Network Working Group                                        N. Williams
Request for Comments: 5179                                           Sun
Category: Standards Track                                       May 2008


    Generic Security Service Application Program Interface (GSS-API)
  Domain-Based Service Names Mapping for the Kerberos V GSS Mechanism

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This document describes the mapping of Generic Security Service
   Application Program Interface (GSS-API) domain-name-based service
   principal names onto Kerberos V principal names.

Table of Contents

   1.  Domain-Based Names for the Kerberos V GSS-API Mechanism . . . . 2
   2.  Conventions Used in This Document . . . . . . . . . . . . . . . 2
   3.  Internationalization Considerations . . . . . . . . . . . . . . 2
   4.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 3
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 3

1.  Domain-Based Names for the Kerberos V GSS-API Mechanism

   In accordance with [RFC5178], this document provides the mechanism-
   specific details needed to implement GSS-API [RFC2743] domain-based
   service names with the Kerberos V GSS-API mechanism [RFC4121].

   GSS_C_NT_DOMAINBASED_SERVICE name SHOULD be mapped to Kerberos V
   principal names as follows:

   o  the <service> name becomes the first (0th) component of the
      Kerberos V principal name;

   o  the <hostname> becomes the second component of the Kerberos V
      principal name;

   o  the <domain> name becomes the third component of the Kerberos V
      principal name;

   o  the realm of the resulting principal name is that which
      corresponds to the domain name, treated as a hostname.

   The same name canonicalization considerations and methods as used
   elsewhere in the Kerberos V GSS-API mechanism [RFC4121] and Kerberos
   V [RFC4120] in general apply here.

   Implementations SHOULD use a Kerberos V name-type of
   NTT-SRVT-HST-DOMAIN (which has the value 12) but MAY use NT-UNKNOWN
   instead.

2.  Conventions Used in This Document

   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 [RFC2119].

3.  Internationalization Considerations

   It is unclear, at this time, how best to address internationalization
   of Kerberos V domain-based principal names.  This is because the
   Kerberos V core protocol internationalization project is incomplete.

   However, clearly the best way to interoperate when using Kerberos V
   domain-based principal names is to use ACE-encoded internationalized
   domain names [RFC3490] for the hostname and domain name slots of a
   Kerberos V domain-based principal name.  Therefore Kerberos V GSS-API
   mechanism implementations MUST do just that.

4.  Examples

   o  The domain-based name, of generic form,
      "ldap@foo.example@ds1.foo.example" may map to a Kerberos V
      principal name like: "ldap/ds1.foo.example/
      foo.example@FOO.EXAMPLE"

   o  The domain-based name, of generic form,
      "kadmin@foo.example@kdc1.foo.example" may map to a Kerberos V
      principal name like: "kadmin/kdc1.foo.example/
      foo.example@FOO.EXAMPLE"

5.  Security Considerations

   See [RFC5178].

   It is important for the security of protocols using the Kerberos V
   GSS-API mechanism and domain-based names, that the realm of domain-
   based principal names be derived from the hostname, rather than the
   domain name slots of the input domain-based name string.

6.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2743]  Linn, J., "Generic Security Service Application Program
              Interface Version 2, Update 1", RFC 2743, January 2000.

   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
              "Internationalizing Domain Names in Applications (IDNA)",
              RFC 3490, March 2003.

   [RFC4120]  Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
              Kerberos Network Authentication Service (V5)", RFC 4120,
              July 2005.

   [RFC4121]  Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos
              Version 5 Generic Security Service Application Program
              Interface (GSS-API) Mechanism: Version 2", RFC 4121,
              July 2005.

   [RFC5178]  Williams, N. and A. Melnikov, "Generic Security Service
              Application Program Interface (GSS-API)
              Internationalization and Domain-Based Service Names and
              Name Type", RFC 5178, May 2008.

Author's Address

   Nicolas Williams
   Sun Microsystems
   5300 Riata Trace Ct.
   Austin, TX  78727
   US

   EMail: Nicolas.Williams@sun.com

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