INTERNET-DRAFT Geoffrey Clemm, Rational Software
draft-ietf-webdav-acl-07 Anne Hopkins, Microsoft Corporation
Eric Sedlar, Oracle Corporation
Jim Whitehead, U.C. Santa Cruz
Expires May 9, 2001 November 9, 2001
WebDAV Access Control Protocol
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference material
or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This document specifies a set of methods, headers, and message bodies
that define Access Control extensions to the WebDAV Distributed
Authoring Protocol. This protocol permits a client to read and modify
access control lists that instruct a server whether to allow or deny
operations upon a resource (such as HTTP method invocations) by a given
principal.
This document is a product of the Web Distributed Authoring and
Versioning (WebDAV) working group of the Internet Engineering Task
Force. Comments on this draft are welcomed, and should be addressed to
the acl@webdav.org mailing list. Other related documents can be found at
http://www.webdav.org/acl/, and http://www.ics.uci.edu/pub/ietf/webdav/.
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Table of Contents
1 INTRODUCTION.......................................................5
1.1 Terms............................................................7
1.2 Notational Conventions...........................................8
2 PRINCIPALS.........................................................8
3 PRIVILEGES.........................................................9
3.1 DAV:read Privilege..............................................11
3.2 DAV:write Privilege.............................................11
3.3 DAV:read-acl Privilege..........................................11
3.4 DAV:read-current-user-privilege-set Privilege...................11
3.5 DAV:write-acl Privilege.........................................12
3.6 DAV:all Privilege...............................................12
3.7 Aggregation of Predefined Privileges............................12
4 PRINCIPAL PROPERTIES..............................................12
4.1 DAV:alternate-URI-set...........................................13
5 ACCESS CONTROL PROPERTIES.........................................13
5.1 DAV:owner.......................................................13
5.1.1 Example: Retrieving DAV:owner................................14
5.1.2 Example: An Attempt to Set DAV:owner.........................15
5.2 DAV:supported-privilege-set.....................................16
5.2.1 Example: Retrieving a List of Privileges Supported on a
Resource.....................................................16
5.3 DAV:current-user-privilege-set..................................18
5.3.1 Example: Retrieving the User's Current Set of Assigned
Privileges.........................................................19
5.4 DAV:acl.........................................................20
5.4.1 ACE Principal................................................20
5.4.2 ACE Grant and Deny...........................................21
5.4.3 ACE Protection...............................................21
5.4.4 ACE Inheritance..............................................22
5.4.5 Example: Retrieving a Resource's Access Control List......22
5.5 DAV:acl-semantics...............................................23
5.5.1 Example: Retrieving DAV:acl-semantics........................24
5.6 DAV:principal-collection-set....................................25
5.6.1 Example: Retrieving DAV:principal-collection-set.............26
5.7 Example: PROPFIND to retrieve access control properties.........27
6 ACL SEMANTICS.....................................................30
6.1 ACE Combination.................................................31
6.1.1 DAV:first-match ACE Combination..............................31
6.1.2 DAV:all-grant-before-any-deny ACE Combination................31
6.1.3 DAV:specific-deny-overrides-grant ACE Combination............31
6.2 ACE Ordering....................................................31
6.2.1 DAV:deny-before-grant ACE Ordering...........................32
6.3 Allowed ACE.....................................................32
6.3.1 DAV:principal-only-one-ace ACE Constraint....................32
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6.3.2 DAV:grant-only ACE Constraint................................32
6.4 Required Principals.............................................32
7 ACCESS CONTROL AND EXISTING METHODS...............................32
7.1 OPTIONS.........................................................33
7.1.1 Example - OPTIONS............................................33
7.2 MOVE............................................................33
7.3 COPY............................................................33
7.4 DELETE..........................................................33
7.5 LOCK............................................................34
8 ACCESS CONTROL METHODS............................................34
8.1 ACL.............................................................34
8.1.1 ACL Preconditions............................................34
8.1.2 Example: the ACL method......................................36
8.1.3 Example: ACL method failure due to protected ACE conflict....37
8.1.4 Example: ACL method failure due to an inherited ACE conflict 38
8.1.5 Example: ACL method failure due to an attempt to set grant
and deny in a single ACE.....................................39
9 ACCESS CONTROL REPORTS............................................40
9.1 REPORT Method...................................................40
9.2 DAV:acl-principal-props Report..................................40
9.2.1 Example: DAV:acl-principal-props Report......................40
9.3 DAV:principal-match REPORT......................................42
9.3.1 Example: DAV:principal-match REPORT..........................43
9.4 DAV:principal-property-search REPORT............................44
9.4.1 Matching.....................................................45
9.4.2 Example: successful DAV:principal-property-search REPORT.....46
9.4.3 Example: Unsuccessful DAV:principal-property-search REPORT...48
9.5 DAV:principal-search-property-set REPORT........................49
9.5.1 Example: DAV:principal-search-property-set REPORT............50
10 XML PROCESSING..................................................51
11 INTERNATIONALIZATION CONSIDERATIONS.............................51
12 SECURITY CONSIDERATIONS.........................................52
12.1 Increased Risk of Compromised Users...........................52
12.2 Risks of the DAV:read-acl and DAV:current-user-privilege-set
Privileges....................................................52
12.3 No Foreknowledge of Initial ACL...............................53
13 AUTHENTICATION..................................................53
14 IANA CONSIDERATIONS.............................................53
15 INTELLECTUAL PROPERTY...........................................54
16 ACKNOWLEDGEMENTS................................................54
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17 REFERENCES......................................................55
17.1 Normative References..........................................55
17.2 Informational References......................................56
18 AUTHORS' ADDRESSES..............................................56
19 APPENDICIES.....................................................57
19.1 XML Document Type Definition..................................57
20 NOTE TO RFC EDITOR..............................................59
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1 INTRODUCTION
The goal of the WebDAV access control extensions is to provide an
interoperable mechanism for handling discretionary access control for
content and metadata managed by WebDAV servers. WebDAV access
control can be implemented on content repositories with security as
simple as that of a UNIX file system, as well as more sophisticated
models. The underlying principle of access control is that who you
are determines what operations you can perform on a resource. The
"who you are" is defined by a "principal" identifier; users, client
software, servers, and groups of the previous have principal
identifiers. The "operations you can perform" is determined by a
single "access control list" (ACL) associated with a resource. An
ACL contains a set of "access control entries" (ACEs), where each ACE
specifies a principal and a set of privileges that are either granted
or denied to that principal. When a principal submits an operation
(such as an HTTP or WebDAV method) to a resource for execution, the
server evaluates the ACEs in the ACL to determine if the principal
has permission for that operation.
Since every ACE contains the identifier of a principal, client
software operated by a human must provide a mechanism for selecting
this principal. This specification uses http(s) scheme URLs to
identify principals, which are represented as WebDAV-capable
resources. There is no guarantee that the URLs identifying principals
will be meaningful to a human. For example,
http://www.dav.org/u/256432 and http://www.dav.org/people/Greg.Stein
are both valid URLs that could be used to identify the same
principal. To remedy this, every principal resource has the
DAV:displayname property containing a human-readable name for the
principal.
Since a principal can be identified by multiple URLs, it raises the
problem of determining exactly which principal's operations are being
described in a given ACE. It is impossible for a client to determine
that an ACE granting the read privilege to
http://www.dav.org/people/Greg.Stein also affects the principal at
http://www.dav.org/u/256432. That is, a client has no mechanism for
determining that two URLs identify the same principal resource. As a
result, this specification requires clients to use just one of the
many possible URLs for a principal when creating ACEs. A client can
discover this URL by retrieving the DAV:principal-URL property
(Section 4.2) from a principal resource. No matter which of the
principal's URLs is used with PROPFIND, the property always returns
the same URL.
Once a system has hundreds to thousands of principals, the problem
arises of how to allow a human operator of client software to select
just one of these principals. One approach is to use broad collection
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hierarchies to spread the principals over a large number of
collections, yielding few principals per collection. An example of
this is a two level hierarchy with the first level containing 36
collections (a-z, 0-9), and the second level being another 36,
creating collections /a/a/, /a/b/, à, /a/z/, such that a principal
with last name "Stein" would appear at /s/t/Stein. In effect, this
pre-computes a common query, search on last name, and encodes it into
a hierarchy. The drawback with this scheme is that it handles only a
small set of predefined queries, and drilling down through the
collection hierarchy adds unnecessary steps (navigate down/up) when
the user already knows the principal's name. While organizing
principal URLs into a hierarchy is a valid namespace organization,
users should not be forced to navigate this hierarchy to select a
principal.
This specification provides the capability to perform substring
searches on a small set of properties on the resources representing
principals. This permits searches based on last name, first name,
user name, job title, etc. Two separate searches are supported, via
the REPORT method, one to search principal resources, the other to
determine which properties may be searched at all.
