draft-ietf-6man-oversized-header-chain-08.txt   draft-ietf-6man-oversized-header-chain-09.txt 
IPv6 maintenance Working Group (6man) F. Gont IPv6 maintenance Working Group (6man) F. Gont
Internet-Draft SI6 Networks / UTN-FRH Internet-Draft SI6 Networks / UTN-FRH
Updates: 2460 (if approved) V. Manral Updates: 2460 (if approved) V. Manral
Intended status: Standards Track Hewlett-Packard Corp. Intended status: Standards Track Hewlett-Packard Corp.
Expires: April 5, 2014 R. Bonica Expires: May 30, 2014 R. Bonica
Juniper Networks Juniper Networks
October 2, 2013 November 26, 2013
Implications of Oversized IPv6 Header Chains Implications of Oversized IPv6 Header Chains
draft-ietf-6man-oversized-header-chain-08 draft-ietf-6man-oversized-header-chain-09
Abstract Abstract
The IPv6 specification allows IPv6 header chains of an arbitrary The IPv6 specification allows IPv6 header chains of an arbitrary
size. The specification also allows options which can in turn extend size. The specification also allows options which can in turn extend
each of the headers. In those scenarios in which the IPv6 header each of the headers. In those scenarios in which the IPv6 header
chain or options are unusually long and packets are fragmented, or chain or options are unusually long and packets are fragmented, or
scenarios in which the fragment size is very small, the first scenarios in which the fragment size is very small, the first
fragment of a packet may fail to include the entire IPv6 header fragment of a packet may fail to include the entire IPv6 header
chain. This document discusses the interoperability and security chain. This document discusses the interoperability and security
problems of such traffic, and updates RFC 2460 such that the first problems of such traffic, and updates RFC 2460 such that the first
fragment of a packet is required to contain the entire IPv6 header fragment of a packet is required to contain the entire IPv6 header
chain. chain.
Status of this Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 April 5, 2014. This Internet-Draft will expire on May 30, 2014.
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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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Updates to RFC 2460 . . . . . . . . . . . . . . . . . . . . . 8 5. Updates to RFC 2460 . . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . . 12 9.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
With IPv6, optional internet-layer information is carried in one or With IPv6, optional internet-layer information is carried in one or
more IPv6 Extension Headers [RFC2460]. Extension headers are placed more IPv6 Extension Headers [RFC2460]. Extension headers are placed
between the IPv6 header and the upper-layer header in a packet. The between the IPv6 header and the upper-layer header in a packet. The
term "header chain" refers collectively to the IPv6 header, extension term "header chain" refers collectively to the IPv6 header, extension
headers and upper-layer header occurring in a packet. In those headers and upper-layer header occurring in a packet. In those
scenarios in which the IPv6 header chain is unusually long and scenarios in which the IPv6 header chain is unusually long and
packets are fragmented, or scenarios in which the fragment size is packets are fragmented, or scenarios in which the fragment size is
skipping to change at page 3, line 27 skipping to change at page 3, line 7
present in a single IPv4 packet, IPv6 does not have any equivalent present in a single IPv4 packet, IPv6 does not have any equivalent
maximum limit at present. This document updates the set of IPv6 maximum limit at present. This document updates the set of IPv6
specifications to create an overall limit on the size of the specifications to create an overall limit on the size of the
combination of IPv6 options and IPv6 Extension Headers that is combination of IPv6 options and IPv6 Extension Headers that is
allowed in a single IPv6 packet. Namely, it updates RFC 2460 such allowed in a single IPv6 packet. Namely, it updates RFC 2460 such
that the first fragment of a fragmented datagram is required to that the first fragment of a fragmented datagram is required to
contain the entire IPv6 header chain. contain the entire IPv6 header chain.
It should be noted that this requirement does not preclude the use of It should be noted that this requirement does not preclude the use of
large payloads but instead merely requires that all headers, starting large payloads but instead merely requires that all headers, starting
from IPv6 base header and continuing up to the upper layer header from the IPv6 base header and continuing up to the upper layer header
(e.g. TCP or the like) be present in the first fragment. (e.g., TCP or the like) be present in the first fragment.
2. Requirements Language 2. Requirements Language
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].
