INTERNET-DRAFT Geoffrey Clemm, Rational Software draft-ietf-webdav-acl-05 Anne Hopkins, Microsoft Corporation Eric Sedlar, Oracle Corporation Jim Whitehead, U.C. Santa Cruz Expires July 21, 2001 April 23, 2001 WebDAV Access Control Protocol Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document specifies a set of methods, headers, and message bodies that define the WebDAV Access Control extensions to the HTTP/1.1 protocol. This protocol permits a client to remotely read and modify access control lists that instruct a server whether to grant or deny operations upon a resource (such as HTTP method invocations) by a given principal. This document is a product of the Web Distributed Authoring and Versioning (WebDAV) working group of the Internet Engineering Task Force. Comments on this draft are welcomed, and should be addressed to the acl@webdav.org mailing list. Other related documents can be found at http://www.webdav.org/acl/, and http://www.ics.uci.edu/pub/ietf/webdav/. Clemm, Hopkins, Sedlar, Whitehead [Page 1]
INTERNET-DRAFT WebDAV ACL April 23, 2001 Table of Contents 1 INTRODUCTION......................................................4 1.1 Terms...........................................................5 1.2 Notational Conventions..........................................6 2 PRINCIPALS........................................................6 3 PRIVILEGES........................................................6 3.1 DAV:read Privilege..............................................7 3.2 DAV:write Privilege.............................................7 3.3 DAV:read-acl Privilege..........................................8 3.4 DAV:read-cuprivset Privilege....................................8 3.5 DAV:write-acl Privilege.........................................8 3.6 DAV:all Privilege...............................................8 4 PRINCIPAL PROPERTIES..............................................8 4.1 DAV:is-principal................................................9 4.2 DAV:alternate-URL...............................................9 5 ACCESS CONTROL PROPERTIES.........................................9 5.1 DAV:owner.......................................................9 5.2 DAV:supported-privilege-set....................................10 5.3 DAV:current-user-privilege-set.................................11 5.4 DAV:acl........................................................11 5.4.1 ACE Principal...............................................11 5.4.2 ACE Grant and Deny..........................................13 5.4.3 ACE Protection..............................................13 5.4.4 ACE Inheritance.............................................13 5.5 DAV:acl-semantics..............................................13 5.6 DAV:principal-collection-set...................................14 5.7 Example: PROPFIND to retrieve access control properties........14 6 ACL SEMANTICS....................................................17 6.1 ACE Combination................................................17 6.1.1 DAV:first-match ACE Combination.............................18 6.1.2 DAV:all-grant-before-any-deny ACE Combination...............18 6.1.3 DAV:specific-deny-overrides-grant ACE Combination...........18 6.2 ACE Ordering...................................................18 6.2.1 DAV:deny-before-grant ACE Ordering..........................18 6.3 Required Principals............................................18 7 ACCESS CONTROL AND EXISTING METHODS..............................19 7.1 OPTIONS........................................................19 7.1.1 Example - OPTIONS...........................................19 8 ACCESS CONTROL METHODS...........................................19 8.1 ACL............................................................19 8.1.1 ACL Preconditions...........................................20 8.1.2 Example: the ACL method.....................................20 8.1.3 Example: ACL method failure due to omission of protected ACE21 8.1.4 Example: ACL method failure due to inherited ACEs preceding non-inherited ACEs................................................22 Clemm, Hopkins, Sedlar, Whitehead [Page 2]
INTERNET-DRAFT WebDAV ACL April 23, 2001 8.1.5 Example: ACL method failure due to an attempt to set grant and deny in a single ACE..............................................23 9 INTERNATIONALIZATION CONSIDERATIONS..............................24 10 SECURITY CONSIDERATIONS........................................25 10.1 Increased Risk of Compromised Users...........................25 10.2 Risks of the read-acl and cuprivset Privileges................25 11 AUTHENTICATION.................................................26 12 IANA CONSIDERATIONS............................................26 13 INTELLECTUAL PROPERTY..........................................26 14 ACKNOWLEDGEMENTS...............................................26 15 REFERENCES.....................................................27 15.1 Normative References..........................................27 15.2 Informational References......................................28 16 AUTHORS' ADDRESSES.............................................28 17 APPENDICIES....................................................28 17.1 XML Document Type Definition..................................28 Clemm, Hopkins, Sedlar, Whitehead [Page 3]
INTERNET-DRAFT WebDAV ACL April 23, 2001 1 INTRODUCTION The goal of the WebDAV access control extensions is to provide an interoperable mechanism for handling discretionary access control for content in WebDAV servers. WebDAV access control can be implemented on content repositories with security as simple as that of a UNIX file system, as well as more sophisticated models. The underlying principle of access control is that who you are determines how you can access a resource. The "who you are" is defined by a "principal" identifier; users, client software, servers, and groups of the previous have principal identifiers. The "how" is determined by a single "access control list" (ACL) associated with a resource. An ACL contains a set of "access control entries" (ACEs), where each ACE specifies a principal and a set of privileges that are either granted or denied to that principal. When a principal submits an operation (such as an HTTP or WebDAV method) to a resource for execution, the server evaluates the ACEs in