Network Working Group                                           J. Abley
Internet-Draft                                                   Afilias
Updates: 2460 (if approved) 2460, 4294                                            P. Savola
(if approved)                                                  CSC/FUNET
Intended status: Standards Track                               CSC/FUNET
Expires: November 17, 2007                         G. Neville-Neil
Expires: December 28, 2007                       Neville-Neil Consulting
                                                            May 16,
                                                           June 26, 2007

             Deprecation of Type 0 Routing Headers in IPv6
                    draft-ietf-ipv6-deprecate-rh0-00
                    draft-ietf-ipv6-deprecate-rh0-01

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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The functionality provided by IPv6's Type 0 Routing Header can be
   exploited in order to perform remote network discovery, to bypass
   firewalls and to achieve packet traffic amplification over a remote
   path for the purposes of generating denial-of-service traffic.  This
   document updates the IPv6 specification to deprecate the use of IPv6
   Type 0 Routing Headers, in
   the light of these this security concerns.

   This document updates RFC 2460. concern.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
   3.  Deprecation of RH0  . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  Origination . . . . . . . . . . . . . . . . . . . . . . . . 3
     3.2.  Processing  . . . . . . . . . . . . . . . . . . . . . . . . 3 4
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4
     4.1.  Ingress Filtering . . . . . . . . . . . . . . . . . . . . . 3 4
     4.2.  Packet Filtering  Firewall Policy . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 5
   7.  Acknowlegements . . . . . . . . . . . . . . . . . . . . . . . . 4 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5 6
   Appendix A.  Change History . . . . . . . . . . . . . . . . . . . . 6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6 7
   Intellectual Property and Copyright Statements  . . . . . . . . . . 7 9

1.  Introduction

   [RFC2460] defines an IPv6 extension header called "Routing Header",
   identified by a Next Header value of 43 in the immediately preceding
   header.  A particular Routing Header subtype denoted as "Type 0" is
   also defined.  Type 0 Routing Headers are referred to as "RH0" in
   this document.

   Use of

   A single RH0 has been shown may contain multiple intermediate node addresses, and
   the same address may be included more than once in the same RH0.
   This allows a packet to have unpleasant security implications,
   some be constructed such that it will oscillate
   between two RH0-processing hosts or routers many times.  This allows
   a stream of packets from an attacker to be amplified along the path
   between two remote routers, which are summarised in Section 5. could be used to cause congestion
   along arbitrary remote paths and hence act as a denial-of-service
   mechanism. 88-fold amplification has been demonstrated using this
   technique [CanSecWest07].

   This document deprecates attack is particularly serious in that it affects the use of RH0.

   This document updates [RFC2460].

2.  Definitions

   RH0 entire
   path between the two exploited nodes, not only the nodes themselves
   or their local networks.  Analogous functionality may be found in this document denotes the IPv6 Extension Header type 43
   ("Routing Header") variant 0 ("Type 0 Routing Header"), as defined
   IPv4 source route option, but the opportunities for abuse are greater
   with RH0 due to the ability to specify many more intermediate node
   addresses in
   [RFC2460]. each packet.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in severity of this
   document are threat is considered to be interpreted as described in [RFC2119].

3.  Deprecation sufficient to warrant
   deprecation of RH0 entirely.  A side-effect is that this also
   eliminates benign RH0 use-cases; however, such applications may be
   facilitated by future Routing Header specifications.

   Potential problems with RH0 were identified in 2001
   [I-D.savola-ipv6-rh-ha-security].  In 2002 a proposal was made to
   restrict Routing Header processing in hosts
   [I-D.savola-ipv6-rh-hosts].  These efforts resulted in the
   modification of the Mobile IPv6 specification to use the type 2
   Routing Header instead of RH0 [RFC3775].  Vishwas Manral identified
   various risks associated with RH0 in 2006 including the amplification
   attack; several of these vulnerabilities (together with other issues)
   were later documented in [I-D.ietf-v6ops-security-overview].

