Security Implications Of IPv6 Options Of Type 10xxxxxx Revision 01
Authored by Fernando Gont
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.
Changes: Updated version for 01/2013.
tags | paper
SHA-256 | fb4961bf8357488cad14ec9267d3578def97ef7eb554541ecd35f6f1114d3f2c
IPv6 maintenance Working Group (6man)                            F. Gont
Internet-Draft                                    SI6 Networks / UTN-FRH
Updates: 2460 (if approved)                                       W. Liu
Intended status: Standards Track                     Huawei Technologies
Expires: July 15, 2013                                  January 11, 2013
Security Implications of IPv6 options of Type 10xxxxxx
draft-gont-6man-ipv6-smurf-amplifier-01
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.
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and derivative works of it may not be created, and it may not be
published except as an Internet-Draft.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 15, 2013.
Gont & Liu                Expires July 15, 2013                 [Page 1]
Internet-Draft        IPv6 options of Type 10xxxxxx         January 2013
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.
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
Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9
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 receiving host 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
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.
document are to be interpreted as described in RFC 2119 [RFC2119].
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 could be 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.
There are no IANA registries within this document.  The RFC-Editor
can remove this section before publication of this document as an
RFC.
This document describes how IPv6 options whose two-highest-order bits
of the Option Type are '10' could 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.
The authors would like to thank (in alphabetical order) Joel Halpern,
for providing valuable comments on earlier versions of this document.
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.
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
[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>.
Fernando Gont
SI6 Networks / UTN-FRH
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires  1706
Email: fgont@si6networks.com
URI:   http://www.si6networks.com
Will Liu
Bantian, Longgang District
Shenzhen  518129
P.R. China
Email: liushucheng@huawei.com