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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 RFC 3744

INTERNET-DRAFT                    Geoffrey Clemm, Rational Software
draft-ietf-webdav-acl-07          Anne Hopkins, Microsoft Corporation
                                  Eric Sedlar, Oracle Corporation
                                  Jim Whitehead, U.C. Santa Cruz

Expires May 9, 2001               November 9, 2001

                     WebDAV Access Control Protocol

Status of this Memo

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.

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.


Abstract

This document specifies a set of methods, headers, and message bodies
that define Access Control extensions to the WebDAV Distributed
Authoring Protocol. This protocol permits a client to read and modify
access control lists that instruct a server whether to allow or deny
operations upon a resource (such as HTTP method invocations) by a given
principal.

This document is a product of the Web Distributed Authoring and
Versioning (WebDAV) working group of the Internet Engineering Task
Force. Comments on this draft are welcomed, and should be addressed to
the acl@webdav.org mailing list. Other related documents can be found at
http://www.webdav.org/acl/, and http://www.ics.uci.edu/pub/ietf/webdav/.












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Table of Contents

1 INTRODUCTION.......................................................5
1.1 Terms............................................................7
1.2 Notational Conventions...........................................8

2 PRINCIPALS.........................................................8

3 PRIVILEGES.........................................................9
3.1 DAV:read Privilege..............................................11
3.2 DAV:write Privilege.............................................11
3.3 DAV:read-acl Privilege..........................................11
3.4 DAV:read-current-user-privilege-set Privilege...................11
3.5 DAV:write-acl Privilege.........................................12
3.6 DAV:all Privilege...............................................12
3.7 Aggregation of Predefined Privileges............................12

4 PRINCIPAL PROPERTIES..............................................12
4.1 DAV:alternate-URI-set...........................................13

5 ACCESS CONTROL PROPERTIES.........................................13
5.1 DAV:owner.......................................................13
 5.1.1 Example: Retrieving DAV:owner................................14
 5.1.2 Example: An Attempt to Set DAV:owner.........................15
5.2 DAV:supported-privilege-set.....................................16
 5.2.1 Example: Retrieving a List of Privileges Supported on a
       Resource.....................................................16
5.3 DAV:current-user-privilege-set..................................18
 5.3.1 Example: Retrieving the User's Current Set of Assigned
 Privileges.........................................................19
5.4 DAV:acl.........................................................20
 5.4.1 ACE Principal................................................20
 5.4.2 ACE Grant and Deny...........................................21
 5.4.3 ACE Protection...............................................21
 5.4.4 ACE Inheritance..............................................22
 5.4.5 Example: Retrieving a Resource's Access Control List......22
5.5 DAV:acl-semantics...............................................23
 5.5.1 Example: Retrieving DAV:acl-semantics........................24
5.6 DAV:principal-collection-set....................................25
 5.6.1 Example: Retrieving DAV:principal-collection-set.............26
5.7 Example: PROPFIND to retrieve access control properties.........27

6 ACL SEMANTICS.....................................................30
6.1 ACE Combination.................................................31
 6.1.1 DAV:first-match ACE Combination..............................31
 6.1.2 DAV:all-grant-before-any-deny ACE Combination................31
 6.1.3 DAV:specific-deny-overrides-grant ACE Combination............31
6.2 ACE Ordering....................................................31
 6.2.1 DAV:deny-before-grant ACE Ordering...........................32
6.3 Allowed ACE.....................................................32
 6.3.1 DAV:principal-only-one-ace ACE Constraint....................32

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 6.3.2 DAV:grant-only ACE Constraint................................32
6.4 Required Principals.............................................32

7 ACCESS CONTROL AND EXISTING METHODS...............................32
7.1 OPTIONS.........................................................33
 7.1.1 Example - OPTIONS............................................33
7.2 MOVE............................................................33
7.3 COPY............................................................33
7.4 DELETE..........................................................33
7.5 LOCK............................................................34

8 ACCESS CONTROL METHODS............................................34
8.1 ACL.............................................................34
 8.1.1 ACL Preconditions............................................34
 8.1.2 Example: the ACL method......................................36
 8.1.3 Example: ACL method failure due to protected ACE conflict....37
 8.1.4 Example: ACL method failure due to an inherited ACE conflict 38
 8.1.5 Example: ACL method failure due to an attempt to set grant
       and deny in a single ACE.....................................39

9 ACCESS CONTROL REPORTS............................................40
9.1 REPORT Method...................................................40
9.2 DAV:acl-principal-props Report..................................40
 9.2.1 Example: DAV:acl-principal-props Report......................40
9.3 DAV:principal-match REPORT......................................42
 9.3.1 Example: DAV:principal-match REPORT..........................43
9.4 DAV:principal-property-search REPORT............................44
 9.4.1 Matching.....................................................45
 9.4.2 Example: successful DAV:principal-property-search REPORT.....46
 9.4.3 Example: Unsuccessful DAV:principal-property-search REPORT...48
9.5 DAV:principal-search-property-set REPORT........................49
 9.5.1 Example: DAV:principal-search-property-set REPORT............50

10  XML PROCESSING..................................................51

11  INTERNATIONALIZATION CONSIDERATIONS.............................51

12  SECURITY CONSIDERATIONS.........................................52
12.1  Increased Risk of Compromised Users...........................52
12.2  Risks of the DAV:read-acl and DAV:current-user-privilege-set
      Privileges....................................................52
12.3  No Foreknowledge of Initial ACL...............................53

13  AUTHENTICATION..................................................53

14  IANA CONSIDERATIONS.............................................53

15  INTELLECTUAL PROPERTY...........................................54

16  ACKNOWLEDGEMENTS................................................54

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17  REFERENCES......................................................55
17.1  Normative References..........................................55
17.2  Informational References......................................56

18  AUTHORS' ADDRESSES..............................................56

19  APPENDICIES.....................................................57
19.1  XML Document Type Definition..................................57

20  NOTE TO RFC EDITOR..............................................59









































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1  INTRODUCTION

   The goal of the WebDAV access control extensions is to provide an
   interoperable mechanism for handling discretionary access control for
   content and metadata managed by WebDAV servers.  WebDAV access
   control can be implemented on content repositories with security as
   simple as that of a UNIX file system, as well as more sophisticated
   models.  The underlying principle of access control is that who you
   are determines what operations you can perform on a resource. The
   "who you are" is defined by a "principal" identifier; users, client
   software, servers, and groups of the previous have principal
   identifiers. The "operations you can perform" is determined by a
   single "access control list" (ACL) associated with a resource.  An
   ACL contains a set of "access control entries" (ACEs), where each ACE
   specifies a principal and a set of privileges that are either granted
   or denied to that principal. When a principal submits an operation
   (such as an HTTP or WebDAV method) to a resource for execution, the
   server evaluates the ACEs in the ACL to determine if the principal
   has permission for that operation.

   Since every ACE contains the identifier of a principal, client
   software operated by a human must provide a mechanism for selecting
   this principal. This specification uses http(s) scheme URLs to
   identify principals, which are represented as WebDAV-capable
   resources. There is no guarantee that the URLs identifying principals
   will be meaningful to a human. For example,
   http://www.dav.org/u/256432 and http://www.dav.org/people/Greg.Stein
   are both valid URLs that could be used to identify the same
   principal. To remedy this, every principal resource has the
   DAV:displayname property containing a human-readable name for the
   principal.

   Since a principal can be identified by multiple URLs, it raises the
   problem of determining exactly which principal's operations are being
   described in a given ACE. It is impossible for a client to determine
   that an ACE granting the read privilege to
   http://www.dav.org/people/Greg.Stein also affects the principal at
   http://www.dav.org/u/256432. That is, a client has no mechanism for
   determining that two URLs identify the same principal resource.  As a
   result, this specification requires clients to use just one of the
   many possible URLs for a principal when creating ACEs. A client can
   discover this URL by retrieving the DAV:principal-URL property
   (Section 4.2) from a principal resource. No matter which of the
   principal's URLs is used with PROPFIND, the property always returns
   the same URL.

   Once a system has hundreds to thousands of principals, the problem
   arises of how to allow a human operator of client software to select
   just one of these principals. One approach is to use broad collection

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   hierarchies to spread the principals over a large number of
   collections, yielding few principals per collection. An example of
   this is a two level hierarchy with the first level containing 36
   collections (a-z, 0-9), and the second level being another 36,
   creating collections /a/a/, /a/b/, à, /a/z/, such that a principal
   with last name "Stein" would appear at /s/t/Stein. In effect, this
   pre-computes a common query, search on last name, and encodes it into
   a hierarchy. The drawback with this scheme is that it handles only a
   small set of predefined queries, and drilling down through the
   collection hierarchy adds unnecessary steps (navigate down/up) when
   the user already knows the principal's name. While organizing
   principal URLs into a hierarchy is a valid namespace organization,
   users should not be forced to navigate this hierarchy to select a
   principal.

   This specification provides the capability to perform substring
   searches on a small set of properties on the resources representing
   principals. This permits searches based on last name, first name,
   user name, job title, etc. Two separate searches are supported, via
   the REPORT method, one to search principal resources, the other to
   determine which properties may be searched at all.

   Once a principal has been identified in an ACE, a server evaluating
   that ACE must know the identity of the principal making a protocol
   request, and must validate that that principal is who they claim to
   be, a process known as authentication. This specification
   intentionally omits discussion of authentication, as the HTTP
   protocol already has a number of authentication mechanisms [RFC2617].
   Some authentication mechanism (such as HTTP Digest Authentication,
   which all WebDAV compliant implementations are required to support)
   must be available to validate the identity of a principal.

   The following issues are out of scope for this document:

        * Access control that applies only to a particular property on a
          resource (excepting the access control properties DAV:acl and
          DAV:current-user-privilege-set), rather than the entire
          resource,

        * Role-based security (where a role can be seen as a dynamically
          defined collection of principals),

        * Specification of the ways an ACL on a resource is initialized,

        * Specification of an ACL that applies globally to all
          resources, rather than to a particular resource.

        * Creation and maintenance of resources representing people or
          computational agents (principals), and groups of these.

   This specification is organized as follows. Section 1.1 defines key
   concepts used throughout the specification, and is followed by a more

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   in-depth discussion of principals (Section 2), and privileges
   (Section 3). Properties defined on principals are specified in
   Section 4, and access control properties for content resources are
   specified in Section 5. The semantics of access control lists are
   described in Section 6, including sections on ACE combination
   (Section 6.1), ACE ordering (Section 6.2), and principals required to
   be present in an ACE (Section 6.4). Client discovery of access
   control capability using OPTIONS is described in Section 7.1.
   Interactions between access control functionality and existing HTTP
   and WebDAV methods are described in the remainder of Section 7. The
   access control setting method, ACL, is specified in Section 8. Four
   reports that provide limited server-side searching capabilities are
   described in Section 9. A note on XML processing (Section 10),
   Internationalization considerations (Section 11), security
   considerations (Section 12), and a note on authentication (Section
   13) round out the specification. An appendix (Section 19.1) provides
   an XML Document Type Definition (DTD) for the XML elements defined in
   the specification.

1.1 Terms

   This draft uses the terms defined in HTTP [RFC2616] and WebDAV
   [RFC2518].  In addition, the following terms are defined:

   principal

     A "principal" is a distinct human or computational actor that
     initiates access to network resources.  In this protocol, a
     principal is an HTTP resource that represents such an actor.

   principal collection

     A "principal collection" is a group of principals, and is
     represented in this protocol by a WebDAV collection containing HTTP
     resources that represent principals, and principal collections.

   privilege

     A "privilege" controls access to a particular set of HTTP
     operations on a resource.

   aggregate privilege

     An "aggregate privilege" is a privilege that contains a set of
     other privileges.

   abstract privilege

     The modifier "abstract", when applied to a privilege, means the
     privilege cannot be set in an access control element (ACE).

   access control list (ACL)

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     An "ACL" is a list of access control elements that define access
     control to a particular resource.

   access control element (ACE)

     An "ACE" either grants or denies a particular set of (non-abstract)
     privileges for a particular principal.

   inherited ACE

     An "inherited ACE" is an ACE that is dynamically shared from the
     ACL of another resource. When a shared ACE changes on the primary
     resource, it is also changed on inheriting resources.

   protected property

    A "protected property" is one whose value cannot be updated except
    by a method explicitly defined as updating that specific property.
    In particular, a protected property cannot be updated with a
    PROPPATCH request.

