draft-ietf-6man-oversized-header-chain-06.txt   draft-ietf-6man-oversized-header-chain-07.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: March 7, 2014 R. Bonica Expires: March 14, 2014 R. Bonica
Juniper Networks Juniper Networks
September 3, 2013 September 10, 2013
Implications of Oversized IPv6 Header Chains Implications of Oversized IPv6 Header Chains
draft-ietf-6man-oversized-header-chain-06 draft-ietf-6man-oversized-header-chain-07
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
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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 March 7, 2014. This Internet-Draft will expire on March 14, 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.
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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While IPv4 had a fixed maximum length for the set of all IPv4 options While IPv4 had a fixed maximum length for the set of all IPv4 options
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
e.g. IPv6 jumbo payloads but instead merely requires that all large payloads but instead merely requires that all headers, starting
*headers*, starting from IPv6 base header and continuing up to the from IPv6 base header and continuing up to the upper layer header
upper layer header (e.g. TCP or the like) be present in the first (e.g. TCP or the like) be present in the first fragment.
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
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First Fragment: First Fragment:
An IPv6 fragment with fragment offset equal to 0. An IPv6 fragment with fragment offset equal to 0.
IPv6 Header Chain: IPv6 Header Chain:
The header chain contains an initial IPv6 header, zero or more The header chain contains an initial IPv6 header, zero or more
IPv6 extension headers, and optionally, a single upper-layer IPv6 extension headers, and optionally, a single upper-layer
header. If an upper-layer header is present, it terminates the header. If an upper-layer header is present, it terminates the
header chain. header chain; otherwise the "No Next Header" value (Next Header =
59) terminates it.
The first member of the header chain is always an IPv6 header. The first member of the header chain is always an IPv6 header.
For a subsequent header to qualify as a member of the header For a subsequent header to qualify as a member of the header
chain, it must be referenced by the "Next Header" field of the chain, it must be referenced by the "Next Header" field of the
previous member of the header chain. However, if a second IPv6 previous member of the header chain. However, if a second IPv6
header appears in the header chain, as is the case when IPv6 is header appears in the header chain, as is the case when IPv6 is
tunneled over IPv6, the second IPv6 header is considered to be an tunneled over IPv6, the second IPv6 header is considered to be an
upper-layer header and terminates the header chain. Likewise, if upper-layer header and terminates the header chain. Likewise, if
an Encapsulating Security Payload (ESP) header appears in the an Encapsulating Security Payload (ESP) header appears in the
header chain it is considered to be an upper-layer header and it header chain it is considered to be an upper-layer header and it
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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 a 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 requirements SHOULD discard that packet, and also MAY above-stated requirement SHOULD discard that packet, and also MAY
send an ICMPv6 error message to the source address of the offending send an ICMPv6 error message to the source address of the offending
packet (subject to the rules for ICMPv6 errors specified in packet (subject to the rules for ICMPv6 errors specified in
[RFC4443]). [RFC4443]).
Likewise, an intermediate system (e.g. router, firewall) that Likewise, an intermediate system (e.g. router, 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 requirements 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
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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 requirements, 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. zero.
As a result of the above mentioned requirements, a packet's header
chain length cannot exceed the Path MTU associated with its
destination. Hosts MAY discover the Path MTU, using procedures such
as those defined in [RFC1981] and [RFC4821]. However, if a host does
not discover the Path MTU, it MUST limit the header chain length to
1280 bytes. Limiting the header chain length to 1280 bytes ensures
that the header chain length does not exceed the IPv6 minimum MTU.
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
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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
IPv6 Source Address of the illegal packet [RFC2827] [RFC3704]. IPv6 Source Address of the illegal packet [RFC2827] [RFC3704].
A firewall that performs stateless deep packet inspection (i.e.,
examines application payload content) might still be unable to
correctly process fragmented packets, even if the IPv6 header chain
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, Mike Heard, Bill Fred Baker, Brian Carpenter, Dominik Elsbroek, Wes George, Mike
Jouris, Suresh Krishnan, Dave Thaler, Ole Troan, and Eric Vyncke, for Heard, Bill Jouris, Suresh Krishnan, Dave Thaler, Ole Troan, and Eric
providing valuable comments on earlier versions of this document. Vyncke, for providing valuable 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
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.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998. (IPv6) Specification", RFC 2460, December 1998.
[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
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-transmit-03 (work in progress), draft-ietf-6man-ext-transmit-03 (work in progress),
August 2013. August 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
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