draft-ietf-webdav-acl-04.txt   draft-ietf-webdav-acl-05.txt 
INTERNET-DRAFT Geoffrey Clemm, Rational Software INTERNET-DRAFT Geoffrey Clemm, Rational Software
draft-ietf-webdav-acl-04 Anne Hopkins, Microsoft Corporation draft-ietf-webdav-acl-05 Anne Hopkins, Microsoft Corporation
Eric Sedlar, Oracle Corporation Eric Sedlar, Oracle Corporation
Jim Whitehead, U.C. Santa Cruz Jim Whitehead, U.C. Santa Cruz
Expires July 21, 2001 January 21, 2001 Expires July 21, 2001 April 23, 2001
WebDAV Access Control Protocol WebDAV Access Control Protocol
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering Task
Task Force (IETF), its areas, and its working groups. Note that other Force (IETF), its areas, and its working groups. Note that other groups
groups may also distribute working documents as Internet-Drafts. may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet- Drafts as reference material time. It is inappropriate to use Internet- Drafts as reference material
or to cite them other than as "work in progress." or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
skipping to change at page 27, line ? skipping to change at line 43
This document specifies a set of methods, headers, and message bodies This document specifies a set of methods, headers, and message bodies
that define the WebDAV Access Control extensions to the HTTP/1.1 that define the WebDAV Access Control extensions to the HTTP/1.1
protocol. This protocol permits a client to remotely read and modify protocol. This protocol permits a client to remotely read and modify
access control lists that instruct a server whether to grant or deny access control lists that instruct a server whether to grant or deny
operations upon a resource (such as HTTP method invocations) by a given operations upon a resource (such as HTTP method invocations) by a given
principal. principal.
This document is a product of the Web Distributed Authoring and This document is a product of the Web Distributed Authoring and
Versioning (WebDAV) working group of the Internet Engineering Task Versioning (WebDAV) working group of the Internet Engineering Task
Force. Comments on this draft are welcomed, and should be addressed to Force. Comments on this draft are welcomed, and should be addressed to
the acl@webdav.org mailing list. Other related documents can be found the acl@webdav.org mailing list. Other related documents can be found at
at http://www.webdav.org/acl/, and http://www.webdav.org/acl/, and http://www.ics.uci.edu/pub/ietf/webdav/.
http://www.ics.uci.edu/pub/ietf/webdav/.
Clemm, Hopkins, Sedlar, Whitehead [Page 1] Clemm, Hopkins, Sedlar, Whitehead [Page 1]
Table of Contents Table of Contents
1 INTRODUCTION......................................................3 1 INTRODUCTION......................................................4
1.1 Terms..........................................................4 1.1 Terms...........................................................5
1.2 Notational Conventions.........................................5 1.2 Notational Conventions..........................................6
2 PRINCIPALS........................................................5 2 PRINCIPALS........................................................6
3 PRIVILEGES........................................................5 3 PRIVILEGES........................................................6
3.1 DAV:read Privilege.............................................6 3.1 DAV:read Privilege..............................................7
3.2 DAV:write Privilege............................................6 3.2 DAV:write Privilege.............................................7
3.3 DAV:read-acl Privilege.........................................7 3.3 DAV:read-acl Privilege..........................................8
3.4 DAV:write-acl Privilege........................................7 3.4 DAV:read-cuprivset Privilege....................................8
3.5 DAV:all Privilege..............................................7 3.5 DAV:write-acl Privilege.........................................8
3.6 DAV:all Privilege...............................................8
4 PRINCIPAL PROPERTIES..............................................7 4 PRINCIPAL PROPERTIES..............................................8
4.1 DAV:is-principal...............................................7 4.1 DAV:is-principal................................................9
4.2 DAV:authentication-id..........................................7 4.2 DAV:alternate-URL...............................................9
5 ACCESS CONTROL PROPERTIES.........................................8 5 ACCESS CONTROL PROPERTIES.........................................9
5.1 DAV:owner......................................................8 5.1 DAV:owner.......................................................9
5.2 DAV:supported-privilege-set....................................8 5.2 DAV:supported-privilege-set....................................10
5.3 DAV:current-user-privilege-set.................................9 5.3 DAV:current-user-privilege-set.................................11
5.4 DAV:acl........................................................9 5.4 DAV:acl........................................................11
5.4.1 ACE Principal................................................9 5.4.1 ACE Principal...............................................11
5.4.2 ACE Grant and Deny..........................................10 5.4.2 ACE Grant and Deny..........................................13
5.4.3 ACE Protection..............................................11 5.4.3 ACE Protection..............................................13
5.4.4 ACE Inheritance.............................................11 5.4.4 ACE Inheritance.............................................13
5.5 DAV:acl-semantics.............................................11 5.5 DAV:acl-semantics..............................................13
5.6 DAV:principal-collection-set..................................11 5.6 DAV:principal-collection-set...................................14
5.7 Example: PROPFIND to retrieve access control properties.......12 5.7 Example: PROPFIND to retrieve access control properties........14
6 ACL SEMANTICS....................................................15 6 ACL SEMANTICS....................................................17
6.1 ACE Combination...............................................15 6.1 ACE Combination................................................17
6.1.1 DAV:first-match ACE Combination.............................15 6.1.1 DAV:first-match ACE Combination.............................18
6.1.2 DAV:all-grant-before-any-deny ACE Combination...............15 6.1.2 DAV:all-grant-before-any-deny ACE Combination...............18
6.1.3 DAV:no-deny ACE Combination.................................15 6.1.3 DAV:specific-deny-overrides-grant ACE Combination...........18
6.2 ACE Ordering..................................................16 6.2 ACE Ordering...................................................18
6.2.1 DAV:deny-before-grant ACE Ordering..........................16 6.2.1 DAV:deny-before-grant ACE Ordering..........................18
6.3 Required Principals...........................................16 6.3 Required Principals............................................18
7 ACCESS CONTROL AND EXISTING METHODS..............................16 7 ACCESS CONTROL AND EXISTING METHODS..............................19
7.1 OPTIONS.......................................................16 7.1 OPTIONS........................................................19
7.1.1 Example - OPTIONS...........................................16 7.1.1 Example - OPTIONS...........................................19
8 ACCESS CONTROL METHODS...........................................17 8 ACCESS CONTROL METHODS...........................................19
8.1 ACL...........................................................17 8.1 ACL............................................................19
8.1.1 ACL Preconditions...........................................17 8.1.1 ACL Preconditions...........................................20
8.1.2 Example: the ACL method.....................................17 8.1.2 Example: the ACL method.....................................20
8.1.3 Example: ACL method failure due to omission of protected ACE18 8.1.3 Example: ACL method failure due to omission of protected ACE21
8.1.4 Example: ACL method failure due to inherited ACEs preceding 8.1.4 Example: ACL method failure due to inherited ACEs preceding
non-inherited ACEs................................................19 non-inherited ACEs................................................22
8.1.5 Example: ACL method failure due to an attempt to set grant and
deny in a single ACE..............................................20
Clemm, Hopkins, Sedlar, Whitehead [Page 2] Clemm, Hopkins, Sedlar, Whitehead [Page 2]
9 INTERNATIONALIZATION CONSIDERATIONS..............................21 8.1.5 Example: ACL method failure due to an attempt to set grant and
deny in a single ACE..............................................23
10 SECURITY CONSIDERATIONS........................................22 9 INTERNATIONALIZATION CONSIDERATIONS..............................24
10.1 Increased Risk of Compromised Users...........................22
10.2 Authentication-id Property and Dictionary Attacks.............22
10.3 Risks of the read-acl Privilege...............................23
11 AUTHENTICATION.................................................23 10 SECURITY CONSIDERATIONS........................................25
10.1 Increased Risk of Compromised Users...........................25
10.2 Risks of the read-acl and cuprivset Privileges................25
12 IANA CONSIDERATIONS............................................23 11 AUTHENTICATION.................................................26
13 INTELLECTUAL PROPERTY..........................................23 12 IANA CONSIDERATIONS............................................26
14 ACKNOWLEDGEMENTS...............................................24 13 INTELLECTUAL PROPERTY..........................................26
15 REFERENCES.....................................................24 14 ACKNOWLEDGEMENTS...............................................26
15.1 Normative References..........................................24
15.2 Informational References......................................25
16 AUTHORS' ADDRESSES.............................................25 15 REFERENCES.....................................................27
15.1 Normative References..........................................27
15.2 Informational References......................................28
17 APPENDICIES....................................................25 16 AUTHORS' ADDRESSES.............................................28
17.1 XML Document Type Definition..................................25
17 APPENDICIES....................................................28
17.1 XML Document Type Definition..................................28
Clemm, Hopkins, Sedlar, Whitehead [Page 3]
1 INTRODUCTION 1 INTRODUCTION
The goal of the WebDAV access control extensions is to provide an The goal of the WebDAV access control extensions is to provide an
interoperable mechanism for handling discretionary access control interoperable mechanism for handling discretionary access control
for content in WebDAV servers. WebDAV access control can be for content in WebDAV servers. WebDAV access control can be
implemented on content repositories with security as simple as that implemented on content repositories with security as simple as that
of a UNIX file system, as well as more sophisticated models. The of a UNIX file system, as well as more sophisticated models. The
underlying principle of access control is that who you are underlying principle of access control is that who you are
determines how you can access a resource. The "who you are" is determines how you can access a resource. The "who you are" is
defined by a "principal" identifier; users, client software, defined by a "principal" identifier; users, client software,
servers, and groups of the previous have principal identifiers. The servers, and groups of the previous have principal identifiers. The
"how" is determined by a single "access control list" (ACL) "how" is determined by a single "access control list" (ACL)
associated with a resource. An ACL contains a set of "access associated with a resource. An ACL contains a set of "access
control entries" (ACEs), where each ACE specifies a principal and a control entries" (ACEs), where each ACE specifies a principal and a
set of privileges that are either granted or denied to that set of privileges that are either granted or denied to that
principal. When a principal submits an operation (such as an HTTP or principal. When a principal submits an operation (such as an HTTP
WebDAV method) to a resource for execution, the server evaluates the or WebDAV method) to a resource for execution, the server evaluates
ACEs in the ACL to determine if the principal has permission for the ACEs in the ACL to determine if the principal has permission
that operation. for that operation.
This specification intentionally omits discussion of authentication, This specification intentionally omits discussion of
as the HTTP protocol already has a number of authentication authentication, as the HTTP protocol already has a number of
mechanisms [RFC2617]. Some authentication mechanism (such as HTTP authentication mechanisms [RFC2617]. Some authentication mechanism
Digest Authentication, which all WebDAV compliant implementations (such as HTTP Digest Authentication, which all WebDAV compliant
are required to support) must be available to validate the identity implementations are required to support) must be available to
of a principal. validate the identity of a principal.
In the interests of timeliness, the following set of security In the interests of timeliness, the following set of security
mechanisms are not addressed by this document: mechanisms are not addressed by this document:
Clemm, Hopkins, Sedlar, Whitehead [Page 3] * Access control that applies only to a particular property on a
* Access control that applies only to a particular property on resource (excepting the access control properties DAV:acl and
a resource, rather than the entire resource, DAV:current-user-privilege-set), rather than the entire
resource,
* Role-based security (where a role can be seen as a * Role-based security (where a role can be seen as a dynamically
dynamically defined collection of principals), defined collection of principals),
* Specification of the ways an ACL on a resource is * Specification of the ways an ACL on a resource is initialized,
initialized,
* Specification of an ACL that applies globally to a method, * Specification of an ACL that applies globally to a method,
rather than to a particular resource. rather than to a particular resource.
