[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 draft-ietf-6man-oversized-header-chain

IPv6 maintenance Working Group (6man)                            F. Gont
Internet-Draft                                    SI6 Networks / UTN-FRH
Updates: 2460 (if approved)                                    V. Manral
Intended status: Standards Track                   Hewlett-Packard Corp.
Expires: December 15, 2012                                 June 13, 2012


  Security and Interoperability Implications of Oversized IPv6 Header
                                 Chains
               draft-gont-6man-oversized-header-chain-02

Abstract

   The IPv6 specification allows IPv6 header chains of an arbitrary
   size.  The specification also allows options which can in turn extend
   each of the headers.  In those scenarios in which the IPv6 header
   chain or options are unusually long and packets are fragmented, or
   scenarios in which the fragment size is very small, the first
   fragment of a packet may fail to include the entire IPv6 header
   chain.  This document discusses the interoperability and security
   problems of such traffic, and updates RFC 2460 such that the first
   fragment of a packet is required to contain the entire IPv6 header
   chain.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may not be modified,
   and derivative works of it may not be created, and it may not be
   published except as an Internet-Draft.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 15, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




Gont & Manral           Expires December 15, 2012               [Page 1]

Internet-Draft   Implications of Oversized Header Chains       June 2012


   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Interoperability Implications of Oversized IPv6 Header
       Chains . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Forwarding Implications of Oversized IPv6 Header Chains  . . .  5
   4.  Security Implications of Oversized IPv6 Header Chains  . . . .  6
   5.  Updating RFC 2460  . . . . . . . . . . . . . . . . . . . . . .  7
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

























Gont & Manral           Expires December 15, 2012               [Page 2]

Internet-Draft   Implications of Oversized Header Chains       June 2012


1.  Introduction

   [RFC2460] allows for an IPv6 header chain of an arbitrary size.  It
   also allows the headers themselves to have options, which can change
   the size of the headers.  In those scenarios in which the IPv6 header
   chain is unusually long and packets are fragmented, or scenarios in
   which the fragment size is very small, the first fragment of a packet
   may fail to include the entire IPv6 header chain.  This document
   discusses the interoperability and security problems of such traffic,
   and updates RFC 2460 such that the first fragment of a fragmented
   datagram is required to contain the entire IPv6 header chain.

   It should be noted that this requirement does not preclude the use of
   e.g.  IPv6 jumbo payloads but instead merely requires that all
   *headers*, starting from IPv6 base header and continuing up to the
   upper layer header (e.g.  TCP or the like) be present in the first
   fragment.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].






























Gont & Manral           Expires December 15, 2012               [Page 3]

Internet-Draft   Implications of Oversized Header Chains       June 2012


2.  Interoperability Implications of Oversized IPv6 Header Chains

   Some transition technologies, such as NAT64 [RFC6146], may need to
   have access to the entire IPv6 header chain in order to associate an
   incoming IPv6 packet with an ongoing "session".

      For instance, Section 3.4 of [RFC6146] states that "The NAT64 MAY
      require that the UDP, TCP, or ICMP header be completely contained
      within the fragment that contains fragment offset equal to zero".

   Failure to include the entire IPv6 header chain in the first-fragment
   may cause the translation function to fail, with the corresponding
   packets being dropped.






































Gont & Manral           Expires December 15, 2012               [Page 4]

Internet-Draft   Implications of Oversized Header Chains       June 2012


3.  Forwarding Implications of Oversized IPv6 Header Chains

   A lot of the switches and Routers in the internet do hardware based
   forwarding.  To be able to achieve a level of throughput, there is a
   fixed maximum number of clock cycles dedicated to each packet.
   However with the use of unlimited options and header interleaving,
   larger packets with a lot of interleaving have to be forwarded to the
   software.  It is for this reason that the maximum size of valid
   packets with interleaved headers needs to be limited.










































Gont & Manral           Expires December 15, 2012               [Page 5]

