draft-ietf-webdav-acl-03.txt   draft-ietf-webdav-acl-04.txt 
INTERNET-DRAFT Geoffrey Clemm, Rational Software INTERNET-DRAFT Geoffrey Clemm, Rational Software
draft-ietf-webdav-acl-03 Anne Hopkins, Microsoft draft-ietf-webdav-acl-04 Anne Hopkins, Microsoft Corporation
Corporation
Eric Sedlar, Oracle Corporation Eric Sedlar, Oracle Corporation
Jim Whitehead, U.C. Santa Cruz Jim Whitehead, U.C. Santa Cruz
Expires May 24, 2001 November 24, 2000 Expires July 21, 2001 January 21, 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 This document is an Internet-Draft and is in full conformance with all
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
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Abstract Abstract
This document specifies a set of methods, headers, and message This document specifies a set of methods, headers, and message bodies
bodies that define the WebDAV Access Control extensions to the that define the WebDAV Access Control extensions to the HTTP/1.1
HTTP/1.1 protocol. This protocol permits a client to remotely read protocol. This protocol permits a client to remotely read and modify
and modify access control lists that instruct a server whether to access control lists that instruct a server whether to grant or deny
grant or deny operations upon a resource (such as HTTP method operations upon a resource (such as HTTP method invocations) by a given
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 Force. Comments on this draft are welcomed, and should be addressed to
to the acl@webdav.org mailing list. Other related documents can be the acl@webdav.org mailing list. Other related documents can be found
found at http://www.webdav.org/acl/, and at 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......................................................3
1.1 Terms .................................................3 1.1 Terms..........................................................4
1.2 Notational Conventions ................................4 1.2 Notational Conventions.........................................5
2 PRINCIPALS ..............................................4 2 PRINCIPALS........................................................5
3 PRIVILEGES ..............................................5 3 PRIVILEGES........................................................5
3.1 DAV:read Privilege ....................................5 3.1 DAV:read Privilege.............................................6
3.2 DAV:write Privilege ...................................6 3.2 DAV:write Privilege............................................6
3.3 DAV:read-acl Privilege ................................6 3.3 DAV:read-acl Privilege.........................................7
3.4 DAV:write-acl Privilege ...............................6 3.4 DAV:write-acl Privilege........................................7
3.5 DAV:all Privilege .....................................6 3.5 DAV:all Privilege..............................................7
4 PRINCIPAL PROPERTIES ....................................6 4 PRINCIPAL PROPERTIES..............................................7
4.1 DAV:is-principal ......................................6 4.1 DAV:is-principal...............................................7
4.2 DAV:authentication-id .................................6 4.2 DAV:authentication-id..........................................7
5 ACCESS CONTROL PROPERTIES ...............................7 5 ACCESS CONTROL PROPERTIES.........................................8
5.1 DAV:owner .............................................7 5.1 DAV:owner......................................................8
5.2 DAV:supported-privilege-set ...........................7 5.2 DAV:supported-privilege-set....................................8
5.3 DAV:current-user-privilege-set ........................8 5.3 DAV:current-user-privilege-set.................................9
5.4 DAV:acl ...............................................8 5.4 DAV:acl........................................................9
5.4.1 ACE Principal .....................................8 5.4.1 ACE Principal................................................9
5.4.2 ACE Grant and Deny ................................9 5.4.2 ACE Grant and Deny..........................................10
5.4.3 ACE Protection ...................................10 5.4.3 ACE Protection..............................................11
5.4.4 ACE Inheritance ..................................10 5.4.4 ACE Inheritance.............................................11
5.5 DAV:acl-semantics ....................................10 5.5 DAV:acl-semantics.............................................11
5.5.1 first-match Semantics ............................14 5.6 DAV:principal-collection-set..................................11
5.5.2 all-grant-before-any-deny Semantics ..............14 5.7 Example: PROPFIND to retrieve access control properties.......12
5.5.3 no-deny Semantics ................................14
5.6 DAV:principal-collection-set .........................10
5.7 Example: PROPFIND to retrieve access control properties11
6 ACCESS CONTROL AND EXISTING METHODS ....................14 6 ACL SEMANTICS....................................................15
6.1 OPTIONS ..............................................15 6.1 ACE Combination...............................................15
6.1.1 Example - OPTIONS ................................15 6.1.1 DAV:first-match ACE Combination.............................15
6.1.2 DAV:all-grant-before-any-deny ACE Combination...............15
6.1.3 DAV:no-deny ACE Combination.................................15
6.2 ACE Ordering..................................................16
6.2.1 DAV:deny-before-grant ACE Ordering..........................16
6.3 Required Principals...........................................16
7 ACCESS CONTROL METHODS .................................16 7 ACCESS CONTROL AND EXISTING METHODS..............................16
7.1 ACL ..................................................16 7.1 OPTIONS.......................................................16
7.1.1 ACL Preconditions ................................16 7.1.1 Example - OPTIONS...........................................16
7.1.2 Example: the ACL method ..........................17
7.1.3 Example: ACL method failure ......................17
8 INTERNATIONALIZATION CONSIDERATIONS ....................18 8 ACCESS CONTROL METHODS...........................................17
8.1 ACL...........................................................17
8.1.1 ACL Preconditions...........................................17
8.1.2 Example: the ACL method.....................................17
8.1.3 Example: ACL method failure due to omission of protected ACE18
8.1.4 Example: ACL method failure due to inherited ACEs preceding
non-inherited ACEs................................................19
8.1.5 Example: ACL method failure due to an attempt to set grant and
deny in a single ACE..............................................20
9 SECURITY CONSIDERATIONS ................................19 Clemm, Hopkins, Sedlar, Whitehead [Page 2]
9 INTERNATIONALIZATION CONSIDERATIONS..............................21
10 AUTHENTICATION .......................................20 10 SECURITY CONSIDERATIONS........................................22
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 IANA CONSIDERATIONS ..................................20 11 AUTHENTICATION.................................................23
12 INTELLECTUAL PROPERTY ................................20 12 IANA CONSIDERATIONS............................................23
13 ACKNOWLEDGEMENTS .....................................21 13 INTELLECTUAL PROPERTY..........................................23
Clemm, Hopkins, Sedlar, Whitehead [Page 2] 14 ACKNOWLEDGEMENTS...............................................24
14 REFERENCES ...........................................21
15 AUTHORS' ADDRESSES ...................................22 15 REFERENCES.....................................................24
15.1 Normative References..........................................24
15.2 Informational References......................................25
16 STILL TO DO ..........................................22 16 AUTHORS' ADDRESSES.............................................25
17 APPENDICIES....................................................25
17.1 XML Document Type Definition..................................25
1 INTRODUCTION 1 INTRODUCTION
The goal of the WebDAV access control extensions is to provide The goal of the WebDAV access control extensions is to provide an
an interoperable mechanism for handling discretionary access interoperable mechanism for handling discretionary access control
control for content in WebDAV servers. WebDAV access control for content in WebDAV servers. WebDAV access control can be
can be implemented on content repositories with security as implemented on content repositories with security as simple as that
simple as that of a UNIX file system, as well as more of a UNIX file system, as well as more sophisticated models. The
sophisticated models. The underlying principle of access underlying principle of access control is that who you are
control is that who you are determines how you can access a determines how you can access a resource. The "who you are" is
resource. The "who you are" is defined by a "principal" defined by a "principal" identifier; users, client software,
identifier; users, client software, servers, and groups of the servers, and groups of the previous have principal identifiers. The
previous have principal identifiers. The "how" is determined "how" is determined by a single "access control list" (ACL)
by a single "access control list" (ACL) associated with a associated with a resource. An ACL contains a set of "access
resource. An ACL contains a set of "access control entries" control entries" (ACEs), where each ACE specifies a principal and a
(ACEs), where each ACE specifies a principal and a set of set of privileges that are either granted or denied to that
rights that are either granted or denied to that principal. principal. When a principal submits an operation (such as an HTTP or
When a principal submits an operation (such as an HTTP or WebDAV method) to a resource for execution, the server evaluates the
WebDAV method) to a resource for execution, the server ACEs in the ACL to determine if the principal has permission for
evaluates the ACEs in the ACL to determine if the principal that operation.
has permission for that operation.
This specification has intentionally omits discussion of This specification intentionally omits discussion of authentication,
authentication, as the HTTP protocol already has a number of as the HTTP protocol already has a number of authentication
authentication mechanisms[RFC2617] . Some authentication mechanisms [RFC2617]. Some authentication mechanism (such as HTTP
mechanism (such as HTTP Digest Authentication, which all Digest Authentication, which all WebDAV compliant implementations
WebDAV compliant implementations are required to support) must are required to support) must be available to validate the identity
be availableto validate the identity of a principal. of a principal.