This specification is organized as follows. Section 1.1 defines key This specification is organized as follows. Section 1.1 defines key
concepts used throughout the specification, and is followed by more concepts used throughout the specification, and is followed by more
in-depth discussion of principals (Section 2), and privileges in-depth discussion of principals (Section 2), and privileges
(Section 3). Properties defined on principals are specified in (Section 3). Properties defined on principals are specified in
Section 4, and access control properties for content resources are Section 4, and access control properties for content resources are
specified in Section 5. The semantics of access control lists are specified in Section 5. The semantics of access control lists are
described in Section 6, including sections on ACE combination described in Section 6, including sections on ACE combination
(Section 6.1), ACE ordering (Section 6.2), and principals required (Section 6.1), ACE ordering (Section 6.2), and principals required
to be present in an ACE (Section 6.3). Client discovery of access to be present in an ACE (Section 6.3). Client discovery of access
control capability using OPTIONS is described in Section 7.1, and control capability using OPTIONS is described in Section 7.1, and
the access control setting method, ACL, is specified in Section 8. the access control setting method, ACL, is specified in Section 8.
Clemm, Hopkins, Sedlar, Whitehead [Page 4]
Internationalization considerations (Section 9) and security Internationalization considerations (Section 9) and security
considerations (Section 10) round out the specification. An appendix considerations (Section 10) round out the specification. An
(Section 17.1) provides an XML Document Type Definition (DTD) for appendix (Section 17.1) provides an XML Document Type Definition
the XML elements defined in the specification. (DTD) for the XML elements defined in the specification.
1.1 Terms 1.1 Terms
This draft uses the terms defined in HTTP [RFC2616] and WebDAV This draft uses the terms defined in HTTP [RFC2616] and WebDAV
[RFC2518]. In addition, the following terms are defined: [RFC2518]. In addition, the following terms are defined:
principal principal
A "principal" is a distinct human or computational actor that A "principal" is a distinct human or computational actor that
initiates access to network resources. In this protocol, a initiates access to network resources. In this protocol, a
principal is an HTTP resource that represents such an actor. principal is an HTTP resource that represents such an actor.
principal collection principal collection
A "principal collection" is a group of principals, and is A "principal collection" is a group of principals, and is
represented in this protocol by a WebDAV collection containing HTTP represented in this protocol by a WebDAV collection containing HTTP
resources that represent principals, and principal collections. resources that represent principals, and principal collections.
privilege privilege
A "privilege" controls access to a particular set of HTTP operations A "privilege" controls access to a particular set of HTTP
on a resource. operations on a resource.
aggregate privilege aggregate privilege
An "aggregate privilege" is a privilege that contains a set of other An "aggregate privilege" is a privilege that contains a set of
privileges. other privileges.
abstract privilege abstract privilege
Clemm, Hopkins, Sedlar, Whitehead [Page 4]
The modifier "abstract", when applied to an atomic or aggregate The modifier "abstract", when applied to an atomic or aggregate
privilege, means the privilege cannot be set in an access control privilege, means the privilege cannot be set in an access control
element (ace). element (ace).
access control list (acl) access control list (acl)
An "acl" is a list of access control elements that define access An "acl" is a list of access control elements that define access
control to a particular resource. control to a particular resource.
access control element (ace) access control element (ace)
An "ace" either grants or denies a particular set of (non-abstract) An "ace" either grants or denies a particular set of (non-abstract)
privileges for a particular principal. privileges for a particular principal.
inherited ace inherited ace
An "inherited ace" is an ace that is shared from the acl of another An "inherited ace" is an ace that is shared from the acl of another
resource. resource.
Clemm, Hopkins, Sedlar, Whitehead [Page 5]
1.2 Notational Conventions 1.2 Notational Conventions
The augmented BNF used by this document to describe protocol The augmented BNF used by this document to describe protocol
elements is described in Section 2.1 of [RFC2616]. Because this elements is described in Section 2.1 of [RFC2616]. Because this
augmented BNF uses the basic production rules provided in Section augmented BNF uses the basic production rules provided in Section
2.2 of [RFC2616], those rules apply to this document as well. 2.2 of [RFC2616], those rules apply to this document as well.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
document are to be interpreted as described in [RFC2119]. this document are to be interpreted as described in [RFC2119].
2 PRINCIPALS 2 PRINCIPALS
A principal is an HTTP resource that represents a distinct human or A principal is a network resource that represents a distinct human
computational actor that initiates access to network resources. On or computational actor that initiates access to network resources.
many implementations, users and groups are represented as On many implementations, users and groups are represented as
principals; other types of principals are also possible. Although principals; other types of principals are also possible. A URL of
an implementation MAY support PROPFIND and PROPPATCH to access and any scheme MAY be used to identify a principal resource. However,
modify information about a principal, it is not required to do so. servers implementing this specification SHOULD 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. Although an implementation SHOULD support PROPFIND
and 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. A collection A principal resource may or may not be a collection. A collection
principal may only contain other principals (not other types of principal may only contain other principals (not other types of
resources). Servers that support aggregation of principals (e.g. resources). Servers that support aggregation of principals (e.g.
groups of users or other groups) MUST manifest them as collection groups of users or other groups) MUST manifest them as collection
principals. The WebDAV methods for examining and maintaining principals. The WebDAV methods for examining and maintaining
collections (e.g. DELETE, PROPFIND) MAY be used to maintain collections (e.g. DELETE, PROPFIND) MAY be used to maintain
collection principals. Membership in a collection principal is collection principals. Membership in a collection principal is
recursive, so a principal in a collection principal GRPA contained recursive, so a principal in a collection principal GRPA contained
by collection principal GRPB is a member of both GRPA and GRPB. by collection principal GRPB is a member of both GRPA and GRPB.
Implementations not supporting recursive membership in principal Implementations not supporting recursive membership in principal
collections can return an error if the client attempts to bind collections can return an error if the client attempts to bind
collection principals into other collection principals. collection principals into other collection principals.
3 PRIVILEGES 3 PRIVILEGES
Ability to perform a given method on a resource SHOULD be controlled Ability to perform a given method on a resource SHOULD be
by one or more privileges. Authors of protocol extensions that controlled by one or more privileges. Authors of protocol
extensions that define new HTTP methods SHOULD specify which
Clemm, Hopkins, Sedlar, Whitehead [Page 5] privileges (by defining new privileges, or mapping to ones below)
define new HTTP methods SHOULD specify which privileges (by defining are required to perform the method. A principal with no privileges
new privileges, or mapping to ones below) are required to perform to a resource SHOULD be denied any HTTP access to that resource.
the method. A principal with no privileges to a resource SHOULD be
denied any HTTP access to that resource.
Privileges may be containers of other privileges, in which case they Privileges may be containers of other privileges, in which case
are termed aggregate privileges. If a principal is granted or they are termed aggregate privileges. If a principal is granted or
denied an aggregate privilege, it is semantically equivalent to denied an aggregate privilege, it is semantically equivalent to
granting or denying each of the aggregated privileges individually. granting or denying each of the aggregated privileges individually.
For example, an implementation may define add-member and remove- For example, an implementation may define add-member and remove-
member privileges that control the ability to add and remove an member privileges that control the ability to add and remove an
internal member of a collection. Since these privileges control the internal member of a collection. Since these privileges control
ability to update the state of a collection, these privileges would
be aggregated by the DAV:write privilege on a collection, and Clemm, Hopkins, Sedlar, Whitehead [Page 6]
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 granting the DAV:write privilege on a collection would also grant
the add-member and remove-member privileges. the add-member and remove-member privileges.
Privileges may have the quality of being abstract, in which case Privileges may have the quality of being abstract, in which case
they cannot be set in an ACE. Aggregate and atomic privileges are they cannot be set in an ACE. Aggregate and atomic privileges are
both capable of being abstract. Abstract privileges are useful for both capable of being abstract. Abstract privileges are useful for
modeling privileges that otherwise would not be exposed via the modeling privileges that otherwise would not be exposed via the
protocol. Abstract privileges also provide server implementations protocol. Abstract privileges also provide server implementations
with flexibility in implementing the privileges defined in this with flexibility in implementing the privileges defined in this
specification. For example, if a server is incapable of separating specification. For example, if a server is incapable of separating
the read resource capability from the read ACL capability, it can the read resource capability from the read ACL capability, it can
still model the DAV:read and DAV:read-acl privileges defined in this still model the DAV:read and DAV:read-acl privileges defined in
specification by declaring them abstract, and containing them within this specification by declaring them abstract, and containing them
a non-abstract aggregate privilege (say, read-all) that holds within a non-abstract aggregate privilege (say, read-all) that
DAV:read, and DAV:read-acl. In this way, it is possible to set the holds DAV:read, and DAV:read-acl. In this way, it is possible to
aggregate privilege, read-all, thus coupling the setting of DAV:read set the aggregate privilege, read-all, thus coupling the setting of
and DAV:read-acl, but it is not possible to set DAV:read, or DAV:read and DAV:read-acl, but it is not possible to set DAV:read,
DAV:read-acl individually. Since aggregate privileges can be or DAV:read-acl individually. Since aggregate privileges can be
abstract, it is also possible to use abstract privileges to group abstract, it is also possible to use abstract privileges to group
and classify non-abstract privileges. and classify non-abstract privileges.
The set of privileges that apply to a particular resource may vary The set of privileges that apply to a particular resource may vary
with the DAV:resourcetype of the resource, as well as between with the DAV:resourcetype of the resource, as well as between
different server implementations. To promote interoperability, different server implementations. To promote interoperability,
however, WebDAV defines a set of well-known privileges (e.g. however, WebDAV defines a set of well-known privileges (e.g.
DAV:read and DAV:write), which can at least be used to classify the DAV:read and DAV:write), which can at least be used to classify the
other privileges defined on a particular resource. other privileges defined on a particular resource. The access
permissions on null and lock-null resources are solely those they
inherit (if any), and they are not discoverable (i.e., the ACL
properties specified in Section 5 are not defined on null and lock-
null resources). On the transition from null or lock-null to a
stateful resource, the initial access control list is set by the
server's default ACL value policy (if any).
3.1 DAV:read Privilege 3.1 DAV:read Privilege
The read privilege controls methods that return information about The read privilege controls methods that return information about
the state of the resource, including the resource's properties. the state of the resource, including the resource's properties.
Affected methods include GET and PROPFIND. Additionally, the read Affected methods include GET and PROPFIND. Additionally, the read
privilege MAY control the OPTIONS method. privilege MAY control the OPTIONS method.
<!ELEMENT read EMPTY> <!ELEMENT read EMPTY>
3.2 DAV:write Privilege 3.2 DAV:write Privilege
The write privilege controls methods that modify the state of the The write privilege controls methods that modify the state of the
resource, such as PUT and PROPPATCH. Note that state modification resource, such as PUT and PROPPATCH. Note that state modification
Clemm, Hopkins, Sedlar, Whitehead [Page 6]
is also controlled via locking (see section 5.3 of [WEBDAV]), so is also controlled via locking (see section 5.3 of [WEBDAV]), so
effective write access requires that both write privileges and write effective write access requires that both write privileges and
locking requirements are satisfied. write locking requirements are satisfied.
<!ELEMENT write EMPTY> <!ELEMENT write EMPTY>
Clemm, Hopkins, Sedlar, Whitehead [Page 7]
3.3 DAV:read-acl Privilege 3.3 DAV:read-acl Privilege
The DAV:read-acl privilege controls the use of PROPFIND to retrieve The DAV:read-acl privilege controls the use of PROPFIND to retrieve
the DAV:acl, and DAV:current-user-privilege-set properties of the the DAV:acl property of the resource.
resource.