3. Terminology 3. Terminology
For the purposes of this document, the terms Extension Header, Header For the purposes of this document, the terms Extension Header, Header
skipping to change at page 8, line 7 skipping to change at page 4, line 46
However, when the firewall is presented with a fragmented packet and However, when the firewall is presented with a fragmented packet and
the header chain spans multiple fragments, the first fragment does the header chain spans multiple fragments, the first fragment does
not contain enough information for the firewall to enforce its not contain enough information for the firewall to enforce its
forwarding policy. Lacking sufficient information, the stateless forwarding policy. Lacking sufficient information, the stateless
firewall either forwards or discards that fragment. Regardless of firewall either forwards or discards that fragment. Regardless of
the action that it takes, it may fail to enforce its forwarding the action that it takes, it may fail to enforce its forwarding
policy. policy.
5. Updates to RFC 2460 5. Updates to RFC 2460
When a host fragments a IPv6 datagram, it MUST include the entire When a host fragments an IPv6 datagram, it MUST include the entire
header chain in the first fragment. header chain in the first fragment.
A host that receives a first-fragment that does not satisfy the A host that receives a first-fragment that does not satisfy the
above- stated requirement SHOULD discard the packet (e.g., including above- stated requirement SHOULD discard the packet and SHOULD send
a configuration option that allows such fragments to be accepted for an ICMPv6 error message to the source address of the offending packet
backwards compatibility) and SHOULD send an ICMPv6 error message to (subject to the rules for ICMPv6 errors specified in [RFC4443]).
the source address of the offending packet (subject to the rules for
ICMPv6 errors specified in [RFC4443]).
Likewise, an intermediate system (e.g. router, firewall) that However, for backwards compatibility, implementations MAY include a
configuration option that allows such fragments to be accepted.
Likewise, an intermediate system (e.g., router or firewall) that
receives an IPv6 first-fragment that does not satisfy the above- receives an IPv6 first-fragment that does not satisfy the above-
stated requirements MAY discard that packet, and MAY send an ICMPv6 stated requirement MAY discard that packet, and MAY send an ICMPv6
error message to the source address of the offending packet (subject error message to the source address of the offending packet (subject
to the rules for ICMPv6 error messages specified in [RFC4443]). to the rules for ICMPv6 error messages specified in [RFC4443]).
Intermediate systems having this capability SHOULD support Intermediate systems having this capability SHOULD support
configuration (e.g. enable/disable) of whether such packets are configuration (e.g., enable/disable) of whether such packets are
dropped or not by the intermediate system. dropped or not by the intermediate system.
If a host or intermediate system discards a first-fragment because it If a host or intermediate system discards a first-fragment because it
does not satisfy the above-stated requirements, and sends an ICMPv6 does not satisfy the above-stated requirement, and sends an ICMPv6
error message due to the discard, then the ICMPv6 error message MUST error message due to the discard, then the ICMPv6 error message MUST
be Type 4 ("Parameter Problem") and MUST use Code TBD ("First- be Type 4 ("Parameter Problem") and MUST use Code TBD ("First-
fragment has incomplete IPv6 Header Chain"). The Pointer field fragment has incomplete IPv6 Header Chain"). The Pointer field
contained by the ICMPv6 Parameter Problem message MUST be set to contained by the ICMPv6 Parameter Problem message MUST be set to
zero. Whether a host or intermediate system originates this ICMP zero. The format for the ICMPv6 error message is the same regardless
message, its format is identical. of whether a host or intermediate system originates it.
As a result of the above mentioned requirements, a packet's header As a result of the above mentioned requirement, a packet's header
chain length cannot exceed the Path MTU associated with its chain length cannot exceed the Path MTU associated with its
destination. Hosts MAY discover the Path MTU, using procedures such destination. Hosts discover the Path MTU using procedures such as
as those defined in [RFC1981] and [RFC4821]. However, if a host does those defined in [RFC1981] and [RFC4821]. Hosts that do not discover
not discover the Path MTU, it MUST limit the header chain length to the Path MTU MUST limit the header chain length to 1280 bytes.
1280 bytes. Limiting the header chain length to 1280 bytes ensures Limiting the header chain length to 1280 bytes ensures that the
that the header chain length does not exceed the IPv6 minimum MTU header chain length does not exceed the IPv6 minimum MTU [RFC2460].
[RFC2460].
