Internet Engineering Task Force (IETF) S. Krishnan
Request for Comments: 6169 Ericsson
Category: Informational D. Thaler
ISSN: 2070-1721 Microsoft
J. Hoagland
Symantec
April 2011
Security Concerns with IP Tunneling
Abstract
A number of security concerns with IP tunnels are documented in this
memo. The intended audience of this document includes network
administrators and future protocol developers. The primary intent of
this document is to raise the awareness level regarding the security
issues with IP tunnels as deployed and propose strategies for the
mitigation of those issues.
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/rfc6169.
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Copyright (c) 2011 IETF Trust and the persons identified as the
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Krishnan, et al. Informational [Page 1]RFC 6169 Tunneling Security Concerns April 2011
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than English.
Table of Contents
1. Introduction ....................................................2
2. Tunnels May Bypass Security .....................................3
2.1. Network Security Bypass ....................................3
2.2. IP Ingress and Egress Filtering Bypass .....................5
2.3. Source Routing after the Tunnel Client .....................6
3. Challenges in Inspecting and Filtering Content of
Tunneled Data Packets ...........................................7
3.1. Inefficiency of Selective Network Filtering of All
Tunneled Packets ...........................................7
3.2. Problems with Deep Packet Inspection of Tunneled
Data Packets ...............................................8
4. Increased Exposure Due to Tunneling .............................9
4.1. NAT Holes Increase Attack Surface ..........................9
4.2. Exposure of a NAT Hole ....................................11
4.3. Public Tunnels Widen Holes in Restricted NATs .............12
5. Tunnel Address Concerns ........................................13
5.1. Feasibility of Guessing Tunnel Addresses ..................13
5.2. Profiling Targets Based on Tunnel Address .................14
6. Additional Security Concerns ...................................15
6.1. Attacks Facilitated by Changing Tunnel Server Setting .....15
7. Mechanisms to Secure the Use of Tunnels ........................17
8. Acknowledgments ................................................18
9. Security Considerations ........................................18
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