| Internet-Draft | title | February 2024 |
| Hardaker & Kumari | Expires 30 August 2024 | [Page] |
[EDITOR NOTE: This document does not change the status (MUST, MAY, RECOMMENDED, etc) of any of the algorithms listed in [RFC8624]; that is the work of future documents. Instead, this document moves the canonical list of algorithms from [RFC8624] to an IANA registry. This is done for two reasons: 1) to allow the list to be updated more easily, and, much more importantly, 2) to allow the list to be more easily referenced.]¶
The DNSSEC protocol makes use of various cryptographic algorithms to provide authentication of DNS data and proof of non-existence. To ensure interoperability between DNS resolvers and DNS authoritative servers, it is necessary to specify both a set of algorithm implementation requirements and usage guidelines to ensure that there is at least one algorithm that all implementations support. This document updates [RFC8624] by moving the canonical source of algorithm implementation requirements and usage guidance for DNSSEC from [RFC8624] to an IANA registry. Future extensions to this registry can be made under new, incremental update RFCs.¶
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 30 August 2024.¶
Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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.¶
DNS Security Extensions (DNSSEC) [RFC4034] is used to provide authentication of DNS data. The DNSSEC signing algorithms are defined by various RFCs, including [RFC4034], [RFC5155], [RFC5702], [RFC5933], [RFC6605], [RFC8080]. To ensure interoperability, a set of "mandatory-to-implement" DNSKEY algorithms are defined in [RFC8624]. To make the current status of the algorithms more easily accessible and understandable, this document moves the canonical status of the algorithms from [RFC8624] to the IANA DNSSEC algorithm registries. [ Editor: This is similar to the process used for the [TLS-ciphersuites] registry, where the canonical list of ciphersuites is in the IANA registry, and the RFCs reference the IANA registry. ]¶
This document simply moves the canonical list of algorithms from [RFC8624] to the IANA registry, and defines the registry policies for updating the registry. It does not change the status of any of the algorithms listed in [RFC8624]; this is left to future documents.¶
The recommendations of this document mostly target DNSSEC implementers, as implementations need to meet both high security expectations as well as high interoperability between various vendors and with different versions. Interoperability requires a smooth transition to more secure algorithms. This perspective may differ from that of a user who wishes to deploy and configure DNSSEC with only the safest algorithm. On the other hand, the comments and recommendations in this document are also expected to be useful for such users.¶
The field of cryptography evolves continuously. New, stronger algorithms appear, and existing algorithms may be found to be less secure then originally thought. Therefore, algorithm implementation requirements and usage guidance need to be updated from time to time in order to reflect the new reality. Cryptographic algorithm choices implemented in and required by software must be conservative to minimize the risk of algorithm compromise.¶
By the time a DNSSEC cryptographic algorithm is made mandatory-to-implement, it should already be available in most implementations. This document attempts to identify and introduce those algorithms for future mandatory-to-implement status. There is no guarantee that algorithms in use today will become mandatory to implement in the future. Published algorithms are continuously subjected to cryptographic attack and may become too weak, or even be completely broken, before this document is updated.¶
It is expected that the deprecation of an algorithm will be performed gradually. This provides time for implementations to update their implemented algorithms while remaining interoperable. Unless there are strong security reasons, an algorithm is expected to be downgraded from MUST to NOT RECOMMENDED or MAY, instead of directly from MUST to MUST NOT. Similarly, an algorithm that has not been mentioned as mandatory-to-implement is expected to be first introduced as RECOMMENDED instead of a MUST.¶
Since the effect of using an unknown DNSKEY algorithm is that the zone is treated as insecure, it is recommended that algorithms downgraded to NOT RECOMMENDED or lower not be used by authoritative nameservers and DNSSEC signers to create new DNSKEY's. This will allow for deprecated algorithms to become used less and less over time. Once an algorithm has reached a sufficiently low level of deployment, it can be marked as MUST NOT, so that recursive resolvers can remove support for validating it.¶
Validating recursive resolvers are encouraged to retain support for all algorithms not marked as MUST NOT.¶
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.¶
[RFC2119] considers the term SHOULD equivalent to RECOMMENDED, and SHOULD NOT equivalent to NOT RECOMMENDED. The authors of this document have chosen to use the terms RECOMMENDED and NOT RECOMMENDED, as this more clearly expresses the recommendations to implementers.¶
Per this document, the following "Recommended" columns have been added to the following DNSSEC algorithm tables registered with IANA:¶
| Table | Column added |
|---|---|
| Domain Security Algorithm Numbers | Recommended for DNSSSEC Signing |
