draft-ietf-6man-nd-extension-headers-05.txt   rfc6980.txt 
IPv6 maintenance Working Group (6man) F. Gont Internet Engineering Task Force (IETF) F. Gont
Internet-Draft SI6 Networks / UTN-FRH Request for Comments: 6980 SI6 Networks / UTN-FRH
Updates: 3971, 4861 (if approved) June 3, 2013 Updates: 3971, 4861 August 2013
Intended status: Standards Track Category: Standards Track
Expires: December 5, 2013 ISSN: 2070-1721
Security Implications of IPv6 Fragmentation with IPv6 Neighbor Discovery Security Implications of IPv6 Fragmentation with IPv6 Neighbor Discovery
draft-ietf-6man-nd-extension-headers-05
Abstract Abstract
This document analyzes the security implications of employing IPv6 This document analyzes the security implications of employing IPv6
fragmentation with Neighbor Discovery (ND) messages. It updates RFC fragmentation with Neighbor Discovery (ND) messages. It updates RFC
4861 such that use of the IPv6 Fragmentation Header is forbidden in 4861 such that use of the IPv6 Fragmentation Header is forbidden in
all Neighbor Discovery messages, thus allowing for simple and all Neighbor Discovery messages, thus allowing for simple and
effective counter-measures for Neighbor Discovery attacks. Finally, effective countermeasures for Neighbor Discovery attacks. Finally,
it discusses the security implications of using IPv6 fragmentation it discusses the security implications of using IPv6 fragmentation
with SEcure Neighbor Discovery (SEND), and formally updates RFC 3971 with SEcure Neighbor Discovery (SEND) and formally updates RFC 3971
to provide advice regarding how the aforementioned security to provide advice regarding how the aforementioned security
implications can be prevented. implications can be mitigated.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This is an Internet Standards Track document.
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on December 5, 2013. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6980.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................2
2. Traditional Neighbor Discovery and IPv6 Fragmentation . . . . 5 2. Traditional Neighbor Discovery and IPv6 Fragmentation ...........4
3. SEcure Neighbor Discovery (SEND) and IPv6 Fragmentation . . . 6 3. SEcure Neighbor Discovery (SEND) and IPv6 Fragmentation .........5
4. Rationale for Forbidding IPv6 Fragmentation in Neighbor 4. Rationale for Forbidding IPv6 Fragmentation in Neighbor
Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Discovery .......................................................6
5. Specification . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Specification ...................................................6
6. Operational Advice . . . . . . . . . . . . . . . . . . . . . . 9 6. Operational Advice ..............................................7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations .........................................7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8. Acknowledgements ................................................8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 9. References ......................................................8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9.1. Normative References .......................................8
10.1. Normative References . . . . . . . . . . . . . . . . . . 13 9.2. Informative References .....................................9
10.2. Informative References . . . . . . . . . . . . . . . . . 13 Appendix A. Message Size When Carrying Certificates ...............10
Appendix A. Message Size When Carrying Certificates . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
The Neighbor Discovery Protocol (NDP) is specified in RFC 4861 The Neighbor Discovery Protocol (NDP) is specified in RFC 4861
[RFC4861]. It is used by both hosts and routers. Its functions [RFC4861]. It is used by both hosts and routers. Its functions
include Neighbor Discovery (ND), Router Discovery (RD), Address include Neighbor Discovery (ND), Router Discovery (RD), address
Autoconfiguration, Address Resolution, Neighbor Unreachability autoconfiguration, address resolution, Neighbor Unreachability
Detection (NUD), Duplicate Address Detection (DAD), and Redirection. Detection (NUD), Duplicate Address Detection (DAD), and redirection.
Many of the possible attacks against the Neighbor Discovery Protocol Many of the possible attacks against the Neighbor Discovery Protocol
are discussed in detail in [RFC3756]. In order to mitigate the are discussed in detail in [RFC3756]. In order to mitigate the
aforementioned possible attacks, the SEcure Neighbor Discovery (SEND) aforementioned possible attacks, SEcure Neighbor Discovery (SEND) was
was standardized. SEND employs a number of mechanisms to certify the standardized. SEND employs a number of mechanisms to certify the
origin of Neighbor Discovery packets and the authority of routers, origin of Neighbor Discovery packets and the authority of routers,
and to protect Neighbor Discovery packets from being the subject of and to protect Neighbor Discovery packets from being the subject of
modification or replay attacks. modification or replay attacks.
