Move Kerberos protocol parameter registries to IANA

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in .

The Keberos 5 network authentication protocol has several numeric protocol parameters. This document requests that IANA take over the maintenance of the Kerberos protocol parameters that are not currently under IANA maintenance. Several instances of number conflicts in Kerberos implementations could have been prevented by having IANA registries for those numbers. This document updates .

Unless otherwise specified, each Kerberos protocol number registry will have the following fields: "number", "name", "reference", and "comments". The name must begin with a lowercase letter, and must consist of ASCII letters, digits, and hyphens. Two or more hyphens must not appear directly adjacent to each other. A hyphen must not appear at the end of a name. It is preferred that words in a name be separated by hyphens, and that all of the letters be lowercase. (These rules are consistent with the lexical rules for an ASN.1 valuereference or identifier. Where the constraints are stricter than the ASN.1 lexical rules, they make it easier to systematically transform the names for use in implementation languages.) Names for numeric parameter values have no inherent meaning in the Kerberos protocol, but they can guide choices for internal implementation symbol names and for user-visible non-numeric representations. When written in English prose in specifications, or when used as symbolic constants in implementation languages (e.g., C preprocessor macros), it is common to transform the name into all uppercase letters, and possibly to replace hyphens with underscores.

This document requests that the IESG establish a pool of Kerberos experts who will manage the Kerberos registries using these guidelines. The IESG may wish to consider including the set of designated IANA experts for existing Kerberos IANA registries as candidates for this pool. IANA will select an expert from this pool for each registration request. The expert will review the registration request and may approve the registration, decline the registration with comments, or recommend that the registration request should follow a specific alternative process. The alternative processes that the expert may recommend are the IETF review process and the standards action process. Initially, the expert reviewers will use a permissive process, generally approving registrations that are architecturally consistent with Kerberos and the protocol parameter in question. Over time, with input from the community, the experts may refine the requirements that registrations are expected to meet. The experts will maintain a current version of these guidelines in a manner that is generally accessible to the entire community. As the guidelines evolve, experts may consider the technical quality of specifications, security impacts of the registrations, architectural consistency, and interoperability impact. Experts may require a publicly available specification in order to make certain registrations. [ For the individual registries, include "Registrations in this registry are managed by the expert review process or in exceptional cases by IESG approval. See section x for guidelines for the experts to be used with this registry." ]

Names for integer assignments must be unique across all Kerberos integer parameter registries. This is normally accomplished by including a name prefix that identifies the registry. Assignments for integers parameters will follow the general registration procedure outlined above, except as otherwise noted in the section that contains the description of the parameter. Kerberos integer parameters take on signed 32-bit values (-2147483648 to 2147483647). Negative values are for private or local use.

Address types General registration procedure Signed 32-bit integers Address types historically align with numeric constants used in the Berkeley sockets API. Future address type assignments should conform to this historical practice when possible. The name prefix for address types is "addrtype-".

Authorization data types General registration procedure Signed 32-bit integers The name prefix for authorization data types is "ad-".

Error codes Standards action Signed 32-bit integers Assignments for error codes require standards action due to their scarcity: assigning error codes greater than 127 could require significant changes to certain implementations. The name prefixes for error codes are "kdc-err-", "krb-err-", and "krb-ap-err-".

Key usages General registration procedure Unsigned 32-bit integers Key usages are unsigned 32-bit integers (0 to 4294967295). Zero is reserved and may not be assigned. The name prefix for key usages is "ku-".

Name types General registration procedure Signed 32-bit integers The name prefix for name types is "nt-". number name reference comment 0 nt-unknown RFC4120 Name type not known 1 nt-principal RFC4120 Just the name of the principal as in DCE, or for users 2 nt-srv-inst RFC4120 Service and other unique instance (krbtgt) 3 nt-srv-hst RFC4120 Service with host name as instance (telnet, rcommands) 4 nt-srv-xhst RFC4120 Service with host as remaining components 5 nt-uid RFC4120 Unique ID 6 nt-x500-principal RFC4120 Encoded X.509 Distinguished name [RFC2253] 7 nt-smtp-name RFC4120 Name in form of SMTP email name (e.g., user@example.com) 10 nt-enterprise RFC4120 Enterprise name - may be mapped to principal name 11 nt-wellknown RFC6111 Well-known principal name 12 nt-srv-hst-domain RFC5179 Domain-based names

Pre-authentication and typed data General registration procedure Signed 32-bit integers This document requests that IANA modify the existing Kerberos Pre-authentication and typed data registry to be consistent with the procedures in this document. The name prefix for pre-authentication type numbers is "pa-". The name prefix for typed data numbers is "td-". Pre-authentication and typed data numbers are in the same registry, but a pre-authentication number may be also be assigned to a related typed data number.

Assignments for named bits require standards action, due to their scarcity: assigning bit numbers greater than 31 could require significant changes to implementations. Names for named bit assignments must be unique within a given named bit registry, and typically do not have name prefixes that identify which registry they belong to.

AP-REQ options Standards action ASN.1 bit numbers 0 through 31

KDC-REQ options Standards action ASN.1 bit numbers 0 through 31

Ticket flags Standards action ASN.1 bit numbers 0 through 31

ASN.1 application tag numbers (which are always equal to the "msg-type" field in Kerberos messages where they appear) will not be registered. Any Kerberos protocol change that requires a new application tag number will be a sufficiently major change that the specification of the change MUST define a new ASN.1 module and MUST be Standards Track. Transited encoding values will not be registered. There is only one transited encoding type for the Kerberos protocol. The interoperability concerns inherent to the cross-realm operation of Kerberos mean that specifications of new transited encoding types are very unlikely. Any specification of new transited encoding types MUST be Standards Action. Protocol version number (pvno) values will not be registered. The location of the "pvno" value in Kerberos messages is not in a place that implementations can meaningfully use to distinguish among different variants of the Kerberos protocol.

Sam Hartman proposed the text of the expert review guidelines. Love Hornquist Astrand wrote a previous document (draft-lha-krb-wg-some-numbers-to-iana-00) with the same goals as this document.

Thanks to Tom Petch for providing useful feedback on previous versions of this document.

Assignments of new Keberos protocol parameter values can have security implications. In cases where the assignment policy calls for expert review, the reviewer is responsible for evaluating whether adequate documentation exists concerning the security considerations for the requested assignment. For assignments that require IETF review or standards action, the normal IETF processes ensure adequate treatment of security considerations.

This document requests that IANA create several registries for Kebreros protocol parameters: Address types Authorization data types Error codes Key usages Name types AP-REQ options KDC-REQ options Ticket flags This document requests that IANA modify the existing "Pre-authentication data and typed data" registry to contain an additional reference to this document, and to transform existing names in that registry to the lowercase-and-hyphens style.

Do we make a registry for application tag numbers (equal to message type numbers)? We've said that we would replace the entire ASN.1 module in that case, but Nico's recent proposal doesn't do that, and if we want to accommodate that sort of proposal, it would probably be best to establish a registry. (It should require standards action for registrations.) Do transited encodings need a registry? They would probably require standards action, even if there were a registry.