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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT Geoffrey Clemm, IBM 3 draft-ietf-webdav-acl-12 Anne Hopkins, Microsoft Corporation 4 Eric Sedlar, Oracle Corporation 5 Jim Whitehead, U.C. Santa Cruz 7 Expires April 10, 2004 October 10, 2003 9 WebDAV Access Control Protocol 11 Status of this Memo 12 This document is an Internet-Draft and is subject to all provisions of 13 Section 10 of RFC2026. 14 Internet-Drafts are working documents of the Internet Engineering Task 15 Force (IETF), its areas, and its working groups. Note that other groups 16 may also distribute working documents as Internet-Drafts. 17 Internet-Drafts are draft documents valid for a maximum of six months 18 and may be updated, replaced, or obsoleted by other documents at any 19 time. It is inappropriate to use Internet-Drafts as reference material 20 or to cite them other than as "work in progress." 21 The list of current Internet-Drafts can be accessed at 22 http://www.ietf.org/ietf/1id-abstracts.txt 23 The list of Internet-Draft Shadow Directories can be accessed at 24 http://www.ietf.org/shadow.html. 26 Abstract 27 This document specifies a set of methods, headers, message bodies, 28 properties, and reports that define Access Control extensions to the 29 WebDAV Distributed Authoring Protocol. This protocol permits a client 30 to read and modify access control lists that instruct a server whether 31 to allow or deny operations upon a resource (such as HyperText Transfer 32 Protocol (HTTP) method invocations) by a given principal. A lightweight 33 representation of principals as Web resources supports integration of a 34 wide range of user management repositories. Search operations allow 35 discovery and manipulation of principals using human names. 36 This document is a product of the Web Distributed Authoring and 37 Versioning (WebDAV) working group of the Internet Engineering Task 38 Force. Comments on this draft are welcomed, and should be addressed to 39 the acl@webdav.org mailing list. Other related documents can be found 40 at http://www.example.com/acl/, and 41 http://www.ics.uci.edu/pub/ietf/webdav/. 43 Clemm, Hopkins, Sedlar, Whitehead 44 Table of Contents 46 1 INTRODUCTION.................................................4 47 1.1 Terms......................................................6 48 1.2 Notational Conventions.....................................7 50 2 PRINCIPALS...................................................7 52 3 PRIVILEGES...................................................8 53 3.1 DAV:read Privilege.........................................9 54 3.2 DAV:write Privilege........................................9 55 3.3 DAV:write-properties.......................................9 56 3.4 DAV:write-content.........................................10 57 3.5 DAV:unlock................................................10 58 3.6 DAV:read-acl Privilege....................................10 59 3.7 DAV:read-current-user-privilege-set Privilege.............10 60 3.8 DAV:write-acl Privilege...................................11 61 3.9 DAV:bind Privilege........................................11 62 3.10 DAV:unbind Privilege.....................................11 63 3.11 DAV:all Privilege........................................11 64 3.12 Aggregation of Predefined Privileges.....................11 66 4 PRINCIPAL PROPERTIES........................................12 67 4.1 DAV:alternate-URI-set.....................................12 68 4.2 DAV:principal-URL.........................................12 69 4.3 DAV:group-member-set......................................12 70 4.4 DAV:group-membership......................................13 72 5 ACCESS CONTROL PROPERTIES...................................13 73 5.1 DAV:owner.................................................13 74 5.1.1 Example: Retrieving DAV:owner..........................13 75 5.1.2 Example: An Attempt to Set DAV:owner...................14 76 5.2 DAV:supported-privilege-set...............................15 77 5.2.1 Example: Retrieving a List of Privileges Supported on 78 a Resource.............................................16 79 5.3 DAV:current-user-privilege-set............................18 80 5.3.1 Example: Retrieving the User's Current Set of Assigned 81 Privileges...................................................19 82 5.4 DAV:acl...................................................20 83 5.4.1 ACE Principal..........................................20 84 5.4.2 ACE Grant and Deny.....................................21 85 5.4.3 ACE Protection.........................................21 86 5.4.4 ACE Inheritance........................................21 87 5.4.5 Example: Retrieving a Resource's Access Control