<!ELEMENT read-acl EMPTY> <!ELEMENT read-acl EMPTY>
3.4 DAV:write-acl Privilege 3.4 DAV:read-cuprivset Privilege
The DAV:write-acl privilege controls use of the ACL method to modify The DAV:read-cuprivset privilege controls the use of PROPFIND to
the DAV:acl property of the resource. retrieve the DAV:current-user-privilege-set property of the
resource.
Clients are intended to use this property to visually indicate in
their UI items that are dependent on the permissions of a resource,
for example, by graying out resources that are not writeable.
This privilege is separate from DAV:read-acl because there is a
need to allow most users access to the privileges permitted the
current user (due to its use in creating the UI), while the full
ACL contains information that may not be appropriate for the
current authenticated user. As a result, the set of users who can
view the full ACL is expected to be much smaller than those who can
read the current user privilege set, and hence distinct privileges
are needed for each
<!ELEMENT read-cuprivset EMPTY>
3.5 DAV:write-acl Privilege
The DAV:write-acl privilege controls use of the ACL method to
modify the DAV:acl property of the resource.
<!ELEMENT write-acl EMPTY> <!ELEMENT write-acl EMPTY>
3.5 DAV:all Privilege 3.6 DAV:all Privilege
DAV:all is an aggregate privilege that contains all privileges on DAV:all is an aggregate privilege that contains all privileges on
the resource. the resource.
<!ELEMENT all EMPTY> <!ELEMENT all EMPTY>
4 PRINCIPAL PROPERTIES 4 PRINCIPAL PROPERTIES
Principals are manifested to clients as an HTTP resource, identified Principals are manifested to clients as an HTTP resource,
by a URL. A principal MUST have a DAV:displayname property. This identified by a URL. A principal MUST have a DAV:displayname
protocol defines the following additional properties for a property. This protocol defines the following additional
principal. properties for a principal. The name and value of these properties
SHOULD NOT be returned by PROPFIND allprop request (as defined in
Section 12.14.1 of [RFC2518]). In the descriptions below, a read-
only property is defined as a property that MUST NOT be writeable
using PROPPATCH.
Clemm, Hopkins, Sedlar, Whitehead [Page 8]
4.1 DAV:is-principal 4.1 DAV:is-principal
This property indicates whether this resource is a principal. A This is a read-only property that indicates whether this resource
resource MUST have a non-empty DAV:is-principal property if and only is a principal. A resource MUST have a non-empty DAV:is-principal
if it is a principal resource. (Note: If we can just add a property if and only if it is a principal resource.
DAV:principal element to the DAV:resourcetype property, then we do
not need a DAV:is-principal property.)
<!ELEMENT is-principal (#PCDATA)> <!ELEMENT is-principal (#PCDATA)>
PCDATA value: any non-empty value ("T" is suggested) PCDATA value: "true" - resource is a principal, "false" - resource
is not a principal (note that in cases where the "F" value might be
used, this specification requires the property not be present at
all).
4.2 DAV:authentication-id 4.2 DAV:alternate-URL
A property containing the name used to authenticate this principal This read-only property, if present, contains the URL of a network
(typically typed into a login prompt/dialog). resource with additional descriptive information about the
principal. This property identifies one or more additional network
resources (i.e., it contains one or more URLs) that may be
consulted by a client to gain additional knowledge concerning a
principal. Two potential uses for this property are to store an
ldap [RFC2255] or mailto [RFC2368] scheme URL. Support for this
property is OPTIONAL.
<!ELEMENT authentication-id (#PCDATA)> <!ELEMENT alternate-URL (href*)>
PCDATA value: any string
Clemm, Hopkins, Sedlar, Whitehead [Page 7]
5 ACCESS CONTROL PROPERTIES 5 ACCESS CONTROL PROPERTIES
This specification defines a number of new properties for WebDAV This specification defines a number of new properties for WebDAV
resources. Access control properties may be retrieved just like resources. Access control properties may be retrieved just like
other WebDAV properties, using the PROPFIND method. Some access other WebDAV properties, using the PROPFIND method. Some access
control properties (such as DAV:owner) MAY be updated with the control properties (such as DAV:owner) MAY be updated with the
PROPPATCH method. PROPPATCH method. In the descriptions below, a read-only property
is defined as a property that MUST NOT be writeable using
PROPPATCH. 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 HTTP resources that support the WebDAV Access Control Protocol MUST
contain the following properties: contain the following properties. Null, and lock-null resources
(described in Section 7.4 of [RFC2518]) MUST NOT contain the
following properties:
5.1 DAV:owner 5.1 DAV:owner
This property identifies a particular principal as being the "owner" This property identifies a particular principal as being the
of the resource. "owner" of the resource. Since the owner of a resource often has
special access control capabilities (e.g., the owner frequently has
permanent write-ACL privilege), clients might display the resource
owner in their user interface.
<!ELEMENT owner (href prop?)> <!ELEMENT owner (href prop?)>
<!ELEMENT prop (see [RFC2518], section 12.11)> <!ELEMENT prop (see [RFC2518], section 12.11)>
Clemm, Hopkins, Sedlar, Whitehead [Page 9]
An implementation MAY include a list of selected properties of that An implementation MAY include a list of selected properties of that
principal resource. Which properties (if any) are included is principal resource. Which properties (if any) are included is
implementation defined. An implementation MAY allow the use of implementation defined, but might reasonably include properties
PROPPATCH to update the DAV:owner field. such as DAV:displayname, which is useful for the construction of
access control user interfaces on the client. A server might
support this capability if it wished to save the client the
additional network round-trip delay required to retrieve this
information using a PROPFIND request on the principal URL in the
href element. Servers that do not directly support PROPFIND on
principal resources might also support this feature, since it
allows them to return a server-controlled subset of the properties
on the principal resource.
An implementation MAY allow the use of PROPPATCH to update the
DAV:owner field. If the DAV:owner property is writeable, clients
MUST NOT submit the prop element; only the href element can be
modified by the client. The purpose of this restriction is to limit
the scope of effect of a PROPPATCH to just the owner property's
resource; setting the prop element would additionally require
modification to properties of the principal resource identified by
the href element.
5.2 DAV:supported-privilege-set 5.2 DAV:supported-privilege-set
This is a read-only property that identifies the privileges defined This is a read-only property that identifies the privileges defined
for the resource. for the resource.
<!ELEMENT supported-privilege-set (supported-privilege*)> <!ELEMENT supported-privilege-set (supported-privilege*)>
Each privilege appears as an XML element, where aggregate privileges Each privilege appears as an XML element, where aggregate
list as sub-elements all of the privileges that they aggregate. privileges list as sub-elements all of the privileges that they
aggregate.
<!ELEMENT supported-privilege <!ELEMENT supported-privilege
(privilege, abstract?, description, supported-privilege*)> (privilege, abstract?, description, supported-privilege*)>
<!ELEMENT privilege ANY> <!ELEMENT privilege ANY>
An abstract privilege of a resource MUST NOT be used in an ACE for An abstract privilege of a resource MUST NOT be used in an ACE for
that resource. Servers MUST fail an attempt to set an abstract that resource. Servers MUST fail an attempt to set an abstract
privilege. privilege.
<!ELEMENT abstract EMPTY> <!ELEMENT abstract EMPTY>
A description is a human-readable description of what this privilege A description is a human-readable description of what this
controls access to. privilege controls access to.
<!ELEMENT description #PCDATA> <!ELEMENT description #PCDATA>
It is envisioned that a WebDAV ACL-aware administrative client would It is envisioned that a WebDAV ACL-aware administrative client
list the supported privileges in a dialog box, and allow the user to would list the supported privileges in a dialog box, and allow the
choose non-abstract privileges to apply in an ACE. The privileges user to choose non-abstract privileges to apply in an ACE. The
tree is useful programmatically to map well-known privileges privileges tree is useful programmatically to map well-known
(defined by WebDAV or other standards groups) into privileges that privileges (defined by WebDAV or other standards groups) into
are supported by any particular server implementation. The
Clemm, Hopkins, Sedlar, Whitehead [Page 8] Clemm, Hopkins, Sedlar, Whitehead [Page 10]
privilege tree also serves to hide complexity in implementations privileges that are supported by any particular server
allowing large number of privileges to be defined by displaying implementation. The privilege tree also serves to hide complexity
aggregates to the user. in implementations allowing large number of privileges to be
defined by displaying aggregates to the user.
5.3 DAV:current-user-privilege-set 5.3 DAV:current-user-privilege-set
DAV:current-user-privilege-set is a read-only property containing DAV:current-user-privilege-set is a read-only property containing
the exact set of privileges (as computed by the server) granted to the exact set of privileges (as computed by the server) granted to
the currently authenticated HTTP user. A user-agent can use the 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 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 inaccessible (e.g., by graying out a menu item or button) for which
the current principal does not have permission. This is particularly the current principal does not have permission. This is
useful for an access control user interface, which can be particularly useful for an access control user interface, which can
constructed without knowing the ACE combining semantics of the be constructed without knowing the ACE combining semantics of the
server. This property is also useful for determine what operations server. This property is also useful for determining what
can be performed by the current principal, without having to operations the current principal can perform, without having to
actually execute an operation. actually execute an operation.
<!ELEMENT current-user-privilege-set (privilege*)> <!ELEMENT current-user-privilege-set (privilege*)>
<!ELEMENT privilege ANY> <!ELEMENT privilege ANY>
If the current user is granted a specific privilege, that privilege If the current user is granted a specific privilege, that privilege
must belong to the set of privileges that may be set on this must belong to the set of privileges that may be set on this
resource. Therefore, each element in the DAV:current-user-privilege- resource. Therefore, each element in the DAV:current-user-
set property MUST identify a privilege from the DAV:supported- privilege-set property MUST identify a non-abstract privilege from
privilege-set property. the DAV:supported-privilege-set property.
5.4 DAV:acl 5.4 DAV:acl
This property specifies the list of access control entries (ACEs), This is a read-only property that specifies the list of access
which define what principals are to get what privileges for this control entries (ACEs), which define what principals are to get
resource. what privileges for this resource.
<!ELEMENT acl (ace*)> <!ELEMENT acl (ace*)>
Each DAV:ace element specifies the set of privileges to be either 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 granted or denied to a single principal. If the DAV:acl property
empty, no principal is granted any privilege. is empty, no principal is granted any privilege.
<!ELEMENT ace (principal, (grant|deny), protected?, inherited?)> <!ELEMENT ace (principal, (grant|deny), protected?, inherited?)>
An attempt to update the DAV:acl property with a PROPPATCH MUST
fail.
5.4.1 ACE Principal 5.4.1 ACE Principal
The DAV:principal element identifies the principal to which this ACE The DAV:principal element identifies the principal to which this
applies. ACE applies.
