Network Working Group L. Hornquist Astrand Internet-Draft Apple, Inc. Intended status: Standards Track S. Hartman Expires: February 14, 2009 Painless Security, LLC August 13, 2008 GSS-API: Delegate if approved by policy draft-lha-gssapi-delegate-policy-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 February 14, 2009. Copyright Notice Copyright (C) The IETF Trust (2008). Hornquist Astrand & Hartman Expires February 14, 2009 [Page 1] Internet-Draft GSS-API: Delegate if approved by policy August 2008 Abstract Several GSS-API applications work in a multi-tiered architecture, where the server takes advantage of delegated user credentials to act on behalf of the user and contact additional servers. In effect, the server acts as an agent on behalf of the user. Examples include web applications that need to access e-mail or file servers as well as CIFs file servers. However, delegating the ability to act as a user to a party who is not sufficiently trusted is problematic from a security standpoint. Kerberos provides a flag called OK-AS-DELEGATE that allows the administrator of a Kerberos realm to communicate that a particular service is trusted for delegation. This specification adds support for this flag and similar facilities in other authentication mechanisms to GSS-API (RFC 2743). Table of Contents 1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. GSS-API flag, c binding . . . . . . . . . . . . . . . . . . . 5 4. GSS-API behavior . . . . . . . . . . . . . . . . . . . . . . . 6 5. GSS-API behavior . . . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 8. Normative References . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . . . 12 Hornquist Astrand & Hartman Expires February 14, 2009 [Page 2] Internet-Draft GSS-API: Delegate if approved by policy August 2008 1. Requirements Notation 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]. Hornquist Astrand & Hartman Expires February 14, 2009 [Page 3] Internet-Draft GSS-API: Delegate if approved by policy August 2008 2. Introduction Several GSS-API applications work in a multi-tiered architecture, where the server takes advantage of delegated user credentials to act on behalf of the user and contact additional servers. In effect, the server acts as an agent on behalf of the user. Examples include web applications that need to access e-mail or file servers as well as CIFs file servers. However, delegating the ability to act as a user to a party who is not sufficiently trusted is problematic from a security standpoint. Today, GSS-API [RFC2743] leaves the determination of whether delegation is desired to the client application. If the client sets the deleg_req_flag to gss_init_sec_context then the application requests delegation. This requires client applications to know what services should be trusted for delegation. In some cases, however, a central authority is in a better position to know what services should receive delegation than the client application. Some mechanisms such as Kerberos [RFC4121] have a facility to allow a realm administrator to communicate that a particular service is a valid target for delegation. In Kerberos, the KDC can set the OK-AS- DELEGATE flag in issued tickets. However even in such a case, delegating to services for applications that do not need delegation is problematic. So, it is desirable for a GSS-API client to be able to request delegation if and only-if central policy reccomends delegation to the given target. This specification adds a new input flag to GSS_Init_sec_context to request delegation when approved by central policy. In addition, a constant value to be used in the GSS-API C bindings [RFC2744] is defined. Finally, the behavior for the Kerberos mechanism [RFC4121] is specified. Hornquist Astrand & Hartman Expires February 14, 2009 [Page 4] Internet-Draft GSS-API: Delegate if approved by policy August 2008 3. GSS-API flag, c binding The GSS_Init_sec_context API is extended to gain a new input flag: if the deleg_policy_req flag is set, then delegation should be performed if recommended by central policy. In addition, the C bindings are extended to define the following constant to represent this new flag. #define GSS_C_DELEG_POLICY_FLAG 32768 Hornquist Astrand & Hartman Expires February 14, 2009 [Page 5] Internet-Draft GSS-API: Delegate if approved by policy August 2008 4. GSS-API behavior As before, if the GSS_C_DELEG_FLAG is set, the GSS-API mechanism tries to delegate. Output ret_flags contains the flag GSS_C_DELEG_FLAG if delegation is successful. If the GSS_C_DELEG_POLICY_FLAG is set, the code delegates only if the mechanism policy allows delegation. If delegation is done, the output flag ret_flags contain both GSS_C_DELEG_FLAG and GSS_C_DELEG_POLICY_FLAG on the initator and GSS_C_DELEG_FLAG on the acceptor. If both GSS_C_DELEG_FLAG and GSS_C_DELEG_POLICY_FLAG are set, then delegation is attempted. However GSS_C_DELEG_POLICY_FLAG is only set in ret_flags on the initiator if GSS_C_DELEG_POLICY_FLAG would have been sufficient to request delegation. Hornquist Astrand & Hartman Expires February 14, 2009 [Page 6] Internet-Draft GSS-API: Delegate if approved by policy August 2008 5. GSS-API behavior If the GSS_C_DELEG_POLICY_FLAG is set, the Kerberos GSS-API mechanism will only delegate if ok-as-delegate is set [RFC4120] in the service ticket. Other policy checks MAY be applied. Hornquist Astrand & Hartman Expires February 14, 2009 [Page 7] Internet-Draft GSS-API: Delegate if approved by policy August 2008 6. Security Considerations Introduce a flag what allows client to get help from the KDC when to delegate to servers, will limit what servers that client delegate too. Hornquist Astrand & Hartman Expires February 14, 2009 [Page 8] Internet-Draft GSS-API: Delegate if approved by policy August 2008 7. IANA Considerations This section needs to be revised to be consistent with the kitten IANA draft. Hornquist Astrand & Hartman Expires February 14, 2009 [Page 9] Internet-Draft GSS-API: Delegate if approved by policy August 2008 8. 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. [RFC2744] Wray, J., "Generic Security Service API Version 2 : C-bindings", RFC 2744, January 2000. [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. Hornquist Astrand & Hartman Expires February 14, 2009 [Page 10] Internet-Draft GSS-API: Delegate if approved by policy August 2008 Authors' Addresses Love Hornquist Astrand Apple, Inc. Email: lha@apple.com Sam Hartman Painless Security, LLC Email: hartmans-ietf@mit.edu Hornquist Astrand & Hartman Expires February 14, 2009 [Page 11] Internet-Draft GSS-API: Delegate if approved by policy August 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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. 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, THE IETF TRUST 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. 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