]> USC/ISI

ietf@hardakers.net

Google

warren@kumari.net

This document retires the use of SHA-1 within DNSSEC.

Introduction The security of the SHA-1 algorithm has been slowly diminishing over time as various forms of attacks have weakened its cryptographic underpinning. DNSSEC originally made extensive use of SHA-1 as a cryptographic verification algorithm in RRSIG and Delegation Signer (DS) records, for example.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 , SHA-384 ()) and for DNSKEY and RRSIG records (such as RSASHA256 (), RSASHA512 (), ECDSAP256SHA256 , ECDSAP384SHA384 , ED25519 , and ED448 ), the use of SHA-1 is no longer needed. This document retires the use of SHA-1 within DNSSEC.

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 when, and only when, they appear in all capitals, as shown here.

Deprecating SHA-1 algorithms in DNSSEC The SHA-1 algorithm MUST NOT be used when creating DS records. Validating resolvers MUST treat 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 , DSA-NSEC3-SHA1 , and RSASHA1-NSEC3-SHA1 algorithms MUST NOT be used when creating DNSKEY and RRSIG records. Validating resolvers MUST treat RRSIG records created from DNSKEY records using these algorithms as insecure. If no other RRSIG records of accepted cryptographic algorithms are available, the validating resolver MUST consider the associated resource records as Bogus.

Security Considerations This document increases the security of the DNSSEC ecosystem by deprecating algorithms that make use of older algorithms with SHA-1 derived uses.

Operational Considerations Zone owners currently making use of SHA-1 based algorithms should immediate switch to algorithms with stronger cryptographic strengths, such as those listed in the introduction. DNS registries should prohibit their clients to upload and publish SHA-1 based DS records.

IANA Considerations IANA is requested to set the "DNSSEC Validation" of the "Digest Algorithms" registry for SHA-1 (1) to MUST NOT. IANA is requested to set the "Recommended for DNSSEC Validation" column of the DNS Security Algorithm Numbers registry to MUST NOT:

• RSASHA1 (5)
• RSASHA1-NSEC3-SHA1 (7)

References Normative References In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. The purpose of this document is to make the SHA-1 (Secure Hash Algorithm 1) hash algorithm conveniently available to the Internet community. This memo provides information for the Internet community. The SIEVE mail filtering language "spamtest" and "virustest" extensions permit users to use simple, portable commands for spam and virus tests on email messages. Each extension provides a new test using matches against numeric 'scores'. It is the responsibility of the underlying SIEVE implementation to do the actual checks that result in values returned by the tests. [PROPOSED STANDARD] The Domain Name System Security Extensions (DNSSEC) add data origin authentication and data integrity to the Domain Name System. This document introduces these extensions and describes their capabilities and limitations. This document also discusses the services that the DNS security extensions do and do not provide. Last, this document describes the interrelationships between the documents that collectively describe DNSSEC. [STANDARDS-TRACK] This document is part of a family of documents that describe the DNS Security Extensions (DNSSEC). The DNS Security Extensions are a collection of resource records and protocol modifications that provide source authentication for the DNS. This document defines the public key (DNSKEY), delegation signer (DS), resource record digital signature (RRSIG), and authenticated denial of existence (NSEC) resource records. The purpose and format of each resource record is described in detail, and an example of each resource record is given. This document obsoletes RFC 2535 and incorporates changes from all updates to RFC 2535. [STANDARDS-TRACK] This document is part of a family of documents that describe the DNS Security Extensions (DNSSEC). The DNS Security Extensions are a collection of new resource records and protocol modifications that add data origin authentication and data integrity to the DNS. This document describes the DNSSEC protocol modifications. This document defines the concept of a signed zone, along with the requirements for serving and resolving by using DNSSEC. These techniques allow a security-aware resolver to authenticate both DNS resource records and authoritative DNS error indications. This document obsoletes RFC 2535 and incorporates changes from all updates to RFC 2535. [STANDARDS-TRACK] This document specifies how to use the SHA-256 digest type in DNS Delegation Signer (DS) Resource Records (RRs). DS records, when stored in a parent zone, point to DNSKEYs in a child zone. [STANDARDS-TRACK] The Domain Name System Security (DNSSEC) Extensions introduced the NSEC resource record (RR) for authenticated denial of existence. This document introduces an alternative resource record, NSEC3, which similarly provides authenticated denial of existence. However, it also provides measures against zone enumeration and permits gradual expansion of delegation-centric zones. [STANDARDS-TRACK] This document describes how to produce RSA/SHA-256 and RSA/SHA-512 DNSKEY and RRSIG resource records for use in the Domain Name System Security Extensions (RFC 4033, RFC 4034, and RFC 4035). [STANDARDS TRACK] This document describes how to specify Elliptic Curve Digital Signature Algorithm (DSA) keys and signatures in DNS Security (DNSSEC). It lists curves of different sizes and uses the SHA-2 family of hashes for signatures. [STANDARDS-TRACK] This document describes how to specify Edwards-curve Digital Security Algorithm (EdDSA) keys and signatures in DNS Security (DNSSEC). It uses EdDSA with the choice of two curves: Ed25519 and Ed448. n.d. n.d. Informative References The Domain Name System (DNS) is defined in literally dozens of different RFCs. The terminology used by implementers and developers of DNS protocols, and by operators of DNS systems, has sometimes changed in the decades since the DNS was first defined. This document gives current definitions for many of the terms used in the DNS in a single document. This document obsoletes RFC 7719 and updates RFC 2308. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.

Acknowledgments TBD

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]

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