List ..22 88 5.5 DAV: acl-restrictions.....................................23 89 5.5.1 DAV:grant-only.........................................23 90 5.5.2 DAV:no-invert ACE Constraint...........................24 91 5.5.3 DAV:deny-before-grant..................................24 92 5.5.4 Required Principals....................................24 93 Example: Retrieving DAV:acl-restrictions............. ...24 94 5.6 DAV:inherited-acl-set.....................................25 95 5.7 DAV:principal-collection-set..............................25 96 5.7.1 Example: Retrieving DAV:principal-collection-set.......26 97 5.8 Example: PROPFIND to retrieve access control properties...27 98 6 ACL EVALUATION..............................................30 100 7 ACCESS CONTROL AND EXISTING METHODS.........................31 101 7.1 ANY HTTP METHOD...........................................32 102 7.1.1 Error Handling.........................................32 103 7.2 OPTIONS...................................................32 104 7.2.1 Example - OPTIONS......................................33 105 7.3 MOVE......................................................33 106 7.4 COPY......................................................33 107 7.5 LOCK......................................................33 109 8 ACCESS CONTROL METHODS......................................33 110 8.1 ACL.......................................................33 111 8.1.1 ACL Preconditions......................................34 112 8.1.2 Example: the ACL method................................35 113 8.1.3 Example: ACL method failure due to protected ACE 114 conflict...............................................36 115 8.1.4 Example: ACL method failure due to an inherited ACE 116 conflict...............................................37 117 8.1.5 Example: ACL method failure due to an attempt to set 118 grant and deny in a single ACE.........................38 120 9 ACCESS CONTROL REPORTS......................................39 121 9.1 REPORT Method.............................................39 122 9.2 DAV:acl-principal-prop-set Report.........................39 123 9.2.1 Example: DAV:acl-principal-prop-set Report.............40 124 9.3 DAV:principal-match REPORT................................42 125 9.3.1 Example: DAV:principal-match REPORT....................43 126 9.4 DAV:principal-property-search REPORT......................43 127 9.4.1 Matching...............................................45 128 9.4.2 Example: successful DAV:principal-property-search 129 REPORT.................................................46 130 9.5 DAV:principal-search-property-set REPORT..................48 131 9.5.1 Example: DAV:principal-search-property-set REPORT......49 133 10 XML PROCESSING............................................50 135 11 INTERNATIONALIZATION CONSIDERATIONS.......................50 137 12 SECURITY CONSIDERATIONS...................................51 138 12.1 Increased Risk of Compromised Users......................51 139 12.2 Risks of the DAV:read-acl and 140 DAV:current-user-privilege-set Privileges................51 141 12.3 No Foreknowledge of Initial ACL..........................52 143 13 AUTHENTICATION............................................52 145 14 IANA CONSIDERATIONS.......................................52 147 15 INTELLECTUAL PROPERTY.....................................53 149 16 ACKNOWLEDGEMENTS..........................................53 151 17 REFERENCES................................................53 152 17.1 Normative References.....................................53 153 17.2 Informational References.................................54 155 18 AUTHORS' ADDRESSES........................................55 157 19 APPENDICES................................................56 158 19.1 WebDAV XML Document Type Definition Addendum.............56 159 19.2 WebDAV Method Privilege Table (Normative)................58 161 1 INTRODUCTION 163 The goal of the WebDAV access control extensions is to provide an 164 interoperable mechanism for handling discretionary access control 165 for content and metadata managed by WebDAV servers. WebDAV access 166 control can be implemented on content repositories with security 167 as simple as that of a UNIX file system, as well as more 168 sophisticated models. The underlying principle of access control 169 is that who you are determines what operations you can perform on 170 a resource. The "who you are" is defined by a "principal" 171 identifier; users, client software, servers, and groups of the 172 previous have principal identifiers. The "operations you can 173 perform" are determined by a single "access control list" (ACL) 174 associated with a resource. An ACL contains a set of "access 175 control entries" (ACEs), where each ACE specifies a principal and 176 a set of privileges that are either granted or denied to that 177 principal. When a principal submits an operation (such as an HTTP 178 or WebDAV method) to a resource for execution, the server 179 evaluates the ACEs in the ACL to determine if the principal has 180 permission for that operation. 