draft-ietf-v6ops-ra-guard-implementation-02.txt   draft-ietf-v6ops-ra-guard-implementation-03.txt 
IPv6 Operations Working Group (v6ops) F. Gont IPv6 Operations Working Group (v6ops) F. Gont
Internet-Draft UK CPNI Internet-Draft UK CPNI
Intended status: BCP March 8, 2012 Intended status: BCP May 11, 2012
Expires: September 9, 2012 Expires: November 12, 2012
Implementation Advice for IPv6 Router Advertisement Guard (RA-Guard) Implementation Advice for IPv6 Router Advertisement Guard (RA-Guard)
draft-ietf-v6ops-ra-guard-implementation-02 draft-ietf-v6ops-ra-guard-implementation-03
Abstract Abstract
The IPv6 Router Advertisement Guard (RA-Guard) mechanism is commonly The IPv6 Router Advertisement Guard (RA-Guard) mechanism is commonly
employed to mitigate attack vectors based on forged ICMPv6 Router employed to mitigate attack vectors based on forged ICMPv6 Router
Advertisement messages. Many existing IPv6 deployments rely on RA- Advertisement messages. Many existing IPv6 deployments rely on RA-
Guard as the first line of defense against the aforementioned attack Guard as the first line of defense against the aforementioned attack
vectors. However, some implementations of RA-Guard have been found vectors. However, some implementations of RA-Guard have been found
to be prone to circumvention by employing IPv6 Extension Headers. to be prone to circumvention by employing IPv6 Extension Headers.
This document describes the evasion techniques that affect the This document describes the evasion techniques that affect the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 9, 2012. This Internet-Draft will expire on November 12, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Evasion techniques for some Router Advertisement Guard (RA 2. Evasion techniques for some Router Advertisement Guard (RA
Guard) implementations . . . . . . . . . . . . . . . . . . . . 4 Guard) implementations . . . . . . . . . . . . . . . . . . . . 4
2.1. Attack Vector based on IPv6 Extension Headers . . . . . . 4 2.1. Attack Vector based on IPv6 Extension Headers . . . . . . 4
2.2. Attack vector based on IPv6 fragmentation . . . . . . . . 4 2.2. Attack vector based on IPv6 fragmentation . . . . . . . . 4
3. RA-Guard implementation advice . . . . . . . . . . . . . . . . 8 3. RA-Guard implementation advice . . . . . . . . . . . . . . . . 8
4. Other Implications . . . . . . . . . . . . . . . . . . . . . . 10 4. Other Implications . . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . . 13 7.1. Normative References . . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . . 13 7.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix A. Changes from previous versions of the draft (to Appendix A. Assessment tools . . . . . . . . . . . . . . . . . . 16
be removed by the RFC Editor before publication Appendix B. Advice and guidance to vendors . . . . . . . . . . . 17
of this document as a RFC . . . . . . . . . . . . . . 15
A.1. Changes from
draft-ietf-v6ops-ra-guard-implementation-00 . . . . . . . 15
A.2. Changes from
draft-gont-v6ops-ra-guard-implementation-01 . . . . . . . 15
A.3. Changes from
draft-gont-v6ops-ra-guard-implementation-00 . . . . . . . 15
A.4. Changes from draft-gont-v6ops-ra-guard-evasion-01 . . . . 15
Appendix B. Assessment tools . . . . . . . . . . . . . . . . . . 16
Appendix C. Advice and guidance to vendors . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
IPv6 Router Advertisement Guard (RA-Guard) is a mitigation technique IPv6 Router Advertisement Guard (RA-Guard) is a mitigation technique
for attack vectors based on ICMPv6 Router Advertisement messages. for attack vectors based on ICMPv6 Router Advertisement messages.
[RFC6104] describes the problem statement of "Rogue IPv6 Router [RFC6104] describes the problem statement of "Rogue IPv6 Router
Advertisements", and [RFC6105] specifies the "IPv6 Router Advertisements", and [RFC6105] specifies the "IPv6 Router
Advertisement Guard" functionality. Advertisement Guard" functionality.
The basic concept behind RA-Guard is that a layer-2 device filters The concept behind RA-Guard is that a layer-2 device filters ICMPv6
ICMPv6 Router Advertisement messages, according to a number of Router Advertisement messages, according to a number of different
different criteria. The most basic filtering criterion is that criteria. The most basic filtering criterion is that Router
Router Advertisement messages are discarded by the layer-2 device Advertisement messages are discarded by the layer-2 device unless
unless they are received on a specified port of the layer-2 device. they are received on a specified port of the layer-2 device.