1.2 Notational Conventions

   The augmented BNF used by this document to describe protocol elements
   is described in Section 2.1 of [RFC2616]. Because this augmented BNF
   uses the basic production rules provided in Section 2.2 of [RFC2616],
   those rules apply to this document as well.

   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].

   Definitions of XML elements in this document use XML element type
   declarations (as found in XML Document Type Declarations), described
   in Section 3.2 of [REC-XML]. When an XML element type in the "DAV:"
   namespace is referenced in this document outside of the context of an
   XML fragment, the string "DAV:" will be prefixed to the element type.


2  PRINCIPALS

   A principal is a network resource that represents a distinct human or
   computational actor that initiates access to network resources. Users
   and groups are represented as principals in many implementations;
   other types of principals are also possible. A URI of any scheme MAY
   be used to identify a principal resource. However, servers
   implementing this specification MUST expose principal resources at an
   http(s) URL, which is a privileged scheme that points to resources
   that have additional properties, as described in Section 4. So, a
   principal resource can have multiple URIs, one of which has to be an
   http(s) scheme URL. Although an implementation SHOULD support

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   PROPFIND and MAY support PROPPATCH to access and modify information
   about a principal, it is not required to do so.

   A principal resource may or may not be a collection.  If a person or
   computational agent matches a principal resource that is contained by
   a collection principal, they also match the collection principal.
   This definition is recursive, and hence if a person or computational
   agent matches a collection principal that is the child of another
   collection principal, they also match the parent collection
   principal. Membership in a collection principal is also recursive, so
   a principal in a collection principal GRPA contained by collection
   principal GRPB is a member of both GRPA and GRPB. Implementations not
   supporting recursive membership in principal collections can return
   an error if the client attempts to bind collection principals into
   other collection principals.

   Servers that support aggregation of principals (e.g. groups of users
   or other groups) MUST manifest them as collection principals. At
   minimum, principals and collection principals MUST support the
   OPTIONS and PROPFIND methods.

     Implementer's Note: Collection principals are first and foremost
     WebDAV collections. Therefore they contain resources as members.
     Since there is no requirement that all members of a collection
     principal need be principals, it is possible for a collection
     principal to have non-principals as members. When enumerating the
     principals-only membership of a collection principal, it is
     necessary to retrieve the DAV:resourcetype property and check it
     for the DAV:principal XML element (described in Section 4). If the
     DAV:principal XML element is not present, the resource is not a
     principal and may be ignored for the purposes of determining the
     principals-only membership of the collection principal.

     For example, the collection principal /FOO/ has two members, Bar
     and Baz. Bar is a principal but Baz is not. Therefore when
     determining which principals belong to the collection principal
     /FOO/, a client would enumerate the membership using PROPFIND
     while asking for the DAV:resourcetype property, and see that only
     Bar has the DAV:principal XML element. Therefore, only Bar is the
     only principal that is a member of the collection principal /FOO/.


3  PRIVILEGES

   Ability to perform a given method on a resource SHOULD be controlled
   by one or more privileges.  Authors of protocol extensions that
   define new HTTP methods SHOULD specify which privileges (by defining
   new privileges, or mapping to ones below) are required to perform the
   method.  A principal with no privileges to a resource SHOULD be
   denied any HTTP access to that resource, unless the principal matches


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   an ACE constructed using the DAV:all, DAV:authenticated, or
   DAV:unauthenticated pseudo-principals (see Section 5.4.1).

   Privileges may be containers of other privileges, in which case they
   are termed aggregate privileges.  If a principal is granted or denied
   an aggregate privilege, it is semantically equivalent to granting or
   denying each of the aggregated privileges individually.  For example,
   an implementation may define add-member and remove-member privileges
   that control the ability to add and remove an internal member of a
   collection.  Since these privileges control the ability to update the
   state of a collection, these privileges would be aggregated by the
   DAV:write privilege on a collection, and granting the DAV:write
   privilege on a collection would also grant the add-member and remove-
   member privileges.

   Privileges may have the quality of being abstract, in which case they
   cannot be set in an ACE. Aggregate and non-aggregate privileges are
   both capable of being abstract. Abstract privileges are useful for
   modeling privileges that otherwise would not be exposed via the
   protocol. Abstract privileges also provide server implementations
   with flexibility in implementing the privileges defined in this
   specification.  For example, if a server is incapable of separating
   the read resource capability from the read ACL capability, it can
   still model the DAV:read and DAV:read-acl privileges defined in this
   specification by declaring them abstract, and containing them within
   a non-abstract aggregate privilege (say, read-all) that holds
   DAV:read, and DAV:read-acl. In this way, it is possible to set the
   aggregate privilege, read-all, thus coupling the setting of DAV:read
   and DAV:read-acl, but it is not possible to set DAV:read, or
   DAV:read-acl individually. Since aggregate privileges can be
   abstract, it is also possible to use abstract privileges to group or
   organize non-abstract privileges. Privilege containment loops are not
   allowed, hence a privilege MUST NOT contain itself. For example,
   DAV:read cannot contain DAV:read.

   The set of privileges that apply to a particular resource may vary
   with the DAV:resourcetype of the resource, as well as between
   different server implementations.  To promote interoperability,
   however, this specification defines a set of well-known privileges
   (e.g. DAV:read, DAV:write, DAV:read-acl, DAV:write-acl, DAV:read-
   current-user-privilege-set, and DAV:all), which can at least be used
   to classify the other privileges defined on a particular resource.
   The access permissions on null resources (defined in [RFC2518],
   Section 3) are solely those they inherit (if any), and they are not
   discoverable (i.e., the access control properties specified in
   Section 5 are not defined on null resources). On the transition from
   null to stateful resource, the initial access control list is set by
   the server's default ACL value policy (if any).

   Server implementations MAY define new privileges beyond those defined
   in this specification. Privileges defined by individual

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   implementations MUST NOT use the DAV: namespace, and instead should
   use a namespace that they control, such as an http scheme URL.

3.1 DAV:read Privilege

   The read privilege controls methods that return information about the
   state of the resource, including the resource's properties. Affected
   methods include GET and PROPFIND.  Additionally, the read privilege
   MAY control the OPTIONS method.

     <!ELEMENT read EMPTY>

3.2 DAV:write Privilege

   The write privilege controls methods that modify the content, dead
   properties, or (in the case of a collection) membership of the
   resource, such as PUT and PROPPATCH.  Note that state modification is
   also controlled via locking (see section 5.3 of [WEBDAV]), so
   effective write access requires that both write privileges and write
   locking requirements are satisfied.

     <!ELEMENT write EMPTY>

3.3 DAV:read-acl Privilege

   The DAV:read-acl privilege controls the use of PROPFIND to retrieve
   the DAV:acl property of the resource.

     <!ELEMENT read-acl EMPTY>

3.4 DAV:read-current-user-privilege-set Privilege

   The DAV:read-current-user-privilege-set privilege controls the use of
   PROPFIND to retrieve the DAV:current-user-privilege-set property of
   the resource.

   Clients are intended to use this property to visually indicate in
   their UI items that are dependent on the permissions of a resource,
   for example, by graying out resources that are not writeable.

   This privilege is separate from DAV:read-acl because there is a need
   to allow most users access to the privileges permitted the current
   user (due to its use in creating the UI), while the full ACL contains
   information that may not be appropriate for the current authenticated
   user. As a result, the set of users who can view the full ACL is
   expected to be much smaller than those who can read the current user
   privilege set, and hence distinct privileges are needed for each.

     <!ELEMENT read-current-user-privilege-set EMPTY>



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3.5 DAV:write-acl Privilege

   The DAV:write-acl privilege controls use of the ACL method to modify
   the DAV:acl property of the resource.

     <!ELEMENT write-acl EMPTY>

3.6 DAV:all Privilege

   DAV:all is an aggregate privilege that contains the entire set of
   privileges that can be applied to the resource.

     <!ELEMENT all EMPTY>

3.7 Aggregation of Predefined Privileges

   Server implementations are free to aggregate the predefined
   privileges (defined above in Sections 3.1-3.6) subject to the
   following limitations:

   DAV:read-acl MUST NOT contain DAV:read, DAV:write, DAV:write-acl, or
   DAV:read-current-user-privilege-set.

   DAV:write-acl MUST NOT contain DAV:write, DAV:read, DAV:read-acl, or
   DAV:read-current-user-privilege-set.

   DAV:read-current-user-privilege-set MUST NOT contain DAV:write,
   DAV:read, DAV:read-acl, or DAV:write-acl.

   DAV:write MUST NOT contain DAV:read, DAV:read-acl, or DAV:read-
   current-user-privilege-set.

   DAV:read MUST NOT contain DAV:write, or DAV:write-acl.


4  PRINCIPAL PROPERTIES

   Principals are manifested to clients as a WebDAV resource, identified
   by a URL.  A principal MUST have a DAV:displayname property (defined
   in Section 13.2 of [RFC2518]), and a DAV:resourcetype property
   (defined in Section 13.9 of [RFC2518]).  Additionally, a principal
   MUST report the DAV:principal empty XML element in the value of the
   DAV:resourcetype property in addition to all other reported elements.
   For example, a collection principal would report DAV:collection and
   DAV:principal elements. The element type declaration for
   DAV:principal is:

     <!ELEMENT principal EMPTY>

   This protocol defines the following additional property for a
   principal. Since it is expensive, for many servers, to retrieve
   access control information, the name and value of this property

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   SHOULD NOT be returned by a PROPFIND allprop request (as defined in
   Section 12.14.1 of [RFC2518]).

4.1 DAV:alternate-URI-set

   This protected property, if non-empty, contains the URIs of network
   resources with additional descriptive information about the
   principal. This property identifies additional network resources
   (i.e., it contains one or more URIs) that may be consulted by a
   client to gain additional knowledge concerning a principal. One
   expected use for this property is the storage of an ldap [RFC2255]
   scheme URL. A user-agent encountering an ldap URL could use LDAP
   [RFC2589] to retrieve additional machine-readable directory
   information about the principal, and display that information in its
   user interface. Support for this property is REQUIRED, and the value
   is empty if no alternate URI exists for the principal.

     <!ELEMENT alternate-URI-set (href*)>

4.2 DAV:principal-URL

    This protected property contains the URL that MUST be used to
   identify this principal in an ACL request.

     <!ELEMENT principal-URL (href)>


5  ACCESS CONTROL PROPERTIES

   This specification defines a number of new properties for WebDAV
   resources.  Access control properties may be retrieved just like
   other WebDAV properties, using the PROPFIND method.   Since it is
   expensive, for many servers, to retrieve access control information,
   a PROPFIND allprop request (as defined in Section 12.14.1 of
   [RFC2518]) SHOULD NOT return the names and values of the properties
   defined in this section.

   HTTP resources that support the WebDAV Access Control Protocol MUST
   contain the following properties. Null resources (described in
   Section 3 of [RFC2518]) MUST NOT contain the following properties:

5.1 DAV:owner

   This protected property identifies a particular principal as being
   the "owner" of the resource. Since the owner of a resource often has
   special access control capabilities (e.g., the owner frequently has
   permanent DAV:write-acl privilege), clients might display the
   resource owner in their user interface.

     <!ELEMENT owner (href)>

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5.1.1 Example: Retrieving DAV:owner

   This example shows a client request for the value of the DAV:owner
   property from a collection resource with URL
   http://www.webdav.org/papers/. The principal making the request is
   authenticated using Digest authentication. The value of DAV:owner is
   the URL http://www.webdav.org/_acl/users/gstein, wrapped in the
   DAV:href XML element.