However, a number of factors, such as the high administrative However, a number of factors, such as the high administrative
overhead of deploying trust anchors and the unavailability of SEND overhead of deploying trust anchors and the unavailability of SEND
implementations for many widely-deployed operating systems, make SEND implementations for many widely deployed operating systems, make SEND
hard to deploy [Gont-DEEPSEC2011]. Thus, in many general scenarios hard to deploy [Gont-DPSC]. Thus, in many general scenarios, it may
it may be necessary and/or convenient to use other mitigation be necessary and/or convenient to use other mitigation techniques for
techniques for NDP-based attacks. The following mitigations are NDP-based attacks. The following mitigations are currently available
currently available for NDP attacks: for NDP attacks:
o Static Access Control Lists (ACLs) in switches o Static Access Control Lists (ACLs) in switches
o Layer-2 filtering of Neighbor Discovery packets (such as RA-Guard o Layer-2 filtering of Neighbor Discovery packets (such as RA-Guard
[RFC6105]) [RFC6105])
o Neighbor Discovery monitoring tools (e.g., such as NDPMon o Neighbor Discovery monitoring tools (e.g., NDPMon [NDPMon] and
[NDPMon], ramond [ramond]) ramond [ramond])
o Intrusion Prevention Systems (IPS) o Intrusion Prevention Systems (IPS)
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. It for attack vectors based on ICMPv6 Router Advertisement (RA)
is meant to block attack packets at a layer-2 device before the messages. It is meant to block attack packets at a layer-2 device
attack packets actually reach the target nodes. [RFC6104] describes before the attack packets actually reach the target nodes. [RFC6104]
the problem statement of "Rogue IPv6 Router Advertisements", and describes the problem statement of "Rogue IPv6 Router
[RFC6105] specifies the "IPv6 Router Advertisement Guard" Advertisements", and [RFC6105] specifies the "IPv6 Router
functionality. Advertisement Guard" functionality.
Tools such as NDPMon [NDPMon] and ramond [ramond] aim at monitoring Tools such as NDPMon [NDPMon] and ramond [ramond] aim to monitor
Neighbor Discovery traffic in the hopes of detecting possible attacks Neighbor Discovery traffic in the hopes of detecting possible attacks
when there are discrepancies between the information advertised in when there are discrepancies between the information advertised in
Neighbor Discovery packets and the information stored on a local Neighbor Discovery packets and the information stored on a local
database. database.
Some Intrusion Prevention Systems (IPS) can mitigate Neighbor Some Intrusion Prevention Systems (IPS) can mitigate Neighbor
Discovery attacks. We recommend that Intrusion Prevention Systems Discovery attacks. We recommend that Intrusion Prevention Systems
(IPS) implement mitigations for NDP attacks. implement mitigations for NDP attacks.
A key challenge that these mitigation or monitoring techniques face IPv6 fragmentation introduces a key challenge for these mitigation or
is that introduced by IPv6 fragmentation, since it is trivial for an monitoring techniques, since it is trivial for an attacker to conceal
attacker to conceal his attack by fragmenting his packets into his attack by fragmenting his packets into multiple fragments. This
multiple fragments. This may limit or even eliminate the may limit or even eliminate the effectiveness of the aforementioned
effectiveness of the aforementioned mitigation or monitoring mitigation or monitoring techniques. Recent work [CPNI-IPv6]
techniques. Recent work [CPNI-IPv6] indicates that current indicates that current implementations of the aforementioned
implementations of the aforementioned mitigations for NDP attacks can mitigations for NDP attacks can be trivially evaded. For example, as
be trivially evaded. For example, as noted in noted in [RA-GUARD], current RA-Guard implementations can be
[I-D.ietf-v6ops-ra-guard-implementation], current RA-Guard trivially evaded by fragmenting the attack packets into multiple
implementations can be trivially evaded by fragmenting the attack fragments, such that the layer-2 device cannot find all the necessary
packets into multiple fragments, such that the layer-2 device cannot information to perform packet filtering in the same packet. While
find all the necessary information to perform packet filtering in the Neighbor Discovery monitoring tools could (in theory) implement IPv6
same packet. While Neighbor Discovery monitoring tools could (in fragment reassembly, this is usually an arms-race with the attacker
theory implement IPv6 fragment reassembly, this is usually an arms- (an attacker can generate lots of forged fragments to "confuse" the
race with the attacker (an attacker generate lots of forged fragments monitoring tools), and therefore the aforementioned tools are
to "confuse" the monitoring tools), and therefore the aforementioned unreliable for the detection of such attacks.