Once a principal has been identified in an ACE, a server evaluating
that ACE must know the identity of the principal making a protocol
request, and must validate that that principal is who they claim to
be, a process known as authentication. This specification
intentionally omits discussion of authentication, as the HTTP
protocol already has a number of authentication mechanisms [RFC2617].
Some authentication mechanism (such as HTTP Digest Authentication,
which all WebDAV compliant implementations are required to support)
must be available to validate the identity of a principal.
The following issues are out of scope for this document:
* Access control that applies only to a particular property on a
resource (excepting the access control properties DAV:acl and
DAV:current-user-privilege-set), rather than the entire
resource,
* Role-based security (where a role can be seen as a dynamically
defined collection of principals),
* Specification of the ways an ACL on a resource is initialized,
* Specification of an ACL that applies globally to all
resources, rather than to a particular resource.
* Creation and maintenance of resources representing people or
computational agents (principals), and groups of these.
This specification is organized as follows. Section 1.1 defines key
concepts used throughout the specification, and is followed by a more
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in-depth discussion of principals (Section 2), and privileges
(Section 3). Properties defined on principals are specified in
Section 4, and access control properties for content resources are
specified in Section 5. The semantics of access control lists are
described in Section 6, including sections on ACE combination
(Section 6.1), ACE ordering (Section 6.2), and principals required to
be present in an ACE (Section 6.4). Client discovery of access
control capability using OPTIONS is described in Section 7.1.
Interactions between access control functionality and existing HTTP
and WebDAV methods are described in the remainder of Section 7. The
access control setting method, ACL, is specified in Section 8. Four
reports that provide limited server-side searching capabilities are
described in Section 9. A note on XML processing (Section 10),
Internationalization considerations (Section 11), security
considerations (Section 12), and a note on authentication (Section
13) round out the specification. An appendix (Section 19.1) provides
an XML Document Type Definition (DTD) for the XML elements defined in
the specification.
1.1 Terms
This draft uses the terms defined in HTTP [RFC2616] and WebDAV
[RFC2518]. In addition, the following terms are defined:
principal
A "principal" is a distinct human or computational actor that
initiates access to network resources. In this protocol, a
principal is an HTTP resource that represents such an actor.
principal collection
A "principal collection" is a group of principals, and is
represented in this protocol by a WebDAV collection containing HTTP
resources that represent principals, and principal collections.
privilege
A "privilege" controls access to a particular set of HTTP
operations on a resource.
aggregate privilege
An "aggregate privilege" is a privilege that contains a set of
other privileges.
abstract privilege
The modifier "abstract", when applied to a privilege, means the
privilege cannot be set in an access control element (ACE).
access control list (ACL)
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An "ACL" is a list of access control elements that define access
control to a particular resource.
access control element (ACE)
An "ACE" either grants or denies a particular set of (non-abstract)
privileges for a particular principal.
inherited ACE
An "inherited ACE" is an ACE that is dynamically shared from the
ACL of another resource. When a shared ACE changes on the primary
resource, it is also changed on inheriting resources.
protected property
A "protected property" is one whose value cannot be updated except
by a method explicitly defined as updating that specific property.
In particular, a protected property cannot be updated with a
PROPPATCH request.
1.2 Notational Conventions
The augmented BNF used by this document to describe protocol elements
is described in Section 2.1 of [RFC2616]. Because this augmented BNF
uses the basic production rules provided in Section 2.2 of [RFC2616],
those rules apply to this document as well.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Definitions of XML elements in this document use XML element type
declarations (as found in XML Document Type Declarations), described
in Section 3.2 of [REC-XML]. When an XML element type in the "DAV:"
namespace is referenced in this document outside of the context of an
XML fragment, the string "DAV:" will be prefixed to the element type.
2 PRINCIPALS
A principal is a network resource that represents a distinct human or
computational actor that initiates access to network resources. Users
and groups are represented as principals in many implementations;
other types of principals are also possible. A URI of any scheme MAY
be used to identify a principal resource. However, servers
implementing this specification MUST expose principal resources at an
http(s) URL, which is a privileged scheme that points to resources
that have additional properties, as described in Section 4. So, a
principal resource can have multiple URIs, one of which has to be an
http(s) scheme URL. Although an implementation SHOULD support
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PROPFIND and MAY support PROPPATCH to access and modify information
about a principal, it is not required to do so.
A principal resource may or may not be a collection. If a person or
computational agent matches a principal resource that is contained by
a collection principal, they also match the collection principal.
This definition is recursive, and hence if a person or computational
agent matches a collection principal that is the child of another
collection principal, they also match the parent collection
principal. Membership in a collection principal is also recursive, so
a principal in a collection principal GRPA contained by collection
principal GRPB is a member of both GRPA and GRPB. Implementations not
supporting recursive membership in principal collections can return
an error if the client attempts to bind collection principals into
other collection principals.
Servers that support aggregation of principals (e.g. groups of users
or other groups) MUST manifest them as collection principals. At
minimum, principals and collection principals MUST support the
OPTIONS and PROPFIND methods.
Implementer's Note: Collection principals are first and foremost
WebDAV collections. Therefore they contain resources as members.
Since there is no requirement that all members of a collection
principal need be principals, it is possible for a collection
principal to have non-principals as members. When enumerating the
principals-only membership of a collection principal, it is
necessary to retrieve the DAV:resourcetype property and check it
for the DAV:principal XML element (described in Section 4). If the
DAV:principal XML element is not present, the resource is not a
principal and may be ignored for the purposes of determining the
principals-only membership of the collection principal.
For example, the collection principal /FOO/ has two members, Bar
and Baz. Bar is a principal but Baz is not. Therefore when
determining which principals belong to the collection principal
/FOO/, a client would enumerate the membership using PROPFIND
while asking for the DAV:resourcetype property, and see that only
Bar has the DAV:principal XML element. Therefore, only Bar is the
only principal that is a member of the collection principal /FOO/.
3 PRIVILEGES
Ability to perform a given method on a resource SHOULD be controlled
by one or more privileges. Authors of protocol extensions that
define new HTTP methods SHOULD specify which privileges (by defining
new privileges, or mapping to ones below) are required to perform the
method. A principal with no privileges to a resource SHOULD be
denied any HTTP access to that resource, unless the principal matches
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an ACE constructed using the DAV:all, DAV:authenticated, or
DAV:unauthenticated pseudo-principals (see Section 5.4.1).
Privileges may be containers of other privileges, in which case they
are termed aggregate privileges. If a principal is granted or denied
an aggregate privilege, it is semantically equivalent to granting or
denying each of the aggregated privileges individually. For example,
an implementation may define add-member and remove-member privileges
that control the ability to add and remove an internal member of a
collection. Since these privileges control the ability to update the
state of a collection, these privileges would be aggregated by the
DAV:write privilege on a collection, and granting the DAV:write
privilege on a collection would also grant the add-member and remove-
member privileges.
Privileges may have the quality of being abstract, in which case they
cannot be set in an ACE. Aggregate and non-aggregate privileges are
both capable of being abstract. Abstract privileges are useful for
modeling privileges that otherwise would not be exposed via the
protocol. Abstract privileges also provide server implementations
with flexibility in implementing the privileges defined in this
specification. For example, if a server is incapable of separating
the read resource capability from the read ACL capability, it can
still model the DAV:read and DAV:read-acl privileges defined in this
specification by declaring them abstract, and containing them within
a non-abstract aggregate privilege (say, read-all) that holds
DAV:read, and DAV:read-acl. In this way, it is possible to set the
aggregate privilege, read-all, thus coupling the setting of DAV:read
and DAV:read-acl, but it is not possible to set DAV:read, or
DAV:read-acl individually. Since aggregate privileges can be
abstract, it is also possible to use abstract privileges to group or
organize non-abstract privileges. Privilege containment loops are not
allowed, hence a privilege MUST NOT contain itself. For example,
DAV:read cannot contain DAV:read.
The set of privileges that apply to a particular resource may vary
with the DAV:resourcetype of the resource, as well as between
different server implementations. To promote interoperability,
however, this specification defines a set of well-known privileges
(e.g. DAV:read, DAV:write, DAV:read-acl, DAV:write-acl, DAV:read-
current-user-privilege-set, and DAV:all), which can at least be used
to classify the other privileges defined on a particular resource.
The access permissions on null resources (defined in [RFC2518],
Section 3) are solely those they inherit (if any), and they are not
discoverable (i.e., the access control properties specified in
Section 5 are not defined on null resources). On the transition from
null to stateful resource, the initial access control list is set by
the server's default ACL value policy (if any).
Server implementations MAY define new privileges beyond those defined
in this specification. Privileges defined by individual
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implementations MUST NOT use the DAV: namespace, and instead should
use a namespace that they control, such as an http scheme URL.
3.1 DAV:read Privilege
The read privilege controls methods that return information about the
state of the resource, including the resource's properties. Affected
methods include GET and PROPFIND. Additionally, the read privilege
MAY control the OPTIONS method.