the ACL to determine if the principal has permission for that operation. This specification intentionally omits discussion of authentication, as the HTTP protocol already has a number of authentication mechanisms [RFC2617]. Some authentication mechanism (such as HTTP Digest Authentication, which all WebDAV compliant implementations are required to support) must be available to validate the identity of a principal. In the interests of timeliness, the following set of security mechanisms are not addressed by this document: * Access control that applies only to a particular property on a resource (excepting the access control properties DAV:acl and DAV:current-user-privilege-set), rather than the entire resource, * Role-based security (where a role can be seen as a dynamically defined collection of principals), * Specification of the ways an ACL on a resource is initialized, * Specification of an ACL that applies globally to a method, 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. Clemm, Hopkins, Sedlar, Whitehead [Page 4]
INTERNET-DRAFT WebDAV ACL April 23, 2001 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 This draft uses the terms defined in HTTP [RFC2616] and WebDAV [RFC2518]. In addition, the following terms are defined: principal A "principal" is a distinct human or computational actor that initiates access to network resources. In this protocol, a principal is an HTTP resource that represents such an actor. principal collection A "principal collection" is a group of principals, and is represented in this protocol by a WebDAV collection containing HTTP resources that represent principals, and principal collections. privilege A "privilege" controls access to a particular set of HTTP operations on a resource. aggregate privilege An "aggregate privilege" is a privilege that contains a set of other privileges. abstract privilege The modifier "abstract", when applied to an atomic or aggregate privilege, means the privilege cannot be set in an access control element (ace). access control list (acl) An "acl" is a list of access control elements that define access control to a particular resource. access control element (ace) An "ace" either grants or denies a particular set of (non-abstract) privileges for a particular principal. inherited ace An "inherited ace" is an ace that is shared from the acl of another resource. Clemm, Hopkins, Sedlar, Whitehead [Page 5]
INTERNET-DRAFT WebDAV ACL April 23, 2001 1.2 Notational Conventions The augmented BNF used by this document to describe protocol elements is described in Section 2.1 of [RFC2616]. Because this augmented BNF uses the basic production rules provided in Section 2.2 of [RFC2616], those rules apply to this document as well. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2 PRINCIPALS A principal is a network resource that represents a distinct human or computational actor that initiates access to network resources. On many implementations, users and groups are represented as principals; other types of principals are also possible. A URL of any scheme MAY be used to identify a principal resource. However, servers implementing this specification SHOULD expose principal resources at an http(s) URL, which is a privileged scheme that points to resources that have additional properties, as described in Section 4. Although an implementation SHOULD support PROPFIND and PROPPATCH to access and modify information about a principal, it is not required to do so. A principal resource may or may not be a collection. A collection principal may only contain other principals (not other types of resources). Servers that support aggregation of principals (e.g. groups of users or other groups) MUST manifest them as collection principals. The WebDAV methods for examining and maintaining collections (e.g. DELETE, PROPFIND) MAY be used to maintain collection principals. Membership in a collection principal is recursive, so a principal in a collection principal GRPA contained by collection principal GRPB is a member of both GRPA and GRPB. Implementations not supporting recursive membership in principal collections can return an error if the client attempts to bind collection principals into other collection principals. 3 PRIVILEGES Ability to perform a given method on a resource SHOULD be controlled by one or more privileges. Authors of protocol extensions that define new HTTP methods SHOULD specify which privileges (by defining new privileges, or mapping to ones below) are required to perform the method. A principal with no privileges to a resource SHOULD be denied any HTTP access to that resource. Privileges may be containers of other privileges, in which case they are termed aggregate privileges. If a principal is granted or denied an aggregate privilege, it is semantically equivalent to granting or denying each of the aggregated privileges individually. For example, an implementation may define add-member and remove- member privileges that control the ability to add and remove an internal member of a collection. Since these privileges control Clemm, Hopkins, Sedlar, Whitehead [Page 6]
INTERNET-DRAFT WebDAV ACL April 23, 2001 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. The access permissions on null and lock-null resources are solely those they inherit (if any), and they are not discoverable (i.e., the ACL properties specified in Section 5 are not defined on null and lock- null resources). On the transition from null or lock-null to a stateful resource, the initial access control list is set by the server's default ACL value policy (if any). 3.1 DAV:read Privilege The read privilege controls methods that return information about the state of the resource, including the resource's properties. Affected methods include GET and PROPFIND. Additionally, the read privilege MAY control the OPTIONS method. <!ELEMENT read EMPTY> 3.2 DAV:write Privilege The write privilege controls methods that modify the state of the resource, such as PUT and PROPPATCH. Note that state modification is also controlled via locking (see section 5.3 of [WEBDAV]), so effective write access requires that both write privileges and write locking requirements are satisfied. <!ELEMENT write EMPTY> Clemm, Hopkins, Sedlar, Whitehead [Page 7]
