Internet DRAFT - draft-smith-6man-more-secure-rh
draft-smith-6man-more-secure-rh
Internet Engineering Task Force M.R. Smith
Internet-Draft 23 February 2022
Updates: 5095, 8200 (if approved)
Intended status: Standards Track
Expires: 27 August 2022
More Secure IPv6 Routing Header Processing
draft-smith-6man-more-secure-rh-03
Abstract
The original IPv6 Type 0 Routing Header has been deprecated due to
the security risk of a packet forwarding loop being formed, by
specifying a large sequence of alternating IPv6 node addresses to
visit. This memo proposes a method to prevent these forwarding loops
forming, allowing the IPv6 Type 0 Routing Header to be more securely
and more safely used. The method may also be applicable to other
unicast source routing scenarios.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 27 August 2022.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. The Fundamental Problem . . . . . . . . . . . . . . . . . . . 3
3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. ICMPv6 Destination Unreachable, Routing Header RPF Check
Failed . . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Updates to RFC8200 . . . . . . . . . . . . . . . . . . . . . 4
7. More General Applicability . . . . . . . . . . . . . . . . . 4
8. Inspiration . . . . . . . . . . . . . . . . . . . . . . . . . 4
9. Security Considerations . . . . . . . . . . . . . . . . . . . 5
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
12. Change Log [RFC Editor please remove] . . . . . . . . . . . . 5
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
13.1. Normative References . . . . . . . . . . . . . . . . . . 5
13.2. Informative References . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
[RFC5095] deprecated the IPv6 Type 0 Routing Header as it could be
used to create a traffic loop, by specifying a large sequence of
alternating IPv6 node addresses to visit. This traffic loop could
consume large amounts of network capacity, causing congestion, and
possibly a network capacity denial of service attack. (The packets
caught in the forwarding loop would eventually be dropped as their
hop-count field will eventually reach zero.)
This memo specifies a method of preventing these traffic loops
occurring, which allows the IPv6 Type 0 to be more securely and more
safely used. This method may also be applicable to other unicast
source routing scenarios.
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2. The Fundamental Problem
The fundamental problem with the type 0 RH, and other source Routing
Headers that support multiple routing hops in general, is that
packets can be made to travel back towards where they've come from.
This then facilitates the first step of a packet being able to enter
a forwarding loop.
3. Solution
Packets need to be prevented from travelling back towards where
they've come from, which then prevents a forwarding loop from being
formed.
The problem of packets going back towards where they've come from
exists in multicast, and has been solved by performing a Reverse Path
Forwarding (RPF) check on a packet as part of the multicast
forwarding procedure.
This RPF check ensures that a packet does not leave via the router in
direction back towards the packet's source address. This direction
back towards the packet's source may be via the packet's ingress
interface, or a different egress interface back towards the packet's
source in an asymmetric routing scenario.
This memo specifies that a Reverse Path Forwarding Check is peformed
when processing the IPv6 Type 0 Routing Header to prevent the packet
going back towards its source.
[RFC3704], although describing RPF checks to prevent source IP
address spoofing, provides good descriptions of the RPF checking
process.
4. Method
The following method is used to process IPv6 Type 0 Routing Headers
while also preventing their packets from entering a forwarding loop.
1. Perform the Type 0 Routing Header processing algorithm as
specified in [RFC2460], section 4.4. This will result in the
packet's Type 0 Routing Header and Destination Address being
updated to the next address specified in the routing header to
visit.
2. Perform an RPF check against the updated packet.
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3. If the packet is to now travel back towards its source, discard
the packet, and generate an ICMPv6 Destination Unreachable,
Routing Header RPF Check Failed error (specified below), sending
it to the packet's source (address).
4. Otherwise, forward the packet to its new Destination Address.
Note that an implementation could perform the RPF check against the
next address specified in the Type 0 Routing Header before updating
the packet's Type 0 Routing Header and Destination Address field as a
processing optimisation. If the RPF check fails in this case, the
packet's Type 0 Routing Header and Destination Address will need to
be updated so that it can then be correctly used as the message body
for the ICMPv6 Destination Unreachable error message [RFC4443].
5. ICMPv6 Destination Unreachable, Routing Header RPF Check Failed
A new ICMPv6 Destination Unreachable error message is defined for a
"Routing Header RPF Check Failed", Type 1, Code [IANA-TBD].
Processing of this error message is as per the general Destination
Unreachable message processing specified in [RFC4443]. There is no
special handling of this error message at the receiver.
6. Updates to RFC8200
This memo makes the reason for the IPv6 Type 0 Routing Header
deprecation invalid. Consequently, [RFC8200] is updated to now
specify the Type 0 Routing Header formerly specified in [RFC2460].
7. More General Applicability
The method of preventing a packet or a frame from travelling back
towards its origin when being forwarded can be applied to any unicast
source routing scenario where a forwarding loop is possible.
Examples of where it could be applied are the IPv6 Segment Routing
Header [RFC8754], Segment Routing over MPLS [RFC8660], the IPv6
Compressed Rouing Header [CRH] and IPv4 [RFC0791].
8. Inspiration
The idea of using an RPF check to prevent forwarding loops when
performing unicast source routing was inspired by using an RPF check
to prevent forwarding loops in hop-by-hop forwarding through the
network using an anycast IPv6 address [FFANYCAST]. In this scenario,
a packet is forwarded towards the next closest instance of the
anycast address in the network, excluding anycast address instances
that are back towards the packet's source.
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9. Security Considerations
This memo addresses the primary security issue that caused the Type 0
Routing Header to be deprecated.
This memo does not address other security issues related to routing
headers and source routing, such as using a routing header to bypass
a security policy enforcement device, or untrusted packets with
routing headers entering a routing header trusting domain. Other
mitigations to these security issues, such as source address
filtering at ingress to the local network, or packet authentication
[RFC4302], need to be deployed.
10. IANA Considerations
IANA are requested to allocate a suitable Type 1 Destination
Unreachable error code for "Routing Header RPF Check Failed".
11. Acknowledgements
Review and comments were provided by YOUR NAME HERE!
This memo was prepared using the xml2rfc tool.
12. Change Log [RFC Editor please remove]
draft-smith-6man-more-secure-rh-00, initial version, 2022-02-14
draft-smith-6man-more-secure-rh-01, 2022-02-17
* IEEE 802.2 Source Route Bridging does a check for a forwarding
loop when forwarding.
* Better wording and minor corrections.
draft-smith-6man-more-secure-rh-02, 2022-02-24
* Hop-by-hop anycast inspiration
draft-smith-6man-more-secure-rh-03, 2022-02-24
* Extra greater than sign
13. References
13.1. Normative References
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[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
13.2. Informative References
[CRH] "The IPv6 Compact Routing Header (CRH)",
<https://datatracker.ietf.org/doc/draft-bonica-6man-comp-
rtg-hdr/>.
[FFANYCAST]
"IPv6 Formal Anycast Addresses and Functional Anycast
Addresses", <https://datatracker.ietf.org/doc/draft-smith-
6man-form-func-anycast-addresses/>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, DOI 10.17487/RFC3704, March
2004, <https://www.rfc-editor.org/info/rfc3704>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/info/rfc4302>.
[RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
of Type 0 Routing Headers in IPv6", RFC 5095,
DOI 10.17487/RFC5095, December 2007,
<https://www.rfc-editor.org/info/rfc5095>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
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[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
Author's Address
Mark Smith
PO BOX 521
HEIDELBERG VIC 3084
Australia
Email: markzzzsmith@gmail.com
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