Layer 3 Virtual Private Network (VPN) Tunnel Traffic Leakages in Dual-Stack Hosts/Networks
RFC 7359

 
Document Type RFC - Informational (August 2014; No errata)
Last updated 2014-08-26
Replaces draft-gont-opsec-vpn-leakages
Stream IETF
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Stream WG state Submitted to IESG for Publication Jul 2013
Consensus Yes
Document shepherd Warren Kumari
Shepherd write-up Show (last changed 2013-10-21)
IESG IESG state RFC 7359 (Informational)
Telechat date
Responsible AD Joel Jaeggli
Send notices to opsec-chairs@ietf.org, draft-ietf-opsec-vpn-leakages@ietf.org
IANA IANA review state IANA OK - No Actions Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                           F. Gont
Request for Comments: 7359                           Huawei Technologies
Category: Informational                                      August 2014
ISSN: 2070-1721

     Layer 3 Virtual Private Network (VPN) Tunnel Traffic Leakages
                      in Dual-Stack Hosts/Networks

Abstract

   The subtle way in which the IPv6 and IPv4 protocols coexist in
   typical networks, together with the lack of proper IPv6 support in
   popular Virtual Private Network (VPN) tunnel products, may
   inadvertently result in VPN tunnel traffic leakages.  That is,
   traffic meant to be transferred over an encrypted and integrity-
   protected VPN tunnel may leak out of such a tunnel and be sent in the
   clear on the local network towards the final destination.  This
   document discusses some scenarios in which such VPN tunnel traffic
   leakages may occur as a result of employing IPv6-unaware VPN
   software.  Additionally, this document offers possible mitigations
   for this issue.

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/rfc7359.

Gont                          Informational                     [Page 1]
RFC 7359                  VPN Traffic Leakages               August 2014

IESG Note

   This document describes a problem of information leakage in VPN
   software and attributes that problem to the software's inability to
   deal with IPv6.  We do not think this is an appropriate
   characterization of the problem.  It is true that when a device
   supports more than one address family, the inability to apply policy
   to more than one address family on that device is a defect.  Despite
   that, inadvertent or maliciously induced information leakage may also
   occur due to the existence of any unencrypted interface allowed on
   the system, including the configuration of split tunnels in the VPN
   software itself.  While there are some attacks that are unique to an
   IPv6 interface, the sort of information leakage described by this
   document is a general problem that is not unique to the situation of
   IPv6-unaware VPN software.  We do not think this document
   sufficiently describes the general issue.

Copyright Notice

   Copyright (c) 2014 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 described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Gont                          Informational                     [Page 2]
RFC 7359                  VPN Traffic Leakages               August 2014

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  IPv4 and IPv6 Coexistence . . . . . . . . . . . . . . . . . .   5
   4.  Virtual Private Networks in IPv4/IPv6 Dual-Stack
       Hosts/Networks  . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Inadvertent VPN Tunnel Traffic Leakages in Legitimate
       Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  VPN Tunnel Traffic Leakage Attacks  . . . . . . . . . . . . .   7
   7.  Mitigations to VPN Tunnel Traffic Leakage Vulnerabilities . .   8
     7.1.  Fixing VPN Client Software  . . . . . . . . . . . . . . .   8
     7.2.  Operational Mitigations . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
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