Clearly, the effectiveness of the RA Guard mitigation relies on the Clearly, the effectiveness of the RA Guard mitigation relies on the
ability of the layer-2 device to identify ICMPv6 Router Advertisement ability of the layer-2 device to identify ICMPv6 Router Advertisement
messages. messages.
Some popular RA-Guard implementations have been found to be easy to Some popular RA-Guard implementations have been found to be easy to
circumvent by employing IPv6 extension headers [CPNI-IPv6]. This circumvent by employing IPv6 extension headers [CPNI-IPv6]. This
document describes such evasion techniques, and provides advice to document describes such evasion techniques, and provides advice to
RA-Guard implementers such that the aforementioned evasion vectors RA-Guard implementers such that the aforementioned evasion vectors
can be eliminated. can be eliminated.
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"Hdr Ext Len" field of the first Destination Options header is "Hdr Ext Len" field of the first Destination Options header is
present in the first fragment (rather than the second). present in the first fragment (rather than the second).
3. RA-Guard implementation advice 3. RA-Guard implementation advice
The following filtering rules MUST be implemented as part of an "RA- The following filtering rules MUST be implemented as part of an "RA-
Guard" implementation on those ports that are not allowed to send Guard" implementation on those ports that are not allowed to send
ICMPv6 Router Advertisement messages, such that the vulnerabilities ICMPv6 Router Advertisement messages, such that the vulnerabilities
discussed in this document are eliminated: discussed in this document are eliminated:
1. When trying to identify an ICMPv6 Router Advertisement message, 1. If the IPv6 Source Address of the packet is not a link-local
follow the IPv6 header chain, enforcing a limit on the maximum address (fe80::/10), pass the packet.
number of Extension Headers that is allowed for each packet. If
such limit is hit before the upper-layer protocol is identified,
silently drop the packet.
2. If the packet is identified to be an ICMPv6 Router Advertisement Section 6.1.2 of [RFC4861] requires nodes to discard Router
message, silently drop the packet. Advertisement messages if their IPv6 Source Address is not a
link-local address.
3. If the layer-2 device is unable to identify whether the packet is 2. If the Hop Limit is not 255, pass the packet.
Section 6.1.2 of [RFC4861] requires nodes to discard Router
Advertisement messages if their Hop Limit is not 255.
3. Try to identify whether the packet is an ICMPv6 Router
Advertisement message, by parsing the IPv6 header chain. When
doing so, enforce a limit on the maximum number of Extension
Headers that is allowed for each packet, and if such limit is hit
before the upper-layer protocol is identified, drop the packet.
[RFC6564] specifies a uniform format for IPv6 Extension
Header, thus meaning that an IPv6 node should be able to parse
an IPv6 header chain even if it contains Extension Headers
that are not currently supported by that node.
4. If the layer-2 device is unable to identify whether the packet is
an ICMPv6 Router Advertisement message or not (i.e., the packet an ICMPv6 Router Advertisement message or not (i.e., the packet
is a first-fragment, and the necessary information is missing), is a first-fragment, and the necessary information is missing),
the IPv6 Source Address of the packet is a link-local address or
the unspecified address (::), and the Hop Limit is 255, silently
drop the packet. drop the packet.
Note: This rule should only be applied to non-fragmented IPv6 Note: This rule should only be applied to non-fragmented IPv6
datagrams and IPv6 fragments with a Fragment Offset of 0 (non- datagrams and IPv6 fragments with a Fragment Offset of 0 (non-
first fragments can be safely passed, since they will never first fragments can be safely passed, since they will never
reassemble into a complete datagram if they are part of a reassemble into a complete datagram if they are part of a
Router Advertisement received on a port where such packets are Router Advertisement received on a port where such packets are
not allowed). not allowed).
4. In all other cases, pass the packet as usual. 5. If the packet is identified to be an ICMPv6 Router Advertisement
message, drop the packet.
6. In all other cases, pass the packet as usual.
Note: For the purpose of enforcing the RA-Guard filtering policy, Note: For the purpose of enforcing the RA-Guard filtering policy,
an ESP header [RFC4303] should be considered to be an "upper-layer an ESP header [RFC4303] should be considered to be an "upper-layer
protocol" (that is, it should be considered the last header in the protocol" (that is, it should be considered the last header in the
IPv6 header chain). This means that packets employing ESP would IPv6 header chain). This means that packets employing ESP would
be passed by the RA-Guard device to the intended destination. If be passed by the RA-Guard device to the intended destination. If
the destination host does not have a security association with the the destination host does not have a security association with the
sender of the aforementioned IPv6 packet, the packet would be sender of the aforementioned IPv6 packet, the packet would be
dropped. Otherwise, if the packet is considered valid by the dropped. Otherwise, if the packet is considered valid by the
IPsec implementation at the receiving host and encapsulates a IPsec implementation at the receiving host and encapsulates a
Router Advertisement message, it is up to the receiving host what Router Advertisement message, it is up to the receiving host what
to do with such packet. to do with such packet.
