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Versions: (draft-hoffman-dnssec)  00 01 02 03      Best Current Practice
Network Working Group                                         P. Hoffman
Internet-Draft                                                     ICANN
Intended status: Best Current Practice                    11 August 2022
Expires: 12 February 2023

                    DNS Security Extensions (DNSSEC)


   This document describes the DNS security extensions (commonly called
   "DNSSEC") that are specified RFCs 4033, 4034, 4035, and a handful of
   others.  One purpose is to introduce all of the RFCs in one place so
   that the reader can understand the many aspects of DNSSEC.  This
   document does not update any of those RFCs.  Another purpose is to
   move DNSSEC to Best Current Practice status.

   This document is currently maintained at
   https://github.com/paulehoffman/draft-hoffman-dnssec.  Issues and
   pull requests are welcomed.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 12 February 2023.

Copyright Notice

   Copyright (c) 2022 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

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   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  DNSSEC as a Best Current Practice . . . . . . . . . . . .   2
     1.2.  Implementing DNSSEC . . . . . . . . . . . . . . . . . . .   3
   2.  DNSSEC Core Documents . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Addition to the DNSSEC Core . . . . . . . . . . . . . . .   4
   3.  Additional Cryptographic Algorithms and DNSSEC  . . . . . . .   4
   4.  Extensions to DNSSEC  . . . . . . . . . . . . . . . . . . . .   5
   5.  Additional Documents of Interest  . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  10
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The core specification for what we know as DNSSEC (the combination of
   [RFC4033], [RFC4034], and [RFC4035]) describes a set of protocols
   that provide origin authentication to data in the DNS.  [RFC6840]
   updates and extends those core RFCs, but does not fundamentally
   change the way that DNSSEC works.

   This document lists many (but not all) of the RFCs that should be
   considered by someone creating an implementation of, or someone
   deploying, modern DNSSEC.  It uses terminology from those documents
   without defining that terminology.  It also points to the relevant
   IANA registries that relate to DNSSEC.  It does not, however, point
   to standards that rely on zones needing to be signed by DNSSEC.

1.1.  DNSSEC as a Best Current Practice

   The DNSSEC set of protocols is widely considered the best current
   practice for adding origin authentication of data in the DNS.  To
   date, no standards-track RFCs offer any other method for such origin
   authentication of data in the DNS.

   Some observers note that, more than 15 years after the DNSSEC
   specification was published, it is still not widely deployed.  Recent
   estimates are that fewer than 10% of the domain names used for web

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   sites are signed, and only around a third of queries to recursive
   resolvers are validated.  However, this low level of implementation
   does not affect whether DNSSEC is a best current practice; it just
   indicates that the value of deploying DNSSEC is often considered
   lower than the cost.  Nonetheless, the significant deployment of
   DNSSEC beneath some top-level domains (TLDs), and the near-universal
   deployment of DNSSEC for the TLDs in the DNS root zone, demonstrate
   that DNSSEC is suitable for implementation by both ordinary and
   highly sophisticated domain owners.

1.2.  Implementing DNSSEC

   Developers of validating resolvers and authoritative servers, as well
   as operators of operators of validating resolvers and authoritative
   servers, need to know the parts of the DNSSEC protocol that would
   affect them.  They should read the DNSSEC core documents, and
   probably at least be familiar with the extensions.  Developers will
   probably need to be very familiar with the algorithm documents as

   As a side note, some of the DNSSEC-related RFCs have significant
   errata, so reading the RFCs should also include looking for the
   related errata.

2.  DNSSEC Core Documents

   What we today call "DNSSEC" is formally version 3 of the DNSSEC
   specification.  However, earlier versions of DNSSEC were thinly
   deployed and significantly less visible than the current DNSSEC
   specification.  Throughout this document, "DNSSEC" means version 3 of
   the protocol initially defined in [RFC4033], [RFC4034], and

   The three initial core documents generally cover different topics:

   *  [RFC4033] is an overview of DNSSEC, including how it might change
      the resolution of DNS queries.

   *  [RFC4034] specifies the DNS resource records used in DNSSEC.  It
      obsoletes many RFCs for earlier versions of DNSSEC.

