Deprecating the use of SHA-1 in DNSSEC signature algorithms
draft-ietf-dnsop-must-not-sha1-09

Network Working Group                                        W. Hardaker
Internet-Draft                                                   USC/ISI
Updates: 4034, 5155 (if approved)                              W. Kumari
Intended status: Standards Track                                  Google
Expires: 5 December 2025                                     3 June 2025

      Deprecating the use of SHA-1 in DNSSEC signature algorithms
                   draft-ietf-dnsop-must-not-sha1-09

Abstract

   This document deprecates the use of the RSASHA1 and
   RSASHA1-NSEC3-SHA1 algorithms for the creation of DNS Public Key
   (DNSKEY) and Resource Record Signature (RRSIG) records.

   It updates RFC4034 and RFC5155 as it deprecates the use of these
   algorithms.

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
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   This Internet-Draft will expire on 5 December 2025.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  Deprecating SHA-1 from DNSSEC Signatures and Delegation
           RRs . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  Operational Considerations  . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .   5
   Appendix B.  Current algorithm usage levels . . . . . . . . . . .   5
   Appendix C.  Github Version of this document  . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The security of the protection provided by the SHA-1 algorithm
   [RFC3174] has been slowly diminishing over time as various forms of
   attacks have weakened its cryptographic underpinning.  DNSSEC
   [RFC9364] originally [RFC3110] made extensive use of SHA-1, for
   example as a cryptographic hash algorithm in RRSIG and Delegation
   Signer (DS) records.  Since then, multiple other algorithms with
   stronger cryptographic strength have become widely available for DS
   records and for Resource Record Signature (DNSKEY) and DNS Public Key
   (RRSIG) records [RFC4034].  Operators are encouraged to consider
   switching to one of the recommended algorithms listed in the
   [DNSKEY-IANA] and [DS-IANA] tables, respectively.  Further, support
   for validating SHA-1 based signatures has been removed from some
   systems.  As a result, SHA-1 as part of a signature algorithm is no
   longer fully interoperable in the context of DNSSEC.  As adequate
   alternatives exist, the use of SHA-1 is no longer advisable.

   This document thus further deprecates the use of RSASHA1 and
   RSASHA1-NSEC3-SHA1 for DNS Security Algorithms.

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1.1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Deprecating SHA-1 from DNSSEC Signatures and Delegation RRs

   The RSASHA1 [RFC4034] and RSASHA1-NSEC3-SHA1 [RFC5155] algorithms
   MUST NOT be used when creating DS records.  Validating resolvers MUST
   treat RSASHA1 and RSASHA1-NSEC3-SHA1 DS records as insecure.  If no
   other DS records of accepted cryptographic algorithms are available,
   the DNS records below the delegation point MUST be treated as
   insecure.

   The RSASHA1 [RFC4034] and RSASHA1-NSEC3-SHA1 [RFC5155] algorithms
   MUST NOT be used when creating DNSKEY and RRSIG records.  Validating
   resolver implementations ([RFC9499] section 10) MUST continue to
   support validation using these algorithms as they are diminishing in
   use but still actively in use for some domains as of this
   publication.  Because of RSASHA1 and RSASHA1-NSEC3-SHA1's non-zero
   use, deployed validating resolvers MAY be configured to continue to
   validate RRSIG records that use these algorithms.  Validating
   resolvers deployed in more security strict environments MAY treat
   these RRSIG records as an unsupported algorithm.

3.  Security Considerations

   This document deprecates the use of RSASHA1 and RSASHA1-NSEC3-SHA1
   for DNSSEC Delegation and DNSSEC signing since these algorithms are
   no longer considered to be secure.

4.  Operational Considerations

   Zone owners currently making use of SHA-1 based algorithms should
   immediately roll to algorithms with stronger cryptographic
   algorithms, such as the recommended algorithms in the [DNSKEY-IANA]
   and [DS-IANA] tables.

