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Security Implications of Predictable Fragment Identification Values (RFC7739)

IP.com Disclosure Number: IPCOM000245089D
Original Publication Date: 2016-Feb-01
Included in the Prior Art Database: 2016-Feb-08
Document File: 40 page(s) / 46K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

F. Gont: AUTHOR

Abstract

IPv6 specifies the Fragment Header, which is employed for the fragmentation and reassembly mechanisms. The Fragment Header contains an "Identification" field that, together with the IPv6 Source Address and the IPv6 Destination Address of a packet, identifies fragments that correspond to the same original datagram, such that they can be reassembled together by the receiving host. The only requirement for setting the Identification field is that its value must be different than that employed for any other fragmented datagram sent recently with the same Source Address and Destination Address.

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Internet Engineering Task Force (IETF)                           F. Gont Request for Comments: 7739                           Huawei Technologies Category: Informational                                    February 2016 ISSN: 2070-1721

   Security Implications of Predictable Fragment Identification Values

Abstract

   IPv6 specifies the Fragment Header, which is employed for the

   fragmentation and reassembly mechanisms.  The Fragment Header

   contains an "Identification" field that, together with the IPv6

   Source Address and the IPv6 Destination Address of a packet,

   identifies fragments that correspond to the same original datagram,

   such that they can be reassembled together by the receiving host.

   The only requirement for setting the Identification field is that the

   corresponding value must be different than that employed for any

   other fragmented datagram sent recently with the same Source Address

   and Destination Address.  Some implementations use a simple global

   counter for setting the Identification field, thus leading to

   predictable Identification values.  This document analyzes the

   security implications of predictable Identification values, and

   provides implementation guidance for setting the Identification field

   of the Fragment Header, such that the aforementioned security

   implications are mitigated.

Status of This Memo

   This document is not an Internet Standards Track specification; it is    published for informational purposes.

   This document is a product of the Internet Engineering Task Force    (IETF).  It represents the consensus of the IETF community.  It has    received public review and has been approved for publication by the    Internet Engineering Steering Group (IESG).  Not all documents    approved by the IESG are a candidate for any level of Internet    Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,    and how to provide feedback on it may be obtained at    http://www.rfc-editor.org/info/rfc7739.

Gont                          Informational                     [Page 1]
 RFC 7739        Implications of Predictable Fragment IDs   February 2016

 Copyright Notice

   Copyright (c) 2016 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    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 desc...