INTERNET-DRAFT Geoffrey Clemm, IBM
draft-ietf-webdav-acl-11 Anne Hopkins, Microsoft Corporatio
Eric Sedlar, Oracle Corporation
Jim Whitehead, U.C. Santa Cruz
Expires March 10, 2004 September 10, 2003
WebDAV Access Control Protocol
Status of this Memo
This document is an Internet-Draft and is subject to all provisions of
Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task
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Abstract
This document specifies a set of methods, headers, message bodies,
properties, and reports that define Access Control extensions to the
WebDAV Distributed Authoring Protocol. This protocol permits a client
to read and modify access control lists that instruct a server whether
to allow or deny operations upon a resource (such as HyperText Transfer
Protocol (HTTP) method invocations) by a given principal. A lightweight
representation of principals as Web resources supports integration of a
wide range of user management repositories. Search operations allow
discovery and manipulation of principals using human names.
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.example.com/acl/, and
http://www.ics.uci.edu/pub/ietf/webdav/.
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Table of Contents
1 INTRODUCTION.................................................4
1.1 Terms......................................................6
1.2 Notational Conventions.....................................7
2 PRINCIPALS...................................................7
3 PRIVILEGES...................................................8
3.1 DAV:read Privilege.........................................9
3.2 DAV:write Privilege........................................9
3.3 DAV:write-properties.......................................9
3.4 DAV:write-content.........................................10
3.5 DAV:unlock................................................10
3.6 DAV:read-acl Privilege....................................10
3.7 DAV:read-current-user-privilege-set Privilege.............10
3.8 DAV:write-acl Privilege...................................11
3.9 DAV:bind Privilege........................................11
3.10 DAV:unbind Privilege.....................................11
3.11 DAV:all Privilege........................................11
3.12 Aggregation of Predefined Privileges.....................11
4 PRINCIPAL PROPERTIES........................................12
4.1 DAV:alternate-URI-set.....................................12
4.2 DAV:principal-URL.........................................12
4.3 DAV:group-member-set......................................12
4.4 DAV:group-membership......................................13
5 ACCESS CONTROL PROPERTIES...................................13
5.1 DAV:owner.................................................13
5.1.1 Example: Retrieving DAV:owner..........................13
5.1.2 Example: An Attempt to Set DAV:owner...................14
5.2 DAV:supported-privilege-set...............................15
5.2.1 Example: Retrieving a List of Privileges Supported on
a Resource.............................................16
5.3 DAV:current-user-privilege-set............................18
5.3.1 Example: Retrieving the User's Current Set of Assigned
Privileges...................................................19
5.4 DAV:acl...................................................20
5.4.1 ACE Principal..........................................20
5.4.2 ACE Grant and Deny.....................................21
5.4.3 ACE Protection.........................................21
5.4.4 ACE Inheritance........................................21
5.4.5 Example: Retrieving a Resource's Access Control List ..22
5.5 DAV: acl-restrictions.....................................23
5.5.1 DAV:grant-only.........................................23
5.5.2 DAV:no-invert ACE Constraint...........................24
5.5.3 DAV:deny-before-grant..................................24
5.5.4 Required Principals....................................24
Example: Retrieving DAV:acl-restrictions............. ...24
5.6 DAV:inherited-acl-set.....................................25
5.7 DAV:principal-collection-set..............................25
5.7.1 Example: Retrieving DAV:principal-collection-set.......26
5.8 Example: PROPFIND to retrieve access control properties...27
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6 ACL EVALUATION..............................................30
7 ACCESS CONTROL AND EXISTING METHODS.........................31
7.1 ANY HTTP METHOD...........................................32
7.1.1 Error Handling.........................................32
7.2 OPTIONS...................................................32
7.2.1 Example - OPTIONS......................................33
7.3 MOVE......................................................33
7.4 COPY......................................................33
7.5 LOCK......................................................33
8 ACCESS CONTROL METHODS......................................33
8.1 ACL.......................................................33
8.1.1 ACL Preconditions......................................34
8.1.2 Example: the ACL method................................35
8.1.3 Example: ACL method failure due to protected ACE
conflict...............................................36
8.1.4 Example: ACL method failure due to an inherited ACE
conflict...............................................37
8.1.5 Example: ACL method failure due to an attempt to set
grant and deny in a single ACE.........................38
9 ACCESS CONTROL REPORTS......................................39
9.1 REPORT Method.............................................39
9.2 DAV:acl-principal-prop-set Report.........................39
9.2.1 Example: DAV:acl-principal-prop-set Report.............40
9.3 DAV:principal-match REPORT................................42
9.3.1 Example: DAV:principal-match REPORT....................43
9.4 DAV:principal-property-search REPORT......................43
9.4.1 Matching...............................................45
9.4.2 Example: successful DAV:principal-property-search
REPORT.................................................46
9.5 DAV:principal-search-property-set REPORT..................48
9.5.1 Example: DAV:principal-search-property-set REPORT......49
10 XML PROCESSING............................................50
11 INTERNATIONALIZATION CONSIDERATIONS.......................50
12 SECURITY CONSIDERATIONS...................................51
12.1 Increased Risk of Compromised Users......................51
12.2 Risks of the DAV:read-acl and
DAV:current-user-privilege-set Privileges................51
12.3 No Foreknowledge of Initial ACL..........................52
13 AUTHENTICATION............................................52
14 IANA CONSIDERATIONS.......................................52
15 INTELLECTUAL PROPERTY.....................................53
16 ACKNOWLEDGEMENTS..........................................53
17 REFERENCES................................................53
17.1 Normative References.....................................53
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17.2 Informational References.................................54
18 AUTHORS' ADDRESSES........................................55
19 APPENDICES................................................56
19.1 WebDAV XML Document Type Definition Addendum.............56
19.2 WebDAV Method Privilege Table (Normative)................58
1 INTRODUCTION
The goal of the WebDAV access control extensions is to provide an
interoperable mechanism for handling discretionary access control
for content and metadata managed by WebDAV servers. WebDAV access
control can be implemented on content repositories with security
as simple as that of a UNIX file system, as well as more
sophisticated models. The underlying principle of access control
is that who you are determines what operations you can perform on
a resource. The "who you are" is defined by a "principal"
identifier; users, client software, servers, and groups of the
previous have principal identifiers. The "operations you can
perform" are determined by a single "access control list" (ACL)
associated with a resource. An ACL contains a set of "access
control entries" (ACEs), where each ACE specifies a principal and
a set of privileges that are either granted or denied to that
principal. When a principal submits an operation (such as an HTTP
or WebDAV method) to a resource for execution, the server
evaluates the ACEs in the ACL to determine if the principal has
permission for that operation.
Since every ACE contains the identifier of a principal, client
software operated by a human must provide a mechanism for
selecting this principal. This specification uses http(s) scheme
URLs to identify principals, which are represented as WebDAV-
capable resources. There is no guarantee that the URLs identifying
principals will be meaningful to a human. For example,
http://www.example.com/u/256432 and
http://www.example.com/people/Greg.Stein are both valid URLs that
could be used to identify the same principal. To remedy this,
every principal resource has the DAV:displayname property
containing a human-readable name for the principal.
Since a principal can be identified by multiple URLs, it raises
the problem of determining exactly which principal is being
referenced in a given ACE. It is impossible for a client to
determine that an ACE granting the read privilege to
http://www.example.com/people/Greg.Stein also affects the
principal at http://www.example.com/u/256432. That is, a client
has no mechanism for determining that two URLs identify the same
principal resource. As a result, this specification requires
clients to use just one of the many possible URLs for a principal
when creating ACEs. A client can discover which URL to use by
retrieving the DAV:principal-URL property (Section 4.2) from a
principal resource. No matter which of the principal's URLs is
used with PROPFIND, the property always returns the same URL.
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With a system having hundreds to thousands of principals, the
problem arises of how to allow a human operator of client software
to select just one of these principals. One approach is to use
broad collection hierarchies to spread the principals over a large
number of collections, yielding few principals per collection. An
example of this is a two level hierarchy with the first level
containing 36 collections (a-z, 0-9), and the second level being
another 36, creating collections /a/a/, /a/b/, ..., /a/z/, such
that a principal with last name "Stein" would appear at
/s/t/Stein. In effect, this pre-computes a common query, search on
last name, and encodes it into a hierarchy. The drawback with this
scheme is that it handles only a small set of predefined queries,
and drilling down through the collection hierarchy adds
unnecessary steps (navigate down/up) when the user already knows
the principal's name. While organizing principal URLs into a
hierarchy is a valid namespace organization, users should not be
forced to navigate this hierarchy to select a principal.
This specification provides the capability to perform substring
searches over a small set of properties on the resources
representing principals. This permits searches based on last name,
first name, user name, job title, etc. Two separate searches are
supported, both via the REPORT method, one to search principal
resources (DAV:principal-property-search, Section 9.4), the other
to determine which properties may be searched at all
(DAV:principal-search-property-set, Section 9.5).
Once a principal has been identified in an ACE, a server
evaluating that ACE must know the identity of the principal making
a protocol request, and must validate that that principal is who
they claim to be, a process known as authentication. This
specification intentionally omits discussion of authentication, as
the HTTP protocol already has a number of authentication
mechanisms [RFC2617]. Some authentication mechanism (such as HTTP
Digest Authentication, which all WebDAV compliant implementations
are required to support) must be available to validate the
identity of a principal.
The following issues are out of scope for this document:
. Access control that applies only to a particular property on
a resource (excepting the access control properties DAV:acl
and DAV:current-user-privilege-set), rather than the entire
resource,
. Role-based security (where a role can be seen as a
dynamically defined group of principals),
. Specification of the ways an ACL on a resource is
initialized,
. Specification of an ACL that applies globally to all
resources, rather than to a particular resource.
. Creation and maintenance of resources representing people or
computational agents (principals), and groups of these.
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This specification is organized as follows. Section 1.1 defines
key concepts used throughout the specification, and is followed by
a more in-depth discussion of principals (Section 2), and
privileges (Section 3). Properties defined on principals are
specified in Section 4, and access control properties for content
resources are specified in Section 5. The ways ACLs are to be
evaluated is described in section 6. Client discovery of access
control capability using OPTIONS is described in Section 7.1.
Interactions between access control functionality and existing
HTTP and WebDAV methods are described in the remainder of Section
7. The access control setting method, ACL, is specified in Section
8. Four reports that provide limited server-side searching
capabilities are described in Section 9. Sections on XML
processing (Section 10), Internationalization considerations
(Section 11), security considerations (Section 12), and
authentication (Section 13) round out the specification. An
appendix (Section 19.1) provides an XML Document Type Definition
(DTD) for the XML elements defined in the specification.