   A treatment of the operational security implications of RH0 was
   presented by Philippe Biondi and Arnaud Ebalard at the CanSecWest
   conference in Vancouver, 2007 [CanSecWest07].  This presentation
   resulted in widespread publicity for the risks associated with RH0.

   This document updates [RFC2460] and [RFC4294].

2.  Definitions

   RH0 in this document denotes the IPv6 Extension Header type 43
   ("Routing Header") variant 0 ("Type 0 Routing Header"), as defined in
   [RFC2460].

   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].

3.  Deprecation of RH0

3.1.  Origination

   IPv6 nodes MUST NOT originate IPv6 packets containing RH0.

3.2.  Processing

   IPv6 nodes MUST NOT process RH0 in packets addressed whose destination address
   in the IPv6 header is an address assigned to them.  Such packets MUST
   be processed according to the behaviour specified in Section 4.4 of
   [RFC2460] for a datagram which includes an unrecognised Routing Type value.
   value, namely:

      If Segments Left is zero, the node must ignore the Routing header
      and proceed to process the next header in the packet, whose type
      is identified by the Next Header field in the Routing header.

      If Segments Left is non-zero, the node must discard the packet and
      send an ICMP Parameter Problem, Code 0, message to the packet's
      Source Address, pointing to the unrecognised Routing Type.

   IPv6 implementations are no longer required to implement RH0 in any
   way.

4.  Operations

4.1.  Ingress Filtering

   It is to be expected that it will take some time before all IPv6
   nodes are updated to remove support for RH0.  Some of the uses of RH0
   described in [CanSecWest07] can be mitigated using ingress filtering,
   as recommended in [RFC2827] and [RFC3704].

4.2.  Packet Filtering

   Firewall

   A site security policy intended to protect against packets containing attacks using RH0
   should be constructed such that routing headers
   SHOULD include the implementation of other types (which
   may well have legitimate and benign applications) are handled on
   their own merits.  For example, discarding ingress filtering at the site
   border.

4.2.  Firewall Policy

   Blocking all IPv6 packets with any which carry Routing Headers (rather than
   specifically blocking type 0, and permitting other types) has very
   serious implications for the future development of routing header simply as IPv6.  If even a reaction
   small percentage of deployed firewalls block other types of routing
   headers by default, it will become impossible in practice to the problems with RH0 is
   inappropriate, and may hamper future functionality designed using
   non-type 0 extend
   IPv6 routing headers.  For example, Mobile IPv6 uses the type 2
   Routing Header [RFC3775].

   Where filtering capabilities do not facilitate matching specific
   types of Routing Headers, filtering based on the presence [RFC3775] relies upon
   a type-2 RH; wide-scale, indescriminate blocking of any Routing Headers on
   will make Mobile IPv6 routers, regardless undeployable.

   Firewall policy intended to protect against packets containing RH0
   MUST NOT simply filter all traffic with a routing header; it must be
   possible to disable forwarding of type, is strongly
   discouraged. type 0 traffic without blocking
   other types of routing headers.  In addition, the default
   configuration MUST permit forwarding of traffic using a RH other than
   0.

5.  Security Considerations

   The purpose of this document is to deprecate a feature of IPv6 which
   has been shown to have serious undesirable security implications.  Specific
   examples of vulnerabilities which are facilitated by the availability
   of RH0 can be found in [CanSecWest07].  In particular, RH0 provides a
   mechanism for traffic amplification, which might be used as a denial-
   of-service attack.  A description of this functionality can be found
   in Section 1.

6.  IANA Considerations

   The IANA registry "Internet Protocol Version 6 (IPv6) Parameters"
   should be updated to reflect that variant 0 of IPv6 header-type 43
   ("Routing Header") is deprecated.