     >> Request <<

     PROPFIND /papers/ HTTP/1.1
     Host: www.webdav.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="jim",
        realm="jim@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
       <D:prop>
         <D:owner/>
       </D:prop>
     </D:propfind>

     >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
        <D:response>
           <D:href>http://www.webdav.org/papers/</D:href>
           <D:propstat>
              <D:prop>
                 <D:owner>
     <D:href>http://www.webdav.org/_acl/users/gstein</D:href>
                 </D:owner>
              </D:prop>
              <D:status>HTTP/1.1 200 OK</D:status>
           </D:propstat>
        </D:response>
     </D:multistatus>



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5.1.2 Example: An Attempt to Set DAV:owner

   The following example shows a client request to modify the value of
   the DAV:owner property on the resource with URL
   http://www.webdav.org/papers/. Since DAV:owner is a protected
   property, the server responds with a 207 (Multi-Status) response that
   contains a 403 (Forbidden) status code for the act of setting
   DAV:owner. Section 8.2.1 of [RFC2518] describes PROPPATCH status code
   information, and Section 11 of [RFC2518] describes the Multi-Status
   response.

     >> Request <<

     PROPPATCH /papers/ HTTP/1.1
     Host: www.webdav.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="jim",
        realm="jim@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propertyupdate xmlns:D="DAV:">
        <D:set>
           <D:prop>
              <D:owner>
                 <D:href>http://www.webdav.org/_acl/users/jim</D:href>
              </D:owner>
           </D:prop>
        </D:set>
     </D:propertyupdate>


     >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
        <D:response>
           <D:href>http://www.webdav.org/papers/</D:href>
           <D:propstat>
              <D:prop><D:owner/></D:prop>
              <D:status>HTTP/1.1 403 Forbidden</D:status>
              <D:responsedescription>Failure to set protected property
     (DAV:owner)
              </D:responsedescription>
           </D:propstat>

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        </D:response>
     </D:multistatus>


5.2 DAV:supported-privilege-set

     This is a protected property that identifies the privileges defined
     for the resource.
     <!ELEMENT supported-privilege-set (supported-privilege*)>

     Each privilege appears as an XML element, where aggregate
     privileges list as sub-elements all of the privileges that they
     aggregate.
     <!ELEMENT supported-privilege (privilege, abstract?, description,
     supported-privilege*)>
     <!ELEMENT privilege ANY>

   An abstract privilege MUST NOT be used in an ACE for that resource.
   Servers MUST fail an attempt to set an abstract privilege.

     <!ELEMENT abstract EMPTY>

   A description is a human-readable description of what this privilege
   controls access to. Servers MUST indicate the human language of the
   description using the xml:lang attribute and SHOULD consider the HTTP
   Accept-Language request header when selecting one of multiple
   available languages.

     <!ELEMENT description #PCDATA>

   It is envisioned that a WebDAV ACL-aware administrative client would
   list the supported privileges in a dialog box, and allow the user to
   choose non-abstract privileges to apply in an ACE.  The privileges
   tree is useful programmatically to map well-known privileges (defined
   by WebDAV or other standards groups) into privileges that are
   supported by any particular server implementation.  The privilege
   tree also serves to hide complexity in implementations allowing large
   number of privileges to be defined by displaying aggregates to the
   user.

5.2.1 Example: Retrieving a List of Privileges Supported on a Resource

   This example shows a client request for the DAV:supported-privilege-
   set property on the resource http://www.webdav.org/papers/. The value
   of the DAV:supported-privilege-set property is a tree of supported
   privileges:

       DAV:all (aggregate, abstract)
           |
           +-- DAV:read (aggregate)

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                  |
                  +-- DAV:read-acl (abstract)
                  +-- DAV:read-current-user-privilege-set (abstract)
           +-- DAV:write (aggregate)
                  |
                  +-- DAV:write-acl (abstract)


   This privilege tree is not normative, and many possible privilege
   trees are possible.


     >> Request <<

     PROPFIND /papers/ HTTP/1.1
     Host: www.webdav.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="gclemm",
        realm="gclemm@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
       <D:prop>
         <D:supported-privilege-set/>
       </D:prop>
     </D:propfind>

     >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/papers/</D:href>
         <D:propstat>
           <D:prop>
             <D:supported-privilege-set>
               <D:supported-privilege>
                 <D:privilege> <D:all/> </D:privilege>
                 <D:abstract/>
                 <D:description xml:lang="en">Any
     operation</D:description>
                 <D:supported-privilege>
                   <D:privilege> <D:read/> </D:privilege>

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                   <D:description xml:lang="en">Read any
     object</D:description>
                   <D:supported-privilege>
                     <D:privilege> <D:read-acl/> </D:privilege>
                     <D:abstract/>
                     <D:description xml:lang="en">Read
     ACL</D:description>
                   </D:supported-privilege>
                 </D:supported-privilege>
                   <D:supported-privilege>
                     <D:privilege>
                       <D:read-current-user-privilege-set/>
                     </D:privilege>
                     <D:abstract/>
                     <D:description xml:lang="en">Read current user
     privilege set property</D:description>
                   </D:supported-privilege>
                 <D:supported-privilege>
                   <D:privilege> <D:write/> </D:privilege>
                   <D:description xml:lang="en">Write any
     object</D:description>
                   <D:supported-privilege>
                     <D:privilege> <D:write-acl/> </D:privilege>
                     <D:description xml:lang="en">Write
     ACL</D:description>
                     <D:abstract/>
                   </D:supported-privilege>
                 </D:supported-privilege>
               </D:supported-privilege>
             </D:supported-privilege-set>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>

5.3 DAV:current-user-privilege-set

   DAV:current-user-privilege-set is a protected property containing the
   exact set of privileges (as computed by the server) granted to the
   currently authenticated HTTP user. Aggregate privileges and their
   contained privileges are listed. A user-agent can use the value of
   this property to adjust its user interface to make actions
   inaccessible (e.g., by graying out a menu item or button) for which
   the current principal does not have permission. This is particularly
   useful for an access control user interface, which can be constructed
   without knowing the ACE combining semantics of the server. This
   property is also useful for determining what operations the current
   principal can perform, without having to actually execute an
   operation.

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     <!ELEMENT current-user-privilege-set (privilege*)>
     <!ELEMENT privilege ANY>

   If the current user is granted a specific privilege, that privilege
   must belong to the set of privileges that may be set on this
   resource. Therefore, each element in the DAV:current-user-privilege-
   set property MUST identify a non-abstract privilege from the
   DAV:supported-privilege-set property.

5.3.1 Example: Retrieving the UserÆs Current Set of Assigned Privileges

   Continuing the example from Section 5.2.1, this example shows a
   client requesting the DAV:current-user-privilege-set property from
   the resource with URL http://www.webdav.org/papers/. The username of
   the principal making the request is ôkhare", and Digest
   authentication is used in the request. The principal with username
   ôkhare" has been granted the DAV:read privilege. Since the DAV:read
   privilege contains the DAV:read-acl and DAV:read-current-user-
   privilege-set privileges (see Section 5.2.1), the principal with
   username ôkhare" can read the ACL property, and the DAV:current-user-
   privilege-set property. However, the DAV:all, DAV:read-acl,
   DAV:write-acl and DAV:read-current-user-privilege-set privileges are
   not listed in the value of DAV:current-user-privilege-set, since (for
   this example) they are abstract privileges. DAV:write is not listed
   since the principal with username ôkhare" is not listed in an ACE
   granting that principal write permission.

     >> Request <<

     PROPFIND /papers/ HTTP/1.1
     Host: www.webdav.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="khare",
        realm="khare@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
       <D:prop>
         <D:current-user-privilege-set/>
       </D:prop>
     </D:propfind>


     >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

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     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/papers/</D:href>
         <D:propstat>
           <D:prop>
             <D:current-user-privilege-set>
               <D:privilege> <D:read/> </D:privilege>
             </D:current-user-privilege-set>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>

5.4 DAV:acl

   This is a protected property that specifies the list of access
   control entries (ACEs), which define what principals are to get what
   privileges for this resource.

     <!ELEMENT acl (ace*)>

   Each DAV:ace element specifies the set of privileges to be either
   granted or denied to a single principal.  If the DAV:acl property is
   empty, no principal is granted any privilege.

     <!ELEMENT ace (principal, (grant|deny), protected?, inherited?)>

5.4.1 ACE Principal

   The DAV:principal element identifies the principal to which this ACE
   applies.

     <!ELEMENT principal ((href)
      | all | authenticated | unauthenticated
      | property | self)>

   The current user matches DAV:href only if that user is authenticated
   as being (or being a member of) the principal identified by the URL
   contained by that DAV:href.

   The current user always matches DAV:all.

     <!ELEMENT all EMPTY>

   The current user matches DAV:authenticated only if authenticated.

     <!ELEMENT authenticated EMPTY>

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   The current user matches DAV:unauthenticated only if not
   authenticated.

     <!ELEMENT unauthenticated EMPTY>

   DAV:all is the union of DAV:authenticated, and DAV:unauthenticated.
   For a given request, the user matches either DAV:authenticated, or
   DAV:unauthenticated, but not both (that is, DAV:authenticated and
   DAV:unauthenticated are disjoint sets).

   The current user matches a DAV:property principal in a DAV:acl
   property of a resource only if the value of the identified property
   of that resource contains at most one DAV:href XML element, the URI
   value of DAV:href identifies a principal, and the current user is
   authenticated as being (or being a member of) that principal.  For
   example, if the DAV:property element contained <DAV:owner/>, the
   current user would match the DAV:property principal only if the
   current user is authenticated as matching the principal identified by
   the DAV:owner property of the resource.

     <!ELEMENT property ANY>

   The current user matches DAV:self in a DAV:acl property of the
   resource only if that resource is a principal object and the current
   user is authenticated as being that principal or a member of that
   principal collection.

     <!ELEMENT self EMPTY>

5.4.2 ACE Grant and Deny

   Each DAV:grant or DAV:deny element specifies the set of privileges to
   be either granted or denied to the specified principal.  A DAV:grant
   or DAV:deny element of the DAV:acl of a resource MUST only contain
   non-abstract elements specified in the DAV:supported-privilege-set of
   that resource.

     <!ELEMENT grant (privilege+)>
     <!ELEMENT deny (privilege+)>
     <!ELEMENT privilege ANY>

5.4.3 ACE Protection

   A server indicates an ACE is protected by including the DAV:protected
   element in the ACE. If the ACL of a resource contains an ACE with a
   DAV:protected element, an attempt to remove that ACE from the ACL
   MUST fail..

     <!ELEMENT protected EMPTY>



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5.4.4 ACE Inheritance

   The presence of a DAV:inherited element indicates that this ACE is
   inherited from another resource that is identified by the URL
   contained in a DAV:href element.  An inherited ACE cannot be modified
   directly, but instead the ACL on the resource from which it is
   inherited must be modified.

   Note that ACE inheritance is not the same as ACL initialization.  ACL
   initialization defines the ACL that a newly created resource will use
   (if not specified).  ACE inheritance refers to an ACE that is
   logically shared - where an update to the resource containing an ACE
   will affect the ACE of each resource that inherits that ACE.  The
   method by which ACLs are initialized or by which ACEs are inherited
   is not defined by this document.

     <!ELEMENT inherited (href)>

5.4.5 Example: Retrieving a ResourceÆs Access Control List

   Continuing the example from Sections 5.2.1 and 5.3.1, this example
   shows a client requesting the DAV:acl property from the resource with
   URL http://www.webdav.org/papers/. There are two ACEs defined in this
   ACL:

   ACE #1: The principal collection identified by URL
   http://www.webdav.org/_acl/groups/maintainers/ (the group of site
   maintainers) is granted DAV:write privilege. Since (for this example)
   DAV:write contains the DAV:write-acl privilege (see Section 5.2.1),
   this means the ômaintainers" group can also modify the access control
   list.

