Measures for Making DNS More Resilient against Forged Answers
RFC 5452
Document | Type |
RFC - Proposed Standard
(January 2009; No errata)
Updates RFC 2181
|
|
---|---|---|---|
Authors | Bert Hubert , Remco Mook | ||
Last updated | 2018-12-20 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 5452 (Proposed Standard) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Mark Townsley | ||
Send notices to | (None) |
Network Working Group A. Hubert Request for Comments: 5452 Netherlabs Computer Consulting BV. Updates: 2181 R. van Mook Category: Standards Track Equinix January 2009 Measures for Making DNS More Resilient against Forged Answers 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. Copyright Notice Copyright (c) 2009 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. Abstract The current Internet climate poses serious threats to the Domain Name System. In the interim period before the DNS protocol can be secured more fully, measures can already be taken to harden the DNS to make 'spoofing' a recursing nameserver many orders of magnitude harder. Even a cryptographically secured DNS benefits from having the ability to discard bogus responses quickly, as this potentially saves large amounts of computation. By describing certain behavior that has previously not been standardized, this document sets out how to make the DNS more resilient against accepting incorrect responses. This document updates RFC 2181. Hubert & van Mook Standards Track [Page 1] RFC 5452 DNS Resilience against Forged Answers January 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements and Definitions . . . . . . . . . . . . . . . . . 4 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Description of DNS Spoofing . . . . . . . . . . . . . . . . . 5 4. Detailed Description of Spoofing Scenarios . . . . . . . . . . 6 4.1. Forcing a Query . . . . . . . . . . . . . . . . . . . . . 6 4.2. Matching the Question Section . . . . . . . . . . . . . . 7 4.3. Matching the ID Field . . . . . . . . . . . . . . . . . . 7 4.4. Matching the Source Address of the Authentic Response . . 7 4.5. Matching the Destination Address and Port of the Authentic Response . . . . . . . . . . . . . . . . . . . . 8 4.6. Have the Response Arrive before the Authentic Response . . 8 5. Birthday Attacks . . . . . . . . . . . . . . . . . . . . . . . 9 6. Accepting Only In-Domain Records . . . . . . . . . . . . . . . 9 7. Combined Difficulty . . . . . . . . . . . . . . . . . . . . . 10 7.1. Symbols Used in Calculation . . . . . . . . . . . . . . . 10 7.2. Calculation . . . . . . . . . . . . . . . . . . . . . . . 11 8. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Repetitive Spoofing Attempts for a Single Domain Name . . 13 9. Forgery Countermeasures . . . . . . . . . . . . . . . . . . . 13 9.1. Query Matching Rules . . . . . . . . . . . . . . . . . . . 13 9.2. Extending the Q-ID Space by Using Ports and Addresses . . 14 9.2.1. Justification and Discussion . . . . . . . . . . . . . 14 9.3. Spoof Detection and Countermeasure . . . . . . . . . . . . 15 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 12.1. Normative References . . . . . . . . . . . . . . . . . . . 16 12.2. Informative References . . . . . . . . . . . . . . . . . . 17 Hubert & van Mook Standards Track [Page 2] RFC 5452 DNS Resilience against Forged Answers January 2009 1. Introduction This document describes several common problems in DNS implementations, which, although previously recognized, remain largely unsolved. Besides briefly recapping these problems, this document contains rules that, if implemented, make complying resolvers vastly more resistant to the attacks described. The goal is to make the existing DNS as secure as possible within the current protocol boundaries. The words below are aimed at authors of resolvers: it is up to operators to decide which nameserver implementation to use, or whichShow full document text