In the interests of timeliness, the following set of security In the interests of timeliness, the following set of security
mechanisms is currently viewed as out of scope of this mechanisms are not addressed by this document:
document:
* Access control that applies only to a particular property Clemm, Hopkins, Sedlar, Whitehead [Page 3]
on a resource, rather than the entire resource. * Access control that applies only to a particular property on
a resource, 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 defined collection of principals) dynamically 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 * Specification of an ACL that applies globally to a method,
method, rather than to a particular resource rather than to a particular resource.
This specification is organized as follows. Section 1.1 defines key
concepts used throughout the specification, and is followed by more
in-depth discussion of principals (Section 2), and privileges
(Section 3). Properties defined on principals are specified in
Section 4, and access control properties for content resources are
specified in Section 5. The semantics of access control lists are
described in Section 6, including sections on ACE combination
(Section 6.1), ACE ordering (Section 6.2), and principals required
to be present in an ACE (Section 6.3). Client discovery of access
control capability using OPTIONS is described in Section 7.1, and
the access control setting method, ACL, is specified in Section 8.
Internationalization considerations (Section 9) and security
considerations (Section 10) round out the specification. An appendix
(Section 17.1) provides an XML Document Type Definition (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:
Clemm, Hopkins, Sedlar, Whitehead [Page 3]
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
A "principal collection" is a group of principals, and is
represented in this protocol by a WebDAV collection containing HTTP
resources that represent principals, and principal collections.
privilege privilege
A "privilege" controls access to a particular set of HTTP A "privilege" controls access to a particular set of HTTP operations
operations on a resource. on a resource.
aggregate privilege aggregate privilege
An "aggregate privilege " is a privilege that comprises a set An "aggregate privilege" is a privilege that contains a set of other
of other privileges. privileges.
abstract privilege
Clemm, Hopkins, Sedlar, Whitehead [Page 4]
The modifier "abstract", when applied to an atomic or aggregate
privilege, means the privilege cannot be set in an access control
element (ace).
access control list (acl) access control list (acl)
An "acl " is a list of access control elements that define An "acl" is a list of access control elements that define access
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 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 An "inherited ace" is an ace that is shared from the acl of another
another resource. resource.
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 elements is described in Section 2.1 of [RFC2616]. Because this
this augmented BNF uses the basic production rules provided in augmented BNF uses the basic production rules provided in Section
Section 2.2 of [RFC2616], those rules apply to this document 2.2 of [RFC2616], those rules apply to this document as well.
as well.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
"OPTIONAL" in this document are to be interpreted as described document are to be interpreted as described in [RFC2119].
in [RFC2119].
2 PRINCIPALS 2 PRINCIPALS
A principal is an HTTP resource that represents a distinct A principal is an HTTP resource that represents a distinct human or
human or computational actor that initiates access to network computational actor that initiates access to network resources. On
resources. On many implementations, users and groups are many implementations, users and groups are represented as
represented as principals; other types of principals are also principals; other types of principals are also possible. Although
possible. Although an implementation MAY support PROPFIND an implementation MAY support PROPFIND and PROPPATCH to access and
and PROPPATCH to access and modify information about a modify information about a principal, it is not required to do so.
principal, it is not required to do so.
Clemm, Hopkins, Sedlar, Whitehead [Page 4] A principal resource may or may not be a collection. A collection
A principal resource may or may not be a collection. A principal may only contain other principals (not other types of
collection principal may only contain other principals (not resources). Servers that support aggregation of principals (e.g.
other types of resources). Servers that support aggregation groups of users or other groups) MUST manifest them as collection
of principals (e.g. groups of users or other groups) MUST principals. The WebDAV methods for examining and maintaining
manifest them as collection principals. The WebDAV methods collections (e.g. DELETE, PROPFIND) MAY be used to maintain
for examining and maintaining collections (e.g. DELETE, collection principals. Membership in a collection principal is
PROPFIND) MAY be used to maintain collection principals. recursive, so a principal in a collection principal GRPA contained
Membership in a collection principal is recursive, so a by collection principal GRPB is a member of both GRPA and GRPB.
principal in a collection principal GRPA contained by Implementations not supporting recursive membership in principal
collection principal GRPB is a member of both GRPA and GRPB. collections can return an error if the client attempts to bind
Implementations not supporting recursive membership in collection principals into other collection principals.
principal collections can return an error if the client
attempts to bind collection principals into other collection
principals.
3 PRIVILEGES 3 PRIVILEGES
Ability to perform a given method on a resource SHOULD be Ability to perform a given method on a resource SHOULD be controlled
controlled by one or more privileges. Authors of protocol by one or more privileges. Authors of protocol extensions that
extensions that define new HTTP methods SHOULD specify which
privileges (by defining new privileges, or mapping to ones
below) are required to perform the method. A principal with
no privileges to a resource SHOULD be denied any HTTP access
to that resource.
Privileges may be aggregates of other privileges. If a Clemm, Hopkins, Sedlar, Whitehead [Page 5]
principal is granted or denied an aggregate privilege, it is define new HTTP methods SHOULD specify which privileges (by defining
semantically equivalent to granting or denying each of the new privileges, or mapping to ones below) are required to perform
aggregated privileges individually. For example, an the method. A principal with no privileges to a resource SHOULD be
implementation may define add-member and remove-member denied any HTTP access to that resource.
privileges that control the ability to add and remove an
internal member of a collection. Since these privileges
control the ability to update the state of a collection, these
privileges would be aggregated by the DAV:write privilege on a
collection, and granting the DAV:write privilege on a
collection would also grant the add-member and remove-member
privileges.
The set of privileges that apply to a particular resource may Privileges may be containers of other privileges, in which case they
vary with the DAV:resourcetype of the resource, as well as are termed aggregate privileges. If a principal is granted or
between different server implementations. To promote denied an aggregate privilege, it is semantically equivalent to
interoperability, however, WebDAV defines a set of well-known granting or denying each of the aggregated privileges individually.
privileges (e.g. DAV:read and DAV:write), which can at least For example, an implementation may define add-member and remove-
be used to classify the other privileges defined on a member privileges that control the ability to add and remove an
particular resource. internal member of a collection. Since these privileges control the
ability to update the state of a collection, these privileges would
be aggregated by the DAV:write privilege on a collection, and
granting the DAV:write privilege on a collection would also grant
the add-member and remove-member privileges.
Privileges may have the quality of being abstract, in which case
they cannot be set in an ACE. Aggregate and atomic privileges are
both capable of being abstract. Abstract privileges are useful for
modeling privileges that otherwise would not be exposed via the
protocol. Abstract privileges also provide server implementations
with flexibility in implementing the privileges defined in this
specification. For example, if a server is incapable of separating
the read resource capability from the read ACL capability, it can
still model the DAV:read and DAV:read-acl privileges defined in this
specification by declaring them abstract, and containing them within
a non-abstract aggregate privilege (say, read-all) that holds
DAV:read, and DAV:read-acl. In this way, it is possible to set the
aggregate privilege, read-all, thus coupling the setting of DAV:read
and DAV:read-acl, but it is not possible to set DAV:read, or
DAV:read-acl individually. Since aggregate privileges can be
abstract, it is also possible to use abstract privileges to group
and classify non-abstract privileges.
The set of privileges that apply to a particular resource may vary
with the DAV:resourcetype of the resource, as well as between
different server implementations. To promote interoperability,
however, WebDAV defines a set of well-known privileges (e.g.
DAV:read and DAV:write), which can at least be used to classify the
other privileges defined on a particular resource.
3.1 DAV:read Privilege 3.1 DAV:read Privilege
The read privilege controls methods that return information The read privilege controls methods that return information about
about the state of the resource, including the resource's the state of the resource, including the resource's properties.
properties. Affected methods include GET and PROPFIND. The Affected methods include GET and PROPFIND. Additionally, the read
read privilege does not control the OPTIONS method since the privilege MAY control the OPTIONS method.
OPTIONS method returns capabilities rather than state.
