One document matched: draft-gont-6man-ipv6-smurf-amplifier-00.txt
IPv6 maintenance Working Group (6man) F. Gont
Internet-Draft UK CPNI
Updates: 2460 (if approved) December 14, 2011
Intended status: Standards Track
Expires: June 16, 2012
Security Implications of IPv6 options of Type 10xxxxxx
draft-gont-6man-ipv6-smurf-amplifier-00
Abstract
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.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on June 16, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
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
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
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 processing node 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
network.
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.
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 RFC 2119 [RFC2119].
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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 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.
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3. IANA Considerations
There are no IANA registries within this document. The RFC-Editor
can remove this section before publication of this document as an
RFC.
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4. Security Considerations
This document describes how IPv6 options whose two-highest-order bits
of the Option Type are '10' could possibly 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.
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5. Acknowledgements
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.
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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
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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>.
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Author's Address
Fernando Gont
UK CPNI
Email: fgont@si6networks.com
URI: http://www.cpni.gov.uk
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