3.2 DAV:write Privilege
The write privilege controls methods that modify the content, dead
properties, or (in the case of a collection) membership of the
resource, such as PUT and PROPPATCH. Note that state modification is
also controlled via locking (see section 5.3 of [WEBDAV]), so
effective write access requires that both write privileges and write
locking requirements are satisfied.
3.3 DAV:read-acl Privilege
The DAV:read-acl privilege controls the use of PROPFIND to retrieve
the DAV:acl property of the resource.
3.4 DAV:read-current-user-privilege-set Privilege
The DAV:read-current-user-privilege-set privilege controls the use of
PROPFIND to retrieve the DAV:current-user-privilege-set property of
the resource.
Clients are intended to use this property to visually indicate in
their UI items that are dependent on the permissions of a resource,
for example, by graying out resources that are not writeable.
This privilege is separate from DAV:read-acl because there is a need
to allow most users access to the privileges permitted the current
user (due to its use in creating the UI), while the full ACL contains
information that may not be appropriate for the current authenticated
user. As a result, the set of users who can view the full ACL is
expected to be much smaller than those who can read the current user
privilege set, and hence distinct privileges are needed for each.
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3.5 DAV:write-acl Privilege
The DAV:write-acl privilege controls use of the ACL method to modify
the DAV:acl property of the resource.
3.6 DAV:all Privilege
DAV:all is an aggregate privilege that contains the entire set of
privileges that can be applied to the resource.
3.7 Aggregation of Predefined Privileges
Server implementations are free to aggregate the predefined
privileges (defined above in Sections 3.1-3.6) subject to the
following limitations:
DAV:read-acl MUST NOT contain DAV:read, DAV:write, DAV:write-acl, or
DAV:read-current-user-privilege-set.
DAV:write-acl MUST NOT contain DAV:write, DAV:read, DAV:read-acl, or
DAV:read-current-user-privilege-set.
DAV:read-current-user-privilege-set MUST NOT contain DAV:write,
DAV:read, DAV:read-acl, or DAV:write-acl.
DAV:write MUST NOT contain DAV:read, DAV:read-acl, or DAV:read-
current-user-privilege-set.
DAV:read MUST NOT contain DAV:write, or DAV:write-acl.
4 PRINCIPAL PROPERTIES
Principals are manifested to clients as a WebDAV resource, identified
by a URL. A principal MUST have a DAV:displayname property (defined
in Section 13.2 of [RFC2518]), and a DAV:resourcetype property
(defined in Section 13.9 of [RFC2518]). Additionally, a principal
MUST report the DAV:principal empty XML element in the value of the
DAV:resourcetype property in addition to all other reported elements.
For example, a collection principal would report DAV:collection and
DAV:principal elements. The element type declaration for
DAV:principal is:
This protocol defines the following additional property for a
principal. Since it is expensive, for many servers, to retrieve
access control information, the name and value of this property
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SHOULD NOT be returned by a PROPFIND allprop request (as defined in
Section 12.14.1 of [RFC2518]).
4.1 DAV:alternate-URI-set
This protected property, if non-empty, contains the URIs of network
resources with additional descriptive information about the
principal. This property identifies additional network resources
(i.e., it contains one or more URIs) that may be consulted by a
client to gain additional knowledge concerning a principal. One
expected use for this property is the storage of an ldap [RFC2255]
scheme URL. A user-agent encountering an ldap URL could use LDAP
[RFC2589] to retrieve additional machine-readable directory
information about the principal, and display that information in its
user interface. Support for this property is REQUIRED, and the value
is empty if no alternate URI exists for the principal.
4.2 DAV:principal-URL
This protected property contains the URL that MUST be used to
identify this principal in an ACL request.
5 ACCESS CONTROL PROPERTIES
This specification defines a number of new properties for WebDAV
resources. Access control properties may be retrieved just like
other WebDAV properties, using the PROPFIND method. Since it is
expensive, for many servers, to retrieve access control information,
a PROPFIND allprop request (as defined in Section 12.14.1 of
[RFC2518]) SHOULD NOT return the names and values of the properties
defined in this section.
HTTP resources that support the WebDAV Access Control Protocol MUST
contain the following properties. Null resources (described in
Section 3 of [RFC2518]) MUST NOT contain the following properties:
5.1 DAV:owner
This protected property identifies a particular principal as being
the "owner" of the resource. Since the owner of a resource often has
special access control capabilities (e.g., the owner frequently has
permanent DAV:write-acl privilege), clients might display the
resource owner in their user interface.
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5.1.1 Example: Retrieving DAV:owner
This example shows a client request for the value of the DAV:owner
property from a collection resource with URL
http://www.webdav.org/papers/. The principal making the request is
authenticated using Digest authentication. The value of DAV:owner is
the URL http://www.webdav.org/_acl/users/gstein, wrapped in the
DAV:href XML element.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="jim",
realm="jim@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
http://www.webdav.org/papers/
http://www.webdav.org/_acl/users/gstein
HTTP/1.1 200 OK
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5.1.2 Example: An Attempt to Set DAV:owner
The following example shows a client request to modify the value of
the DAV:owner property on the resource with URL
http://www.webdav.org/papers/. Since DAV:owner is a protected
property, the server responds with a 207 (Multi-Status) response that
contains a 403 (Forbidden) status code for the act of setting
DAV:owner. Section 8.2.1 of [RFC2518] describes PROPPATCH status code
information, and Section 11 of [RFC2518] describes the Multi-Status
response.
>> Request <<
PROPPATCH /papers/ HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="jim",
realm="jim@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
http://www.webdav.org/_acl/users/jim
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
http://www.webdav.org/papers/
HTTP/1.1 403 Forbidden
Failure to set protected property
(DAV:owner)
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5.2 DAV:supported-privilege-set
This is a protected property that identifies the privileges defined
for the resource.
Each privilege appears as an XML element, where aggregate
privileges list as sub-elements all of the privileges that they
aggregate.
An abstract privilege MUST NOT be used in an ACE for that resource.
Servers MUST fail an attempt to set an abstract privilege.
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.
It is envisioned that a WebDAV ACL-aware administrative client would
list the supported privileges in a dialog box, and allow the user to
choose non-abstract privileges to apply in an ACE. The privileges
tree is useful programmatically to map well-known privileges (defined
by WebDAV or other standards groups) into privileges that are
supported by any particular server implementation. The privilege
tree also serves to hide complexity in implementations allowing large
number of privileges to be defined by displaying aggregates to the
user.
5.2.1 Example: Retrieving a List of Privileges Supported on a Resource
This example shows a client request for the DAV:supported-privilege-
set property on the resource http://www.webdav.org/papers/. The value
of the DAV:supported-privilege-set property is a tree of supported
privileges:
DAV:all (aggregate, abstract)
|
+-- DAV:read (aggregate)
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|
+-- DAV:read-acl (abstract)
+-- DAV:read-current-user-privilege-set (abstract)
+-- DAV:write (aggregate)
|
+-- DAV:write-acl (abstract)
This privilege tree is not normative, and many possible privilege
trees are possible.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="gclemm",
realm="gclemm@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
http://www.webdav.org/papers/
Any
operation
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Read any
object
Read
ACL
Read current user
privilege set property
Write any
object
Write
ACL
HTTP/1.1 200 OK
5.3 DAV:current-user-privilege-set
DAV:current-user-privilege-set is a protected property containing the
exact set of privileges (as computed by the server) granted to the
currently authenticated HTTP user. Aggregate privileges and their
contained privileges are listed. A user-agent can use the value of
this property to adjust its user interface to make actions
inaccessible (e.g., by graying out a menu item or button) for which
the current principal does not have permission. This is particularly
useful for an access control user interface, which can be constructed
without knowing the ACE combining semantics of the server. This
property is also useful for determining what operations the current
principal can perform, without having to actually execute an
operation.
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If the current user is granted a specific privilege, that privilege
must belong to the set of privileges that may be set on this
resource. Therefore, each element in the DAV:current-user-privilege-
set property MUST identify a non-abstract privilege from the
DAV:supported-privilege-set property.
5.3.1 Example: Retrieving the UserÆs Current Set of Assigned Privileges
Continuing the example from Section 5.2.1, this example shows a
client requesting the DAV:current-user-privilege-set property from
the resource with URL http://www.webdav.org/papers/. The username of
the principal making the request is ôkhare", and Digest
authentication is used in the request. The principal with username
ôkhare" has been granted the DAV:read privilege. Since the DAV:read
privilege contains the DAV:read-acl and DAV:read-current-user-
privilege-set privileges (see Section 5.2.1), the principal with
username ôkhare" can read the ACL property, and the DAV:current-user-
privilege-set property. However, the DAV:all, DAV:read-acl,
DAV:write-acl and DAV:read-current-user-privilege-set privileges are
not listed in the value of DAV:current-user-privilege-set, since (for
this example) they are abstract privileges. DAV:write is not listed
since the principal with username ôkhare" is not listed in an ACE
granting that principal write permission.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="khare",
realm="khare@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
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http://www.webdav.org/papers/
HTTP/1.1 200 OK
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.