In order to protect current end-node IPv6 implementations, Rule #3 If a packet is dropped due to this filtering policy, then the packet
drop event SHOULD be logged. The logging mechanism SHOULD include a
drop counter dedicated to RA-Guard packet drops.
In order to protect current end-node IPv6 implementations, Rule #4
has been defined as a default rule to drop packets that cannot be has been defined as a default rule to drop packets that cannot be
positively identified as RA packets or not (perhaps due to the fact positively identified as not being Router Advertisement (RA) messages
that it contains fragments that do not contain the entire IPv6 header (possibly because the packet contains fragments that do not contain
chain). This means that, at least in theory, RA-Guard could result the entire IPv6 header chain). This means that, at least in theory,
in false-positive blocking of some legitimate non-RA packets that RA-Guard could result in false-positive blocking of some legitimate
could not be positively identified as being non-RA. In order to non-RA packets that could not be positively identified as being
reduce the likelihood of false positives, Rule #3 also requires that non-RA. In order to reduce the likelihood of false positives, Rule
an RA-Guard implementation check, before dropping an unidentifiable #1 and Rule #2 require that packets that would not pass the required
packet, that it has an IPv6 Source Address that is a link-local validation checks for RA messages (Section 6.1.2 of [RFC4861]) be
address or the unspecified address (::), and that the Hop Limit is passed without further inspection. In any case, as noted in
255. In any case, as noted in
[I-D.gont-6man-oversized-header-chain], IPv6 packets that fail to [I-D.gont-6man-oversized-header-chain], IPv6 packets that fail to
include the entire IPv6 header chain are anyway unlikely to survive include the entire IPv6 header chain are anyway unlikely to survive
in real networks. Whilst currently legitimate from a specifications in real networks. Whilst currently legitimate from a specifications
standpoint, they are virtually impossible to police with state-less standpoint, they are virtually impossible to police with state-less
filters and firewalls, and are hence likely to be blocked by such filters and firewalls, and are hence likely to be blocked by such
filters and firewalls. filters and firewalls.
This filtering policy assumes that host implementations require that This filtering policy assumes that host implementations require that
the IPv6 Source Address of ICMPv6 Router Advertisement messages be a the IPv6 Source Address of ICMPv6 Router Advertisement messages be a
link-local address, and that they discard the packet if this check link-local address, and that they discard the packet if this check
fails, as required by the current IETF specifications [RFC4861]. fails, as required by the current IETF specifications [RFC4861].
Additionally, it assumes that hosts require the Hop Limit of Neighbor Additionally, it assumes that hosts require the Hop Limit of Neighbor
Discovery messages to be 255, and discard those packets otherwise. Discovery messages to be 255, and discard those packets otherwise.
Finally, note that the aforementioned filtering rules implicitly The aforementioned filtering rules implicitly handle the case of
handle the case of fragmented packets: if the RA-Guard device fails fragmented packets: if the RA-Guard device fails to identify the
to identify the upper-layer protocol as a result of the use of upper-layer protocol as a result of the use of fragmentation, the
fragmentation, the corresponding packets would be silently dropped. corresponding packets would be dropped.
Finally, we note that IPv6 implementations that allow overlapping
fragments (i.e. that do not comply with [RFC5722]) might still be
subject of RA-based attacks. However, a recent assessment of IPv6
implementations [SI6-FRAG] with respect to their fragment reassembly
policy seems to indicate that most current implementations comply
with [RFC5722].
4. Other Implications 4. Other Implications
A similar concept to that of "RA-Guard" has been implemented for A similar concept to that of "RA-Guard" has been implemented for
protecting against forged DHCPv6 messages. Such protection can be protecting against forged DHCPv6 messages. Such protection can be
circumvented with the same techniques discussed in this document, and circumvented with the same techniques discussed in this document, and
the counter-measures for such evasion attack are analogous to those the counter-measures for such evasion attack are analogous to those
described in Section 3 of this document. described in Section 3 of this document.
