--- 1/draft-ietf-6man-overlap-fragment-01.txt 2009-03-09 18:12:05.000000000 +0100 +++ 2/draft-ietf-6man-overlap-fragment-02.txt 2009-03-09 18:12:05.000000000 +0100 @@ -1,65 +1,73 @@ 6man Working Group S. Krishnan Internet-Draft Ericsson -Updates: 2460 (if approved) November 3, 2008 +Updates: 2460 (if approved) March 8, 2009 Intended status: Standards Track -Expires: May 7, 2009 +Expires: September 9, 2009 Handling of overlapping IPv6 fragments - draft-ietf-6man-overlap-fragment-01 + draft-ietf-6man-overlap-fragment-02 Status of this Memo - By submitting this Internet-Draft, each author represents that any - applicable patent or other IPR claims of which he or she is aware - have been or will be disclosed, and any of which he or she becomes - aware will be disclosed, in accordance with Section 6 of BCP 79. + This Internet-Draft is submitted to IETF in full conformance with the + provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. - This Internet-Draft will expire on May 7, 2009. + This Internet-Draft will expire on September 9, 2009. + +Copyright Notice + + Copyright (c) 2009 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 in effect on the date of + publication of this document (http://trustee.ietf.org/license-info). + Please review these documents carefully, as they describe your rights + and restrictions with respect to this document. Abstract The fragmentation and reassembly algorithm specified in the base IPv6 specification allows fragments to overlap. This document demonstrates the security issues with allowing overlapping fragments and updates the IPv6 specification to explicitly forbid overlapping fragments. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . . 3 2. Overlapping Fragments . . . . . . . . . . . . . . . . . . . . . 3 - 3. The attack . . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 4. Recommendation . . . . . . . . . . . . . . . . . . . . . . . . 5 - 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 + 3. The attack . . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 4. Recommendation . . . . . . . . . . . . . . . . . . . . . . . . 6 + 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7. Normative References . . . . . . . . . . . . . . . . . . . . . 6 - Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 - Intellectual Property and Copyright Statements . . . . . . . . . . 7 + Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction Fragmentation is used in IPv6 when the IPv6 packet will not fit inside the path MTU to its destination. When fragmentation is performed an IPv6 node uses a fragment header as specified in section 4.5 of the IPv6 base specification [RFC2460] to break down the datagram into smaller fragments that will fit in the path MTU. The destination node receives these fragments and reassembles them. The algorithm specified for fragmentation in [RFC2460] does not prevent @@ -174,25 +182,23 @@ Note that this attack is much more serious in IPv6 than in IPv4. In IPv4 the overlapping part of the TCP header did not include the source and destination ports. In IPv6 the attack can easily work to replace the source or destination port with an overlapping fragment. 4. Recommendation IPv6 nodes transmitting datagrams that need to be fragmented MUST NOT create overlapping fragments. IPv6 nodes that receive a fragment that overlaps with a previously received fragment MUST cease the - reassembly process and MUST ignore further fragments with the same - IPv6 Source Address, IPv6 Destination Address and Fragment - Identification. It MUST also discard the previously received - fragments with the same IPv6 Source Address, IPv6 Destination Address - and Fragment Identification. + reassembly process and MUST discard the previously received fragments + with the same IPv6 Source Address, IPv6 Destination Address and + Fragment Identification. 5. Security Considerations This document discusses an attack that can be used to bypass IPv6 firewalls using overlapping fragments. It recommends disallowing overlapping fragments in order to prevent this attack. 6. IANA Considerations This document does not require any action from the IANA. @@ -215,50 +221,10 @@ Author's Address Suresh Krishnan Ericsson 8400 Blvd Decarie Town of Mount Royal, Quebec Canada Email: suresh.krishnan@ericsson.com - -Full Copyright Statement - - Copyright (C) The IETF Trust (2008). - - This document is subject to the rights, licenses and restrictions - contained in BCP 78, and except as set forth therein, the authors - retain all their rights. - - This document and the information contained herein are provided on an - "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS - OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND - THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS - OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF - THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED - WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - -Intellectual Property - - The IETF takes no position regarding the validity or scope of any - Intellectual Property Rights or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; nor does it represent that it has - made any independent effort to identify any such rights. Information - on the procedures with respect to rights in RFC documents can be - found in BCP 78 and BCP 79. - - Copies of IPR disclosures made to the IETF Secretariat and any - assurances of licenses to be made available, or the result of an - attempt made to obtain a general license or permission for the use of - such proprietary rights by implementers or users of this - specification can be obtained from the IETF on-line IPR repository at - http://www.ietf.org/ipr. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights that may cover technology that may be required to implement - this standard. Please address the information to the IETF at - ietf-ipr@ietf.org.