<!ELEMENT read EMPTY>
Clemm, Hopkins, Sedlar, Whitehead [Page 5]
3.2 DAV:write Privilege 3.2 DAV:write Privilege
The write privilege controls methods that modify the state of The write privilege controls methods that modify the state of the
the resource, such as PUT and PROPPATCH. Note that state resource, such as PUT and PROPPATCH. Note that state modification
modification is also controlled via locking (see section 5.3
of [WEBDAV]), so effective write access requires that both Clemm, Hopkins, Sedlar, Whitehead [Page 6]
write privileges and write locking requirements are satisfied. is also controlled via locking (see section 5.3 of [WEBDAV]), so
effective write access requires that both write privileges and write
locking requirements are satisfied.
<!ELEMENT write EMPTY>
3.3 DAV:read-acl Privilege 3.3 DAV:read-acl Privilege
The DAV:read-acl privilege controls the use of PROPFIND to The DAV:read-acl privilege controls the use of PROPFIND to retrieve
retrieve the DAV:acl, and DAV:current-user-privilege-set the DAV:acl, and DAV:current-user-privilege-set properties of the
properties of the resource. resource.
<!ELEMENT read-acl EMPTY>
3.4 DAV:write-acl Privilege 3.4 DAV:write-acl Privilege
The DAV:write-acl privilege controls use of the ACL method to The DAV:write-acl privilege controls use of the ACL method to modify
modify the DAV:acl property of the resource. the DAV:acl property of the resource.
<!ELEMENT write-acl EMPTY>
3.5 DAV:all Privilege 3.5 DAV:all Privilege
The DAV:all privilege controls all privileges on the resource. DAV:all is an aggregate privilege that contains all privileges on
the resource.
<!ELEMENT all EMPTY>
4 PRINCIPAL PROPERTIES 4 PRINCIPAL PROPERTIES
Principals are manifested to clients as an HTTP resource, Principals are manifested to clients as an HTTP resource, identified
identified by a URL. A principal MUST have a DAV:displayname by a URL. A principal MUST have a DAV:displayname property. This
property. This protocol defines the following additional protocol defines the following additional properties for a
properties for a principal. principal.
4.1 DAV:is-principal 4.1 DAV:is-principal
This property indicates whether this resource is a principal. This property indicates whether this resource is a principal. A
A resource MUST have a non-empty DAV:is-principal property if resource MUST have a non-empty DAV:is-principal property if and only
and only if it is a principal resource. (Note: If we can if it is a principal resource. (Note: If we can just add a
just add a DAV:principal element to the DAV:resourcetype DAV:principal element to the DAV:resourcetype property, then we do
property, then we do not need a DAV:is-principal property.) 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: any non-empty value ("T" is suggested)
4.2 DAV:authentication-id 4.2 DAV:authentication-id
A property containing the name used to authenticate this A property containing the name used to authenticate this principal
principal (typically typed into a login prompt/dialog). (typically typed into a login prompt/dialog).
<!ELEMENT authentication-id (#PCDATA)> <!ELEMENT authentication-id (#PCDATA)>
PCDATA value: any string PCDATA value: any string
Clemm, Hopkins, Sedlar, Whitehead [Page 6] Clemm, Hopkins, Sedlar, Whitehead [Page 7]
5 ACCESS CONTROL PROPERTIES 5 ACCESS CONTROL PROPERTIES
This specification defines a number of new properties for This specification defines a number of new properties for WebDAV
WebDAV resources. Access control properties may be retrieved resources. Access control properties may be retrieved just like
just like other WebDAV properties, using the PROPFIND method. other WebDAV properties, using the PROPFIND method. Some access
Some access control properties (such as DAV:owner) MAY be control properties (such as DAV:owner) MAY be updated with the
updated with the PROPPATCH method. PROPPATCH method.
HTTP resources that support the WebDAV Access Control Protocol HTTP resources that support the WebDAV Access Control Protocol MUST
MUST contain the following properties: contain the following properties:
5.1 DAV:owner 5.1 DAV:owner
This property identifies a particular principal as being the This property identifies a particular principal as being the "owner"
"owner" of the resource. of the resource.
<!ELEMENT owner (href prop?)> <!ELEMENT owner (href prop?)>
<!ELEMENT prop (see [RFC2518], section 12.11)> <!ELEMENT prop (see [RFC2518], section 12.11)>
An implementation MAY include a list of selected properties of An implementation MAY include a list of selected properties of that
that principal resource. Which properties (if any) are principal resource. Which properties (if any) are included is
included is implementation defined. An implementation MAY implementation defined. An implementation MAY allow the use of
allow the use of PROPPATCH to update the DAV:owner field. PROPPATCH to update the DAV:owner field.
5.2 DAV:supported-privilege-set 5.2 DAV:supported-privilege-set
This is a read-only property that identifies the privileges This is a read-only property that identifies the privileges defined
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 Each privilege appears as an XML element, where aggregate privileges
privileges list as sub-elements all of the privileges that list as sub-elements all of the privileges that they aggregate.
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 is used to classify the non-abstract An abstract privilege of a resource MUST NOT be used in an ACE for
privilege elements. An abstract privilege of a resource MUST that resource. Servers MUST fail an attempt to set an abstract
NOT be used in an ACE for that resource. Servers MUST fail an privilege.
attempt to set an abstract privilege.
<!ELEMENT abstract EMPTY> <!ELEMENT abstract EMPTY>
A description is a human-readable description of what this A description is a human-readable description of what this privilege
privilege controls access to. controls access to.
<!ELEMENT description #PCDATA> <!ELEMENT description #PCDATA>
It is envisioned that a WebDAV ACL-aware administrative client It is envisioned that a WebDAV ACL-aware administrative client would
would list the supported privileges in a dialog box, and allow list the supported privileges in a dialog box, and allow the user to
the user to choose non-abstract privileges to apply in an ACE. choose non-abstract privileges to apply in an ACE. The privileges
The privileges tree is useful programmatically to map well- tree is useful programmatically to map well-known privileges
(defined by WebDAV or other standards groups) into privileges that
are supported by any particular server implementation. The
Clemm, Hopkins, Sedlar, Whitehead [Page 7] Clemm, Hopkins, Sedlar, Whitehead [Page 8]
known privileges (defined by WebDAV or other standards groups) privilege tree also serves to hide complexity in implementations
into 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 aggregates to the user.
complexity 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
This is a read-only property containing a list of privileges DAV:current-user-privilege-set is a read-only property containing
granted to the currently authenticated HTTP user. The current the exact set of privileges (as computed by the server) granted to
user has no access privileges to an object protected by an ACL the currently authenticated HTTP user. A user-agent can use the
unless that user matches one or more of the principals value of this property to adjust its user interface to make actions
specified in the ACEs. inaccessible (e.g, by graying out a menu item or button) for which
the current principal does not have permission. This is particularly
useful for an access control user interface, which can be
constructed without knowing the ACE combining semantics of the
server. This property is also useful for determine what operations
can be performed by the current principal, without having to
actually execute an operation.
<!ELEMENT current-user-privilege-set (privilege*)> <!ELEMENT current-user-privilege-set (privilege*)>
<!ELEMENT privilege ANY> <!ELEMENT privilege ANY>
Each element in the DAV:current-user-privilege-set property If the current user is granted a specific privilege, that privilege
MUST identify a privilege from the DAV:supported-privilege-set must belong to the set of privileges that may be set on this
property. resource. Therefore, each element in the DAV:current-user-privilege-
set property MUST identify a privilege from the DAV:supported-
privilege-set property.
5.4 DAV:acl 5.4 DAV:acl
This property specifies the list of access control entries This property specifies the list of access control entries (ACEs),
(ACEs), which define what principals are to get what which define what principals are to get what privileges for this
privileges for this resource. resource.
<!ELEMENT acl (ace*)> <!ELEMENT acl (ace*)>
Each DAV:ace element specifies the set of privileges to be Each DAV:ace element specifies the set of privileges to be either
either granted or denied to a single principal. If the granted or denied to a single principal. If the DAV:acl property is
DAV:acl property is empty, no principal is granted any empty, no principal is granted any privilege.
privilege.
<!ELEMENT ace (principal, (grant|deny), protected?, <!ELEMENT ace (principal, (grant|deny), protected?, inherited?)>
inherited?)>
An attempt to update the DAV:acl property with a PROPPATCH An attempt to update the DAV:acl property with a PROPPATCH MUST
MUST fail. fail.