<!ELEMENT principal ((href, prop?) <!ELEMENT principal ((href, prop?)
| all | authenticated | unauthenticated | all | authenticated | unauthenticated
| property | self)> | property | self)>
The current user matches DAV:href only if that user is authenticated Clemm, Hopkins, Sedlar, Whitehead [Page 11]
as being (or being a member of) the principal identified by the URL The current user matches DAV:href only if that user is
authenticated as being (or being a member of) the principal
Clemm, Hopkins, Sedlar, Whitehead [Page 9] identified by the URL contained by that DAV:href. An implementation
contained by that DAV:href. An implementation MAY include a MAY include a DAV:prop element after the DAV:href element,
DAV:prop element after the DAV:href element, containing a list of containing a list of selected properties of that principal
selected properties of that principal resource. Which properties resource. Which properties (if any) are included in the DAV:prop
(if any) are included in the DAV:prop element is implementation element is implementation defined. The DAV:prop element can be used
defined. The DAV:prop element is primarily intended for by servers that do not support PROPFIND requests on principal
implementations that do not support PROPFIND requests on the resources to return principal-related information (such as the
principal URL. value of the DAV:displayname property) that a client would find
useful in the creation of an access control user interface. A
server might also support this capability if it wished to save the
client the additional network round-trip delays required to
retrieve this information via a series of PROPFIND requests on each
principal URL in the ACL. In the worst case, this is one additional
PROPFIND per ACE.
<!ELEMENT prop (see [RFC2518], section 12.11)> <!ELEMENT prop (see [RFC2518], section 12.11)>
The current user always matches DAV:all. The current user always matches DAV:all.
<!ELEMENT all EMPTY> <!ELEMENT all EMPTY>
The current user matches DAV:authenticated only if authenticated. The current user matches DAV:authenticated only if authenticated.
<!ELEMENT authenticated EMPTY> <!ELEMENT authenticated EMPTY>
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resource contains a DAV:href that identifies a principal, and the resource contains a DAV:href that identifies a principal, and the
current user is authenticated as being (or being a member of) that current user is authenticated as being (or being a member of) that
principal. For example, if the DAV:property element contained principal. For example, if the DAV:property element contained
<DAV:owner/>, the current user would match the DAV:property <DAV:owner/>, the current user would match the DAV:property
principal only if the current user is authenticated as matching the principal only if the current user is authenticated as matching the
principal identified by the DAV:owner property of the resource. principal identified by the DAV:owner property of the resource.
<!ELEMENT property ANY> <!ELEMENT property ANY>
The current user matches DAV:self in a DAV:acl property of the 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 resource only if that resource is a principal object and the
user is authenticated as being that principal. current user is authenticated as being that principal.
<!ELEMENT self EMPTY> <!ELEMENT self EMPTY>
Clemm, Hopkins, Sedlar, Whitehead [Page 12]
5.4.2 ACE Grant and Deny 5.4.2 ACE Grant and Deny
Each DAV:grant or DAV:deny element specifies the set of privileges Each DAV:grant or DAV:deny element specifies the set of privileges
to be either granted or denied to the specified principal. A 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 DAV:grant or DAV:deny element of the DAV:acl of a resource MUST
contain elements specified in the DAV:supported-privilege-set of only contain non-abstract elements specified in the DAV:supported-
that resource. privilege-set of that resource.
<!ELEMENT grant (privilege+)> <!ELEMENT grant (privilege+)>
<!ELEMENT deny (privilege+)> <!ELEMENT deny (privilege+)>
<!ELEMENT privilege ANY> <!ELEMENT privilege ANY>
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5.4.3 ACE Protection 5.4.3 ACE Protection
If an ACE contains a DAV:protected element, an ACL request without If an ACE contains a DAV:protected element, an ACL request without
that ACE MUST fail. that ACE MUST fail.
<!ELEMENT protected EMPTY> <!ELEMENT protected EMPTY>
5.4.4 ACE Inheritance 5.4.4 ACE Inheritance
The presence of a DAV:inherited element indicates that this ACE is The presence of a DAV:inherited element indicates that this ACE is
inherited from another resource that is identified by the URL inherited from another resource that is identified by the URL
contained in a DAV:href element. An inherited ACE cannot be contained in a DAV:href element. An inherited ACE cannot be
modified directly, but instead the ACL on the resource from which it modified directly, but instead the ACL on the resource from which
is inherited must be modified. it is inherited must be modified.
Note that ACE inheritance is not the same as ACL initialization. Note that ACE inheritance is not the same as ACL initialization.
ACL initialization defines the ACL that a newly created resource ACL initialization defines the ACL that a newly created resource
will use (if not specified). ACE inheritance refers to an ACE that will use (if not specified). ACE inheritance refers to an ACE that
is logically shared - where an update to the resource containing an is logically shared - where an update to the resource containing an
ACE will affect the ACE of each resource that inherits that ACE. ACE will affect the ACE of each resource that inherits that ACE.
The method by which ACLs are initialized or by which ACEs are The method by which ACLs are initialized or by which ACEs are
inherited is not defined by this document. inherited is not defined by this document.
<!ELEMENT inherited (href)> <!ELEMENT inherited (href)>
5.5 DAV:acl-semantics 5.5 DAV:acl-semantics
This is a read-only property that defines the ACL semantics. These This is a read-only property that defines the ACL semantics. These
semantics define how multiple ACEs that match the current user are semantics define how multiple ACEs that match the current user are
combined, what are the constraints on how ACEs can be ordered, and combined, what are the constraints on how ACEs can be ordered, and
which principals must have an ACE. 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 could use this property to determine exactly,
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 Since it is not practical to require all implementations to use the
same ACL semantics, the DAV:acl-semantics property is used to same ACL semantics, the DAV:acl-semantics property is used to
identify the ACL semantics for a particular resource. The DAV:acl- identify the ACL semantics for a particular resource. The DAV:acl-
semantics element is defined in section 6. semantics element is defined in section 6.
Clemm, Hopkins, Sedlar, Whitehead [Page 13]
5.6 DAV:principal-collection-set 5.6 DAV:principal-collection-set
This read-only property contains zero, one, or more URLs that This read-only property contains zero, one, or more URLs that
identify a collection principal. It is expected that implementations identify a collection principal. It is expected that
of this protocol will typically employ a relatively small number of implementations of this protocol will typically employ a relatively
locations in the URL namespace for principal, and collection small number of locations in the URL namespace for principal, and
principals. In cases where this assumption holds, the DAV:principal- collection principals. In cases where this assumption holds, the
collection-set property will contain a small set of URLs identifying DAV:principal-collection-set property will contain a small set of
the top of collection hierarchy containing multiple principals and URLs identifying the top of collection hierarchy containing
collection principals. An access control protocol user agent could multiple principals and collection principals. An access control
use the contents of DAV:principal-collection-set to, for example, protocol user agent could use the contents of DAV:principal-
query the DAV:displayname property (specified in Section 13.2 of collection-set to query the DAV:displayname property (specified in
[RFC2518]) of all principals on that server, thereby yielding human- Section 13.2 of [RFC2518]) of all principals on that server,
readable names for each principal that could be displayed in a user thereby yielding human-readable names for each principal that could
interface. be displayed in a user interface.
Clemm, Hopkins, Sedlar, Whitehead [Page 11]
<!ELEMENT principal-collection-set (href*)> <!ELEMENT principal-collection-set (href*)>
Since different servers can control different parts of the URL Since different servers can control different parts of the URL
namespace, different resources on the same host MAY have different namespace, different resources on the same host MAY have different
DAV:principal-collection-set values. The collections specified in DAV:principal-collection-set values. The collections specified in
the DAV:principal-collection-set MAY be located on different hosts the DAV:principal-collection-set MAY be located on different hosts
from the resource. The URLs in DAV:principal-collection-set are not from the resource. The URLs in DAV:principal-collection-set SHOULD
limited to http scheme URLs, and can, for example, be ldap scheme be http or https scheme URLs. For security and scalability reasons,
URLs. For security and scalability reasons, a server MAY report only a server MAY report only a subset of the entire set of known
a subset of the entire set of known collection principals, and collection principals, and therefore clients should not assume they
therefore clients should not assume they have retrieved an have retrieved an exhaustive listing. Additionally, a server MAY
exhaustive listing. Additionally, a server MAY elect to report none elect to report none of the collection principals it knows about.
of the collection principals it knows about.
5.7 Example: PROPFIND to retrieve access control properties 5.7 Example: PROPFIND to retrieve access control properties
The following example shows how access control information can be The following example shows how access control information can be
retrieved by using the PROPFIND method to fetch the values of the retrieved by using the PROPFIND method to fetch the values of the
DAV:owner, DAV:supported-privilege-set, DAV:current-user-privilege- DAV:owner, DAV:supported-privilege-set, DAV:current-user-privilege-
set, and DAV:acl properties. set, and DAV:acl properties.
>> Request << >> Request <<
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uri="/top/container/", response="...", opaque="..." uri="/top/container/", response="...", opaque="..."
<?xml version="1.0" encoding="utf-8" ?> <?xml version="1.0" encoding="utf-8" ?>
<D:propfind xmlns:D="DAV:"> <D:propfind xmlns:D="DAV:">
<D:owner/> <D:owner/>
<D:supported-privilege-set/> <D:supported-privilege-set/>
<D:current-user-privilege-set/> <D:current-user-privilege-set/>
<D:acl/> <D:acl/>
</D:propfind> </D:propfind>
Clemm, Hopkins, Sedlar, Whitehead [Page 14]
>> Response << >> Response <<
HTTP/1.1 207 Multi-Status HTTP/1.1 207 Multi-Status
Content-Type: text/xml; charset="utf-8" Content-Type: text/xml; charset="utf-8"
Content-Length: xxx Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?> <?xml version="1.0" encoding="utf-8" ?>
<D:multistatus <D:multistatus
xmlns:D="DAV:" xmlns:D="DAV:"
xmlns:A="http://www.acl.org/"> <D:response> <D:propstat> xmlns:A="http://www.webdav.org/acl/"> <D:response> <D:propstat>
<D:status>HTTP/1.1 200 OK</D:status> <D:status>HTTP/1.1 200 OK</D:status>
<D:prop> <D:prop>
<D:owner> <D:owner>
<D:href>http://www.foo.org/users/gclemm</D:href> </D:owner> <D:href>http://www.foo.org/users/gclemm</D:href> </D:owner>
Clemm, Hopkins, Sedlar, Whitehead [Page 12]
<D:supported-privilege-set> <D:supported-privilege-set>
<D:supported-privilege> <D:supported-privilege>
<D:privilege> <D:all/> </D:privilege> <D:privilege> <D:all/> </D:privilege>
<D:abstract/> <D:abstract/>
<D:description>Any operation</D:description> <D:description>Any operation</D:description>
<D:supported-privilege> <D:supported-privilege>
<D:privilege> <D:read/> </D:privilege> <D:privilege> <D:read/> </D:privilege>
<D:description>Read any object</D:description> <D:description>Read any object</D:description>
</D:supported-privilege> </D:supported-privilege>
<D:supported-privilege> <D:supported-privilege>
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</D:supported-privilege> </D:supported-privilege>
<D:supported-privilege> <D:supported-privilege>
<D:privilege> <D:write-acl/> </D:privilege> <D:privilege> <D:write-acl/> </D:privilege>
<D:description>Write the ACL</D:description> <D:description>Write the ACL</D:description>
</D:supported-privilege> </D:supported-privilege>
</D:supported-privilege> </D:supported-privilege>
</D:supported-privilege-set> </D:supported-privilege-set>
<D:current-user-privilege-set> <D:current-user-privilege-set>
<D:privilege> <D:read/> </D:privilege> <D:privilege> <D:read/> </D:privilege>
<D:privilege> <D:read-acl/> </D:privilege> <D:privilege> <D:read-acl/> </D:privilege>
Clemm, Hopkins, Sedlar, Whitehead [Page 15]
</D:current-user-privilege-set> </D:current-user-privilege-set>
<D:acl> <D:acl>
<D:ace> <D:ace>
<D:principal> <D:principal>
<D:href>http://www.foo.org/users/esedlar</D:href> <D:href>http://www.foo.org/users/esedlar</D:href>
<D:prop> <D:prop>
<D:authentication-id>esedlar</D:authentication-id>
<D:displayname>Eric Sedlar</D:displayname> <D:displayname>Eric Sedlar</D:displayname>
</D:prop> </D:principal> </D:prop> </D:principal>
<D:grant> <D:grant>
<D:privilege> <D:read/> </D:privilege> <D:privilege> <D:read/> </D:privilege>
<D:privilege> <D:write/> </D:privilege> <D:privilege> <D:write/> </D:privilege>
<D:privilege> <D:read-acl/> </D:privilege> </D:grant> <D:privilege> <D:read-acl/> </D:privilege> </D:grant>
</D:ace> </D:ace>
<D:ace> <D:ace>
<D:principal> <D:principal>
Clemm, Hopkins, Sedlar, Whitehead [Page 13]
<D:href>http://www.foo.org/groups/marketing/</D:href> <D:href>http://www.foo.org/groups/marketing/</D:href>
</D:principal> </D:principal>
<D:deny> <D:deny>
<D:privilege> <D:read/> </D:privilege> </D:deny> <D:privilege> <D:read/> </D:privilege> </D:deny>
</D:ace> </D:ace>
<D:ace> <D:ace>
<D:principal> <D:principal>
<D:property> <D:owner/> </D:property> </D:principal> <D:property> <D:owner/> </D:property> </D:principal>
<D:grant> <D:grant>
<D:privilege> <D:read-acl/> </D:privilege> <D:privilege> <D:read-acl/> </D:privilege>
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<D:ace> <D:ace>
<D:principal> <D:all/> </D:principal> <D:principal> <D:all/> </D:principal>
<D:grant> <D:grant>
<D:privilege> <D:read/> </D:privilege> </D:grant> <D:privilege> <D:read/> </D:privilege> </D:grant>
<D:inherited> <D:inherited>
<D:href>http://www.foo.org/top/</D:href> </D:inherited> <D:href>http://www.foo.org/top/</D:href> </D:inherited>
</D:ace> </D:acl> </D:ace> </D:acl>
</D:prop> </D:prop>
</D:propstat> </D:response> </D:multistatus> </D:propstat> </D:response> </D:multistatus>
The value of the DAV:owner property is a single DAV:href XML element The value of the DAV:owner property is a single DAV:href XML
containing the URL of the principal that owns this resource. element containing the URL of the principal that owns this
resource.