181 Since every ACE contains the identifier of a principal, client 182 software operated by a human must provide a mechanism for 183 selecting this principal. This specification uses http(s) scheme 184 URLs to identify principals, which are represented as WebDAV- 185 capable resources. There is no guarantee that the URLs identifying 186 principals will be meaningful to a human. For example, 187 http://www.example.com/u/256432 and 188 http://www.example.com/people/Greg.Stein are both valid URLs that 189 could be used to identify the same principal. To remedy this, 190 every principal resource has the DAV:displayname property 191 containing a human-readable name for the principal. 192 Since a principal can be identified by multiple URLs, it raises 193 the problem of determining exactly which principal is being 194 referenced in a given ACE. It is impossible for a client to 195 determine that an ACE granting the read privilege to 196 http://www.example.com/people/Greg.Stein also affects the 197 principal at http://www.example.com/u/256432. That is, a client 198 has no mechanism for determining that two URLs identify the same 199 principal resource. As a result, this specification requires 200 clients to use just one of the many possible URLs for a principal 201 when creating ACEs. A client can discover which URL to use by 202 retrieving the DAV:principal-URL property (Section 4.2) from a 203 principal resource. No matter which of the principal's URLs is 204 used with PROPFIND, the property always returns the same URL. 206 With a system having hundreds to thousands of principals, the 207 problem arises of how to allow a human operator of client software 208 to select just one of these principals. One approach is to use 209 broad collection hierarchies to spread the principals over a large 210 number of collections, yielding few principals per collection. An 211 example of this is a two level hierarchy with the first level 212 containing 36 collections (a-z, 0-9), and the second level being 213 another 36, creating collections /a/a/, /a/b/, ..., /a/z/, such 214 that a principal with last name "Stein" would appear at 215 /s/t/Stein. In effect, this pre-computes a common query, search on 216 last name, and encodes it into a hierarchy. The drawback with this 217 scheme is that it handles only a small set of predefined queries, 218 and drilling down through the collection hierarchy adds 219 unnecessary steps (navigate down/up) when the user already knows 220 the principal's name. While organizing principal URLs into a 221 hierarchy is a valid namespace organization, users should not be 222 forced to navigate this hierarchy to select a principal. 223 This specification provides the capability to perform substring 224 searches over a small set of properties on the resources 225 representing principals. This permits searches based on last name, 226 first name, user name, job title, etc. Two separate searches are 227 supported, both via the REPORT method, one to search principal 228 resources (DAV:principal-property-search, Section 9.4), the other 229 to determine which properties may be searched at all 230 (DAV:principal-search-property-set, Section 9.5). 231 Once a principal has been identified in an ACE, a server 232 evaluating that ACE must know the identity of the principal making 233 a protocol request, and must validate that that principal is who 234 they claim to be, a process known as authentication. This 235 specification intentionally omits discussion of authentication, as 236 the HTTP protocol already has a number of authentication 237 mechanisms [RFC2617]. Some authentication mechanism (such as HTTP 238 Digest Authentication, which all WebDAV compliant implementations 239 are required to support) must be available to validate the 240 identity of a principal. 241 The following issues are out of scope for this document: 242 . Access control that applies only to a particular property on 243 a resource (excepting the access control properties DAV:acl 244 and DAV:current-user-privilege-set), rather than the entire 245 resource, 246 . Role-based security (where a role can be seen as a 247 dynamically defined group of principals), 248 . Specification of the ways an ACL on a resource is 249 initialized, 250 . Specification of an ACL that applies globally to all 251 resources, rather than to a particular resource. 