7.  Acknowlegements

   Potential problems with Routing Headers were identified in 2001
   [I-D.savola-ipv6-rh-ha-security].  In 2002 a proposal was made to
   restrict Routing Header processing in hosts
   [I-D.savola-ipv6-rh-hosts].  These efforts did not gain sufficient
   momentum to change the IPv6 specification, but resulted in the
   modification of the Mobile IPv6 specification to use the type 2
   Routing Header instead of RH0 [RFC3775].  Routing Header issues were
   later documented in [I-D.ietf-v6ops-security-overview].

   An eloquent and useful description of the operational security
   implications of RH0 was presented by Philippe Biondi and Arnaud
   Ebalard at the CanSecWest conference in Vancouver, 2007
   [CanSecWest07].  This presentation resulted in widespread publicity
   for the risks associated with RH0.

   This document also benefits from the contributions of IPv6 many IPV6 and V6OPS
   orking
   working group participants, including Jari Arkko, Arbaud Arnaud Ebalard, Tim
   Enos, Brian Haberman, Jun-ichiro itojun HAGINO, Bob Hinden, Thomas
   Narten, JINMEI Tatuya, David Malone, Jeroen Massar, Dave Thaler and
   Guillaume Valadon.

8.  References

8.1.  Normative References

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

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

   [RFC4294]  Loughney, J., "IPv6 Node Requirements", RFC 4294,
              April 2006.

8.2.  Informative References

   [CanSecWest07]
              BIONDI, P. and A. EBALARD, "IPv6 Routing Header Security",
              CanSecWest Security Conference 2007, April 2007.

              http://www.secdev.org/conf/IPv6_RH_security-csw07.pdf

   [I-D.ietf-v6ops-security-overview]
              Davies, E., "IPv6 Transition/Co-existence Security
              Considerations", draft-ietf-v6ops-security-overview-06
              (work in progress), October 2006.

   [I-D.savola-ipv6-rh-ha-security]
              Savola, P., "Security of IPv6 Routing Header and Home
              Address Options", draft-savola-ipv6-rh-ha-security-02
              (work in progress), March 2002.

   [I-D.savola-ipv6-rh-hosts]
              Savola, P., "Note about Routing Header Processing on IPv6
              Hosts", draft-savola-ipv6-rh-hosts-00 (work in progress),
              February 2002.

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.

   [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
              Networks", BCP 84, RFC 3704, March 2004.

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

Appendix A.  Change History

   This section to be removed prior to publication.

   00 Strawman, draft-jabley-ipv6-rh0-is-evil, circulated to provoke
      discussion.

   01 Clarified Section 3; presented more options in Section 4; added
      Pekka and George as authors.  This document version was not widely
      circulated.

   00 Renamed, draft-ietf-ipv6-deprecate-rh0, a candidate working group
      document.

   01-candidate-00  Incorporated text summarising some of the unwelcome
      uses of RH0; added some clariying text describing deprecation;
      modified some ambiguous text in Section 4.2; added "Updates:
      4294".

   01-candidate-01  Incorporated contributions from working group:
      substantially reduced Section 5; clarified wording in Section 3.

   01-candidate-02  Moved description of traffic amplification to
      Section 1, and inserted a corresponding cross-reference in
      Section 5.  Strengthened the language in Section 4.2 along the
      lines suggested by Thomas Narten.  Small typos corrected.  Added a
      further sentence in Section 4.1 intended to act as further
      encouragement for operators to implement [RFC3704].

   01 Minor wordsmithing; removed some subjective language; adopted
      "intermediate node" nomenclature instead of "waypoint"; shifted
      some history from Section 7 to Section 1.

Authors' Addresses

   Joe Abley
   Afilias Canada Corp.
   Suite 204, 4141 Yonge Street
   Toronto, ON  M2P 2A8
   Canada

   Phone: +1 416 673 4176
   Email: jabley@ca.afilias.info
   Pekka Savola
   CSC/FUNET
   Espoo,
   Finland

   Email: psavola@funet.fi

   George Neville-Neil
   Neville-Neil Consulting
   2261 Market St. #239
   San Francisco, CA  94114
   USA

   Email: gnn@neville-neil.com

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