Interoperable Domain Name System (DNS) Server Cookies
RFC 9018

Document Type RFC - Proposed Standard (April 2021; No errata)
Updates RFC 7873
Authors Ondřej Surý  , Willem Toorop  , Donald Eastlake  , Mark Andrews 
Last updated 2021-04-05
Replaces draft-eastlake-dnsop-server-cookies, draft-sury-toorop-dnsop-server-cookies
Stream Internet Engineering Task Force (IETF)
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Reviews
Stream WG state Submitted to IESG for Publication
Document shepherd Tim Wicinski
Shepherd write-up Show (last changed 2020-11-19)
IESG IESG state RFC 9018 (Proposed Standard)
Action Holders
(None)
Consensus Boilerplate Yes
Telechat date
Responsible AD Warren Kumari
Send notices to tjw.ietf@gmail.com
IANA IANA review state Version Changed - Review Needed
IANA action state RFC-Ed-Ack


Internet Engineering Task Force (IETF)                           O. Sury
Request for Comments: 9018                   Internet Systems Consortium
Updates: 7873                                                  W. Toorop
Category: Standards Track                                     NLnet Labs
ISSN: 2070-1721                                          D. Eastlake 3rd
                                                  Futurewei Technologies
                                                              M. Andrews
                                             Internet Systems Consortium
                                                              April 2021

         Interoperable Domain Name System (DNS) Server Cookies

Abstract

   DNS Cookies, as specified in RFC 7873, are a lightweight DNS
   transaction security mechanism that provide limited protection to DNS
   servers and clients against a variety of denial-of-service
   amplification, forgery, or cache-poisoning attacks by off-path
   attackers.

   This document updates RFC 7873 with precise directions for creating
   Server Cookies so that an anycast server set including diverse
   implementations will interoperate with standard clients, with
   suggestions for constructing Client Cookies in a privacy-preserving
   fashion, and with suggestions on how to update a Server Secret.  An
   IANA registry listing the methods and associated pseudorandom
   function suitable for creating DNS Server Cookies has been created
   with the method described in this document as the first and, as of
   the time of publication, only entry.

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9018.

Copyright Notice

   Copyright (c) 2021 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
   (https://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.

Table of Contents

   1.  Introduction
     1.1.  Terminology and Definitions
   2.  Changes to RFC 7873
   3.  Constructing a Client Cookie
   4.  Constructing a Server Cookie
     4.1.  The Version Sub-Field
     4.2.  The Reserved Sub-Field
     4.3.  The Timestamp Sub-Field
     4.4.  The Hash Sub-Field
   5.  Updating the Server Secret
   6.  Cookie Algorithms
   7.  IANA Considerations
   8.  Security and Privacy Considerations
     8.1.  Client Cookie Construction
     8.2.  Server Cookie Construction
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Appendix A.  Test Vectors
     A.1.  Learning a New Server Cookie
     A.2.  The Same Client Learning a Renewed (Fresh) Server Cookie
     A.3.  Another Client Learning a Renewed Server Cookie
     A.4.  IPv6 Query with Rolled Over Secret
   Appendix B.  Implementation Status
   Acknowledgements
   Authors' Addresses

1.  Introduction

   DNS Cookies, as specified in [RFC7873], are a lightweight DNS
   transaction security mechanism that provide limited protection to DNS
   servers and clients against a variety of denial-of-service
   amplification, forgery, or cache-poisoning attacks by off-path
   attackers.  This document specifies a means of producing
   interoperable cookies so that an anycast server set including diverse
   implementations can be easily configured to interoperate with
   standard clients.  Also, single-implementation or non-anycast
   services can benefit from a well-studied standardized algorithm for
   which the behavioral and security characteristics are more widely
   known.

   The threats considered for DNS Cookies and the properties of the DNS
   Security features other than DNS Cookies are discussed in [RFC7873].

   In Section 6 of [RFC7873], for simplicity, it is "RECOMMENDED that
   the same Server Secret be used by each DNS server in a set of anycast
   servers."  However, how precisely a Server Cookie is calculated from
   this Server Secret is left to the implementation.

   This guidance has led to a gallimaufry of DNS Cookie implementations,
   calculating the Server Cookie in different ways.  As a result, DNS
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