| Domain sSecurity Algorithm Numbers | Recommended for DNSSSEC Validation |
| Digest Algorithms |
Adding a new entry to the "DNS System Algorithm Numbers" registry with a recommended value of MAY in both the "Recommended for DNSSSEC Signing" and "Recommended for DNSSSEC Validation" columns requires RFC publication. Adding a new entry to, or changing existing values in the "DNS System Algorithm Numbers" registry with a value in the "Recommended for DNSSSEC Signing" or "Recommended for DNSSSEC Validation" columns other than MAY requires a Standards Action.¶
Adding a new entry to the "Digest Algorithms" registry with a recommended value of MAY in the "Recommended" column requires RFC publication. Adding a new entry to the "Digest Algorithms" registry with a value in the "Recommended" column other than MAY requires a Standards Action.¶
If an item is not marked as "RECOMMENDED", it does not necessarily mean that it is flawed; rather, it indicates that the item either has not been through the IETF consensus process, has limited applicability, or is intended only for specific use cases.¶
The following sections state the initial values to be populated into these rows, with values transcribed from [RFC8624].¶
Initial recommendation columns of implementation recommendations for the "Domain Name System Security (DNSSEC) Algorithm Numbers" are show in Table 1.¶
| Recommended for | Recommended for | ||
|---|---|---|---|
| Number | Mnemonics | DNSSEC Signing | DNSSEC Validation |
| 1 | RSAMD5 | MUST NOT | MUST NOT |
| 3 | DSA | MUST NOT | MUST NOT |
| 5 | RSASHA1 | MUST NOT | SHOULD NOT |
| 6 | DSA-NSEC3-SHA1 | MUST NOT | MUST NOT |
| 7 | RSASHA1-NSEC3-SHA1 | MUST NOT | SHOULD NOT |
| 8 | RSASHA256 | MUST | MUST |
| 10 | RSASHA512 | NOT | MUST |
| RECOMMENDED | |||
| 12 | ECC-GOST | MUST NOT | MUST NOT |
| 13 | ECDSAP256SHA256 | MUST | MUST |
| 14 | ECDSAP384SHA384 | MAY | RECOMMENDED |
| 15 | ED25519 | RECOMMENDED | RECOMMENDED |
| 16 | ED448 | MAY | RECOMMENDED |
Table 1
¶
Initial recommendation columns of implementation recommendations for the "DNSSEC Delegation Signer (DS) Resource Record (RR) Type Digest Algorithms" registry are shown in Table 2.¶
| Number | Mnemonics | DNSSEC Delegation | DNSSEC Validation |
|---|---|---|---|
| 0 | NULL (CDS only) | MUST NOT [*] | MUST NOT [*] |
| 1 | SHA-1 | MUST NOT | MUST |
| 2 | SHA-256 | MUST | MUST |
| 3 | GOST R 34.11-94 | MUST NOT | MAY |
| 4 | SHA-384 | MAY | RECOMMENDED |
Table 2
¶
The security of cryptographic systems depends on both the strength of the cryptographic algorithms chosen and the strength of the keys used with those algorithms. The security also depends on the engineering of the protocol used by the system to ensure that there are no non- cryptographic ways to bypass the security of the overall system.¶
This document concerns itself with the selection of cryptographic algorithms for the use of DNSSEC, specifically with the selection of "mandatory-to-implement" algorithms. The algorithms identified in this document as MUST or RECOMMENDED to implement are not known to be broken at the current time, and cryptographic research so far leads us to believe that they are likely to remain secure into the foreseeable future. However, this isn't necessarily forever, and it is expected that new revisions of this document will be issued from time to time to reflect the current best practices in this area.¶
Retiring an algorithm too soon would result in a zone signed with the retired algorithm being downgraded to the equivalent of an unsigned zone. Therefore, algorithm deprecation must be done very slowly and only after careful consideration and measurement of its use.¶
DNSKEY algorithm rollover in a live zone is a complex process. See [RFC6781] and [RFC7583] for guidelines on how to perform algorithm rollovers.¶
DS algorithm rollover in a live zone is also a complex process. Upgrading algorithm at the same time as rolling the new KSK key will lead to DNSSEC validation failures, and users MUST upgrade the DS algorithm first before rolling the Key Signing Key.¶
The IANA is requested to update the [DNSKEY-IANA] and [DS-IANA] registries as follows:¶
Add "Recommended for DNSSSEC Signing" and "Recommended for DNSSSEC Validation" columns to the "DNS Security Algorithm Numbers" registry ([DNSKEY-IANA]) and populate these columens with the values from Table 1.¶
Add a "Recommended" column to the "Digest Algorithms" registry ([DS-IANA]) and populate this column with the values from Table 2.¶
Update the registration policy for the [DNSKEY-IANA] registry to match the text describing update requirements above.¶
{Ed: We're not sure if this is the right policy, and this requires a good discussion with the WG. The purpose of much of this document is so that we can introduce TheNextBestAlgorithm by documenting TheNextBestAlgorithm in a new RFC and having it updating the IANA registry, instead of having to update RFC8624-bis-bis-bis-bis. We also, obviously, don't want someone to do something silly and mark an algorithm as "Recommended" without a good reason. This implies Standards Track. On the other hand we want to allow the ISE to add new algorithms (like the latest GOST algorithm), and, rightly or wrongly, the ISE doesn't publishes Std Track RFCs. Standards Action or IESG Approval seems like a reasonable compromise, but I'm not sure if it's the right one. We hope to present this to the WG at IEFT119 and get feedback.}¶
This document is based on, and extends, RFC 8624, which was authored by Paul Wouters, and Ondrej Sury.¶