INTERNET-DRAFT                    Geoffrey Clemm, Rational Software
   draft-ietf-webdav-acl-06
draft-ietf-webdav-acl-07          Anne Hopkins, Microsoft Corporation
                                  Eric Sedlar, Oracle Corporation
                                  Jim Whitehead, U.C. Santa Cruz

Expires December 21, May 9, 2001        June 21,               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.

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or to cite them other than as "work in progress."

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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
   remotely read and modify
access control lists that instruct a server whether to grant 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...................................................4 INTRODUCTION.......................................................5
1.1  Terms.......................................................5 Terms............................................................7
1.2 Notational Conventions......................................6 Conventions...........................................8

2 PRINCIPALS.....................................................6 PRINCIPALS.........................................................8

3 PRIVILEGES.....................................................7 PRIVILEGES.........................................................9
3.1 DAV:read Privilege..........................................8 Privilege..............................................11
3.2 DAV:write Privilege.........................................8 Privilege.............................................11
3.3 DAV:read-acl Privilege......................................9 Privilege..........................................11
3.4 DAV:read-current-user-privilege-set Privilege...............9 Privilege...................11
3.5 DAV:write-acl Privilege.....................................9 Privilege.........................................12
3.6 DAV:all Privilege...........................................9 Privilege...............................................12
3.7 Aggregation of Predefined Privileges........................9 Privileges............................12

4 PRINCIPAL PROPERTIES..........................................10 PROPERTIES..............................................12
4.1  DAV:alternate-URL..........................................10 DAV:alternate-URI-set...........................................13

5 ACCESS CONTROL PROPERTIES.....................................10 PROPERTIES.........................................13
5.1  DAV:owner..................................................11 DAV:owner.......................................................13
 5.1.1 Example: Retrieving DAV:owner............................11 DAV:owner................................14
 5.1.2 Example: An Attempt to Set DAV:owner.....................12 DAV:owner.........................15
5.2  DAV:supported-privilege-set................................13 DAV:supported-privilege-set.....................................16
 5.2.1 Example: Retrieving a List of Privileges Supported on a
          Resource.................................................14
       Resource.....................................................16
5.3  DAV:current-user-privilege-set.............................15 DAV:current-user-privilege-set..................................18
 5.3.1 Example: Retrieving the User's Current Set of Assigned
          Privileges...............................................16
 Privileges.........................................................19
5.4  DAV:acl....................................................17 DAV:acl.........................................................20
 5.4.1 ACE Principal............................................17 Principal................................................20
 5.4.2 ACE Grant and Deny.......................................18 Deny...........................................21
 5.4.3 ACE Protection...........................................18 Protection...............................................21
 5.4.4 ACE Inheritance..........................................18 Inheritance..............................................22
 5.4.5 Example: Retrieving a Resource's Access Control List.....19 List......22
5.5  DAV:acl-semantics..........................................20 DAV:acl-semantics...............................................23
 5.5.1 Example: Retrieving DAV:acl-semantics....................21 DAV:acl-semantics........................24
5.6  DAV:principal-collection-set...............................22 DAV:principal-collection-set....................................25
 5.6.1 Example: Retrieving DAV:principal-collection-set.........22 DAV:principal-collection-set.............26
5.7 Example: PROPFIND to retrieve access control properties....23 properties.........27

6 ACL SEMANTICS.................................................27 SEMANTICS.....................................................30
6.1 ACE Combination............................................27 Combination.................................................31
 6.1.1 DAV:first-match ACE Combination..........................27 Combination..............................31
 6.1.2 DAV:all-grant-before-any-deny ACE Combination............27 Combination................31
 6.1.3 DAV:specific-deny-overrides-grant ACE Combination........27 Combination............31
6.2 ACE Ordering...............................................28 Ordering....................................................31
 6.2.1 DAV:deny-before-grant ACE Ordering.......................28 Ordering...........................32
6.3 Allowed ACE................................................28 ACE.....................................................32
 6.3.1 DAV:principal-only-one-ace ACE Constraint................28
    6.3.2 DAV:grant-only ACE Constraint............................28
   6.4  Required Principals........................................28 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...........................29 METHODS...............................32
7.1  OPTIONS....................................................29 OPTIONS.........................................................33
 7.1.1 Example - OPTIONS........................................29 OPTIONS............................................33
7.2  MOVE.......................................................29 MOVE............................................................33
7.3  COPY.......................................................29 COPY............................................................33
7.4 DELETE..........................................................33
7.5 LOCK............................................................34

8 ACCESS CONTROL METHODS........................................29 METHODS............................................34
8.1  ACL........................................................29 ACL.............................................................34
 8.1.1 ACL Preconditions........................................30 Preconditions............................................34
 8.1.2 Example: the ACL method..................................31 method......................................36
 8.1.3 Example: ACL method failure due to protected ACE
          conflict ................................................32 conflict....37
 8.1.4 Example: ACL method failure due to an inherited ACE conflict ................................................33 38
 8.1.5 Example: ACL method failure due to an attempt to set grant
       and deny in a single ACE ..........................34 ACE.....................................39

9 ACCESS CONTROL REPORTS........................................35 REPORTS............................................40
9.1 REPORT Method..............................................35 Method...................................................40
9.2 DAV:acl-principal-props Report.............................36 Report..................................40
 9.2.1 Example: DAV:acl-principal-props Report..................36 Report......................40
9.3 DAV:principal-match REPORT.................................37 REPORT......................................42
 9.3.1 Example: DAV:principal-match REPORT......................38 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..............................................39 PROCESSING..................................................51

11  INTERNATIONALIZATION CONSIDERATIONS.........................39 CONSIDERATIONS.............................51

12  SECURITY CONSIDERATIONS.....................................40 CONSIDERATIONS.........................................52
12.1  Increased Risk of Compromised Users........................40 Users...........................52
12.2  Risks of the DAV:read-acl and DAV:current-user-privilege-set
        Privileges.................................................40
      Privileges....................................................52
12.3  No Foreknowledge of Initial ACL............................41 ACL...............................53

13  AUTHENTICATION..............................................41  AUTHENTICATION..................................................53

14  IANA CONSIDERATIONS.........................................42 CONSIDERATIONS.............................................53

15  INTELLECTUAL PROPERTY.......................................42 PROPERTY...........................................54

16  ACKNOWLEDGEMENTS............................................42  ACKNOWLEDGEMENTS................................................54

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17  REFERENCES..................................................43  REFERENCES......................................................55
17.1  Normative References.......................................43 References..........................................55
17.2  Informational References...................................43 References......................................56

18  AUTHORS' ADDRESSES..........................................43 ADDRESSES..............................................56

19  APPENDICIES.................................................44  APPENDICIES.....................................................57
19.1  XML Document Type Definition...............................44 Definition..................................57

20  NOTE TO RFC EDITOR..........................................46 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 in 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 how what operations you can access 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 "how" "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.

        This specification intentionally omits discussion of
        authentication, as

   Since every ACE contains the HTTP protocol already has a number identifier of
        authentication mechanisms [RFC2617].  Some authentication a principal, client
   software operated by a human must provide a mechanism (such as HTTP Digest Authentication, for selecting
   this principal. This specification uses http(s) scheme URLs to
   identify principals, which all WebDAV
        compliant implementations are required to support) must represented as WebDAV-capable
   resources. There is no guarantee that the URLs identifying principals
   will be
        available meaningful to validate the identity of a principal.

        The following issues human. For example,
   http://www.dav.org/u/256432 and http://www.dav.org/people/Greg.Stein
   are out of scope for this document:

          * Access control both valid URLs that applies only could be used to a particular property
            on a identify the same
   principal. To remedy this, every principal resource (excepting has the access control properties
            DAV:acl and DAV:current-user-privilege-set), rather than
   DAV:displayname property containing a human-readable name for the entire resource,

          * Role-based security (where
   principal.

   Since a role principal can be seen as a
            dynamically defined collection of principals),

          * Specification of identified by multiple URLs, it raises the ways an ACL on
   problem of determining exactly which principal's operations are being
   described in a resource given ACE. It is
            initialized,

          * Specification of an ACL that applies globally impossible for a client to all
            resources , rather than 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 particular client has no mechanism for
   determining that two URLs identify the same principal resource.

          * Creation and maintenance  As a
   result, this specification requires clients to use just one of resources representing people
            or computational agents (principals), and groups 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 these.

        This specification the
   principal's URLs is organized as follows. Section 1.1 defines
        key concepts used throughout with PROPFIND, the specification, and is followed
        by more in-depth discussion property always returns
   the same URL.

   Once a system has hundreds to thousands 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 principals, the problem
   arises of
        access control lists are described in Section 6, including
        sections on ACE combination (Section 6.1), ACE ordering 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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        (Section 6.2), and principals required 5] 
   hierarchies to be present in an ACE
        (Section 6.4). Client discovery spread the principals over a large number of access control capability
        using OPTIONS
   collections, yielding few principals per collection. An example of
   this is described in Section 7.1, a two level hierarchy with the first level containing 36
   collections (a-z, 0-9), and the access
        control setting method, ACL, 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 specified in Section 8.
        Internationalization considerations (Section 11) that it handles only a
   small set of predefined queries, and security
        considerations (Section 12) round out drilling down through 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
   collection hierarchy adds unnecessary steps (navigate down/up) when
   the terms defined in HTTP [RFC2616] and WebDAV
        [RFC2518].  In addition, user already knows the following terms are defined: principal's name. While organizing
   principal

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

      principal collection

        A "principal collection" hierarchy is a group of principals, and is
        represented in valid namespace organization,
   users should not be forced to navigate this protocol by a WebDAV collection containing
        HTTP resources that represent principals, and principal
        collections.

      privilege

        A "privilege" controls access hierarchy to select a particular set of HTTP
        operations
   principal.