252 . Creation and maintenance of resources representing people or 253 computational agents (principals), and groups of these. 255 This specification is organized as follows. Section 1.1 defines 256 key concepts used throughout the specification, and is followed by 257 a more in-depth discussion of principals (Section 2), and 258 privileges (Section 3). Properties defined on principals are 259 specified in Section 4, and access control properties for content 260 resources are specified in Section 5. The ways ACLs are to be 261 evaluated is described in section 6. Client discovery of access 262 control capability using OPTIONS is described in Section 7.1. 263 Interactions between access control functionality and existing 264 HTTP and WebDAV methods are described in the remainder of Section 265 7. The access control setting method, ACL, is specified in Section 266 8. Four reports that provide limited server-side searching 267 capabilities are described in Section 9. Sections on XML 268 processing (Section 10), Internationalization considerations 269 (Section 11), security considerations (Section 12), and 270 authentication (Section 13) round out the specification. An 271 appendix (Section 19.1) provides an XML Document Type Definition 272 (DTD) for the XML elements defined in the specification. 274 1.1 Terms 276 This draft uses the terms defined in HTTP [RFC2616] and WebDAV 277 [RFC2518]. In addition, the following terms are defined: 278 principal 279 A "principal" is a distinct human or computational actor that 280 initiates access to network resources. In this protocol, a 281 principal is an HTTP resource that represents such an actor. 282 group 283 A "group" is a principal that represents a set of other 284 principals. 285 privilege 286 A "privilege" controls access to a particular set of HTTP 287 operations on a resource. 288 aggregate privilege 289 An "aggregate privilege" is a privilege that contains a set of 290 other privileges. 291 abstract privilege 292 The modifier "abstract", when applied to a privilege on a 293 resource, means the privilege cannot be set in an access control 294 element (ACE) on that resource . 295 access control list (ACL) 296 An "ACL" is a list of access control elements that define access 297 control to a particular resource. 298 access control element (ACE) 299 An "ACE" either grants or denies a particular set of (non- 300 abstract) privileges for a particular principal. 302 inherited ACE 303 An "inherited ACE" is an ACE that is dynamically shared from the 304 ACL of another resource. When a shared ACE changes on the primary 305 resource, it is also changed on inheriting resources. 306 protected property 307 A "protected property" is one whose value cannot be updated except 308 by a method explicitly defined as updating that specific property. 309 In particular, a protected property cannot be updated with a 310 PROPPATCH request. 312 1.2 Notational Conventions 314 The augmented BNF used by this document to describe protocol 315 elements is described in Section 2.1 of [RFC2616]. Because this 316 augmented BNF uses the basic production rules provided in Section 317 2.2 of [RFC2616], those rules apply to this document as well. 318 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL 319 NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" 320 in this document are to be interpreted as described in [RFC2119]. 321 Definitions of XML elements in this document use XML element type 322 declarations (as found in XML Document Type Declarations), 323 described in Section 3.2 of [REC-XML]. When an XML element type in 324 the "DAV:" namespace is referenced in this document outside of the 325 context of an XML fragment, the string "DAV:" will be prefixed to 326 the element name. 328 2 PRINCIPALS 330 A principal is a network resource that represents a distinct human 331 or computational actor that initiates access to network resources. 332 Users and groups are represented as principals in many 333 implementations; other types of principals are also possible. A 334 URI of any scheme MAY be used to identify a principal resource. 335 However, servers implementing this specification MUST expose 336 principal resources at an http(s) URL, which is a privileged 337 scheme that points to resources that have additional properties, 338 as described in Section 4. So, a principal resource can have 339 multiple URIs, one of which has to be an http(s) scheme URL. 340 Although an implementation SHOULD support PROPFIND and MAY support 341 PROPPATCH to access and modify information about a principal, it 342 is not required to do so. 343 A principal resource may be a group, where a group is a principal 344 that represents a set of other principals, called the members of 345 the group. If a person or computational agent matches a principal 346 resource that is a member of a group, they also match the group. 