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Network Working Group                                           J. AbleyRequest for Comments: 5095                                       AfiliasUpdates:2460,4294                                            P. SavolaCategory: Standards Track                                      CSC/FUNET                                                         G. Neville-Neil                                                 Neville-Neil Consulting                                                           December 2007Deprecation of Type 0 Routing Headers in IPv6Status of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   The functionality provided by IPv6's Type 0 Routing Header can be   exploited in order to achieve 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 light of this security concern.Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .22.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . . .33.  Deprecation of RH0  . . . . . . . . . . . . . . . . . . . . . .34.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . . .34.1.  Ingress Filtering . . . . . . . . . . . . . . . . . . . . .34.2.  Firewall Policy . . . . . . . . . . . . . . . . . . . . . .35.  Security Considerations . . . . . . . . . . . . . . . . . . . .46.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .47.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . .48.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .58.1.  Normative References  . . . . . . . . . . . . . . . . . . .58.2.  Informative References  . . . . . . . . . . . . . . . . . .5Abley, et al.               Standards Track                     [Page 1]

RFC 5095                   Deprecation of RH0              December 20071.  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.   A single RH0 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 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 could be used to cause congestion   along arbitrary remote paths and hence act as a denial-of-service   mechanism.  An 88-fold amplification has been demonstrated using this   technique [CanSecWest07].   This attack is particularly serious in that it affects the entire   path between the two exploited nodes, not only the nodes themselves   or their local networks.  Analogous functionality may be found in the   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 each packet.   The severity of this threat is considered to be 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 [Security].  In   2002 a proposal was made to restrict Routing Header processing in   hosts [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   [RFC4942].   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].Abley, et al.               Standards Track                     [Page 2]

RFC 5095                   Deprecation of RH0              December 20072.  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   An IPv6 node that receives a packet with a destination address   assigned to it and that contains an RH0 extension header MUST NOT   execute the algorithm specified in the latter part ofSection 4.4 of   [RFC2460] for RH0.  Instead, such packets MUST be processed according   to the behaviour specified inSection 4.4 of [RFC2460] for a datagram   that includes an unrecognised Routing Type 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 unrecognized Routing Type.   IPv6 implementations are no longer required to implement RH0 in any   way.4.  Operations4.1.  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].   A site security policy intended to protect against attacks using RH0   SHOULD include the implementation of ingress filtering at the site   border.4.2.  Firewall Policy   Blocking all IPv6 packets that carry Routing Headers (rather than   specifically blocking Type 0 and permitting other types) has very   serious implications for the future development of IPv6.  If even aAbley, et al.               Standards Track                     [Page 3]

RFC 5095                   Deprecation of RH0              December 2007   small percentage of deployed firewalls block other types of Routing   Headers by default, it will become impossible in practice to extend   IPv6 Routing Headers.  For example, Mobile IPv6 [RFC3775] relies upon   a Type 2 Routing Header; wide-scale, indiscriminate blocking of   Routing Headers will make Mobile IPv6 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 0 traffic without blocking   other types of Routing Headers.  In addition, the default   configuration MUST permit forwarding of traffic using a Routing   Header other than 0.5.  Security Considerations   The purpose of this document is to deprecate a feature of IPv6 that   has been shown to have undesirable security implications.  Specific   examples of vulnerabilities that 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   inSection 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.  Acknowledgements   This document benefits from the contributions of many IPV6 and V6OPS   working group participants, including Jari Arkko, 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.Abley, et al.               Standards Track                     [Page 4]

RFC 5095                   Deprecation of RH0              December 20078.  References8.1.  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   [Hosts]         Savola, P., "Note about Routing Header Processing on                   IPv6 Hosts", 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.   [RFC4942]       Davies, E., Krishnan, S., and P. Savola, "IPv6                   Transition/Co-existence Security Considerations",RFC 4942, September 2007.   [Security]      Savola, P., "Security of IPv6 Routing Header and Home                   Address Options", Work in Progress, March 2002.Abley, et al.               Standards Track                     [Page 5]

RFC 5095                   Deprecation of RH0              December 2007Authors' 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.comAbley, et al.               Standards Track                     [Page 6]

RFC 5095                   Deprecation of RH0              December 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Abley, et al.               Standards Track                     [Page 7]