Deprecation of Type 0 Routing Headers in IPv6
RFC 5095

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Network Working Group                                           J. Abley
Request for Comments: 5095                                       Afilias
Updates: 2460, 4294                                            P. Savola
Category: Standards Track                                      CSC/FUNET
                                                         G. Neville-Neil
                                                 Neville-Neil Consulting
                                                           December 2007

             Deprecation of Type 0 Routing Headers in IPv6

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   The functionality provided by IPv6's Type 0 Routing Header can be
   exploited in order to achieve traffic amplification over a remote
   path for the purposes of generating denial-of-service traffic.  This
   document updates the IPv6 specification to deprecate the use of IPv6
   Type 0 Routing Headers, in light of this security concern.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Deprecation of RH0  . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
     4.1.  Ingress Filtering . . . . . . . . . . . . . . . . . . . . . 3
     4.2.  Firewall Policy . . . . . . . . . . . . . . . . . . . . . . 3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5

Abley, et al.               Standards Track                     [Page 1]
RFC 5095                   Deprecation of RH0              December 2007

1.  Introduction

   [RFC2460] defines an IPv6 extension header called "Routing Header",
   identified by a Next Header value of 43 in the immediately preceding
   header.  A particular Routing Header subtype denoted as "Type 0" is
   also defined.  Type 0 Routing Headers are referred to as "RH0" in
   this document.

   A single RH0 may contain multiple intermediate node addresses, and
   the same address may be included more than once in the same RH0.
   This allows a packet to be constructed such that it will oscillate
   between two RH0-processing hosts or routers many times.  This allows
   a stream of packets from an attacker to be amplified along the path
   between two remote routers, which could be used to cause congestion
   along arbitrary remote paths and hence act as a denial-of-service
   mechanism.  An 88-fold amplification has been demonstrated using this
   technique [CanSecWest07].

   This attack is particularly serious in that it affects the entire
   path between the two exploited nodes, not only the nodes themselves
   or their local networks.  Analogous functionality may be found in the
   IPv4 source route option, but the opportunities for abuse are greater
   with RH0 due to the ability to specify many more intermediate node
   addresses in each packet.

   The severity of this threat is considered to be sufficient to warrant
   deprecation of RH0 entirely.  A side effect is that this also
   eliminates benign RH0 use-cases; however, such applications may be
   facilitated by future Routing Header specifications.

   Potential problems with RH0 were identified in 2001 [Security].  In
   2002 a proposal was made to restrict Routing Header processing in
   hosts [Hosts].  These efforts resulted in the modification of the
   Mobile IPv6 specification to use the type 2 Routing Header instead of
   RH0 [RFC3775].  Vishwas Manral identified various risks associated
   with RH0 in 2006 including the amplification attack; several of these
   vulnerabilities (together with other issues) were later documented in
   [RFC4942].

   A treatment of the operational security implications of RH0 was
   presented by Philippe Biondi and Arnaud Ebalard at the CanSecWest
   conference in Vancouver, 2007 [CanSecWest07].  This presentation
   resulted in widespread publicity for the risks associated with RH0.

   This document updates [RFC2460] and [RFC4294].

Abley, et al.               Standards Track                     [Page 2]
RFC 5095                   Deprecation of RH0              December 2007

2.  Definitions

   RH0 in this document denotes the IPv6 Extension Header type 43