347 Membership in a group is recursive, so if a principal is a member 348 of group GRPA, and GRPA is a member of group GRPB, then the 349 principal is also a member of GRPB. 351 3 PRIVILEGES 353 Ability to perform a given method on a resource MUST be controlled 354 by one or more privileges. Authors of protocol extensions that 355 define new HTTP methods SHOULD specify which privileges (by 356 defining new privileges, or mapping to ones below) are required to 357 perform the method. A principal with no privileges to a resource 358 MUST be denied any HTTP access to that resource, unless the 359 principal matches an ACE constructed using the DAV:all, 360 DAV:authenticated, or DAV:unauthenticated pseudo-principals (see 361 Section 5.4.1). Servers MUST report a 403 "Forbidden" error if 362 access is denied, except in the case where the privilege restricts 363 the ability to know the resource exists, in which case 404 "Not 364 Found" may be returned. 365 Privileges may be containers of other privileges, in which case 366 they are termed "aggregate privileges". If a principal is granted 367 or denied an aggregate privilege, it is semantically equivalent to 368 granting or denying each of the aggregated privileges 369 individually. For example, an implementation may define add- 370 member and remove-member privileges that control the ability to 371 add and remove a member of a group. Since these privileges 372 control the ability to update the state of a group, these 373 privileges would be aggregated by the DAV:write privilege on a 374 group, and granting the DAV:write privilege on a group would also 375 grant the add-member and remove-member privileges. 376 Privileges may be declared to be "abstract" for a given resource, 377 in which case they cannot be set in an ACE on that resource. 378 Aggregate and non-aggregate privileges are both capable of being 379 abstract. Abstract privileges are useful for modeling privileges 380 that otherwise would not be exposed via the protocol. Abstract 381 privileges also provide server implementations with flexibility in 382 implementing the privileges defined in this specification. For 383 example, if a server is incapable of separating the read resource 384 capability from the read ACL capability, it can still model the 385 DAV:read and DAV:read-acl privileges defined in this specification 386 by declaring them abstract, and containing them within a non- 387 abstract aggregate privilege (say, read-all) that holds DAV:read, 388 and DAV:read-acl. In this way, it is possible to set the aggregate 389 privilege, read-all, thus coupling the setting of DAV:read and 390 DAV:read-acl, but it is not possible to set DAV:read, or DAV:read- 391 acl individually. Since aggregate privileges can be abstract, it 392 is also possible to use abstract privileges to group or organize 393 non-abstract privileges. Privilege containment loops are not 394 allowed; therefore, a privilege MUST NOT contain itself. For 395 example, DAV:read cannot contain DAV:read. 396 The set of privileges that apply to a particular resource may vary 397 with the DAV:resourcetype of the resource, as well as between 398 different server implementations. To promote interoperability, 399 however, this specification defines a set of well-known privileges 400 (e.g. DAV:read, DAV:write, DAV:read-acl, DAV:write-acl, DAV:read- 401 current-user-privilege-set, and DAV:all), which can at least be 402 used to classify the other privileges defined on a particular 403 resource. The access permissions on null resources (defined in 404 [RFC2518], Section 3) are solely those they inherit (if any), and 405 they are not discoverable (i.e., the access control properties 406 specified in Section 5 are not defined on null resources). On the 407 transition from null to stateful resource, the initial access 408 control list is set by the server's default ACL value policy (if 409 any). 410 Server implementations MAY define new privileges beyond those 411 defined in this specification. Privileges defined by individual 412 implementations MUST NOT use the DAV: namespace, and instead 413 should use a namespace that they control, such as an http scheme 414 URL. 416 3.1 DAV:read Privilege 418 The read privilege controls methods that return information about 419 the state of the resource, including the resource's properties. 420 Affected methods include GET and PROPFIND. Any implementation- 421 defined privilege that also controls access to GET and PROPFIND 422 must be aggregated under DAV:read�if an ACL grants access to 423 DAV:read, the client may expect that no other privilege needs to 424 be granted to have access to GET and PROPFIND. Additionally, the 425 read privilege MUST control the OPTIONS method. 