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.
5.4.1 ACE Principal
The DAV:principal element identifies the principal to which this ACE
applies.
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.
The current user matches DAV:authenticated only if authenticated.
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The current user matches DAV:unauthenticated only if not
authenticated.
DAV:all is the union of DAV:authenticated, and DAV:unauthenticated.
For a given request, the user matches either DAV:authenticated, or
DAV:unauthenticated, but not both (that is, DAV:authenticated and
DAV:unauthenticated are disjoint sets).
The current user matches a DAV:property principal in a DAV:acl
property of a resource only if the value of the identified property
of that resource contains at most one DAV:href XML element, the URI
value of DAV:href identifies a principal, and the current user is
authenticated as being (or being a member of) that principal. For
example, if the DAV:property element contained , 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.
The current user matches DAV:self in a DAV:acl property of the
resource only if that resource is a principal object and the current
user is authenticated as being that principal or a member of that
principal collection.
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.
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..
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5.4.4 ACE Inheritance
The presence of a DAV:inherited element indicates that this ACE is
inherited from another resource that is identified by the URL
contained in a DAV:href element. An inherited ACE cannot be modified
directly, but instead the ACL on the resource from which it is
inherited must be modified.
Note that ACE inheritance is not the same as ACL initialization. ACL
initialization defines the ACL that a newly created resource will use
(if not specified). ACE inheritance refers to an ACE that is
logically shared - where an update to the resource containing an ACE
will affect the ACE of each resource that inherits that ACE. The
method by which ACLs are initialized or by which ACEs are inherited
is not defined by this document.
5.4.5 Example: Retrieving a ResourceÆs Access Control List
Continuing the example from Sections 5.2.1 and 5.3.1, this example
shows a client requesting the DAV:acl property from the resource with
URL http://www.webdav.org/papers/. There are two ACEs defined in this
ACL:
ACE #1: The principal collection identified by URL
http://www.webdav.org/_acl/groups/maintainers/ (the group of site
maintainers) is granted DAV:write privilege. Since (for this example)
DAV:write contains the DAV:write-acl privilege (see Section 5.2.1),
this means the ômaintainers" group can also modify the access control
list.
ACE #2: All principals (DAV:all) are granted the DAV:read privilege.
Since (for this example) DAV:read contains DAV:read-acl and DAV:read-
current-user-privilege-set, this means all users (including all
members of the ômaintainers" group) can read the DAV:acl property and
the DAV:current-user-privilege-set property.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="masinter",
realm="masinter@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
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>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
http://www.webdav.org/papers/
http://www.webdav.org/_acl/groups/maintainers/
HTTP/1.1 200 OK
5.5 DAV:acl-semantics
This is a protected property that defines the ACL semantics. These
semantics define how multiple ACEs that match the current user are
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combined, what are the constraints on how ACEs can be ordered, and
which principals must have an ACE. A client user interface could use
the value of this property to provide feedback to a human operator
concerning the impact of proposed changes to an ACL. Alternately, a
client can use this property to help it determine, before submitting
an ACL method invocation, what ACL changes it needs to make to
accomplish a specific goal (or whether that goal is even achievable
on this server).
Since it is not practical to require all implementations to use the
same ACL semantics, the DAV:acl-semantics property is used to
identify the ACL semantics for a particular resource. The DAV:acl-
semantics element is defined in Section 6.
5.5.1 Example: Retrieving DAV:acl-semantics
In this example, the client requests the value of the DAV:acl-
semantics property. Digest authentication provides credentials for
the principal operating the client. In this example, the ACE
combination semantics are DAV:first-match, described in Section
6.1.1, the ACE ordering semantics are not specified (some value other
than DAV:deny-before-grant, described in Section 6.2.1), the
DAV:allowed-ace element states that only one ACE is permitted for
each principal, and an ACE describing the privileges granted the
DAV:all principal must exist in every ACL.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="srcarter",
realm="srcarter@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
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Content-Length: xxx
http://www.webdav.org/papers/
HTTP/1.1 200 OK
5.6 DAV:principal-collection-set
This protected property contains zero, one, or more URLs that
identify a collection principal. It is expected that implementations
of this protocol will typically use a relatively small number of
locations in the URL namespace for principals, and collection
principals. In cases where this assumption holds, the DAV:principal-
collection-set property will contain a small set of URLs identifying
the top of a collection hierarchy containing multiple principals and
collection principals. An access control protocol user agent could
use the contents of DAV:principal-collection-set to retrieve the
DAV:displayname property (specified in Section 13.2 of [RFC2518]) of
all principals on that server, thereby yielding human-readable names
for each principal that could be displayed in a user interface.
Since different servers can control different parts of the URL
namespace, different resources on the same host MAY have different
DAV:principal-collection-set values. The collections specified in the
DAV:principal-collection-set MAY be located on different hosts from
the resource. The URLs in DAV:principal-collection-set SHOULD be http
or https scheme URLs. For security and scalability reasons, a server
MAY report only a subset of the entire set of known collection
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principals, and therefore clients should not assume they have
retrieved an exhaustive listing. Additionally, a server MAY elect to
report none of the collection principals it knows about, in which
case the property value would be empty.
The value of DAV:principal-collection-set gives the scope of the
DAV:principal-property-search REPORT (defined in Section 9.4).
Clients use the DAV:principal-property-search REPORT to populate
their user interface with a list of principals. Therefore, servers
that limit a client's ability to obtain principal information will
interfere with the client's ability to manipulate access control
lists, due to the difficulty of getting the URL of a principal for
use in an ACE.
5.6.1 Example: Retrieving DAV:principal-collection-set
In this example, the client requests the value of the DAV:principal-
collection-set property on the collection resource identified by URL
http://www.webdav.org/papers/. The property contains the two URLs,
http://www.webdav.org/_acl/users/ and
http://www.webdav.org/_acl/groups/, both wrapped in XML
elements. Digest authentication provides credentials for the
principal operating the client.
The client might reasonably follow this request with two separate
PROPFIND requests to retrieve the DAV:displayname property of the
members of the two collections (/_acl/users/ and /_acl_groups/). This
information could be used when displaying a user interface for
creating access control entries.
>> Request <<
PROPFIND /papers/ HTTP/1.1
Host: www.webdav.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="yarong",
realm="yarong@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
>> Response <<
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HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
http://www.webdav.org/papers/
http://www.webdav.org/_acl/users/
http://www.webdav.org/_acl/groups/
HTTP/1.1 200 OK
5.7 Example: PROPFIND to retrieve access control properties
The following example shows how access control information can be
retrieved by using the PROPFIND method to fetch the values of the
DAV:owner, DAV:supported-privilege-set, DAV:current-user-privilege-
set, and DAV:acl properties.
>> Request <<
PROPFIND /top/container/ HTTP/1.1
Host: www.foo.org
Content-type: text/xml; charset="utf-8"
Content-Length: xxx
Depth: 0
Authorization: Digest username="ejw",
realm="users@foo.org", nonce="...",
uri="/top/container/", response="...", opaque="..."
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>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
http://www.foo.org/top/container/
http://www.foo.org/users/gclemm
Any operation
Read any
object
Write any
object
Create an
object
Update an
object
Delete an
object
Read the ACL
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Write the
ACL
http://www.foo.org/users/esedlar
http://www.foo.org/groups/marketing/
http://www.foo.org/top/
HTTP/1.1 200 OK
The value of the DAV:owner property is a single DAV:href XML element
containing the URL of the principal that owns this resource.
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The value of the DAV:supported-privilege-set property is a tree of
supported privileges:
DAV:all (aggregate, abstract)
|
+-- DAV:read
+-- DAV:write (aggregate, abstract)
|
+-- http://www.webdav.org/acl/create
+-- http://www.webdav.org/acl/update
+-- http://www.webdav.org/acl/delete
+-- DAV:read-acl
+-- DAV:write-acl
The DAV:current-user-privilege-set property contains two privileges,
DAV:read, and DAV:read-acl. This indicates that the current
authenticated user only has the ability to read the resource, and
read the DAV:acl property on the resource.
The DAV:acl property contains a set of four ACEs:
ACE #1: The principal identified by the URL
http://www.foo.org/users/esedlar is granted the DAV:read, DAV:write,
and DAV:read-acl privileges.
ACE #2: The principals identified by the URL
http://www.foo.org/groups/marketing/ are denied the DAV:read
privilege. In this example, the principal URL identifies a group,
which is represented by a collection principal.
ACE #3: In this ACE, the principal is a property principal,
specifically the DAV:owner property. When evaluating this ACE, the
value of the DAV:owner property is retrieved, and is examined to see
if it contains a DAV:href XML element. If so, the URL within the
DAV:href element is read, and identifies a principal. In this ACE,
the owner is granted DAV:read-acl, and DAV:write-acl privileges.
