Generic Security Service Application Program Interface (GSS-API): Delegate if Approved by Policy
RFC 5896

Internet Engineering Task Force (IETF)              L. Hornquist Astrand
Request for Comments: 5896                                   Apple, Inc.
Updates: 4120                                                 S. Hartman
Category: Standards Track                         Painless Security, LLC
ISSN: 2070-1721                                                June 2010

   Generic Security Service Application Program Interface (GSS-API):
                     Delegate if Approved by Policy

Abstract

   Several Generic Security Service Application Program Interface
   (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, including
   CIFS (Common Internet File System) file servers.  However, delegating
   the user credentials 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).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5896.

Hornquist Astrand & Hartman  Standards Track                    [Page 1]
RFC 5896         GSS-API: Delegate if Approved by Policy       June 2010

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . . . 3
   3.  GSS-API flag, C binding . . . . . . . . . . . . . . . . . . . . 3
   4.  GSS-API Behavior  . . . . . . . . . . . . . . . . . . . . . . . 3
   5.  Kerberos GSS-API Behavior . . . . . . . . . . . . . . . . . . . 4
   6.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   9.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5

1.  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, including
   CIFS file servers.  However, delegating user credentials 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.  An application
   requests delegation by setting the deleg_req_flag when calling
   init_sec_context.  This requires client applications to know what
   services should be trusted for delegation.

   However, blindly delegating to services for applications that do not
   need delegation is problematic.  In some cases, a central authority
   is in a better position than the client application to know what
   services should receive delegation.  Some GSS-API mechanisms have a

Hornquist Astrand & Hartman  Standards Track                    [Page 2]
RFC 5896         GSS-API: Delegate if Approved by Policy       June 2010