   This specification provides the capability to perform substring
   searches on a resource.

      aggregate privilege

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

      abstract privilege

        The modifier "abstract", when applied 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 a privilege, means search principal resources, the
        privilege cannot other to
   determine which properties may be set searched at all.

   Once a principal has been identified in an access control element (ace).

      access control list (ACL)

        An "ACL" is ACE, a list server evaluating
   that ACE must know the identity of access control elements the principal making a protocol
   request, and must validate that define
        access control that principal is who they claim to
   be, a particular resource.

      access control element (ace)

        An "ace" either grants or denies process known as authentication. This specification
   intentionally omits discussion of authentication, as the HTTP
   protocol already has a particular set 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 (non-
        abstract) privileges for a particular principal.

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      inherited ace

        An "inherited ace" is an ace that is dynamically shared from
        the ACL

   The following issues are out of another resource. When scope for this document:

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

        * Role-based security (where a protected property cannot role can be
        updated with seen as a PROPPATCH request.

   1.2 Notational Conventions

        The augmented BNF used by this document to describe protocol
        elements is described in Section 2.1 dynamically
          defined collection of principals),

        * Specification of [RFC2616]. Because this
        augmented BNF uses the basic production rules provided in
        Section 2.2 ways an ACL on a resource is initialized,

        * Specification of [RFC2616], those rules apply an ACL that applies globally to this document 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
        well.

        The follows. Section 1.1 defines key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
        NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   concepts used throughout the specification, and
        "OPTIONAL" in this document are to be interpreted as described 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 [RFC2119].

        Definitions
   Section 4, and access control properties for content resources are
   specified in Section 5. The semantics of XML elements access control lists are
   described in this document use XML element
        type declarations (as found Section 6, including sections on ACE combination
   (Section 6.1), ACE ordering (Section 6.2), and principals required to
   be present in XML Document Type Declarations), an ACE (Section 6.4). Client discovery of access
   control capability using OPTIONS is described in Section 3.2 7.1.
   Interactions between access control functionality and existing HTTP
   and WebDAV methods are described in the remainder of [REC-XML].

   2  PRINCIPALS 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 network resource that represents a distinct human or computational actor that
     initiates access to network resources. On many implementations, users and groups are
        represented as principals; other types of principals are also
        possible. A URI of any scheme MAY be used to identify a
        principal resource. However, servers implementing  In this
        specification MUST expose protocol, a
     principal resources at an http(s)
        URL, which is a privileged scheme that points to resources an HTTP resource that
        have additional properties, as described represents such an actor.

   principal collection

     A "principal collection" is a group of principals, and is
     represented in Section 4. So, this protocol by a WebDAV collection containing HTTP
     resources that represent principals, and principal resource can have multiple URI identifiers, one collections.

   privilege

     A "privilege" controls access to a particular set of
        which has 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 http(s) scheme URL. Although an
        implementation SHOULD support PROPFIND and MAY support
        PROPPATCH to access and modify information about a principal,
        it control element (ACE).

   access control list (ACL)

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     An "ACL" is not required to do so.

        A principal resource may or may not be a collection.  If list of access control elements that define access
     control to a
        person particular resource.

   access control element (ACE)

     An "ACE" either grants or computational agent matches denies a principal resource that
        is contained by particular set of (non-abstract)
     privileges for a collection principal, they also match the
        collection particular principal. This definition

   inherited ACE

     An "inherited ACE" is recursive, and hence
        if a person or computational agent matches a collection
        principal an ACE that is dynamically shared from the child
     ACL of another collection principal,
        they also match the parent collection principal. Membership in resource. When a collection principal shared ACE changes on the primary
     resource, it is also recursive, so a principal in changed on inheriting resources.

   protected property

    A "protected property" is one whose value cannot be updated except
    by a
        collection principal GRPA contained 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 collection principal

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 6] 
        GRPB this document to describe protocol elements
   is a member of both GRPA and GRPB. Implementations not
        supporting recursive membership described in principal collections can
        return an error if the client attempts to bind collection
        principals into other collection principals.

        Servers that support aggregation Section 2.1 of principals (e.g. groups [RFC2616]. Because this augmented BNF
   uses the basic production rules provided in Section 2.2 of
        users or other groups) MUST manifest them [RFC2616],
   those rules apply to this document as collection
        principals. At minimum, principals and collection principals
        MUST support the OPTIONS well.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and PROPFIND methods.

           Implementer's Note: Collection principals "OPTIONAL" in this
   document 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 be interpreted as members. When enumerating the principals-only membership described in [RFC2119].

   Definitions of a collection principal, it is necessary to retrieve the
           DAV:resourcetype property and check it for the DAV:principal XML elements in this document use XML element (described type
   declarations (as found in XML Document Type Declarations), described
   in Section 4). If the DAV:principal 3.2 of [REC-XML]. When an XML element is not present, type in the resource "DAV:"
   namespace is not a principal
           and may be ignored for the purposes referenced in this document outside of determining the
           principals-only membership context of an
   XML fragment, the collection principal.

           For example, string "DAV:" will be prefixed to the collection element type.

2  PRINCIPALS

   A principal /FOO/ has two members,
           Bar and Baz. Bar is a principal but Baz is not. Therefore
           when determining which network resource that represents a distinct human or
   computational actor that initiates access to network resources. Users
   and groups are represented as principals belong in many implementations;
   other types of principals are also possible. A URI of any scheme MAY
   be used to the collection
           principal /FOO/, identify 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 resource. However, servers
   implementing this specification MUST expose principal resources at an
   http(s) URL, which is a
           member of the collection principal /FOO/.

   3  PRIVILEGES

        Ability privileged scheme that points to perform a given method on resources
   that have additional properties, as described in Section 4. So, a
   principal resource SHOULD be
        controlled by can have multiple URIs, one or more privileges.  Authors of protocol
        extensions that define new HTTP methods SHOULD specify which
        privileges (by defining new privileges, or mapping has to ones
        below) are 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 perform the method. do so.

   A principal with no
        privileges to a resource SHOULD be denied any HTTP access to
        that resource.

        Privileges may or may not be containers of other privileges, in which case
        they are termed aggregate privileges. a collection.  If a principal is
        granted or denied an aggregate privilege, it is semantically
        equivalent to granting person 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
   computational agent matches a collection, these privileges would be aggregated principal resource that is contained by the
        DAV:write privilege on a collection, and granting the DAV:write
        privilege on
   a collection would principal, they also grant match the add-member collection principal.
   This definition is recursive, and
        remove-member privileges.

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        Privileges may have hence if a person or computational
   agent matches a collection principal that is the quality child of being abstract, in which
        case another
   collection principal, 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 match the privileges defined parent collection
   principal. Membership in this specification.  For example, if a server collection principal 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 also recursive, so
   a principal in this
        specification a collection principal GRPA contained by declaring them abstract, and containing them
        within collection
   principal GRPB is a non-abstract aggregate privilege (say, read-all) that
        holds DAV:read, member of both GRPA 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 GRPB. Implementations not possible
   supporting recursive membership in principal collections can return
   an error if the client attempts to
        set DAV:read, bind collection principals into
   other collection principals.

   Servers that support aggregation of principals (e.g. groups of users
   or DAV:read-acl individually. 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 aggregate
        privileges can there is no requirement that all members of a collection
     principal need be abstract, principals, it is also possible to use abstract
        privileges to group or organize non-abstract privileges.
        Privilege containment loops are not allowed, hence for a privilege
        MUST NOT contain itself. For example, DAV:read cannot contain
        DAV:read.

        The set of privileges that apply collection
     principal to have non-principals as members. When enumerating the
     principals-only membership of a particular 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
        vary with be ignored for the DAV:resourcetype purposes of determining the resource, as well as
        between different server implementations.  To promote
        interoperability, however, this specification defines a set
     principals-only membership of
        well-known privileges (e.g. DAV:read,DAV:write, DAV:read-acl,
        DAV:write-acl, DAV:read-current-user-privilege-set, the collection principal.

     For example, the collection principal /FOO/ has two members, Bar
     and
        DAV:all), Baz. Bar is a principal but Baz is not. Therefore when
     determining which can at least be used principals belong to classify the other
        privileges defined on collection principal
     /FOO/, a particular resource. The access
        permissions on null and lock-null resources (defined in
        [RFC2518], Sections 3 and 7.4) are solely those they inherit
        (if any), and they are not discoverable (i.e., client would enumerate the access
        control properties specified in Section 5 are not defined on
        null and lock-null resources). On membership using PROPFIND
     while asking for the transition from null or
        lock-null to a stateful resource, DAV:resourcetype property, and see that only
     Bar has the initial access control
        list DAV:principal XML element. Therefore, only Bar is set by the server's default ACL value policy (if any).

   3.1 DAV:read Privilege

        The read privilege controls methods
     only principal that return information
        about the state is a member 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 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 modify the content,
        dead properties,
   define new HTTP methods SHOULD specify which privileges (by defining
   new privileges, or (in mapping to ones below) are required to perform the case of
   method.  A principal with no privileges to a collection) membership of
        the resource, such as PUT and PROPPATCH.  Note resource SHOULD be
   denied any HTTP access to that state
        modification is also controlled via locking (see section 5.3 of resource, unless the principal matches

Clemm, Hopkins, Sedlar, Whitehead                           [Page 8] 
        [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 9] 
   an ACE constructed using the use DAV:all, DAV:authenticated, or
   DAV:unauthenticated pseudo-principals (see Section 5.4.1).

