Network Working Group W. Hardaker Internet-Draft USC/ISI Updates: 4034, 5155 (if approved) W. Kumari Intended status: Standards Track Google Expires: 22 November 2025 21 May 2025 Deprecating the use of SHA-1 in DNSSEC signature algorithms draft-ietf-dnsop-must-not-sha1-08 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 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 22 November 2025. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. Hardaker & Kumari Expires 22 November 2025 [Page 1] Internet-Draft MUST NOT DNSSEC with SHA-1 May 2025 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 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. 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 . . . . . . . . . . . . . . . . . . . . . 3 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 . . . . . . . . . . . . . . . . . . . . . . . 5 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 as a cryptographic hash algorithm in RRSIG and Delegation Signer (DS) records, for example. 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. Hardaker & Kumari Expires 22 November 2025 [Page 2] Internet-Draft MUST NOT DNSSEC with SHA-1 May 2025 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. 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.] Hardaker & Kumari Expires 22 November 2025 [Page 3] Internet-Draft MUST NOT DNSSEC with SHA-1 May 2025 IANA is requested to set the "Use for DNSSEC Delegation" field of the "Digest Algorithms" registry [DS-IANA] [draft-ietf-dnsop-algorithm-update] 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] [draft-ietf-dnsop-algorithm-update] 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., . [draft-ietf-dnsop-algorithm-update] W., K., "Algorithm Implementation Requirements and Usage Guidance for DNSSEC", n.d., . [DS-IANA] IANA, "Delegation Signer (DS) Resource Record (RR) Type Digest Algorithms", n.d., . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . [RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1 (SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001, . [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, . Hardaker & Kumari Expires 22 November 2025 [Page 4] Internet-Draft MUST NOT DNSSEC with SHA-1 May 2025 [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9364] Hoffman, P., "DNS Security Extensions (DNSSEC)", BCP 237, RFC 9364, DOI 10.17487/RFC9364, February 2023, . [RFC9499] Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219, RFC 9499, DOI 10.17487/RFC9499, March 2024, . 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. 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 Authors' Addresses Wes Hardaker USC/ISI Hardaker & Kumari Expires 22 November 2025 [Page 5] Internet-Draft MUST NOT DNSSEC with SHA-1 May 2025 Email: ietf@hardakers.net Warren Kumari Google Email: warren@kumari.net Hardaker & Kumari Expires 22 November 2025 [Page 6]