426 428 3.2 DAV:write Privilege 430 The write privilege controls methods that lock a resource or 431 modify the content, dead properties, or (in the case of a 432 collection) membership of the resource, such as PUT and PROPPATCH. 433 Note that state modification is also controlled via locking (see 434 section 5.3 of [WEBDAV]), so effective write access requires that 435 both write privileges and write locking requirements are 436 satisfied. Any implementation-defined privilege that also 437 controls access to methods modifying content, dead properties or 438 collection membership must be aggregated under DAV:write, e.g. if 439 an ACL grants access to DAV:write, the client may expect that no 440 other privilege needs to be granted to have access to PUT and 441 PROPPATCH. 442 444 3.3 DAV:write-properties 446 The DAV:write-properties privilege controls methods that modify 447 the dead properties of the resource, such as PROPPATCH. Whether 448 this privilege may be used to control access to any live 449 properties is determined by the implementation. Any 450 implementation-defined privilege that also controls access to 451 methods modifying dead properties must be aggregated under 452 DAV:write-properties�e.g. if an ACL grants access to DAV:write- 453 properties, the client can safely expect that no other privilege 454 needs to be granted to have access to PROPPATCH. 456 458 3.4 DAV:write-content 460 The DAV:write-content privilege controls methods that modify the 461 content or (in the case of a collection) membership of the 462 resource, such as PUT and DELETE. Any implementation-defined 463 privilege that also controls access to content or alteration of 464 collection membership must be aggregated under DAV:write-content� 465 e.g. if an ACL grants access to DAV:write-content, the client can 466 safely expect that no other privilege needs to be granted to have 467 access to PUT or DELETE. 468 470 3.5 DAV:unlock 472 The DAV:unlock privilege controls the use of the UNLOCK method by 473 a principal other than the lock owner (the principal that created 474 a lock can always perform an UNLOCK). While the set of users who 475 may lock a resource is most commonly the same set of users who may 476 modify a resource, servers may allow various kinds of 477 administrators to unlock resources locked by others. Any privilege 478 controlling access by non-lock owners to UNLOCK MUST be aggregated 479 under DAV:unlock. 480 A lock owner can always remove a lock by issuing an UNLOCK with 481 the correct lock token and authentication credentials. That is, 482 even if a principal does not have DAV:unlock privilege, they can 483 still remove locks they own. Principals other than the lock owner 484 can remove a lock only if they have DAV:unlock privilege and they 485 issue an UNLOCK with the correct lock token. Lock timeout is not 486 affected by the DAV:unlock privilege. 487 489 3.6 DAV:read-acl Privilege 491 The DAV:read-acl privilege controls the use of PROPFIND to 492 retrieve the DAV:acl property of the resource. 493 495 3.7 DAV:read-current-user-privilege-set Privilege 497 The DAV:read-current-user-privilege-set privilege controls the use 498 of PROPFIND to retrieve the DAV:current-user-privilege-set 499 property of the resource. 500 Clients are intended to use this property to visually indicate in 501 their UI items that are dependent on the permissions of a 502 resource, for example, by graying out resources that are not 503 writeable. 504 This privilege is separate from DAV:read-acl because there is a 505 need to allow most users access to the privileges permitted the 506 current user (due to its use in creating the UI), while the full 507 ACL contains information that may not be appropriate for the 508 current authenticated user. As a result, the set of users who can 509 view the full ACL is expected to be much smaller than those who 510 can read the current user privilege set, and hence distinct 511 privileges are needed for each. 512 514 3.8 DAV:write-acl Privilege 516 The DAV:write-acl privilege controls use of the ACL method to 517 modify the DAV:acl property of the resource. 518 520 3.9 DAV:bind Privilege 522 The DAV:bind privilege allows a method to add a new member URL to 523 the specified collection (for example via PUT or MKCOL). It is 524 ignored for resources that are not collections. 525 527 3.10DAV:unbind Privilege 529 The DAV:unbind privilege allows a method to remove a member URL 530 from the specified collection (for example via DELETE or MOVE). 531 It is ignored for resources that are not collections. 532 534 3.11 DAV:all Privilege 536 DAV:all is an aggregate privilege that contains the entire set of 537 privileges that can be applied to the resource. 