   Privileges may be containers of PROPFIND 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
        retrieve the DAV:acl property granting or
   denying each 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 aggregated privileges individually.  For example,
   an implementation may define add-member and remove-member privileges
   that control the
        use of PROPFIND ability to retrieve the DAV:current-user-privilege-set
        property add and remove an internal member of a
   collection.  Since these privileges control the resource.

        Clients are intended to use this property ability to visually indicate
        in their UI items that are dependent on update the permissions
   state of a
        resource, for example, collection, these privileges would be aggregated by graying out resources that are not
        writeable.

        This the
   DAV:write privilege is separate from DAV:read-acl because there is on a
        need to allow most users access to the privileges permitted the
        current user (due to its use in creating collection, and granting the UI), while DAV:write
   privilege on a collection would also grant the
        full ACL contains information that add-member and remove-
   member privileges.

   Privileges may not be appropriate for
        the current authenticated user. As a result, have the set quality of users
        who can view the full ACL is expected to being abstract, in which case they
   cannot be much smaller than
        those who can read the current user privilege set, set in an ACE. Aggregate and hence
        distinct non-aggregate privileges are needed
   both capable of being abstract. Abstract privileges are useful for each.

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

   3.5 DAV:write-acl Privilege

        The DAV:write-acl privilege controls use of
   modeling privileges that otherwise would not be exposed via the ACL method to
        modify
   protocol. Abstract privileges also provide server implementations
   with flexibility in implementing the DAV:acl property privileges defined in this
   specification.  For example, if a server is incapable of separating
   the resource.

        <!ELEMENT write-acl EMPTY>

   3.6 DAV:all Privilege

        DAV:all is an aggregate privilege that contains read resource capability from the entire set
        of 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 apply holds
   DAV:read, and DAV:read-acl. In this way, it is possible to set the resource.

        <!ELEMENT all EMPTY>

   3.7 Aggregation of Predefined Privileges

        Server implementations are free to
   aggregate privilege, read-all, thus coupling the predefined
        privileges (defined above in Sections 3.1-3.6) subject setting of DAV:read
   and DAV:read-acl, but it is not possible to the
        following limitations:

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 9] 
        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, set 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,
   DAV:read-acl individually. Since aggregate privileges can be
   abstract, it is also possible to use abstract privileges to group or DAV:write-acl.

        DAV:write
   organize non-abstract privileges. Privilege containment loops are not
   allowed, hence a privilege MUST NOT contain DAV:read, DAV:read-acl, or DAV:read-
        current-user-privilege-set. itself. For example,
   DAV:read MUST NOT cannot contain DAV:write, or DAV:write-acl.

   4  PRINCIPAL PROPERTIES

        Principals are manifested DAV:read.

   The set of privileges that apply to clients as an HTTP resource,
        identified by a URL.  A principal MUST have a DAV:displayname
        property (defined in Section 13.2 particular resource may vary
   with the DAV:resourcetype of [RFC2518]), 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
        DAV:resourcetype property particular resource.
   The access permissions on null resources (defined in [RFC2518],
   Section 13.9 of
        [RFC2518]).  Additionally, a principal MUST report 3) are solely those they inherit (if any), and they are not
   discoverable (i.e., the
        DAV:principal empty XML element access control properties specified in
   Section 5 are not defined on null resources). On the value of the
        DAV:resourcetype property in addition transition from
   null 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 stateful resource, the following additional property for a
        principal. Since it is expensive, for many servers, to retrieve initial access control information, list is set by
   the name and server's default ACL value of this property
        SHOULD NOT be returned by a PROPFIND allprop request (as policy (if any).

   Server implementations MAY define new privileges beyond those defined
   in Section 12.14.1 of [RFC2518]).

   4.1 DAV:alternate-URL

        This protected property, if non-empty, contains this specification. Privileges defined by individual

Clemm, Hopkins, Sedlar, Whitehead                          [Page 10] 
   implementations MUST NOT use the URIs of
        network resources with additional descriptive 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 principal. This property identifies one or more 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. Two potential uses for this property
        are to store an ldap [RFC2255] or mailto [RFC2368] scheme URL.
        Support for this property is REQUIRED,
   state of the resource, including the resource's properties. Affected
   methods include GET and PROPFIND.  Additionally, the value is empty
        if no alternate URL exists for read privilege
   MAY control the principal. . OPTIONS method.

     <!ELEMENT alternate-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 read EMPTY>

3.2 DAV:write Privilege

   The write privilege controls methods that modify the content, dead
   properties, using or (in the PROPFIND method.
        Since it is expensive, for many servers, to retrieve access

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 10] 
        control information, case of a PROPFIND allprop request (as defined in
        Section 12.14.1 collection) membership of [RFC2518]) SHOULD NOT return the names
   resource, such as PUT and
        values PROPPATCH.  Note that state modification is
   also controlled via locking (see section 5.3 of the properties defined in this section.

        HTTP resources [WEBDAV]), so
   effective write access requires that support the WebDAV Access Control Protocol
        MUST contain the following properties. Null, both write privileges and lock-null
        resources (described in Section 7.4 write
   locking requirements are satisfied.

     <!ELEMENT write EMPTY>

3.3 DAV:read-acl Privilege

   The DAV:read-acl privilege controls the use of [RFC2518]) MUST NOT
        contain PROPFIND to retrieve
   the following properties:

   5.1 DAV:owner

        This protected DAV:acl 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.,

     <!ELEMENT read-acl EMPTY>

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

   The DAV:read-current-user-privilege-set privilege controls the owner frequently has permanent DAV:write-acl privilege),
        clients might display use of
   PROPFIND to retrieve the resource owner DAV:current-user-privilege-set property of
   the resource.

   Clients are intended to use this property to visually indicate in
   their user
        interface.

        <!ELEMENT owner (href)>

   5.1.1 Example: Retrieving DAV:owner

        This example shows a client request for UI items that are dependent on the value permissions of the
        DAV:owner property a resource,
   for example, by graying out resources that are not writeable.

   This privilege is separate from DAV:read-acl because there is a collection resource with URL
        http://www.webdav.org/papers/. The principal making need
   to allow most users access to the request
        is 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 using Digest authentication. The value
   user. As a result, the set of
        DAV:owner is users who can view the URL http://www.webdav.org/_acl/users/gstein,
        wrapped in full ACL is
   expected to be much smaller than those who can read 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:owner/>
        </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:"> current user
   privilege set, and hence distinct privileges are needed for each.

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 11] 
           <D:response>
              <D:href>http://www.webdav.org/papers/</D:href>
              <D:propstat>
                 <D:status>HTTP/1.1 200 OK</D:status>
                 <D:prop>
                    <D:owner>
                     <D:href>
                       http://www.webdav.org/_acl/users/gstein
                     </D:href>
                    </D:owner>
                 </D:prop>
              </D:propstat>
           </D:response>
        </D:multistatus>

   5.1.2 Example: An Attempt to Set DAV:owner 

3.5 DAV:write-acl Privilege

   The following example shows a client request DAV:write-acl privilege controls use of the ACL method to modify
   the
        value of the DAV:owner DAV:acl property on of the resource with URL
        http://www.webdav.org/papers/. Since DAV:owner resource.

     <!ELEMENT write-acl EMPTY>

3.6 DAV:all Privilege

   DAV:all is a protected
        property, the server responds with a 207 (Multi-Status)
        response an aggregate privilege that contains a 403 (Forbidden) status code for the
        act of setting DAV:owner. [RFC2518], Section 8.2.1 describes
        PROPPATCH status code information, and Section 11 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

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 12] 
        <?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:status>HTTP/1.1 403 Forbidden</D:status>
                 <D:prop><D:owner/></D:prop>
              </D:propstat>
              <D:responsedescription>Failure to entire set protected property
        (DAV:owner)
              </D:responsedescription>
           </D:response>
        </D:multistatus>

   5.2 DAV:supported-privilege-set

        This is a protected property that identifies the of
   privileges
        defined for that can be applied to the resource.

     <!ELEMENT supported-privilege-set (supported-privilege*)>

        Each privilege appears as an XML element, where aggregate
        privileges list as sub-elements all EMPTY>

3.7 Aggregation of Predefined Privileges

   Server implementations are free to aggregate the predefined
   privileges that they
        aggregate.

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

        An abstract privilege of a resource (defined above in Sections 3.1-3.6) subject to the
   following limitations:

   DAV:read-acl MUST NOT be used in an ACE
        for that resource. Servers contain DAV:read, DAV:write, DAV:write-acl, or
   DAV:read-current-user-privilege-set.

   DAV:write-acl MUST fail an attempt to set an
        abstract privilege.

        <!ELEMENT abstract EMPTY> 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 description is principal MUST have a human-readable description DAV:displayname property (defined
   in Section 13.2 of what this
        privilege controls access to.

        <!ELEMENT description #PCDATA>

        It is envisioned that [RFC2518]), and a WebDAV ACL-aware administrative client
        would list the supported privileges DAV:resourcetype property
   (defined in Section 13.9 of [RFC2518]).  Additionally, a dialog box, and allow principal
   MUST report the user to choose non-abstract privileges to apply DAV:principal empty XML element in an ACE.
        The privileges tree is useful programmatically the value of the
   DAV:resourcetype property in addition to map well-
        known privileges (defined by WebDAV or all other standards groups)
        into privileges that are supported by any particular server
        implementation. reported elements.
   For example, a collection principal would report DAV:collection and
   DAV:principal elements. The privilege tree also serves to hide
        complexity in implementations allowing large number of
        privileges to be defined by displaying aggregates 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 user. name and value of this property

Clemm, Hopkins, Sedlar, Whitehead                          [Page 13] 
   5.2.1 Example: Retrieving 12] 
   SHOULD NOT be returned by a List PROPFIND allprop request (as defined in
   Section 12.14.1 of Privileges Supported on a
         Resource [RFC2518]).