The value of the DAV:supported-privilege-set property is a tree of The value of the DAV:supported-privilege-set property is a tree of
supported privileges: supported privileges:
DAV:acl (aggregate, abstract) DAV:all (aggregate, abstract)
| |
+-- DAV:read +-- DAV:read
+-- DAV:write (aggregate, abstract) +-- DAV:write (aggregate, abstract)
| |
+-- http://www.acl.org/create +-- http://www.webdav.org/acl/create
+-- http://www.acl.org/update +-- http://www.webdav.org/acl/update
+-- http://www.acl.org/delete +-- http://www.webdav.org/acl/delete
Clemm, Hopkins, Sedlar, Whitehead [Page 16]
+-- DAV:read-acl +-- DAV:read-acl
+-- DAV:write-acl +-- DAV:write-acl
The DAV:current-user-privilege-set property contains two privileges, The DAV:current-user-privilege-set property contains two
DAV:read, and DAV:read-acl. This indicates that the current privileges, DAV:read, and DAV:read-acl. This indicates that the
authenticated user only has the ability to read the resource, and current authenticated user only has the ability to read the
read the DAV:acl property on the resource. resource, and read the DAV:acl property on the resource.
The DAV:acl property contains a set of four ACEs: The DAV:acl property contains a set of four ACEs:
ACE #1: The principal identified by the URL ACE #1: The principal identified by the URL
http://www.foo.org/users/esedlar is granted the DAV:read, DAV:write, http://www.foo.org/users/esedlar is granted the DAV:read,
and DAV:read-acl privileges. DAV:write, and DAV:read-acl privileges.
ACE #2: The principals identified by the URL ACE #2: The principals identified by the URL
http://www.foo.org/groups/marketing/ are denied the DAV:read http://www.foo.org/groups/marketing/ are denied the DAV:read
privilege. In this example, the principal URL identifies a group, privilege. In this example, the principal URL identifies a group,
which is represented by a collection principal. which is represented by a collection principal.
Clemm, Hopkins, Sedlar, Whitehead [Page 14]
ACE #3: In this ACE, the principal is a property principal, ACE #3: In this ACE, the principal is a property principal,
specifically the DAV:owner property. When evaluating this ACE, the specifically the DAV:owner property. When evaluating this ACE, the
value of the DAV:owner property is retrieved, and is examined to see value of the DAV:owner property is retrieved, and is examined to
if it contains a DAV:href XML element. If so, the URL within the see if it contains a DAV:href XML element. If so, the URL within
DAV:href element is read, and identifies a principal. In this ACE, the DAV:href element is read, and identifies a principal. In this
the owner is granted DAV:read-acl, and DAV:write-acl privileges. 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 ACE #4: This ACE grants the DAV:all principal (all users) the
DAV:read privilege. This ACE is inherited from the resource DAV:read privilege. This ACE is inherited from the resource
http://www.foo.org/top/, the parent collection of this resource. http://www.foo.org/top/, the parent collection of this resource.
6 ACL SEMANTICS 6 ACL SEMANTICS
The ACL semantics define how multiple ACEs that match the current The ACL semantics define how multiple ACEs that match the current
user are combined, what are the constraints on how ACEs can be user are combined, what are the constraints on how ACEs can be
ordered, and which principals must have an ACE. ordered, and which principals must have an ACE.
<!ELEMENT acl-semantics acl-sem*> <!ELEMENT acl-semantics acl-sem*>
<!ELEMENT acl-sem (ace-combination, ace-ordering, required- <!ELEMENT acl-sem (ace-combination, ace-ordering, required-
principal)> principal*)>
6.1 ACE Combination 6.1 ACE Combination
The DAV:ace-combination element defines how privileges from multiple The DAV:ace-combination element defines how privileges from
ACEs that match the current user will be combined to determine the multiple ACEs that match the current user will be combined to
access privileges for that user. Multiple ACEs may match the same determine the access privileges for that user. Multiple ACEs may
user because the same principal can appear in multiple ACEs, because match the same user because the same principal can appear in
multiple principals can identify the same user, and because one multiple ACEs, because multiple principals can identify the same
principal can be a member of another principal. user, and because one principal can be a member of another
principal.
<!ELEMENT ace-combination <!ELEMENT ace-combination
(first-match | all-grant-before-any-deny | no-deny)>
Clemm, Hopkins, Sedlar, Whitehead [Page 17]
(first-match | all-grant-before-any-deny | specific-deny-
overrides-grant)>
6.1.1 DAV:first-match ACE Combination 6.1.1 DAV:first-match ACE Combination
The ACEs are evaluated in the order in which they appear in the ACL. The ACEs are evaluated in the order in which they appear in the
If the first ACE that matches the current user does not grant all ACL. If the first ACE that matches the current user does not grant
the privileges needed for the request, the request MUST fail. all the privileges needed for the request, the request MUST fail.
<!ELEMENT first-match EMPTY> <!ELEMENT first-match EMPTY>
6.1.2 DAV:all-grant-before-any-deny ACE Combination 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. The ACEs are evaluated in the order in which they appear in the
If an evaluated ACE denies a privilege needed for the request, the ACL. If an evaluated ACE denies a privilege needed for the
request MUST fail. If all ACEs have been evaluated without the user request, the request MUST fail. If all ACEs have been evaluated
being granted all privileges needed for the request, the request without the user being granted all privileges needed for the
MUST fail. request, the request MUST fail.
<!ELEMENT all-grant-before-any-deny EMPTY> <!ELEMENT all-grant-before-any-deny EMPTY>
6.1.3 DAV:no-deny ACE Combination 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
Clemm, Hopkins, Sedlar, Whitehead [Page 15] All ACEs in the ACL are evaluated. An "individual ACE" is one
principal is a collection that contains a principal that identifies whose principal identifies the current user. A "group ACE" is one
the current user. A privilege is granted if it is granted by an whose principal is a collection that contains a principal that
individual ACE and not denied by an individual ACE, or if it is identifies the current user. A privilege is granted if it is
granted by a group ACE and not denied by an individual or group ACE. granted by an individual ACE and not denied by an individual ACE,
A request MUST fail if any of its needed privileges are not granted. or if it is granted by a group ACE and not denied by an individual
or group ACE. A request MUST fail if any of its needed privileges
are not granted.
<!ELEMENT no-deny EMPTY> <!ELEMENT specific-deny-overrides-grant EMPTY>
6.2 ACE Ordering 6.2 ACE Ordering
The DAV:ace-ordering element defines a constraint on how the ACEs The DAV:ace-ordering element defines a constraint on how the ACEs
can be ordered in the ACL. can be ordered in the ACL.
<!ELEMENT ace-ordering (deny-before-grant)? > <!ELEMENT ace-ordering (deny-before-grant)? >
6.2.1 DAV:deny-before-grant ACE Ordering 6.2.1 DAV:deny-before-grant ACE Ordering
skipping to change at page 27, line ? skipping to change at line 958
ACEs. ACEs.
<!ELEMENT deny-before-grant EMPTY> <!ELEMENT deny-before-grant EMPTY>
6.3 Required Principals 6.3 Required Principals
The required principal elements identify which principals must have The required principal elements identify which principals must have
an ACE defined in the ACL. an ACE defined in the ACL.
<!ELEMENT required-principal <!ELEMENT required-principal
(href | all | authenticated | unauthenticated | property | (href | all | authenticated | unauthenticated | property | self)>
self)>
For example, the following element requires that the ACE contain a Clemm, Hopkins, Sedlar, Whitehead [Page 18]
For example, the following element requires that the ACL contain a
DAV:owner property ACE: DAV:owner property ACE:
<D:required-principal xmlns:D="DAV:"> <D:required-principal xmlns:D="DAV:">
<D:property> <D:owner/> </D:property> <D:property> <D:owner/> </D:property>
</D:required-principal> </D:required-principal>
7 ACCESS CONTROL AND EXISTING METHODS 7 ACCESS CONTROL AND EXISTING METHODS
This section defines the impact of access control functionality on This section defines the impact of access control functionality on
existing methods. existing methods.
7.1 OPTIONS 7.1 OPTIONS
If the server supports access control, it MUST return "access- If the server supports access control, it MUST return "access-
control" as a field in the DAV response header from an OPTIONS control" as a field in the DAV response header from an OPTIONS
request on any resource implemented by that server. request on any resource implemented by that server.
7.1.1Example - OPTIONS 7.1.1Example - OPTIONS
>> REQUEST << >> Request <<
OPTIONS /foo.html HTTP/1.1 OPTIONS /foo.html HTTP/1.1
Host: www.webdav.org Host: www.webdav.org
Content-Length: 0 Content-Length: 0
Clemm, Hopkins, Sedlar, Whitehead [Page 16] >> Response <<
>> RESPONSE <<
HTTP/1.1 200 OK HTTP/1.1 200 OK
DAV: 1, 2, access-control DAV: 1, 2, access-control
Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL
In this example, the OPTIONS response indicates that the server In this example, the OPTIONS response indicates that the server
supports access control and that /foo.html can have its access supports access control and that /foo.html can have its access
control list modified by the ACL method. control list modified by the ACL method.
