Clarifications and Implementation Notes for DNS Security (DNSSEC)
RFC 6840

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Internet Engineering Task Force (IETF)                    S. Weiler, Ed.
Request for Comments: 6840                                  SPARTA, Inc.
Updates: 4033, 4034, 4035, 5155                           D. Blacka, Ed.
Category: Standards Track                                 Verisign, Inc.
ISSN: 2070-1721                                            February 2013

   Clarifications and Implementation Notes for DNS Security (DNSSEC)

Abstract

   This document is a collection of technical clarifications to the DNS
   Security (DNSSEC) document set.  It is meant to serve as a resource
   to implementors as well as a collection of DNSSEC errata that existed
   at the time of writing.

   This document updates the core DNSSEC documents (RFC 4033, RFC 4034,
   and RFC 4035) as well as the NSEC3 specification (RFC 5155).  It also
   defines NSEC3 and SHA-2 (RFC 4509 and RFC 5702) as core parts of the
   DNSSEC specification.

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 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6840.

Weiler & Blacka              Standards Track                    [Page 1]
RFC 6840               DNSSEC Implementation Notes         February 2013

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.

   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
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Weiler & Blacka              Standards Track                    [Page 2]
RFC 6840               DNSSEC Implementation Notes         February 2013

Table of Contents

   1. Introduction and Terminology ....................................4
      1.1. Structure of This Document .................................4
      1.2. Terminology ................................................4
   2. Important Additions to DNSSEC ...................................4
      2.1. NSEC3 Support ..............................................4
      2.2. SHA-2 Support ..............................................5
   3. Scaling Concerns ................................................5
      3.1. Implement a BAD Cache ......................................5
   4. Security Concerns ...............................................5
      4.1. Clarifications on Nonexistence Proofs ......................5
      4.2. Validating Responses to an ANY Query .......................6
      4.3. Check for CNAME ............................................6
      4.4. Insecure Delegation Proofs .................................7
   5. Interoperability Concerns .......................................7
      5.1. Errors in Canonical Form Type Code List ....................7
      5.2. Unknown DS Message Digest Algorithms .......................7
      5.3. Private Algorithms .........................................8
      5.4. Caution about Local Policy and Multiple RRSIGs .............9
      5.5. Key Tag Calculation ........................................9
      5.6. Setting the DO Bit on Replies ..............................9
      5.7. Setting the AD Bit on Queries .............................10
      5.8. Setting the AD Bit on Replies .............................10
      5.9. Always Set the CD Bit on Queries ..........................10
      5.10. Nested Trust Anchors .....................................11