4.1 DAV:alternate-URI-set

   This example shows a client request for the DAV:supported-
        privilege-set property on protected property, if non-empty, contains the resource
        http://www.webdav.org/papers/. The value URIs of network
   resources with additional descriptive information about the DAV:supported-
        privilege-set
   principal. This property is identifies additional network resources
   (i.e., it contains one or more URIs) that may be consulted by a tree of supported privileges:

          DAV:all (aggregate, abstract)
              |
            +-- DAV:read (aggregate)
                     |
                     +-- 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:supported-privilege-set/>
        </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:status>HTTP/1.1 200 OK</D:status>
              <D:prop>
                <D:supported-privilege-set>

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 14] 
                  <D:supported-privilege>
                    <D:privilege> <D:all/> </D:privilege>
                    <D:abstract/>
                    <D:description>Any operation</D:description>
                    <D:supported-privilege>
                      <D:privilege> <D:read/> </D:privilege>
                      <D:description>Read any object</D:description>
                      <D:supported-privilege>
                        <D:privilege> <D:read-acl/> </D:privilege>
                        <D:abstract/>
                        <D:description>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>Read current user privilege set
        property</D:description>
                      </D:supported-privilege>
                    <D:supported-privilege>
                      <D:privilege> <D:write/> </D:privilege>
                      <D:description>Write any object</D:description>
                      <D:supported-privilege>
                        <D:privilege> <D:write-acl/> </D:privilege>
                        <D:description>Write ACL</D:description>
                        <D:abstract/>
                      </D:supported-privilege>
                    </D:supported-privilege>
                  </D:supported-privilege>
                </D:supported-privilege-set>
              </D:prop>
            </D:propstat>
          </D:response>
        </D:multistatus>

   5.3 DAV:current-user-privilege-set

        DAV:current-user-privilege-set is
   client to gain additional knowledge concerning a protected principal. One
   expected use for this property
        containing is the exact set storage of privileges (as computed by the
        server) granted to the currently authenticated HTTP user.
        Aggregate privileges and their contained privileges are listed. an ldap [RFC2255]
   scheme URL. A user-agent can encountering an ldap URL could use the value of this property to adjust its
        user interface LDAP
   [RFC2589] to make actions inaccessible (e.g., by graying
        out a menu item or button) retrieve additional machine-readable directory
   information about the principal, and display that information in its
   user interface. Support for which this property is REQUIRED, and the current principal does
        not have permission. This value
   is particularly useful empty if no alternate URI exists for an access
        control user interface, which can be constructed without
        knowing the ACE combining semantics of the server. principal.

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

4.2 DAV:principal-URL

    This protected property is also useful for determining what operations contains the
        current principal can perform, without having URL that MUST be used to actually
        execute
   identify this principal in an operation.

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

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 15] ACL request.

     <!ELEMENT privilege ANY>

        If the current user is granted principal-URL (href)>

5  ACCESS CONTROL PROPERTIES

   This specification defines a specific privilege, that
        privilege must belong to the set number of privileges that new properties for WebDAV
   resources.  Access control properties may be set
        on this resource. Therefore, each element in retrieved just like
   other WebDAV properties, using the DAV:current-
        user-privilege-set property MUST identify PROPFIND method.   Since it is
   expensive, for many servers, to retrieve access control information,
   a non-abstract
        privilege from the DAV:supported-privilege-set property.

   5.3.1 Example: Retrieving PROPFIND allprop request (as defined in Section 12.14.1 of
   [RFC2518]) SHOULD NOT return the User's Current Set names and values of Assigned
         Privileges

        Continuing the example from Section 5.2.1, properties
   defined in this example shows a
        client requesting section.

   HTTP resources that support the DAV:current-user-privilege-set property
        from WebDAV Access Control Protocol MUST
   contain the resource with URL http://www.webdav.org/papers/. The
        username 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 making the request is ôkhareö, and
        Digest authentication is used in the request. The principal
        with username ôkhareö 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), as being
   the principal with username ôkhareö can read "owner" of the ACL
        property, and resource. Since the DAV:current-user-privilege-set property.
        However, owner of a resource often has
   special access control capabilities (e.g., the DAV:all, DAV:read-acl, owner frequently has
   permanent DAV:write-acl and DAV:read-
        current-user-privilege-set privileges are not listed privilege), clients might display the
   resource owner in their user interface.

     <!ELEMENT owner (href)>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 13] 

5.1.1 Example: Retrieving DAV:owner

   This example shows a client request for the value of DAV:current-user-privilege-set, since (for this
        example) they are abstract privileges. DAV:write is not listed
        since the principal DAV:owner
   property from a collection resource with username ôkhareö URL
   http://www.webdav.org/papers/. The principal making the request is not listed
   authenticated using Digest authentication. The value of DAV:owner is
   the URL http://www.webdav.org/_acl/users/gstein, wrapped in an
        ACE granting that principal write permission. 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="khare",
           realm="khare@webdav.org", username="jim",
        realm="jim@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

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

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 16]
           <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:prop>
                <D:current-user-privilege-set>
                  <D:privilege> <D:read/> </D:privilege>
                </D:current-user-privilege-set>
              </D:prop>
           </D:propstat>
        </D:response>
     </D:multistatus>

   5.4 DAV:acl

        This

Clemm, Hopkins, Sedlar, Whitehead                          [Page 14] 

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
   property, the server responds with a 207 (Multi-Status) response that specifies
   contains a 403 (Forbidden) status code for the list act of access
        control entries (ACEs), which define what principals are 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 get
        what set protected property
     (DAV:owner)
              </D:responsedescription>
           </D:propstat>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 15] 
        </D:response>
     </D:multistatus>

5.2 DAV:supported-privilege-set

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

     Each DAV:ace element specifies the set of privilege appears as an XML element, where aggregate
     privileges to be
        either granted or denied to a single principal.  If list as sub-elements all of the DAV:acl
        property is empty, no principal is granted any privilege. privileges that they
     aggregate.
     <!ELEMENT ace (principal, (grant|deny), protected?,
        inherited?)>

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

   An abstract privilege MUST NOT be used in an ACE Principal

        The DAV:principal element identifies the principal for that resource.
   Servers MUST fail an attempt to which
        this ACE applies. set an abstract privilege.

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

        The current user matches DAV:href only if that user abstract EMPTY>

   A description is
        authenticated as being (or being a member of) human-readable description of what this privilege
   controls access to. Servers MUST indicate the principal
        identified by human language of 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>

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

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 17]
   description using the xml:lang attribute and SHOULD consider the HTTP
   Accept-Language request header when selecting one of multiple
   available languages.

     <!ELEMENT unauthenticated EMPTY>

        DAV:all description #PCDATA>

   It is envisioned that a WebDAV ACL-aware administrative client would
   list the union of DAV:authenticated, and
        DAV:unauthenticated. For supported privileges in a given request, dialog box, and allow the user matches
        either DAV:authenticated, 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 DAV:unauthenticated, but not both
        (that is, DAV:authenticated and DAV:unauthenticated other standards groups) into privileges that are
        disjoint sets).
   supported by any particular server implementation.  The current user matches a DAV:property principal privilege
   tree also serves to hide complexity in a DAV:acl
        property implementations allowing large
   number of a resource only if privileges to be defined by displaying aggregates to the value
   user.

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

   This example shows a client request for the identified DAV:supported-privilege-
   set property of that resource contains at most one DAV:href XML
        element, on the URI resource http://www.webdav.org/papers/. The value
   of DAV:href identifies a principal, and the current user DAV:supported-privilege-set property 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 tree of the resource.

        <!ELEMENT property ANY>

        The current user matches DAV:self in a DAV:acl property of the
        resource only if that resource supported
   privileges:

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 16] 
                  |
                  +-- DAV:read-acl (abstract)
                  +-- DAV:read-current-user-privilege-set (abstract)
           +-- DAV:write (aggregate)
                  |
                  +-- DAV:write-acl (abstract)

   This privilege tree is a principal object not normative, and the 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>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 17] 
                   <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 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 protected property containing the
   exact set of privileges to be either (as computed by the server) granted or denied to the specified
        principal.
   currently authenticated HTTP user. Aggregate privileges and their
   contained privileges are listed. A DAV:grant or DAV:deny element of user-agent can use the DAV:acl value of
   this property to adjust its user interface to make actions
   inaccessible (e.g., by graying out a
        resource MUST only contain non-abstract elements specified in menu item or button) for which
   the DAV:supported-privilege-set of that resource.

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

   5.4.3 ACE Protection

        If an ACE contains a DAV:protected element, current principal does not have permission. This is particularly
   useful for an ACL request access control user interface, which can be constructed
   without that ACE MUST fail.

        <!ELEMENT protected EMPTY>

   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 knowing the
        URL contained in a DAV:href element.  An inherited ACE cannot
        be modified directly, but instead the ACL on combining semantics of the resource from
        which it server. This
   property is inherited must be modified. also useful for determining what operations the current
   principal can perform, without having to actually execute an
   operation.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 18] 
        Note that ACE inheritance is not the same as ACL
        initialization.  ACL initialization defines 
     <!ELEMENT current-user-privilege-set (privilege*)>
     <!ELEMENT privilege ANY>

   If the ACL that current user is granted a
        newly created resource will use (if not specified).  ACE
        inheritance refers to an ACE specific privilege, that is logically shared - where
        an update privilege
   must belong to the resource containing an ACE will affect the ACE set of each resource that inherits privileges that ACE.  The method by which
        ACLs are initialized or by which ACEs are inherited is not
        defined by may be set on this document.