   *  [RFC4035] covers the modifications to the DNS protocol incurred by
      DNSSEC.  These include signing zones, serving signed zones,
      resolving in light of DNSSEC, and authenticating DNSSEC-signed

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   At the time this set of core documents was published, someone could
   create a DNSSEC implementation of signing software, of an DNSSEC-
   aware authoritative server, and/or a DNSSEC-aware recursive resolver
   from the three core documents, the many documents that update them,
   plus a few older RFCs specifying the cryptography used.  Those two
   older documents are:

   *  [RFC2536] defines how to use the DSA signature algorithm (although
      refers to other documents for the details).  DSA was thinly
      implemented and can safely be ignored by DNSSEC implementations

   *  [RFC3110] defines how to use the RSA signature algorithm (although
      refers to other documents for the details).  RSA is still the most
      popular signing algorithm for DNSSEC.

   It is important to note that later RFCs update the core documents.
   As just one example, [RFC9077] changes how TTL values are calculated
   in DNSSEC processing.

2.1.  Addition to the DNSSEC Core

   As with any major protocol, developers and operators discovered
   issues with the original core documents over the years.  [RFC6840] is
   an omnibus update to the original core documents and thus itself has
   become a core document.  In addition to covering new requirements
   from new DNSSEC RFCs, it describes many important security and
   interoperability issues that arose during the deployment of the
   initial specifications, particularly after the DNS root was signed in
   2010.  It also lists some errors in the examples of the core

   [RFC6840] brings a few additions into the core of DNSSEC.  It makes
   NSEC3 [RFC5155] as much a part of DNSSEC as NSEC is.  It also makes
   the SHA-2 hash function defined in [RFC4509] and [RFC5702] part of
   the core as well.

3.  Additional Cryptographic Algorithms and DNSSEC

   Cryptography improves over time, and new algorithms get adopted by
   various Internet protocols.  Two new signing algorithms have been
   adopted by the DNSSEC community: ECDSA [RFC6605] and EdDSA [RFC8080].
   The GOST signing algorithm [RFC5933] was also adopted, but has seen
   very limited use, likely because it is a national algorithm specific
   to a very small number of countries.

   Implementation developers who want to know which algorithms to
   implement in DNSSEC software should refer to [RFC8624].  Note that
   this specification is only about what algorithms should and should

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   not be included in implementations: it is not advice for which
   algorithms that zone operators should and should not sign with, nor
   which algorithms recursive resolver operators should or should not

4.  Extensions to DNSSEC

   The DNSSEC community has extended the DNSSEC core and the
   cryptographic algorithms both in terms of describing good operational
   practices and in new protocols.  Some of the RFCs that describe these
   extensions include:

   *  [RFC5011] describes a method to help resolvers update their DNSSEC
      trust anchors in an automated fashion.  This method was used in
      2018 to update the DNS root trust anchor.

   *  [RFC6781] is a compendium of operational practices that may not be
      obvious from reading just the core specifications.

   *  [RFC7344] describes using the CDS and CDNSKEY resource records to
      help automate the maintenance of DS records in the parents of
      signed zones.

   *  [RFC8078] extends [RFC7344] by showing how to do initial setup of
      trusted relationships between signed parent and child zones.

   *  [RFC8198] describes how a validating resolver can emit fewer
      queries in signed zones that use NSEC and NSEC3 for negative

   *  [RFC9077] updates [RFC8198] with respect to the time-to-live (TTL)
      fields in signed records.

5.  Additional Documents of Interest

   The documents listed above constitute the core of DNSSEC, the
   additional cryptographic algorithms, and the major extensions to
   DNSSEC.  This section lists some additional documents that someone
   interested in implementing or operating DNSSEC might find of value.

   *  [RFC4470] "describes how to construct DNSSEC NSEC resource records
      that cover a smaller range of names than called for by [RFC4034]".

   *  [RFC6975] "specifies a way for validating end-system resolvers to
      signal to a server which digital signature and hash algorithms
      they support".

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   *  [RFC7129] "provides additional background commentary and some
      context for the NSEC and NSEC3 mechanisms used by DNSSEC to
      provide authenticated denial-of-existence responses".  This
      background is particularly important for understanding NSEC and
      NSEC3 usage.

   *  [RFC7583] "describes the issues surrounding the timing of events
      in the rolling of a key in a DNSSEC-secured zone".

   *  [RFC7646] "defines Negative Trust Anchors (NTAs), which can be
      used to mitigate DNSSEC validation failures by disabling DNSSEC
      validation at specified domains".

   *  [RFC7958] "describes the format and publication mechanisms IANA
      has used to distribute the DNSSEC trust anchors".