8 ACCESS CONTROL METHODS 8 ACCESS CONTROL METHODS
8.1 ACL 8.1 ACL
A DAV:acl property of a resource is modified by the ACL method. A The ACL method modifies the DAV:acl property of a resource. A new
new DAV:acl value must be written in its entirety, including any DAV:acl value must be written in its entirety, including any
inherited ACEs. Unless the DAV:acl property of the resource can be inherited ACEs. Unless the DAV:acl property of the resource can be
updated to be exactly the value specified in the ACL request, the updated to be exactly the value specified in the ACL request, the
ACL request MUST fail. If a server restricts the set of ACEs ACL request MUST fail. If a server restricts the set of ACEs
visible to the current user via the DAV:acl property, then the ACL visible to the current user via the DAV:acl property, then the ACL
request would only replace the set of ACEs visible to the current request would only replace the set of ACEs visible to the current
user, and would not affect any ACE that was not visible. user, and would not affect any ACE that was not visible.
In order to avoid overwriting DAV:acl changes by another client, a In order to avoid overwriting DAV:acl changes by another client, a
client SHOULD acquire a WebDAV lock on the resource before client SHOULD acquire a WebDAV lock on the resource before
retrieving the DAV:acl property of a resource that it intends on retrieving the DAV:acl property of a resource that it intends on
updating. updating.
Clemm, Hopkins, Sedlar, Whitehead [Page 19]
When submitting ACEs, clients MUST NOT include the optional prop
element (a child of the principal element). The purpose of this
restriction is to limit the scope of effect of the ACL method to
just the resource identified by the Request-URI; setting the prop
element would additionally require property modification for one or
more principal resources.
8.1.1 ACL Preconditions 8.1.1 ACL Preconditions
An implementation MAY enforce one or more of the following An implementation MAY enforce one or more of the following
constraints on an ACL request. If the constraint is violated, a 403 constraints on an ACL request. If the constraint is violated, a
(Forbidden) response MUST be returned and the indicated XML element 403 (Forbidden) response MUST be returned and the indicated XML
MUST be returned in the response body. element MUST be returned in the response body.
<DAV:protected/>: An implementation MAY protect an ACE from <DAV:protected/>: An implementation MAY protect an ACE from
modification or deletion. For example, some implementations modification or deletion. For example, some implementations
implicitly grant the DAV:owner of a resource DAV:read-acl and implicitly grant the DAV:owner of a resource DAV:read-acl and
DAV:write-acl privileges, and this cannot be changed by a client. DAV:write-acl privileges, and this cannot be changed by a client.
<DAV:too-many-aces/>: An implementation MAY limit the number of ACEs <DAV:too-many-aces/>: An implementation MAY limit the number of
in an ACL. However, ACL-compliant servers MUST support at least one ACEs in an ACL. However, ACL-compliant servers MUST support at
ACE granting privileges to a single principal, and one ACE granting least one ACE granting privileges to a single principal, and one
privileges to a collection principal. ACE granting privileges to a collection principal.
<DAV:non-inherited-must-precede-inherited/>: All non-inherited ACEs <DAV:non-inherited-must-precede-inherited/>: All non-inherited ACEs
MUST precede all inherited ACEs. MUST precede all inherited ACEs.
<DAV:deny-must-precede-grant/>: All non-inherited deny ACEs MUST <DAV:deny-must-precede-grant/>: All non-inherited deny ACEs MUST
precede all non-inherited grant ACEs. precede all non-inherited grant ACEs.
If the following precondition is not met, the server MUST return a
409 (Conflict) response, and the indicated XML element MUST be
returned in the response body:
<DAV:inhereted-exist-parent>: Inherited ACEs MUST exist on a parent
resource.
8.1.2 Example: the ACL method 8.1.2 Example: the ACL method
In the following example, user "fielding", authenticated by In the following example, user "fielding", authenticated by
information in the Authorization header, grants the principal information in the Authorization header, grants the principal
Clemm, Hopkins, Sedlar, Whitehead [Page 17]
identified by the URL http://www.foo.org/users/esedlar (i.e., the identified by the URL http://www.foo.org/users/esedlar (i.e., the
user "esedlar") read and write privileges, grants the owner of the user "esedlar") read and write privileges, grants the owner of the
resource read-acl and write-acl privileges, and grants everyone read resource read-acl and write-acl privileges, and grants everyone
privileges inherited from the parent collection read privileges inherited from the parent collection
http://www.foo.bar/top/. http://www.foo.bar/top/.
>> Request << >> Request <<
ACL /top/container/ HTTP/1.1 ACL /top/container/ HTTP/1.1
Host: www.foo.org Host: www.foo.org
Content-Type: text/xml; charset="utf-8" Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx Content-Length: xxxx
Authorization: Digest username="fielding", Authorization: Digest username="fielding",
realm="users@foo.org", nonce="...", realm="users@foo.org", nonce="...",
Clemm, Hopkins, Sedlar, Whitehead [Page 20]
uri="/top/container/", response="...", opaque="..." uri="/top/container/", response="...", opaque="..."
<?xml version="1.0" encoding="utf-8" ?> <?xml version="1.0" encoding="utf-8" ?>
<D:acl xmlns:D="DAV:"> <D:acl xmlns:D="DAV:">
<D:ace> <D:ace>
<D:principal> <D:principal>
<D:href>http://www.foo.org/users/esedlar</D:href> <D:href>http://www.foo.org/users/esedlar</D:href>
</D:principal> </D:principal>
<D:grant> <D:grant>
<D:privilege> <D:read/> </D:privilege> <D:privilege> <D:read/> </D:privilege>
skipping to change at page 27, line ? skipping to change at line 1109
>> Response << >> Response <<
HTTP/1.1 200 OK HTTP/1.1 200 OK
8.1.3 Example: ACL method failure due to omission of protected ACE 8.1.3 Example: ACL method failure due to omission of protected ACE
In the following request, user "fielding", authenticated by In the following request, user "fielding", authenticated by
information in the Authorization header, attempts to grant the information in the Authorization header, attempts to grant the
principal identified by the URL http://www.foo.org/users/esedlar principal identified by the URL http://www.foo.org/users/esedlar
(i.e., the user "esedlar") read privileges, but fails because an (i.e., the user "esedlar") read privileges. Prior to the request,
protected ACE has been omitted (e.g. the ACE granting the DAV:owner the DAV:acl property on the resource contained a protected ACE (see
DAV:read-acl and DAV:write-acl privileges must always be present Section 5.4.3) granting DAV:owner the DAV:read-acl and DAV:write-
since it is protected -- see Section 5.4.3). acl privileges. The ACL method invocation fails because this
protected ACE is omitted, thus violating the semantics of ACE
protection..
Clemm, Hopkins, Sedlar, Whitehead [Page 18]
>> Request << >> Request <<
ACL /top/container/ HTTP/1.1 ACL /top/container/ HTTP/1.1
Host: www.foo.org Host: www.foo.org
Content-Type: text/xml; charset="utf-8" Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx Content-Length: xxxx
Authorization: Digest username="fielding", Authorization: Digest username="fielding",
realm="users@foo.org", nonce="...", realm="users@foo.org", nonce="...",
uri="/top/container/", response="...", opaque="..." uri="/top/container/", response="...", opaque="..."
<?xml version="1.0" encoding="utf-8" ?> <?xml version="1.0" encoding="utf-8" ?>
Clemm, Hopkins, Sedlar, Whitehead [Page 21]
<D:acl xmlns:D="DAV:"> <D:acl xmlns:D="DAV:">
<D:ace> <D:ace>
<D:principal> <D:principal>
<D:href>http://www.foo.org/users/esedlar</D:href> <D:href>http://www.foo.org/users/esedlar</D:href>
</D:principal> </D:principal>
<D:grant> <D:grant>
<D:privilege> <D:read/> </D:privilege> </D:grant> <D:privilege> <D:read/> </D:privilege> </D:grant>
</D:ace> </D:ace>
</D:acl> </D:acl>
skipping to change at page 27, line ? skipping to change at line 1152
Content-Type: text/xml; charset="utf-8" Content-Type: text/xml; charset="utf-8"
Content-Length: xxx Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?> <?xml version="1.0" encoding="utf-8" ?>
<DAV:protected/> <DAV:protected/>
8.1.4 Example: ACL method failure due to inherited ACEs preceding non- 8.1.4 Example: ACL method failure due to inherited ACEs preceding non-
inherited ACEs inherited ACEs
In the following request, user "ejw", authenticated by information In the following request, user "ejw", authenticated by information
in the Authorization header, tries to change the access control list in the Authorization header, tries to change the access control
on the resource http://www.foo.org/top/index.html. This resource has list on the resource http://www.foo.org/top/index.html. This
two inherited ACEs. resource has two inherited ACEs.
Inherited ACE #1 grants the principal identified by URL Inherited ACE #1 grants the principal identified by URL
http://www.foo.org/users/ejw (i.e., the user "ejw") http://www.foo.org/users/ejw (i.e., the user "ejw")
http://www.foo.org/privs/write-all and DAV:read-acl privileges. On 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 this server, http://www.foo.org/privs/write-all is an aggregate
privilege containing DAV:write, and DAV:write-acl. privilege containing DAV:write, and DAV:write-acl.
Inherited ACE #2 grants principal DAV:all the DAV:read privilege. Inherited ACE #2 grants principal DAV:all the DAV:read privilege.
The request attempts to add a third ACE, granting the principal The request attempts to add a third ACE, granting the principal
identified by the URL http://www.foo.org/users/gclemm (i.e., the identified by the URL http://www.foo.org/users/gclemm (i.e., the
user "gclemm") DAV:write permission, but in the request places the user ôgclemmö) DAV:write permission, but in the request places the
inherited ACEs before the non-inherited ACEs, causing an error on inherited ACEs before the non-inherited ACEs, causing an error on
this specific server implementation. Note that on a different this specific server implementation. Note that on a different
implementation, this request might be accepted. implementation, this request might be accepted.
>> Request << >> Request <<
Clemm, Hopkins, Sedlar, Whitehead [Page 19]
ACL /top/index.html HTTP/1.1 ACL /top/index.html HTTP/1.1
Host: www.foo.org Host: www.foo.org
Content-Type: text/xml; charset="utf-8" Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx Content-Length: xxxx
Authorization: Digest username="ejw", Authorization: Digest username="ejw",
realm="users@foo.org", nonce="...", realm="users@foo.org", nonce="...",
uri="/top/index.html", response="...", opaque="..." uri="/top/index.html", response="...", opaque="..."
<?xml version="1.0" encoding="utf-8" ?> <?xml version="1.0" encoding="utf-8" ?>
<D:acl xmlns:D="DAV:" xmlns:F="http://www.foo.org/privs/"> <D:acl xmlns:D="DAV:" xmlns:F="http://www.foo.org/privs/">
Clemm, Hopkins, Sedlar, Whitehead [Page 22]
<D:ace> <D:ace>
<D:principal> <D:principal>
<D:href>http://www.foo.org/users/ejw</D:href> <D:href>http://www.foo.org/users/ejw</D:href>
</D:principal> </D:principal>
<D:grant> <D:grant>
<D:privilege><F:write-all/></D:privilege> <D:privilege><F:write-all/></D:privilege>
<D:privilege><D:read-acl/></D:privilege> <D:privilege><D:read-acl/></D:privilege>
</D:grant> </D:grant>
<D:inherited/> <D:inherited/>
</D:ace> </D:ace>
skipping to change at page 27, line ? skipping to change at line 1217
>> Response << >> Response <<
HTTP/1.1 403 Forbidden HTTP/1.1 403 Forbidden
Content-Type: text/xml; charset="utf-8" Content-Type: text/xml; charset="utf-8"
Content-Length: xxx Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?> <?xml version="1.0" encoding="utf-8" ?>
<DAV:non-inherited-must-precede-inherited/> <DAV:non-inherited-must-precede-inherited/>
8.1.5 Example: ACL method failure due to an attempt to set grant and 8.1.5 Example: ACL method failure due to an attempt to set grant and deny
deny in a single ACE. in a single ACE.