        <!ELEMENT inherited (href)>

   5.4.5
   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 a Resource's Access Control List

        Continuing the example from Sections 5.2.1 and 5.3.1, UserÆs Current Set of Assigned Privileges

   Continuing the example from Section 5.2.1, this example shows a
   client requesting the DAV:acl DAV:current-user-privilege-set 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 username 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 principal making the ômaintainersö group can
        also modify request is ôkhare", and Digest
   authentication is used in the access control list.

        ACE #2: All principals (DAV:all) are request. The principal with username
   ôkhare" has been granted the DAV:read privilege. Since (for this example) the DAV:read
   privilege contains DAV:read-
        acl the DAV:read-acl and DAV:read-current-user-privilege-set, this means all
        users (including all members of DAV:read-current-user-
   privilege-set privileges (see Section 5.2.1), the ômaintainersö group) principal with
   username ôkhare" can read the DAV:acl property ACL property, and the DAV:current-user-privilege-
        set 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="masinter",
           realm="masinter@webdav.org", username="khare",
        realm="khare@webdav.org", nonce="...",
        uri="/papers/", response="...", opaque="..."

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 19] 
        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:status>HTTP/1.1 200 OK</D:status>
           <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:href> <D:all/> </D:href>
                    </D:principal>
                    <D:grant>
             <D:current-user-privilege-set>
               <D:privilege> <D:read/> </D:privilege>
                    </D:grant>
                  </D:ace>
                </D:acl>
             </D:current-user-privilege-set>
           </D:prop>
           <D:status>HTTP/1.1 200 OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>

   5.5 DAV:acl-semantics

5.4 DAV:acl

   This is a protected property that defines specifies the ACL semantics.
        These semantics list of access
   control entries (ACEs), which define how multiple ACEs that match the current
        user are combined, what principals are to get what
   privileges for this resource.

     <!ELEMENT acl (ace*)>

   Each DAV:ace element specifies the constraints on how ACEs can set of privileges to be
        ordered, and which principals must have an ACE. A client user
        interface could use the value of this property to provide
        feedback either
   granted or denied to a human operator concerning single principal.  If the impact of proposed
        changes to an ACL. Alternately, a client can use this DAV:acl 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
   empty, no principal is not practical granted any privilege.

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

5.4.1 ACE Principal

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

     <!ELEMENT principal ((href)
      | all implementations to use
        the same ACL semantics, the DAV:acl-semantics | authenticated | unauthenticated
      | property | self)>

   The current user matches DAV:href only if that user is used
        to identify the ACL semantics for authenticated
   as being (or being a particular resource. member of) the principal identified by the URL
   contained by that DAV:href.

   The
        DAV:acl-semantics element is defined in Section 6. current user always matches DAV:all.

     <!ELEMENT all EMPTY>

   The current user matches DAV:authenticated only if authenticated.

     <!ELEMENT authenticated EMPTY>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 20] 
   5.5.1 Example: Retrieving DAV:acl-semantics

        In this example, 
   The current user matches DAV:unauthenticated only if not
   authenticated.

     <!ELEMENT unauthenticated EMPTY>

   DAV:all is the client requests 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 DAV:acl-
        semantics property. Digest authentication provides credentials
        for identified property
   of that resource contains at most one DAV:href XML element, the principal operating URI
   value of DAV:href identifies a principal, and the client. In this current user is
   authenticated as being (or being a member of) that principal.  For
   example, if the
        ACE combination semantics are DAV:first-match, described in
        Section 6.1.1, DAV:property element contained <DAV:owner/>, the ACE ordering semantics are not specified
        (some value other than DAV:deny-before-grant, described in
        Section 6.2.1),
   current user would match the DAV:allowed-ace element states that DAV:property principal only
        one ACE is permitted for each principal, and an ACE describing if the privileges granted
   current user is authenticated as matching the DAV:all principal must exist identified by
   the DAV:owner property of the resource.

     <!ELEMENT property ANY>

   The current user matches DAV:self 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:acl-semantics/>
        </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:status>HTTP/1.1 200 OK</D:status>
              <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>

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 21] 
                    <D:all/>
                  </D:required-principal>
                </D:acl-semantics>
              </D:prop>
            </D:propstat>
          <D:response>
        </D:multistatus>

   5.6 DAV:principal-collection-set

        This protected a DAV:acl property contains zero, one, or more URLs of the
   resource only if that
        identify resource is a collection principal. It principal object and the current
   user is expected authenticated as being that
        implementations of this protocol will typically use principal or a
        relatively small number member of locations in the URL namespace for
        principal, 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 that
   principal collection.

     <!ELEMENT self EMPTY>

5.4.2 ACE Grant and
        collection principals. An access control protocol user agent
        could use Deny

   Each DAV:grant or DAV:deny element specifies the contents set of DAV:principal-collection-set privileges to
   be either granted or denied to query the DAV:displayname property (specified in Section 13.2 specified principal.  A DAV:grant
   or DAV:deny element of
        [RFC2518]) the DAV:acl 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 resource MUST only contain
   non-abstract elements specified in the DAV:principal-collection-set MAY be located on
        different hosts from the DAV:supported-privilege-set of
   that resource. The URLs in DAV:principal-
        collection-set SHOULD be http or https scheme URLs. For
        security and scalability reasons, a

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

5.4.3 ACE Protection

   A server MAY report only a
        subset of the entire set of known collection principals, and
        therefore clients should not assume they have retrieved indicates an
        exhaustive listing. Additionally, a server MAY elect to report
        none of ACE is protected by including the collection principals it knows about, DAV:protected
   element in which case
        the property value would be empty.

   5.6.1 Example: Retrieving DAV:principal-collection-set

        In this example, the client requests ACE. If the value ACL of the
        DAV:principal-collection-set property on the collection a 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 an ACE with two
        separate PROPFIND requests a
   DAV:protected element, an attempt to retrieve remove that ACE from the DAV:displayname ACL
   MUST fail..

     <!ELEMENT protected EMPTY>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 22] 
        property 21] 

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 members of URL
   contained in a DAV:href element.  An inherited ACE cannot be modified
   directly, but instead the two collections (/_acl/users/
        and /_acl_groups/). This information could ACL on the resource from which it is
   inherited must be used when
        displaying modified.

   Note that ACE inheritance is not the same as ACL initialization.  ACL
   initialization defines the ACL that 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:principal-collection-set/>
        </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:status>HTTP/1.1 200 OK</D:status>
              <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:propstat>
          </D:response>
        </D:multistatus>

   5.7 Example: PROPFIND newly created resource will use
   (if not specified).  ACE inheritance refers to retrieve access control properties

        The following example shows how access control information can
        be retrieved by using the PROPFIND method an ACE that is
   logically shared - where an update to fetch the values
        of resource containing an ACE
   will affect the DAV:owner, DAV:supported-privilege-set, DAV:current-
        user-privilege-set, 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 properties.

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 23] 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 /top/container/ /papers/ HTTP/1.1
     Host: www.foo.org www.webdav.org
     Content-type: text/xml; charset="utf-8"
     Content-Length: xxx
     Depth: 0
     Authorization: Digest username="ejw",
           realm="users@foo.org", username="masinter",
        realm="masinter@webdav.org", nonce="...",
           uri="/top/container/",
        uri="/papers/", response="...", opaque="..."

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 22] 
     <D:propfind xmlns:D="DAV:">
          <D:owner/>
          <D:supported-privilege-set/>
          <D:current-user-privilege-set/>
       <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:"
           xmlns:A="http://www.webdav.org/acl/"> xmlns:D="DAV:">
       <D:response>
          <D:href>http://www.foo.org/top/container/</D:href>
         <D:href>http://www.webdav.org/papers/</D:href>
         <D:propstat>
          <D:status>HTTP/1.1 200 OK</D:status>

           <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>Any operation</D:description>
                <D:supported-privilege>
                  <D:privilege> <D:read/> </D:privilege>
                  <D:description>Read any object</D:description>
                </D:supported-privilege>
                <D:supported-privilege>
             <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:abstract/>
                  <D:description>Write any object</D:description>
                  <D:supported-privilege>
                    <D:privilege> <A:create/> </D:privilege>
                    <D:description>Create an object</D:description>
                  </D:supported-privilege>
                  <D:supported-privilege>

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 24]
                 </D:grant>
               </D:ace>
               <D:ace>
                 <D:principal>
                   <D:all/>
                 </D:principal>
                 <D:grant>
                   <D:privilege> <A:update/> <D:read/> </D:privilege>
                    <D:description>Update
                 </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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 23] 
   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"

Clemm, Hopkins, Sedlar, Whitehead                          [Page 24] 
     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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 25] 
   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 <<

Clemm, Hopkins, Sedlar, Whitehead                          [Page 26] 
     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>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 27] 
     </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>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 28] 
             </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.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 29] 
   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?)>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 30] 

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)? >

Clemm, Hopkins, Sedlar, Whitehead                          [Page 31] 

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 object</D:description>
                  </D:supported-privilege>
                  <D:supported-privilege>
                    <D:privilege> <A:delete/> </D:privilege>
                    <D:description>Delete 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 object</D:description>
                  </D:supported-privilege>
                </D:supported-privilege>
                <D:supported-privilege>
                  <D:privilege> <D:read-acl/> </D:privilege>
                  <D:description>Read ACE defined in the ACL</D:description>
                </D:supported-privilege>
                <D:supported-privilege>
                  <D:privilege> <D:write-acl/> </D:privilege>
                  <D:description>Write ACL.

