Secret Key Transaction Authentication for DNS (TSIG)
RFC 8945

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Internet Engineering Task Force (IETF)                         F. Dupont
Request for Comments: 8945                                           ISC
STD: 93                                                        S. Morris
Obsoletes: 2845, 4635                                       Unaffiliated
Category: Standards Track                                       P. Vixie
ISSN: 2070-1721                                                 Farsight
                                                         D. Eastlake 3rd
                                                               Futurewei
                                                          O. Gudmundsson
                                                              Cloudflare
                                                           B. Wellington
                                                                  Akamai
                                                           November 2020

          Secret Key Transaction Authentication for DNS (TSIG)

Abstract

   This document describes a protocol for transaction-level
   authentication using shared secrets and one-way hashing.  It can be
   used to authenticate dynamic updates to a DNS zone as coming from an
   approved client or to authenticate responses as coming from an
   approved name server.

   No recommendation is made here for distributing the shared secrets;
   it is expected that a network administrator will statically configure
   name servers and clients using some out-of-band mechanism.

   This document obsoletes RFCs 2845 and 4635.

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/rfc8945.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   Without obtaining an adequate license from the person(s) controlling
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   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction
     1.1.  Background
     1.2.  Protocol Overview
     1.3.  Document History
   2.  Key Words
   3.  Assigned Numbers
   4.  TSIG RR Format
     4.1.  TSIG RR Type
     4.2.  TSIG Record Format
     4.3.  MAC Computation
       4.3.1.  Request MAC
       4.3.2.  DNS Message
       4.3.3.  TSIG Variables
   5.  Protocol Details
     5.1.  Generation of TSIG on Requests
     5.2.  Server Processing of Request
       5.2.1.  Key Check and Error Handling
       5.2.2.  MAC Check and Error Handling
       5.2.3.  Time Check and Error Handling
       5.2.4.  Truncation Check and Error Handling
     5.3.  Generation of TSIG on Answers
       5.3.1.  TSIG on TCP Connections
       5.3.2.  Generation of TSIG on Error Returns
     5.4.  Client Processing of Answer
       5.4.1.  Key Error Handling
       5.4.2.  MAC Error Handling
       5.4.3.  Time Error Handling
       5.4.4.  Truncation Error Handling
     5.5.  Special Considerations for Forwarding Servers
   6.  Algorithms and Identifiers
   7.  TSIG Truncation Policy
   8.  Shared Secrets
   9.  IANA Considerations
   10. Security Considerations
     10.1.  Issue Fixed in This Document
     10.2.  Why Not DNSSEC?
   11. References
     11.1.  Normative References
     11.2.  Informative References
   Acknowledgements
   Authors' Addresses

1.  Introduction

1.1.  Background

   The Domain Name System (DNS) ([RFC1034] [RFC1035]) is a replicated