ACE #4: This ACE grants the DAV:all principal (all users) the
DAV:read privilege. This ACE is inherited from the resource
http://www.foo.org/top/, the parent collection of this resource.
6 ACL SEMANTICS
The ACL semantics define how multiple ACEs that match the current
user are combined, what are the constraints on how ACEs can be
ordered, and which principals must have an ACE.
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6.1 ACE Combination
The DAV:ace-combination element defines how privileges from multiple
ACEs that match the current user will be combined to determine the
access privileges for that user. Multiple ACEs may match the same
user because the same principal can appear in multiple ACEs, because
multiple principals can identify the same user, and because one
principal can be a member of another principal.
6.1.1 DAV:first-match ACE Combination
The ACEs are evaluated in the order in which they appear in the ACL.
If the first ACE that matches the current user does not grant all the
privileges needed for the request, the request MUST fail.
6.1.2 DAV:all-grant-before-any-deny ACE Combination
The ACEs are evaluated in the order in which they appear in the ACL.
If an evaluated ACE denies a privilege needed for the request, the
request MUST fail. If all ACEs have been evaluated without the user
being granted all privileges needed for the request, the request MUST
fail.
6.1.3 DAV:specific-deny-overrides-grant ACE Combination
All ACEs in the ACL are evaluated. An "individual ACE" is one whose
principal identifies the current user. A "group ACE" is one whose
principal is a collection that contains a principal that identifies
the current user. A privilege is granted if it is granted by an
individual ACE and not denied by an individual ACE, or if it is
granted by a group ACE and not denied by an individual or group ACE.
A request MUST fail if any of its needed privileges are not granted.
6.2 ACE Ordering
The DAV:ace-ordering element defines a constraint on how the ACEs can
be ordered in the ACL.
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6.2.1 DAV:deny-before-grant ACE Ordering
This element indicates that all deny ACEs must precede all grant
ACEs.
6.3 Allowed ACE
The DAV:allowed-ace XML element specifies constraints on what kinds
of ACEs are allowed in an ACL.
6.3.1 DAV:principal-only-one-ace ACE Constraint
This element indicates that a principal can appear in only one ACE
per resource.
6.3.2 DAV:grant-only ACE Constraint
This element indicates that ACEs with deny clauses are not allowed.
6.4 Required Principals
The required principal elements identify which principals must have
an ACE defined in the ACL.
For example, the following element requires that the ACL contain a
DAV:owner property ACE:
7 ACCESS CONTROL AND EXISTING METHODS
This section defines the impact of access control functionality on
existing methods.
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7.1 OPTIONS
If the server supports access control, it MUST return "access-
control" as a field in the DAV response header from an OPTIONS
request on any resource implemented by that server.
7.1.1 Example - OPTIONS
>> Request <<
OPTIONS /foo.html HTTP/1.1
Host: www.webdav.org
Content-Length: 0
>> Response <<
HTTP/1.1 200 OK
DAV: 1, 2, access-control
Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL
In this example, the OPTIONS response indicates that the server
supports access control and that /foo.html can have its access
control list modified by the ACL method.
7.2 MOVE
When a resource is moved from one location to another due to a MOVE
request, the non-inherited and non-protected ACEs in the DAV:acl
property of the resource MUST NOT be modified, or the MOVE request
fails. Handling of inherited and protected ACEs is intentionally
undefined to give server implementations flexibility in how they
implement ACE inheritance and protection.
7.3 COPY
The DAV:acl property on the resource at the destination of a COPY
MUST be the same as if the resource was created by an individual
resource creation request (e.g. MKCOL, PUT). Clients wishing to
preserve the DAV:acl property across a copy need to read the DAV:acl
property prior to the COPY, then perform an ACL operation on the new
resource at the destination to restore, insofar as this is possible,
the original access control list.
7.4 DELETE
The precise combination of privileges and resources necessary to
permit the DELETE method is intentionally left to the discretion of
each server implementation. It is envisioned that on some servers,
DELETE will require write permission on the collection containing the
resource to be deleted. On other servers, it might also require
write permission on the resource being deleted.
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7.5 LOCK
A lock on a resource ensures that only the lock owner can modify ACEs
that are not inherited and not protected (these are the only ACEs
that a client can modify with an ACL request). A lock does not
protect inherited or protected ACEs, since a client cannot modify
them with an ACL request on that resource.
8 ACCESS CONTROL METHODS
8.1 ACL
The ACL method modifies the access control list (which can be read
via the DAV:acl property) of a resource. Specifically, the ACL
method only permits modification to ACEs that are not inherited, and
are not protected. An ACL method invocation modifies all non-
inherited and non-protected ACEs in a resourceÆs access control list
to exactly match the ACEs contained within in the DAV:acl XML element
(specified in Section 5.4) of the request body. An ACL request body
MUST contain only one DAV:acl XML element. Unless the non-inherited
and non-protected ACEs of the DAV:acl property of the resource can be
updated to be exactly the value specified in the ACL request, the ACL
request MUST fail.
It is possible that the ACEs visible to the current user in the
DAV:acl property may only be a portion of the complete set of ACEs on
that resource. If this is the case, an ACL request only modifies the
set of ACEs visible to the current user, and does not affect any non-
visible ACE.
In order to avoid overwriting DAV:acl changes by another client, a
client SHOULD acquire a WebDAV lock on the resource before retrieving
the DAV:acl property of a resource that it intends on updating.
Implementation Note: Two common operations are to add or remove an
ACE from an existing access control list. To accomplish this, a
client uses the PROPFIND method to retrieve the value of the
DAV:acl property, then parses the returned access control list to
remove all inherited and protected ACEs (these ACEs are tagged
with the DAV:inherited and DAV:protected XML elements). In the
remaining set of non-inherited, non-protected ACEs, the client can
add or remove one or more ACEs before submitting the final ACE set
in the request body of the ACL method.
8.1.1 ACL Preconditions
An implementation MAY enforce one or more of the following
constraints on an ACL request. If the constraint is violated, a 403
(Forbidden) response MUST be returned and the indicated XML element
MUST be returned as the top level element in an XML response body.
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: A conflict exists between two or more ACEs
submitted in the ACL request.
: A conflict exists between an ACE in
the ACL request and a protected ACE on the resource. For example, if
the resource has a protected ACE granting DAV:write to a given
principal, then it would be a protected ACE conflict if the ACL
request submitted an ACE denying DAV:write to the same principal.
: A conflict exists between an ACE in
the ACL request and an inherited ACE on the resource. For example, if
the resource inherits an ACE from its parent collection granting
DAV:write to a given principal, then it would be an inherited ACE
conflict if the ACL request submitted an ACE denying DAV:write to the
same principal. Note that reporting of this error will be
implementation-dependent. Implementations have the choice to either
report this error, or to allow the ACE to be set, and then let normal
ACE evaluation rules determine whether the new ACE has any impact on
the privileges available to a specific principal.
: An implementation MAY limit the number of ACEs
in an ACL. However, ACL-compliant servers MUST support at least one
ACE granting privileges to a single principal, and one ACE granting
privileges to a collection principal.
: All non-inherited deny ACEs MUST precede
all non-inherited grant ACEs.
: For implementations that have the
DAV:principal-only-one-ace constraint (defined in Section 6.3.1),
this XML element indicates that fulfilling the ACL request would
result in multiple ACEs for one or more principals.
: For implementations that have the DAV:grant-only
constraint (defined in Section 6.3.2), this XML element indicates the
request contained one or more deny ACEs.
: The ACL request attempts to set an abstract
privilege in an ACE (see Section 5.2).
: One or more of the privileges in the ACL
request is not supported by the resource.
: One or more required principals (see
Section 6.4) would not be present in the access control list after
processing the ACL request. The DAV:required-principal XML element
MUST contain a list of the missing principal(s), following the syntax
specified in Section 6.4.
: One or more of the principal URLs in the
ACL request does not identify a principal resource.
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: One or more of the principal URLs in the
ACL request is not allowed in an ACE. For example, a server where
only authenticated principals can access resources would not allow
the DAV:all or DAV:unauthenticated principals to be used in an ACE,
since these would allow unauthenticated access to resources.
8.1.2 Example: the ACL method
In the following example, user "fielding", authenticated by
information in the Authorization header, grants the principal
identified by the URL http://www.foo.org/users/esedlar (i.e., the
user "esedlar") read and write privileges, grants the owner of the
resource read-acl and write-acl privileges, and grants everyone read
privileges.