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

   For example, 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> 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: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:required-principal>

7  ACCESS CONTROL AND EXISTING METHODS

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 25] 
              </D:ace> </D:acl>
            </D:prop>
          </D:propstat> </D:response> </D:multistatus>

        The value of 32] 

7.1 OPTIONS

   If the DAV:owner property is server supports access control, it MUST return "access-
   control" as a single DAV:href XML
        element containing the URL of field in the principal DAV response header from an OPTIONS
   request on any resource implemented by that owns 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
        resource.

        The value of example, 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 OPTIONS response indicates that the
        current authenticated user only has server
   supports access control and that /foo.html can have its access
   control list modified by the ability ACL method.

7.2 MOVE

   When a resource is moved from one location to read another due to a MOVE
   request, the
        resource, non-inherited and read the DAV:acl property on non-protected ACEs in 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 resource MUST NOT be modified, or the DAV:read,
        DAV:write, MOVE request
   fails. Handling of inherited and DAV:read-acl privileges. protected ACEs is intentionally
   undefined to give server implementations flexibility in how they
   implement ACE #2: inheritance and protection.

7.3 COPY

   The principals identified by the URL
        http://www.foo.org/groups/marketing/ are denied DAV:acl property on the DAV:read
        privilege.  In this example, resource at the principal URL identifies destination of a
        group, which is represented COPY
   MUST be the same as if the resource was created by a collection principal.

        ACE #3: In this ACE, an individual
   resource creation request (e.g. MKCOL, PUT). Clients wishing to
   preserve the principal is DAV:acl property across a copy need to read the DAV:acl
   property principal,
        specifically prior to the DAV:owner property. When evaluating COPY, then perform an ACL operation on the new
   resource at the destination to restore, insofar as this ACE, is possible,
   the value original access control list.

7.4 DELETE

   The precise combination of the DAV:owner property is retrieved, privileges and is
        examined resources necessary to see if it contains a DAV:href XML element. If so,
        the URL within
   permit the DAV:href element DELETE method is read, and identifies a
        principal. In this ACE, intentionally left to the owner discretion of
   each server implementation. It is granted DAV:read-acl, and
        DAV:write-acl privileges.

        ACE #4: This ACE grants the DAV:all principal (all users) envisioned that on some servers,
   DELETE will require write permission on the
        DAV:read privilege. This ACE is inherited from collection containing the
   resource
        http://www.foo.org/top/, to be deleted.  On other servers, it might also require
   write permission on the parent collection of this
        resource. resource being deleted.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 26] 
   6  ACL SEMANTICS

        The ACL semantics define how multiple ACEs 33] 

7.5 LOCK

   A lock on a resource ensures that match the
        current user are combined, what are only the constraints on how ACEs lock owner can be ordered, and which principals must have an ACE.

        <!ELEMENT acl-semantics acl-sem*>

        <!ELEMENT acl-sem (ace-combination, ace-ordering, allowed-ace,
        required-principal*)>

   6.1 ACE Combination

        The DAV:ace-combination element defines how privileges from
        multiple modify ACEs
   that match the current user will be combined to
        determine are not inherited and not protected  (these are the access privileges for that user.  Multiple only ACEs
        may match the same user because the same principal
   that a client can appear
        in multiple modify with an ACL request). A lock does not
   protect inherited or protected ACEs, because multiple principals can identify the
        same user, and because one principal can be since 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 client cannot modify
   them with an ACL request on that resource.

8  ACCESS CONTROL METHODS

8.1 ACL

   The ACEs are evaluated in ACL method modifies the order in which they appear in access control list (which can be read
   via the
        ACL.  If DAV:acl property) of a resource.  Specifically, the first ACE ACL
   method only permits modification to ACEs that matches the current user does are not
        grant inherited, and
   are not protected. An ACL method invocation modifies 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 non-
   inherited and non-protected ACEs are evaluated in a resourceÆs access control list
   to exactly match the order in which they appear ACEs contained within in the
        ACL.  If an evaluated ACE denies a privilege needed for the
        request, DAV:acl XML element
   (specified in Section 5.4) of the request body. An ACL request body
   MUST fail.  If all contain only one DAV:acl XML element. Unless the non-inherited
   and non-protected ACEs have been
        evaluated without of the user being granted all privileges needed
        for DAV:acl property of the resource can be
   updated to be exactly the value specified in the ACL request, the ACL
   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"

   It is one
        whose principal identifies possible that the ACEs visible to the current user.  A "group ACE" is
        one whose principal is a collection that contains user in the
   DAV:acl property may only be a principal
        that identifies portion of 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 complete set of ACEs on
   that resource. If this is granted by a group ACE and not denied by the case, an
        individual or group ACE.  A ACL request MUST fail if any only modifies the
   set of its
        needed privileges are ACEs visible to the current user, and does not granted.

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 27] 
        <!ELEMENT specific-deny-overrides-grant EMPTY>

   6.2 ACE Ordering

        The DAV:ace-ordering element defines affect any non-
   visible ACE.

   In order to avoid overwriting DAV:acl changes by another client, a constraint
   client SHOULD acquire a WebDAV lock on how the
        ACEs can be ordered in resource before retrieving
   the ACL.

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

   6.2.1 DAV:deny-before-grant ACE Ordering

        This element indicates DAV:acl property of a resource 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 it intends on what
        kinds of ACEs updating.

     Implementation Note: Two common operations are allowed in to add or remove 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 from an existing access control list. To accomplish this, 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
     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 with deny clauses are not
        allowed.

        <!ELEMENT grant-only EMPTY>

   6.4 Required Principals

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

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

        For example, request body of the following element requires that ACL method.

8.1.1 ACL Preconditions

   An implementation MAY enforce one or more of the following
   constraints on an ACL
        contain request.  If the constraint is violated, a DAV:owner property ACE:

        <D:required-principal xmlns:D="DAV:">
          <D:property> <D:owner/> </D:property>
        </D:required-principal> 403
   (Forbidden) response MUST be returned and the indicated XML element
   MUST be returned as the top level element in an XML response body.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 28] 
   7  ACCESS CONTROL AND EXISTING METHODS

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

   7.1 OPTIONS

        If the server supports access control, it MUST return "access-
        control" as a field 34] 
   <DAV:ace-conflict/>: A conflict exists between two or more ACEs
   submitted in the DAV response header from ACL request.

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

        In this example,
   request submitted an ACE denying DAV:write to the OPTIONS response indicates that same principal.

   <DAV:inherited-ace-conflict/>: A conflict exists between an ACE in
   the server
        supports access control ACL request and that /foo.html can have its access
        control list modified by an inherited ACE on the resource. For example, if
   the ACL method.

   7.2 MOVE

        When a resource is moved inherits an ACE from one location to another due its parent collection granting
   DAV:write to a
        MOVE request, given principal, then it would be an inherited ACE
   conflict if the non-inherited ACEs in ACL request submitted an ACE denying DAV:write to the DAV:acl property
   same principal. Note that reporting of
        the resource MUST NOT this error will be modified,
   implementation-dependent. Implementations have the choice to either
   report this error, or to allow the MOVE request fails.

   7.3 COPY

        The DAV:acl property ACE to be set, and then let normal
   ACE evaluation rules determine whether the new ACE has any impact on
   the resource at privileges available to a specific principal.

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

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

   <DAV:principal-only-one-ace/>: For implementations that have the same as if
   DAV:principal-only-one-ace constraint (defined in Section 6.3.1),
   this XML element indicates that fulfilling the resource was created by an
        individual resource creation request (e.g. MKCOL, PUT).

   8  ACCESS CONTROL METHODS

   8.1 ACL

        The ACL method modifies request would
   result in multiple ACEs for one or more principals.

   <DAV:grant-only/>: For implementations that have the access control list (which can be
        read via DAV:grant-only
   constraint (defined in Section 6.3.2), this XML element indicates the DAV:acl property)
   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 a resource.  Specifically, the privileges in the ACL method only permits modification to ACEs that are
   request is not
        inherited, and are supported by the resource.

   <DAV:required-principal/>: One or more required principals (see
   Section 6.4) would not protected. An ACL method invocation
        modifies all non-inherited and non-protected ACEs be present in a
        resource's the access control list to exactly match the ACEs
        contained within in after
   processing the DAV:acl ACL request. The DAV:required-principal XML element (specified
   MUST contain a list of the missing principal(s), following the syntax
   specified in Section 5.4) 6.4.

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 35] 
   <DAV:allowed-principal/>: One or more of the principal URLs in the
   ACL request body MUST
        contain is not allowed in an ACE. For example, a server where
   only one DAV:acl XML element. Unless authenticated principals can access resources would not allow
   the non-inherited 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>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 29] 
        and non-protected ACEs of the DAV:acl property of the resource
        can be updated 36] 
     </D:acl>

     >> Response <<

     HTTP/1.1 200 OK

8.1.3 Example: ACL method failure due to be exactly protected ACE conflict

   In the value specified following request, user "fielding", authenticated by
   information in the ACL
        request, Authorization header, attempts to deny the ACL request MUST fail.

        It is possible that
   principal identified by the ACEs visible to URL http://www.foo.org/users/esedlar
   (i.e., the current user in "esedlar") write privileges. Prior to the request,
   the DAV:acl property may only be on the resource contained a portion of protected ACE (see
   Section 5.4.3) granting DAV:owner the complete set of
        ACEs on that resource. If this DAV:read and DAV:write
   privileges. The principal identified by URL
   http://www.foo.org/users/esedlar is the case, an ACL request only
        modifies the set owner 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 resource. The
   ACL method invocation fails because the resource
        before retrieving submitted ACE conflicts with
   the DAV:acl property protected ACE, thus violating the semantics of a resource that it
        intends on updating.