In this example, user "ygoland", authenticated by information in the In this example, user "ygoland", authenticated by information in
Authorization header, tries to change the access control list on the the Authorization header, tries to change the access control list
resource http://www.foo.org/diamond/engagement-ring.gif. The ACL on the resource http://www.foo.org/diamond/engagement-ring.gif. The
request includes a single, syntactically and semantically incorrect ACL request includes a single, syntactically and semantically
ACE, which attempts to grant the collection principal identified by incorrect ACE, which attempts to grant the collection principal
the URL http://www.foo.org/users/friends/ DAV:read privilege and identified by the URL http://www.foo.org/users/friends/ DAV:read
deny the principal identified by URL privilege and deny the principal identified by URL
http://www.foo.org/users/ygoland-so (i.e., the user "ygoland-so") http://www.foo.org/users/ygoland-so (i.e., the user "ygoland-so")
DAV:read privilege. However, it is illegal to have multiple DAV:read privilege. However, it is illegal to have multiple
Clemm, Hopkins, Sedlar, Whitehead [Page 20]
principal elements, as well as both a grant and deny element in the principal elements, as well as both a grant and deny element in the
same ACE, so the request fails due to poor syntax. same ACE, so the request fails due to poor syntax.
>> Request << >> Request <<
ACL /diamond/engagement-ring.gif HTTP/1.1 ACL /diamond/engagement-ring.gif HTTP/1.1
Host: www.foo.org Host: www.foo.org
Content-Type: text/xml; charset="utf-8" Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx Content-Length: xxxx
Authorization: Digest username="ygoland", Authorization: Digest username="ygoland",
Clemm, Hopkins, Sedlar, Whitehead [Page 23]
realm="users@foo.org", nonce="...", realm="users@foo.org", nonce="...",
uri="/diamond/engagement-ring.gif", response="...", uri="/diamond/engagement-ring.gif", response="...", opaque="..."
opaque="..."
<?xml version="1.0" encoding="utf-8" ?> <?xml version="1.0" encoding="utf-8" ?>
<D:acl xmlns:D="DAV:"> <D:acl xmlns:D="DAV:">
<D:ace> <D:ace>
<D:principal> <D:principal>
<D:href>http://www.foo.org/users/friends/</D:href> <D:href>http://www.foo.org/users/friends/</D:href>
</D:principal> </D:principal>
<D:grant><D:read/></D:grant> <D:grant><D:read/></D:grant>
<D:principal> <D:principal>
<D:href>http://www.foo.org/users/ygoland-so</D:href> <D:href>http://www.foo.org/users/ygoland-so</D:href>
skipping to change at page 27, line ? skipping to change at line 1270
HTTP/1.1 400 Bad Request HTTP/1.1 400 Bad Request
Content-Length: 0 Content-Length: 0
Note that if the request had been divided into two ACEs, one to Note that if the request had been divided into two ACEs, one to
grant, and one to deny, the request would have been syntactically grant, and one to deny, the request would have been syntactically
well formed. well formed.
9 INTERNATIONALIZATION CONSIDERATIONS 9 INTERNATIONALIZATION CONSIDERATIONS
In this specification, the only human-readable content can be found In this specification, the only human-readable content can be found
in the DAV:authentication-id property, found on principal resources. in the description XML element, found within the DAV:supported-
This property contains the name used to authenticate a principal, privilege-set property. This element contains a human-readable
typically by a user entering this name into a password entry screen. description of the capabilities controlled by a privilege. As a
As a result, the authentication-id must be capable of representing result, the description element must be capable of representing
names in multiple character sets. Since DAV:authentication-id is a descriptions in multiple character sets. Since the description
WebDAV property, it is represented on-the-wire as XML [REC-XML], and element is found within a WebDAV property, it is represented on-
hence can leverage XML's language tagging and character set encoding the-wire as XML [REC-XML], and hence can leverage XML's language
capabilities. Specifically, XML processors must, at minimum, be able tagging and character set encoding capabilities. Specifically, XML
to read XML elements encoded using the UTF-8 [UTF-8] encoding of the processors must, at minimum, be able to read XML elements encoded
ISO 10646 multilingual plane. XML examples in this specification using the UTF-8 [UTF-8] encoding of the ISO 10646 multilingual
demonstrate use of the charset parameter of the Content-Type header, plane. XML examples in this specification demonstrate use of the
as defined in [RFC3023], as well as the XML "encoding" attribute, charset parameter of the Content-Type header, as defined in
which together provide charset identification information for MIME [RFC3023], as well as the XML "encoding" attribute, which together
and XML processors. provide charset identification information for MIME and XML
processors.
Clemm, Hopkins, Sedlar, Whitehead [Page 21] For XML elements other than the description element, it is expected
For properties other than DAV:authentication-id, it is expected that that implementations will treat the property names, privilege
implementations will treat the property names and values as tokens, names, and values as tokens, and convert these tokens into human-
and convert these tokens into human-readable text in the user's readable text in the user's language and character set when
language and character set when displayed to a person. Only a displayed to a person. Only a generic WebDAV property display
generic WebDAV property display utility would display these values utility would display these values in their raw form to a human
in their raw form. user.
Clemm, Hopkins, Sedlar, Whitehead [Page 24]
For error reporting, we follow the convention of HTTP/1.1 status For error reporting, we follow the convention of HTTP/1.1 status
codes, including with each status code a short, English description codes, including with each status code a short, English description
of the code (e.g., 200 (OK)). While the possibility exists that a of the code (e.g., 200 (OK)). While the possibility exists that a
poorly crafted user agent would display this message to a user, poorly crafted user agent would display this message to a user,
internationalized applications will ignore this message, and display internationalized applications will ignore this message, and
an appropriate message in the user's language and character set. display an appropriate message in the user's language and character
set.
Further internationalization considerations for this protocol are Further internationalization considerations for this protocol are
described in the WebDAV Distributed Authoring protocol specification described in the WebDAV Distributed Authoring protocol
[RFC2518]. specification [RFC2518].
10 SECURITY CONSIDERATIONS 10 SECURITY CONSIDERATIONS
Applications and users of this access control protocol should be Applications and users of this access control protocol should be
aware of several security considerations, detailed below. In aware of several security considerations, detailed below. In
addition to the discussion in this document, the security addition to the discussion in this document, the security
considerations detailed in the HTTP/1.1 specification [RFC2616], the considerations detailed in the HTTP/1.1 specification [RFC2616],
WebDAV Distributed Authoring Protocol specification [RFC2518], and the WebDAV Distributed Authoring Protocol specification [RFC2518],
the XML Media Types specification [RFC3023] should be considered in and the XML Media Types specification [RFC3023] should be
a security analysis of this protocol. considered in a security analysis of this protocol.
10.1 Increased Risk of Compromised Users 10.1 Increased Risk of Compromised Users
In the absence of a mechanism for remotely manipulating access In the absence of a mechanism for remotely manipulating access
control specifications, if a single user's authentication control lists, if a single user's authentication credentials are
credentials are compromised, only those resources for which the user compromised, only those resources for which the user has access
has access permission can be read, modified, moved, or deleted. With permission can be read, modified, moved, or deleted. With the
the introduction of this access control protocol, if a single introduction of this access control protocol, if a single
compromised user has the ability to change ACLs for a broad range of compromised user has the ability to change ACLs for a broad range
other users (e.g., a super-user), the number of resources that could of other users (e.g., a super-user), the number of resources that
be altered by a single compromised user increases. This risk can be could be altered by a single compromised user increases. This risk
mitigated by limiting the number of people who have write-acl can be mitigated by limiting the number of people who have write-
privileges across a broad range of resources. acl privileges across a broad range of resources.
10.2 Authentication-id Property and Dictionary Attacks
Every principal has a DAV:authentication-id property defined on it,
which provides the name used to authenticate this principal,
typically the username portion of a username/password authentication
scheme. An attacker can use the information in this property when
attempting either a brute-force, or a dictionary attack to guess the
principal's identifying password. By providing the username in
DAV:authentication-id, the scope of an attack can be reduced to a
single, valid username. Furthermore, it is possible that principals
can potentially belong to a collection. In this case, it is possible
to use the PROPFIND method to retrieve the DAV:authentication-id
property from all of the principals in a collection, thus providing
multiple usernames that can be the focus of attack.
Clemm, Hopkins, Sedlar, Whitehead [Page 22]
To reduce this risk, the DAV:authentication-id property should not
be world-readable. Which principals are granted default read
privilege for DAV:authentication-id should be carefully considered
in any deployment of this protocol.
10.3 Risks of the read-acl Privilege 10.2 Risks of the read-acl and cuprivset Privileges
The ability to read the access privileges (stored in the DAV:acl The ability to read the access privileges (stored in the DAV:acl
property), or the privileges permitted the currently authenticated property), or the privileges permitted the currently authenticated
user (stored in the DAV:current-user-privilege-set property) on a user (stored in the DAV:current-user-privilege-set property) on a
resource may seem innocuous, since reading an ACL cannot possibly resource may seem innocuous, since reading an ACL cannot possibly
affect the resource's state. However, if all resources have world- affect the resource's state. However, if all resources have world-
readable ACLs, it is possible to perform an exhaustive search for readable ACLs, it is possible to perform an exhaustive search for
those resources that have inadvertently left themselves in a those resources that have inadvertently left themselves in a
vulnerable state, such as being world-writeable. In particular, the vulnerable state, such as being world-writeable. In particular, the
property retrieval method PROPFIND, executed with Depth infinity on property retrieval method PROPFIND, executed with Depth infinity on
an entire hierarchy, is a very efficient way to retrieve the DAV:acl an entire hierarchy, is a very efficient way to retrieve the
or DAV:current-user-privilege-set properties. Once found, this DAV:acl or DAV:current-user-privilege-set properties. Once found,
vulnerability can be exploited by a denial of service attack in this vulnerability can be exploited by a denial of service attack
which the open resource is repeatedly overwritten. Alternately, in which the open resource is repeatedly overwritten. Alternately,
writeable resources can be modified in undesirable ways. writeable resources can be modified in undesirable ways.
To reduce this risk, read-acl privileges should not be granted to To reduce this risk, read-acl privileges should not be granted to
unauthenticated principals, and restrictions on read-acl privileges unauthenticated principals, and restrictions on read-acl and
for authenticated principals should be carefully analyzed when
deploying this protocol. Clemm, Hopkins, Sedlar, Whitehead [Page 25]
cuprivset 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.
11 AUTHENTICATION 11 AUTHENTICATION
Authentication mechanisms defined in WebDAV also apply to this Authentication mechanisms defined in WebDAV also apply to this
WebDAV Access Control Protocol, in particular the Basic and Digest WebDAV Access Control Protocol, in particular the Basic and Digest
authentication mechanisms defined in [RFC2617]. authentication mechanisms defined in [RFC2617].
12 IANA CONSIDERATIONS 12 IANA CONSIDERATIONS
This document uses the namespace defined by [RFC2518] for XML This document uses the namespace defined by [RFC2518] for XML
elements. All other IANA considerations mentioned in [RFC2518] also elements. All other IANA considerations mentioned in [RFC2518]
applicable to WebDAV ACL. also applicable to WebDAV ACL.
