Network Working Group W. Kumari Internet-Draft Google Intended status: Informational November 22, 2013 Expires: May 26, 2014 A method for mitigating namespace collisions draft-wkumari-dnsop-defense-collision-mitigate-03 Abstract This document outlines a possible, but not recommended, method to mitigate the effect of collisions in the DNS namespace by providing a means for end users to disambiguate the conflict. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on May 26, 2014. Copyright Notice Copyright (c) 2013 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. Kumari Expires May 26, 2014 [Page 1] Internet-Draft DNS Collision Mitigation November 2013 Table of Contents 1. Introduction / Background . . . . . . . . . . . . . . . . . . 2 2. Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Implementation / Disclaimers . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction / Background Collisions in the DNS occur in multiple ways; one common case is that an organization has used an sub-domain (foo) of their primary domain (example.com) for corporate infrastructure, and then the string "foo" is delegated as a TLD. When an employee of the organization enters 'www.foo', is the goal to reach a machine in the internal namespace (www.foo.example.com) or the hostname 'www' in the 'foo' TLD? This document describes a means of disambiguating these, and similar cases. Implementation of these methods are not recommended; they are documented here to explain some of the pitfalls with approaches like these. 2. Mitigation The mitigation described in this document involves presenting the multiple options to the user, and allowing them to indicate which of the names is the one they were trying to reach. The mitigation would lookup the name in multiple namespaces. When if a conflict is detected, it would then provide a means for the user to indicate which one of the colliding names they wish to connect to, and return the disambiguated answer to the application. An additional feature could be for the mitigation to cache the user's choice, and / or provide a means to set priorities. This could be accomplished in a number of ways, including: Intercepting the resolution requests from the application in a "shim" type library Replacing the resolver library entirelyT Kumari Expires May 26, 2014 [Page 2] Internet-Draft DNS Collision Mitigation November 2013 Integrating this type of mitigation into applications (some web browsers already do something similar to this) Proxying the request to a server that provides an interstitial page that allows the user to indicate the intended name (for applications such as HTTP requests) There are a number of issues with this solution, including but not limited to: o There may not be a human available to disambiguate the answer (unattended machines, mail servers, etc.) o The human / user may have no idea which is the correct choice, especially in the case of a phishing attackor other malicious intent o The additional latency introduced may cause the originating application to time out o The user experience would be time consuming to select each site and subsite intended (www.intranet, images.intranet, etc.) o Caching the responses could lead to problems when the user changes location (internal sites would fail when offsite, or otherwise lead to incorrect sites being loaded) For these and other reasons, implementation of this technique is not recommended. 3. Implementation / Disclaimers This document does not reference an implementation. Due to the numerous issues described above, we do not recommend this solution be implemented. We do not recommend that this be viewed as a solution to the namespace collision problem. This is a very slight mitigation. It should not be viewed as a solution to the "namespace collision" issue. 4. IANA Considerations This document contains no IANA considerations. 5. Security Considerations While this method may make some users more aware of which version of a name they are going to (and so careful users may avoid some Kumari Expires May 26, 2014 [Page 3] Internet-Draft DNS Collision Mitigation November 2013 phishing attacks), the security risks described above outweigh this potential benefit. There are numerous security implications in this approach, including leaking internal names (secret-project.corp.example.com), users being tricked into selecting the incorrect choice when trying to disambiguate answers, etc. For these reasons, it is not recommended that this solution be deployed. 6. Acknowledgements The authors wish to thank some folk, including Fred Baker, Bob Braden, Carsten Bormann, Nevil Brownlee, Eric Burger, Brian Carpenter, Benoit Claise, Keith Drage, Martin J. Duerst, David Harrington, Paul Hoffamn, John Levine and Ted Lemon, 7. References Appendix A. Changes / Author Notes. [RFC Editor: Please remove this section before publication.] From -00 to -01. o Nothing changed in the template. from -01 to -02 o Rewrite. Less flippant. From -02 to -03: o Changed to Informational. Suggestion from ISE:"I see only one remaining thing - you've changed its Intended Status to Experimental. I think Informational would be better, since 'Experimental' implies that you have an implementation and are publishing the document so that others can try it too. " Author's Address Kumari Expires May 26, 2014 [Page 4] Internet-Draft DNS Collision Mitigation November 2013 Warren Kumari Google 1600 Amphitheatre Parkway Mountain View, CA 94043 US Email: warren@kumari.net Kumari Expires May 26, 2014 [Page 5]