5.4.1 ACE Principal 5.4.1 ACE Principal
The DAV:principal element identifies the principal to which The DAV:principal element identifies the principal to which this ACE
this ACE applies. 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 The current user matches DAV:href only if that user is authenticated
authenticated as being (or being a member of) the principal as being (or being a member of) the principal identified by the URL
identified by the URL contained by that DAV:href. An
implementation MAY include a DAV:prop element after the
DAV:href element, containing a list of selected properties of
that principal resource. Which properties (if any) are
Clemm, Hopkins, Sedlar, Whitehead [Page 8] Clemm, Hopkins, Sedlar, Whitehead [Page 9]
included in the DAV:prop element is implementation defined. contained by that DAV:href. An implementation MAY include a
The DAV:prop element is primarily intended for implementations DAV:prop element after the DAV:href element, containing a list of
that do not support PROPFIND requests on the principal URL. selected properties of that principal resource. Which properties
(if any) are included in the DAV:prop element is implementation
defined. The DAV:prop element is primarily intended for
implementations that do not support PROPFIND requests on the
principal URL.
<!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 The current user matches DAV:authenticated only if authenticated.
authenticated.
<!ELEMENT authenticated EMPTY> <!ELEMENT authenticated EMPTY>
The current user matches DAV:unauthenticated only if not The current user matches DAV:unauthenticated only if not
authenticated. authenticated.
<!ELEMENT unauthenticated EMPTY> <!ELEMENT unauthenticated EMPTY>
DAV:all is the union of DAV:authenticated, and DAV:all is the union of DAV:authenticated, and DAV:unauthenticated.
DAV:unauthenticated. For a given request, the user matches For a given request, the user matches either DAV:authenticated, or
either DAV:authenticated, or DAV:unauthenticated, but not DAV:unauthenticated, but not both.
both.
The current user matches a DAV:property principal in a DAV:acl The current user matches a DAV:property principal in a DAV:acl
property of a resource only if the identified property of that property of a resource only if the identified property of that
resource contains a DAV:href that identifies a principal, and resource contains a DAV:href that identifies a principal, and the
the current user is authenticated as being (or being a member current user is authenticated as being (or being a member of) that
of) that principal. For example, if the DAV:property element principal. For example, if the DAV:property element contained
contained <DAV:owner/>, the current user would match the <DAV:owner/>, the current user would match the DAV:property
DAV:property principal only if the current user is principal only if the current user is authenticated as matching the
authenticated as matching the principal identified by the principal identified by the DAV:owner property of the resource.
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 resource only if that resource is a principal object and the current
current user is authenticated as being that principal. user is authenticated as being that principal.
<!ELEMENT self EMPTY> <!ELEMENT self EMPTY>
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 Each DAV:grant or DAV:deny element specifies the set of privileges
privileges to be either granted or denied to the specified to be either granted or denied to the specified principal. A
principal. A DAV:grant or DAV:deny element of the DAV:acl of DAV:grant or DAV:deny element of the DAV:acl of a resource MUST only
a resource MUST only contain elements specified in the contain elements specified in the DAV:supported-privilege-set of
DAV:supported-privilege-set of that resource. that resource.
<!ELEMENT grant (privilege+)> <!ELEMENT grant (privilege+)>
<!ELEMENT deny (privilege+)> <!ELEMENT deny (privilege+)>
<!ELEMENT privilege ANY> <!ELEMENT privilege ANY>
Clemm, Hopkins, Sedlar, Whitehead [Page 9] Clemm, Hopkins, Sedlar, Whitehead [Page 10]
5.4.3 ACE Protection 5.4.3 ACE Protection
If an ACE contains a DAV:protected element, an ACL request If an ACE contains a DAV:protected element, an ACL request without
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 The presence of a DAV:inherited element indicates that this ACE is
ACE is inherited from another resource that is identified by inherited from another resource that is identified by the URL
the URL contained in a DAV:href element. An inherited ACE contained in a DAV:href element. An inherited ACE cannot be
cannot be modified directly, but instead the ACL on the modified directly, but instead the ACL on the resource from which it
resource from which it is inherited must be modified. is inherited must be modified.
Note that ACE inheritance is not the same as ACL Note that ACE inheritance is not the same as ACL initialization.
initialization. ACL initialization defines the ACL that a ACL initialization defines the ACL that a newly created resource
newly created resource will use (if not specified). ACE will use (if not specified). ACE inheritance refers to an ACE that
inheritance refers to an ACE that is logically shared - where is logically shared - where an update to the resource containing an
an update to the resource containing an ACE will affect the ACE will affect the ACE of each resource that inherits that ACE.
ACE of each resource that inherits that ACE. The method by The method by which ACLs are initialized or by which ACEs are
which ACLs are initialized or by which ACEs are inherited is inherited is not defined by this document.
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. This is a read-only property that defines the ACL semantics. These
These semantics define how multiple ACEs that match the semantics define how multiple ACEs that match the current user are
current user are combined, what are the constraints on how combined, what are the constraints on how ACEs can be ordered, and
ACEs can be ordered, and which principals must have an ACE. which principals must have an ACE.
Since it is not practical to require all implementations to Since it is not practical to require all implementations to use the
use the same ACL semantics, the DAV:acl-semantics property is same ACL semantics, the DAV:acl-semantics property is used to
used to identify the ACL semantics for a particular resource. identify the ACL semantics for a particular resource. The DAV:acl-
The DAV:acl-semantics element is defined in section 6. semantics element is defined in section 6.
5.6 DAV:principal-collection-set 5.6 DAV:principal-collection-set
Often a versioning implementation constrains where a principal This read-only property contains zero, one, or more URLs that
can be located in the URL space. The DAV:principal- identify a collection principal. It is expected that implementations
collection-set enumerates which collections may contain of this protocol will typically employ a relatively small number of
principals. locations in the URL namespace for principal, and collection
principals. In cases where this assumption holds, the DAV:principal-
collection-set property will contain a small set of URLs identifying
the top of collection hierarchy containing multiple principals and
collection principals. An access control protocol user agent could
use the contents of DAV:principal-collection-set to, for example,
query the DAV:displayname property (specified in Section 13.2 of
[RFC2518]) of all principals on that server, thereby yielding human-
readable names for each principal that could be displayed in a user
interface.
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 namespace, different resources on the same host MAY have different
different DAV:principal-collection-set values . The DAV:principal-collection-set values. The collections specified in
collections specified in the DAV:principal-collection-set MAY the DAV:principal-collection-set MAY be located on different hosts
be located on different hosts from the resource. from the resource. The URLs in DAV:principal-collection-set are not
limited to http scheme URLs, and can, for example, be ldap scheme
URLs. For security and scalability reasons, a server MAY report only
a subset of the entire set of known collection principals, and
therefore clients should not assume they have retrieved an
exhaustive listing. Additionally, a server MAY elect to report none
of the collection principals it knows about.
Clemm, Hopkins, Sedlar, Whitehead [Page 10]
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 The following example shows how access control information can be
be retrieved by using the PROPFIND method to fetch the values retrieved by using the PROPFIND method to fetch the values of the
of the DAV:owner, DAV:supported-privilege-set, DAV:current- DAV:owner, DAV:supported-privilege-set, DAV:current-user-privilege-
user-privilege-set, and DAV:acl properties. set, and DAV:acl properties.
>> Request << >> Request <<
PROPFIND /top/container/ HTTP/1.1 PROPFIND /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: xxx Content-Length: xxx
Depth: 0 Depth: 0
Authorization: Digest username="ejw", Authorization: Digest username="ejw",
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" ?>
<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>
>> 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.acl.org/"> <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>
<D:privilege> <D:write/> </D:privilege> <D:privilege> <D:write/> </D:privilege>
<D:abstract/> <D:abstract/>
<D:description>Write any object</D:description> <D:description>Write any object</D:description>
<D:supported-privilege> <D:supported-privilege>
<D:privilege> <A:create/> </D:privilege> <D:privilege> <A:create/> </D:privilege>
Clemm, Hopkins, Sedlar, Whitehead [Page 11]
<D:description>Create an object</D:description> <D:description>Create an object</D:description>
</D:supported-privilege> </D:supported-privilege>
<D:supported-privilege> <D:supported-privilege>
<D:privilege> <A:update> </D:privilege> <D:privilege> <A:update/> </D:privilege>
<D:description>Update an object</D:description> <D:description>Update an object</D:description>
</D:supported-privilege> </D:supported-privilege>
<D:supported-privilege> <D:supported-privilege>
<D:privilege> <A:delete> </D:privilege> <D:privilege> <A:delete/> </D:privilege>
<D:description>Delete an object</D:description> <D:description>Delete an object</D:description>
</D:supported-privilege> </D:supported-privilege>
</D:supported-privilege> </D:supported-privilege>
<D:supported-privilege> <D:supported-privilege>
<D:privilege> <D:read-acl/> </D:privilege> <D:privilege> <D:read-acl/> </D:privilege>
<D:description>Read the ACL</D:privilege> <D:description>Read the ACL</D:description>
</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:privilege> <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>
</D:current-user-privilege-set> </D:current-user-privilege-set>
<D:acl> <D:acl>
<D:ace> <D:ace>
<D:principal> <D:principal>
skipping to change at line 646 skipping to change at page 27, line ?
