IANA Registry Updates for TLS and DTLS

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Table of Contents

1. Introduction

This document instructs IANA to make changes to a number of the IANA registries related to Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS). These changes update the changes made in [RFC8447].¶

This specification updates the "Recommended" column in TLS registries to define a third value "D" for items that are discouraged.¶

2. Terminology

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.¶

3. Adding "Recommended" Column

The instructions in this document update the Recommended column, originally added in [RFC8447] to add a third value, "D", indicating that a value is "Discouraged". The permitted values are:¶

Y:

Indicates that the IETF has consensus that the item is RECOMMENDED. This only means that the associated mechanism is fit for the purpose for which it was defined. Careful reading of the documentation for the mechanism is necessary to understand the applicability of that mechanism. The IETF could recommend mechanisms that have limited applicability, but will provide applicability statements that describe any limitations of the mechanism or necessary constraints on its use.¶

N:

Indicates that the item has not been evaluated by the IETF and that the IETF has made no statement about the suitability of the associated mechanism. This does not necessarily mean that the mechanism is flawed, only that no consensus exists. The IETF might have consensus to leave an items marked as "N" on the basis of it having limited applicability or usage constraints.¶

D:

Indicates that the item is discouraged. This marking could be used to identify mechanisms that might result in problems if they are used, such as a weak cryptographic algorithm or a mechanism that might cause interoperability problems in deployment. Implementers SHOULD consult the linked references associated with the item to determine the conditions under which it SHOULD NOT or MUST NOT be used.¶

Setting a value to "Y" or "D" in the "Recommended" column requires IETF Standards Action [RFC8126]. Any state transition to or from a "Y" or "D" value requires IESG Approval. Not all items defined in Standards Track RFCs need to be set to "Y" or "D". Any item not otherwise specified is set to "N". The column is blank for values that are unassigned or reserved unless specifically set.¶

4. TLS ExtensionType Values

In order to refect the changes in the Recommended column allocation, IANA SHALL update the TLS ExtensionType Values registry as follows:¶

• Change the registration procedure to:¶

    Values with the first byte in the range 0-254 (decimal) are assigned
    via Specification Required [RFC8126].  Values with the first byte
    255 (decimal) are reserved for Private Use [RFC8126].  Setting a
    "Recommended" column value to "Y" or "D" requires Standards Action [RFC8126].
    Any state transition to or from a "Y" or "D" value requires
    IESG Approval.

• Add a reference to this document under the reference heading.¶

• Update the "Recommended" column with the changes as listed below. Entries keep their existing "Y" and "N" entries except for the entries in following table. A reference to this document SHALL be added to these entries.¶

• Update note on the recommended column with text in Section 3.1.¶

5. TLS Cipher Suites Registry

Several categories of ciphersuites are discouraged for general use and are maked as "D".¶

Ciphersuites that use NULL encryption do not provide the confidentiality normally expected of TLS. Protocols and applications are often designed to require confidentialy as a security property. These ciphersuites MUST NOT be used in those cases.¶

Ciphersuites marked as EXPORT use weak ciphers and were deprecated in TLS 1.1 [RFC4346].¶

Cipher suites maked as anon do not provide any authentication and are vulnerable to man-in-the-middle attacks and are deprecated in TLS 1.1 [RFC4346].¶

RC4 is a weak cipher and is deprecated in [RFC7465].¶

DES and IDEA are not considered secure for general use and are deprecated in [RFC5469].¶

In order to refect the changes in the Recommended column allocation, IANA SHALL update the TLS ExtensionType Values registry as follows:¶

• Change the registration procedure to:¶

    Values with the first byte in the range 0-254 (decimal) are
    assigned via Specification Required [RFC8126].  Values with the
    first byte 255 (decimal) are reserved for Private Use [RFC8126].
    Setting a "Recommended" column value to "Y" or "D" requires Standards
    Action [RFC8126]. Any state transition to or from a "Y" or "D"
    value requires IESG Approval.