tools are unreliable for the detection of such attacks.
Section 2 analyzes the use of IPv6 fragmentation in traditional Section 2 analyzes the use of IPv6 fragmentation in traditional
Neighbor discovery. Section 3 analyzes the use of IPv6 fragmentation Neighbor Discovery. Section 3 analyzes the use of IPv6 fragmentation
in SEcure Neighbor Discovery (SEND). Section 4 provides the in SEcure Neighbor Discovery (SEND). Section 4 provides the
rationale for forbidding the use of IPv6 fragmentation with Neighbor rationale for forbidding the use of IPv6 fragmentation with Neighbor
Discovery. Section 5 formally updates RFC 4861 such that use of the Discovery. Section 5 formally updates RFC 4861 such that the use of
IPv6 Fragment Header with traditional Neighbor Discovery is the IPv6 Fragment Header with traditional Neighbor Discovery is
forbidden, and also formally updates RFC 3971 providing advice on the forbidden, and also formally updates RFC 3971 by providing advice on
use of IPv6 fragmentation with SEND. Section 6 provides operational the use of IPv6 fragmentation with SEND. Section 6 provides
advice about interoperability problems arising from the use of IPv6 operational advice about interoperability problems arising from the
fragmentation with Neighbor Discovery. use of IPv6 fragmentation with Neighbor Discovery.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Traditional Neighbor Discovery and IPv6 Fragmentation 2. Traditional Neighbor Discovery and IPv6 Fragmentation
The only potential use case for IPv6 fragmentation with traditional The only potential use case for IPv6 fragmentation with traditional
(i.e., non-SEND) IPv6 Neighbor Discovery would be that in which a (i.e., non-SEND) IPv6 Neighbor Discovery would be that in which a
Router Advertisement must include a large number of options (Prefix Router Advertisement must include a large number of options (Prefix
skipping to change at page 5, line 24 skipping to change at page 4, line 43
Some Neighbor Discovery implementations are known to silently Some Neighbor Discovery implementations are known to silently
ignore Router Advertisement messages that employ fragmentation. ignore Router Advertisement messages that employ fragmentation.
Therefore, splitting the necessary information into multiple RA Therefore, splitting the necessary information into multiple RA
messages (rather than sending a large RA message that is messages (rather than sending a large RA message that is
fragmented into multiple IPv6 fragments) is probably desirable fragmented into multiple IPv6 fragments) is probably desirable
even from an interoperability point of view. even from an interoperability point of view.
Thus, avoiding the use of IPv6 fragmentation in traditional Neighbor Thus, avoiding the use of IPv6 fragmentation in traditional Neighbor
Discovery would greatly simplify and improve the effectiveness of Discovery would greatly simplify and improve the effectiveness of
monitoring and filtering Neighbor Discovery traffic, and would also monitoring and filtering Neighbor Discovery traffic and would also
prevent interoperability problems with those implementations that do prevent interoperability problems with those implementations that do
not support fragmentation in Neighbor Discovery messages. not support fragmentation in Neighbor Discovery messages.