538 540 3.12 Aggregation of Predefined Privileges 542 Server implementations are free to aggregate the predefined 543 privileges (defined above in Sections 3.1-3.9) subject to the 544 following limitations: 545 DAV:read-acl MUST NOT contain DAV:read, DAV:write, DAV:write-acl, 546 DAV:write-properties, DAV:write-content, or DAV:read-current-user- 547 privilege-set. 548 DAV:write-acl MUST NOT contain DAV:write, DAV:read, DAV:read-acl, 549 or DAV:read-current-user-privilege-set. 550 DAV:read-current-user-privilege-set MUST NOT contain DAV:write, 551 DAV:read, DAV:read-acl, or DAV:write-acl. 552 DAV:write MUST NOT contain DAV:read, DAV:read-acl, or DAV:read- 553 current-user-privilege-set. 554 DAV:read MUST NOT contain DAV:write, DAV:write-acl, DAV:write- 555 properties, or DAV:write-content. 557 DAV:write MUST contain DAV:write-properties and DAV:write-content. 559 4 PRINCIPAL PROPERTIES 561 Principals are manifested to clients as a WebDAV resource, 562 identified by a URL. A principal MUST have a non-empty 563 DAV:displayname property (defined in Section 13.2 of [RFC2518]), 564 and a DAV:resourcetype property (defined in Section 13.9 of 565 [RFC2518]). Additionally, a principal MUST report the 566 DAV:principal XML element in the value of the DAV:resourcetype 567 property. The element type declaration for DAV:principal is: 568 570 This protocol defines the following additional properties for a 571 principal. Since it can be expensive for a server to retrieve 572 access control information, the name and value of these properties 573 SHOULD NOT be returned by a PROPFIND allprop request (as defined 574 in Section 12.14.1 of [RFC2518]). 576 4.1 DAV:alternate-URI-set 578 This protected property, if non-empty, contains the URIs of 579 network resources with additional descriptive information about 580 the principal. This property identifies additional network 581 resources (i.e., it contains one or more URIs) that may be 582 consulted by a client to gain additional knowledge concerning a 583 principal. One expected use for this property is the storage of an 584 LDAP [RFC2255] scheme URL. A user-agent encountering an LDAP URL 585 could use LDAP [RFC2589] to retrieve additional machine-readable 586 directory information about the principal, and display that 587 information in its user interface. Support for this property is 588 REQUIRED, and the value is empty if no alternate URI exists for 589 the principal. 590 592 4.2 DAV:principal-URL 594 A principal may have many URLs, but there must be one "principal 595 URL" that clients can use to uniquely identify a principal. This 596 protected property contains the URL that MUST be used to identify 597 this principal in an ACL request. Support for this property is 598 REQUIRED. 599 601 4.3 DAV:group-member-set 603 This property of a group principal identifies the principals that 604 are direct members of this group. Since a group may be a member of 605 another group, a group may also have indirect members (i.e. the 606 members of its direct members). A URL in the DAV:group-member-set 607 for a principal MUST be the DAV:principal-URL of that principal. 608 609 4.4 DAV:group-membership 611 This protected property identifies the groups in which the 612 principal is directly a member. Note that a server may allow a 613 group to be a member of another group, in which case the 614 DAV:group-membership of those other groups would need to be 615 queried in order to determine the groups in which the principal is 616 indirectly a member. Support for this property is REQUIRED. 617 619 5 ACCESS CONTROL PROPERTIES 621 This specification defines a number of new properties for WebDAV 622 resources. Access control properties may be retrieved just like 623 other WebDAV properties, using the PROPFIND method. Since it is 624 expensive, for many servers, to retrieve access control 625 information, a PROPFIND allprop request (as defined in Section 626 12.14.1 of [RFC2518]) SHOULD NOT return the names and values of 627 the properties defined in this section. 628 Access control properties (especially DAV:acl and DAV:inherited- 629 acl-set) are defined on the resource identified by the Request-URI 630 of a PROPFIND request. A direct consequence is that if the 631 resource is accessible via multiple URI, the value of access 632 control properties is the same across these URI. 633 HTTP resources that support the WebDAV Access Control Protocol 634 MUST contain the following properties. Null resources (described 635 in Section 3 of [RFC2518]) MUST NOT contain the following 636 properties. 638 5.1 DAV:owner 640 This protected property identifies a particular principal as being 641 the "owner" of the resource. Since the owner of a resource often 642 has special access control capabilities (e.g., the owner 643 frequently has permanent DAV:write-acl privilege), clients might 644 display the resource owner in their user interface. 