   ACE #2: All principals (DAV:all) are granted the DAV:read privilege.
   Since (for this example) DAV:read contains DAV:read-acl and DAV:read-
   current-user-privilege-set, this means all users (including all
   members of the ômaintainers" group) can read the DAV:acl property and
   the DAV:current-user-privilege-set property.


     >> Request <<

     PROPFIND /papers/ HTTP/1.1
     Host: www.webdav.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="masinter",
        realm="masinter@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>

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     <D:propfind xmlns:D="DAV:">
       <D:prop>
         <D:acl/>
       </D:prop>
     </D:propfind>


     >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/papers/</D:href>
         <D:propstat>

           <D:prop>
             <D:acl>
               <D:ace>
                 <D:principal>
                   <D:href>
                     http://www.webdav.org/_acl/groups/maintainers/
                   </D:href>
                 </D:principal>
                 <D:grant>
                   <D:privilege> <D:write/> </D:privilege>
                 </D:grant>
               </D:ace>
               <D:ace>
                 <D:principal>
                   <D:all/>
                 </D:principal>
                 <D:grant>
                   <D:privilege> <D:read/> </D:privilege>
                 </D:grant>
               </D:ace>
             </D:acl>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>


5.5 DAV:acl-semantics

   This is a protected property that defines the ACL semantics.  These
   semantics define how multiple ACEs that match the current user are

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   combined, what are the constraints on how ACEs can be ordered, and
   which principals must have an ACE. A client user interface could use
   the value of this property to provide feedback to a human operator
   concerning the impact of proposed changes to an ACL. Alternately, a
   client can use this property to help it determine, before submitting
   an ACL method invocation, what ACL changes it needs to make to
   accomplish a specific goal (or whether that goal is even achievable
   on this server).

   Since it is not practical to require all implementations to use the
   same ACL semantics, the DAV:acl-semantics property is used to
   identify the ACL semantics for a particular resource.  The DAV:acl-
   semantics element is defined in Section 6.

5.5.1 Example: Retrieving DAV:acl-semantics

   In this example, the client requests the value of the DAV:acl-
   semantics property. Digest authentication provides credentials for
   the principal operating the client. In this example, the ACE
   combination semantics are DAV:first-match, described in Section
   6.1.1, the ACE ordering semantics are not specified (some value other
   than DAV:deny-before-grant, described in Section 6.2.1), the
   DAV:allowed-ace element states that only one ACE is permitted for
   each principal, and an ACE describing the privileges granted the
   DAV:all principal must exist in every ACL.



     >> Request <<

     PROPFIND /papers/ HTTP/1.1
     Host: www.webdav.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="srcarter",
        realm="srcarter@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
       <D:prop>
         <D:acl-semantics/>
       </D:prop>
     </D:propfind>


     >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"

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     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/papers/</D:href>
         <D:propstat>
           <D:prop>
             <D:acl-semantics>
               <D:ace-combination>
                 <D:first-match/>
               </D:ace-combination>
               <D:ace-ordering/>
            <D:allowed-ace>
                 <D:principal-only-one-ace/>
               </D:allowed-ace>
               <D:required-principal>
                 <D:all/>
               </D:required-principal>
             </D:acl-semantics>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       <D:response>
     </D:multistatus>


5.6 DAV:principal-collection-set

   This protected property contains zero, one, or more URLs that
   identify a collection principal. It is expected that implementations
   of this protocol will typically use a relatively small number of
   locations in the URL namespace for principals, and collection
   principals. In cases where this assumption holds, the DAV:principal-
   collection-set property will contain a small set of URLs identifying
   the top of a collection hierarchy containing multiple principals and
   collection principals. An access control protocol user agent could
   use the contents of DAV:principal-collection-set to retrieve the
   DAV:displayname property (specified in Section 13.2 of [RFC2518]) of
   all principals on that server, thereby yielding human-readable names
   for each principal that could be displayed in a user interface.

     <!ELEMENT principal-collection-set (href*)>
   Since different servers can control different parts of the URL
   namespace, different resources on the same host MAY have different
   DAV:principal-collection-set values. The collections specified in the
   DAV:principal-collection-set MAY be located on different hosts from
   the resource. The URLs in DAV:principal-collection-set SHOULD be http
   or https scheme URLs. For security and scalability reasons, a server
   MAY report only a subset of the entire set of known collection

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   principals, and therefore clients should not assume they have
   retrieved an exhaustive listing. Additionally, a server MAY elect to
   report none of the collection principals it knows about, in which
   case the property value would be empty.

   The value of DAV:principal-collection-set gives the scope of the
   DAV:principal-property-search REPORT (defined in Section 9.4).
   Clients use the DAV:principal-property-search REPORT to populate
   their user interface with a list of principals. Therefore, servers
   that limit a client's ability to obtain principal information will
   interfere with the client's ability to manipulate access control
   lists, due to the difficulty of getting the URL of a principal for
   use in an ACE.

5.6.1 Example: Retrieving DAV:principal-collection-set

   In this example, the client requests the value of the DAV:principal-
   collection-set property on the collection resource identified by URL
   http://www.webdav.org/papers/. The property contains the two URLs,
   http://www.webdav.org/_acl/users/ and
   http://www.webdav.org/_acl/groups/, both wrapped in <DAV:href> XML
   elements. Digest authentication provides credentials for the
   principal operating the client.

   The client might reasonably follow this request with two separate
   PROPFIND requests to retrieve the DAV:displayname property of the
   members of the two collections (/_acl/users/ and /_acl_groups/). This
   information could be used when displaying a user interface for
   creating access control entries.


     >> Request <<

     PROPFIND /papers/ HTTP/1.1
     Host: www.webdav.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="yarong",
        realm="yarong@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
       <D:prop>
         <D:principal-collection-set/>
       </D:prop>
     </D:propfind>


     >> Response <<

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     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/papers/</D:href>
         <D:propstat>
           <D:prop>
             <D:principal-collection-set>
               <D:href>
                 http://www.webdav.org/_acl/users/
               </D:href>
               <D:href>
                 http://www.webdav.org/_acl/groups/
               </D:href>
             </D:principal-collection-set>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>

5.7 Example: PROPFIND to retrieve access control properties

   The following example shows how access control information can be
   retrieved by using the PROPFIND method to fetch the values of the
   DAV:owner, DAV:supported-privilege-set, DAV:current-user-privilege-
   set, and DAV:acl properties.

     >> Request <<

     PROPFIND /top/container/ HTTP/1.1
     Host: www.foo.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="ejw",
        realm="users@foo.org", nonce="...",
        uri="/top/container/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:propfind xmlns:D="DAV:">
       <D:prop>
         <D:owner/>
         <D:supported-privilege-set/>
         <D:current-user-privilege-set/>
         <D:acl/>
       </D:prop>

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     </D:propfind>

     >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus
        xmlns:D="DAV:"
        xmlns:A="http://www.webdav.org/acl/"> <D:response>
       <D:href>http://www.foo.org/top/container/</D:href>
       <D:propstat>
       <D:prop>
         <D:owner>
           <D:href>http://www.foo.org/users/gclemm</D:href> </D:owner>
         <D:supported-privilege-set>
           <D:supported-privilege>
             <D:privilege> <D:all/> </D:privilege>
             <D:abstract/>
             <D:description xml:lang="en">Any operation</D:description>
             <D:supported-privilege>
               <D:privilege> <D:read/> </D:privilege>
               <D:description xml:lang="en">Read any
     object</D:description>
             </D:supported-privilege>
             <D:supported-privilege>
               <D:privilege> <D:write/> </D:privilege>
               <D:abstract/>
               <D:description xml:lang="en">Write any
     object</D:description>
               <D:supported-privilege>
                 <D:privilege> <A:create/> </D:privilege>
                 <D:description xml:lang="en">Create an
     object</D:description>
               </D:supported-privilege>
               <D:supported-privilege>
                 <D:privilege> <A:update/> </D:privilege>
                 <D:description xml:lang="en">Update an
     object</D:description>
               </D:supported-privilege>
               <D:supported-privilege>
                 <D:privilege> <A:delete/> </D:privilege>
                 <D:description xml:lang="en">Delete an
     object</D:description>
               </D:supported-privilege>
             </D:supported-privilege>
             <D:supported-privilege>
               <D:privilege> <D:read-acl/> </D:privilege>
               <D:description xml:lang="en">Read the ACL</D:description>

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             </D:supported-privilege>
             <D:supported-privilege>
               <D:privilege> <D:write-acl/> </D:privilege>
               <D:description xml:lang="en">Write the
     ACL</D:description>
             </D:supported-privilege>
           </D:supported-privilege>
         </D:supported-privilege-set>
         <D:current-user-privilege-set>
           <D:privilege> <D:read/> </D:privilege>
           <D:privilege> <D:read-acl/> </D:privilege>
         </D:current-user-privilege-set>
         <D:acl>
           <D:ace>
             <D:principal>
               <D:href>http://www.foo.org/users/esedlar</D:href>
               </D:principal>
             <D:grant>
               <D:privilege> <D:read/> </D:privilege>
               <D:privilege> <D:write/> </D:privilege>
               <D:privilege> <D:read-acl/> </D:privilege> </D:grant>
           </D:ace>
           <D:ace>
             <D:principal>
               <D:href>http://www.foo.org/groups/marketing/</D:href>
             </D:principal>
             <D:deny>
               <D:privilege> <D:read/> </D:privilege> </D:deny>
           </D:ace>
           <D:ace>
             <D:principal>
               <D:property> <D:owner/> </D:property> </D:principal>
             <D:grant>
               <D:privilege> <D:read-acl/> </D:privilege>
               <D:privilege> <D:write-acl/> </D:privilege> </D:grant>
           </D:ace>
           <D:ace>
             <D:principal> <D:all/> </D:principal>
             <D:grant>
               <D:privilege> <D:read/> </D:privilege></D:grant>
             <D:inherited>
               <D:href>http://www.foo.org/top/</D:href> </D:inherited>
           </D:ace> </D:acl>
         </D:prop>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:propstat> </D:response> </D:multistatus>


   The value of the DAV:owner property is a single DAV:href XML element
   containing the URL of the principal that owns this resource.

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   The value of the DAV:supported-privilege-set property is a tree of
   supported privileges:

       DAV:all (aggregate, abstract)
           |
         +-- DAV:read
         +-- DAV:write (aggregate, abstract)
              |
              +-- http://www.webdav.org/acl/create
              +-- http://www.webdav.org/acl/update
              +-- http://www.webdav.org/acl/delete
           +-- DAV:read-acl
           +-- DAV:write-acl


   The DAV:current-user-privilege-set property contains two privileges,
   DAV:read, and DAV:read-acl. This indicates that the current
   authenticated user only has the ability to read the resource, and
   read the DAV:acl property on the resource.

   The DAV:acl property contains a set of four ACEs:

   ACE #1: The principal identified by the URL
   http://www.foo.org/users/esedlar is granted the DAV:read, DAV:write,
   and DAV:read-acl privileges.

   ACE #2: The principals identified by the URL
   http://www.foo.org/groups/marketing/ are denied the DAV:read
   privilege.  In this example, the principal URL identifies a group,
   which is represented by a collection principal.

   ACE #3: In this ACE, the principal is a property principal,
   specifically the DAV:owner property. When evaluating this ACE, the
   value of the DAV:owner property is retrieved, and is examined to see
   if it contains a DAV:href XML element. If so, the URL within the
   DAV:href element is read, and identifies a principal. In this ACE,
   the owner is granted DAV:read-acl, and DAV:write-acl privileges.

   ACE #4: This ACE grants the DAV:all principal (all users) the
   DAV:read privilege. This ACE is inherited from the resource
   http://www.foo.org/top/, the parent collection of this resource.


6  ACL SEMANTICS

   The ACL semantics define how multiple ACEs that match the current
   user are combined, what are the constraints on how ACEs can be
   ordered, and which principals must have an ACE.