<D:authentication-id>esedlar</D:authentication-id> <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>
<D:href>http://www.foo.org/groups/marketing/</d:href>
Clemm, Hopkins, Sedlar, Whitehead [Page 13]
<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>
<D:privilege> <D:write-acl/> </D:privilege></D:grant> <D:privilege> <D:write-acl/> </D:privilege></D:grant>
<D:ace/> </D:ace>
<D:ace> <D:ace>
Clemm, Hopkins, Sedlar, Whitehead [Page 12]
<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:inheritied> <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 The value of the DAV:owner property is a single DAV:href XML element
element containing the URL of the principal that owns this containing the URL of the principal that owns this resource.
resource.
The value of the DAV:supported-privilege-set property is a The value of the DAV:supported-privilege-set property is a tree of
tree of supported privileges: supported privileges:
DAV:acl (abstract) DAV:acl (aggregate, abstract)
| |
+-- DAV:read +-- DAV:read
+-- DAV:write (abstract) +-- DAV:write (aggregate, abstract)
| |
+-- http://www.acl.org/create +-- http://www.acl.org/create
+-- http://www.acl.org/update +-- http://www.acl.org/update
+-- http://www.acl.org/delete +-- http://www.acl.org/delete
+-- DAV:read-acl +-- DAV:read-acl
+-- DAV:write-acl +-- DAV:write-acl
The DAV:current-user-privilege-set property contains two The DAV:current-user-privilege-set property contains two privileges,
privileges, DAV:read, and DAV:read-acl. This indicates that DAV:read, and DAV:read-acl. This indicates that the current
the current authenticated user only has the ability to read authenticated user only has the ability to read the resource, and
the resource, and read the DAV:acl property on the resource. 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, http://www.foo.org/users/esedlar is granted the DAV:read, DAV:write,
DAV:write, and DAV:read-acl privileges. 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 privilege. In this example, the principal URL identifies a group,
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, specifically the DAV:owner property. When evaluating this ACE, the
the value of the DAV:owner property is retrieved, and is value of the DAV:owner property is retrieved, and is examined to see
examined to see if it contains a DAV:href XML element. If so, if it contains a DAV:href XML element. If so, the URL within the
the URL within the DAV:href element is read, and identifies a DAV:href element is read, and identifies a principal. In this ACE,
principal. In this ACE, the owner is granted DAV:read-acl, and the owner is granted DAV:read-acl, and DAV:write-acl privileges.
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.
Clemm, Hopkins, Sedlar, Whitehead [Page 13]
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 The ACL semantics define how multiple ACEs that match the current
current user are combined, what are the constraints on how user are combined, what are the constraints on how ACEs can be
ACEs can be ordered, and which principals must have an ACE. ordered, and which principals must have an ACE.
<!ELEMENT acl-semantics ANY> <!ELEMENT acl-semantics acl-sem*>
ANY value: zero or more of the ACL semantic elements
<!ELEMENT acl-sem (ace-combination, ace-ordering, required-
principal)>
6.1 ACE Combination 6.1 ACE Combination
The DAV:ace-combination element defines how privileges from The DAV:ace-combination element defines how privileges from multiple
multiple ACEs that match the current user will be combined to ACEs that match the current user will be combined to determine the
determine the access rights for that user. Multiple ACEs may access privileges for that user. Multiple ACEs may match the same
match the same user because the same principal can appear in user because the same principal can appear in multiple ACEs, because
multiple ACEs, because multiple principals can identify the multiple principals can identify the same user, and because one
same user, and because one principal can be a member of principal can be a member of another principal.
another principal.
<!ELEMENT ace-combination <!ELEMENT ace-combination
(first-match | all-grant-before-any-deny | no-deny)> (first-match | all-grant-before-any-deny | no-deny)>
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 ACEs are evaluated in the order in which they appear in the ACL.
the ACL. If the first ACE that matches the current user does If the first ACE that matches the current user does not grant all
not grant all the privileges needed for the request, the the privileges needed for the request, the request MUST fail.
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 ACEs are evaluated in the order in which they appear in the ACL.
the ACL. If an evaluated ACE denies a privilege needed for If an evaluated ACE denies a privilege needed for the request, the
the request, the request MUST fail. If all ACEs have been request MUST fail. If all ACEs have been evaluated without the user
evaluated without the user being granted all privileges needed being granted all privileges needed for the request, the request
for the request, the request MUST fail. 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:no-deny ACE Combination
All ACEs in the ACL are evaluated. An "individual ACE" is one All ACEs in the ACL are evaluated. An "individual ACE" is one whose
whose principal identifies the current user. A "group ACE" is principal identifies the current user. A "group ACE" is one whose
one whose principal is a collection that contains a principal
that identifies the current user. A privilege is granted if Clemm, Hopkins, Sedlar, Whitehead [Page 15]
it is granted by an individual ACE and not denied by an principal is a collection that contains a principal that identifies
individual ACE, or if it is granted by a group ACE and not the current user. A privilege is granted if it is granted by an
denied by an individual or group ACE. A request MUST fail if individual ACE and not denied by an individual ACE, or if it is
any of its needed privileges are not granted. 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 no-deny EMPTY>
Clemm, Hopkins, Sedlar, Whitehead [Page 14]
6.2 ACE Ordering 6.2 ACE Ordering
The DAV:ace-ordering element defines a constraint on how the The DAV:ace-ordering element defines a constraint on how the ACEs
ACEs can be ordered in the ACL. can be ordered in the ACL.
<!ELEMENT ace-ordering (deny-before-grant)? >
6.2.1 DAV:deny-before-grant ACE Ordering 6.2.1 DAV:deny-before-grant ACE Ordering
This element indicates that all deny ACEs must precede all This element indicates that all deny ACEs must precede all grant
grant 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 The required principal elements identify which principals must have
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 For example, the following element requires that the ACE contain a
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 This section defines the impact of access control functionality on
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.
7.1.1 Example - OPTIONS 7.1.1 Example - 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
>>RESPONSE Clemm, Hopkins, Sedlar, Whitehead [Page 16]
>> RESPONSE <<
HTTP/1.1 200 OK HTTP/1.1 200 OK
DAV: 1, 2, access-control DAV: 1, 2, access-control
Clemm, Hopkins, Sedlar, Whitehead [Page 15]
Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL
In this example, the OPTIONS response indicates that the In this example, the OPTIONS response indicates that the server
server supports access control and that /foo.html can have its supports access control and that /foo.html can have its access
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 A DAV:acl property of a resource is modified by the ACL method. A
method. A new DAV:acl value must be written in its entirety, new DAV:acl value must be written in its entirety, including any
including any inherited ACEs. Unless the DAV:acl property of inherited ACEs. Unless the DAV:acl property of the resource can be
the resource can be updated to be exactly the value specified updated to be exactly the value specified in the ACL request, the
in the ACL request, the ACL request MUST fail. If a server ACL request MUST fail. If a server restricts the set of ACEs
restricts the set of ACEs visible to the current user via the visible to the current user via the DAV:acl property, then the ACL
DAV:acl property, then the ACL request would only replace the request would only replace the set of ACEs visible to the current
set of ACEs visible to the current user, and would not affect user, and would not affect any ACE that was not visible.
any ACE that was not visible.
In order to avoid overwriting DAV:acl changes by another In order to avoid overwriting DAV:acl changes by another client, a
client, a client SHOULD acquire a WebDAV lock on the resource client SHOULD acquire a WebDAV lock on the resource before
before retrieving the DAV:acl property of a resource that it retrieving the DAV:acl property of a resource that it intends on
intends on updating. updating.
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, constraints on an ACL request. If the constraint is violated, a 403
a 403 (Forbidden) response MUST be returned and the indicated (Forbidden) response MUST be returned and the indicated XML element
XML element MUST be returned in the response body. 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 DAV:write-acl privileges, and this cannot be changed by a client.
client.
<DAV:too-many-aces/>: An implementation MAY limit the number
of ACEs in an ACL. However, ACL-compliant servers MUST
support at least one ACE granting privileges to a single
principal, and one ACE granting privileges to a collection
principal.