INTERNET-DRAFT WebDAV ACL April 23, 2001 3.3 DAV:read-acl Privilege The DAV:read-acl privilege controls the use of PROPFIND to retrieve the DAV:acl property of the resource. <!ELEMENT read-acl EMPTY> 3.4 DAV:read-cuprivset Privilege The DAV:read-cuprivset privilege controls the use of PROPFIND to retrieve the DAV:current-user-privilege-set property of the resource. Clients are intended to use this property to visually indicate in their UI items that are dependent on the permissions of a resource, for example, by graying out resources that are not writeable. This privilege is separate from DAV:read-acl because there is a need to allow most users access to the privileges permitted the current user (due to its use in creating the UI), while the full ACL contains information that may not be appropriate for the current authenticated user. As a result, the set of users who can view the full ACL is expected to be much smaller than those who can read the current user privilege set, and hence distinct privileges are needed for each <!ELEMENT read-cuprivset EMPTY> 3.5 DAV:write-acl Privilege The DAV:write-acl privilege controls use of the ACL method to modify the DAV:acl property of the resource. <!ELEMENT write-acl EMPTY> 3.6 DAV:all Privilege DAV:all is an aggregate privilege that contains all privileges on the resource. <!ELEMENT all EMPTY> 4 PRINCIPAL PROPERTIES Principals are manifested to clients as an HTTP resource, identified by a URL. A principal MUST have a DAV:displayname property. This protocol defines the following additional properties for a principal. The name and value of these properties SHOULD NOT be returned by PROPFIND allprop request (as defined in Section 12.14.1 of [RFC2518]). In the descriptions below, a read- only property is defined as a property that MUST NOT be writeable using PROPPATCH. Clemm, Hopkins, Sedlar, Whitehead [Page 8]
INTERNET-DRAFT WebDAV ACL April 23, 2001 4.1 DAV:is-principal This is a read-only property that indicates whether this resource is a principal. A resource MUST have a non-empty DAV:is-principal property if and only if it is a principal resource. <!ELEMENT is-principal (#PCDATA)> PCDATA value: "true" - resource is a principal, "false" - resource is not a principal (note that in cases where the "F" value might be used, this specification requires the property not be present at all). 4.2 DAV:alternate-URL This read-only property, if present, contains the URL of a network resource with additional descriptive information about the principal. This property identifies one or more additional network resources (i.e., it contains one or more URLs) that may be consulted by a client to gain additional knowledge concerning a principal. Two potential uses for this property are to store an ldap [RFC2255] or mailto [RFC2368] scheme URL. Support for this property is OPTIONAL. <!ELEMENT alternate-URL (href*)> 5 ACCESS CONTROL PROPERTIES This specification defines a number of new properties for WebDAV resources. Access control properties may be retrieved just like other WebDAV properties, using the PROPFIND method. Some access control properties (such as DAV:owner) MAY be updated with the PROPPATCH method. In the descriptions below, a read-only property is defined as a property that MUST NOT be writeable using PROPPATCH. Since it is expensive, for many servers, to retrieve access control information, a PROPFIND allprop request (as defined in Section 12.14.1 of [RFC2518]) SHOULD NOT return the names and values of the properties defined in this section. HTTP resources that support the WebDAV Access Control Protocol MUST contain the following properties. Null, and lock-null resources (described in Section 7.4 of [RFC2518]) MUST NOT contain the following properties: 5.1 DAV:owner This property identifies a particular principal as being the "owner" of the resource. Since the owner of a resource often has special access control capabilities (e.g., the owner frequently has permanent write-ACL privilege), clients might display the resource owner in their user interface. <!ELEMENT owner (href prop?)> <!ELEMENT prop (see [RFC2518], section 12.11)> Clemm, Hopkins, Sedlar, Whitehead [Page 9]
INTERNET-DRAFT WebDAV ACL April 23, 2001 An implementation MAY include a list of selected properties of that principal resource. Which properties (if any) are included is implementation defined, but might reasonably include properties such as DAV:displayname, which is useful for the construction of access control user interfaces on the client. A server might support this capability if it wished to save the client the additional network round-trip delay required to retrieve this information using a PROPFIND request on the principal URL in the href element. Servers that do not directly support PROPFIND on principal resources might also support this feature, since it allows them to return a server-controlled subset of the properties on the principal resource. An implementation MAY allow the use of PROPPATCH to update the DAV:owner field. If the DAV:owner property is writeable, clients MUST NOT submit the prop element; only the href element can be modified by the client. The purpose of this restriction is to limit the scope of effect of a PROPPATCH to just the owner property's resource; setting the prop element would additionally require modification to properties of the principal resource identified by the href element. 5.2 DAV:supported-privilege-set This is a read-only property that identifies the privileges defined for the resource. <!ELEMENT supported-privilege-set (supported-privilege*)> Each privilege appears as an XML element, where aggregate privileges list as sub-elements all of the privileges that they aggregate. <!ELEMENT supported-privilege (privilege, abstract?, description, supported-privilege*)> <!ELEMENT privilege ANY> An abstract privilege of a resource MUST NOT be used in an ACE for that resource. Servers MUST fail an attempt to set an abstract privilege. <!ELEMENT abstract EMPTY> A description is a human-readable description of what this privilege controls access to. <!ELEMENT description #PCDATA> It is envisioned that a WebDAV ACL-aware administrative client would list the supported privileges in a dialog box, and allow the user to choose non-abstract privileges to apply in an ACE. The privileges tree is useful programmatically to map well-known privileges (defined by WebDAV or other standards groups) into Clemm, Hopkins, Sedlar, Whitehead [Page 10]