Internet-Draft   Implications of Oversized Header Chains       June 2012


4.  Security Implications of Oversized IPv6 Header Chains

   Most firewalls enforce they filtering policy based on the following
   parameters:

   o  Source IP address

   o  Destination IP address

   o  Protocol type

   o  Source port number

   o  Destination port number

   Some firewalls reassemble fragmented packets before applying a
   filtering policy, and thus always have the aforementioned information
   available when deciding whether to allow or block a packet.  However,
   other stateless firewalls (generally prevalent on small/ home office
   equipment) do not reassemble fragmented traffic, and hence have to
   enforce their filtering policy based on the information contained in
   the received fragment, as opposed to the information contained in the
   reassembled datagram.

   When presented with fragmented traffic, many of such firewalls
   typically enforce their policy only on the first fragment of a
   packet, based on the assumption that if the first fragment is
   dropped, reassembly of the corresponding datagram will fail, and thus
   such datagram will be effectively blocked.  However, if the first
   fragment fails to include the entire IPv6 header chain, they may have
   no option other than "blindly" allowing or blocking the corresponding
   fragment.  If they blindly allow the packet, then the firewall can be
   easily circumvented by intentionally sending fragmented packets that
   fail to include the entire IPv6 header chain in the first fragment.
   On the other hand, first-fragments that fail to include the entire
   IPv6 header chain have never been formally deprecated and thus, in
   theory, might be legitimately generated.














Gont & Manral           Expires December 15, 2012               [Page 6]

Internet-Draft   Implications of Oversized Header Chains       June 2012


5.  Updating RFC 2460

   If a packet is fragmented, the first fragment of the packet (i.e.,
   that with a Fragment Offset of 0) MUST contain the entire IPv6 header
   chain.














































Gont & Manral           Expires December 15, 2012               [Page 7]

Internet-Draft   Implications of Oversized Header Chains       June 2012


6.  IANA Considerations

   There are no IANA registries within this document.  The RFC-Editor
   can remove this section before publication of this document as an
   RFC.














































Gont & Manral           Expires December 15, 2012               [Page 8]

Internet-Draft   Implications of Oversized Header Chains       June 2012


7.  Security Considerations

   This document describes the interoperability and security
   implications of IPv6 packets or first-fragments that fail to include
   the entire IPv6 header chain.  The security implications include the
   possibility of an attacker evading network security controls such as
   firewalls and Network Intrusion Detection Systems (NIDS) [CPNI-IPv6].

   This document updates RFC 2460 such that those packets are forbidden,
   thus preventing the aforementioned issues.









































Gont & Manral           Expires December 15, 2012               [Page 9]

Internet-Draft   Implications of Oversized Header Chains       June 2012


8.  Acknowledgements

   The authors would like to thank (in alphabetical order) Ran Atkinson
   and Dave Thaler for providing valuable comments on earlier versions
   of this document.














































Gont & Manral           Expires December 15, 2012              [Page 10]

Internet-Draft   Implications of Oversized Header Chains       June 2012


9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

9.2.  Informative References

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

   [CPNI-IPv6]
              Gont, F., "Security Assessment of the Internet Protocol
              version 6 (IPv6)",  UK Centre for the Protection of
              National Infrastructure, (available on request).































Gont & Manral           Expires December 15, 2012              [Page 11]

Internet-Draft   Implications of Oversized Header Chains       June 2012


Authors' Addresses

   Fernando Gont
   SI6 Networks / UTN-FRH
   Evaristo Carriego 2644
   Haedo, Provincia de Buenos Aires  1706
   Argentina

   Phone: +54 11 4650 8472
   Email: fgont@si6networks.com
   URI:   http://www.si6networks.com


   Vishwas Manral
   Hewlett-Packard Corp.
   191111 Pruneridge Ave.
   Cupertino, CA  95014
   US

   Phone: 408-447-1497
   Email: vishwas.manral@hp.com
   URI:





























Gont & Manral           Expires December 15, 2012              [Page 12]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/