 of [RFC2460], when a node processing an
   IPv6 packet does not support an IPv6 option whose two-highest-order
   bits of the Option Type are '10', it should respond with an ICMPv6
   Parameter Problem error message, even if the Destination Address of
   the packet was a multicast address.  This feature provides an
   amplification vector, opening the door to an IPv6 version of the
   'Smurf' Denial-of-Service (DoS) attack [CERT1998] [RFC6274] found in
   IPv4 networks.

   An attacker could exploit the aforementioned amplification vector by
   sending forged IPv6 packets with the IPv6 address of the victim
   system as the Source Address of his packets, a multicast address as
   the Destination Address, and an unsupported option (with an Option
   Type of '10xxxxxx') in a Destination Options Header.  Upon receipt of
   the forged packet, each processing node would respond with an ICMPv6
   Parameter Problem, code 2, error message, pointing to the unsupported
   option type.  Thus, the systems belonging to the multicast group
   specified by the multicast address contained in the Destination
   Address field would serve as an 'amplifier network'.

      It should be noted that if the multicast RPF check is used (e.g.
      to prevent routing loops), this would prevent an attacker from
      forging the Source Address of a packet to an arbitrary value, thus
      preventing an attacker from launching this attack against a remote
      network.

      Chapter 5 of [Juniper2010] discusses multicast RPF configuration
      for Juniper routers.

   Section 2.1 updates RFC 2460 [RFC2460], such that the aforementioned
   attack vector is eliminated.  Section 2.2 describes a number of
   operational mitigations for the aforementioned attack vector.

   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.  Proposed countermeasures

2.1.  Updating RFC 2460

   Considering the security implications discussed in Section 1, and
   since there are no known legitimate uses of IPv6 options of type
   '10xxxxxx', this document updates RFC 2460 [RFC2460] as follows:

   A node that receives a packet containing an unsupported IPv6 option
   of type '10xxxxxx', MUST process the packet as if the two-highest-
   order bits of the option were '11'.  That is, the packet should be
   dropped, and an ICMPv6 Parameter Problem error message should be sent
   to the Source Address of the packet subject to the ICMPv6 error
   sending rules specified in [RFC4443] (which means that no ICMPv6
   error message must be sent if the Destination Address of the
   offending packet is a multicast address).

2.2.  Operational mitigations

   This section describes a number of operational mitigations that could
   be implemented for the aforementioned attack vector:

   o  Firstly, IPv6 nodes should limit their ICMPv6 traffic.  This is a
      general mitigation technique for any bandwidth-exhaustion attack
      that relies on ICMPv6 traffic.  This could be enforced at the
      hosts themselves, or at any router connecting such hosts to the
      public network.

   o  Secondly, as noted in Section 1 of this document, the multicast
      RPF check enabled such that an attacker cannot forge the Source
      Address of a packet to an arbitrary value, thus preventing an
      attacker from launching this attack against a remote network.



















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3.  IANA Considerations

   There are no IANA registries within this document.  The RFC-Editor
   can remove this section before publication of this document as an
   RFC.














































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4.  Security Considerations

   This document describes how IPv6 options whose two-highest-order bits
   of the Option Type are '10' could possibly be exploited to perform an
   IPv6 version of the 'Smurf' Denial-of-Service (DoS) attack [CERT1998]
   [RFC6274] found in IPv4 networks.  It formally updates RFC 2460
   [RFC2460] such that this attack vector is eliminated., and also
   describes a number of operational mitigations that could be deployed
   against this attack vector.










































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5.  Acknowledgements

   This document is based on the technical report "Security Assessment
   of the Internet Protocol version 6 (IPv6)" [CPNI-IPv6] authored by
   Fernando Gont on behalf of the UK Centre for the Protection of
   National Infrastructure (CPNI).

   Fernando Gont would like to thank CPNI (http://www.cpni.gov.uk) for
   their continued support.










































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6.  References

6.1.  Normative References

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

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

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, "Internet Control
              Message Protocol (ICMPv6) for the Internet Protocol
              Version 6 (IPv6) Specification", RFC 4443, March 2006.

6.2.  Informative References

   [RFC6274]  Gont, F., "Security Assessment of the Internet Protocol
              Version 4", RFC 6274, July 2011.

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

   [CERT1998]
              CERT, "CERT Advisory CA-1998-01: Smurf IP Denial-of-
              Service Attacks", 1998,
              <http://www.cert.org/advisories/CA-1998-01.html>.

   [Juniper2010]
              Juniper, "JunosE Software for E Series Broadband Services
              Routers Multicast Routing Configuration Guide", 2010, <htt
              p://www.juniper.net/techpubs/en_US/junose11.2/
              information-products/topic-collections/
              swconfig-multicast-routing/book-swconfig-multicast.pdf>.
















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Author's Address

   Fernando Gont
   UK CPNI

   Email: fgont@si6networks.com
   URI:   http://www.cpni.gov.uk












































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