1.1 Terms
This draft uses the terms defined in HTTP [RFC2616] and WebDAV
[RFC2518]. In addition, the following terms are defined:
principal
A "principal" is a distinct human or computational actor that
initiates access to network resources. In this protocol, a
principal is an HTTP resource that represents such an actor.
group
A "group" is a principal that represents a set of other
principals.
privilege
A "privilege" controls access to a particular set of HTTP
operations on a resource.
aggregate privilege
An "aggregate privilege" is a privilege that contains a set of
other privileges.
abstract privilege
The modifier "abstract", when applied to a privilege on a
resource, means the privilege cannot be set in an access control
element (ACE) on that resource .
access control list (ACL)
An "ACL" is a list of access control elements that define access
control to a particular resource.
access control element (ACE)
An "ACE" either grants or denies a particular set of (non-
abstract) privileges for a particular principal.
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inherited ACE
An "inherited ACE" is an ACE that is dynamically shared from the
ACL of another resource. When a shared ACE changes on the primary
resource, it is also changed on inheriting resources.
protected property
A "protected property" is one whose value cannot be updated except
by a method explicitly defined as updating that specific property.
In particular, a protected property cannot be updated with a
PROPPATCH request.
1.2 Notational Conventions
The augmented BNF used by this document to describe protocol
elements is described in Section 2.1 of [RFC2616]. Because this
augmented BNF uses the basic production rules provided in Section
2.2 of [RFC2616], those rules apply to this document as well.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in [RFC2119].
Definitions of XML elements in this document use XML element type
declarations (as found in XML Document Type Declarations),
described in Section 3.2 of [REC-XML]. When an XML element type in
the "DAV:" namespace is referenced in this document outside of the
context of an XML fragment, the string "DAV:" will be prefixed to
the element name.
2 PRINCIPALS
A principal is a network resource that represents a distinct human
or computational actor that initiates access to network resources.
Users and groups are represented as principals in many
implementations; other types of principals are also possible. A
URI of any scheme MAY be used to identify a principal resource.
However, servers implementing this specification MUST expose
principal resources at an http(s) URL, which is a privileged
scheme that points to resources that have additional properties,
as described in Section 4. So, a principal resource can have
multiple URIs, one of which has to be an http(s) scheme URL.
Although an implementation SHOULD support PROPFIND and MAY support
PROPPATCH to access and modify information about a principal, it
is not required to do so.
A principal resource may be a group, where a group is a principal
that represents a set of other principals, called the members of
the group. If a person or computational agent matches a principal
resource that is a member of a group, they also match the group.
Membership in a group is recursive, so if a principal is a member
of group GRPA, and GRPA is a member of group GRPB, then the
principal is also a member of GRPB.
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3 PRIVILEGES
Ability to perform a given method on a resource MUST be controlled
by one or more privileges. Authors of protocol extensions that
define new HTTP methods SHOULD specify which privileges (by
defining new privileges, or mapping to ones below) are required to
perform the method. A principal with no privileges to a resource
MUST be denied any HTTP access to that resource, unless the
principal matches an ACE constructed using the DAV:all,
DAV:authenticated, or DAV:unauthenticated pseudo-principals (see
Section 5.4.1). Servers MUST report a 403 "Forbidden" error if
access is denied, except in the case where the privilege restricts
the ability to know the resource exists, in which case 404 "Not
Found" may be returned.
Privileges may be containers of other privileges, in which case
they are termed "aggregate privileges". If a principal is granted
or denied an aggregate privilege, it is semantically equivalent to
granting or denying each of the aggregated privileges
individually. For example, an implementation may define add-
member and remove-member privileges that control the ability to
add and remove a member of a group. Since these privileges
control the ability to update the state of a group, these
privileges would be aggregated by the DAV:write privilege on a
group, and granting the DAV:write privilege on a group would also
grant the add-member and remove-member privileges.
Privileges may be declared to be "abstract" for a given resource,
in which case they cannot be set in an ACE on that resource.
Aggregate and non-aggregate privileges are both capable of being
abstract. Abstract privileges are useful for modeling privileges
that otherwise would not be exposed via the protocol. Abstract
privileges also provide server implementations with flexibility in
implementing the privileges defined in this specification. For
example, if a server is incapable of separating the read resource
capability from the read ACL capability, it can still model the
DAV:read and DAV:read-acl privileges defined in this specification
by declaring them abstract, and containing them within a non-
abstract aggregate privilege (say, read-all) that holds DAV:read,
and DAV:read-acl. In this way, it is possible to set the aggregate
privilege, read-all, thus coupling the setting of DAV:read and
DAV:read-acl, but it is not possible to set DAV:read, or DAV:read-
acl individually. Since aggregate privileges can be abstract, it
is also possible to use abstract privileges to group or organize
non-abstract privileges. Privilege containment loops are not
allowed; therefore, a privilege MUST NOT contain itself. For
example, DAV:read cannot contain DAV:read.
The set of privileges that apply to a particular resource may vary
with the DAV:resourcetype of the resource, as well as between
different server implementations. To promote interoperability,
however, this specification defines a set of well-known privileges
(e.g. DAV:read, DAV:write, DAV:read-acl, DAV:write-acl, DAV:read-
current-user-privilege-set, and DAV:all), which can at least be
used to classify the other privileges defined on a particular
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resource. The access permissions on null resources (defined in
[RFC2518], Section 3) are solely those they inherit (if any), and
they are not discoverable (i.e., the access control properties
specified in Section 5 are not defined on null resources). On the
transition from null to stateful resource, the initial access
control list is set by the server's default ACL value policy (if
any).
Server implementations MAY define new privileges beyond those
defined in this specification. Privileges defined by individual
implementations MUST NOT use the DAV: namespace, and instead
should use a namespace that they control, such as an http scheme
URL.
3.1 DAV:read Privilege
The read privilege controls methods that return information about
the state of the resource, including the resource's properties.
Affected methods include GET and PROPFIND. Any implementation-
defined privilege that also controls access to GET and PROPFIND
must be aggregated under DAV:readif an ACL grants access to
DAV:read, the client may expect that no other privilege needs to
be granted to have access to GET and PROPFIND. Additionally, the
read privilege MUST control the OPTIONS method.
<!ELEMENT read EMPTY>
3.2 DAV:write Privilege
The write privilege controls methods that lock a resource or
modify the content, dead properties, or (in the case of a
collection) membership of the resource, such as PUT and PROPPATCH.
Note that state modification is also controlled via locking (see
section 5.3 of [WEBDAV]), so effective write access requires that
both write privileges and write locking requirements are
satisfied. Any implementation-defined privilege that also
controls access to methods modifying content, dead properties or
collection membership must be aggregated under DAV:write, e.g. if
an ACL grants access to DAV:write, the client may expect that no
other privilege needs to be granted to have access to PUT and
PROPPATCH.
<!ELEMENT write EMPTY>
3.3 DAV:write-properties
The DAV:write-properties privilege controls methods that modify
the dead properties of the resource, such as PROPPATCH. Whether
this privilege may be used to control access to any live
properties is determined by the implementation. Any
implementation-defined privilege that also controls access to
methods modifying dead properties must be aggregated under
DAV:write-propertiese.g. if an ACL grants access to DAV:write-
properties, the client can safely expect that no other privilege
needs to be granted to have access to PROPPATCH.
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<!ELEMENT write-properties EMPTY>
3.4 DAV:write-content
The DAV:write-content privilege controls methods that modify the
content or (in the case of a collection) membership of the
resource, such as PUT and DELETE. Any implementation-defined
privilege that also controls access to content or alteration of
collection membership must be aggregated under DAV:write-content
e.g. if an ACL grants access to DAV:write-content, the client can
safely expect that no other privilege needs to be granted to have
access to PUT or DELETE.
<!ELEMENT write-content EMPTY>
3.5 DAV:unlock
The DAV:unlock privilege controls the use of the UNLOCK method by
a principal other than the lock owner (the principal that created
a lock can always perform an UNLOCK). While the set of users who
may lock a resource is most commonly the same set of users who may
modify a resource, servers may allow various kinds of
administrators to unlock resources locked by others. Any privilege
controlling access by non-lock owners to UNLOCK MUST be aggregated
under DAV:unlock.
A lock owner can always remove a lock by issuing an UNLOCK with
the correct lock token and authentication credentials. That is,
even if a principal does not have DAV:unlock privilege, they can
still remove locks they own. Principals other than the lock owner
can remove a lock only if they have DAV:unlock privilege and they
issue an UNLOCK with the correct lock token. Lock timeout is not
affected by the DAV:unlock privilege.
<!ELEMENT unlock EMPTY>
3.6 DAV:read-acl Privilege
The DAV:read-acl privilege controls the use of PROPFIND to
retrieve the DAV:acl property of the resource.
<!ELEMENT read-acl EMPTY>
3.7 DAV:read-current-user-privilege-set Privilege
The DAV:read-current-user-privilege-set privilege controls the use
of PROPFIND to retrieve the DAV:current-user-privilege-set
property of the resource.
Clients are intended to use this property to visually indicate in
their UI items that are dependent on the permissions of a
resource, for example, by graying out resources that are not
writeable.
This privilege is separate from DAV:read-acl because there is a
need to allow most users access to the privileges permitted the
current user (due to its use in creating the UI), while the full
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ACL contains information that may not be appropriate for the
current authenticated user. As a result, the set of users who can
view the full ACL is expected to be much smaller than those who
can read the current user privilege set, and hence distinct
privileges are needed for each.
<!ELEMENT read-current-user-privilege-set EMPTY>
3.8 DAV:write-acl Privilege
The DAV:write-acl privilege controls use of the ACL method to
modify the DAV:acl property of the resource.
<!ELEMENT write-acl EMPTY>
3.9 DAV:bind Privilege
The DAV:bind privilege allows a method to add a new member URL to
the specified collection (for example via PUT or MKCOL). It is
ignored for resources that are not collections.
<!ELEMENT bind EMPTY>
3.10DAV:unbind Privilege
The DAV:unbind privilege allows a method to remove a member URL
from the specified collection (for example via DELETE or MOVE).
It is ignored for resources that are not collections.
<!ELEMENT unbind EMPTY>
3.11 DAV:all Privilege
DAV:all is an aggregate privilege that contains the entire set of
privileges that can be applied to the resource.
<!ELEMENT all EMPTY>
3.12 Aggregation of Predefined Privileges
Server implementations are free to aggregate the predefined
privileges (defined above in Sections 3.1-3.9) subject to the
following limitations:
DAV:read-acl MUST NOT contain DAV:read, DAV:write, DAV:write-acl,
DAV:write-properties, DAV:write-content, or DAV:read-current-user-
privilege-set.