INTERNET-DRAFT WebDAV ACL April 23, 2001 privileges that are supported by any particular server implementation. The privilege tree also serves to hide complexity in implementations allowing large number of privileges to be defined by displaying aggregates to the user. 5.3 DAV:current-user-privilege-set DAV:current-user-privilege-set is a read-only property containing the exact set of privileges (as computed by the server) granted to the currently authenticated HTTP user. Aggregate privileges and their contained privileges are listed. A user-agent can use the value of this property to adjust its user interface to make actions inaccessible (e.g., by graying out a menu item or button) for which the current principal does not have permission. This is particularly useful for an access control user interface, which can be constructed without knowing the ACE combining semantics of the server. This property is also useful for determining what operations the current principal can perform, without having to actually execute an operation. <!ELEMENT current-user-privilege-set (privilege*)> <!ELEMENT privilege ANY> If the current user is granted a specific privilege, that privilege must belong to the set of privileges that may be set on this resource. Therefore, each element in the DAV:current-user- privilege-set property MUST identify a non-abstract privilege from the DAV:supported-privilege-set property. 5.4 DAV:acl This is a read-only property that specifies the list of access control entries (ACEs), which define what principals are to get what privileges for this resource. <!ELEMENT acl (ace*)> Each DAV:ace element specifies the set of privileges to be either granted or denied to a single principal. If the DAV:acl property is empty, no principal is granted any privilege. <!ELEMENT ace (principal, (grant|deny), protected?, inherited?)> 5.4.1 ACE Principal The DAV:principal element identifies the principal to which this ACE applies. <!ELEMENT principal ((href, prop?) | all | authenticated | unauthenticated | property | self)> Clemm, Hopkins, Sedlar, Whitehead [Page 11]
INTERNET-DRAFT WebDAV ACL April 23, 2001 The current user matches DAV:href only if that user is authenticated as being (or being a member of) the principal identified by the URL contained by that DAV:href. 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 included in the DAV:prop element is implementation defined. The DAV:prop element can be used by servers that do not support PROPFIND requests on principal resources to return principal-related information (such as the value of the DAV:displayname property) that a client would find useful in the creation of an access control user interface. A server might also support this capability if it wished to save the client the additional network round-trip delays required to retrieve this information via a series of PROPFIND requests on each principal URL in the ACL. In the worst case, this is one additional PROPFIND per ACE. <!ELEMENT prop (see [RFC2518], section 12.11)> The current user always matches DAV:all. <!ELEMENT all EMPTY> The current user matches DAV:authenticated only if authenticated. <!ELEMENT authenticated EMPTY> The current user matches DAV:unauthenticated only if not authenticated. <!ELEMENT unauthenticated EMPTY> DAV:all is the union of DAV:authenticated, and DAV:unauthenticated. For a given request, the user matches either DAV:authenticated, or DAV:unauthenticated, but not both. The current user matches a DAV:property principal in a DAV:acl property of a resource only if the identified property of that resource contains a DAV:href that identifies a principal, and the current user is authenticated as being (or being a member of) that principal. For example, if the DAV:property element contained <DAV:owner/>, the current user would match the DAV:property principal only if the current user is authenticated as matching the principal identified by the DAV:owner property of the resource. <!ELEMENT property ANY> The current user matches DAV:self in a DAV:acl property of the resource only if that resource is a principal object and the current user is authenticated as being that principal. <!ELEMENT self EMPTY> Clemm, Hopkins, Sedlar, Whitehead [Page 12]
INTERNET-DRAFT WebDAV ACL April 23, 2001 5.4.2 ACE Grant and Deny Each DAV:grant or DAV:deny element specifies the set of privileges to be either granted or denied to the specified principal. A DAV:grant or DAV:deny element of the DAV:acl of a resource MUST only contain non-abstract elements specified in the DAV:supported- privilege-set of that resource. <!ELEMENT grant (privilege+)> <!ELEMENT deny (privilege+)> <!ELEMENT privilege ANY> 5.4.3 ACE Protection If an ACE contains a DAV:protected element, an ACL request without that ACE MUST fail. <!ELEMENT protected EMPTY> 5.4.4 ACE Inheritance The presence of a DAV:inherited element indicates that this ACE is inherited from another resource that is identified by the URL contained in a DAV:href element. An inherited ACE cannot be modified directly, but instead the ACL on the resource from which it is inherited must be modified. Note that ACE inheritance is not the same as ACL initialization. ACL initialization defines the ACL that a newly created resource will use (if not specified). ACE inheritance refers to an ACE that is logically shared - where an update to the resource containing an ACE will affect the ACE of each resource that inherits that ACE. The method by which ACLs are initialized or by which ACEs are inherited is not defined by this document. <!ELEMENT inherited (href)> 5.5 DAV:acl-semantics This is a read-only property that defines the ACL semantics. These semantics define how multiple ACEs that match the current user are combined, what are the constraints on how ACEs can be ordered, and which principals must have an ACE. A client user interface could use the value of this property to provide feedback to a human operator concerning the impact of proposed changes to an ACL. Alternately, a client could use this property to determine exactly, before submitting an ACL method invocation, what ACL changes it needs to make to accomplish a specific goal (or whether that goal is even achievable on this server). Since it is not practical to require all implementations to use the same ACL semantics, the DAV:acl-semantics property is used to identify the ACL semantics for a particular resource. The DAV:acl- semantics element is defined in section 6. Clemm, Hopkins, Sedlar, Whitehead [Page 13]
