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Versions: 00 01 RFC 5095
Network Working Group J. Abley
Internet-Draft Afilias
Updates: 2460, 4294 P. Savola
(if approved) CSC/FUNET
Intended status: Standards Track G. Neville-Neil
Expires: December 28, 2007 Neville-Neil Consulting
June 26, 2007
Deprecation of Type 0 Routing Headers in IPv6
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 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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Deprecation of RH0 . . . . . . . . . . . . . . . . . . . . . . 4
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Ingress Filtering . . . . . . . . . . . . . . . . . . . . . 4
4.2. Firewall Policy . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowlegements . . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Change History . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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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.
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. 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
[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].
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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
IPv6 nodes MUST NOT process RH0 in packets 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, 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].
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 which carry Routing Headers (rather than
specifically blocking type 0, and permitting other types) has very
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serious implications for the future development of IPv6. If even a
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 RH; wide-scale, indescriminate 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 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 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
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.
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.
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[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.
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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
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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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