DAV:write-acl MUST NOT contain DAV:write, DAV:read, DAV:read-acl,
or DAV:read-current-user-privilege-set.
DAV:read-current-user-privilege-set MUST NOT contain DAV:write,
DAV:read, DAV:read-acl, or DAV:write-acl.
DAV:write MUST NOT contain DAV:read, DAV:read-acl, or DAV:read-
current-user-privilege-set.
DAV:read MUST NOT contain DAV:write, DAV:write-acl, DAV:write-
properties, or DAV:write-content.
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DAV:write MUST contain DAV:write-properties and DAV:write-content.
4 PRINCIPAL PROPERTIES
Principals are manifested to clients as a WebDAV resource,
identified by a URL. A principal MUST have a non-empty
DAV:displayname property (defined in Section 13.2 of [RFC2518]),
and a DAV:resourcetype property (defined in Section 13.9 of
[RFC2518]). Additionally, a principal MUST report the
DAV:principal XML element in the value of the DAV:resourcetype
property. The element type declaration for DAV:principal is:
<!ELEMENT principal EMPTY>
This protocol defines the following additional properties for a
principal. Since it can be expensive for a server to retrieve
access control information, the name and value of these properties
SHOULD NOT be returned by a PROPFIND allprop request (as defined
in Section 12.14.1 of [RFC2518]).
4.1 DAV:alternate-URI-set
This protected property, if non-empty, contains the URIs of
network resources with additional descriptive information about
the principal. This property identifies additional network
resources (i.e., it contains one or more URIs) that may be
consulted by a client to gain additional knowledge concerning a
principal. One expected use for this property is the storage of an
LDAP [RFC2255] scheme URL. A user-agent encountering an LDAP URL
could use LDAP [RFC2589] to retrieve additional machine-readable
directory information about the principal, and display that
information in its user interface. Support for this property is
REQUIRED, and the value is empty if no alternate URI exists for
the principal.
<!ELEMENT alternate-URI-set (href*)>
4.2 DAV:principal-URL
A principal may have many URLs, but there must be one "principal
URL" that clients can use to uniquely identify a principal. This
protected property contains the URL that MUST be used to identify
this principal in an ACL request. Support for this property is
REQUIRED.
<!ELEMENT principal-URL (href)>
4.3 DAV:group-member-set
This property of a group principal identifies the principals that
are direct members of this group. Since a group may be a member of
another group, a group may also have indirect members (i.e. the
members of its direct members). A URL in the DAV:group-member-set
for a principal MUST be the DAV:principal-URL of that principal.
<!ELEMENT group-member-set (href*)>
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4.4 DAV:group-membership
This protected property identifies the groups in which the
principal is directly a member. Note that a server may allow a
group to be a member of another group, in which case the
DAV:group-membership of those other groups would need to be
queried in order to determine the groups in which the principal is
indirectly a member. Support for this property is REQUIRED.
<!ELEMENT group-membership (href*)>
5 ACCESS CONTROL PROPERTIES
This specification defines a number of new properties for WebDAV
resources. Access control properties may be retrieved just like
other WebDAV properties, using the PROPFIND method. Since it is
expensive, for many servers, to retrieve access control
information, a PROPFIND allprop request (as defined in Section
12.14.1 of [RFC2518]) SHOULD NOT return the names and values of
the properties defined in this section.
Access control properties (especially DAV:acl and DAV:inherited-
acl-set) are defined on the resource identified by the Request-URI
of a PROPFIND request. A direct consequence is that if the
resource is accessible via multiple URI, the value of access
control properties is the same across these URI.
HTTP resources that support the WebDAV Access Control Protocol
MUST contain the following properties. Null resources (described
in Section 3 of [RFC2518]) MUST NOT contain the following
properties.
5.1 DAV:owner
This protected property identifies a particular principal as being
the "owner" of the resource. Since the owner of a resource often
has special access control capabilities (e.g., the owner
frequently has permanent DAV:write-acl privilege), clients might
display the resource owner in their user interface.
<!ELEMENT owner (href)>
5.1.1 Example: Retrieving DAV:owner
This example shows a client request for the value of the DAV:owner
property from a collection resource with URL
http://www.example.com/papers/. The principal making the request
is authenticated using Digest authentication. The value of
DAV:owner is the URL http://www.example.com/acl/users/gstein,
wrapped in the DAV:href XML element.
>> Request <<
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PROPFIND /papers/ HTTP/1.1
Host: www.example.com
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="jim",
realm="jim@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
<?xml version="1.0" encoding="utf-8" ?>
<D:propfind xmlns:D="DAV:">
<D:prop>
<D:owner/>
</D:prop>
</D:propfind>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.example.com/papers/</D:href>
<D:propstat>
<D:prop>
<D:owner>
<D:href>http://www.example.com/acl/users/gstein</D:href>
</D:owner>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
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.example.com/papers>. Since DAV:owner is a protected
property, the server responds with a 207 (Multi-Status) response
that contains a 403 (Forbidden) status code for the act of setting
DAV:owner. Section 8.2.1 of [RFC2518] describes PROPPATCH status
code information, and Section 11 of [RFC2518] describes the Multi-
Status response.
>> Request <<
PROPPATCH /papers/ HTTP/1.1
Host: www.example.com
Content-type: text/xml; charset="utf-8"
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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.example.com/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.example.com/papers/</D:href>
<D:propstat>
<D:prop><D:owner/></D:prop>
<D:status>HTTP/1.1 403 Forbidden</D:status>
<D:responsedescription>
Failure to set protected property (DAV:owner)
</D:responsedescription>
</D:propstat>
</D:response>
</D:multistatus>
5.2 DAV:supported-privilege-set
This is a protected property that identifies the privileges
defined for the resource.
<!ELEMENT supported-privilege-set (supported-privilege*)>
Each privilege appears as an XML element, where aggregate
privileges list as sub-elements all of the privileges that they
aggregate.
<!ELEMENT supported-privilege
(privilege, abstract?, description, supported-privilege*)>
<!ELEMENT privilege ANY>
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An abstract privilege MUST NOT be used in an ACE for that
resource. Servers MUST fail an attempt to set an abstract
privilege.
<!ELEMENT abstract EMPTY>
A description is a human-readable description of what this
privilege controls access to. Servers MUST indicate the human
language of the description using the xml:lang attribute and
SHOULD consider the HTTP Accept-Language request header when
selecting one of multiple available languages.
<!ELEMENT description #PCDATA>
It is envisioned that a WebDAV ACL-aware administrative client
would list the supported privileges in a dialog box, and allow the
user to choose non-abstract privileges to apply in an ACE. The
privileges tree is useful programmatically to map well-known
privileges (defined by WebDAV or other standards groups) into
privileges that are supported by any particular server
implementation. The privilege tree also serves to hide complexity
in implementations allowing large number of privileges to be
defined by displaying aggregates to the user.
5.2.1 Example: Retrieving a List of Privileges Supported on a Resource
This example shows a client request for the DAV:supported-
privilege-set property on the resource
http://www.example.com/papers/. The value of the DAV:supported-
privilege-set property is a tree of supported privileges (using
"[XML Namespace , localname]" to identify each privilege):
[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)
+-- [DAV:, write-properties]
+-- [DAV:, write-content]
|
+-- [DAV:, unlock]
This privilege tree is not normative (except that it reflects the
normative aggregation rules given in Section 3.12), and many
possible privilege trees are possible.
>> Request <<
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PROPFIND /papers/ HTTP/1.1
Host: www.example.com
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.example.com/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>
<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: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>
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<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:privilege> <D:write-properties/> </D:privilege>
<D:description xml:lang="en">
Write properties</D:description>
</D:supported-privilege>
<D:supported-privilege>
<D:privilege> <D:write-content/> </D:privilege>
<D:description xml:lang="en">
Write resource content</D:description>
</D:supported-privilege>
</D:supported-privilege>
<D:supported-privilege>
<D:privilege> <D:unlock/> </D:privilege>
<D:description xml:lang="en">
Unlock resource</D:description>
</D:supported-privilege>
</D:supported-privilege>
</D:supported-privilege-set>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
5.3 DAV:current-user-privilege-set
DAV:current-user-privilege-set is a protected property containing
the exact set of privileges (as computed by the server) granted to
the currently authenticated HTTP user. Aggregate privileges and
their contained privileges are listed. A user-agent can use the
value of this property to adjust its user interface to make
actions inaccessible (e.g., by graying out a menu item or button)
for which the current principal does not have permission. This
property is also useful for determining what operations the
current principal can perform, without having to actually execute
an operation.
<!ELEMENT current-user-privilege-set (privilege*)>
<!ELEMENT privilege ANY>
If the current user is granted a specific privilege, that
privilege must belong to the set of privileges that may be set on
this resource. Therefore, each element in the DAV:current-user-
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privilege-set property MUST identify a non-abstract privilege from
the DAV:supported-privilege-set property.
5.3.1 Example: Retrieving the User's Current Set of Assigned Privileges
Continuing the example from Section 5.2.1, this example shows a
client requesting the DAV:current-user-privilege-set property from
the resource with URL http://www.example.com/papers/. The username
of the principal making the request is "khare", and Digest
authentication is used in the request. The principal with username
"khare" has been granted the DAV:read privilege. Since the
DAV:read privilege contains the DAV:read-acl and DAV:read-current-
user-privilege-set privileges (see Section 5.2.1), the principal
with username "khare" can read the ACL property, and the
DAV:current-user-privilege-set property. However, the DAV:all,
DAV:read-acl, DAV:write-acl and DAV:read-current-user-privilege-
set privileges are not listed in the value of DAV:current-user-
privilege-set, since (for this example) they are abstract
privileges. DAV:write is not listed since the principal with
username "khare" is not listed in an ACE granting that principal
write permission.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.example.com
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="khare",
realm="khare@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
<?xml version="1.0" encoding="utf-8" ?>
<D:propfind xmlns:D="DAV:">
<D:prop>
<D:current-user-privilege-set/>
</D:prop>
</D:propfind>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.example.com/papers/</D:href>
<D:propstat>
<D:prop>
<D:current-user-privilege-set>
<D:privilege> <D:read/> </D:privilege>
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</D:current-user-privilege-set>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
5.4 DAV:acl
This is a protected property that specifies the list of access
control entries (ACEs), which define what principals are to get
what privileges for this resource.
<!ELEMENT acl (ace*) >
Each DAV:ace element specifies the set of privileges to be either
granted or denied to a single principal. If the DAV:acl property
is empty, no principal is granted any privilege.