• Add a reference to this document under the reference heading.¶

• Update the "Recommended" column with the changes as listed below. Entries keep their existing "Y" and "N" entries except for the entries in following table. A reference to this document SHALL be added to these entries. This document does not make any changes to the DTLS-OK column.¶

• Update note on the recommended column with text in Section 3.1.¶

6. TLS Supported Groups

In order to refect the changes in the Recommended column allocation, IANA SHALL update the TLS Supported Groups registry as follows:¶

• Update the registration policy to include:¶

    Setting a "Recommended" column value to "Y" or "D" requires Standards
    Action [RFC8126]. Any state transition to or from a "Y" or "D"
    value requires IESG Approval.

• Add a reference to this document under the reference heading.¶

• Update the "Recommended" column with the changes as listed below. Entries keep their existing "Y" and "N" entries except for the entries in following table. A reference to this document SHALL be added to these entries.¶

• Update note on the recommended column with text in Section 3.1.¶

7. TLS Exporter Labels Registry

This document updates the registration procedure for the TLS Exporter registry and updates the Recommended column allocation. IANA SHALL update the TLS Exporter Labels Registry as follows:¶

• Change the registration procedure from Specification Required to Expert Review and update it to include:¶

    Setting a "Recommended" column value to "Y" or "D" requires Standards
    Action [RFC8126]. Any state transition to or from a "Y" or "D"
    value requires IESG Approval.

• Add a reference to this document under the reference heading.¶

• Entries keep their existing Recommended column "Y" and "N" entries¶

• Update note on the recommended column with text in Section 3.1.¶

• update the note on the role of the expert reviewer as follows.¶

Note:

The role of the designated expert is described in [RFC8447]. Even though this registry does not require a specification, the designated expert [RFC8126] will strongly encourage registrants to provide a link to a publicly available specification. An Internet-Draft (that is posted and never published as an RFC) or a document from another standards body, industry consortium, university site, etc. are suitable for these purposes. The expert may provide more in-depth reviews, but their approval should not be taken as an endorsement of the exporter label. The expert also verifies that the label is a string consisting of printable ASCII characters beginning with "EXPORTER". IANA MUST also verify that one label is not a prefix of any other label. For example, labels "key" or "master secretary" are forbidden.¶

8. TLS Certificate Types

In order to refect the changes in the Recommended column allocation, IANA SHALL update the the TLS Certificate Types registry as follows:¶

• Change the registration procedure to:¶

    Values in the range 0-223 (decimal) are assigned via Specification
    Required [RFC8126]. Values in the range 224-255 (decimal) are
    reserved for Private Use [RFC8126]. Setting a "Recommended" column
    value to "Y" or "D" requires Standards
    Action [RFC8126]. Any state transition to or from a "Y" or "D"
    value requires IESG Approval.

• Add a reference to this document under the reference heading.¶

• Entries keep their existing Recommended column "Y" and "N" entries.¶

• Update note on the recommended column with text in Section 3.1.¶

9. TLS HashAlgorithm Registry

Though TLS 1.0 and TLS 1.1 were deprecated [RFC8996], TLS 1.2 will be in use for some time. In order to refect the changes in the Recommended column allocation, IANA SHALL update the TLS HashAlgorithm Registry registry as follows:¶

• Update the registration procedure to include:¶

    Setting a "Recommended" column value to "Y" or "D" requires Standards
    Action [RFC8126]. Any state transition to or from a "Y" or "D"
    value requires IESG Approval.

• Add a reference to this document under the reference heading.¶

• Update the TLS HashAlgorithm registry to add a "Recommended" column as follows:¶

• Add note on the recommended column with text in Section 3.1.¶

10. TLS SignatureAlgorithm registry

Though TLS 1.0 and TLS 1.1 were deprecated [RFC8996], TLS 1.2 will be in use for some time. In order to refect the changes in the Recommended column allocation, IANA SHALL update the TLS SignatureAlgorithm registry registry as follows:¶

• Update the registration procedure to include:¶

    Setting a "Recommended" column value to "Y" or "D" requires Standards
    Action [RFC8126]. Any state transition to or from a "Y" or "D"
    value requires IESG Approval.