13 INTELLECTUAL PROPERTY 13 INTELLECTUAL PROPERTY
The following notice is copied from RFC 2026, section 10.4, and The following notice is copied from RFC 2026, section 10.4, and
describes the position of the IETF concerning intellectual property describes the position of the IETF concerning intellectual property
claims made against this document. claims made against this document.
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to intellectual property or other rights that might be claimed to
pertain to the implementation or use other technology described in pertain to the implementation or use other technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on
IETF's procedures with respect to rights in standards-track and the IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances claims of rights made available for publication and any assurances
of licenses to be made available, or the result of an attempt made of licenses to be made available, or the result of an attempt made
Clemm, Hopkins, Sedlar, Whitehead [Page 23]
to obtain a general license or permission for the use of such to obtain a general license or permission for the use of such
proprietary rights by implementers or users of this specification proprietary rights by implementers or users of this specification
can be obtained from the IETF Secretariat. can be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to practice rights that may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF
Director. Executive Director.
14 ACKNOWLEDGEMENTS 14 ACKNOWLEDGEMENTS
This protocol is the collaborative product of the WebDAV ACL design This protocol is the collaborative product of the WebDAV ACL design
team: Bernard Chester, Geoff Clemm (Rational), Anne Hopkins team: Bernard Chester, Geoff Clemm (Rational), Anne Hopkins
Clemm, Hopkins, Sedlar, Whitehead [Page 26]
(Microsoft), Barry Lind (Xythos), Sean Lyndersay (Microsoft), Eric (Microsoft), Barry Lind (Xythos), Sean Lyndersay (Microsoft), Eric
Sedlar (Oracle), Greg Stein (Apache.org), and Jim Whitehead (UC Sedlar (Oracle), Greg Stein (Apache.org), and Jim Whitehead (UC
Santa Cruz). The authors are grateful for the detailed review and Santa Cruz). The authors are grateful for the detailed review and
comments provided by Jim Amsden, Gino Basso, Murthy Chintalapati, comments provided by Jim Amsden, Gino Basso, Murthy Chintalapati,
Dennis Hamilton, Ron Jacobs, Chris Knight, and Remy Maucherat. Prior Dennis Hamilton, Laurie Harper, Ron Jacobs, Chris Knight, and Remy
work on WebDAV access control protocols has been performed by Yaron Maucherat. Prior work on WebDAV access control protocols has been
Goland, Paul Leach, Lisa Dusseault, Howard Palmer, and Jon Radoff. performed by Yaron Goland, Paul Leach, Lisa Dusseault, Howard
We would like to acknowledge the foundation laid for us by the Palmer, and Jon Radoff. We would like to acknowledge the foundation
authors of the WebDAV and HTTP protocols upon which this protocol is laid for us by the authors of the WebDAV and HTTP protocols upon
layered, and the invaluable feedback from the WebDAV working group. which this protocol is layered, and the invaluable feedback from
the WebDAV working group.
15 REFERENCES 15 REFERENCES
15.1 Normative References 15.1 Normative References
[RFC2119] S.Bradner, "Key words for use in RFCs to Indicate [RFC2119] S.Bradner, "Key words for use in RFCs to Indicate
Requirement Levels." RFC 2119, BCP 14, Harvard, March, 1997. Requirement Levels." RFC 2119, BCP 14, Harvard, March, 1997.
[REC-XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible [REC-XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible
Markup Language (XML)." World Wide Web Consortium Recommendation Markup Language (XML)." World Wide Web Consortium Recommendation
REC-xml-19980210. http://www.w3.org/TR/REC-xml-19980210. REC-xml-19980210. http://www.w3.org/TR/REC-xml-19980210.
[RFC2616] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, L. [RFC2616] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, L.
Masinter, P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol Masinter, P. Leach, and T. Berners-Lee, "Hypertext Transfer
-- HTTP/1.1." RFC 2616. U.C.Irvine, Compaq, Xerox, Microsoft, Protocol -- HTTP/1.1." RFC 2616. U.C.Irvine, Compaq, Xerox,
MIT/LCS, June, 1999. Microsoft, MIT/LCS, June, 1999.
[RFC2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, P. [RFC2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, P.
Leach, A. Luotonen, L. Stewart, "HTTP Authentication: Basic and Leach, A. Luotonen, L. Stewart, "HTTP Authentication: Basic and
Digest Access Authentication. " RFC 2617. Northwestern University, Digest Access Authentication. " RFC 2617. Northwestern University,
Verisign, AbiSource, Agranat, Microsoft, Netscape, Open Market, Verisign, AbiSource, Agranat, Microsoft, Netscape, Open Market,
June, 1999. June, 1999.
[RFC2518] Y. Goland, E. Whitehead, A. Faizi, S. R. Carter, D. [RFC2518] Y. Goland, E. Whitehead, A. Faizi, S. R. Carter, D.
Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV." RFC Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV." RFC
2518. Microsoft, U.C.Irvine, Netscape, Novell, February, 1999. 2518. Microsoft, U.C.Irvine, Netscape, Novell, February, 1999.
[RFC2368] P. Hoffman, L. Masinter, J. Zawinski, "The mailto URL
scheme." RFC 2368. Internet Mail Consortium, Xerox, Netscape, July,
1998.
[RFC2255] T. Howes, M. Smith, "The LDAP URL Format." RFC 2255.
Netscape, December, 1997.
[RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types." RFC [RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types." RFC
3023. IBM Tokyo Research Laboratory, simonstl.com, Skymoon Ventures, 3023. IBM Tokyo Research Laboratory, simonstl.com, Skymoon
January, 2001. Ventures, January, 2001.
Clemm, Hopkins, Sedlar, Whitehead [Page 24]
[UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode and [UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode and
ISO 10646." RFC 2279. Alis Technologies. January, 1998. ISO 10646." RFC 2279. Alis Technologies. January, 1998.
Clemm, Hopkins, Sedlar, Whitehead [Page 27]
15.2Informational References 15.2Informational References
[RFC2026] S.Bradner, "The Internet Standards Process û Revision 3." [RFC2026] S.Bradner, "The Internet Standards Process -- Revision 3."
RFC 2026, BCP 9. Harvard, October, 1996. RFC 2026, BCP 9. Harvard, October, 1996.
16 AUTHORS' ADDRESSES 16 AUTHORS' ADDRESSES
Geoffrey Clemm Geoffrey Clemm
Rational Software Rational Software
20 Maguire Road 20 Maguire Road
Lexington, MA 02421 Lexington, MA 02421
Email: geoffrey.clemm@rational.com Email: geoffrey.clemm@rational.com
skipping to change at page 27, line ? skipping to change at line 1502
17 APPENDICIES 17 APPENDICIES
17.1XML Document Type Definition 17.1XML Document Type Definition
<!-- Privileges --> <!-- Privileges -->
<!ELEMENT read EMPTY> <!ELEMENT read EMPTY>
<!ELEMENT write EMPTY> <!ELEMENT write EMPTY>
<!ELEMENT read-acl EMPTY> <!ELEMENT read-acl EMPTY>
<!ELEMENT read-cuprivset EMPTY>
<!ELEMENT write-acl EMPTY> <!ELEMENT write-acl EMPTY>
<!ELEMENT all EMPTY> <!ELEMENT all EMPTY>
<!-- Principal Properties (Section 4) --> <!-- Principal Properties (Section 4) -->
Clemm, Hopkins, Sedlar, Whitehead [Page 25]
<!ELEMENT is-principal (#PCDATA)> <!ELEMENT is-principal (#PCDATA)>
<!ELEMENT authentication-id (#PCDATA)>
<!ELEMENT alternate-URL (href*)>
Clemm, Hopkins, Sedlar, Whitehead [Page 28]
<!-- Access Control Properties (Section 5) --> <!-- Access Control Properties (Section 5) -->
<!-- DAV:owner Property (Section 5.1) --> <!-- DAV:owner Property (Section 5.1) -->
<!ELEMENT owner (href prop?)> <!ELEMENT owner (href prop?)>
<!ELEMENT prop (see [RFC2518], section 12.11)> <!ELEMENT prop (see [RFC2518], section 12.11)>
<!-- DAV:supported-privilege-set Property (Section 5.2) --> <!-- DAV:supported-privilege-set Property (Section 5.2) -->
<!ELEMENT supported-privilege-set (supported-privilege*)> <!ELEMENT supported-privilege-set (supported-privilege*)>
skipping to change at page 27, line ? skipping to change at line 1561
<!ELEMENT grant (privilege+)> <!ELEMENT grant (privilege+)>
<!ELEMENT deny (privilege+)> <!ELEMENT deny (privilege+)>
<!ELEMENT privilege ANY> <!ELEMENT privilege ANY>
<!ELEMENT protected EMPTY> <!ELEMENT protected EMPTY>
<!ELEMENT inherited (href)> <!ELEMENT inherited (href)>
<!-- DAV:principal-collection-set Property (Section 5.6) --> <!-- DAV:principal-collection-set Property (Section 5.6) -->
Clemm, Hopkins, Sedlar, Whitehead [Page 26]
<!ELEMENT principal-collection-set (href*)> <!ELEMENT principal-collection-set (href*)>
Clemm, Hopkins, Sedlar, Whitehead [Page 29]
<!-- DAV:acl-semantics Property (Section 6) --> <!-- DAV:acl-semantics Property (Section 6) -->
<!ELEMENT acl-semantics acl-sem*> <!ELEMENT acl-semantics acl-sem*>
<!ELEMENT acl-sem (ace-combination, ace-ordering, required- <!ELEMENT acl-sem (ace-combination, ace-ordering, required-
principal)> principal*)>
<!ELEMENT ace-combination <!ELEMENT ace-combination
(first-match | all-grant-before-any-deny | no-deny)> (first-match | all-grant-before-any-deny | specific-deny-
overrides-grant)>
<!ELEMENT first-match EMPTY> <!ELEMENT first-match EMPTY>
<!ELEMENT all-grant-before-any-deny EMPTY> <!ELEMENT all-grant-before-any-deny EMPTY>
<!ELEMENT no-deny EMPTY> <!ELEMENT specific-deny-overrides-grant EMPTY>
<!ELEMENT ace-ordering (deny-before-grant)? > <!ELEMENT ace-ordering (deny-before-grant)? >
<!ELEMENT deny-before-grant EMPTY> <!ELEMENT deny-before-grant EMPTY>
<!ELEMENT required-principal <!ELEMENT required-principal
(href | all | authenticated | unauthenticated | property | (href | all | authenticated | unauthenticated | property | self)>
self)>
<!-- ACL method preconditions (Section 8.1.1) --> <!-- ACL method preconditions (Section 8.1.1) -->
<!ELEMENT protected EMPTY> <!ELEMENT protected EMPTY>
<!ELEMENT too-many-aces EMPTY> <!ELEMENT too-many-aces EMPTY>
<!ELEMENT non-inherited-must-precede-inherited EMPTY> <!ELEMENT non-inherited-must-precede-inherited EMPTY>
<!ELEMENT deny-must-precede-grant EMPTY> <!ELEMENT deny-must-precede-grant EMPTY>
<!ELEMENT acl-requires-lock-token EMPTY> <!ELEMENT acl-requires-lock-token EMPTY>
<!ELEMENT inherited-exist-parent EMPTY>
Clemm, Hopkins, Sedlar, Whitehead [Page 30]
 End of changes. 

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