<!ELEMENT ace (invert | principal, (grant|deny), protected?,
inherited?)>
5.4.1 ACE Principal
The DAV:principal element identifies the principal to which this
ACE applies.
<!ELEMENT principal ((href)
| all | authenticated | unauthenticated
| property | self)>
The current user matches DAV:href only if that user is
authenticated as being (or being a member of) the principal
identified by the URL contained by that DAV:href.
The current user always matches DAV:all.
<!ELEMENT all EMPTY>
The current user matches DAV:authenticated only if authenticated.
<!ELEMENT authenticated EMPTY>
The current user matches DAV:unauthenticated only if not
authenticated.
<!ELEMENT unauthenticated EMPTY>
DAV:all is the union of DAV:authenticated, and
DAV:unauthenticated. For a given request, the user matches either
DAV:authenticated, or DAV:unauthenticated, but not both (that is,
DAV:authenticated and DAV:unauthenticated are disjoint sets).
The current user matches a DAV:property principal in a DAV:acl
property of a resource only if the value of the identified
property of that resource contains at most one DAV:href XML
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element, the URI value of DAV:href identifies a principal, and the
current user is authenticated as being (or being a member of) that
principal. For example, if the DAV:property element contained
<DAV:owner/>, the current user would match the DAV:property
principal only if the current user is authenticated as matching
the principal identified by the DAV:owner property of the
resource.
<!ELEMENT property ANY>
Alternately, some servers may support ACEs applying to those users
NOT matching the current principal, e.g. all users not in a
particular group. This can be done by wrapping the DAV:principal
element with DAV:invert.
<!ELEMENT invert principal>
The current user matches DAV:self in a DAV:acl property of the
resource only if that resource is a principal and that principal
matches the current user or, if the principal is a group, a member
of that group matches the current user.
<!ELEMENT self EMPTY>
5.4.2 ACE Grant and Deny
Each DAV:grant or DAV:deny element specifies the set of privileges
to be either granted or denied to the specified principal. A
DAV:grant or DAV:deny element of the DAV:acl of a resource MUST
only contain non-abstract elements specified in the DAV:supported-
privilege-set of that resource.
<!ELEMENT grant (privilege+)>
<!ELEMENT deny (privilege+)>
<!ELEMENT privilege ANY>
5.4.3 ACE Protection
A server indicates an ACE is protected by including the
DAV:protected element in the ACE. If the ACL of a resource
contains an ACE with a DAV:protected element, an attempt to remove
that ACE from the ACL MUST fail.
<!ELEMENT protected EMPTY>
5.4.4 ACE Inheritance
The presence of a DAV:inherited element indicates that this ACE is
inherited from another resource that is identified by the URL
contained in a DAV:href element. An inherited ACE cannot be
modified directly, but instead the ACL on the resource from which
it is inherited must be modified.
Note that ACE inheritance is not the same as ACL initialization.
ACL initialization defines the ACL that a newly created resource
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will use (if not specified). ACE inheritance refers to an ACE
that is logically shared - where an update to the resource
containing an ACE will affect the ACE of each resource that
inherits that ACE. The method by which ACLs are initialized or by
which ACEs are inherited is not defined by this document.
<!ELEMENT inherited (href)>
5.4.5 Example: Retrieving a Resource's Access Control List
Continuing the example from Sections 5.2.1 and 5.3.1, this example
shows a client requesting the DAV:acl property from the resource
with URL http://www.example.com/papers/. There are two ACEs
defined in this ACL:
ACE #1: The group identified by URL
http://www.example.com/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 "maintainers" 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 "maintainers" group) can read the
DAV:acl property and the DAV:current-user-privilege-set property.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.example.com
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="masinter",
realm="webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
<D:propfind xmlns:D="DAV:">
<D:prop>
<D:acl/>
</D:prop>
</D:propfind>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.example.com/papers/</D:href>
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<D:propstat>
<D:prop>
<D:acl>
<D:ace>
<D:principal>
<D:href>http://www.example.com/acl/groups/maintainers</D:href>
</D:principal>
<D:grant>
<D:privilege> <D:write/> </D:privilege>
</D:grant>
</D:ace>
<D:ace>
<D:principal>
<D:all/>
</D:principal>
<D:grant>
<D:privilege> <D:read/> </D:privilege>
</D:grant>
</D:ace>
</D:acl>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
5.5 DAV: acl-restrictions
This protected property defines the types of ACLs supported by
this server, to avoid clients needlessly getting errors. When a
client tries to set an ACL via the ACL method, the server may
reject the attempt to set the ACL as specified. The following
properties indicate the restrictions the client must observe
before setting an ACL:
<grant-only> Deny ACEs are not supported
<no-invert> Inverted ACEs are not supported
<deny-before-grant> All deny ACEs must occur before any grant
ACEs
<required-principal> Indicates which principals are
required to be present
<!ELEMENT acl-restrictions (grant-only?, no-invert?, deny-before-
grant?, required-principal?)>
5.5.1 DAV:grant-only
This element indicates that ACEs with deny clauses are not
allowed.
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<!ELEMENT grant-only EMPTY>
5.5.2 DAV:no-invert ACE Constraint
This element indicates that ACEs with the <invert> element are not
allowed.
<!ELEMENT no-invert EMPTY>
5.5.3 DAV:deny-before-grant
This element indicates that all deny ACEs must precede all grant
ACEs.
<!ELEMENT deny-before-grant EMPTY>
5.5.4 Required Principals
The required principal elements identify which principals must
have an ACE defined in the ACL.
<!ELEMENT required-principal
(all? | authenticated? | unauthenticated? | self? | href* |
property*)>
For example, the following element requires that the ACL contain a
DAV:owner property ACE:
<D:required-principal xmlns:D="DAV:">
<D:property> <D:owner/> </D:property>
</D:required-principal>
Example: Retrieving DAV:acl-restrictions
In this example, the client requests the value of the DAV:acl-
restrictions property. Digest authentication provides credentials
for the principal operating the client.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.example.com
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-restrictions/>
</D:prop>
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</D:propfind>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.example.com/papers/</D:href>
<D:propstat>
<D:prop>
<D:acl-restrictions>
<D:principal-only-one-ace/>
<D:required-principal>
<D:all/>
</D:required-principal>
</D:acl-restrictions>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:response>
</D:multistatus>
5.6 DAV:inherited-acl-set
This protected property contains a set of URLs that identify other
resources that also control the access to this resource. To have
a privilege on a resource, not only must the ACL on that resource
(specified in the DAV:acl property of that resource) grant the
privilege, but so must the ACL of each resource identified in the
DAV:inherited-acl-set property of that resource. Effectively, the
privileges granted by the current ACL are ANDed with the
privileges granted by each inherited ACL.
<!ELEMENT inherited-acl-set (href*)>
5.7 DAV:principal-collection-set
This protected property of a resource contains a set of URLs that
identify the root collections that contain the principals that are
available on the server that implements this resource. A WebDAV
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*)>
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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 principal collections, and therefore clients should not
assume they have retrieved an exhaustive listing. Additionally, a
server MAY elect to report none of the principal collections 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.
5.7.1 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.example.com/papers/. The property
contains the two URLs, http://www.example.com/acl/users/ and
http://www.example.com/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.example.com
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>
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>> 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.example.com/papers/</D:href>
<D:propstat>
<D:prop>
<D:principal-collection-set>
<D:href>http://www.example.com/acl/users/</D:href>
<D:href>http://www.example.com/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>
5.8 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.example.com
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>
</D:propfind>
>> Response <<
HTTP/1.1 207 Multi-Status
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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.example.com/acl/"> <D:response>
<D:href>http://www.example.com/top/container/</D:href>
<D:propstat>
<D:prop>
<D:owner>
<D:href>http://www.example.com/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:unbind/> </D:privilege>
<D:description xml:lang="en">Remove binding to 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>
</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>
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</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.example.com/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.example.com/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.example.com/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.
The value of the DAV:supported-privilege-set property is a tree of
supported privileges (using "[XML Namespace , localname]" to
identify each privilege):
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[DAV:, all] (aggregate, abstract)
|
+-- [DAV:, read]
+-- [DAV:, write] (aggregate, abstract)
|
+-- [http://www.example.com/acl, create]
+-- [http://www.example.com/acl, update]
+-- [http://www.example.com/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.example.com/users/esedlar is granted the DAV:read,
DAV:write, and DAV:read-acl privileges.
ACE #2: The principals identified by the URL
http://www.example.com/groups/marketing are denied the DAV:read
privilege. In this example, the principal URL identifies a group.
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.example.com/top, the parent collection of this
resource.
6 ACL EVALUATION
WebDAV ACLs are evaluated in similar manner as ACLs on Windows NT
and in NFSv4 [NFSV4]). An ACL is evaluated to determine whether
or not access will be granted for a WebDAV request. ACEs are
maintained in a particular order, and are evaluated until all of
the permissions required by the current request have been granted,
at which point the ACL evaluation is terminated and access is
granted. If, during ACL evaluation, a <deny> ACE (matching the
current user) is encountered for a privilege which has not yet
been granted, the ACL evaluation is terminated and access is
denied. Failure to have all required privileges granted results
in access being denied.
Note that the semantics of many other existing ACL systems may be
represented via this mechanism, by mixing deny and grant ACEs.
For example, consider the standard "rwx" privilege scheme used by
UNIX. In this scheme, if the current user is the owner of the
file, access is granted if the corresponding privilege bit is set
and denied if not set, regardless of the permissions set on the
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files group and for the world. An ACL for UNIX permissions of
"r--rw-r--"might be constructed like:
<D:acl>
<D:ace>
<D:principal><D:property>
<D:owner/></D:property></D:principal>
<D:grant><D:privilege><D:read/></D:privilege></D:grant>
</D:ace>
<D:ace>
<D:principal><D:property>
<D:owner/> </D:property></D:principal>
<D:deny><D:privilege><D:all/></D:privilege></D:deny>
</D:ace>
<D:ace>
<D:principal><D:property>
<D:group/> </D:property></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:group/> </D:property></D:principal>
<D:deny><D:privilege><D:all/></D:privilege></D:deny>
</D:ace>
<D:ace>
<D:principal><D:all></D:principal>
<D:grant><D:privilege><D:read/></D:privilege></D:grant>
</D:ace>
</D:acl>
and the <acl-restrictions> would be defined as:
<D:no-invert/><D:principal-only-one-ace/>
<D:required-principal>
<D:all/>
<D:property><D:owner/></D:property>
<D:property><D:group/><D:group/>
</D:required-principal>
Note that the client can still get errors from a UNIX server in
spite of obeying the <acl-restrictions>, including <D:allowed-
principal> (adding an ACE specifying a principal other than the
ones in the ACL above) or <D:ace-conflict> (by trying to reorder
the ACEs in the example above), as these particular implementation
semantics are too complex to be captured with the simple (but
general) declarative restrictions.
