--- 1/draft-ietf-6man-oversized-header-chain-07.txt 2013-10-02 12:14:26.581522675 -0700 +++ 2/draft-ietf-6man-oversized-header-chain-08.txt 2013-10-02 12:14:26.601523170 -0700 @@ -1,21 +1,21 @@ 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: March 14, 2014 R. Bonica +Expires: April 5, 2014 R. Bonica Juniper Networks - September 10, 2013 + October 2, 2013 Implications of Oversized IPv6 Header Chains - draft-ietf-6man-oversized-header-chain-07 + draft-ietf-6man-oversized-header-chain-08 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 @@ -31,21 +31,21 @@ 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 March 14, 2014. + This Internet-Draft will expire on April 5, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. 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 @@ -155,70 +155,73 @@ 4. Motivation Many forwarding devices implement stateless firewalls. A stateless firewall enforces a forwarding policy on packet-by-packet basis. In order to enforce its forwarding policy, the stateless firewall may need to glean information from both the IPv6 and upper-layer headers. For example, assume that a stateless firewall discards all traffic received from an interface unless it destined for a particular TCP port on a particular IPv6 address. When this firewall is presented - with a fragmented packet, and the entire header chain is contained - within the first fragment, the firewall discards the first fragment - and allows subsequent fragments to pass. Because the first fragment - was discarded, the packet cannot be reassembled at the destination. - Insomuch as the packet cannot be reassembled, the forwarding policy - is enforced. + with a fragmented packet that is destined for a different TCP port, + and the entire header chain is contained within the first fragment, + the firewall discards the first fragment and allows subsequent + fragments to pass. Because the first fragment was discarded, the + packet cannot be reassembled at the destination. Insomuch as the + packet cannot be reassembled, the forwarding policy is enforced. However, when the firewall is presented with a fragmented packet and the header chain spans multiple fragments, the first fragment does not contain enough information for the firewall to enforce its forwarding policy. Lacking sufficient information, the stateless firewall either forwards or discards that fragment. Regardless of the action that it takes, it may fail to enforce its forwarding policy. 5. Updates to RFC 2460 When a host fragments a IPv6 datagram, it MUST include the entire header chain in the first fragment. A host that receives a first-fragment that does not satisfy the - above-stated requirement SHOULD discard that packet, and also MAY - send an ICMPv6 error message to the source address of the offending - packet (subject to the rules for ICMPv6 errors specified in - [RFC4443]). + above- stated requirement SHOULD discard the packet (e.g., including + a configuration option that allows such fragments to be accepted for + backwards compatibility) and SHOULD send an ICMPv6 error message to + 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 receives an IPv6 first-fragment that does not satisfy the above- stated requirements MAY discard that packet, and MAY send an ICMPv6 error message to the source address of the offending packet (subject to the rules for ICMPv6 error messages specified in [RFC4443]). Intermediate systems having this capability SHOULD support configuration (e.g. enable/disable) of whether such packets are dropped or not by the intermediate system. If a host or intermediate system discards a first-fragment because it does not satisfy the above-stated requirements, and sends an ICMPv6 error message due to the discard, then the ICMPv6 error message MUST be Type 4 ("Parameter Problem") and MUST use Code TBD ("First- fragment has incomplete IPv6 Header Chain"). The Pointer field contained by the ICMPv6 Parameter Problem message MUST be set to - zero. + zero. Whether a host or intermediate system originates this ICMP + message, its format is identical. 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. + that the header chain length does not exceed the IPv6 minimum MTU + [RFC2460]. 6. IANA Considerations IANA is requested to add a the following entry to the "Reason Code" registry for ICMPv6 "Type 4 - Parameter Problem" messages: CODE NAME/DESCRIPTION TBD IPv6 first-fragment has incomplete IPv6 header chain 7. Security Considerations @@ -273,22 +276,22 @@ [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol 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] Carpenter, B. and S. Jiang, "Transmission and Processing of IPv6 Extension Headers", - draft-ietf-6man-ext-transmit-03 (work in progress), - August 2013. + draft-ietf-6man-ext-transmit-04 (work in progress), + September 2013. 9.2. Informative References [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, May 2000. [RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed Networks", BCP 84, RFC 3704, March 2004.