          Implementation Note: Two common operations are 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:"/>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 37] 

8.1.4 Example: ACL method failure due to add or
          remove an inherited ACE from an existing access control list. To
          accomplish this, a client uses the PROPFIND method to
          retrieve conflict

   In the value of following request, user "ejw", authenticated by information in
   the DAV:acl property, then parses Authorization header, tries to change the
          returned access control list to remove all on
   the resource http://www.foo.org/top/index.html. This resource has two
   inherited and
          protected ACEs (these ACEs are tagged with ACEs.

   Inherited ACE #1 grants the DAV:inherited principal identified by URL
   http://www.foo.org/users/ejw (i.e., the user "ejw")
   http://www.foo.org/privs/write-all and DAV:protected XML elements). In 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 remaining DAV:read privilege.

   The request attempts to set of non-
          inherited, non-protected ACEs, the client can add or remove
          one or more ACEs before submitting a (non-inherited) ACE, denying the final ACE set in
   principal identified by the
          request body of URL http://www.foo.org/users/ejw (i.e.,
   the ACL method.

   8.1.1 ACL Preconditions

        An implementation MAY enforce one or more of user ôejw") DAV:write permission. This conflicts with inherited
   ACE #1. Note that the following
        constraints on decision to report an ACL request.  If the constraint inherited ACE conflict is violated,
        a 403 (Forbidden) response MUST be returned and
   specific to this server implementation. Another server implementation
   could have allowed the indicated
        XML element MUST new ACE to be returned as the top level element in an XML
        response body.

        <DAV:ace-conflict/>: A conflict exists between two or more ACEs
        submitted in set, and then used normal ACE
   evaluation rules to determine whether the ACL request.

        <DAV:protected-ace-conflict/>: A conflict exists between an new ACE
        in has any impact on
   the privileges available to a principal.

     >> Request <<

     ACL request /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" ?>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 38] 
     <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 protected ACE on the resource. For single ACE.

   In this example, if user "ygoland", authenticated by information in the resource has a protected ACE granting DAV:write
   Authorization header, tries to a given principal, then it would be a protected ACE conflict
        if change the access control list on the
   resource http://www.foo.org/diamond/engagement-ring.gif. The ACL
   request submitted an ACE denying DAV:write includes a single, syntactically and semantically incorrect
   ACE, which attempts to grant the
        same principal.

        <DAV:inherited-ace-conflict/>: A conflict exists between an ACE
        in collection principal identified by
   the ACL request URL http://www.foo.org/users/friends/ DAV:read privilege and an inherited ACE on deny
   the resource. For
        example, if principal identified by URL http://www.foo.org/users/ygoland-so
   (i.e., the resource inherits an ACE from its parent
        collection granting DAV:write user "ygoland-so") DAV:read privilege. However, it is
   illegal to have multiple principal elements, as well as both a given principal, then it
        would be an inherited ACE conflict 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 ACL request submitted
        an ACE denying DAV:write had been divided into two ACEs, one to
   grant, and one to deny, the same principal. Note that
        reporting of this error will be implementation-dependent. request would have been syntactically
   well formed.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 30] 
        Implementations have 39] 

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 choice to either report this error, PROPFIND method, which returns the value of one or
        to allow more
   named properties, the ACE to be set, and then let normal ACE evaluation
        rules determine whether REPORT method can involve more complex
   processing. REPORT is valuable in cases where the new ACE server has any impact on the
        privileges available access
   to a specific principal.

        <DAV:too-many-aces/>: An implementation MAY limit the number all of
        ACEs in an ACL.  However, ACL-compliant servers MUST support at
        least one ACE granting privileges the information needed to perform the complex request (such
   as a single principal, query), and
        one ACE granting privileges where it would require multiple requests for the
   client 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 retrieve the DAV:principal-only-one-ace constraint (defined 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 Section
        6.3.1), this XML element indicates the
   DAV:acl property that fulfilling are identified by http(s) URLs, the value of
   the ACL
        request would result properties specified in the REPORT request body. In the case
   where a principal URL appears multiple ACEs times, the DAV:acl-principal-
   props report MUST return the properties for one or more
        principals.

        <DAV:grant-only/>: For implementations that have the DAV:grant- principal only constraint (defined in Section 6.3.2), this XML element
        indicates the once.

   Marshalling

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

     <!ELEMENT acl-principal-props ANY>
     ANY value: a sequence of one or more deny ACEs.

        <DAV:required-principal>: One or more required principals (see elements, with at most one
     DAV:prop element.
     prop: see RFC 2518, Section 6.4) would not 12.11

   The response body for a successful request MUST be present in a DAV:multistatus
   XML element (i.e., the access control list
        after processing response uses the ACL request. same format as the response
   for PROPFIND).

     multistatus: see RFC 2518, Section 12.9

   The DAV:required-principal
        XML element response body for a successful DAV:acl-principal-props REPORT
   request MUST contain a list of the missing principal(s),
        following the syntax specified DAV:response element for each principal
   identified by an http(s) URL listed in Section 6.4.

   8.1.2 Example: a DAV:principal XML element of
   an ACE within the ACL method

        In DAV:acl property of the following example, user "fielding", authenticated resource identified by
        information in the Authorization header, grants 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.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 40] 
   ACE #2: The principal identified by the URL http://www.foo.org/users/esedlar  (i.e.,
        the
   http://www.webdav.org/people/gstein (the user "esedlar") read 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 write privileges, grants DAV:read-acl privileges.

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

   >> Request <<

        ACL /top/container/

     REPORT /index.html HTTP/1.1
     Host: www.foo.org www.webdav.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
     <D:acl-principal-props xmlns:D="DAV:">
          <D:ace>
       <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>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 31] 
            <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> </D:acl>

        >> Response <<

        HTTP/1.1 41] 
             <D:displayname>Site authors</D:displayname>
           </D:prop>
           <D:status>HTTP/1.1 200 OK

   8.1.3 Example: ACL method failure due OK</D:status>
         </D:propstat>
       </D:response>
     </D:multistatus>

9.3 DAV:principal-match REPORT

   The DAV:principal-match REPORT is used to protected ACE conflict identify all members of a
   collection that match the current user. In particular, if the following request, user "fielding", authenticated by
        information in
   collection contains principals, the Authorization header, attempts report can be used to deny 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 identified (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 URL
        http://www.foo.org/users/esedlar  (i.e., the user "esedlar")
        write privileges. Prior to the request, 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 DAV:acl property report
   operates on the resource contained a protected ACE (see Section 5.4.3)
        granting DAV:owner collection in the DAV:read and DAV:write privileges. Request-URI, as well as all child
   collections, grandchild collections, etc.

   Marshalling:

   The
        principal identified by URL http://www.foo.org/users/esedlar 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 owner value 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" ?>

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 32] 
        <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" ?>
        <DAV:protected-ace-conflict/>

   8.1.4 Example: ACL method failure due to named property typically contains
     an inherited ACE conflict

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

        Inherited ACE #1 grants current user. When the principal identified by URL
        http://www.foo.org/users/ejw (i.e., DAV:principal-property
   element is used, a match occurs if the current 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 same as
   the principal identified by the URL http://www.foo.org/users/ejw
        (i.e., the user ôejwö) DAV:write permission. This conflicts
        with inherited ACE #1. Note that URI found in the decision to report an
        inherited ACE conflict is specific to this server
        implementation. Another server implementation could have
        allowed DAV:href element of
   the new ACE to be set, and then used normal ACE
        evaluation rules to determine whether property identified by the new ACE has any
        impact on DAV:principal-property element. When
   the privileges available to DAV:self element is used in 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", DAV:principal-match report issued
   against a collection principal, it matches a child of the collection

Clemm, Hopkins, Sedlar, Whitehead                          [Page 33] 
           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" ?>
        <DAV:inherited-ace-conflict/>

   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 42] 
   principal if that child (a principal resource) identifies the same
   principal as the current user.

   If DAV:prop is specified in the Authorization header, tries to change request body, the access control
        list on properties
   specified in the resource http://www.foo.org/diamond/engagement-
        ring.gif. DAV:prop element MUST be reported in the
   DAV:response elements.

9.3.1 Example: DAV:principal-match REPORT

   The ACL request includes a single, syntactically and
        semantically incorrect ACE, which attempts to grant following example identifies the members of the collection principal
   identified by the URL
        http://www.foo.org/users/friends/ DAV:read privilege and deny
        the principal identified http://www.webdav.org/doc/ that are owned by URL
        http://www.foo.org/users/ygoland-so (i.e.,
   the current user. The current user "ygoland-
        so") DAV:read privilege. However, it (ôgclemm") 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. authenticated using
   Digest authentication.

   >> Request <<

        ACL /diamond/engagement-ring.gif

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

     <?xml version="1.0" encoding="utf-8" ?>
        <D:acl
     <D:principal-match xmlns:D="DAV:">
          <D:ace>
            <D:principal>

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 34] 
              <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>
       <D:principal-property>
         <D:owner/>
       </D:principal-property>
     </D:principal-match>

     >> Response <<

     HTTP/1.1 400 Bad Request 207 Multi-Status
     Content-Type: text/xml; charset="utf-8"
     Content-Length: 0

        Note that if 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>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 43] 

9.4 DAV:principal-property-search REPORT

   The DAV:principal-property-search REPORT performs a substring search
   on the request had been divided into two ACEs, one to
        grant, 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 one hence can include any character in the
      Unicode/ISO-10646 standard, that is, most known characters in
      human languages. Due to deny, the request would have been
        syntactically well formed.