INTERNET-DRAFT WebDAV ACL April 23, 2001 5.6 DAV:principal-collection-set This read-only property contains zero, one, or more URLs that identify a collection principal. It is expected that implementations of this protocol will typically employ a relatively small number of locations in the URL namespace for principal, and collection principals. In cases where this assumption holds, the DAV:principal-collection-set property will contain a small set of URLs identifying the top of collection hierarchy containing multiple principals and collection principals. An access control protocol user agent could use the contents of DAV:principal- collection-set to 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. <!ELEMENT principal-collection-set (href*)> Since different servers can control different parts of the URL namespace, different resources on the same host MAY have different DAV:principal-collection-set values. The collections specified in the DAV:principal-collection-set MAY be located on different hosts from the resource. The URLs in DAV:principal-collection-set SHOULD be http or https scheme URLs. For security and scalability reasons, a server MAY report only a subset of the entire set of known collection 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. 5.7 Example: PROPFIND to retrieve access control properties The following example shows how access control information can be retrieved by using the PROPFIND method to fetch the values of the DAV:owner, DAV:supported-privilege-set, DAV:current-user-privilege- set, and DAV:acl properties. >> Request << PROPFIND /top/container/ HTTP/1.1 Host: www.foo.org Content-type: text/xml; charset="utf-8" Content-Length: xxx Depth: 0 Authorization: Digest username="ejw", realm="users@foo.org", nonce="...", uri="/top/container/", response="...", opaque="..." <?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:"> <D:owner/> <D:supported-privilege-set/> <D:current-user-privilege-set/> <D:acl/> </D:propfind> Clemm, Hopkins, Sedlar, Whitehead [Page 14]
INTERNET-DRAFT WebDAV ACL April 23, 2001 >> Response << HTTP/1.1 207 Multi-Status Content-Type: text/xml; charset="utf-8" Content-Length: xxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D="DAV:" xmlns:A="http://www.webdav.org/acl/"> <D:response> <D:propstat> <D:status>HTTP/1.1 200 OK</D:status> <D:prop> <D:owner> <D:href>http://www.foo.org/users/gclemm</D:href> </D:owner> <D:supported-privilege-set> <D:supported-privilege> <D:privilege> <D:all/> </D:privilege> <D:abstract/> <D:description>Any operation</D:description> <D:supported-privilege> <D:privilege> <D:read/> </D:privilege> <D:description>Read any object</D:description> </D:supported-privilege> <D:supported-privilege> <D:privilege> <D:write/> </D:privilege> <D:abstract/> <D:description>Write any object</D:description> <D:supported-privilege> <D:privilege> <A:create/> </D:privilege> <D:description>Create an object</D:description> </D:supported-privilege> <D:supported-privilege> <D:privilege> <A:update/> </D:privilege> <D:description>Update an object</D:description> </D:supported-privilege> <D:supported-privilege> <D:privilege> <A:delete/> </D:privilege> <D:description>Delete an object</D:description> </D:supported-privilege> </D:supported-privilege> <D:supported-privilege> <D:privilege> <D:read-acl/> </D:privilege> <D:description>Read the ACL</D:description> </D:supported-privilege> <D:supported-privilege> <D:privilege> <D:write-acl/> </D:privilege> <D:description>Write the ACL</D:description> </D:supported-privilege> </D:supported-privilege> </D:supported-privilege-set> <D:current-user-privilege-set> <D:privilege> <D:read/> </D:privilege> <D:privilege> <D:read-acl/> </D:privilege> Clemm, Hopkins, Sedlar, Whitehead [Page 15]
INTERNET-DRAFT WebDAV ACL April 23, 2001 </D:current-user-privilege-set> <D:acl> <D:ace> <D:principal> <D:href>http://www.foo.org/users/esedlar</D:href> <D:prop> <D:displayname>Eric Sedlar</D:displayname> </D:prop> </D:principal> <D:grant> <D:privilege> <D:read/> </D:privilege> <D:privilege> <D:write/> </D:privilege> <D:privilege> <D:read-acl/> </D:privilege> </D:grant> </D:ace> <D:ace> <D:principal> <D:href>http://www.foo.org/groups/marketing/</D:href> </D:principal> <D:deny> <D:privilege> <D:read/> </D:privilege> </D:deny> </D:ace> <D:ace> <D:principal> <D:property> <D:owner/> </D:property> </D:principal> <D:grant> <D:privilege> <D:read-acl/> </D:privilege> <D:privilege> <D:write-acl/> </D:privilege> </D:grant> </D:ace> <D:ace> <D:principal> <D:all/> </D:principal> <D:grant> <D:privilege> <D:read/> </D:privilege></D:grant> <D:inherited> <D:href>http://www.foo.org/top/</D:href> </D:inherited> </D:ace> </D:acl> </D:prop> </D:propstat> </D:response> </D:multistatus> The value of the DAV:owner property is a single DAV:href XML element containing the URL of the principal that owns this resource. The value of the DAV:supported-privilege-set property is a tree of supported privileges: DAV:all (aggregate, abstract) | +-- DAV:read +-- DAV:write (aggregate, abstract) | +-- http://www.webdav.org/acl/create +-- http://www.webdav.org/acl/update +-- http://www.webdav.org/acl/delete Clemm, Hopkins, Sedlar, Whitehead [Page 16]
INTERNET-DRAFT WebDAV ACL April 23, 2001 +-- DAV:read-acl +-- DAV:write-acl The DAV:current-user-privilege-set property contains two privileges, DAV:read, and DAV:read-acl. This indicates that the current authenticated user only has the ability to read the resource, and read the DAV:acl property on the resource. The DAV:acl property contains a set of four ACEs: ACE #1: The principal identified by the URL http://www.foo.org/users/esedlar is granted the DAV:read, DAV:write, and DAV:read-acl privileges. ACE #2: The principals identified by the URL http://www.foo.org/groups/marketing/ are denied the DAV:read privilege. In this example, the principal URL identifies a group, which is represented by a collection principal. ACE #3: In this ACE, the principal is a property principal, specifically the DAV:owner property. When evaluating this ACE, the value of the DAV:owner property is retrieved, and is examined to see if it contains a DAV:href XML element. If so, the URL within the DAV:href element is read, and identifies a principal. In this ACE, the owner is granted DAV:read-acl, and DAV:write-acl privileges. ACE #4: This ACE grants the DAV:all principal (all users) the DAV:read privilege. This ACE is inherited from the resource http://www.foo.org/top/, the parent collection of this resource. 6 ACL SEMANTICS The ACL semantics define how multiple ACEs that match the current user are combined, what are the constraints on how ACEs can be ordered, and which principals must have an ACE. <!ELEMENT acl-semantics acl-sem*> <!ELEMENT acl-sem (ace-combination, ace-ordering, required- principal*)> 6.1 ACE Combination The DAV:ace-combination element defines how privileges from multiple ACEs that match the current user will be combined to determine the access privileges for that user. Multiple ACEs may match the same user because the same principal can appear in multiple ACEs, because multiple principals can identify the same user, and because one principal can be a member of another principal. <!ELEMENT ace-combination Clemm, Hopkins, Sedlar, Whitehead [Page 17]