     <!ELEMENT acl-semantics (ace-combination?, ace-ordering?, allowed-
     ace?, required-principal?)>

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6.1 ACE Combination

   The DAV:ace-combination element defines how privileges from multiple
   ACEs that match the current user will be combined to determine the
   access privileges for that user.  Multiple ACEs may match the same
   user because the same principal can appear in multiple ACEs, because
   multiple principals can identify the same user, and because one
   principal can be a member of another principal.

     <!ELEMENT ace-combination
      (first-match | all-grant-before-any-deny | specific-deny-
     overrides-grant)>

6.1.1 DAV:first-match ACE Combination

   The ACEs are evaluated in the order in which they appear in the ACL.
   If the first ACE that matches the current user does not grant all the
   privileges needed for the request, the request MUST fail.

     <!ELEMENT first-match EMPTY>

6.1.2 DAV:all-grant-before-any-deny ACE Combination

   The ACEs are evaluated in the order in which they appear in the ACL.
   If an evaluated ACE denies a privilege needed for the request, the
   request MUST fail.  If all ACEs have been evaluated without the user
   being granted all privileges needed for the request, the request MUST
   fail.

     <!ELEMENT all-grant-before-any-deny EMPTY>

6.1.3 DAV:specific-deny-overrides-grant ACE Combination

   All ACEs in the ACL are evaluated.  An "individual ACE" is one whose
   principal identifies the current user.  A "group ACE" is one whose
   principal is a collection that contains a principal that identifies
   the current user.  A privilege is granted if it is granted by an
   individual ACE and not denied by an individual ACE, or if it is
   granted by a group ACE and not denied by an individual or group ACE.
   A request MUST fail if any of its needed privileges are not granted.

     <!ELEMENT specific-deny-overrides-grant EMPTY>

6.2 ACE Ordering

   The DAV:ace-ordering element defines a constraint on how the ACEs can
   be ordered in the ACL.

     <!ELEMENT ace-ordering (deny-before-grant)? >



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6.2.1 DAV:deny-before-grant ACE Ordering

   This element indicates that all deny ACEs must precede all grant
   ACEs.

     <!ELEMENT deny-before-grant EMPTY>

6.3 Allowed ACE

   The DAV:allowed-ace XML element specifies constraints on what kinds
   of ACEs are allowed in an ACL.

     <!ELEMENT allowed-ace (principal-only-one-ace | grant-only)*>

6.3.1 DAV:principal-only-one-ace ACE Constraint

   This element indicates that a principal can appear in only one ACE
   per resource.

     <!ELEMENT principal-only-one-ace EMPTY>

6.3.2 DAV:grant-only ACE Constraint

   This element indicates that ACEs with deny clauses are not allowed.

     <!ELEMENT grant-only EMPTY>

6.4 Required Principals

   The required principal elements identify which principals must have
   an ACE defined in the ACL.

     <!ELEMENT required-principal
       (all? | authenticated? | unauthenticated? | self? | href* |
     property*)>

   For example, the following element requires that the ACL contain a
   DAV:owner property ACE:

     <D:required-principal xmlns:D="DAV:">
       <D:property> <D:owner/> </D:property>
     </D:required-principal>


7  ACCESS CONTROL AND EXISTING METHODS

   This section defines the impact of access control functionality on
   existing methods.




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7.1 OPTIONS

   If the server supports access control, it MUST return "access-
   control" as a field in the DAV response header from an OPTIONS
   request on any resource implemented by that server.

7.1.1 Example - OPTIONS

     >> Request <<

       OPTIONS /foo.html HTTP/1.1
       Host: www.webdav.org
       Content-Length: 0

     >> Response <<

       HTTP/1.1 200 OK
       DAV: 1, 2, access-control
       Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL

   In this example, the OPTIONS response indicates that the server
   supports access control and that /foo.html can have its access
   control list modified by the ACL method.

7.2 MOVE

   When a resource is moved from one location to another due to a MOVE
   request, the non-inherited and non-protected ACEs in the DAV:acl
   property of the resource MUST NOT be modified, or the MOVE request
   fails. Handling of inherited and protected ACEs is intentionally
   undefined to give server implementations flexibility in how they
   implement ACE inheritance and protection.

7.3 COPY

   The DAV:acl property on the resource at the destination of a COPY
   MUST be the same as if the resource was created by an individual
   resource creation request (e.g. MKCOL, PUT). Clients wishing to
   preserve the DAV:acl property across a copy need to read the DAV:acl
   property prior to the COPY, then perform an ACL operation on the new
   resource at the destination to restore, insofar as this is possible,
   the original access control list.

7.4 DELETE

   The precise combination of privileges and resources necessary to
   permit the DELETE method is intentionally left to the discretion of
   each server implementation. It is envisioned that on some servers,
   DELETE will require write permission on the collection containing the
   resource to be deleted.  On other servers, it might also require
   write permission on the resource being deleted.

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7.5 LOCK

   A lock on a resource ensures that only the lock owner can modify ACEs
   that are not inherited and not protected  (these are the only ACEs
   that a client can modify with an ACL request). A lock does not
   protect inherited or protected ACEs, since a client cannot modify
   them with an ACL request on that resource.


8  ACCESS CONTROL METHODS

8.1 ACL

   The ACL method modifies the access control list (which can be read
   via the DAV:acl property) of a resource.  Specifically, the ACL
   method only permits modification to ACEs that are not inherited, and
   are not protected. An ACL method invocation modifies all non-
   inherited and non-protected ACEs in a resourceÆs access control list
   to exactly match the ACEs contained within in the DAV:acl XML element
   (specified in Section 5.4) of the request body. An ACL request body
   MUST contain only one DAV:acl XML element. Unless the non-inherited
   and non-protected ACEs of the DAV:acl property of the resource can be
   updated to be exactly the value specified in the ACL request, the ACL
   request MUST fail.

   It is possible that the ACEs visible to the current user in the
   DAV:acl property may only be a portion of the complete set of ACEs on
   that resource. If this is the case, an ACL request only modifies the
   set of ACEs visible to the current user, and does not affect any non-
   visible ACE.

   In order to avoid overwriting DAV:acl changes by another client, a
   client SHOULD acquire a WebDAV lock on the resource before retrieving
   the DAV:acl property of a resource that it intends on updating.

     Implementation Note: Two common operations are to add or remove an
     ACE from an existing access control list. To accomplish this, a
     client uses the PROPFIND method to retrieve the value of the
     DAV:acl property, then parses the returned access control list to
     remove all inherited and protected ACEs (these ACEs are tagged
     with the DAV:inherited and DAV:protected XML elements). In the
     remaining set of non-inherited, non-protected ACEs, the client can
     add or remove one or more ACEs before submitting the final ACE set
     in the request body of the ACL method.

8.1.1 ACL Preconditions

   An implementation MAY enforce one or more of the following
   constraints on an ACL request.  If the constraint is violated, a 403
   (Forbidden) response MUST be returned and the indicated XML element
   MUST be returned as the top level element in an XML response body.

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   <DAV:ace-conflict/>: A conflict exists between two or more ACEs
   submitted in the ACL request.

   <DAV:protected-ace-conflict/>: A conflict exists between an ACE in
   the ACL request and a protected ACE on the resource. For example, if
   the resource has a protected ACE granting DAV:write to a given
   principal, then it would be a protected ACE conflict if the ACL
   request submitted an ACE denying DAV:write to the same principal.

   <DAV:inherited-ace-conflict/>: A conflict exists between an ACE in
   the ACL request and an inherited ACE on the resource. For example, if
   the resource inherits an ACE from its parent collection granting
   DAV:write to a given principal, then it would be an inherited ACE
   conflict if the ACL request submitted an ACE denying DAV:write to the
   same principal. Note that reporting of this error will be
   implementation-dependent. Implementations have the choice to either
   report this error, or to allow the ACE to be set, and then let normal
   ACE evaluation rules determine whether the new ACE has any impact on
   the privileges available to a specific principal.

   <DAV:too-many-aces/>: An implementation MAY limit the number of ACEs
   in an ACL.  However, ACL-compliant servers MUST support at least one
   ACE granting privileges to a single principal, and one ACE granting
   privileges to a collection principal.

   <DAV:deny-before-grant/>: All non-inherited deny ACEs MUST precede
   all non-inherited grant ACEs.

   <DAV:principal-only-one-ace/>: For implementations that have the
   DAV:principal-only-one-ace constraint (defined in Section 6.3.1),
   this XML element indicates that fulfilling the ACL request would
   result in multiple ACEs for one or more principals.

   <DAV:grant-only/>: For implementations that have the DAV:grant-only
   constraint (defined in Section 6.3.2), this XML element indicates the
   request contained one or more deny ACEs.

   <DAV:no-abstract/>: The ACL request attempts to set an abstract
   privilege in an ACE (see Section 5.2).

   <DAV:supported-privilege/>: One or more of the privileges in the ACL
   request is not supported by the resource.

   <DAV:required-principal/>: One or more required principals (see
   Section 6.4) would not be present in the access control list after
   processing the ACL request. The DAV:required-principal XML element
   MUST contain a list of the missing principal(s), following the syntax
   specified in Section 6.4.

   <DAV:recognized-principal/>: One or more of the principal URLs in the
   ACL request does not identify a principal resource.


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   <DAV:allowed-principal/>: One or more of the principal URLs in the
   ACL request is not allowed in an ACE. For example, a server where
   only authenticated principals can access resources would not allow
   the DAV:all or DAV:unauthenticated principals to be used in an ACE,
   since these would allow unauthenticated access to resources.

8.1.2 Example: the ACL method

   In the following example, user "fielding", authenticated by
   information in the Authorization header, grants the principal
   identified by the URL http://www.foo.org/users/esedlar  (i.e., the
   user "esedlar") read and write privileges, grants the owner of the
   resource read-acl and write-acl privileges, and grants everyone read
   privileges.

     >> Request <<

     ACL /top/container/ HTTP/1.1
     Host: www.foo.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx
     Authorization: Digest username="fielding",
        realm="users@foo.org", nonce="...",
        uri="/top/container/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:acl xmlns:D="DAV:">
       <D:ace>
         <D:principal>
           <D:href>http://www.foo.org/users/esedlar</D:href>
         </D:principal>
         <D:grant>
           <D:privilege> <D:read/> </D:privilege>
           <D:privilege> <D:write/> </D:privilege>
         </D:grant>
       </D:ace>
       <D:ace>
         <D:principal>
           <D:property> <D:owner/> </D:property>
         </D:principal>
         <D:grant>
           <D:privilege> <D:read-acl/> </D:privilege>
           <D:privilege> <D:write-acl/> </D:privilege>
         </D:grant>
       </D:ace>
       <D:ace>
         <D:principal> <D:all/> </D:principal>
         <D:grant>
           <D:privilege> <D:read/> </D:privilege>
         </D:grant>
       </D:ace>

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     </D:acl>

     >> Response <<

     HTTP/1.1 200 OK

8.1.3 Example: ACL method failure due to protected ACE conflict

   In the following request, user "fielding", authenticated by
   information in the Authorization header, attempts to deny the
   principal identified by the URL http://www.foo.org/users/esedlar
   (i.e., the user "esedlar") write privileges. Prior to the request,
   the DAV:acl property on the resource contained a protected ACE (see
   Section 5.4.3) granting DAV:owner the DAV:read and DAV:write
   privileges. The principal identified by URL
   http://www.foo.org/users/esedlar is the owner of the resource. The
   ACL method invocation fails because the submitted ACE conflicts with
   the protected ACE, thus violating the semantics of ACE protection.

     >> Request <<

     ACL /top/container/ HTTP/1.1
     Host: www.foo.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx
     Authorization: Digest username="fielding",
        realm="users@foo.org", nonce="...",
        uri="/top/container/", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:acl xmlns:D="DAV:">
       <D:ace>
         <D:principal>
           <D:href>http://www.foo.org/users/esedlar</D:href>
         </D:principal>
         <D:deny>
           <D:privilege> <D:write/> </D:privilege>
         </D:deny>
       </D:ace>
     </D:acl>

     >> Response <<

     HTTP/1.1 403 Forbidden
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:protected-ace-conflict xmlns:D="DAV:"/>


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8.1.4 Example: ACL method failure due to an inherited ACE conflict

   In the following request, user "ejw", authenticated by information in
   the Authorization header, tries to change the access control list on
   the resource http://www.foo.org/top/index.html. This resource has two
   inherited ACEs.