• Add a reference to this document under the reference heading.¶

• Update the TLS SignatureAlgorithm registry to add a "Recommended" column as follows:¶

• Add note on the recommended column with text in Section 3.1.¶

11. TLS ClientCertificateTypes registry

Though TLS 1.0 and TLS 1.1 were deprecated [RFC8996], TLS 1.2 will be in use for some time. In order to refect the changes in the Recommended column allocation, IANA SHALL update the TLS ClientCertificateTypes registry as follows:¶

• Update the registration procedure to include:¶

    Setting a "Recommended" column value to "Y" or "D" requires Standards
    Action [RFC8126]. Any state transition to or from a "Y" or "D"
    value requires IESG Approval.

• Add a reference to this document under the reference heading.¶

• Update the TLS ClientCertificateTypes registry to add a "Recommended" column as follows:¶

• Add note on the recommended column with text in Section 3.1.¶

12. TLS PskKeyExchangeMode registry

In order to refect the changes in the Recommended column allocation, IANA SHALL update the TLS PskKeyExchangeMode registry as follows:¶

• Update the registration procedure to include:¶

    Setting a "Recommended" column value to "Y" or "D" requires Standards
    Action [RFC8126]. Any state transition to or from a "Y" or "D"
    value requires IESG Approval.

• Add a reference to this document under the reference heading.¶

• Entries keep their existing recommended column "Y" and "N" entries.¶

• Update note on the recommended column with text in Section 3.1.¶

13. Adding "Comment" Column

IANA is requested to add a "Comment" column to the following registries:¶

• TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs¶

• TLS CachedInformationType Values¶

• TLS Certificate Compression Algorithm IDs¶

• TLS Cipher Suites¶

• TLS ContentType¶

• TLS EC Point Formats¶

• TLS EC Curve Types¶

• TLS Supplemental Data Formats (SupplementalDataType)¶

• TLS UserMappingType Values¶

• TLS Authorization Data Formats¶

• TLS Heartbeat Message Types¶

• TLS Heartbeat Modes¶

• TLS SignatureScheme¶

• TLS PskKeyExchangeMode¶

• TLS KDF Identifiers¶

This list of registries is all registries that do not already have a "Comment" or "Notes" column or that were not orphaned by TLS 1.3. The TLS ExtensionType Values is not listed above because it has the "TLS 1.3" column.¶

14. Security Considerations

The change to Specification Required from IETF Review lowers the amount of review provided by the WG for cipher suites and supported groups. This change reflects reality in that the WG essentially provided no cryptographic review of the cipher suites or supported groups. This was especially true of national cipher suites.¶

Recommended algorithms are regarded as secure for general use at the time of registration; however, cryptographic algorithms and parameters will be broken or weakened over time. It is possible that the "Recommended" status in the registry lags behind the most recent advances in cryptanalysis. Implementers and users need to check that the cryptographic algorithms listed continue to provide the expected level of security.¶

Designated experts ensure the specification is publicly available. They may provide more in-depth reviews. Their review should not be taken as an endorsement of the cipher suite, extension, supported group, etc.¶

15. IANA Considerations

This document is entirely about changes to TLS-related IANA registries.¶

16. Normative References

[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>.

[RFC4346]

Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, DOI 10.17487/RFC4346, April 2006, <https://www.rfc-editor.org/rfc/rfc4346>.

[RFC5469]

Eronen, P., Ed., "DES and IDEA Cipher Suites for Transport Layer Security (TLS)", RFC 5469, DOI 10.17487/RFC5469, February 2009, <https://www.rfc-editor.org/rfc/rfc5469>.

[RFC7465]

Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465, DOI 10.17487/RFC7465, February 2015, <https://www.rfc-editor.org/rfc/rfc7465>.

[RFC8126]

Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/rfc/rfc8126>.

[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>.

[RFC8447]

Salowey, J. and S. Turner, "IANA Registry Updates for TLS and DTLS", RFC 8447, DOI 10.17487/RFC8447, August 2018, <https://www.rfc-editor.org/rfc/rfc8447>.

[RFC8996]

"*** BROKEN REFERENCE ***".

Authors' Addresses