INTERNET-DRAFT WebDAV ACL April 23, 2001 (first-match | all-grant-before-any-deny | specific-deny- overrides-grant)> 6.1.1 DAV:first-match ACE Combination The ACEs are evaluated in the order in which they appear in the ACL. If the first ACE that matches the current user does not grant all the privileges needed for the request, the request MUST fail. <!ELEMENT first-match EMPTY> 6.1.2 DAV:all-grant-before-any-deny ACE Combination The ACEs are evaluated in the order in which they appear in the ACL. If an evaluated ACE denies a privilege needed for the request, the request MUST fail. If all ACEs have been evaluated without the user being granted all privileges needed for the request, the request MUST fail. <!ELEMENT all-grant-before-any-deny EMPTY> 6.1.3 DAV:specific-deny-overrides-grant ACE Combination All ACEs in the ACL are evaluated. An "individual ACE" is one whose principal identifies the current user. A "group ACE" is one whose principal is a collection that contains a principal that identifies the current user. A privilege is granted if it is granted by an individual ACE and not denied by an individual ACE, or if it is granted by a group ACE and not denied by an individual or group ACE. A request MUST fail if any of its needed privileges are not granted. <!ELEMENT specific-deny-overrides-grant EMPTY> 6.2 ACE Ordering The DAV:ace-ordering element defines a constraint on how the ACEs can be ordered in the ACL. <!ELEMENT ace-ordering (deny-before-grant)? > 6.2.1 DAV:deny-before-grant ACE Ordering This element indicates that all deny ACEs must precede all grant ACEs. <!ELEMENT deny-before-grant EMPTY> 6.3 Required Principals The required principal elements identify which principals must have an ACE defined in the ACL. <!ELEMENT required-principal (href | all | authenticated | unauthenticated | property | self)> Clemm, Hopkins, Sedlar, Whitehead [Page 18]
INTERNET-DRAFT WebDAV ACL April 23, 2001 For example, the following element requires that the ACL contain a DAV:owner property ACE: <D:required-principal xmlns:D="DAV:"> <D:property> <D:owner/> </D:property> </D:required-principal> 7 ACCESS CONTROL AND EXISTING METHODS This section defines the impact of access control functionality on existing methods. 7.1 OPTIONS If the server supports access control, it MUST return "access- control" as a field in the DAV response header from an OPTIONS request on any resource implemented by that server. 7.1.1 Example - OPTIONS >> Request << OPTIONS /foo.html HTTP/1.1 Host: www.webdav.org Content-Length: 0 >> Response << HTTP/1.1 200 OK DAV: 1, 2, access-control Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL In this example, the OPTIONS response indicates that the server supports access control and that /foo.html can have its access control list modified by the ACL method. 8 ACCESS CONTROL METHODS 8.1 ACL The ACL method modifies the DAV:acl property of a resource. A new DAV:acl value must be written in its entirety, including any inherited ACEs. Unless the DAV:acl property of the resource can be updated to be exactly the value specified in the ACL request, the ACL request MUST fail. If a server restricts the set of ACEs visible to the current user via the DAV:acl property, then the ACL request would only replace the set of ACEs visible to the current user, and would not affect any ACE that was not visible. In order to avoid overwriting DAV:acl changes by another client, a client SHOULD acquire a WebDAV lock on the resource before retrieving the DAV:acl property of a resource that it intends on updating. Clemm, Hopkins, Sedlar, Whitehead [Page 19]
INTERNET-DRAFT WebDAV ACL April 23, 2001 When submitting ACEs, clients MUST NOT include the optional prop element (a child of the principal element). The purpose of this restriction is to limit the scope of effect of the ACL method to just the resource identified by the Request-URI; setting the prop element would additionally require property modification for one or more principal resources. 8.1.1 ACL Preconditions An implementation MAY enforce one or more of the following constraints on an ACL request. If the constraint is violated, a 403 (Forbidden) response MUST be returned and the indicated XML element MUST be returned in the response body. <DAV:protected/>: An implementation MAY protect an ACE from modification or deletion. For example, some implementations implicitly grant the DAV:owner of a resource DAV:read-acl and DAV:write-acl privileges, and this cannot be changed by a client. <DAV: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 ACEs MUST precede all inherited ACEs. <DAV:deny-must-precede-grant/>: All non-inherited deny ACEs MUST precede all non-inherited grant ACEs. If the following precondition is not met, the server MUST return a 409 (Conflict) response, and the indicated XML element MUST be returned in the response body: <DAV:inhereted-exist-parent>: Inherited ACEs MUST exist on a parent resource. 8.1.2 Example: the ACL method In the following example, user "fielding", authenticated by information in the Authorization header, grants the principal identified by the URL http://www.foo.org/users/esedlar (i.e., the user "esedlar") read and write privileges, grants the owner of the resource read-acl and write-acl privileges, and grants everyone read privileges inherited from the parent collection http://www.foo.bar/top/. >> Request << ACL /top/container/ HTTP/1.1 Host: www.foo.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx Authorization: Digest username="fielding", realm="users@foo.org", nonce="...", Clemm, Hopkins, Sedlar, Whitehead [Page 20]
