| Internet-Draft | MUST NOT DNSSEC with SHA-1 | October 2024 |
| Hardaker & Kumari | Expires 6 April 2025 | [Page] |
This document retires the use of SHA-1 within DNSSEC.¶
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Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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The security of the SHA-1 algorithm [RFC3174] has been slowly diminishing over time as various forms of attacks have weakened its cryptographic underpinning. DNSSEC [RFC4033] [RFC4034] [RFC4035] originally made extensive use of SHA-1 as a cryptographic verification algorithm in RRSIG and Delegation Signer (DS) records, for example. Since then, multiple other signing algorithms with stronger cryptographic strength are now widely available for DS records (such as SHA-256 [RFC4509], SHA-384 ([RFC6605])) and for DNSKEY and RRSIG records (such as RSASHA256 ([RFC5702]), RSASHA512 ([RFC5702]), ECDSAP256SHA256 [RFC6605], ECDSAP384SHA384 [RFC6605], ED25519 [RFC8080], and ED448 [RFC8080]). Further, support for validating SHA-1 based signatures has been removed from some systems. As a result, SHA-1 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.¶
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.¶
The RSASHA1 [RFC4034] and RSASHA1-NSEC3-SHA1 [RFC5155] algorithms MUST NOT be used when creating DNSKEY and RRSIG records.¶
Validating resolvers 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. Validating resolvers MAY treat RRSIG records created from DNSKEY records using these algorithms as an unsupported algorithm.¶
This document reduces the risk that a zone cannot be validated due to lack of SHA-1 support in a validator, by guiding signers to choose a more interoperable signing algorithm.¶
Zone owners currently making use of SHA-1 based algorithms should immediately switch to algorithms with stronger cryptographic strengths, such as those listed in the introduction.¶
IANA is requested to set the "Use for DNSSEC Delegation" field of the "Digest Algorithms" registry [DS-IANA] 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] to MUST NOT for the RSASHA1 (5) and RSASHA1-NSEC3-SHA1 (7) algorithms.¶
All other columns should remain as currently specified.¶
The authors appreciate the comments and suggestions from the following IETF participants in helping produce this document: Mark Andrews, Peter Dickson, Peter Thomassen, Paul Wouters and the many members of the DNSOP working group that discussed this draft.¶
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>¶
While this document is under development, it can be viewed, tracked, fill here:¶
https://github.com/hardaker/draft-hardaker-dnsop-must-not-sha1¶