3. SEcure Neighbor Discovery (SEND) and IPv6 Fragmentation 3. SEcure Neighbor Discovery (SEND) and IPv6 Fragmentation
SEND packets typically carry more information than traditional SEND packets typically carry more information than traditional
Neighbor Discovery packets: for example, they include additional Neighbor Discovery packets: for example, they include additional
options such as the CGA option and the RSA signature option. options such as the Cryptographically Generated Address (CGA) option
and the RSA signature option.
When SEND nodes employ any of the Neighbor Discovery messages When SEND nodes employ any of the Neighbor Discovery messages
specified in [RFC4861], the situation is roughly the same: if more specified in [RFC4861], the situation is roughly the same: if more
information than would fit in a non-fragmented Neighbor Discovery information than would fit in a non-fragmented Neighbor Discovery
packet needs to be sent, it should be split into multiple Neighbor packet needs to be sent, it should be split into multiple Neighbor
Discovery messages (such that IPv6 fragmentation is avoided). Discovery messages (such that IPv6 fragmentation is avoided).
However, Certification Path Advertisement messages (specified in However, Certification Path Advertisement (CPA) messages (specified
[RFC3971]) pose a different situation, since the Certificate Option in [RFC3971]) pose a different situation, since the Certificate
they include typically contains much more information than any other Option they include typically contains much more information than any
Neighbor Discovery option. For example, Appendix C of [RFC3971] other Neighbor Discovery option. For example, Appendix C of
reports Certification Path Advertisement messages from 1050 to 1066 [RFC3971] reports Certification Path Advertisement messages from 1050
bytes on an Ethernet link layer. Since the size of CPA messages to 1066 bytes on an Ethernet link layer. Since the size of CPA
could potentially exceed the MTU of the local link, Section 5 messages could potentially exceed the MTU of the local link,
recommends that fragmented CPA messages be normally processed, but Section 5 recommends that fragmented CPA messages be processed
discourages the use of keys that would result in fragmented CPA normally, but discourages the use of keys that would result in
messages. fragmented CPA messages.
It should be noted that relying on fragmentation opens the door to a It should be noted that relying on fragmentation opens the door to a
variety of IPv6 fragmentation-based attacks against SEND. In variety of IPv6 fragmentation-based attacks against SEND. In
particular, if an attacker is located on the same broadcast domain as particular, if an attacker is located on the same broadcast domain as
the victim host, and Certification Path Advertisement messages employ the victim host and Certification Path Advertisement messages employ
IPv6 fragmentation, it would be trivial for the attacker to forge IPv6 fragmentation, it would be trivial for the attacker to forge
IPv6 fragments such that they result in "Fragment ID collisions", IPv6 fragments such that they result in "Fragment ID collisions",
causing both the attack fragments and the legitimate fragments to be causing both the attack fragments and the legitimate fragments to be
discarded by the victim node. This would eventually cause the discarded by the victim node. This would eventually cause
Authorization Delegation Discovery (Section 6 of [RFC3971]) to fail, Authorization Delegation Discovery (Section 6 of [RFC3971]) to fail,
thus leading the host to fall back (depending on local configuration) thus leading the host to (depending on local configuration) either
either to unsecured mode, or to reject the corresponding Router fall back to unsecured mode or reject the corresponding Router
Advertisement messages (possibly resulting in a Denial of Service). Advertisement messages (possibly resulting in a denial of service).
4. Rationale for Forbidding IPv6 Fragmentation in Neighbor Discovery 4. Rationale for Forbidding IPv6 Fragmentation in Neighbor Discovery
A number of considerations should be made regarding the use of IPv6 A number of considerations should be made regarding the use of IPv6
fragmentation with Neighbor Discovery: fragmentation with Neighbor Discovery:
o A significant number of existing implementations already silently o A significant number of existing implementations already silently
drop fragmented ND messages, so the use of IPv6 fragmentation may drop fragmented ND messages, so the use of IPv6 fragmentation may
hamper interoperability among IPv6 implementations. hamper interoperability among IPv6 implementations.
o Although it is possible to build an ND message that needs to be o Although it is possible to build an ND message that needs to be
fragmented, such packets are unlikely to exist in the real world fragmented, such packets are unlikely to exist in the real world
because of the large number of options that would be required for because of the large number of options that would be required for
the resulting packet to exceed the minimum IPv6 MTU of 1280 the resulting packet to exceed the minimum IPv6 MTU of
octets. 1280 octets.
o If an ND message was so large as to need fragmentation, there is o If an ND message was so large as to need fragmentation, there is
an option to distribute the same information amongst more than one an option to distribute the same information amongst more than one
message, each of which is small enough to not need fragmentation. message, each of which is small enough to not need fragmentation.
