NETWORK WORKING GROUP L. Zhu Internet-Draft Microsoft Corporation Updates: 4120 (if approved) June 2, 2006 Expires: December 4, 2006 Additional Kerberos Naming Constraits draft-ietf-krb-wg-naming-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 4, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document defines new naming constraints for reserved Keberos names. Names can be reserved for either the Kerberos principal name or the Kerberos realm name. The reserved names defined in this document are critical: if a reserved name is unknown, authentication MUST fail. Zhu Expires December 4, 2006 [Page 1]
Internet-Draft Kerberos Naming June 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . . 3 3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Reserved Kerberos Principal Names . . . . . . . . . . . . . 3 3.2. Reserved Kerberos Realm Names . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Zhu Expires December 4, 2006 [Page 2]
Internet-Draft Kerberos Naming June 2006 1. Introduction Occasionally protocol designers need to designate a Kerberos principal name name or a Kerberos realm name to have special meanings, other than identifying a particular instance. An example is that the protocol designers for the Kerberos anonymity support [ANON] need to define the Kerberos anonymous principal name and the Kerberos anonymous realm name, such that the anonymous name pair conveys no more meaning than that the client's identity is not revealed. In that case, it is critical that deployed Kerberos implementations MUST fail the authentication so that no access can be accidentally granted to a principal who's name happens to match with that of the anonymous identity. However Kerberos as defined in [RFC4120] does not have such reserved name spaces. As such, protocol designers have resolved to use exceedingly-unlikely-to-have-been-used names to avoid collision. Even if a registry can be setup to avoid collision for new implementations, there is no collision-free guarantee for deployed implementations. Accidental reuse of names can result in a security weakness. The Kerberos realm name has a reserved name space but none is defined and the criticality of unknown reserved realm names is not sufficiently specified. This document is to remedy that by defining the reserved name spaces for Kerberos names and these names are critical so that authentication MUST fail if an unknown reserved name is used by conforming implementations. 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. Definitions In this section, reserved names are defined for both the kerberos principal name and the kerberos realm name. 3.1. Reserved Kerberos Principal Names A new name type is defined for the reserved principal name as defined in Section 6.2 of [RFC4120]. Zhu Expires December 4, 2006 [Page 3]
Internet-Draft Kerberos Naming June 2006 KRB_NT_RESRVED 16 The reserved principal name MUST have at least two or more KerberosString components, and the first component must be the string literal "RESERVED". For implementations conforming with this specification, authentication MUST fail with KRB_AP_ERR_RESERVED_PRINCIPAL_NAME_UNKNOWN if an unknown reserved principal name is used. There is no accompanying error data for this error. KRB_AP_ERR_RESERVED_PRINCIPAL_NAME_UNKNOWN 82 -- a reserved Kerberos principal name is unknown 3.2. Reserved Kerberos Realm Names A new reserved realm name type is defined. This new name type is defined as the "other" style of the realm names as defined in Section 6.1 of [RFC4120]. other: RESERVED:real-name Namely the reserved realm names start with the literal "RESERVED:" For implementations conforming with this specification, authentication MUST fail with KRB_AP_ERR_RESERVED_REALM_NAME_UNKNOWN if an unknown reserved realm name is used. There is no accompanying error data for this error. KRB_AP_ERR_RESERVED_REALM_NAME_UNKNOWN 83 -- a reserved Kerberos realm name is unknown 4. Security Considerations If a reserved name is unknown, authentication MUST fail, otherwise, access can be granted unintentionally, resulting in a security weakness. Care MUST be taken to avoid accidental reuse of names. 5. Acknowledgements The initial document was mostly based on the author's conversation with Clifford Newman and Sam Hartman. Zhu Expires December 4, 2006 [Page 4]
Internet-Draft Kerberos Naming June 2006 6. IANA Considerations No IANA actions are required for this document. 7. Normative References [ANON] Zhu, L, Leach, P. and Jaganathan, K., "Kerberos Anonymity Support", draft-ietf-krb-wg-anon, work in progress. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999. [RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The Kerberos Network Authentication Service (V5)", RFC 4120, July 2005. Zhu Expires December 4, 2006 [Page 5]
Internet-Draft Kerberos Naming June 2006 Author's Address Larry Zhu Microsoft Corporation One Microsoft Way Redmond, WA 98052 US Email: lzhu@microsoft.com Zhu Expires December 4, 2006 [Page 6]
Internet-Draft Kerberos Naming June 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Zhu Expires December 4, 2006 [Page 7]