   Operators should take care when deploying software packages and
   operating systems that may have already removed support for the SHA-1
   algorithm.  In these situations software may need to be manually
   built and deployed by an operator to continue supporting the required
   levels indicated by the "Use for DNSSEC Validation" and "Implement
   for DNSSEC Validation" columns, which this document is not changing.

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5.  IANA Considerations

   [Note to IANA, to be removed by the RFC Editor: the registry fields
   listed above will be created by draft-ietf-dnsop-rfc8624-bis.]

   IANA is requested to set the "Use for DNSSEC Delegation" field of the
   "Digest Algorithms" registry [DS-IANA] [I-D.ietf-dnsop-rfc8624-bis]
   for SHA-1 (1) to MUST NOT.

   IANA is requested to set the "Use for DNSSEC Signing" column of the
   DNS Security Algorithm Numbers registry [DNSKEY-IANA]
   [I-D.ietf-dnsop-rfc8624-bis] to MUST NOT for the RSASHA1 (5) and
   RSASHA1-NSEC3-SHA1 (7) algorithms.

   All other columns should remain as currently specified.

6.  Normative References

   [DNSKEY-IANA]
              IANA, "Domain Name System Security (DNSSEC) Algorithm
              Numbers", n.d., <https://www.iana.org/assignments/dns-sec-
              alg-numbers/dns-sec-alg-numbers.xhtml>.

   [DS-IANA]  IANA, "Delegation Signer (DS) Resource Record (RR) Type
              Digest Algorithms", n.d.,
              <http://www.iana.org/assignments/ds-rr-types>.

   [I-D.ietf-dnsop-rfc8624-bis]
              Hardaker, W. and W. Kumari, "DNSSEC Cryptographic
              Algorithm Recommendation Update Process", Work in
              Progress, Internet-Draft, draft-ietf-dnsop-rfc8624-bis-11,
              21 May 2025, <https://datatracker.ietf.org/doc/html/draft-
              ietf-dnsop-rfc8624-bis-11>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [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/rfc/rfc3110>.

   [RFC3174]  Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1
              (SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001,
              <https://www.rfc-editor.org/rfc/rfc3174>.

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   [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,
              <https://www.rfc-editor.org/rfc/rfc4034>.

   [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,
              <https://www.rfc-editor.org/rfc/rfc5155>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [RFC9364]  Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237,
              RFC 9364, DOI 10.17487/RFC9364, February 2023,
              <https://www.rfc-editor.org/rfc/rfc9364>.

   [RFC9499]  Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219,
              RFC 9499, DOI 10.17487/RFC9499, March 2024,
              <https://www.rfc-editor.org/rfc/rfc9499>.

Appendix A.  Acknowledgments

   The authors appreciate the comments and suggestions from the
   following IETF participants in helping produce this document: Mark
   Andrews, Steve Crocker, Peter Dickson, Thomas Graf, Paul Hoffman,
   Russ Housley, Shumon Huque, Barry Leiba, S Moonesamy, Yoav Nir,
   Florian Obser, Peter Thomassen, Stefan Ubbink, Paul Wouters, Tim
   Wicinski, and the many members of the DNSOP working group that
   discussed this draft.

Appendix B.  Current algorithm usage levels

   The DNSSEC scanning project by Viktor Dukhovni and Wes Hardaker
   highlights the current deployment of various algorithms on the
   https://stats.dnssec-tools.org/ website.

   <RFC Editor: please delete this section upon publication>

Appendix C.  Github Version of this document

   While this document is under development, it can be viewed, tracked,
   fill here:

   https://github.com/hardaker/draft-hardaker-dnsop-must-not-sha1

   <RFC Editor: please delete this section upon publication>

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Authors' Addresses

   Wes Hardaker
   USC/ISI
   Email: ietf@hardakers.net

   Warren Kumari
   Google
   Email: warren@kumari.net

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