>> Request <<
ACL /top/container/ HTTP/1.1
Host: www.foo.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Authorization: Digest username="fielding",
realm="users@foo.org", nonce="...",
uri="/top/container/", response="...", opaque="..."
http://www.foo.org/users/esedlar
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>> Response <<
HTTP/1.1 200 OK
8.1.3 Example: ACL method failure due to protected ACE conflict
In the following request, user "fielding", authenticated by
information in the Authorization header, attempts to deny the
principal identified by the URL http://www.foo.org/users/esedlar
(i.e., the user "esedlar") write privileges. Prior to the request,
the DAV:acl property on the resource contained a protected ACE (see
Section 5.4.3) granting DAV:owner the DAV:read and DAV:write
privileges. The principal identified by URL
http://www.foo.org/users/esedlar is the owner of the resource. The
ACL method invocation fails because the submitted ACE conflicts with
the protected ACE, thus violating the semantics of ACE protection.
>> Request <<
ACL /top/container/ HTTP/1.1
Host: www.foo.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Authorization: Digest username="fielding",
realm="users@foo.org", nonce="...",
uri="/top/container/", response="...", opaque="..."
http://www.foo.org/users/esedlar
>> Response <<
HTTP/1.1 403 Forbidden
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
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8.1.4 Example: ACL method failure due to an inherited ACE conflict
In the following request, user "ejw", authenticated by information in
the Authorization header, tries to change the access control list on
the resource http://www.foo.org/top/index.html. This resource has two
inherited ACEs.
Inherited ACE #1 grants the principal identified by URL
http://www.foo.org/users/ejw (i.e., the user "ejw")
http://www.foo.org/privs/write-all and DAV:read-acl privileges. On
this server, http://www.foo.org/privs/write-all is an aggregate
privilege containing DAV:write, and DAV:write-acl.
Inherited ACE #2 grants principal DAV:all the DAV:read privilege.
The request attempts to set a (non-inherited) ACE, denying the
principal identified by the URL http://www.foo.org/users/ejw (i.e.,
the user ôejw") DAV:write permission. This conflicts with inherited
ACE #1. Note that the decision to report an inherited ACE conflict is
specific to this server implementation. Another server implementation
could have allowed the new ACE to be set, and then used normal ACE
evaluation rules to determine whether the new ACE has any impact on
the privileges available to a principal.
>> Request <<
ACL /top/index.html HTTP/1.1
Host: www.foo.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Authorization: Digest username="ejw",
realm="users@foo.org", nonce="...",
uri="/top/index.html", response="...", opaque="..."
http://www.foo.org/users/ejw
>> Response <<
HTTP/1.1 403 Forbidden
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
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8.1.5 Example: ACL method failure due to an attempt to set grant and
deny in a single ACE.
In this example, user "ygoland", authenticated by information in the
Authorization header, tries to change the access control list on the
resource http://www.foo.org/diamond/engagement-ring.gif. The ACL
request includes a single, syntactically and semantically incorrect
ACE, which attempts to grant the collection principal identified by
the URL http://www.foo.org/users/friends/ DAV:read privilege and deny
the principal identified by URL http://www.foo.org/users/ygoland-so
(i.e., the user "ygoland-so") DAV:read privilege. However, it is
illegal to have multiple principal elements, as well as both a grant
and deny element in the same ACE, so the request fails due to poor
syntax.
>> Request <<
ACL /diamond/engagement-ring.gif HTTP/1.1
Host: www.foo.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Authorization: Digest username="ygoland",
realm="users@foo.org", nonce="...",
uri="/diamond/engagement-ring.gif", response="...", opaque="..."
http://www.foo.org/users/friends/
http://www.foo.org/users/ygoland-so
>> Response <<
HTTP/1.1 400 Bad Request
Content-Length: 0
Note that if the request had been divided into two ACEs, one to
grant, and one to deny, the request would have been syntactically
well formed.
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9 ACCESS CONTROL REPORTS
9.1 REPORT Method
The REPORT method (defined in Section 3.6 of [RFCxxxx]) provides an
extensible mechanism for obtaining information about a resource.
Unlike the PROPFIND method, which returns the value of one or more
named properties, the REPORT method can involve more complex
processing. REPORT is valuable in cases where the server has access
to all of the information needed to perform the complex request (such
as a query), and where it would require multiple requests for the
client to retrieve the information needed to perform the same
request.
9.2 DAV:acl-principal-props Report
The DAV:acl-principle-props report returns, for all principals in the
DAV:acl property that are identified by http(s) URLs, the value of
the properties specified in the REPORT request body. In the case
where a principal URL appears multiple times, the DAV:acl-principal-
props report MUST return the properties for that principal only once.
Marshalling
The request body MUST be a DAV:acl-principal-props XML element.
ANY value: a sequence of one or more elements, with at most one
DAV:prop element.
prop: see RFC 2518, Section 12.11
The response body for a successful request MUST be a DAV:multistatus
XML element (i.e., the response uses the same format as the response
for PROPFIND).
multistatus: see RFC 2518, Section 12.9
The response body for a successful DAV:acl-principal-props REPORT
request MUST contain a DAV:response element for each principal
identified by an http(s) URL listed in a DAV:principal XML element of
an ACE within the DAV:acl property of the resource identified by the
Request-URI.
9.2.1 Example: DAV:acl-principal-props Report
Resource http://www.webdav.org/index.html has an ACL with three ACEs:
ACE #1: All principals (DAV:all) have DAV:read and DAV:read-current-
user-privilege-set access.
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ACE #2: The principal identified by
http://www.webdav.org/people/gstein (the user ôgstein") is granted
DAV:write, DAV:write-acl, DAV:read-acl privileges.
ACE #3: The collection principal identified by
http://www.webdav.org/groups/authors/ (the ôauthors" group) is
granted DAV:write and DAV:read-acl privileges.
The following example shows a DAV:acl-principal-props report
requesting the DAV:displayname property. It returns the value of
DAV:displayname for resources http://www.webdav.org/people/gstein and
http://www.webdav.org/groups/authors/ , but not for DAV:all, since
this is not an http(s) URL.
>> Request <<
REPORT /index.html HTTP/1.1
Host: www.webdav.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://www.webdav.org/people/gstein
Greg Stein
HTTP/1.1 200 OK
http://www.webdav.org/groups/authors/
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Site authors
HTTP/1.1 200 OK
9.3 DAV:principal-match REPORT
The DAV:principal-match REPORT is used to identify all members of a
collection that match the current user. In particular, if the
collection contains principals, the report can be used to identify
all members of the collection that match the current user.
Alternatively, if the collection contains resources that have a
property that identifies a principal (e.g. DAV:owner), then the
report can be used to identify all members of the collection whose
property identifies a principal that matches the current user. For
example, this report can return all of the resources in a collection
hierarchy that are owned by the current user.
The Depth header (defined in Section 9.2 of [RFC2518]), with value
"infinity", can be used with this report. In this case, the report
operates on the collection in the Request-URI, as well as all child
collections, grandchild collections, etc.
Marshalling:
The request body MUST be a DAV:principal-match XML element.
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
prop: see RFC 2518, Section 12.11
The response body for a successful request MUST be a DAV:multistatus
XML element.
multistatus: see RFC 2518, Section 12.9
The response body for a successful DAV:principal-match REPORT request
MUST contain a DAV:response element for each member of the collection
that matches the current user. When the DAV:principal-property
element is used, a match occurs if the current user is the same as
the principal identified by the URI found in the DAV:href element of
the property identified by the DAV:principal-property element. When
the DAV:self element is used in a DAV:principal-match report issued
against a collection principal, it matches a child of the collection
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principal if that child (a principal resource) identifies the same
principal as the current user.
If DAV:prop is specified in the request body, the properties
specified in the DAV:prop element MUST be reported in the
DAV:response elements.
9.3.1 Example: DAV:principal-match REPORT
The following example identifies the members of the collection
identified by the URL http://www.webdav.org/doc/ that are owned by
the current user. The current user (ôgclemm") is authenticated using
Digest authentication.
>> Request <<
REPORT /doc/ HTTP/1.1
Host: www.webdav.org
Authorization: Digest username="gclemm",
realm="gclemm@webdav.org", nonce="...",
uri="/papers/", response="...", opaque="..."
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Depth: infinity
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
http://www.webdav.org/doc/foo.html
HTTP/1.1 200 OK
http://www.webdav.org/doc/img/bar.gif
HTTP/1.1 200 OK
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9.4 DAV:principal-property-search REPORT
The DAV:principal-property-search REPORT performs a substring search
on the character data value of specified properties. The server MUST
perform caseless matching of substrings. Only properties defined on
principal or collection principal resources are searched. For
implementation efficiency, servers do not typically support substring
searching on all properties. A client can discover the set of
searchable properties by using the principal-search-property-set
REPORT, defined in Section 9.5.
Implementation Note: The value of a WebDAV property is a sequence
of well-formed XML, and hence can include any character in the
Unicode/ISO-10646 standard, that is, most known characters in
human languages. Due to the idiosyncrasies of case mapping across
human languages, implementation of caseless matching is non-
trivial. Implementors are strongly encouraged to consult
[CaseMap], especially Section 2.3 ("Caseless Matching"), for
guidance when implementing their caseless matching algorithms.