7 ACCESS CONTROL AND EXISTING METHODS
This section defines the impact of access control functionality on
existing methods.
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7.1 ANY HTTP METHOD
7.1.1 Error Handling
The WebDAV ACL mechanism requires the usage of HTTP method
"preconditions" as described in section 1.6 of RFC3253 for ALL
HTTP methods. All HTTP methods have an additional precondition
called DAV:need-privileges. If an HTTP method fails due to
insufficient privileges, the response body to the "403 Forbidden"
error MUST contain the <DAV:error> element, which in turn contains
the <DAV:need-privileges> element, which contains one or more
<DAV:resource> elements indicating which resource had insufficient
privileges, and what the lacking privileges were:
<!ELEMENT need-privileges (resource)* >
<!ELEMENT resource ( href , privilege ) >
Since some methods require multiple permissions on multiple
resources, this information is needed to resolve any ambiguity.
There is no requirement that all privilege violations be reported
for implementation reasons, some servers may only report the first
privilege violation. For example:
>> Request <<
MOVE /a/b/ HTTP/1.1
Host: www.example.com
Destination: http://www.example.com/c/d
>> Response <<
HTTP/1.1 403 Forbidden
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<D:error xmlns:D="DAV:">
<D:need-privileges>
<D:resource>
<D:href>/a</D:href>
<D:privilege><D:unbind/></D:privilege>
</D:resource>
<D:resource>
<D:href>/c</D:href>
<D:privilege><D:bind/></D:privilege>
</D:resource>
</D:need-privileges>
</D:error>
7.2 OPTIONS
If the server supports access control, it MUST return "access-
control" as a field in the DAV response header from an OPTIONS
request on any resource implemented by that server. A value of
"access-control" in the DAV header MUST indicate that the server
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supports all MUST level requirements and REQUIRED features
specified in this document.
7.2.1 Example - OPTIONS
>> Request <<
OPTIONS /foo.html HTTP/1.1
Host: www.example.com
Content-Length: 0
>> Response <<
HTTP/1.1 200 OK
DAV: 1, 2, access-control
Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL
In this example, the OPTIONS response indicates that the server
supports access control and that /foo.html can have its access
control list modified by the ACL method.
7.3 MOVE
When a resource is moved from one location to another due to a
MOVE request, the non-inherited and non-protected ACEs in the
DAV:acl property of the resource MUST NOT be modified, or the MOVE
request fails. Handling of inherited and protected ACEs is
intentionally undefined to give server implementations flexibility
in how they implement ACE inheritance and protection.
7.4 COPY
The DAV:acl property on the resource at the destination of a COPY
MUST be the same as if the resource was created by an individual
resource creation request (e.g. MKCOL, PUT). Clients wishing to
preserve the DAV:acl property across a copy need to read the
DAV:acl property prior to the COPY, then perform an ACL operation
on the new resource at the destination to restore, insofar as this
is possible, the original access control list.
7.5 LOCK
A lock on a resource ensures that only the lock owner can modify
ACEs that are not inherited and not protected (these are the only
ACEs that a client can modify with an ACL request). A lock does
not protect inherited or protected ACEs, since a client cannot
modify them with an ACL request on that resource.
8 ACCESS CONTROL METHODS
8.1 ACL
The ACL method modifies the access control list (which can be read
via the DAV:acl property) of a resource. Specifically, the ACL
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method only permits modification to ACEs that are not inherited,
and are not protected. An ACL method invocation modifies all non-
inherited and non-protected ACEs in a resource's access control
list to exactly match the ACEs contained within in the DAV:acl XML
element (specified in Section 5.4) of the request body. An ACL
request body MUST contain only one DAV:acl XML element. Unless the
non-inherited and non-protected ACEs of the DAV:acl property of
the resource can be updated to be exactly the value specified in
the ACL request, the ACL request MUST fail.
It is possible that the ACEs visible to the current user in the
DAV:acl property may only be a portion of the complete set of ACEs
on that resource. If this is the case, an ACL request only
modifies the set of ACEs visible to the current user, and does not
affect any non-visible ACE.
In order to avoid overwriting DAV:acl changes by another client, a
client SHOULD acquire a WebDAV lock on the resource before
retrieving the DAV:acl property of a resource that it intends on
updating.
Implementation Note: Two common operations are to add or remove
an ACE from an existing access control list. To accomplish
this, a client uses the PROPFIND method to retrieve the value
of the DAV:acl property, then parses the returned access
control list to remove all inherited and protected ACEs (these
ACEs are tagged with the DAV:inherited and DAV:protected XML
elements). In the remaining set of non-inherited, non-protected
ACEs, the client can add or remove one or more ACEs before
submitting the final ACE set in the request body of the ACL
method.
8.1.1 ACL Preconditions
An implementation MUST enforce the following constraints on an ACL
request. If the constraint is violated, a 403 (Forbidden) or 409
(Conflict) response MUST be returned and the indicated XML element
MUST be returned as a child of a top level DAV:error element in an
XML response body.
Though these status elements are generally expressed as empty XML
elements (and are defined as EMPTY in the DTD), implementations
MAY return additional descriptive XML elements as children of the
status element. Clients MUST be able to accept children of these
status elements. Clients that do not understand the additional XML
elements should ignore them.
(DAV:no-ace-conflict): The ACEs submitted in the ACL request MUST
NOT conflict with each other. This is a catchall error code
indicating that an implementation-specific ACL restriction has
been violated.
(DAV:no-protected-ace-conflict): The ACEs submitted in the ACL
request MUST NOT conflict with the protected ACEs on the resource.
For example, if the resource has a protected ACE granting
DAV:write to a given principal, then it would not be consistent if
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the ACL request submitted an ACE denying DAV:write to the same
principal.
(DAV:no-inherited-ace-conflict): The ACEs submitted in the ACL
request MUST NOT conflict with the inherited ACEs on the resource.
For example, if the resource inherits an ACE from its parent
collection granting DAV:write to a given principal, then it would
not be consistent if the ACL request submitted an ACE denying
DAV:write to the same principal. Note that reporting of this error
will be implementation-dependent. Implementations MUST either
report this error or allow the ACE to be set, and then let normal
ACE evaluation rules determine whether the new ACE has any impact
on the privileges available to a specific principal.
(DAV:limited-number-of-aces): The number of ACEs submitted in the
ACL request MUST NOT exceed the number of ACEs allowed on that
resource. However, ACL-compliant servers MUST support at least
one ACE granting privileges to a single principal, and one ACE
granting privileges to a group.
(DAV:deny-before-grant): All non-inherited deny ACEs MUST precede
all non-inherited grant ACEs.
(DAV:grant-only): The ACEs submitted in the ACL request MUST NOT
include a deny ACE. This precondition applies only when the ACL
restrictions of the resource include the DAV:grant-only constraint
(defined in Section 5.5.1).
(DAV:no-invert): The ACL request MUST NOT include a DAV:invert
element. This precondition applies only when the ACL semantics
of the resource includes the DAV:no-invert constraint (defined in
Section 6.3.4).
(DAV:no-abstract): The ACL request MUST NOT attempt to grant or
deny an abstract privilege (see Section 5.2).
(DAV:not-supported-privilege): The ACEs submitted in the ACL
request MUST be supported by the resource.
(DAV:missing-required-principal): The result of the ACL request
MUST have at least one ACE for each principal identified in a
DAV:required-principal XML element in the ACL semantics of that
resource (see Section 5.5.4).
(DAV:recognized-principal): Every principal URL in the ACL request
MUST identify a principal resource.
(DAV:allowed-principal): The principals specified in the ACEs
submitted in the ACL request MUST be allowed as principals for the
resource. For example, a server where only authenticated
principals can access resources would not allow the DAV:all or
DAV:unauthenticated principals to be used in an ACE, since these
would allow unauthenticated access to resources.
8.1.2 Example: the ACL method
In the following example, user "fielding", authenticated by
information in the Authorization header, grants the principal
identified by the URL http://www.example.com/users/esedlar (i.e.,
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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.example.com
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.example.com/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/1.1 200 OK
8.1.3 Example: ACL method failure due to protected ACE conflict
In the following request, user "fielding", authenticated by
information in the Authorization header, attempts to deny the
principal identified by the URL
http://www.example.com/users/esedlar (i.e., the user "esedlar")
write privileges. Prior to the request, the DAV:acl property on
the resource contained a protected ACE (see Section 5.4.3)
granting DAV:owner the DAV:read and DAV:write privileges. The
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principal identified by URL http://www.example.com/users/esedlar
is the owner of the resource. The ACL method invocation fails
because the submitted ACE conflicts with the protected ACE, thus
violating the semantics of ACE protection.
>> Request <<
ACL /top/container/ HTTP/1.1
Host: www.example.com
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.example.com/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:error xmlns:D="DAV:">
<D:no-protected-ace-conflict/>
</D:error>
8.1.4 Example: ACL method failure due to an inherited ACE conflict
In the following request, user "ejw", authenticated by information
in the Authorization header, tries to change the access control
list on the resource http://www.example.com/top/index.html. This
resource has two inherited ACEs.
Inherited ACE #1 grants the principal identified by URL
http://www.example.com/users/ejw (i.e., the user "ejw")
http://www.example.com/privs/write-all and DAV:read-acl
privileges. On this server, http://www.example.com/privs/write-all
is an aggregate privilege containing DAV:write, and DAV:write-acl.
Inherited ACE #2 grants principal DAV:all the DAV:read privilege.
The request attempts to set a (non-inherited) ACE, denying the
principal identified by the URL http://www.example.com/users/ejw
(i.e., the user "ejw") DAV:write permission. This conflicts with
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inherited ACE #1. Note that the decision to report an inherited
ACE conflict is specific to this server implementation. Another
server implementation could have allowed the new ACE to be set,
and then used normal ACE evaluation rules to determine whether the
new ACE has any impact on the privileges available to a principal.
>> Request <<
ACL /top/index.html HTTP/1.1
Host: www.example.com
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.example.com/privs/">
<D:ace>
<D:principal>
<D:href>http://www.example.com/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" ?>
<D:error xmlns:D="DAV:">
<D:no-inherited-ace-conflict xmlns:D="DAV:"/>
</D:error>
8.1.5 Example: ACL method failure due to an attempt to set grant and
deny in a single ACE.