INTERNET-DRAFT WebDAV ACL April 23, 2001 uri="/top/container/", response="...", opaque="..." <?xml version="1.0" encoding="utf-8" ?> <D:acl xmlns:D="DAV:"> <D:ace> <D:principal> <D:href>http://www.foo.org/users/esedlar</D:href> </D:principal> <D:grant> <D:privilege> <D:read/> </D:privilege> <D:privilege> <D:write/> </D:privilege> </D:grant> </D:ace> <D:ace> <D:principal> <D:property> <D:owner/> </D:property> </D:principal> <D:grant> <D:privilege> <D:read-acl/> </D:privilege> <D:privilege> <D:write-acl/> </D:privilege> </D:grant> </D:ace> <D:ace> <D:principal> <D:all/> </D:principal> <D:grant> <D:privilege> <D:read/> </D:privilege></D:grant> <D:inherited> <D:href>http://www.foo.org/top/</D:href> </D:inherited> </D:ace> </D:acl> >> Response << HTTP/1.1 200 OK 8.1.3 Example: ACL method failure due to omission of protected ACE In the following request, user "fielding", authenticated by information in the Authorization header, attempts to grant the principal identified by the URL http://www.foo.org/users/esedlar (i.e., the user "esedlar") read privileges. Prior to the request, the DAV:acl property on the resource contained a protected ACE (see Section 5.4.3) granting DAV:owner the DAV:read-acl and DAV:write- acl privileges. The ACL method invocation fails because this protected ACE is omitted, thus violating the semantics of ACE protection.. >> Request << ACL /top/container/ HTTP/1.1 Host: www.foo.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx Authorization: Digest username="fielding", realm="users@foo.org", nonce="...", uri="/top/container/", response="...", opaque="..." <?xml version="1.0" encoding="utf-8" ?> Clemm, Hopkins, Sedlar, Whitehead [Page 21]
INTERNET-DRAFT WebDAV ACL April 23, 2001 <D:acl xmlns:D="DAV:"> <D:ace> <D:principal> <D:href>http://www.foo.org/users/esedlar</D:href> </D:principal> <D:grant> <D:privilege> <D:read/> </D:privilege> </D: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:protected/> 8.1.4 Example: ACL method failure due to inherited ACEs preceding non- inherited ACEs In the following request, user "ejw", authenticated by information in the Authorization header, tries to change the access control list on the resource http://www.foo.org/top/index.html. This resource has two inherited ACEs. Inherited ACE #1 grants the principal identified by URL http://www.foo.org/users/ejw (i.e., the user "ejw") http://www.foo.org/privs/write-all and DAV:read-acl privileges. On this server, http://www.foo.org/privs/write-all is an aggregate privilege containing DAV:write, and DAV:write-acl. Inherited ACE #2 grants principal DAV:all the DAV:read privilege. The request attempts to add a third ACE, granting the principal identified by the URL http://www.foo.org/users/gclemm (i.e., the user ôgclemmö) DAV:write permission, but in the request places the inherited ACEs before the non-inherited ACEs, causing an error on this specific server implementation. Note that on a different implementation, this request might be accepted. >> Request << ACL /top/index.html HTTP/1.1 Host: www.foo.org Content-Type: text/xml; charset="utf-8" Content-Length: xxxx Authorization: Digest username="ejw", realm="users@foo.org", nonce="...", uri="/top/index.html", response="...", opaque="..." <?xml version="1.0" encoding="utf-8" ?> <D:acl xmlns:D="DAV:" xmlns:F="http://www.foo.org/privs/"> Clemm, Hopkins, Sedlar, Whitehead [Page 22]
INTERNET-DRAFT WebDAV ACL April 23, 2001 <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 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", Clemm, Hopkins, Sedlar, Whitehead [Page 23]
INTERNET-DRAFT WebDAV ACL April 23, 2001 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 description XML element, found within the DAV:supported- privilege-set property. This element contains a human-readable description of the capabilities controlled by a privilege. As a result, the description element must be capable of representing descriptions in multiple character sets. Since the description element is found within a WebDAV property, it is represented on- the-wire as XML [REC-XML], and hence can leverage XML's language tagging and character set encoding capabilities. Specifically, XML processors must, at minimum, be able to read XML elements encoded using the UTF-8 [UTF-8] encoding of the ISO 10646 multilingual plane. XML examples in this specification demonstrate use of the charset parameter of the Content-Type header, as defined in [RFC3023], as well as the XML "encoding" attribute, which together provide charset identification information for MIME and XML processors. For XML elements other than the description element, it is expected that implementations will treat the property names, privilege names, and values as tokens, and convert these tokens into human- readable text in the user's language and character set when displayed to a person. Only a generic WebDAV property display utility would display these values in their raw form to a human user. Clemm, Hopkins, Sedlar, Whitehead [Page 24]
INTERNET-DRAFT WebDAV ACL April 23, 2001 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 Applications and users of this access control protocol should be aware of several security considerations, detailed below. In addition to the discussion in this document, the security considerations detailed in the HTTP/1.1 specification [RFC2616], the WebDAV Distributed Authoring Protocol specification [RFC2518], and the XML Media Types specification [RFC3023] should be considered in a security analysis of this protocol. 10.1 Increased Risk of Compromised Users In the absence of a mechanism for remotely manipulating access control lists, if a single user's authentication credentials are compromised, only those resources for which the user has access permission can be read, modified, moved, or deleted. With the introduction of this access control protocol, if a single compromised user has the ability to change ACLs for a broad range of other users (e.g., a super-user), the number of resources that could be altered by a single compromised user increases. This risk can be mitigated by limiting the number of people who have write- acl privileges across a broad range of resources. 