<DAV:non-inherited-must-precede-inherited/>: All non-inherited <DAV:too-many-aces/>: An implementation MAY limit the number of ACEs
ACEs MUST precede all inherited ACEs. in an ACL. However, ACL-compliant servers MUST support at least one
ACE granting privileges to a single principal, and one ACE granting
privileges to a collection principal.
<DAV:deny-must-precede-grant/>: All non-inherited deny ACEs <DAV:non-inherited-must-precede-inherited/>: All non-inherited ACEs
MUST precede all non-inherited grant ACEs. MUST precede all inherited ACEs.
<DAV:acl-requires-lock-token/>: If a resource is locked, the <DAV:deny-must-precede-grant/>: All non-inherited deny ACEs MUST
lock token MUST be specified in the ACL request. precede all non-inherited grant ACEs.
Clemm, Hopkins, Sedlar, Whitehead [Page 16]
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
identified by the URL http://www.foo.org/users/esedlar (i.e.,
the user "esedlar") read and write privileges, grants the Clemm, Hopkins, Sedlar, Whitehead [Page 17]
owner of the resource read-acl and write-acl privileges, and identified by the URL http://www.foo.org/users/esedlar (i.e., the
grants everyone read privileges inherited from the parent user "esedlar") read and write privileges, grants the owner of the
collection http://www.foo.bar/top/. resource read-acl and write-acl privileges, and grants everyone read
privileges inherited from the parent collection
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="...",
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>
skipping to change at line 917 skipping to change at page 27, line ?
<D:grant> <D:grant>
<D:privilege> <D:read/> </D:privilege> <D:privilege> <D:read/> </D:privilege>
<D:privilege> <D:write/> </D:privilege> </D:grant> <D:privilege> <D:write/> </D:privilege> </D:grant>
</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>
<D:privilege> <D:write-acl/> </D:privilege> </D:grant> <D:privilege> <D:write-acl/> </D:privilege> </D:grant>
<D:ace/> </D:ace>
<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>
>> Response << >> Response <<
HTTP/1.1 200 OK HTTP/1.1 200 OK
8.1.3Example: ACL method failure 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 information in the Authorization header, attempts to grant the
principal identified by the URL principal identified by the URL http://www.foo.org/users/esedlar
http://www.foo.org/users/esedlar (i.e., the user "esedlar") (i.e., the user "esedlar") read privileges, but fails because an
read privileges, but fails because an implicit ACE has been protected ACE has been omitted (e.g. the ACE granting the DAV:owner
DAV:read-acl and DAV:write-acl privileges must always be present
Clemm, Hopkins, Sedlar, Whitehead [Page 17] since it is protected -- see Section 5.4.3).
omitted (e.g. the ACE granting the DAV:owner DAV:read-acl and
DAV:write-acl privileges).
Clemm, Hopkins, Sedlar, Whitehead [Page 18]
>> Request << >> Request <<
ACL /top/container HTTP/1.1 ACL /top/container/ HTTP/1.1
Host: www.foo.bar 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" ?>
<D:acl xmlns:D="DAV:"> <D:acl xmlns:D="DAV:">
<D:ace> <D:ace>
<D:principal> <D:principal>
<D:href>http://www.foo.bar/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>
>> 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:cannot-change-implicit-ace/> <DAV:protected/>
9 INTERNATIONALIZATION CONSIDERATIONS 8.1.4 Example: ACL method failure due to inherited ACEs preceding non-
inherited ACEs
In this specification, the only human-readable content can be In the following request, user "ejw", authenticated by information
found in the DAV:authentication-id property, found on in the Authorization header, tries to change the access control list
principal resources. This property contains the name used to on the resource http://www.foo.org/top/index.html. This resource has
authenticate a principal, typically by a user entering this two inherited ACEs.
name into a password entry screen. As a result, the
authentication-id must be capable of representing names in
multiple character sets. Since DAV:authentication-id is a
WebDAV property, it is represented on-the-wire as XML [REC-
XML], and hence can leverage XML's language tagging and
character set encoding capabilities. Specifically, XML
processors must, at minimum, be able to read XML elements
encoded using the UTF-8 [UTF-8] encoding of the ISO 10646
multilingual plane. XML examples in this specification
demonstrate use of the charset parameter of the Content-Type
header, as defined in [RFC2376], as well as the XML "encoding"
attribute, which together provide charset identification
information for MIME and XML processors.
For properties other than DAV:authentication-id, it is Inherited ACE #1 grants the principal identified by URL
expected that implementations will treat the property names http://www.foo.org/users/ejw (i.e., the user "ejw")
and values as tokens, and convert these tokens into human- http://www.foo.org/privs/write-all and DAV:read-acl privileges. On
this server, http://www.foo.org/privs/write-all is an aggregate
privilege containing DAV:write, and DAV:write-acl.
Clemm, Hopkins, Sedlar, Whitehead [Page 18] Inherited ACE #2 grants principal DAV:all the DAV:read privilege.
readable text in the user's language and character set when
displayed to a person. Only a generic WebDAV property display
utility would display these values in their raw form.
For error reporting, we follow the convention of HTTP/1.1 The request attempts to add a third ACE, granting the principal
status codes, including with each status code a short, English identified by the URL http://www.foo.org/users/gclemm (i.e., the
description of the code (e.g., 200 (OK)). While the user "gclemm") DAV:write permission, but in the request places the
possibility exists that a poorly crafted user agent would inherited ACEs before the non-inherited ACEs, causing an error on
display this message to a user, internationalized applications this specific server implementation. Note that on a different
will ignore this message, and display an appropriate message implementation, this request might be accepted.
in the user's language and character set.
Further internationalization considerations for this protocol >> Request <<
are described in the WebDAV Distributed Authoring protocol
specification [RFC2518]. Clemm, Hopkins, Sedlar, Whitehead [Page 19]
ACL /top/index.html HTTP/1.1
Host: www.foo.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Authorization: Digest username="ejw",
realm="users@foo.org", nonce="...",
uri="/top/index.html", response="...", opaque="..."
<?xml version="1.0" encoding="utf-8" ?>
<D:acl xmlns:D="DAV:" xmlns:F="http://www.foo.org/privs/">
<D:ace>
<D:principal>
<D:href>http://www.foo.org/users/ejw</D:href>
</D:principal>
<D:grant>
<D:privilege><F:write-all/></D:privilege>
<D:privilege><D:read-acl/></D:privilege>
</D:grant>
<D:inherited/>
</D:ace>
<D:ace>
<D:principal><D:all/></D:principal>
<D:grant><D:read/></D:grant>
<D:inherited/>
</D:ace>
<D:ace>
<D:principal>
<D:href>http://www.foo.org/users/gclemm</D:href>
</D:principal>
<D:grant><D:write/></D:grant>
</D:ace>
</D:acl>
>> Response <<
HTTP/1.1 403 Forbidden
Content-Type: text/xml; charset="utf-8"
Content-Length: xxx
<?xml version="1.0" encoding="utf-8" ?>
<DAV:non-inherited-must-precede-inherited/>
8.1.5 Example: ACL method failure due to an attempt to set grant and
deny in a single ACE.
In this example, user "ygoland", authenticated by information in the
Authorization header, tries to change the access control list on the
resource http://www.foo.org/diamond/engagement-ring.gif. The ACL
request includes a single, syntactically and semantically incorrect
ACE, which attempts to grant the collection principal identified by
the URL http://www.foo.org/users/friends/ DAV:read privilege and
deny the principal identified by URL
http://www.foo.org/users/ygoland-so (i.e., the user "ygoland-so")
DAV:read privilege. However, it is illegal to have multiple
Clemm, Hopkins, Sedlar, Whitehead [Page 20]
principal elements, as well as both a grant and deny element in the
same ACE, so the request fails due to poor syntax.
>> Request <<
ACL /diamond/engagement-ring.gif HTTP/1.1
Host: www.foo.org
Content-Type: text/xml; charset="utf-8"
Content-Length: xxxx
Authorization: Digest username="ygoland",
realm="users@foo.org", nonce="...",
uri="/diamond/engagement-ring.gif", response="...",
opaque="..."
<?xml version="1.0" encoding="utf-8" ?>
<D:acl xmlns:D="DAV:">
<D:ace>
<D:principal>
<D:href>http://www.foo.org/users/friends/</D:href>
</D:principal>
<D:grant><D:read/></D:grant>
<D:principal>
<D:href>http://www.foo.org/users/ygoland-so</D:href>
</D:principal>
<D:deny><D:read/></D:deny>
</D:ace>
</D:acl>
>> Response <<
HTTP/1.1 400 Bad Request
Content-Length: 0
Note that if the request had been divided into two ACEs, one to
grant, and one to deny, the request would have been syntactically
well formed.