6. IANA Considerations 6. IANA Considerations
IANA is requested to add a the following entry to the "Reason Code" IANA is requested to add a the following entry to the "Reason Code"
registry for ICMPv6 "Type 4 - Parameter Problem" messages: registry for ICMPv6 "Type 4 - Parameter Problem" messages:
CODE NAME/DESCRIPTION CODE NAME/DESCRIPTION
TBD IPv6 first-fragment has incomplete IPv6 header chain TBD IPv6 first-fragment has incomplete IPv6 header chain
7. Security Considerations 7. Security Considerations
This document describes how improperly-fragmented packets can prevent No new security exposures or issues are raised by this document.
traditional stateless packet filtering. This document describes how undesirably-fragmented packets can be
leveraged to evade stateless packet filtering. Having made that
This document updates RFC 2460 such that those packets are forbidden, observation, this document updates RFC 2460 [RFC2460] so that so
thus enabling stateless packet filtering for IPv6. undesirably-fragmented packets are forbidden. Therefore, a security
vulnerability is removed.
This specification allows nodes that drop the aforementioned packets This specification allows nodes that drop the aforementioned packets
to signal such packet drops with ICMPv6 "Parameter Problem, IPv6 to signal such packet drops with ICMPv6 "Parameter Problem, IPv6
first-fragment has incomplete IPv6 header chain" (Type 4, Code TBD) first-fragment has incomplete IPv6 header chain" (Type 4, Code TBD)
error messages. error messages.
As with all ICMPv6 error/diagnostic messages, deploying Source As with all ICMPv6 error/diagnostic messages, deploying Source
Address Forgery Prevention filters helps reduce the chances of an Address Forgery Prevention filters helps reduce the chances of an
attacker successfully performing a reflection attack by sending attacker successfully performing a reflection attack by sending
forged illegal packets with the victim/target's IPv6 address as the forged illegal packets with the victim/target's IPv6 address as the
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correctly process fragmented packets, even if the IPv6 header chain correctly process fragmented packets, even if the IPv6 header chain
is not fragmented. is not fragmented.
8. Acknowledgements 8. Acknowledgements
The authors of this document would like to thank Ran Atkinson for The authors of this document would like to thank Ran Atkinson for
contributing text and ideas that were incorporated into this contributing text and ideas that were incorporated into this
document. document.
The authors would like to thank (in alphabetical order) Ran Atkinson, The authors would like to thank (in alphabetical order) Ran Atkinson,
Fred Baker, Brian Carpenter, Dominik Elsbroek, Wes George, Mike Fred Baker, Stewart Bryant, Brian Carpenter, Benoit Claise, Dominik
Heard, Bill Jouris, Suresh Krishnan, Dave Thaler, Ole Troan, and Eric Elsbroek, Wes George, Mike Heard, Bill Jouris, Suresh Krishnan, Dave
Vyncke, for providing valuable comments on earlier versions of this Thaler, Ole Troan, Eric Vyncke, and Peter Yee, for providing valuable
document. comments on earlier versions of this document.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery [RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, August 1996. for IP version 6", RFC 1981, August 1996.
[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.
skipping to change at page 12, line 27 skipping to change at page 7, line 5
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006. Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU [RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, March 2007. Discovery", RFC 4821, March 2007.
[I-D.ietf-6man-ext-transmit] [I-D.ietf-6man-ext-transmit]
Carpenter, B. and S. Jiang, "Transmission and Processing Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", of IPv6 Extension Headers", draft-ietf-6man-ext-
draft-ietf-6man-ext-transmit-04 (work in progress), transmit-05 (work in progress), October 2013.
September 2013.
9.2. Informative References 9.2. Informative References
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000. Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed [RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, March 2004. Networks", BCP 84, RFC 3704, March 2004.
[IANA-PROTO] [IANA-PROTO]
Internet Assigned Numbers Authority, "Protocol Numbers", Internet Assigned Numbers Authority, "Protocol Numbers",
February 2013, <http://www.iana.org/assignments/ February 2013, <http://www.iana.org/assignments/protocol-
protocol-numbers/protocol-numbers.txt>. numbers/protocol-numbers.txt>.
Authors' Addresses Authors' Addresses
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
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URI: http://www.si6networks.com URI: http://www.si6networks.com
Vishwas Manral Vishwas Manral
Hewlett-Packard Corp. Hewlett-Packard Corp.
191111 Pruneridge Ave. 191111 Pruneridge Ave.
Cupertino, CA 95014 Cupertino, CA 95014
US US
Phone: 408-447-1497 Phone: 408-447-1497
Email: vishwas.manral@hp.com Email: vishwas.manral@hp.com
URI:
Ronald P. Bonica Ronald P. Bonica
Juniper Networks Juniper Networks
2251 Corporate Park Drive 2251 Corporate Park Drive
Herndon, VA 20171 Herndon, VA 20171
US US
Phone: 571 250 5819 Phone: 571 250 5819
Email: rbonica@juniper.net Email: rbonica@juniper.net
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