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Network Working Group W. Sanchez Request for Comments: 5397 C. Daboo Category: Standards Track Apple Inc.

                                                         December 2008
                 WebDAV Current Principal Extension

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.

Copyright Notice

 Copyright (c) 2008 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
 Provisions Relating to IETF Documents
 ( in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.


 This specification defines a new WebDAV property that allows clients
 to quickly determine the principal corresponding to the current
 authenticated user.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
 2.  Conventions Used in This Document . . . . . . . . . . . . . . . 2
 3.  DAV:current-user-principal  . . . . . . . . . . . . . . . . . . 3
 4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
 5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4
 6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 4

Sanchez & Daboo Standards Track [Page 1] RFC 5397 WebDAV Current Principal December 2008

1. Introduction

 WebDAV [RFC4918] is an extension to HTTP [RFC2616] to support
 improved document authoring capabilities.  The WebDAV Access Control
 Protocol ("WebDAV ACL") [RFC3744] extension adds access control
 capabilities to WebDAV.  It introduces the concept of a "principal"
 resource, which is used to represent information about authenticated
 entities on the system.
 Some clients have a need to determine which [RFC3744] principal a
 server is associating with the currently authenticated HTTP user.
 While [RFC3744] defines a DAV:current-user-privilege-set property for
 retrieving the privileges granted to that principal, there is no
 recommended way to identify the principal in question, which is
 necessary to perform other useful operations.  For example, a client
 may wish to determine which groups the current user is a member of,
 or modify a property of the principal resource associated with the
 current user.
 The DAV:principal-match REPORT provides some useful functionality,
 but there are common situations where the results from that query can
 be ambiguous.  For example, not only is an individual user principal
 returned, but also every group principal that the user is a member
 of, and there is no clear way to distinguish which is which.
 This specification proposes an extension to WebDAV ACL that adds a
 DAV:current-user-principal property to resources under access control
 on the server.  This property provides a URL to a principal resource
 corresponding to the currently authenticated user.  This allows a
 client to "bootstrap" itself by performing additional queries on the
 principal resource to obtain additional information from that
 resource, which is the purpose of this extension.  Note that while it
 is possible for multiple URLs to refer to the same principal
 resource, or for multiple principal resources to correspond to a
 single principal, this specification only allows for a single http(s)
 URL in the DAV:current-user-principal property.  If a client wishes
 to obtain alternate URLs for the principal, it can query the
 principal resource for this information; it is not the purpose of
 this extension to provide a complete list of such URLs, but simply to
 provide a means to locate a resource which contains that (and other)

2. Conventions Used in This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 document are to be interpreted as described in [RFC2119].

Sanchez & Daboo Standards Track [Page 2] RFC 5397 WebDAV Current Principal December 2008

 When XML element types in the namespace "DAV:" are referenced in this
 document outside of the context of an XML fragment, the string "DAV:"
 will be prefixed to the element type names.
 Processing of XML by clients and servers MUST follow the rules
 defined in Section 17 of WebDAV [RFC4918].
 Some of the declarations refer to XML elements defined by WebDAV

3. DAV:current-user-principal

 Name:  current-user-principal
 Namespace:  DAV:
 Purpose:  Indicates a URL for the currently authenticated user's
    principal resource on the server.
 Value:  A single DAV:href or DAV:unauthenticated element.
 Protected:  This property is computed on a per-request basis, and
    therefore is protected.
 Description:  The DAV:current-user-principal property contains either
    a DAV:href or DAV:unauthenticated XML element.  The DAV:href
    element contains a URL to a principal resource corresponding to
    the currently authenticated user.  That URL MUST be one of the
    URLs in the DAV:principal-URL or DAV:alternate-URI-set properties
    defined on the principal resource and MUST be an http(s) scheme
    URL.  When authentication has not been done or has failed, this
    property MUST contain the DAV:unauthenticated pseudo-principal.
    In some cases, there may be multiple principal resources
    corresponding to the same authenticated principal.  In that case,
    the server is free to choose any one of the principal resource
    URIs for the value of the DAV:current-user-principal property.
    However, servers SHOULD be consistent and use the same principal
    resource URI for each authenticated principal.
 COPY/MOVE behavior:  This property is computed on a per-request
    basis, and is thus never copied or moved.
    <!ELEMENT current-user-principal (unauthenticated | href)>
    <!-- href value: a URL to a principal resource -->

Sanchez & Daboo Standards Track [Page 3] RFC 5397 WebDAV Current Principal December 2008

    <D:current-user-principal xmlns:D="DAV:">

4. Security Considerations

 This specification does not introduce any additional security issues
 beyond those defined for HTTP [RFC2616], WebDAV [RFC4918], and WebDAV
 ACL [RFC3744].

5. Acknowledgments

 This specification is based on discussions that took place within the
 Calendaring and Scheduling Consortium's CalDAV Technical Committee.
 The authors thank the participants of that group for their input.
 The authors thank Julian Reschke for his valuable input via the
 WebDAV working group mailing list.

6. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
            Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
            Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
 [RFC3744]  Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web
            Distributed Authoring and Versioning (WebDAV)
            Access Control Protocol", RFC 3744, May 2004.
 [RFC4918]  Dusseault, L., "HTTP Extensions for Web Distributed
            Authoring and Versioning (WebDAV)", RFC 4918, June 2007.

Authors' Addresses

 Wilfredo Sanchez
 Apple Inc.
 1 Infinite Loop
 Cupertino, CA  95014

Sanchez & Daboo Standards Track [Page 4] RFC 5397 WebDAV Current Principal December 2008

 Cyrus Daboo
 Apple Inc.
 1 Infinite Loop
 Cupertino, CA  95014

Sanchez & Daboo Standards Track [Page 5]

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