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 which
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