10.2 Risks of the read-acl and cuprivset Privileges The ability to read the access privileges (stored in the DAV:acl property), or the privileges permitted the currently authenticated user (stored in the DAV:current-user-privilege-set property) on a resource may seem innocuous, since reading an ACL cannot possibly affect the resource's state. However, if all resources have world- readable ACLs, it is possible to perform an exhaustive search for those resources that have inadvertently left themselves in a vulnerable state, such as being world-writeable. In particular, the property retrieval method PROPFIND, executed with Depth infinity on an entire hierarchy, is a very efficient way to retrieve the DAV:acl or DAV:current-user-privilege-set properties. Once found, this vulnerability can be exploited by a denial of service attack in which the open resource is repeatedly overwritten. Alternately, writeable resources can be modified in undesirable ways. To reduce this risk, read-acl privileges should not be granted to unauthenticated principals, and restrictions on read-acl and Clemm, Hopkins, Sedlar, Whitehead [Page 25]
INTERNET-DRAFT WebDAV ACL April 23, 2001 cuprivset privileges for authenticated principals should be carefully analyzed when deploying this protocol. Access to the current-user-privilege-set property will involve a tradeoff of usability versus security. When the current-user-privilege-set is visible, user interfaces are expected to provide enhanced information concerning permitted and restricted operations, yet this information may also indicate a vulnerability that could be exploited. Deployment of this protocol will need to evaluate this tradeoff in light of the requirements of the deployment environment. 11 AUTHENTICATION Authentication mechanisms defined in WebDAV also apply to this WebDAV Access Control Protocol, in particular the Basic and Digest authentication mechanisms defined in [RFC2617]. 12 IANA CONSIDERATIONS This document uses the namespace defined by [RFC2518] for XML elements. All other IANA considerations mentioned in [RFC2518] also applicable to WebDAV ACL. 13 INTELLECTUAL PROPERTY The following notice is copied from RFC 2026, section 10.4, and describes the position of the IETF concerning intellectual property claims made against this document. The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use other technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 14 ACKNOWLEDGEMENTS This protocol is the collaborative product of the WebDAV ACL design team: Bernard Chester, Geoff Clemm (Rational), Anne Hopkins Clemm, Hopkins, Sedlar, Whitehead [Page 26]
INTERNET-DRAFT WebDAV ACL April 23, 2001 (Microsoft), Barry Lind (Xythos), Sean Lyndersay (Microsoft), Eric Sedlar (Oracle), Greg Stein (Apache.org), and Jim Whitehead (UC Santa Cruz). The authors are grateful for the detailed review and comments provided by Jim Amsden, Gino Basso, Murthy Chintalapati, Dennis Hamilton, Laurie Harper, Ron Jacobs, Chris Knight, and Remy Maucherat. Prior work on WebDAV access control protocols has been performed by Yaron Goland, Paul Leach, Lisa Dusseault, Howard Palmer, and Jon Radoff. We would like to acknowledge the foundation laid for us by the authors of the WebDAV and HTTP protocols upon which this protocol is layered, and the invaluable feedback from the WebDAV working group. 15 REFERENCES 15.1 Normative References [RFC2119] S.Bradner, "Key words for use in RFCs to Indicate Requirement Levels." RFC 2119, BCP 14, Harvard, March, 1997. [REC-XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible Markup Language (XML)." World Wide Web Consortium Recommendation REC-xml-19980210. http://www.w3.org/TR/REC-xml-19980210. [RFC2616] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, L. Masinter, P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1." RFC 2616. U.C.Irvine, Compaq, Xerox, Microsoft, MIT/LCS, June, 1999. [RFC2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, P. Leach, A. Luotonen, L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication. " RFC 2617. Northwestern University, Verisign, AbiSource, Agranat, Microsoft, Netscape, Open Market, June, 1999. [RFC2518] Y. Goland, E. Whitehead, A. Faizi, S. R. Carter, D. Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV." RFC 2518. Microsoft, U.C.Irvine, Netscape, Novell, February, 1999. [RFC2368] P. Hoffman, L. Masinter, J. Zawinski, "The mailto URL scheme." RFC 2368. Internet Mail Consortium, Xerox, Netscape, July, 1998. [RFC2255] T. Howes, M. Smith, "The LDAP URL Format." RFC 2255. Netscape, December, 1997. [RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types." RFC 3023. IBM Tokyo Research Laboratory, simonstl.com, Skymoon Ventures, January, 2001. [UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode and ISO 10646." RFC 2279. Alis Technologies. January, 1998. Clemm, Hopkins, Sedlar, Whitehead [Page 27]
INTERNET-DRAFT WebDAV ACL April 23, 2001 15.2 Informational References [RFC2026] S.Bradner, "The Internet Standards Process -- Revision 3." RFC 2026, BCP 9. Harvard, October, 1996. 16 AUTHORS' ADDRESSES Geoffrey Clemm Rational Software 20 Maguire Road Lexington, MA 02421 Email: geoffrey.clemm@rational.com Anne Hopkins Microsoft Corporation One Microsoft Way Redmond, WA 98052 Email: annehop@microsoft.com Eric Sedlar Oracle Corporation 500 Oracle Parkway Redwood Shores, CA 94065 Email: esedlar@us.oracle.com Jim Whitehead U.C. Santa Cruz Dept. of Computer Science Baskin Engineering 1156 High Street Santa Cruz, CA 95064 Email: ejw@cse.ucsc.edu 17 APPENDICIES 17.1 XML Document Type Definition <!-- Privileges --> <!ELEMENT read EMPTY> <!ELEMENT write EMPTY> <!ELEMENT read-acl EMPTY> <!ELEMENT read-cuprivset EMPTY> <!ELEMENT write-acl EMPTY> <!ELEMENT all EMPTY> <!-- Principal Properties (Section 4) --> <!ELEMENT is-principal (#PCDATA)> <!ELEMENT alternate-URL (href*)> Clemm, Hopkins, Sedlar, Whitehead [Page 28]
INTERNET-DRAFT WebDAV ACL April 23, 2001 <!-- 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) --> <!ELEMENT principal-collection-set (href*)> Clemm, Hopkins, Sedlar, Whitehead [Page 29]
INTERNET-DRAFT WebDAV ACL April 23, 2001 <!-- 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 | specific-deny- overrides-grant)> <!ELEMENT first-match EMPTY> <!ELEMENT all-grant-before-any-deny EMPTY> <!ELEMENT specific-deny-overrides-grant EMPTY> <!ELEMENT ace-ordering (deny-before-grant)? > <!ELEMENT deny-before-grant EMPTY> <!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> <!ELEMENT inherited-exist-parent EMPTY> Clemm, Hopkins, Sedlar, Whitehead [Page 30]