Marshalling:
The DAV:principal-collection-set property of the resource identified
by the Request-URI specifies the scope of the DAV:principal-property-
search REPORT, as follows:
- All principal and collection principal resources identified in
DAV:principal-collection-set are searched
- All principal and collection principal resources that are
descendents of a collection principal resource identified in
DAV:principal collection-set are searched.
Servers MUST support the DAV:principal-property-search REPORT on all
principal collections identified in the value of a DAV:principal-
collection-set property.
The request body MUST be a DAV:principal-property-search XML element
containing a search specification and an optional list of properties.
For every principal that matches the search specification, the
response will contain the value of the properties on that principal.
The DAV:property-search element contains a prop element enumerating
the properties to be searched and a caseless-substring element,
containing the search string.
prop: see RFC 2518, Section 12.11
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Multiple property-search elements or multiple elements within a
DAV:prop element will be interpreted with a logical AND. An empty
DAV:caseless-substring element will match all properties specified in
its parent DAV:property-search element.
The response body for a successful request MUST be a DAV:multistatus
XML element.
multistatus: see RFC 2518, Section 12.9
The response body for a successful DAV:principal-property-search
REPORT request MUST contain a DAV:response element for each
principal whose property values satisfy the search specification
given in DAV:principal-property-search.
If DAV:prop is specified in the request body, the properties
specified in the DAV:prop element MUST be reported in the
DAV:response elements.
Errors:
If a request specifies a search of a property that is not
searchable, a 403 (Forbidden) response MUST be returned and the
response body MUST be a DAV:non-searchable-property element,
containing the unsearchable properties.
9.4.1 Matching
There are several cases to consider when matching strings. The
easiest case is when a property value is "simple" and has only
character information item content (see [REC-XMLINFOSET]). For
example, the search string "julian" would match the DAV:displayname
property with value "Julian Reschke". Note that the on-the-wire
marshalling of DAV:displayname in this case is:
Julian Reschke
The name of the property is encoded into the XML element information
item, and the character information item content of the property is
"Julian Reschke".
The more complicated case occurred when properties have mixed content
(that is, compound values consisting of multiple child element items,
other types of information items, and character information item
content). Consider the property http://www.webdav.org/props/aprop,
marshalled as:
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{cdata 0}{cdata 1}
{cdata 2}{cdata 3}
In this case, substring matching is performed on each individual
contiguous sequence of character information items. In the example
above, a search string would be compared to the four following
strings:
{cdata 0}
{cdata 1}
{cdata 2}
{cdata 3}
That is, four individual caseless substring matches would be
performed, one each for {cdata 0}, {cdata 1}, {cdata 2}, and {cdata
3}.
9.4.2 Example: successful DAV:principal-property-search REPORT
In this example, the client requests the principal URLs of all users
whose DAV:displayname property contains the substring "doE" and whose
http://BigCorp.com/ns/title property (that is, their professional
title) contains "sales". In addition, the client requests five
properties to be returned with the matching principals:
In the DAV: namespace: displayname
In the http://www.BigCorp.com/ns/ namespace: department, phone,
office, salary
The response shows that two principal resources meet the search
specification, "John Doe" and "Zygdoebert Smith". The property
"salary" in namespace "http://www.BigCorp.com/ns/" is not returned,
since the principal making the request does not have sufficient
access permissions to read this property.
>> Request <<
REPORT /users/ HTTP/1.1
Host: www.BigCorp.com
Content-Type: text/xml; charset=utf-8
Content-Length: xxxx
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doE
sales
>> Response <<
HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset=utf-8
Content-Length: xxxx
http://www.BigCorp.com/users/jdoe
John Doe
Widget Sales
234-4567
209
HTTP/1.1 200 OK
HTTP/1.1 403 Forbidden
http://www.BigCorp.com/users/zsmith
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Zygdoebert Smith
Gadget Sales
234-7654
114
HTTP/1.1 200 OK
HTTP/1.1 403 Forbidden
9.4.3 Example: Unsuccessful DAV:principal-property-search REPORT
In this example, the client requests a search on the non-searchable
property "phone" in the namespace "http://www.BigCorp.com/ns/". The
response is a 403 (Forbidden), with a response body containing the
XML element DAV:non-searchable-property listing the non-searchable
property.
>> Request <<
REPORT /users/ HTTP/1.1
Host: www.BigCorp.com
Content-Type: text/xml; charset=utf-8
Content-Length: xxxx
232
>> Response <<
HTTP/1.1 403 FORBIDDEN
Content-Type: text/xml; charset=utf-8
Content-Length: xxxx
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9.5 DAV:principal-search-property-set REPORT
The DAV:principal-search-property-set REPORT identifies those
properties that may be searched using the DAV:principal-property-
search REPORT (defined in Section 9.4). The DAV:principal-collection-
set property of the resource identified by the Request-URI specifies
the scope of the DAV:principal-search-property-set REPORT, as
follows:
- All principal and collection principal resources identified in
DAV:principal-collection-set are in scope
- All principal and collection principal resources that are
descendents of a collection principal resource identified in
DAV:principal collection-set are also in scope.
Principals and collection principals within this scope are examined
for searchable properties.
Servers MUST support the DAV:principal-search-property-set REPORT on
all principal collections identified in the value of a DAV:principal-
collection-set property.
An access control protocol user agent could use the results of the
DAV:principal-search-property-set REPORT to present a query interface
to the user for retrieving principals.
Marshalling:
The request body MUST be an empty DAV:principal-search-property-set
XML element.
The response body MUST be a DAV:principal-search-property-set XML
element, containing a DAV:principal-search-property XML element for
each property that may be searched with the DAV:principal-property-
search REPORT. A server MAY limit its response to just a subset of
the searchable properties, such as those likely to be useful to an
interactive access control client.
Each DAV:principal-search-property XML element contains exactly one
searchable property, and a description of the property.
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The DAV:prop element contains one principal property on which the
server is able to perform DAV:principal-property-search REPORTs.
prop: see RFC 2518, Section 12.11
The description element is a human-readable description of what
information this property represents. Servers MUST indicate the human
language of the description using the xml:lang attribute and SHOULD
consider the HTTP Accept-Language request header when selecting one
of multiple available languages.
9.5.1 Example: DAV:principal-search-property-set REPORT
In this example, the client determines the set of searchable
principal properties by requesting the DAV:principal-search-property-
set REPORT on the root of the serverÆs principal URL collection set,
identified by http://www.BigCorp.com/users/.
>> Request <<
REPORT /users/ HTTP/1.1
Host: www.BigCorp.com
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
Accept-Language: en, de
Authorization: BASIC d2FubmFtYWs6cGFzc3dvcmQ=
>> Response <<
HTTP/1.1 200 OK
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
Full name
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Job title
10 XML PROCESSING
Implementations of this specification MUST support the XML element
ignore rule, as specified in Section 23.3.2 of [RFC2518], and the XML
Namespace Recommendation [REC-XML-NAMES].
Note that use of the DAV namespace is reserved for XML elements and
property names defined in a standards-track or Experimental IETF RFC.
11 INTERNATIONALIZATION CONSIDERATIONS
In this specification, the only human-readable content can be found
in the description XML element, found within the DAV:supported-
privilege-set property. This element contains a human-readable
description of the capabilities controlled by a privilege. As a
result, the description element must be capable of representing
descriptions in multiple character sets. Since the description
element is found within a WebDAV property, it is represented on-the-
wire as XML [REC-XML], and hence can leverage XML's language tagging
and character set encoding capabilities. Specifically, XML processors
must, at minimum, be able to read XML elements encoded using the UTF-
8 [UTF-8] encoding of the ISO 10646 multilingual plane. XML examples
in this specification demonstrate use of the charset parameter of the
Content-Type header, as defined in [RFC3023], as well as the XML
"encoding" attribute, which together provide charset identification
information for MIME and XML processors. Furthermore, this
specification requires server implementations to tag description
fields with the xml:lang attribute (see Section 2.12 of [REC-XML]),
which specifies the human language of the description. Additionally,
server implementations should take into account the value of the
Accept-Language HTTP header to determine which description string to
return.
For XML elements other than the description element, it is expected
that implementations will treat the property names, privilege names,
and values as tokens, and convert these tokens into human-readable
text in the user's language and character set when displayed to a
person. Only a generic WebDAV property display utility would display
these values in their raw form to a human user.
For error reporting, we follow the convention of HTTP/1.1 status
codes, including with each status code a short, English description
of the code (e.g., 200 (OK)). While the possibility exists that a
poorly crafted user agent would display this message to a user,
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internationalized applications will ignore this message, and display
an appropriate message in the user's language and character set.
Further internationalization considerations for this protocol are
described in the WebDAV Distributed Authoring protocol specification
[RFC2518].