9 INTERNATIONALIZATION CONSIDERATIONS
In this specification, the only human-readable content can be found
in the DAV:authentication-id property, found on principal resources.
This property contains the name used to authenticate a principal,
typically by a user entering this name into a password entry screen.
As a result, the authentication-id must be capable of representing
names in multiple character sets. Since DAV:authentication-id is a
WebDAV property, it is represented on-the-wire as XML [REC-XML], and
hence can leverage XML's language tagging and character set encoding
capabilities. Specifically, XML processors must, at minimum, be able
to read XML elements encoded using the UTF-8 [UTF-8] encoding of the
ISO 10646 multilingual plane. XML examples in this specification
demonstrate use of the charset parameter of the Content-Type header,
as defined in [RFC3023], as well as the XML "encoding" attribute,
which together provide charset identification information for MIME
and XML processors.
Clemm, Hopkins, Sedlar, Whitehead [Page 21]
For properties other than DAV:authentication-id, it is expected that
implementations will treat the property names and values as tokens,
and convert these tokens into human-readable text in the user's
language and character set when displayed to a person. Only a
generic WebDAV property display utility would display these values
in their raw form.
For error reporting, we follow the convention of HTTP/1.1 status
codes, including with each status code a short, English description
of the code (e.g., 200 (OK)). While the possibility exists that a
poorly crafted user agent would display this message to a user,
internationalized applications will ignore this message, and display
an appropriate message in the user's language and character set.
Further internationalization considerations for this protocol are
described in the WebDAV Distributed Authoring protocol specification
[RFC2518].
10 SECURITY CONSIDERATIONS 10 SECURITY CONSIDERATIONS
Applications and users of this access control protocol should Applications and users of this access control protocol should be
be aware of several security considerations, detailed below. aware of several security considerations, detailed below. In
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 considerations detailed in the HTTP/1.1 specification [RFC2616], the
[RFC2616], the WebDAV Distributed Authoring Protocol WebDAV Distributed Authoring Protocol specification [RFC2518], and
specification [RFC2518], and the XML specification (discussed the XML Media Types specification [RFC3023] should be considered in
in [RFC2376]) should be considered in a security analysis of a security analysis of this protocol.
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 specifications, if a single user's authentication
credentials are compromised, only those resources for which credentials are compromised, only those resources for which the user
the user has access permission can be read, modified, moved, has access permission can be read, modified, moved, or deleted. With
or deleted. With the introduction of this access control the introduction of this access control protocol, if a single
protocol, if a single compromised user has the ability to compromised user has the ability to change ACLs for a broad range of
change ACLs for a broad range of other users (e.g., a super- other users (e.g., a super-user), the number of resources that could
user), the number of resources that could be altered by a be altered by a single compromised user increases. This risk can be
single compromised user increases. This risk can be mitigated mitigated by limiting the number of people who have write-acl
by limiting the number of people who have write-acl privileges privileges across a broad range of resources.
across a broad range of resources.
10.2 Authentication-id Property and Dictionary Attacks 10.2 Authentication-id Property and Dictionary Attacks
Every principal has a DAV:authentication-id property defined Every principal has a DAV:authentication-id property defined on it,
on it, which provides the name used to authenticate this which provides the name used to authenticate this principal,
principal, typically the username portion of a typically the username portion of a username/password authentication
username/password authentication scheme. An attacker can use scheme. An attacker can use the information in this property when
the information in this property when attempting either a attempting either a brute-force, or a dictionary attack to guess the
brute-force, or a dictionary attack to guess the principal's principal's identifying password. By providing the username in
identifying password. By providing the username in DAV:authentication-id, the scope of an attack can be reduced to a
DAV:authentication-id, the scope of an attack can be reduced single, valid username. Furthermore, it is possible that principals
to a single, valid username. Furthermore, it is possible that can potentially belong to a collection. In this case, it is possible
principals can potentially belong to a collection. In this to use the PROPFIND method to retrieve the DAV:authentication-id
property from all of the principals in a collection, thus providing
Clemm, Hopkins, Sedlar, Whitehead [Page 19] multiple usernames that can be the focus of attack.
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.
To reduce this risk, the DAV:authentication-id property should Clemm, Hopkins, Sedlar, Whitehead [Page 22]
not be world-readable. Which principals are granted default To reduce this risk, the DAV:authentication-id property should not
read permission for DAV:authentication-id should be carefully be world-readable. Which principals are granted default read
considered in any deployment of this protocol. privilege for DAV:authentication-id should be carefully considered
in any deployment of this protocol.
10.3 Risks of the read-acl Privilege 10.3 Risks of the read-acl Privilege
The ability to read the access permissions (stored in the The ability to read the access privileges (stored in the DAV:acl
DAV:acl property), or the privileges permitted the currently property), or the privileges permitted the currently authenticated
authenticated user (stored in the DAV:current-user-privilege- user (stored in the DAV:current-user-privilege-set property) on a
set property) on a resource may seem innocuous, since reading resource may seem innocuous, since reading an ACL cannot possibly
an ACL cannot possibly affect the resource's state. However, affect the resource's state. However, if all resources have world-
if all resources have world-readable ACLs, it is possible to readable ACLs, it is possible to perform an exhaustive search for
perform an exhaustive search for those resources that have those resources that have inadvertently left themselves in a
inadvertently left themselves in a vulnerable state, such as vulnerable state, such as being world-writeable. In particular, the
being world-writeable. Once found, this vulnerability can be property retrieval method PROPFIND, executed with Depth infinity on
exploited by a denial of service attack in which the open an entire hierarchy, is a very efficient way to retrieve the DAV:acl
resource is repeatedly overwritten. Alternately, writeable or DAV:current-user-privilege-set properties. Once found, this
resources can be modified in undesirable ways. vulnerability can be exploited by a denial of service attack in
which the open resource is repeatedly overwritten. Alternately,
writeable resources can be modified in undesirable ways.
To reduce this risk, read-acl privileges should not be granted To reduce this risk, read-acl privileges should not be granted to
to unauthenticated principals, and restrictions on read-acl unauthenticated principals, and restrictions on read-acl privileges
privileges for authenticated principals should be carefully for authenticated principals should be carefully analyzed when
analysed when deploying this protocol. deploying this protocol.
11 AUTHENTICATION 11 AUTHENTICATION
Authentication mechanisms defined in WebDAV will also apply to Authentication mechanisms defined in WebDAV also apply to this
WebDAV ACL. WebDAV Access Control Protocol, in particular the Basic and Digest
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 elements. All other IANA considerations mentioned in [RFC2518] also
[RFC2518] also applicable to WebDAV ACL. applicable to WebDAV ACL.
13 INTELLECTUAL PROPERTY 13 INTELLECTUAL PROPERTY
The following notice is copied from RFC 2026, section 10.4, The following notice is copied from RFC 2026, section 10.4, and
and describes the position of the IETF concerning intellectual describes the position of the IETF concerning intellectual property
property claims made against this document. claims made against this document.
The IETF takes no position regarding the validity or scope of The IETF takes no position regarding the validity or scope of any
any intellectual property or other rights that might be intellectual property or other rights that might be claimed to
claimed to pertain to the implementation or use other pertain to the implementation or use other technology described in
technology described in this document or the extent to which this document or the extent to which any license under such rights
any license under such rights might or might not be available; might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances
of licenses to be made available, or the result of an attempt made
Clemm, Hopkins, Sedlar, Whitehead [Page 20] Clemm, Hopkins, Sedlar, Whitehead [Page 23]
neither does it represent that it has made any effort to to obtain a general license or permission for the use of such
identify any such rights. Information on the IETF's proprietary rights by implementers or users of this specification
procedures with respect to rights in standards-track and can be obtained from the IETF Secretariat.
standards-related documentation can be found in BCP-11.
Copies of claims of rights made available for publication and
any assurances of licenses to be made available, or the result
of an attempt made to obtain a general license or permission
for the use of such proprietary rights by implementers or
users of this specification can be obtained from the IETF
Secretariat.
The IETF invites any interested party to bring to its The IETF invites any interested party to bring to its attention any
attention any copyrights, patents or patent applications, or copyrights, patents or patent applications, or other proprietary
other proprietary rights that may cover technology that may be rights that may cover technology that may be required to practice
required to practice this standard. Please address the this standard. Please address the information to the IETF Executive
information to the IETF Executive Director. Director.