In this example, user "ygoland", authenticated by information in
the Authorization header, tries to change the access control list
on the resource http://www.example.com/diamond/engagement-
ring.gif. The ACL request includes a single, syntactically and
semantically incorrect ACE, which attempts to grant the group
identified by the URL http://www.example.com/users/friends
DAV:read privilege and deny the principal identified by URL
http://www.example.com/users/ygoland-so (i.e., the user "ygoland-
so") DAV:read privilege. However, it is illegal to have multiple
principal elements, as well as both a grant and deny element in
the same ACE, so the request fails due to poor syntax.
>> Request <<
ACL /diamond/engagement-ring.gif HTTP/1.1
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Host: www.example.com
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.example.com/users/friends</D:href>
</D:principal>
<D:grant><D:read/></D:grant>
<D:principal>
<D:href>http://www.example.com/users/ygoland-so</D:href>
</D:principal>
<D:deny><D:read/></D:deny>
</D:ace>
</D:acl>
>> Response <<
HTTP/1.1 400 Bad Request
Content-Length: 0
Note that if the request had been divided into two ACEs, one to
grant, and one to deny, the request would have been syntactically
well formed.
9 ACCESS CONTROL REPORTS
9.1 REPORT Method
The REPORT method (defined in Section 3.6 of [RFC3253]) provides
an extensible mechanism for obtaining information about a
resource. Unlike the PROPFIND method, which returns the value of
one or more named properties, the REPORT method can involve more
complex processing. REPORT is valuable in cases where the server
has access to all of the information needed to perform the complex
request (such as a query), and where it would require multiple
requests for the client to retrieve the information needed to
perform the same request.
A server that supports the WebDAV Access Control Protocol MUST
support the DAV:expand-property report (defined in Section 3.8 of
[RFC3253]).
9.2 DAV:acl-principal-prop-set Report
The DAV:acl-principal-prop-set report returns, for all principals
in the DAV:acl property (of the Request-URI) that are identified
by http(s) URLs or by a DAV:property principal, the value of the
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properties specified in the REPORT request body. In the case where
a principal URL appears multiple times, the DAV:acl-principal-
prop-set report MUST return the properties for that principal only
once. Support for this report is REQUIRED.
One expected use of this report is to retrieve the human readable
name (found in the DAV:displayname property) of each principal
found in an ACL. This is useful for constructing user interfaces
that show each ACE in a human readable form.
Marshalling
The request body MUST be a DAV:acl-principal-prop-set XML element.
<!ELEMENT acl-principal-prop-set ANY>
ANY value: a sequence of one or more elements, with at most one
DAV:prop element.
prop: see RFC 2518, Section 12.11
This report is only defined when the Depth header has value "0";
other values result in a 400 (Bad Request) error response. Note
that [RFC3253], Section 3.6, states that if the Depth header is
not present, it defaults to a value of "0".
The response body for a successful request MUST be a
DAV:multistatus XML element (i.e., the response uses the same
format as the response for PROPFIND). In the case where there are
no response elements, the returned multistatus XML element is
empty.
multistatus: see RFC 2518, Section 12.9
The response body for a successful DAV:acl-principal-prop-set
REPORT request MUST contain a DAV:response element for each
principal identified by an http(s) URL listed in a DAV:principal
XML element of an ACE within the DAV:acl property of the resource
identified by the Request-URI.
Postconditions:
(DAV:number-of-matches-within-limits): The number of matching
principals must fall within server-specific, predefined limits.
For example, this condition might be triggered if a search
specification would cause the return of an extremely large number
of responses.
9.2.1 Example: DAV:acl-principal-prop-set Report
Resource http://www.example.com/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.example.com/people/gstein (the user "gstein") is
granted DAV:write, DAV:write-acl, DAV:read-acl privileges.
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ACE #3: The group identified by
http://www.example.com/groups/authors (the "authors" group) is
granted DAV:write and DAV:read-acl privileges.
The following example shows a DAV:acl-principal-prop-set report
requesting the DAV:displayname property. It returns the value of
DAV:displayname for resources http://www.example.com/people/gstein
and http://www.example.com/groups/authors , but not for DAV:all,
since this is not an http(s) URL.
>> Request <<
REPORT /index.html HTTP/1.1
Host: www.example.com
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Depth: 0
<?xml version="1.0" encoding="utf-8" ?>
<D:acl-principal-prop-set xmlns:D="DAV:">
<D:prop>
<D:displayname/>
</D:prop>
</D:acl-principal-prop-set>
>> 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.example.com/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.example.com/groups/authors</D:href>
<D:propstat>
<D:prop>
<D:displayname>Site authors</D:displayname>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
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9.3 DAV:principal-match REPORT
The DAV:principal-match REPORT is used to identify all members (at
any depth) of the collection identified by the Request-URI that
are principals and that match the current user. In particular, if
the collection contains principals, the report can be used to
identify all members of the collection that match the current
user. Alternatively, if the collection contains resources that
have a property that identifies a principal (e.g. DAV:owner), the
report can be used to identify all members of the collection whose
property identifies a principal that matches the current user. For
example, this report can return all of the resources in a
collection hierarchy that are owned by the current user. Support
for this report is REQUIRED.
Marshalling:
The request body MUST be a DAV:principal-match XML element.
<!ELEMENT principal-match ((principal-property | self), prop?)>
<!ELEMENT principal-property ANY>
ANY value: an element whose value identifies a property. The
expectation is the value of the named property typically contains
an href element that contains the URI of a principal
<!ELEMENT self EMPTY>
prop: see RFC 2518, Section 12.11
This report is only defined when the Depth header has value "0";
other values result in a 400 (Bad Request) error response. Note
that [RFC3253], Section 3.6, states that if the Depth header is
not present, it defaults to a value of "0".
The response body for a successful request MUST be a
DAV:multistatus XML element. In the case where there are no
response elements, the returned multistatus XML element is empty.
multistatus: see RFC 2518, Section 12.9
The response body for a successful DAV:principal-match REPORT
request MUST contain a DAV:response element for each member of the
collection that matches the current user. When the DAV:principal-
property element is used, a match occurs if the current user is
matched by the principal identified by the URI found in the
DAV:href element of the property identified by the DAV:principal-
property element. When the DAV:self element is used in a
DAV:principal-match report issued against a group, it matches the
group if a member identifies the same principal as the current
user.
If DAV:prop is specified in the request body, the properties
specified in the DAV:prop element MUST be reported in the
DAV:response elements.
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9.3.1 Example: DAV:principal-match REPORT
The following example identifies the members of the collection
identified by the URL http://www.example.com/doc that are owned by
the current user. The current user ("gclemm") is authenticated
using Digest authentication.
>> Request <<
REPORT /doc/ HTTP/1.1
Host: www.example.com
Authorization: Digest username="gclemm",
realm="gclemm@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Depth: 0
<?xml version="1.0" encoding="utf-8" ?>
<D:principal-match xmlns:D="DAV:">
<D:principal-property>
<D:owner/>
</D:principal-property>
</D:principal-match>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:">
<D:response>
<D:href>http://www.example.com/doc/foo.html</D:href>
<D:status>HTTP/1.1 200 OK</D:status>
</D:response>
<D:response>
<D:href>http://www.example.com/doc/img/bar.gif</D:href>
<D:status>HTTP/1.1 200 OK</D:status>
</D:response>
</D:multistatus>
9.4 DAV:principal-property-search REPORT
The DAV:principal-property-search REPORT performs a search for all
principals whose properties contain character data that matches
the search criteria specified in the request. One expected use of
this report is to discover the URL of a principal associated with
a given person or group by searching for them by name. This is
done by searching over DAV:displayname, which is defined on all
principals.
The actual search method (exact matching vs. substring matching
vs, prefix-matching, case-sensitivity) deliberately is left to the
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server implementation to allow implementation on a wide set of
possible user management systems. In cases where the
implementation of DAV:principal-property-search is not constrained
by the semantics of an underlying user management repository,
preferred default semantics are caseless substring matches.
For implementation efficiency, servers do not typically support
searching on all properties. A search requesting properties that
are not searchable for a particular principal will not match that
principal.
Support for the DAV:principal-property-search report is REQUIRED.
Implementation Note: The value of a WebDAV property is a
sequence of well-formed XML, and hence can include any
character in the Unicode/ISO-10646 standard, that is, most
known characters in human languages. Due to the idiosyncrasies
of case mapping across human languages, implementation of case-
insensitive matching is non-trivial. Implementors of servers
that do perform substring matching are strongly encouraged to
consult [CaseMap], especially Section 2.3 ("Caseless
Matching"), for guidance when implementing their case-
insensitive matching algorithms.
Implementation Note: Some implementations of this protocol will
use an LDAP repository for storage of principal metadata. The
schema describing each attribute (akin to a WebDAV property) in
an LDAP repository specifies whether it supports case-sensitive
or caseless searching. One of the benefits of leaving the
search method to the discretion of the server implementation is
the default LDAP attribute search behavior can be used when
implementing the DAV:principal-property-search report.
Marshalling:
The request body MUST be a DAV:principal-property-search XML
element containing a search specification and an optional list of
properties. For every principal that matches the search
specification, the response will contain the value of the
requested properties on that principal.
<!ELEMENT principal-property-search
((property-search+), prop?, apply-to-principal-collection-set?) >
By default, the report searches all members (at any depth) of the
collection identified by the Request-URI. If DAV:apply-to-
principal-collection-set is specified in the request body, the
request is applied instead to each collection identified by the
DAV:prinicipal-collection-set property of the resource identified
by the Request-URI.
The DAV:property-search element contains a prop element
enumerating the properties to be searched and a match element,
containing the search string.
<!ELEMENT property-search (prop, match) >
prop: see RFC 2518, Section 12.11
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<!ELEMENT match #PCDATA >
Multiple property-search elements or multiple elements within a
DAV:prop element will be interpreted with a logical AND.
This report is only defined when the Depth header has value "0";
other values result in a 400 (Bad Request) error response. Note
that [RFC3253], Section 3.6, states that if the Depth header is
not present, it defaults to a value of "0".
The response body for a successful request MUST be a
DAV:multistatus XML element. In the case where there are no
response elements, the returned multistatus XML element is empty.
multistatus: see RFC 2518, Section 12.9
The response body for a successful DAV:principal-property-search
REPORT request MUST contain a DAV:response element for each
principal whose property values satisfy the search specification
given in DAV:principal-property-search.
The response body for an unsuccessful DAV:principal-property-
search REPORT request MUST contain, after the XML element
indicating the failed precondition or postcondition, a DAV:prop
element containing the property that caused the pre/postcondition
to fail.
If DAV:prop is specified in the request body, the properties
specified in the DAV:prop element MUST be reported in the
DAV:response elements.