   Inherited ACE #1 grants the principal identified by URL
   http://www.foo.org/users/ejw (i.e., the user "ejw")
   http://www.foo.org/privs/write-all and DAV:read-acl privileges. On
   this server, http://www.foo.org/privs/write-all is an aggregate
   privilege containing DAV:write, and DAV:write-acl.

   Inherited ACE #2 grants principal DAV:all the DAV:read privilege.

   The request attempts to set a (non-inherited) ACE, denying the
   principal identified by the URL http://www.foo.org/users/ejw (i.e.,
   the user ôejw") DAV:write permission. This conflicts with inherited
   ACE #1. Note that the decision to report an inherited ACE conflict is
   specific to this server implementation. Another server implementation
   could have allowed the new ACE to be set, and then used normal ACE
   evaluation rules to determine whether the new ACE has any impact on
   the privileges available to a principal.

     >> Request <<

     ACL /top/index.html HTTP/1.1
     Host: www.foo.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx
     Authorization: Digest username="ejw",
        realm="users@foo.org", nonce="...",
        uri="/top/index.html", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:acl xmlns:D="DAV:" xmlns:F="http://www.foo.org/privs/">
       <D:ace>
         <D:principal>
           <D:href>http://www.foo.org/users/ejw</D:href>
         </D:principal>
         <D:grant><D:write/></D:grant>
       </D:ace>
     </D:acl>

     >> Response <<

     HTTP/1.1 403 Forbidden
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>

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     <D:inherited-ace-conflict xmlns:D="DAV:"/>

8.1.5 Example: ACL method failure due to an attempt to set grant and
      deny in a single ACE.

   In this example, user "ygoland", authenticated by information in the
   Authorization header, tries to change the access control list on the
   resource http://www.foo.org/diamond/engagement-ring.gif. The ACL
   request includes a single, syntactically and semantically incorrect
   ACE, which attempts to grant the collection principal identified by
   the URL http://www.foo.org/users/friends/ DAV:read privilege and deny
   the principal identified by URL http://www.foo.org/users/ygoland-so
   (i.e., the user "ygoland-so") DAV:read privilege. However, it is
   illegal to have multiple principal elements, as well as both a grant
   and deny element in the same ACE, so the request fails due to poor
   syntax.

     >> Request <<

     ACL /diamond/engagement-ring.gif HTTP/1.1
     Host: www.foo.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx
     Authorization: Digest username="ygoland",
        realm="users@foo.org", nonce="...",
        uri="/diamond/engagement-ring.gif", response="...", opaque="..."

     <?xml version="1.0" encoding="utf-8" ?>
     <D:acl xmlns:D="DAV:">
       <D:ace>
         <D:principal>
           <D:href>http://www.foo.org/users/friends/</D:href>
         </D:principal>
         <D:grant><D:read/></D:grant>
         <D:principal>
           <D:href>http://www.foo.org/users/ygoland-so</D:href>
         </D:principal>
         <D:deny><D:read/></D:deny>
       </D:ace>
     </D:acl>

     >> Response <<

     HTTP/1.1 400 Bad Request
     Content-Length: 0

   Note that if the request had been divided into two ACEs, one to
   grant, and one to deny, the request would have been syntactically
   well formed.


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9  ACCESS CONTROL REPORTS

9.1 REPORT Method

   The REPORT method (defined in Section 3.6 of [RFCxxxx]) provides an
   extensible mechanism for obtaining information about a resource.
   Unlike the PROPFIND method, which returns the value of one or more
   named properties, the REPORT method can involve more complex
   processing. REPORT is valuable in cases where the server has access
   to all of the information needed to perform the complex request (such
   as a query), and where it would require multiple requests for the
   client to retrieve the information needed to perform the same
   request.

9.2 DAV:acl-principal-props Report

   The DAV:acl-principle-props report returns, for all principals in the
   DAV:acl property that are identified by http(s) URLs, the value of
   the properties specified in the REPORT request body. In the case
   where a principal URL appears multiple times, the DAV:acl-principal-
   props report MUST return the properties for that principal only once.

   Marshalling

   The request body MUST be a DAV:acl-principal-props XML element.

     <!ELEMENT acl-principal-props ANY>
     ANY value: a sequence of one or more elements, with at most one
     DAV:prop element.
     prop: see RFC 2518, Section 12.11


   The response body for a successful request MUST be a DAV:multistatus
   XML element (i.e., the response uses the same format as the response
   for PROPFIND).

     multistatus: see RFC 2518, Section 12.9

   The response body for a successful DAV:acl-principal-props REPORT
   request MUST contain a DAV:response element for each principal
   identified by an http(s) URL listed in a DAV:principal XML element of
   an ACE within the DAV:acl property of the resource identified by the
   Request-URI.

9.2.1 Example: DAV:acl-principal-props Report

   Resource http://www.webdav.org/index.html has an ACL with three ACEs:

   ACE #1: All principals (DAV:all) have DAV:read and DAV:read-current-
   user-privilege-set access.


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   ACE #2: The principal identified by
   http://www.webdav.org/people/gstein (the user ôgstein") is granted
   DAV:write,  DAV:write-acl, DAV:read-acl privileges.

   ACE #3: The collection principal identified by
   http://www.webdav.org/groups/authors/ (the ôauthors" group) is
   granted DAV:write and DAV:read-acl privileges.

   The following example shows a DAV:acl-principal-props report
   requesting the DAV:displayname property. It returns the value of
   DAV:displayname for resources http://www.webdav.org/people/gstein and
   http://www.webdav.org/groups/authors/ , but not for DAV:all, since
   this is not an http(s) URL.


   >> Request <<


     REPORT /index.html HTTP/1.1
     Host: www.webdav.org
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:acl-principal-props xmlns:D="DAV:">
       <D:prop>
         <D:displayname/>
       </D:prop>
     </D:acl-principal-props>

   >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/people/gstein</D:href>
         <D:propstat>
           <D:prop>
             <D:displayname>Greg Stein</D:displayname>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
       <D:response>
         <D:href>http://www.webdav.org/groups/authors/</D:href>
         <D:propstat>
           <D:prop>

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             <D:displayname>Site authors</D:displayname>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>

9.3 DAV:principal-match REPORT

   The DAV:principal-match REPORT is used to identify all members of a
   collection that match the current user. In particular, if the
   collection contains principals, the report can be used to identify
   all members of the collection that match the current user.
   Alternatively, if the collection contains resources that have a
   property that identifies a principal (e.g. DAV:owner), then the
   report can be used to identify all members of the collection whose
   property identifies a principal that matches the current user. For
   example, this report can return all of the resources in a collection
   hierarchy that are owned by the current user.

   The Depth header (defined in Section 9.2 of [RFC2518]), with value
   "infinity", can be used with this report. In this case, the report
   operates on the collection in the Request-URI, as well as all child
   collections, grandchild collections, etc.

   Marshalling:

   The request body MUST be a DAV:principal-match XML element.

     <!ELEMENT principal-match ((principal-property | self), prop?)>
     <!ELEMENT principal-property ANY>
     ANY value: an element whose value identifies a property. The
     expectation is the value of the named property typically contains
     an href element that contains the URI of a principal
     <!ELEMENT self EMPTY>
     prop: see RFC 2518, Section 12.11


   The response body for a successful request MUST be a DAV:multistatus
   XML element.

     multistatus: see RFC 2518, Section 12.9


   The response body for a successful DAV:principal-match REPORT request
   MUST contain a DAV:response element for each member of the collection
   that matches the current user. When the DAV:principal-property
   element is used, a match occurs if the current user is the same as
   the principal identified by the URI found in the DAV:href element of
   the property identified by the DAV:principal-property element. When
   the DAV:self element is used in a DAV:principal-match report issued
   against a collection principal, it matches a child of the collection

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   principal if that child (a principal resource) identifies the same
   principal as the current user.

   If DAV:prop is specified in the request body, the properties
   specified in the DAV:prop element MUST be reported in the
   DAV:response elements.

9.3.1 Example: DAV:principal-match REPORT

   The following example identifies the members of the collection
   identified by the URL http://www.webdav.org/doc/ that are owned by
   the current user. The current user (ôgclemm") is authenticated using
   Digest authentication.

   >> Request <<

     REPORT /doc/ HTTP/1.1
     Host: www.webdav.org
     Authorization: Digest username="gclemm",
        realm="gclemm@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx
     Depth: infinity

     <?xml version="1.0" encoding="utf-8" ?>
     <D:principal-match xmlns:D="DAV:">
       <D:principal-property>
         <D:owner/>
       </D:principal-property>
     </D:principal-match>

     >> Response <<

     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:">
       <D:response>
         <D:href>http://www.webdav.org/doc/foo.html</D:href>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:response>
       <D:response>
         <D:href>http://www.webdav.org/doc/img/bar.gif</D:href>
         <D:status>HTTP/1.1 200 OK</D:status>
       </D:response>
     </D:multistatus>


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9.4 DAV:principal-property-search REPORT

   The DAV:principal-property-search REPORT performs a substring search
   on the character data value of specified properties. The server MUST
   perform caseless matching of substrings. Only properties defined on
   principal or collection principal resources are searched. For
   implementation efficiency, servers do not typically support substring
   searching on all properties. A client can discover the set of
   searchable properties by using the principal-search-property-set
   REPORT, defined in Section 9.5.

      Implementation Note: The value of a WebDAV property is a sequence
      of well-formed XML, and hence can include any character in the
      Unicode/ISO-10646 standard, that is, most known characters in
      human languages. Due to the idiosyncrasies of case mapping across
      human languages, implementation of caseless matching is non-
      trivial. Implementors are strongly encouraged to consult
      [CaseMap], especially Section 2.3 ("Caseless Matching"), for
      guidance when implementing their caseless matching algorithms.

   Marshalling:

   The DAV:principal-collection-set property of the resource identified
   by the Request-URI specifies the scope of the DAV:principal-property-
   search REPORT, as follows:

   - All principal and collection principal resources identified in
   DAV:principal-collection-set are searched
   - All principal and collection principal resources that are
   descendents of a collection principal resource identified in
   DAV:principal collection-set are searched.

   Servers MUST support the DAV:principal-property-search REPORT on all
   principal collections identified in the value of a DAV:principal-
   collection-set property.

   The request body MUST be a DAV:principal-property-search XML element
   containing a search specification and an optional list of properties.
   For every principal that matches the search specification, the
   response will contain the value of the properties on that principal.

     <!ELEMENT principal-property-search ((property-search+), prop?) >

   The DAV:property-search element contains a prop element enumerating
   the properties to be searched and a caseless-substring element,
   containing the search string.

     <!ELEMENT property-search (prop, caseless-substring) >
     prop: see RFC 2518, Section 12.11

     <!ELEMENT caseless-substring #PCDATA >

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   Multiple property-search elements or multiple elements within a
   DAV:prop element will be interpreted with a logical AND.  An empty
   DAV:caseless-substring element will match all properties specified in
   its parent DAV:property-search element.

   The response body for a successful request MUST be a DAV:multistatus
   XML element.

     multistatus: see RFC 2518, Section 12.9

   The response body for a successful DAV:principal-property-search
   REPORT request MUST contain  a DAV:response element for each
   principal whose property values satisfy the search specification
   given in DAV:principal-property-search.

   If DAV:prop is specified in the request body, the properties
   specified in the DAV:prop element MUST be reported in the
   DAV:response elements.

   Errors:

   If a request specifies a search of  a property that is not
   searchable, a 403 (Forbidden) response MUST be returned and the
   response body MUST be a DAV:non-searchable-property element,
   containing the unsearchable properties.