   *  [RFC8027] "describes problems that a Validating DNS resolver,
      stub-resolver, or application might run into within a non-
      compliant infrastructure".

   *  [RFC8145] "specifies two different ways for validating resolvers
      to signal to a server which keys are referenced in their chain of

   *  [RFC8499] is a list of terminology used when talking about the
      DNS; sections 10 and 11 cover DNSSEC.

   *  [RFC8509] "specifies a mechanism that will allow an end user and
      third parties to determine the trusted key state for the root key
      of the resolvers that handle that user's DNS queries".

   *  [RFC8901] "presents deployment models that accommodate this
      scenario [when each DNS provider independently signs zone data
      with their own keys] and describes these key-management

   *  [RFC9276] "provides guidance on setting NSEC3 parameters based on
      recent operational deployment experience".

   There will certainly be other RFCs related to DNSSEC that are
   published after this one.

6.  IANA Considerations

   IANA already has three registries that relate to DNSSEC:

   *  DNSSEC algorithm numbers (https://www.iana.org/assignments/dns-

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   *  DNSSEC NSEC3 parameters (https://www.iana.org/assignments/dnssec-

   *  DNSSEC DS RRtype digest algorithms

   The rules for the DNSSEC algorithm registry were set in the core RFCs
   and updated by [RFC6014], [RFC6725], and [RFC9157].

   This document does not update or create any registries.

7.  Security Considerations

   All of the security considerations from all of the RFCs referenced in
   this document apply here.

8.  References

8.1.  Normative References

   [RFC3110]  Eastlake 3rd, D., "RSA/SHA-1 SIGs and RSA KEYs in the
              Domain Name System (DNS)", RFC 3110, DOI 10.17487/RFC3110,
              May 2001, <https://www.rfc-editor.org/info/rfc3110>.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",
              RFC 4033, DOI 10.17487/RFC4033, March 2005,

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,

   [RFC4509]  Hardaker, W., "Use of SHA-256 in DNSSEC Delegation Signer
              (DS) Resource Records (RRs)", RFC 4509,
              DOI 10.17487/RFC4509, May 2006,

   [RFC5155]  Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
              Security (DNSSEC) Hashed Authenticated Denial of
              Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,

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   [RFC5702]  Jansen, J., "Use of SHA-2 Algorithms with RSA in DNSKEY
              and RRSIG Resource Records for DNSSEC", RFC 5702,
              DOI 10.17487/RFC5702, October 2009,

   [RFC6840]  Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and
              Implementation Notes for DNS Security (DNSSEC)", RFC 6840,
              DOI 10.17487/RFC6840, February 2013,

8.2.  Informative References

   [RFC2536]  Eastlake 3rd, D., "DSA KEYs and SIGs in the Domain Name
              System (DNS)", RFC 2536, DOI 10.17487/RFC2536, March 1999,

   [RFC4470]  Weiler, S. and J. Ihren, "Minimally Covering NSEC Records
              and DNSSEC On-line Signing", RFC 4470,
              DOI 10.17487/RFC4470, April 2006,

   [RFC5011]  StJohns, M., "Automated Updates of DNS Security (DNSSEC)
              Trust Anchors", STD 74, RFC 5011, DOI 10.17487/RFC5011,
              September 2007, <https://www.rfc-editor.org/info/rfc5011>.

   [RFC5933]  Dolmatov, V., Ed., Chuprina, A., and I. Ustinov, "Use of
              GOST Signature Algorithms in DNSKEY and RRSIG Resource
              Records for DNSSEC", RFC 5933, DOI 10.17487/RFC5933, July
              2010, <https://www.rfc-editor.org/info/rfc5933>.

   [RFC6014]  Hoffman, P., "Cryptographic Algorithm Identifier
              Allocation for DNSSEC", RFC 6014, DOI 10.17487/RFC6014,
              November 2010, <https://www.rfc-editor.org/info/rfc6014>.

   [RFC6605]  Hoffman, P. and W.C.A. Wijngaards, "Elliptic Curve Digital
              Signature Algorithm (DSA) for DNSSEC", RFC 6605,
              DOI 10.17487/RFC6605, April 2012,

   [RFC6725]  Rose, S., "DNS Security (DNSSEC) DNSKEY Algorithm IANA
              Registry Updates", RFC 6725, DOI 10.17487/RFC6725, August
              2012, <https://www.rfc-editor.org/info/rfc6725>.