Preconditions:
None
Postconditions:
(DAV:number-of-matches-within-limits): The number of matching
principals must fall within server-specific, predefined limits.
For example, this condition might be triggered if a search
specification would cause the return of an extremely large number
of responses.
9.4.1 Matching
There are several cases to consider when matching strings. The
easiest case is when a property value is "simple" and has only
character information item content (see [REC-XML-INFOSET]). For
example, the search string "julian" would match the
DAV:displayname property with value "Julian Reschke". Note that
the on-the-wire marshalling of DAV:displayname in this case is:
<D:displayname xmlns:D="DAV:">Julian Reschke</D:displayname>
The name of the property is encoded into the XML element
information item, and the character information item content of
the property is "Julian Reschke".
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A more complicated case occurs when properties have mixed content
(that is, compound values consisting of multiple child element
items, other types of information items, and character information
item content). Consider the property "aprop" in the namespace
"http://www.example.com/props/", marshalled as:
<W:aprop xmlns:W="http://www.example.com/props/">
{cdata 0}<W:elem1>{cdata 1}</W:elem1>
<W:elem2>{cdata 2}</W:elem2>{cdata 3}
</W:aprop>
In this case, matching is performed on each individual contiguous
sequence of character information items. In the example above, a
search string would be compared to the four following strings:
{cdata 0}
{cdata 1}
{cdata 2}
{cdata 3}
That is, four individual matches would be performed, one each for
{cdata 0}, {cdata 1}, {cdata 2}, and {cdata 3}.
9.4.2 Example: successful DAV:principal-property-search REPORT
In this example, the client requests the principal URLs of all
users whose DAV:displayname property contains the substring "doE"
and whose "title" property in the namespace
"http://BigCorp.com/ns/" (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.example.com/ns/ namespace: department, phone,
office, salary
The response shows that two principal resources meet the search
specification, "John Doe" and "Zygdoebert Smith". The property
"salary" in namespace "http://www.example.com/ns/" is not
returned, since the principal making the request does not have
sufficient access permissions to read this property.
>> Request <<
REPORT /users/ HTTP/1.1
Host: www.example.com
Content-Type: text/xml; charset=utf-8
Content-Length: xxxx
Depth: 0
<?xml version="1.0" encoding="utf-8" ?>
<D:principal-property-search xmlns:D="DAV:">
<D:property-search>
<D:prop>
<D:displayname/>
</D:prop>
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<D:match>doE</D:match>
</D:property-search>
<D:property-search>
<D:prop xmlns:B="http://www.example.com/ns/">
<B:title/>
</D:prop>
<D:match>Sales</D:match>
</D:property-search>
<D:prop xmlns:B="http://www.example.com/ns/">
<D:displayname/>
<B:department/>
<B:phone/>
<B:office/>
<B:salary/>
</D:prop>
</D:principal-property-search>
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset=utf-8
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:" xmlns:B="http://BigCorp.com/ns/">
<D:response>
<D:href>http://www.example.com/users/jdoe</D:href>
<D:propstat>
<D:prop>
<D:displayname>John Doe</D:displayname>
<B:department>Widget Sales</B:department>
<B:phone>234-4567</B:phone>
<B:office>209</B:office>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
<D:propstat>
<D:prop>
<B:salary/>
</D:prop>
<D:status>HTTP/1.1 403 Forbidden</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>http://www.example.com/users/zsmith</D:href>
<D:propstat>
<D:prop>
<D:displayname>Zygdoebert Smith</D:displayname>
<B:department>Gadget Sales</B:department>
<B:phone>234-7654</B:phone>
<B:office>114</B:office>
</D:prop>
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<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>
9.5 DAV:principal-search-property-set REPORT
The DAV:principal-search-property-set REPORT identifies those
properties that may be searched using the DAV:principal-property-
search REPORT (defined in Section 9.4).
Servers MUST support the DAV:principal-search-property-set REPORT
on all collections identified in the value of a DAV:principal-
collection-set property.
An access control protocol user agent could use the results of the
DAV:principal-search-property-set REPORT to present a query
interface to the user for retrieving principals.
Support for this report is REQUIRED.
Implementation Note: Some clients will have only limited screen
real estate for the display of lists of searchable properties.
In this case, a user might appreciate having the most
frequently searched properties be displayed on-screen, rather
than having to scroll through a long list of searchable
properties. One mechanism for signaling the most frequently
searched properties is to return them towards the start of a
list of properties. A client can then preferentially display
the list of properties in order, increasing the likelihood that
the most frequently searched properties will appear on-screen,
and will not require scrolling for their selection.
Marshalling:
The request body MUST be an empty DAV:principal-search-property-
set XML element.
This report is only defined when the Depth header has value "0";
other values result in a 400 (Bad Request) error response. Note
that [RFC3253], Section 3.6, states that if the Depth header is
not present, it defaults to a value of "0".
The response body MUST be a DAV:principal-search-property-set XML
element, containing a DAV:principal-search-property XML element
for each property that may be searched with the DAV:principal-
property-search REPORT. A server MAY limit its response to just a
subset of the searchable properties, such as those likely to be
useful to an interactive access control client.
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<!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.
<!ELEMENT principal-search-property (prop, description) >
The DAV:prop element contains one principal property on which the
server is able to perform a DAV:principal-property-search REPORT.
prop: see RFC 2518, Section 12.11
The description element is a human-readable description of what
information this property represents. Servers MUST indicate the
human language of the description using the xml:lang attribute and
SHOULD consider the HTTP Accept-Language request header when
selecting one of multiple available languages.
<!ELEMENT description #PCDATA >
9.5.1 Example: DAV:principal-search-property-set REPORT
In this example, the client determines the set of searchable
principal properties by requesting the DAV:principal-search-
property-set REPORT on the root of the server's principal URL
collection set, identified by http://www.example.com/users/.
>> Request <<
REPORT /users/ HTTP/1.1
Host: www.example.com
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
Accept-Language: en, de
Authorization: BASIC d2FubmFtYWs6cGFzc3dvcmQ=
Depth: 0
<?xml version="1.0" encoding="utf-8" ?>
<D:principal-search-property-set xmlns:D="DAV:"/>
>> Response <<
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<D:principal-search-property-set xmlns:D="DAV:">
<D:principal-search-property>
<D:prop>
<D:displayname/>
</D:prop>
<D:description xml:lang="en">Full name</D:description>
</D:principal-search-property>
<D:principal-search-property>
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<D:prop xmlns:B="http://BigCorp.com/ns/">
<B:title/>
</D:prop>
<D:description xml:lang="en">Job title</D:description>
</D:principal-search-property>
</D:principal-search-property-set>
10 XML PROCESSING
Implementations of this specification MUST support the XML element
ignore rule, as specified in Section 23.3.2 of [RFC2518], and the
XML Namespace recommendation [REC-XML-NAMES].
Note that use of the DAV namespace is reserved for XML elements
and property names defined in a standards-track or Experimental
IETF RFC.
11 INTERNATIONALIZATION CONSIDERATIONS
In this specification, the only human-readable content can be
found in the description XML element, found within the
DAV:supported-privilege-set property. This element contains a
human-readable description of the capabilities controlled by a
privilege. As a result, the description element must be capable
of representing descriptions in multiple character sets. Since
the description element is found within a WebDAV property, it is
represented on the wire as XML [REC-XML], and hence can leverage
XML's language tagging and character set encoding capabilities.
Specifically, XML processors at minimum must be able to read XML
elements encoded using the UTF-8 [UTF-8] encoding of the ISO 10646
multilingual plane. XML examples in this specification demonstrate
use of the charset parameter of the Content-Type header, as
defined in [RFC3023], as well as the XML "encoding" attribute,
which together provide charset identification information for MIME
and XML processors. Futhermore, this specification requires server
implementations to tag description fields with the xml:lang
attribute (see Section 2.12 of [REC-XML]), which specifies the
human language of the description. Additionally, server
implementations should take into account the value of the Accept-
Language HTTP header to determine which description string to
return.
For XML elements other than the description element, it is
expected that implementations will treat the property names,
privilege names, and values as tokens, and convert these tokens
into human-readable text in the user's language and character set
when displayed to a person. Only a generic WebDAV property
display utility would display these values in their raw form to a
human user.
For error reporting, we follow the convention of HTTP/1.1 status
codes, including with each status code a short, English
description of the code (e.g., 200 (OK)). While the possibility
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exists that a poorly crafted user agent would display this message
to a user, internationalized applications will ignore this
message, and display an appropriate message in the user's language
and character set.
Further internationalization considerations for this protocol are
described in the WebDAV Distributed Authoring protocol
specification [RFC2518].
12 SECURITY CONSIDERATIONS
Applications and users of this access control protocol should be
aware of several security considerations, detailed below. In
addition to the discussion in this document, the security
considerations detailed in the HTTP/1.1 specification [RFC2616],
the WebDAV Distributed Authoring Protocol specification [RFC2518],
and the XML Media Types specification [RFC3023] should be
considered in a security analysis of this protocol.
12.1 Increased Risk of Compromised Users
In the absence of a mechanism for remotely manipulating access
control lists, if a single user's authentication credentials are
compromised, only those resources for which the user has access
permission can be read, modified, moved, or deleted. With the
introduction of this access control protocol, if a single
compromised user has the ability to change ACLs for a broad range
of other users (e.g., a super-user), the number of resources that
could be altered by a single compromised user increases. This risk
can be mitigated by limiting the number of people who have write-
acl privileges across a broad range of resources.
12.2 Risks of the DAV:read-acl and DAV:current-user-privilege-set
Privileges
The ability to read the access privileges (stored in the DAV:acl
property), or the privileges permitted the currently authenticated
user (stored in the DAV:current-user-privilege-set property) on a
resource may seem innocuous, since reading an ACL cannot possibly
affect the resource's state. However, if all resources have world-
readable ACLs, it is possible to perform an exhaustive search for
those resources that have inadvertently left themselves in a
vulnerable state, such as being world-writeable. In particular,
the property retrieval method PROPFIND, executed with Depth
infinity on an entire hierarchy, is a very efficient way to
retrieve the DAV:acl or DAV:current-user-privilege-set properties.
Once found, this vulnerability can be exploited by a denial of
service attack in which the open resource is repeatedly
overwritten. Alternately, writeable resources can be modified in
undesirable ways.
To reduce this risk, read-acl privileges should not be granted to
unauthenticated principals, and restrictions on read-acl and read-
current-user-privilege-set privileges for authenticated principals
should be carefully analyzed when deploying this protocol. Access
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to the current-user-privilege-set property will involve a tradeoff
of usability versus security. When the current-user-privilege-set
is visible, user interfaces are expected to provide enhanced
information concerning permitted and restricted operations, yet
this information may also indicate a vulnerability that could be
exploited. Deployment of this protocol will need to evaluate this
tradeoff in light of the requirements of the deployment
environment.