Thus, forbidding the use of IPv6 fragmentation with Neighbor Thus, forbidding the use of IPv6 fragmentation with Neighbor
Discovery normalizes existing behavior and sets the expectations of Discovery normalizes existing behavior and sets the expectations of
all implementations to the existing lowest common denominator. all implementations to the existing lowest common denominator.
5. Specification 5. Specification
skipping to change at page 8, line 25 skipping to change at page 6, line 48
o Router Advertisement o Router Advertisement
o Redirect o Redirect
o Certification Path Solicitation o Certification Path Solicitation
Nodes SHOULD NOT employ IPv6 fragmentation for sending the following Nodes SHOULD NOT employ IPv6 fragmentation for sending the following
messages (see Section 6.4.2 of [RFC3971]): messages (see Section 6.4.2 of [RFC3971]):
o Certification Path Advertisement messages o Certification Path Advertisement
Nodes MUST silently ignore the following Neighbor Discovery and Nodes MUST silently ignore the following Neighbor Discovery and
SEcure Neighbor Discovery messages if the packets carrying them SEcure Neighbor Discovery messages if the packets carrying them
include an IPv6 Fragmentation Header: include an IPv6 Fragmentation Header:
o Neighbor Solicitation o Neighbor Solicitation
o Neighbor Advertisement o Neighbor Advertisement
o Router Solicitation o Router Solicitation
skipping to change at page 9, line 9 skipping to change at page 7, line 32
o Certification Path Advertisement o Certification Path Advertisement
SEND nodes SHOULD NOT employ keys that would result in fragmented CPA SEND nodes SHOULD NOT employ keys that would result in fragmented CPA
messages. messages.
6. Operational Advice 6. Operational Advice
An operator detecting that Neighbor Discovery traffic is being An operator detecting that Neighbor Discovery traffic is being
silently dropped should find whether the corresponding Neighbor silently dropped should find whether the corresponding Neighbor
Discovery are employing IPv6 fragmentation. If they are, it is Discovery messages are employing IPv6 fragmentation. If they are, it
likely that the devices receiving such packets are silently dropping is likely that the devices receiving such packets are silently
them merely because they employ IPv6 fragmentation. In such case, an dropping them merely because they employ IPv6 fragmentation. In such
operator should check whether the sending device has an option to a case, an operator should check whether the sending device has an
prevent fragmentation of ND messages, and/or see whether it is option to prevent fragmentation of ND messages, and/or see whether it
possible to reduce the options carried on such messages. We note is possible to reduce the options carried on such messages. We note
that solving this (unlikely) problem might need a software upgrade to that solving this (unlikely) problem might require a software upgrade
a version that does not employ IPv6 fragmentation with Neighbor to a version that does not employ IPv6 fragmentation with Neighbor
Discovery. Discovery.
7. IANA Considerations 7. Security Considerations
There are no IANA registries within this document. The RFC-Editor
can remove this section before publication of this document as an
RFC.
8. Security Considerations
The IPv6 Fragmentation Header can be leveraged to circumvent network The IPv6 Fragmentation Header can be leveraged to circumvent network
monitoring tools and current implementations of mechanisms such as monitoring tools and current implementations of mechanisms such as
RA-Guard [I-D.ietf-v6ops-ra-guard-implementation]. By updating the RA-Guard [RA-GUARD]. By updating the relevant specifications such
relevant specifications such that the IPv6 Fragment Header is not that the IPv6 Fragment Header is not allowed in any Neighbor
allowed in any Neighbor Discovery messages except "Certification Path Discovery messages except Certification Path Advertisement messages,
Advertisement", protection of local nodes against Neighbor Discovery protection of local nodes against Neighbor Discovery attacks, as well
attacks, and monitoring of Neighbor Discovery traffic is greatly as the monitoring of Neighbor Discovery traffic, are greatly
simplified. simplified.