5. Security Considerations 5. Security Considerations
This document describes a number of techniques that have been found This document describes a number of techniques that have been found
to be effective to circumvent popular RA-Guard implementations, and to be effective to circumvent popular RA-Guard implementations, and
provides advice to RA-Guard implementations such that those evasion provides advice to RA-Guard implementations such that those evasion
vulnerabilities are eliminated. vulnerabilities are eliminated.
As noted in Section 3, IPv6 implementations that allow overlapping
fragments (i.e. that do not comply with [RFC5722]) might still be
subject of RA-based attacks. However, most current
implementations seem to comply with [RFC5722].
We note that if an attacker sends a fragmented Router Advertisement We note that if an attacker sends a fragmented Router Advertisement
message on a port not allowed to send such packets, the first- message on a port not allowed to send such packets, the first-
fragment would be dropped, and the rest of the fragments would be fragment would be dropped, and the rest of the fragments would be
passed. This means that the victim node would tie memory buffers for passed. This means that the victim node would tie memory buffers for
the aforementioned fragments, which would never reassemble into a the aforementioned fragments, which would never reassemble into a
complete datagram. If a large number of such packets were sent by an complete datagram. If a large number of such packets were sent by an
attacker, and the victim node failed to implement proper resource attacker, and the victim node failed to implement proper resource
management for the fragment reassembly buffer, this could lead to a management for the fragment reassembly buffer, this could lead to a
Denial of Service (DoS). However, this does not really introduce a Denial of Service (DoS). However, this does not really introduce a
new attack vector, since an attacker could always perform the same new attack vector, since an attacker could always perform the same
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these attacks would be to prohibit the use of IPv6 fragmentation with these attacks would be to prohibit the use of IPv6 fragmentation with
Router Advertisement messages (as proposed by Router Advertisement messages (as proposed by
[I-D.gont-6man-nd-extension-headers]), such that the RA-Guard [I-D.gont-6man-nd-extension-headers]), such that the RA-Guard
functionality is easier to implement. However, since such mitigation functionality is easier to implement. However, since such mitigation
would require an update to existing implementations, it cannot be would require an update to existing implementations, it cannot be
relied upon in the short or near term. relied upon in the short or near term.
6. Acknowledgements 6. Acknowledgements
The author would like to thank Ran Atkinson, Karl Auer, Robert The author would like to thank Ran Atkinson, Karl Auer, Robert
Downie, Washam Fan, David Farmer, Marc Heuse, Ray Hunter, Simon Downie, Washam Fan, David Farmer, Marc Heuse, Nick Hilliard, Ray
Perreault, Arturo Servin, and Gunter van de Velde, for providing Hunter, Simon Perreault, Arturo Servin, Gunter van de Velde, James
valuable comments on earlier versions of this document. Woodyatt, and Bjoern A. Zeeb, for providing valuable comments on
earlier versions of this document.
The author would like to thank Arturo Servin, who presented this The author would like to thank Arturo Servin, who presented this
document at IETF 81. document at IETF 81.
This document resulted from the project "Security Assessment of the This document resulted from the project "Security Assessment of the
Internet Protocol version 6 (IPv6)" [CPNI-IPv6], carried out by Internet Protocol version 6 (IPv6)" [CPNI-IPv6], carried out by
Fernando Gont on behalf of the UK Centre for the Protection of Fernando Gont on behalf of the UK Centre for the Protection of
National Infrastructure (CPNI). The author would like to thank the National Infrastructure (CPNI). The author would like to thank the
UK CPNI, for their continued support. UK CPNI, for their continued support.
skipping to change at page 13, line 19 skipping to change at page 14, line 19
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005. RFC 4303, December 2005.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007. September 2007.
[RFC5722] Krishnan, S., "Handling of Overlapping IPv6 Fragments",
RFC 5722, December 2009.
[RFC6564] Krishnan, S., Woodyatt, J., Kline, E., Hoagland, J., and
M. Bhatia, "A Uniform Format for IPv6 Extension Headers",
RFC 6564, April 2012.
7.2. Informative References 7.2. Informative References
[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement [RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
Problem Statement", RFC 6104, February 2011. Problem Statement", RFC 6104, February 2011.
[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J. [RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105, Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
February 2011. February 2011.
[I-D.gont-6man-oversized-header-chain] [I-D.gont-6man-oversized-header-chain]
Gont, F. and V. Manral, "Security and Interoperability Gont, F. and V. Manral, "Security and Interoperability
Implications of Oversized IPv6 Header Chains", Implications of Oversized IPv6 Header Chains",
draft-gont-6man-oversized-header-chain-00 (work in draft-gont-6man-oversized-header-chain-01 (work in
progress), February 2012. progress), April 2012.