14 ACKNOWLEDGEMENTS 14 ACKNOWLEDGEMENTS
This protocol is the collaborative product of the WebDAV ACL This protocol is the collaborative product of the WebDAV ACL design
design team: Bernard Chester, Geoff Clemm (Rational), Anne team: Bernard Chester, Geoff Clemm (Rational), Anne Hopkins
Hopkins (Microsoft), Barry Lind (Xythos), Sean Lyndersay (Microsoft), Barry Lind (Xythos), Sean Lyndersay (Microsoft), Eric
(Microsoft), Eric Sedlar (Oracle), Greg Stein (Apache.org), Sedlar (Oracle), Greg Stein (Apache.org), and Jim Whitehead (UC
and Jim Whitehead (UC Santa Cruz). Prior work on WebDAV access Santa Cruz). The authors are grateful for the detailed review and
control protocols has been performed by Yaron Goland, Paul comments provided by Jim Amsden, Gino Basso, Murthy Chintalapati,
Leach, Lisa Dusseault, Howard Palmer, and Jon Radoff. We would Dennis Hamilton, Ron Jacobs, Chris Knight, and Remy Maucherat. Prior
like to acknowledge the foundation laid for us by the authors work on WebDAV access control protocols has been performed by Yaron
of the WebDAV and HTTP protocols upon which this protocol is Goland, Paul Leach, Lisa Dusseault, Howard Palmer, and Jon Radoff.
layered, and the invaluable feedback from the WebDAV working We would like to acknowledge the foundation laid for us by the
group. authors of the WebDAV and HTTP protocols upon 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, [REC-XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible
"Extensible Markup Language (XML)." World Wide Web Consortium Markup Language (XML)." World Wide Web Consortium Recommendation
Recommendation REC-xml-19980210. http://www.w3.org/TR/REC-xml- REC-xml-19980210. http://www.w3.org/TR/REC-xml-19980210.
19980210.[RFC2616] R. Fielding, J. Gettys, J. C. Mogul, H.
Frystyk, L. Masinter, P. Leach, and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1." RFC 2616. U.C.Irvine, Compaq,
Xerox, Microsoft, MIT/LCS, June, 1999.
[RFC2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. [RFC2616] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, L.
Lawrence, P. Leach, A. Luotonen, L. Stewart, "HTTP Masinter, P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol
Authentication: Basic and Digest Access Authentication. " RFC -- HTTP/1.1." RFC 2616. U.C.Irvine, Compaq, Xerox, Microsoft,
2617. Northwestern University, Verisign, AbiSource, Agranat, MIT/LCS, June, 1999.
Microsoft, Netscape, Open Market, June, 1999.
[RFC2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, P.
Leach, A. Luotonen, L. Stewart, "HTTP Authentication: Basic and
Digest Access Authentication. " RFC 2617. Northwestern University,
Verisign, AbiSource, Agranat, Microsoft, Netscape, Open Market,
June, 1999.
Clemm, Hopkins, Sedlar, Whitehead [Page 21]
[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." Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV." RFC
RFC 2518. Microsoft, U.C.Irvine, Netscape, Novell, February, 2518. Microsoft, U.C.Irvine, Netscape, Novell, February, 1999.
1999.
[UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode [RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types." RFC
and ISO 10646." RFC 2279. Alis Technologies. January, 1998. 3023. IBM Tokyo Research Laboratory, simonstl.com, Skymoon Ventures,
January, 2001.
15.2 Informational References Clemm, Hopkins, Sedlar, Whitehead [Page 24]
[UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode and
ISO 10646." RFC 2279. Alis Technologies. January, 1998.
[RFC2026] S.Bradner, "The Internet Standards Process _ 15.2Informational References
Revision 3." RFC 2026, BCP 9. Harvard, October, 1996.
[RFC2396] E. Whitehead, M. Murata, "XML Media Types." RFC [RFC2026] S.Bradner, "The Internet Standards Process û Revision 3."
2376. U.C. Irvine, Fuji Xerox Info. Systems. July, 1998. (This RFC 2026, BCP 9. Harvard, October, 1996.
RFC will soon be superseded by <draft-murata-xml-09.txt>,
which has been approved by the IESG as a Proposed Standard,
but not yet issued as an RFC.)
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
Anne Hopkins Anne Hopkins
skipping to change at line 1206 skipping to change at page 27, line ?
Email: esedlar@us.oracle.com Email: esedlar@us.oracle.com
Jim Whitehead Jim Whitehead
U.C. Santa Cruz U.C. Santa Cruz
Dept. of Computer Science Dept. of Computer Science
Baskin Engineering Baskin Engineering
1156 High Street 1156 High Street
Santa Cruz, CA 95064 Santa Cruz, CA 95064
Email: ejw@cse.ucsc.edu Email: ejw@cse.ucsc.edu
17 STILL TO DO 17 APPENDICIES
* If we can add more elements to DAV:resourcetype, we can 17.1XML Document Type Definition
eliminate DAV:is-principal.
Clemm, Hopkins, Sedlar, Whitehead [Page 22] <!-- Privileges -->
* Add back the XML schema if provides info not in the DTD's.
* Consider adding a DAV:matching-principals, which identifies <!ELEMENT read EMPTY>
all ACL principals that match the current user. <!ELEMENT write EMPTY>
<!ELEMENT read-acl EMPTY>
<!ELEMENT write-acl EMPTY>
<!ELEMENT all EMPTY>
* Add DAV:ordering-constraints, DAV:required-principals, and <!-- Principal Properties (Section 4) -->
DAV:ace-combination-semantics as sub-elements of DAV:acl-
semantics.
Clemm, Hopkins, Sedlar, Whitehead [Page 23] Clemm, Hopkins, Sedlar, Whitehead [Page 25]
<!ELEMENT is-principal (#PCDATA)>
<!ELEMENT authentication-id (#PCDATA)>
<!-- Access Control Properties (Section 5) -->
<!-- DAV:owner Property (Section 5.1) -->
<!ELEMENT owner (href prop?)>
<!ELEMENT prop (see [RFC2518], section 12.11)>
<!-- DAV:supported-privilege-set Property (Section 5.2) -->
<!ELEMENT supported-privilege-set (supported-privilege*)>
<!ELEMENT supported-privilege
(privilege, abstract?, description, supported-privilege*)>
<!ELEMENT privilege ANY>
<!ELEMENT abstract EMPTY>
<!ELEMENT description #PCDATA>
<!ELEMENT privilege ANY>
<!-- DAV:current-user-privilege-set Property (Section 5.3) -->
<!ELEMENT current-user-privilege-set (privilege*)>
<!-- DAV:acl Property (Section 5.4) -->
<!ELEMENT acl (ace*)>
<!ELEMENT ace (principal, (grant|deny), protected?, inherited?)>
<!ELEMENT principal ((href, prop?)
| all | authenticated | unauthenticated
| property | self)>
<!ELEMENT prop (see [RFC2518], section 12.11)>
<!ELEMENT all EMPTY>
<!ELEMENT authenticated EMPTY>
<!ELEMENT unauthenticated EMPTY>
<!ELEMENT property ANY>
<!ELEMENT self EMPTY>
<!ELEMENT grant (privilege+)>
<!ELEMENT deny (privilege+)>
<!ELEMENT privilege ANY>
<!ELEMENT protected EMPTY>
<!ELEMENT inherited (href)>
<!-- DAV:principal-collection-set Property (Section 5.6) -->
Clemm, Hopkins, Sedlar, Whitehead [Page 26]
<!ELEMENT principal-collection-set (href*)>
<!-- DAV:acl-semantics Property (Section 6) -->
<!ELEMENT acl-semantics acl-sem*>
<!ELEMENT acl-sem (ace-combination, ace-ordering, required-
principal)>
<!ELEMENT ace-combination
(first-match | all-grant-before-any-deny | no-deny)>
<!ELEMENT first-match EMPTY>
<!ELEMENT all-grant-before-any-deny EMPTY>
<!ELEMENT no-deny EMPTY>
<!ELEMENT ace-ordering (deny-before-grant)? >
<!ELEMENT deny-before-grant EMPTY>
<!ELEMENT required-principal
(href | all | authenticated | unauthenticated | property |
self)>
<!-- ACL method preconditions (Section 8.1.1) -->
<!ELEMENT protected EMPTY>
<!ELEMENT too-many-aces EMPTY>
<!ELEMENT non-inherited-must-precede-inherited EMPTY>
<!ELEMENT deny-must-precede-grant EMPTY>
<!ELEMENT acl-requires-lock-token EMPTY>
 End of changes. 

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