[I-D.ietf-v6ops-ra-guard-implementation] discusses an improvement to As noted in Section 3, the use of SEND could potentially result in
the RA-Guard mechanism that can mitigate Neighbor Discovery attacks fragmented Certification Path Advertisement messages, thus allowing
that employ IPv6 Fragmentation. However, it should be noted that
unless [RFC4861] is updated (as proposed in this document), Neighbor
Discovery monitoring tools (such as NDPMon [NDPMon], and ramond
[ramond]) would remain unreliable and trivial to circumvent by a
skilled attacker.
As noted in Section 3, use of SEND could potentially result in
fragmented "Certification Path Advertisement" messages, thus allowing
an attacker to employ IPv6 fragmentation-based attacks against such an attacker to employ IPv6 fragmentation-based attacks against such
messages. Therefore, to the extent that is possible, such use of messages. Therefore, to the extent that is possible, such use of
fragmentation should be avoided. fragmentation should be avoided.
9. Acknowledgements 8. Acknowledgements
The author would like to thank (in alphabetical order) Mikael The author would like to thank (in alphabetical order) Mikael
Abrahamsson, Ran Atkinson, Ron Bonica, Jean-Michel Combes, David Abrahamsson, Ran Atkinson, Ron Bonica, Jean-Michel Combes, David
Farmer, Adrian Farrel, Stephen Farrell, Roque Gagliano, Brian Farmer, Adrian Farrel, Stephen Farrell, Roque Gagliano, Brian
Haberman, Bob Hinden, Philip Homburg, Ray Hunter, Arturo Servin, Mark Haberman, Bob Hinden, Philip Homburg, Ray Hunter, Arturo Servin, Mark
Smith, and Martin Stiemerling, for providing valuable comments on Smith, and Martin Stiemerling for providing valuable comments on
earlier versions of this document. earlier versions of this document.
The author would like to thank Roque Gagliano, who contributed the The author would also like to thank Roque Gagliano for contributing
information regarding messages sizes in Appendix A. the information regarding message sizes in Appendix A, and Arturo
Servin for presenting this document at IETF 81.
Finally, the author would like to thank his brother, friend, and
colleague, Guillermo Gont, for his love and support.
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).
UK CPNI, for their continued support.
10. References 9. References
10.1. Normative References 9.1. Normative References
[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.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005. Neighbor Discovery (SEND)", RFC 3971, March 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.
[RFC6494] Gagliano, R., Krishnan, S., and A. Kukec, "Certificate [RFC6494] Gagliano, R., Krishnan, S., and A. Kukec, "Certificate
Profile and Certificate Management for SEcure Neighbor Profile and Certificate Management for SEcure Neighbor
Discovery (SEND)", RFC 6494, February 2012. Discovery (SEND)", RFC 6494, February 2012.
10.2. Informative References 9.2. Informative References
[RFC3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor [CPNI-IPv6] Gont, F., "Security Assessment of the Internet Protocol
Discovery (ND) Trust Models and Threats", RFC 3756, version 6 (IPv6)", UK Centre for the Protection of
May 2004. National Infrastructure, (available on request).
[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement [Gont-DPSC] Gont, F., "Results of a Security Assessment of the
Problem Statement", RFC 6104, February 2011. Internet Protocol version 6 (IPv6)", DEEPSEC 2011
Conference, Vienna, Austria, November 2011,
<http://www.si6networks.com/presentations/deepsec2011/
fgont-deepsec2011-ipv6-security.pdf>.
[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J. [NDPMon] SourceForge, "NDPMon - IPv6 Neighbor Discovery Protocol
Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105, Monitor", July 2012, <http://ndpmon.sourceforge.net/>.
February 2011.