[I-D.gont-6man-nd-extension-headers] [I-D.gont-6man-nd-extension-headers]
Gont, F., "Security Implications of the Use of IPv6 Gont, F., "Security Implications of the Use of IPv6
Extension Headers with IPv6 Neighbor Discovery", Extension Headers with IPv6 Neighbor Discovery",
draft-gont-6man-nd-extension-headers-02 (work in draft-gont-6man-nd-extension-headers-02 (work in
progress), January 2012. progress), January 2012.
[CPNI-IPv6] [CPNI-IPv6]
Gont, F., "Security Assessment of the Internet Protocol Gont, F., "Security Assessment of the Internet Protocol
version 6 (IPv6)", UK Centre for the Protection of version 6 (IPv6)", UK Centre for the Protection of
National Infrastructure, (available on request). National Infrastructure, (available on request).
[NDPMon] "NDPMon - IPv6 Neighbor Discovery Protocol Monitor", [NDPMon] "NDPMon - IPv6 Neighbor Discovery Protocol Monitor",
<http://ndpmon.sourceforge.net/>. <http://ndpmon.sourceforge.net/>.
[rafixd] "rafixd", <http://www.kame.net/dev/cvsweb2.cgi/kame/kame/ [rafixd] "rafixd", <http://www.kame.net/dev/cvsweb2.cgi/kame/kame/
kame/rafixd/>. kame/rafixd/>.
[ramond] "ramond", <http://ramond.sourceforge.net/>. [ramond] "ramond", <http://ramond.sourceforge.net/>.
[THC-IPV6] [SI6-FRAG]
"THC-IPV6", <http://www.thc.org/thc-ipv6/>. SI6 Networks, "IPv6 NIDS evasion and improvements in IPv6
fragmentation/reassembly", 2012, <http://
Appendix A. Changes from previous versions of the draft (to be removed blog.si6networks.com/2012/02/
by the RFC Editor before publication of this document as a ipv6-nids-evasion-and-improvements-in.html>.
RFC
A.1. Changes from draft-ietf-v6ops-ra-guard-implementation-00
o The filtering rules in Section 3 have been further clarified.
A.2. Changes from draft-gont-v6ops-ra-guard-implementation-01
o Document resubmitted as draft-ietf to reflect wg adoption.
A.3. Changes from draft-gont-v6ops-ra-guard-implementation-00
o Miscellaneous (minor) editorial changes.
o The filtering rules in Section 3 have been polished.
A.4. Changes from draft-gont-v6ops-ra-guard-evasion-01
o The contents were updated to reflect that the evasion
vulnerabilities are based on implementation flaws, rather than on
the RA-Guard "concept" itself.
o The I-D now focuses on providing advice to RA-Guard implementers. [THC-IPV6]
"The Hacker's Choice IPv6 Attack Toolkit",
<http://www.thc.org/thc-ipv6/>.
Appendix B. Assessment tools Appendix A. Assessment tools
CPNI has produced assessment tools (which have not yet been made CPNI has produced assessment tools (which have not yet been made
publicly available) to assess RA-Guard implementations with respect publicly available) to assess RA-Guard implementations with respect
to the issues described in this document. If you think that you to the issues described in this document. If you think that you
would benefit from these tools, we might be able to provide a copy of would benefit from these tools, we might be able to provide a copy of
the tools (please contact Fernando Gont at fernando@gont.com.ar). the tools (please contact Fernando Gont at fernando@gont.com.ar).
[THC-IPV6] is a publicly-available set of tools that implements some [THC-IPV6] is a publicly-available set of tools that implements some
of the techniques described in this document. of the techniques described in this document.
Appendix C. Advice and guidance to vendors Appendix B. Advice and guidance to vendors
Vendors are urged to contact CSIRTUK (csirt@cpni.gsi.gov.uk) if they Vendors are urged to contact CSIRTUK (csirt@cpni.gsi.gov.uk) if they
think they may be affected by the issues described in this document. think they may be affected by the issues described in this document.
As the lead coordination centre for these issues, CPNI is well placed As the lead coordination centre for these issues, CPNI is well placed
to give advice and guidance as required. to give advice and guidance as required.
CPNI works extensively with government departments and agencies, CPNI works extensively with government departments and agencies,
commercial organisations and the academic community to research commercial organisations and the academic community to research
vulnerabilities and potential threats to IT systems especially where vulnerabilities and potential threats to IT systems especially where
they may have an impact on Critical National Infrastructure's (CNI). they may have an impact on Critical National Infrastructure's (CNI).
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