   [RFC6781]  Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC
              Operational Practices, Version 2", RFC 6781,
              DOI 10.17487/RFC6781, December 2012,

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   [RFC6975]  Crocker, S. and S. Rose, "Signaling Cryptographic
              Algorithm Understanding in DNS Security Extensions
              (DNSSEC)", RFC 6975, DOI 10.17487/RFC6975, July 2013,

   [RFC7129]  Gieben, R. and W. Mekking, "Authenticated Denial of
              Existence in the DNS", RFC 7129, DOI 10.17487/RFC7129,
              February 2014, <https://www.rfc-editor.org/info/rfc7129>.

   [RFC7344]  Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
              DNSSEC Delegation Trust Maintenance", RFC 7344,
              DOI 10.17487/RFC7344, September 2014,

   [RFC7583]  Morris, S., Ihren, J., Dickinson, J., and W. Mekking,
              "DNSSEC Key Rollover Timing Considerations", RFC 7583,
              DOI 10.17487/RFC7583, October 2015,

   [RFC7646]  Ebersman, P., Kumari, W., Griffiths, C., Livingood, J.,
              and R. Weber, "Definition and Use of DNSSEC Negative Trust
              Anchors", RFC 7646, DOI 10.17487/RFC7646, September 2015,

   [RFC7958]  Abley, J., Schlyter, J., Bailey, G., and P. Hoffman,
              "DNSSEC Trust Anchor Publication for the Root Zone",
              RFC 7958, DOI 10.17487/RFC7958, August 2016,

   [RFC8027]  Hardaker, W., Gudmundsson, O., and S. Krishnaswamy,
              "DNSSEC Roadblock Avoidance", BCP 207, RFC 8027,
              DOI 10.17487/RFC8027, November 2016,

   [RFC8078]  Gudmundsson, O. and P. Wouters, "Managing DS Records from
              the Parent via CDS/CDNSKEY", RFC 8078,
              DOI 10.17487/RFC8078, March 2017,

   [RFC8080]  Sury, O. and R. Edmonds, "Edwards-Curve Digital Security
              Algorithm (EdDSA) for DNSSEC", RFC 8080,
              DOI 10.17487/RFC8080, February 2017,

   [RFC8145]  Wessels, D., Kumari, W., and P. Hoffman, "Signaling Trust
              Anchor Knowledge in DNS Security Extensions (DNSSEC)",
              RFC 8145, DOI 10.17487/RFC8145, April 2017,

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   [RFC8198]  Fujiwara, K., Kato, A., and W. Kumari, "Aggressive Use of
              DNSSEC-Validated Cache", RFC 8198, DOI 10.17487/RFC8198,
              July 2017, <https://www.rfc-editor.org/info/rfc8198>.

   [RFC8499]  Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
              January 2019, <https://www.rfc-editor.org/info/rfc8499>.

   [RFC8509]  Huston, G., Damas, J., and W. Kumari, "A Root Key Trust
              Anchor Sentinel for DNSSEC", RFC 8509,
              DOI 10.17487/RFC8509, December 2018,

   [RFC8624]  Wouters, P. and O. Sury, "Algorithm Implementation
              Requirements and Usage Guidance for DNSSEC", RFC 8624,
              DOI 10.17487/RFC8624, June 2019,

   [RFC8901]  Huque, S., Aras, P., Dickinson, J., Vcelak, J., and D.
              Blacka, "Multi-Signer DNSSEC Models", RFC 8901,
              DOI 10.17487/RFC8901, September 2020,

   [RFC9077]  van Dijk, P., "NSEC and NSEC3: TTLs and Aggressive Use",
              RFC 9077, DOI 10.17487/RFC9077, July 2021,

   [RFC9157]  Hoffman, P., "Revised IANA Considerations for DNSSEC",
              RFC 9157, DOI 10.17487/RFC9157, December 2021,

   [RFC9276]  Hardaker, W. and V. Dukhovni, "Guidance for NSEC3
              Parameter Settings", BCP 236, RFC 9276,
              DOI 10.17487/RFC9276, August 2022,

Appendix A.  Acknowledgements

   The DNS world owes a depth of gratitude to the authors and other
   contributors to the core DNSSEC documents, and to the notable DNSSEC

   In addition, the following people made significant contributions to
   early versions of this document: Ben Schwartz and Duane Wessels.

Author's Address

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   Paul Hoffman
   Email: paul.hoffman@icann.org

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