   9  ACCESS CONTROL REPORTS

   9.1 REPORT Method

        A REPORT request idiosyncrasies of case mapping across
      human languages, implementation of caseless matching is an extensible mechanism non-
      trivial. Implementors are strongly encouraged to consult
      [CaseMap], especially Section 2.3 ("Caseless Matching"), for obtaining
        information about a resource.  Unlike a
      guidance when implementing their caseless matching algorithms.

   Marshalling:

   The DAV:principal-collection-set property of the resource property,
        which has a single value, identified
   by the value 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 report can depend on
        additional information specified collection principal resource identified in
   DAV:principal collection-set are searched.

   Servers MUST support the DAV:principal-property-search REPORT request body and on all
   principal collections identified in the REPORT request headers.

      Marshalling:

        The body value of a REPORT DAV:principal-
   collection-set property.

   The request specifies which report is being
        requested, as well as any additional information 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 be
        used 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 customize be searched and a caseless-substring element,
   containing the report. search string.

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

     <!ELEMENT caseless-substring #PCDATA >

Clemm, Hopkins, Sedlar, Whitehead                          [Page 44] 
   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 MAY include MUST be a Depth header. 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
        requested report. search specification
   given in DAV:principal-property-search.

   If a Depth request header DAV:prop is included, specified in the response request body, the properties
   specified in the DAV:prop element MUST be a
        207 Multi-Status.

      Postconditions:

        The REPORT method MUST NOT change reported in the content or dead
        properties of any resource.
   DAV:response elements.

   Errors:

   If a Depth request header specifies a search of  a property that is included, the request not
   searchable, a 403 (Forbidden) response MUST be
        applied separately to the collection itself returned and to all members
        of the collection that satisfy
   response body MUST be a DAV:non-searchable-property element,
   containing the Depth value. unsearchable properties.

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

9.4.1 Matching

   There are several cases to consider when matching strings. The DAV:prop
        element of a DAV:response for
   easiest case is when a given resource MUST contain property value is "simple" and has only
   character information item content (see [REC-XMLINFOSET]). For
   example, the
        requested report for that resource.

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 35] 
   9.2 DAV:acl-principal-props Report

        The DAV:acl-principle-props report returns, for all principals
        in search string "julian" would match the DAV:acl DAV:displayname
   property with value "Julian Reschke". Note that are identified by http(s) URLs, the value on-the-wire
   marshalling of the properties specified DAV:displayname in the REPORT request
        body. In the this case where a principal URL appears multiple times,
        the DAV:acl-principal-props report MUST return the properties
        for that principal only once.

      Marshalling is:

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

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

        <!ELEMENT acl-principal-props ANY>
        ANY value: a sequence name 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 the property is encoded into the XML element (i.e., the response uses information
   item, and the same
        format as character information item content of the response for PROPFIND).

        multistatus: see RFC 2518, Section 12.9 property is
   "Julian Reschke".

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 45] 
     <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 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.

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

        The following example shows
   above, a DAV:acl-principal-props report
        requesting search string would be compared to the DAV:displayname property. It returns 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 value client requests the principal URLs of all users
   whose DAV:displayname for 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
        http://www.webdav.org/people/gstein meet the search
   specification, "John Doe" and
        http://www.webdav.org/groups/authors/ , but not for DAV:all,
        since this "Zygdoebert Smith". The property
   "salary" in namespace "http://www.BigCorp.com/ns/" is not an http(s) URL.

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 36] returned,
   since the principal making the request does not have sufficient
   access permissions to read this property.

   >> Request <<

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

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 46] 
           <D:displayname/>
         </D:prop>
        </D:acl-principal-props>
         <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" charset=utf-8
     Content-Length: xxxx

     <?xml version="1.0" encoding="utf-8" ?>
     <D:multistatus xmlns:D="DAV:"> xmlns:D="DAV:" xmlns:B="http://BigCorp.com/ns/">
       <D:response>
            <D:href>http://www.webdav.org/people/gstein</D:href>
         <D:href>http://www.BigCorp.com/users/jdoe</D:href>
         <D:propstat>
           <D:prop>
                <D:displayname>Greg Stein</D:displayname>
             <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.webdav.org/groups/authors/</D:href>
         <D:href>http://www.BigCorp.com/users/zsmith</D:href>
         <D:propstat>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 47] 
           <D:prop>
                <D:displayname>Site authors</D:displayname>
             <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>

   9.3 DAV:principal-match

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 DAV:principal-match REPORT
   response is used to identify all members
        of a collection that match the current user. In particular, if 403 (Forbidden), with a response body containing the collection contains principals,
   XML element DAV:non-searchable-property listing the report can 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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 48] 
     <?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 used to
        identify all members searched using the DAV:principal-property-
   search REPORT (defined in Section 9.4). The DAV:principal-collection-
   set property of the collection that match resource identified by the current
        user. Alternatively, if Request-URI specifies
   the scope of the DAV:principal-search-property-set REPORT, as
   follows:

   - All principal and collection contains principal resources that
        have a property that identifies a identified in
   DAV:principal-collection-set are in scope
   - All principal (e.g. DAV:owner),
        then the report can be used to identify all members of the and collection whose property identifies a principal resources that matches
        the current user. For example, this report can return all are
   descendents of

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 37] 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 resources DAV:principal-search-property-set REPORT on
   all principal collections identified in a collection hierarchy that are owned by the
        current user.

      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 of a DAV:principal-
   collection-set property. The
        expectation is

   An access control protocol user agent could use the value results of the named property typically
        contains an href element that contains the URI of
   DAV:principal-search-property-set REPORT to present a principal
        <!ELEMENT self EMPTY>
        prop: see RFC 2518, Section 12.11

        The response body query interface
   to the user for a successful retrieving principals.

   Marshalling:

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

        multistatus: see RFC 2518, Section 12.9

   The response body for a successful DAV:principal-match REPORT
        request MUST contain be a DAV:response DAV:principal-search-property-set XML
   element, containing a DAV:principal-search-property XML element for
   each member of
        the collection property that matches the current user. When may be searched with the
        DAV:principal-property element is used, DAV:principal-property-
   search REPORT. A server MAY limit its response to just a match occurs if the
        current user is subset of
   the same searchable properties, such as the principal identified by the URI
        found in the DAV:href 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.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 49] 
     <!ELEMENT principal-search-property (prop, description) >

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

     prop: see RFC 2518, Section 12.11

   The description element is
        used in a DAV:principal-match report issued against a
        collection principal, it matches a child human-readable description of what
   information this property represents. Servers MUST indicate the collection
        principal if that child (a principal resource) identifies the
        same principal as human
   language of the current user.

        If DAV:prop is specified in description using the xml:lang attribute and SHOULD
   consider the HTTP Accept-Language request body, 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 properties
        specified in client determines the DAV:prop element MUST be reported in set of searchable
   principal properties by requesting the
        DAV:response elements.

   9.3.1 Example: DAV:principal-match DAV:principal-search-property-
   set REPORT

        The following example identifies on the members root of the serverÆs principal URL collection set,
   identified by the URL http://www.webdav.org/doc/ that are owned
        by the current user. The current user (ôgclemmö) is
        authenticated using Digest authentication. http://www.BigCorp.com/users/.

   >> Request <<

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

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 38] xxx
     Accept-Language: en, de
     Authorization: BASIC d2FubmFtYWs6cGFzc3dvcmQ=

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

   >> Response <<

     HTTP/1.1 207 Multi-Status 200 OK
     Content-Type: text/xml; charset="utf-8"
     Content-Length: xxxx xxx

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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 50] 
         </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 WebDAV XML
   Namespace interpretation
        convention, described in Section 23.4 Recommendation [REC-XML-NAMES].

   Note that use of [RFC2518]. 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 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 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 [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

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 39] 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,

Clemm, Hopkins, Sedlar, Whitehead                          [Page 51] 
   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 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 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

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 40] 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
        cuprivset read-

Clemm, Hopkins, Sedlar, Whitehead                          [Page 52] 
   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 in 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].

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 41]

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.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 53] 

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, and Joe Orton. 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.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 42] 54] 

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-19980210. http://www.w3.org/TR/REC-xml-
        19980210. 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.

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

   [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.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 55] 

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

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 43]

     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

Clemm, Hopkins, Sedlar, Whitehead                          [Page 56] 

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 is-principal (#PCDATA)> principalEMPTY>

     <!ELEMENT alternate-URL 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*)>

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 44]

     <!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*)>

Clemm, Hopkins, Sedlar, Whitehead                          [Page 57] 
     <!-- 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 acl-sem*>
        <!ELEMENT acl-sem (ace-combination, ace-ordering, allowed-ace,
        required-principal*)> (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>

   Clemm, Hopkins, Sedlar, Whitehead                      [Page 45]
     <!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
          (href | all

Clemm, Hopkins, Sedlar, Whitehead                          [Page 58] 
       (all? | authenticated authenticated? | unauthenticated unauthenticated? | property self? |
        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>

     <!-- REPORT Method 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

        *** This section (Section 20) MUST be removed before
        publication as an RFC ***

        Section 9.1 defines

   As of the REPORT method. The REPORT method is
        also defined in draft-ietf-deltav-versioning-15, in Section
        3.6, using identical text. This was done to avoid making writing of this
        specification dependent on draft-ietf-deltav-versioning.

        If draft-ietf-deltav-versioning is specification, the DeltaV protocol,
   described in draft-ietf-deltav-versioning-20, has been approved by
   the IESG, but not yet published as an RFC before 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 9.1 MUST 17.1 also needs to be removed. updated with the correct RFC number,
   and the month of issue.

Clemm, Hopkins, Sedlar, Whitehead                          [Page 46] 59]