Here's a revised candidate -01. As before, I have not submitted this
to the i-d repository, but offer it here first instead in order to
make sure my changes seem reasonable.
Substantive changes include:
+ removed section 3.1 ("Origination"), since hosts will originate
any junk they want, and it's pointless to presume to dictate
otherwise (paraphrasing Jinmei). I left in the comment about hosts
not being required to support RH0 in the introduction, after the line
"This document updates [RFC2460] and [RFC4294]".
+ section 3.2 becomes section 3, and has been re-worked to spell
out the undefined RH type behaviour from 2460, and to be more
specific about which addresses nodes need to check when deciding
whether or not to look for RH0. I have not incorporated the more
conservative OpenBSD/Mac OS X behaviour as a requirement, since it's
not clear to me that such a requirement is reasonable for all nodes
(e.g. for routers).
+ section 5 has been substantially reduced (and its subsections
removed) along the lines suggested by Jinmei. I added a note about
the side-effects of deprecation on benign uses of RH0, and included
mention of the possibility of new, future, safe routing header types
which might fill some of the resulting gap.
I have not corrected the alleged typos such as "recognized" vs.
"recognised", since the latter is a valid example of how we spell
things in my world :-)
Revised text attached. Comments welcome. Apologies for the delay in
getting these edits done; I expect subsequent text wrangling to be
turned around more rapidly.
Joe
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 14, 2007 Neville-Neil Consulting
June 12, 2007
Deprecation of Type 0 Routing Headers in IPv6
draft-ietf-ipv6-deprecate-rh0-01-candidate-01
Status of this Memo
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This Internet-Draft will expire on December 14, 2007.
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 packet amplification 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 the severity of this security concern.
Abley, et al. Expires December 14, 2007 [Page 1]
Internet-Draft Deprecation of RH0 June 2007
This document updates RFC 2460 and RFC 4294.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Deprecation of RH0 . . . . . . . . . . . . . . . . . . . . . . 3
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Ingress Filtering . . . . . . . . . . . . . . . . . . . . . 4
4.2. Packet Filtering . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowlegements . . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Change History . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 8
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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.
The functionality provided by IPv6's Type 0 Routing Header can be
exploited in order to achieve packet amplification 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 the severity of this security concern.
This document updates [RFC2460] and [RFC4294].
IPv6 implementations are no longer required to implement RH0 in any
way.
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.
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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 policy intended to protect against packets containing RH0
should be constructed such that routing headers of other types (which
may well have legitimate and benign applications) are handled on
their own merits. For example, discarding all packets with any type
of routing header simply as a reaction to the problems with RH0 is
inappropriate, and may hamper future functionality designed using
non-type 0 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 of any
Routing Headers on IPv6 routers, without explicitly checking the
Routing Header type, is strongly discouraged.
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 single RH0 may contain multiple waypoint 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
Abley, et al. Expires December 14, 2007 [Page 4]
Internet-Draft Deprecation of RH0 June 2007
IPv4 source route option, but the opportunities for abuse are greater
with RH0 due to the ability to specify many more waypoints in each
packet.
The severity of the threat is considered to be sufficient to warrant
deprecation of RH0 entirely. This has the unfortunate side-effect
that benign use cases for RH0 are eliminated along with the potential
security hazards; such applications may be facilitated in the future
by new routing header specifications which do not suffer from RH0's
problems.
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]. 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].
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 and V6OPS
orking group participants, including Jari Arkko, Arnaud Ebalard, Tim
Enos, Brian Haberman, Jun-ichiro itojun HAGINO, Bob Hinden, JINMEI
Tatuya, David Malone, Jeroen Massar, Dave Thaler and Guillaume
Valadon.
8. References
Abley, et al. Expires December 14, 2007 [Page 5]
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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.
Abley, et al. Expires December 14, 2007 [Page 6]
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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.
Authors' Addresses
Joe Abley
Afilias Canada Corp.
Suite 204, 4141 Yonge Street
Toronto, ON M2P 2A8
Canada
Phone: +1 416 673 4176
Email: [EMAIL PROTECTED]
Pekka Savola
CSC/FUNET
Espoo,
Finland
Email: [EMAIL PROTECTED]
George Neville-Neil
Neville-Neil Consulting
2261 Market St. #239
San Francisco, CA 94114
USA
Email: [EMAIL PROTECTED]
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