     <!ELEMENT non-searchable-property (prop) >


9.4.1 Matching

   There are several cases to consider when matching strings. The
   easiest case is when a property value is "simple" and has only
   character information item content (see [REC-XMLINFOSET]). For
   example, the search string "julian" would match the DAV:displayname
   property with value "Julian Reschke". Note that the on-the-wire
   marshalling of DAV:displayname in this case is:

     <D:displayname xmlns:D="DAV:">Julian Reschke</D:displayname>


   The name of the property is encoded into the XML element information
   item, and the character information item content of the property is
   "Julian Reschke".

   The more complicated case occurred when properties have mixed content
   (that is, compound values consisting of multiple child element items,
   other types of information items, and character information item
   content). Consider the property http://www.webdav.org/props/aprop,
   marshalled as:


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     <W:aprop xmlns:W="http://www.webdav.org/props/">
     {cdata 0}<W:elem1>{cdata 1}</W:elem1>
       <W:elem2>{cdata 2}</W:elem2>{cdata 3}
     </W:aprop>


   In this case, substring matching is performed on each individual
   contiguous sequence of character information items. In the example
   above, a search string would be compared to the four following
   strings:

     {cdata 0}
     {cdata 1}
     {cdata 2}
     {cdata 3}

   That is, four individual caseless substring matches would be
   performed, one each for {cdata 0}, {cdata 1}, {cdata 2}, and {cdata
   3}.

9.4.2 Example: successful DAV:principal-property-search REPORT

   In this example, the client requests the principal URLs of all users
   whose DAV:displayname property contains the substring "doE" and whose
   http://BigCorp.com/ns/title property (that is, their professional
   title) contains "sales".  In addition, the client requests five
   properties to be returned with the matching principals:

   In the DAV: namespace: displayname
   In the http://www.BigCorp.com/ns/ namespace: department, phone,
   office, salary

   The response shows that two principal resources meet the search
   specification, "John Doe" and "Zygdoebert Smith". The property
   "salary" in namespace "http://www.BigCorp.com/ns/" is not returned,
   since the principal making the request does not have sufficient
   access permissions to read this property.


   >> Request <<

     REPORT /users/ HTTP/1.1
     Host: www.BigCorp.com
     Content-Type: text/xml; charset=utf-8
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:principal-property-search xmlns:D="DAV:">
       <D:property-search>
         <D:prop>


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           <D:displayname/>
         </D:prop>
         <D:caseless-substring>doE</D:caseless-substring>
       </D:property-search>
       <D:property-search>
         <D:prop xmlns:B="http://www.BigCorp.com/ns/">
           <B:title/>
         </D:prop>
         <D:caseless-substring>sales</D:caseless-substring>
       </D:property-search>
       <D:prop xmlns:B="http://www.BigCorp.com/ns/">
         <D:displayname/>
         <B:department/>
         <B:phone/>
         <B:office/>
         <B:salary/>
       </D:prop>
     </D:principal-property-search>


   >> Response <<



     HTTP/1.1 207 Multi-Status
     Content-Type: text/xml; charset=utf-8
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:" xmlns:B="http://BigCorp.com/ns/">
       <D:response>
         <D:href>http://www.BigCorp.com/users/jdoe</D:href>
         <D:propstat>
           <D:prop>
             <D:displayname>John Doe</D:displayname>
             <B:department>Widget Sales</B:department>
             <B:phone>234-4567</B:phone>
             <B:office>209</B:office>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
         <D:propstat>
           <D:prop>
             <B:salary/>
           </D:prop>
           <D:status>HTTP/1.1 403 Forbidden</D:status>
         </D:propstat>
       </D:response>
       <D:response>
         <D:href>http://www.BigCorp.com/users/zsmith</D:href>
         <D:propstat>

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           <D:prop>
             <D:displayname>Zygdoebert Smith</D:displayname>
             <B:department>Gadget Sales</B:department>
             <B:phone>234-7654</B:phone>
             <B:office>114</B:office>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
         <D:propstat>
           <D:prop>
             <B:salary/>
           </D:prop>
           <D:status>HTTP/1.1 403 Forbidden</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>


9.4.3 Example: Unsuccessful DAV:principal-property-search REPORT

   In this example, the client requests a search on the non-searchable
   property "phone" in the namespace "http://www.BigCorp.com/ns/".  The
   response is a 403 (Forbidden), with a response body containing the
   XML element DAV:non-searchable-property listing the non-searchable
   property.

   >> Request <<

     REPORT /users/ HTTP/1.1
     Host: www.BigCorp.com
     Content-Type: text/xml; charset=utf-8
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:principal-property-search xmlns:D="DAV:">
       <D:property-search>
         <D:prop xmlns:B="http://www.BigCorp.com/ns/">
           <B:phone/>
         </D:prop>
         <D:caseless-substring>232</D:caseless-substring>
       </D:property-search>
     </D:principal-property-search>


   >> Response <<


     HTTP/1.1 403 FORBIDDEN
     Content-Type: text/xml; charset=utf-8
     Content-Length: xxxx


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     <?xml version="1.0" encoding="utf-8" ?>
     <D:non-searchable-property xmlns:D="DAV:">
       <D:prop xmlns:B="http://www.BigCorp.com/ns/">
         <B:phone/>
       </D:prop>
     </D:non-searchable-property>


9.5 DAV:principal-search-property-set REPORT

   The DAV:principal-search-property-set REPORT identifies those
   properties that may be searched using the DAV:principal-property-
   search REPORT (defined in Section 9.4). The DAV:principal-collection-
   set property of the resource identified by the Request-URI specifies
   the scope of the DAV:principal-search-property-set REPORT, as
   follows:

   - All principal and collection principal resources identified in
   DAV:principal-collection-set are in scope
   - All principal and collection principal resources that are
   descendents of a collection principal resource identified in
   DAV:principal collection-set are also in scope.

   Principals and collection principals within this scope are examined
   for searchable properties.

   Servers MUST support the DAV:principal-search-property-set REPORT on
   all principal collections identified in the value of a DAV:principal-
   collection-set property.

   An access control protocol user agent could use the results of the
   DAV:principal-search-property-set REPORT to present a query interface
   to the user for retrieving principals.

   Marshalling:

   The request body MUST be an empty DAV:principal-search-property-set
   XML element.

   The response body MUST be a DAV:principal-search-property-set XML
   element, containing a DAV:principal-search-property XML element for
   each property that may be searched with the DAV:principal-property-
   search REPORT. A server MAY limit its response to just a subset of
   the searchable properties, such as those likely to be useful to an
   interactive access control client.

     <!ELEMENT principal-search-property-set (principal-search-
     property*) >


   Each DAV:principal-search-property XML element contains exactly one
   searchable property, and a description of the property.

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     <!ELEMENT principal-search-property (prop, description) >

   The DAV:prop element contains one principal property on which the
   server is able to perform DAV:principal-property-search REPORTs.

     prop: see RFC 2518, Section 12.11

   The description element is a human-readable description of what
   information this property represents. Servers MUST indicate the human
   language of the description using the xml:lang attribute and SHOULD
   consider the HTTP Accept-Language request header when selecting one
   of multiple available languages.

     <!ELEMENT description #PCDATA >

9.5.1 Example: DAV:principal-search-property-set REPORT

   In this example, the client determines the set of searchable
   principal properties by requesting the DAV:principal-search-property-
   set REPORT on the root of the serverÆs principal URL collection set,
   identified by http://www.BigCorp.com/users/.

   >> Request <<

     REPORT /users/ HTTP/1.1
     Host: www.BigCorp.com
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx
     Accept-Language: en, de
     Authorization: BASIC d2FubmFtYWs6cGFzc3dvcmQ=

     <?xml version="1.0" encoding="utf-8" ?>
     <D:principal-search-property-set xmlns:D="DAV:"/>


   >> Response <<

     HTTP/1.1 200 OK
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:principal-search-property-set xmlns:D="DAV:">
       <D:principal-search-property>
         <D:prop>
           <D:displayname/>
         </D:prop>
         <D:description xml:lang="en">Full name</D:description>
       </D:principal-search-property>
       <D:principal-search-property>
         <D:prop xmlns:B="http://BigCorp.com/ns/">
           <B:title/>

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         </D:prop>
         <D:description xml:lang="en">Job title</D:description>
       </D:principal-search-property>
     </D:principal-search-property-set>


10 XML PROCESSING

   Implementations of this specification MUST support the XML element
   ignore rule, as specified in Section 23.3.2 of [RFC2518], and the XML
   Namespace Recommendation [REC-XML-NAMES].

   Note that use of the DAV namespace is reserved for XML elements and
   property names defined in a standards-track or Experimental IETF RFC.


11 INTERNATIONALIZATION CONSIDERATIONS

   In this specification, the only human-readable content can be found
   in the description XML element, found within the DAV:supported-
   privilege-set property.  This element contains a human-readable
   description of the capabilities controlled by a privilege.  As a
   result, the description element must be capable of representing
   descriptions in multiple character sets.  Since the description
   element is found within a WebDAV property, it is represented on-the-
   wire as XML [REC-XML], and hence can leverage XML's language tagging
   and character set encoding capabilities. Specifically, XML processors
   must, at minimum, be able to read XML elements encoded using the UTF-
   8 [UTF-8] encoding of the ISO 10646 multilingual plane. XML examples
   in this specification demonstrate use of the charset parameter of the
   Content-Type header, as defined in [RFC3023], as well as the XML
   "encoding" attribute, which together provide charset identification
   information for MIME and XML processors. Furthermore, this
   specification requires server implementations to tag description
   fields with the xml:lang attribute (see Section 2.12 of [REC-XML]),
   which specifies the human language of the description. Additionally,
   server implementations should take into account the value of the
   Accept-Language HTTP header to determine which description string to
   return.

   For XML elements other than the description element, it is expected
   that implementations will treat the property names, privilege names,
   and values as tokens, and convert these tokens into human-readable
   text in the user's language and character set when displayed to a
   person.  Only a generic WebDAV property display utility would display
   these values in their raw form to a human user.

   For error reporting, we follow the convention of HTTP/1.1 status
   codes, including with each status code a short, English description
   of the code (e.g., 200 (OK)).  While the possibility exists that a
   poorly crafted user agent would display this message to a user,

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   internationalized applications will ignore this message, and display
   an appropriate message in the user's language and character set.

   Further internationalization considerations for this protocol are
   described in the WebDAV Distributed Authoring protocol specification
   [RFC2518].


12 SECURITY CONSIDERATIONS

   Applications and users of this access control protocol should be
   aware of several security considerations, detailed below. In addition
   to the discussion in this document, the security considerations
   detailed in the HTTP/1.1 specification [RFC2616], the WebDAV
   Distributed Authoring Protocol specification [RFC2518], and the XML
   Media Types specification [RFC3023] should be considered in a
   security analysis of this protocol.

12.1 Increased Risk of Compromised Users

   In the absence of a mechanism for remotely manipulating access
   control lists, if a single user's authentication credentials are
   compromised, only those resources for which the user has access
   permission can be read, modified, moved, or deleted. With the
   introduction of this access control protocol, if a single compromised
   user has the ability to change ACLs for a broad range of other users
   (e.g., a super-user), the number of resources that could be altered
   by a single compromised user increases. This risk can be mitigated by
   limiting the number of people who have write-acl privileges across a
   broad range of resources.

12.2 Risks of the DAV:read-acl and DAV:current-user-privilege-set
     Privileges

   The ability to read the access privileges (stored in the DAV:acl
   property), or the privileges permitted the currently authenticated
   user (stored in the DAV:current-user-privilege-set property) on a
   resource may seem innocuous, since reading an ACL cannot possibly
   affect the resource's state. However, if all resources have world-
   readable ACLs, it is possible to perform an exhaustive search for
   those resources that have inadvertently left themselves in a
   vulnerable state, such as being world-writeable. In particular, the
   property retrieval method PROPFIND, executed with Depth infinity on
   an entire hierarchy, is a very efficient way to retrieve the DAV:acl
   or DAV:current-user-privilege-set properties. Once found, this
   vulnerability can be exploited by a denial of service attack in which
   the open resource is repeatedly overwritten. Alternately, writeable
   resources can be modified in undesirable ways.