12 SECURITY CONSIDERATIONS
Applications and users of this access control protocol should be
aware of several security considerations, detailed below. In addition
to the discussion in this document, the security considerations
detailed in the HTTP/1.1 specification [RFC2616], the WebDAV
Distributed Authoring Protocol specification [RFC2518], and the XML
Media Types specification [RFC3023] should be considered in a
security analysis of this protocol.
12.1 Increased Risk of Compromised Users
In the absence of a mechanism for remotely manipulating access
control lists, if a single user's authentication credentials are
compromised, only those resources for which the user has access
permission can be read, modified, moved, or deleted. With the
introduction of this access control protocol, if a single compromised
user has the ability to change ACLs for a broad range of other users
(e.g., a super-user), the number of resources that could be altered
by a single compromised user increases. This risk can be mitigated by
limiting the number of people who have write-acl privileges across a
broad range of resources.
12.2 Risks of the DAV:read-acl and DAV:current-user-privilege-set
Privileges
The ability to read the access privileges (stored in the DAV:acl
property), or the privileges permitted the currently authenticated
user (stored in the DAV:current-user-privilege-set property) on a
resource may seem innocuous, since reading an ACL cannot possibly
affect the resource's state. However, if all resources have world-
readable ACLs, it is possible to perform an exhaustive search for
those resources that have inadvertently left themselves in a
vulnerable state, such as being world-writeable. In particular, the
property retrieval method PROPFIND, executed with Depth infinity on
an entire hierarchy, is a very efficient way to retrieve the DAV:acl
or DAV:current-user-privilege-set properties. Once found, this
vulnerability can be exploited by a denial of service attack in which
the open resource is repeatedly overwritten. Alternately, writeable
resources can be modified in undesirable ways.
To reduce this risk, read-acl privileges should not be granted to
unauthenticated principals, and restrictions on read-acl and read-
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current-user-privilege-set privileges for authenticated principals
should be carefully analyzed when deploying this protocol. Access to
the current-user-privilege-set property will involve a tradeoff of
usability versus security. When the current-user-privilege-set is
visible, user interfaces are expected to provide enhanced information
concerning permitted and restricted operations, yet this information
may also indicate a vulnerability that could be exploited. Deployment
of this protocol will need to evaluate this tradeoff in light of the
requirements of the deployment environment.
12.3 No Foreknowledge of Initial ACL
In an effort to reduce protocol complexity, this protocol
specification intentionally does not address the issue of how to
manage or discover the initial ACL that is placed upon a resource
when it is created. The only way to discover the initial ACL is to
create a new resource, then retrieve the value of the DAV:acl
property. This assumes the principal creating the resource also has
been granted the DAV:read-acl privilege.
As a result, it is possible that a principal could create a resource,
and then discover that its ACL grants privileges that are
undesirable. Furthermore, this protocol makes it possible (though
unlikely) that the creating principal could be unable to modify the
ACL, or even delete the resource. Even when the ACL can be modified,
there will be a short period of time when the resource exists with
the initial ACL before its new ACL can be set.
Several factors mitigate this risk. Human principals are often aware
of the default access permissions in their editing environments and
take this into account when writing information. Furthermore, default
privilege policies are usually very conservative, limiting the
privileges granted by the initial ACL.
13 AUTHENTICATION
Authentication mechanisms defined for use with HTTP and WebDAV also
apply to this WebDAV Access Control Protocol, in particular the Basic
and Digest authentication mechanisms defined in [RFC2617].
14 IANA CONSIDERATIONS
This document uses the namespace defined by [RFC2518] for XML
elements. All other IANA considerations mentioned in [RFC2518] also
applicable to WebDAV ACL.
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15 INTELLECTUAL PROPERTY
The following notice is copied from RFC 2026, section 10.4, and
describes the position of the IETF concerning intellectual property
claims made against this document.
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use other technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementers or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
16 ACKNOWLEDGEMENTS
This protocol is the collaborative product of the WebDAV ACL design
team: Bernard Chester, Geoff Clemm, Anne Hopkins, Barry Lind, Sean
Lyndersay, Eric Sedlar, Greg Stein, and Jim Whitehead. The authors
are grateful for the detailed review and comments provided by Jim
Amsden, Gino Basso, Murthy Chintalapati, Dennis Hamilton, Laurie
Harper, Ron Jacobs, Chris Knight, Remy Maucherat, Larry Masinter,
Yaron Goland, Lisa Dusseault, Joe Orton, Stefan Eissing, Julian
Reschke, Keith Wannamaker, Tim Ellison, and Dylan Barrell. We thank
Keith Wannamaker for the initial text of the principal property
search sections. Prior work on WebDAV access control protocols has
been performed by Yaron Goland, Paul Leach, Lisa Dusseault, Howard
Palmer, and Jon Radoff. We would like to acknowledge the foundation
laid for us by the authors of the DeltaV, WebDAV and HTTP protocols
upon which this protocol is layered, and the invaluable feedback from
the WebDAV working group.
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17 REFERENCES
17.1 Normative References
[RFC2119] S.Bradner, "Key words for use in RFCs to Indicate
Requirement Levels." RFC 2119, BCP 14, Harvard, March, 1997.
[REC-XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible
Markup Language (XML)." World Wide Web Consortium Recommendation REC-
xml.http://www.w3.org/TR/REC-xml
[REC-XML-NAMES] T. Bray, D. Hollander, A. Layman, ôName Spaces in
XML" World Wide Web Consortium Recommendation REC-xml-names.
http://www.w3.org/TR/REC-xml-names/
[RFCxxxx] G. Clemm, J. Amsden, T. Ellison, C. Kaler, J. Whitehead,
"Versioning Extensions to WebDAV." RFC xxxx. Rational, IBM,
Microsoft, U.C. Santa Cruz, 2001.
[REC-XML-INFOSET] J. Cowan, R. Tobin, "XML Information Set." World
Wide Web Consortium Recommendation REC-xml-infoset.
http://www.w3.org/TR/xml-infoset/
[RFC2616] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, L.
Masinter, P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol
-- HTTP/1.1." RFC 2616. U.C. Irvine, Compaq, Xerox, Microsoft,
MIT/LCS, June, 1999.
[RFC2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, P.
Leach, A. Luotonen, L. Stewart, "HTTP Authentication: Basic and
Digest Access Authentication." RFC 2617. Northwestern University,
Verisign, AbiSource, Agranat, Microsoft, Netscape, Open Market, June,
1999.
[RFC2518] Y. Goland, E. Whitehead, A. Faizi, S. R. Carter, D. Jensen,
"HTTP Extensions for Distributed Authoring -- WEBDAV." RFC 2518.
Microsoft, U.C. Irvine, Netscape, Novell, February, 1999.
[RFC2368] P. Hoffman, L. Masinter, J. Zawinski, "The mailto URL
scheme." RFC 2368. Internet Mail Consortium, Xerox, Netscape, July,
1998.
[RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types." RFC
3023. IBM Tokyo Research Laboratory, simonstl.com, Skymoon Ventures,
January, 2001.
[UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode and
ISO 10646." RFC 2279. Alis Technologies. January, 1998.
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17.2 Informational References
[RFC2026] S.Bradner, "The Internet Standards Process û Revision 3."
RFC 2026, BCP 9. Harvard, October, 1996.
[RFC2255] T. Howes, M. Smith, "The LDAP URL Format." RFC 2255.
Netscape, December, 1997.
[RFC2251] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
Protocol (v3)." RFC 2251. Critical Angle, Netscape, Isode, December,
1997.
[CaseMap] M. Davis, "Case Mappings", Unicode Technical Report #21,
18 AUTHORS' ADDRESSES
Geoffrey Clemm
Rational Software
20 Maguire Road
Lexington, MA 02421
Email: geoffrey.clemm@rational.com
Anne Hopkins
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
Email: annehop@microsoft.com
Eric Sedlar
Oracle Corporation
500 Oracle Parkway
Redwood Shores, CA 94065
Email: esedlar@us.oracle.com
Jim Whitehead
U.C. Santa Cruz
Dept. of Computer Science
Baskin Engineering
1156 High Street
Santa Cruz, CA 95064
Email: ejw@cse.ucsc.edu
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19 APPENDICIES
19.1 WebDAV XML Document Type Definition Addendum
All XML elements defined in this Document Type Definition (DTD)
belong to the DAV namespace. This DTD should be viewed as an addendum
to the DTD provided in [RFC2518], section 23.1.
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ANY value: a sequence of one or more elements, with at most one
DAV:prop element.
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
20 NOTE TO RFC EDITOR
As of the writing of this specification, the DeltaV protocol,
described in draft-ietf-deltav-versioning-20, has been approved by
the IESG, but not yet published as an RFC. Within this specification,
the DeltaV protocol is referenced as [RFCxxxx]. These references need
to be replaced with the actual RFC number. As well, the citation in
Section 17.1 also needs to be updated with the correct RFC number,
and the month of issue.
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