wdiff rfc9905.original rfc9905.txt

Network Working Group

Internet Engineering Task Force (IETF) W. Hardaker
Internet-Draft
Request for Comments: 9905 USC/ISI
Updates: 4034, 5155 (if approved) W. Kumari
Intended status:
Category: Standards Track Google
Expires: 14 March 2026 10 September
ISSN: 2070-1721 October 2025

Deprecating the use Use of SHA-1 in DNSSEC signature algorithms
draft-ietf-dnsop-must-not-sha1-10 Signature Algorithms

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 RFCs 4034 and RFC5155 5155 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 an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
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Internet-Drafts are draft documents valid the IETF community. It has
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This Internet-Draft will expire on 14 March 2026.
https://www.rfc-editor.org/info/rfc9905.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3 Notation
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] (originally defined in [RFC3110]) made extensive use of
SHA-1, for
example example, as a cryptographic hash algorithm in RRSIG Resource
Record Signature (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) RRSIG and DNS
Public Key
(RRSIG) (DNSKEY) 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 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.

1.1. Requirements notation 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. Operators of 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 ([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. Operators of validating resolvers MUST treat DNSSEC
signing algorithms RSASHA1 and RSASHA1-NSEC3-SHA1 as unsupported,
rendering responses insecure if they cannot be validated by other
supported signing algorithms.

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 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 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.

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 has set the "Use for DNSSEC Delegation" field column of the "Digest
Algorithms" registry [DS-IANA] [I-D.ietf-dnsop-rfc8624-bis] [RFC9904] to MUST NOT for SHA-1 (1) to MUST NOT.
and has added this document as a reference for the entry.

IANA is requested to has set the "Use for DNSSEC Signing" column of the
DNS "DNS Security
Algorithm Numbers Numbers" registry [DNSKEY-IANA]
[I-D.ietf-dnsop-rfc8624-bis] [RFC9904] to MUST NOT for
the RSASHA1 (5) and RSASHA1-NSEC3-SHA1 (7) algorithms. algorithms and has added
this document as a reference for these entries.

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>.
<https://www.iana.org/assignments/dns-sec-alg-numbers>.

[DS-IANA] IANA, "Delegation "DNSSEC 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-13,
4 June 2025, <https://datatracker.ietf.org/doc/html/draft-
ietf-dnsop-rfc8624-bis-13>.

[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>.
<https://www.rfc-editor.org/info/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>. <https://www.rfc-editor.org/info/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>.
<https://www.rfc-editor.org/info/rfc3174>.

[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>.
<https://www.rfc-editor.org/info/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>.
<https://www.rfc-editor.org/info/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>. <https://www.rfc-editor.org/info/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>.
<https://www.rfc-editor.org/info/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.
<https://www.rfc-editor.org/info/rfc9499>.

[RFC9904] Hardaker, W. and W. Kumari, "DNSSEC Cryptographic
Algorithm Recommendation Update Process", RFC 9904,
DOI 10.17487/RFC9904, October 2025,
<https://www.rfc-editor.org/info/rfc9904>.

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 S. Moonesamy, Yoav Nir,
Florian Obser, Peter Thomassen, Stefan Ubbink, Paul Wouters, Tim
Wicinski, and the many members of the DNSOP working group 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.

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> specification.

Authors' Addresses

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

Warren Kumari
Google
Email: warren@kumari.net