   To reduce this risk, read-acl privileges should not be granted to
   unauthenticated principals, and restrictions on read-acl and read-

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   current-user-privilege-set privileges for authenticated principals
   should be carefully analyzed when deploying this protocol. Access to
   the current-user-privilege-set property will involve a tradeoff of
   usability versus security. When the current-user-privilege-set is
   visible, user interfaces are expected to provide enhanced information
   concerning permitted and restricted operations, yet this information
   may also indicate a vulnerability that could be exploited. Deployment
   of this protocol will need to evaluate this tradeoff in light of the
   requirements of the deployment environment.

12.3 No Foreknowledge of Initial ACL

   In an effort to reduce protocol complexity, this protocol
   specification intentionally does not address the issue of how to
   manage or discover the initial ACL that is placed upon a resource
   when it is created. The only way to discover the initial ACL is to
   create a new resource, then retrieve the value of the DAV:acl
   property. This assumes the principal creating the resource also has
   been granted the DAV:read-acl privilege.

   As a result, it is possible that a principal could create a resource,
   and then discover that its ACL grants privileges that are
   undesirable. Furthermore, this protocol makes it possible (though
   unlikely) that the creating principal could be unable to modify the
   ACL, or even delete the resource. Even when the ACL can be modified,
   there will be a short period of time when the resource exists with
   the initial ACL before its new ACL can be set.

   Several factors mitigate this risk. Human principals are often aware
   of the default access permissions in their editing environments and
   take this into account when writing information. Furthermore, default
   privilege policies are usually very conservative, limiting the
   privileges granted by the initial ACL.


13 AUTHENTICATION

   Authentication mechanisms defined for use with HTTP and  WebDAV also
   apply to this WebDAV Access Control Protocol, in particular the Basic
   and Digest authentication mechanisms defined in [RFC2617].


14 IANA CONSIDERATIONS

   This document uses the namespace defined by [RFC2518] for XML
   elements.  All other IANA considerations mentioned in [RFC2518] also
   applicable to WebDAV ACL.




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15 INTELLECTUAL PROPERTY

   The following notice is copied from RFC 2026, section 10.4, and
   describes the position of the IETF concerning intellectual property
   claims made against this document.

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use other technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication 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 Secretariat.

   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 practice
   this standard.  Please address the information to the IETF Executive
   Director.


16 ACKNOWLEDGEMENTS

   This protocol is the collaborative product of the WebDAV ACL design
   team: Bernard Chester, Geoff Clemm, Anne Hopkins, Barry Lind, Sean
   Lyndersay, Eric Sedlar, Greg Stein, and Jim Whitehead. The authors
   are grateful for the detailed review and comments provided by Jim
   Amsden, Gino Basso, Murthy Chintalapati, Dennis Hamilton, Laurie
   Harper, Ron Jacobs, Chris Knight, Remy Maucherat, Larry Masinter,
   Yaron Goland, Lisa Dusseault, Joe Orton, Stefan Eissing, Julian
   Reschke, Keith Wannamaker, Tim Ellison, and Dylan Barrell. We thank
   Keith Wannamaker for the initial text of the principal property
   search sections. Prior work on WebDAV access control protocols has
   been performed by Yaron Goland, Paul Leach, Lisa Dusseault, Howard
   Palmer, and Jon Radoff. We would like to acknowledge the foundation
   laid for us by the authors of the DeltaV, WebDAV and HTTP protocols
   upon which this protocol is layered, and the invaluable feedback from
   the WebDAV working group.







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17 REFERENCES

17.1 Normative References

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

   [REC-XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible
   Markup Language (XML)." World Wide Web Consortium Recommendation REC-
   xml.http://www.w3.org/TR/REC-xml

   [REC-XML-NAMES] T. Bray, D. Hollander, A. Layman, ôName Spaces in
   XML" World Wide Web Consortium Recommendation REC-xml-names.
   http://www.w3.org/TR/REC-xml-names/

   [RFCxxxx] G. Clemm, J. Amsden, T. Ellison, C. Kaler, J. Whitehead,
   "Versioning Extensions to WebDAV." RFC xxxx. Rational, IBM,
   Microsoft, U.C. Santa Cruz, 2001.

   [REC-XML-INFOSET] J. Cowan, R. Tobin, "XML Information Set." World
   Wide Web Consortium Recommendation REC-xml-infoset.
   http://www.w3.org/TR/xml-infoset/

   [RFC2616] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, L.
   Masinter, P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol
   -- HTTP/1.1." RFC 2616. U.C. Irvine, Compaq, Xerox, Microsoft,
   MIT/LCS, June, 1999.

   [RFC2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, P.
   Leach, A. Luotonen, L. Stewart, "HTTP Authentication: Basic and
   Digest Access Authentication." RFC 2617. Northwestern University,
   Verisign, AbiSource, Agranat, Microsoft, Netscape, Open Market, June,
   1999.

   [RFC2518] Y. Goland, E. Whitehead, A. Faizi, S. R. Carter, D. Jensen,
   "HTTP Extensions for Distributed Authoring -- WEBDAV." RFC 2518.
   Microsoft, U.C. Irvine, Netscape, Novell, February, 1999.

   [RFC2368] P. Hoffman, L. Masinter, J. Zawinski, "The mailto URL
   scheme." RFC 2368. Internet Mail Consortium, Xerox, Netscape, July,
   1998.

   [RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types." RFC
   3023. IBM Tokyo Research Laboratory, simonstl.com, Skymoon Ventures,
   January, 2001.

   [UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode and
   ISO 10646." RFC 2279. Alis Technologies. January, 1998.





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17.2 Informational References

   [RFC2026] S.Bradner, "The Internet Standards Process û Revision 3."
   RFC 2026, BCP 9. Harvard, October, 1996.

   [RFC2255] T. Howes, M. Smith, "The LDAP URL Format." RFC 2255.
   Netscape, December, 1997.

   [RFC2251] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
   Protocol (v3)." RFC 2251. Critical Angle, Netscape, Isode, December,
   1997.

   [CaseMap] M. Davis, "Case Mappings", Unicode Technical Report #21,
   <http://www.unicode.org/unicode/reports/tr21>


18 AUTHORS' ADDRESSES

     Geoffrey Clemm
     Rational Software
     20 Maguire Road
     Lexington, MA 02421
     Email: geoffrey.clemm@rational.com

     Anne Hopkins
     Microsoft Corporation
     One Microsoft Way
     Redmond, WA 98052
     Email: annehop@microsoft.com

     Eric Sedlar
     Oracle Corporation
     500 Oracle Parkway
     Redwood Shores, CA 94065
     Email: esedlar@us.oracle.com

     Jim Whitehead
     U.C. Santa Cruz
     Dept. of Computer Science
     Baskin Engineering
     1156 High Street
     Santa Cruz, CA 95064
     Email: ejw@cse.ucsc.edu








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19 APPENDICIES

19.1 WebDAV XML Document Type Definition Addendum

   All XML elements defined in this Document Type Definition (DTD)
   belong to the DAV namespace. This DTD should be viewed as an addendum
   to the DTD provided in [RFC2518], section 23.1.

     <!-- Privileges -->

     <!ELEMENT read EMPTY>
     <!ELEMENT write EMPTY>
     <!ELEMENT read-acl EMPTY>
     <!ELEMENT read-current-user-privilege-set EMPTY>
     <!ELEMENT write-acl EMPTY>
     <!ELEMENT all EMPTY>


     <!-- Principal Properties (Section 4) -->

     <!ELEMENT principalEMPTY>

     <!ELEMENT alternate-URI-set (href*)>
     <!ELEMENT principal-URL (href)>

     <!-- Access Control Properties (Section 5) -->

     <!-- DAV:owner Property (Section 5.1) -->

     <!ELEMENT owner (href prop?)>
     <!ELEMENT prop (see [RFC2518], section 12.11)>


     <!-- DAV:supported-privilege-set Property (Section 5.2) -->

     <!ELEMENT supported-privilege-set (supported-privilege*)>
     <!ELEMENT supported-privilege
      (privilege, abstract?, description, supported-privilege*)>

     <!ELEMENT privilege ANY>
     <!ELEMENT abstract EMPTY>
     <!ELEMENT description #PCDATA>
     <!ELEMENT privilege ANY>


     <!-- DAV:current-user-privilege-set Property (Section 5.3) -->

     <!ELEMENT current-user-privilege-set (privilege*)>

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     <!-- DAV:acl Property (Section 5.4) -->

     <!ELEMENT acl (ace*)>

     <!ELEMENT ace (principal, (grant|deny), protected?, inherited?)>
     <!ELEMENT principal ((href, prop?)
      | all | authenticated | unauthenticated
      | property | self)>

     <!ELEMENT prop (see [RFC2518], section 12.11)>
     <!ELEMENT all EMPTY>
     <!ELEMENT authenticated EMPTY>
     <!ELEMENT unauthenticated EMPTY>
     <!ELEMENT property ANY>
     <!ELEMENT self EMPTY>

     <!ELEMENT grant (privilege+)>
     <!ELEMENT deny (privilege+)>
     <!ELEMENT privilege ANY>

     <!ELEMENT protected EMPTY>

     <!ELEMENT inherited (href)>


     <!-- DAV:principal-collection-set Property (Section 5.6) -->

     <!ELEMENT principal-collection-set (href*)>


     <!-- DAV:acl-semantics Property (Section 6) -->

     <!ELEMENT acl-semantics (ace-combination?, ace-ordering?, allowed-
     ace?, required-principal?)>

     <!ELEMENT ace-combination
      (first-match | all-grant-before-any-deny | specific-deny-
     overrides-grant)>
     <!ELEMENT first-match EMPTY>
     <!ELEMENT all-grant-before-any-deny EMPTY>
     <!ELEMENT specific-deny-overrides-grant EMPTY>

     <!ELEMENT ace-ordering (deny-before-grant)? >
     <!ELEMENT deny-before-grant EMPTY>

     <!ELEMENT allowed-ace (principal-only-one-ace | grant-only)*>
     <!ELEMENT principal-only-one-ace EMPTY>
     <!ELEMENT grant-only EMPTY>

     <!ELEMENT required-principal

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       (all? | authenticated? | unauthenticated? | self? | href*
     |property*)>


     <!-- ACL method preconditions (Section 8.1.1) -->

     <!ELEMENT ace-conflict EMPTY>
     <!ELEMENT protected-ace-conflict EMPTY>
     <!ELEMENT inherited-ace-conflict EMPTY>
     <!ELEMENT too-many-aces EMPTY>


     <!-- REPORTs (Section 9) -->

     <!ELEMENT acl-principal-props ANY>
     ANY value: a sequence of one or more elements, with at most one
     DAV:prop element.

     <!ELEMENT principal-match ((principal-property | self), prop?)>
     <!ELEMENT principal-property ANY>
     ANY value: an element whose value identifies a property. The
     expectation is the value of the named property typically contains
     an href element that contains the URI of a principal

     <!ELEMENT self EMPTY>

     <!ELEMENT principal-property-search ((property-search+), prop?) >
     <!ELEMENT property-search (prop, caseless-substring) >
     <!ELEMENT caseless-substring #PCDATA >
     <!ELEMENT non-searchable-property (prop) >

     <!ELEMENT principal-search-property-set (principal-search-
     property*) >
     <!ELEMENT principal-search-property (prop, description) >


20 NOTE TO RFC EDITOR

   As of the writing of this specification, the DeltaV protocol,
   described in draft-ietf-deltav-versioning-20, has been approved by
   the IESG, but not yet published as an RFC. Within this specification,
   the DeltaV protocol is referenced as [RFCxxxx]. These references need
   to be replaced with the actual RFC number. As well, the citation in
   Section 17.1 also needs to be updated with the correct RFC number,
   and the month of issue.






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