12.3 No Foreknowledge of Initial ACL
In an effort to reduce protocol complexity, this protocol
specification intentionally does not address the issue of how to
manage or discover the initial ACL that is placed upon a resource
when it is created. The only way to discover the initial ACL is to
create a new resource, then retrieve the value of the DAV:acl
property. This assumes the principal creating the resource also
has been granted the DAV:read-acl privilege.
As a result, it is possible that a principal could create a
resource, and then discover that its ACL grants privileges that
are undesirable. Furthermore, this protocol makes it possible
(though unlikely) that the creating principal could be unable to
modify the ACL, or even delete the resource. Even when the ACL can
be modified, there will be a short period of time when the
resource exists with the initial ACL before its new ACL can be
set.
Several factors mitigate this risk. Human principals are often
aware of the default access permissions in their editing
environments and take this into account when writing information.
Furthermore, default privilege policies are usually very
conservative, limiting the privileges granted by the initial ACL.
13 AUTHENTICATION
Authentication mechanisms defined for use with HTTP and WebDAV
also apply to this WebDAV Access Control Protocol, in particular
the Basic and Digest authentication mechanisms defined in
[RFC2617]. Implementation of the ACL spec requires that Basic
authentication, if used, MUST only be supported over secure
transport such as TLS.
14 IANA CONSIDERATIONS
This document uses the namespace defined by [RFC2518] for XML
elements. That is, this specification uses the "DAV:" URI
namespace, previously registered in the URI schemes registry. All
other IANA considerations mentioned in [RFC2518] are also
applicable to this specification.
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15 INTELLECTUAL PROPERTY
The following notice is copied from RFC 2026, section 10.4, and
describes the position of the IETF concerning intellectual
property claims made against this document.
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use other technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on
the IETF's procedures with respect to rights in standards-track
and standards-related documentation can be found in BCP-11. Copies
of claims of rights made available for publication and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this
specification can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention
any copyrights, patents or patent applications, or other
proprietary rights that may cover technology that may be required
to practice this standard. Please address the information to the
IETF Executive Director.
16 ACKNOWLEDGEMENTS
This protocol is the collaborative product of the WebDAV ACL
design team: Bernard Chester, Geoff Clemm, Anne Hopkins, Barry
Lind, Sean Lyndersay, Eric Sedlar, Greg Stein, and Jim Whitehead.
The authors are grateful for the detailed review and comments
provided by Jim Amsden, Dylan Barrell, Gino Basso, Murthy
Chintalapati, Lisa Dusseault, Stefan Eissing, Tim Ellison, Yaron
Goland, Dennis Hamilton, Laurie Harper, Eckehard Hermann, Ron
Jacobs, Chris Knight, Remy Maucherat, Larry Masinter, Joe Orton,
Peter Raymond, Julian Reschke, and Keith Wannamaker. 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.
17 REFERENCES
17.1 Normative References
[RFC2119] S.Bradner, "Key words for use in RFCs to Indicate
Requirement Levels." RFC 2119, BCP 14, March, 1997.
[REC-XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible
Markup Language (XML)." World Wide Web Consortium Recommendation
REC-xml.http://www.w3.org/TR/REC-xml
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INTERNET-DRAFT WebDAV ACL September 10, 2003
[REC-XML-NAMES] T. Bray, D. Hollander, A. Layman, "Name Spaces in
XML" World Wide Web Consortium Recommendation REC-xml-names.
http://www.w3.org/TR/REC-xml-names/
[RFC3253] G. Clemm, J. Amsden, T. Ellison, C. Kaler, J. Whitehead,
"Versioning Extensions to WebDAV." RFC 3253, March 2002.
[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, 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, June, 1999.
[RFC2518] Y. Goland, E. Whitehead, A. Faizi, S. R. Carter, D.
Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV." RFC
2518, February, 1999.
[RFC2368] P. Hoffman, L. Masinter, J. Zawinski, "The mailto URL
scheme." RFC 2368, July, 1998.
[RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types."
RFC 3023, January, 2001.
[RFC3010] S. Shepler, B. Callaghan, D. Robinson, R. Thurlow, C.
Beame, M. Eisler, D.Noveck "NFS version 4 Protocol." RFC 3010,
December 2000.
[UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode
and ISO 10646." RFC 2279, January, 1998.
17.2 Informational References
[RFC2026] S.Bradner, "The Internet Standards Process - 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 Standard Annex #21,
March 26, 2001. http://www.unicode.org/unicode/reports/tr21
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18 AUTHORS' ADDRESSES
Geoffrey Clemm
IBM
20 Maguire Road
Lexington, MA 02421
Email: geoffrey.clemm@us.ibm.com
Anne Hopkins
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
Email: annehop@microsoft.com
Eric Sedlar
Oracle Corporation
500 Oracle Parkway
Redwood Shores, CA 94065
Email: eric.sedlar@oracle.com
Jim Whitehead
U.C. Santa Cruz
Dept. of Computer Science
Baskin Engineering
1156 High Street
Santa Cruz, CA 95064
Email: ejw@cse.ucsc.edu
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19 APPENDICES
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 write-properties EMPTY>
<!ELEMENT write-content EMPTY>
<!ELEMENT unlock EMPTY>
<!ELEMENT read-acl EMPTY>
<!ELEMENT read-current-user-privilege-set EMPTY>
<!ELEMENT write-acl EMPTY>
<!ELEMENT all EMPTY>
<!-- Principal Properties (Section 4) -->
<!ELEMENT principal EMPTY>
<!ELEMENT alternate-URI-set (href*)>
<!ELEMENT principal-URL (href)>
<!ELEMENT group-member-set (href*)>
<!ELEMENT group-membership (href*)>
<!-- Access Control Properties (Section 5) -->
<!-- DAV:owner Property (Section 5.1) -->
<!ELEMENT owner (href prop?)>
<!ELEMENT prop (see [RFC2518], section 12.11)>
<!-- DAV:supported-privilege-set Property (Section 5.2) -->
<!ELEMENT supported-privilege-set (supported-privilege*)>
<!ELEMENT supported-privilege
(privilege, abstract?, description, supported-privilege*)>
<!ELEMENT privilege ANY>
<!ELEMENT abstract EMPTY>
<!ELEMENT description #PCDATA>
<!ELEMENT privilege ANY>
<!-- DAV:current-user-privilege-set Property (Section 5.3) -->
<!ELEMENT current-user-privilege-set (privilege*)>
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<!-- DAV:acl Property (Section 5.4) -->
<!ELEMENT acl (ace)* >
<!ELEMENT ace (invert | principal, (grant|deny), protected?,
inherited?)>
<!ELEMENT invert principal>
<!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:inherited-acl-set Property (Section 5.6) -->
<!ELEMENT inherited-acl-set (href*)>
<!-- DAV:principal-collection-set Property (Section 5.6) -->
<!ELEMENT principal-collection-set (href*)>
<!-- DAV:acl-semantics Property (Section 6) -->
<!ELEMENT acl-semantics (ace-combination?, ace-ordering?, allowed-
ace?, required-principal?)>
<!ELEMENT ace-combination
(first-match | all-grant-before-any-deny | specific-deny-
overrides-grant)>
<!ELEMENT first-match EMPTY>
<!ELEMENT all-grant-before-any-deny EMPTY>
<!ELEMENT specific-deny-overrides-grant EMPTY>
<!ELEMENT ace-ordering (deny-before-grant)? >
<!ELEMENT deny-before-grant EMPTY>
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<!ELEMENT allowed-ace (grant-only |
no-invert)*>
<!ELEMENT grant-only EMPTY>
<!ELEMENT no-invert EMPTY>
<!ELEMENT required-principal
(all? | authenticated? | unauthenticated? | self? | href*
|property*)>
<!-- ACL method preconditions (Section 8.1.1) -->
<!ELEMENT no-ace-conflict EMPTY>
<!ELEMENT no-protected-ace-conflict EMPTY>
<!ELEMENT no-inherited-ace-conflict EMPTY>
<!ELEMENT limited-number-of-aces EMPTY>
<!ELEMENT no-abstract EMPTY>
<!ELEMENT not-supported-privilege EMPTY>
<!ELEMENT missing-required-principal EMPTY>
<!ELEMENT recognized-principal EMPTY>
<!ELEMENT allowed-principal EMPTY>
<!-- REPORTs (Section 9) -->
<!ELEMENT acl-principal-prop-set 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, match) >
<!ELEMENT match #PCDATA >
<!ELEMENT principal-search-property-set (principal-search-
property*) >
<!ELEMENT principal-search-property (prop, description) >
19.2 WebDAV Method Privilege Table (Normative)
The following table of WebDAV methods (as defined in RFC 2518, 2616,
and 3253) clarifies which privileges are required for access for each
method. Note that the privileges listed, if denied, MUST cause access
to be denied. However, given that a specific implementation MAY define
an additional custom privilege to control access to existing methods,
having all of the indicated privileges does not mean that access will
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be granted. Note that lack of the indicated privileges does not imply
that access will be denied, since a particular implementation may use a
sub-privilege aggregated under the indicated privilege to control
access. Privileges required refer to the current resource being
processed unless otherwise specified.
METHOD PRIVILEGES
GET <D:read>
HEAD <D:read>
OPTIONS <D:read>
PUT (target exists) <D:write-content> on target resource
PUT (no target exists) <D:bind> on parent collection of target
PROPPATCH <D:write-properties>
ACL <D:write-acl>
PROPFIND <D:read> (plus <D:read-acl> and
<D:read-current-user-privilege-set> as needed)
COPY (target exists) <D:read>, <D:write-content> and <D:write-
properties> on target resource
COPY (no target exists) <D:read>, <D:bind> on target collection
MOVE (no target exists) <D:unbind> on source collection and <D:bind>
on target collection
MOVE (target exists) As above, plus <D:unbind> on the target
collection
DELETE <D:unbind> on parent collection
LOCK (target exists) <D:write-content>
LOCK (no target exists) <D:bind> on parent collection
MKCOL <D:bind> on parent collection
UNLOCK <D:unlock>
CHECKOUT <D:write-properties >
CHECKIN <D:write-properties >
REPORT <D:read> (on all referenced resources)
VERSION-CONTROL <D:write-properties>
MERGE <D:write-content>
MKWORKSPACE <D:write-content> on parent collection
BASELINE-CONTROL <D:write-properties> and <D:write-content>
MKACTIVITY <D:write-content> on parent collection
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