[NDPMon] "NDPMon - IPv6 Neighbor Discovery Protocol Monitor", [RA-GUARD] Gont, F., "Implementation Advice for IPv6 Router
<http://ndpmon.sourceforge.net/>. Advertisement Guard (RA-Guard)", Work in Progress,
November 2012.
[ramond] "ramond", <http://ramond.sourceforge.net/>. [ramond] SourceForge, "ramond", January 2009,
<http://ramond.sourceforge.net/>.
[I-D.ietf-v6ops-ra-guard-implementation] [RFC3756] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor
Gont, F., "Implementation Advice for IPv6 Router Discovery (ND) Trust Models and Threats", RFC 3756,
Advertisement Guard (RA-Guard)", May 2004.
draft-ietf-v6ops-ra-guard-implementation-07 (work in
progress), November 2012.
[CPNI-IPv6] [RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
Gont, F., "Security Assessment of the Internet Protocol Problem Statement", RFC 6104, February 2011.
version 6 (IPv6)", UK Centre for the Protection of
National Infrastructure, (available on request).
[Gont-DEEPSEC2011] [RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and
Gont, "Results of a Security Assessment of the Internet J. Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
Protocol version 6 (IPv6)", DEEPSEC 2011 Conference, February 2011.
Vienna, Austria, November 2011, <http://
www.si6networks.com/presentations/deepsec2011/
fgont-deepsec2011-ipv6-security.pdf>.
Appendix A. Message Size When Carrying Certificates Appendix A. Message Size When Carrying Certificates
This section aims at estimating the size of normal Certification Path This section aims at estimating the size of normal Certification Path
Advertisement messages. Advertisement messages.
Considering a Certification Path Advertisement (CPA) such as that of Considering a Certification Path Advertisement (CPA) such as that of
Appendix C of [RFC3971] (certification path length of 4, between 1 Appendix C of [RFC3971] (certification path length of 4, between 1
and 4 address prefix extensions, and a key length of 1024 bits), the and 4 address prefix extensions, and a key length of 1024 bits), the
certificate lengths range between 864 to 888 bytes (and the certificate lengths range between 864 and 888 bytes (and the
corresponding Ethernet packets from 1050 to 1066 bytes) [RFC3971]. corresponding Ethernet packets from 1050 to 1066 bytes) [RFC3971].
Updating the aforementioned packet size to account for the larger Updating the aforementioned packet size to account for the larger
(2048 bits) keys required by [RFC6494] results in packet sizes (2048 bits) keys required by [RFC6494] results in packet sizes
ranging from 1127 to 1238 bytes, which are smaller than the minimum ranging from 1127 to 1238 bytes, which are smaller than the minimum
IPv6 MTU (1280 bytes), and much smaller than the ubiquitous Ethernet IPv6 MTU (1280 bytes) and much smaller than the ubiquitous Ethernet
MTU (1500 bytes). MTU (1500 bytes).
However, we note that packet sizes may vary depending on a number of However, we note that packet sizes may vary depending on a number of
factors, including: factors, including:
o the number of prefixes included in the certificate o the number of prefixes included in the certificate
o the length of Fully-Qualified Domain Names (FQDNs) in Trust Anchor o the length of Fully Qualified Domain Names (FQDNs) in Trust Anchor
(TA) options [RFC3971] (if present) (TA) options [RFC3971] (if present)
If larger key sizes (i.e. 4096 bits) were required in the future, a If larger key sizes (e.g., 4096 bits) are required in the future, a
larger MTU size might be required to to convey such information in larger MTU size might be required to convey such information in
Neighbor Discovery packets without the need to employ fragmentation. Neighbor Discovery packets without the need to employ fragmentation.
Author's Address Author's Address
Fernando Gont Fernando Gont
SI6 Networks / UTN-FRH SI6 Networks / UTN-FRH
Evaristo Carriego 2644 Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706 Haedo, Provincia de Buenos Aires 1706
Argentina Argentina
Phone: +54 11 4650 8472 Phone: +54 11 4650 8472
Email: fgont@si6networks.com EMail: fgont@si6networks.com
URI: http://www.si6networks.com URI: http://www.si6networks.com
 End of changes. 56 change blocks. 
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