646 648 5.1.1 Example: Retrieving DAV:owner 650 This example shows a client request for the value of the DAV:owner 651 property from a collection resource with URL 652 http://www.example.com/papers/. The principal making the request 653 is authenticated using Digest authentication. The value of 654 DAV:owner is the URL http://www.example.com/acl/users/gstein, 655 wrapped in the DAV:href XML element. 656 >> Request << 657 PROPFIND /papers/ HTTP/1.1 658 Host: www.example.com 659 Content-type: text/xml; charset="utf-8" 660 Content-Length: xxx 661 Depth: 0 662 Authorization: Digest username="jim", 663 realm="jim@webdav.org", nonce="...", 664 uri="/papers/", response="...", opaque="..." 666 667 668 669 670 671 673 >> Response << 675 HTTP/1.1 207 Multi-Status 676 Content-Type: text/xml; charset="utf-8" 677 Content-Length: xxx 679 680 681 682 http://www.example.com/papers/ 683 684 685 687 http://www.example.com/acl/users/gstein 688 689 690 HTTP/1.1 200 OK 691 692 693 695 5.1.2 Example: An Attempt to Set DAV:owner 697 The following example shows a client request to modify the value 698 of the DAV:owner property on the resource with URL 699 . Since DAV:owner is a protected 700 property, the server responds with a 207 (Multi-Status) response 701 that contains a 403 (Forbidden) status code for the act of setting 702 DAV:owner. Section 8.2.1 of [RFC2518] describes PROPPATCH status 703 code information, and Section 11 of [RFC2518] describes the Multi- 704 Status response. 705 >> Request << 707 PROPPATCH /papers/ HTTP/1.1 708 Host: www.example.com 709 Content-type: text/xml; charset="utf-8" 710 Content-Length: xxx 711 Depth: 0 712 Authorization: Digest username="jim", 713 realm="jim@webdav.org", nonce="...", 714 uri="/papers/", response="...", opaque="..." 716 717 718 719 720 721 http://www.example.com/acl/users/jim 722 723 724 725 727 >> Response << 729 HTTP/1.1 207 Multi-Status 730 Content-Type: text/xml; charset="utf-8" 731 Content-Length: xxx 733 734 735 736 http://www.example.com/papers/ 737 738 739 HTTP/1.1 403 Forbidden 740 741 Failure to set protected property (DAV:owner) 742 743 744 745 747 5.2 DAV:supported-privilege-set 749 This is a protected property that identifies the privileges 750 defined for the resource. 751 753 Each privilege appears as an XML element, where aggregate 754 privileges list as sub-elements all of the privileges that they 755 aggregate. 756 758 759 An abstract privilege MUST NOT be used in an ACE for that 760 resource. Servers MUST fail an attempt to set an abstract 761 privilege. 763 765 A description is a human-readable description of what this 766 privilege controls access to. Servers MUST indicate the human 767 language of the description using the xml:lang attribute and 768 SHOULD consider the HTTP Accept-Language request header when 769 selecting one of multiple available languages. 771 773 It is envisioned that a WebDAV ACL-aware administrative client 774 would list the supported privileges in a dialog box, and allow the 775 user to choose non-abstract privileges to apply in an ACE. The 776 privileges tree is useful programmatically to map well-known 777 privileges (defined by WebDAV or other standards groups) into 778 privileges that are supported by any particular server 779 implementation. The privilege tree also serves to hide complexity 780 in implementations allowing large number of privileges to be 781 defined by displaying aggregates to the user. 783 5.2.1 Example: Retrieving a List of Privileges Supported on a Resource 785 This example shows a client request for the DAV:supported- 786 privilege-set property on the resource 787 http://www.example.com/papers/. The value of the DAV:supported- 788 privilege-set property is a tree of supported privileges (using 789 "[XML Namespace , localname]" to identify each privilege): 790 [DAV:, all] (aggregate, abstract) 791 | 792 +-- [DAV:, read] (aggregate) 793 | 794 +-- [DAV:, read-acl] (abstract) 795 +-- [DAV:, read-current-user-privilege-set] 796 (abstract) 797 | 798 +-- [DAV:, write] (aggregate) 799 | 800 +-- [DAV:, write-acl] (abstract) 801 +-- [DAV:, write-properties] 802 +-- [DAV:, write-content] 803 | 804 +-- [DAV:, unlock] 806 This privilege tree is not normative (except that it reflects the 807 normative aggregation rules given in Section 3.12), and many 808 possible privilege trees are possible. 810 >> Request << 811 PROPFIND /papers/ HTTP/1.1 812 Host: www.example.com 813 Content-type: text/xml; charset="utf-8" 814 Content-Length: xxx 815 Depth: 0 816 Authorization: Digest username="gclemm", 817 realm="gclemm@webdav.org", nonce="...", 818 uri="/papers/", response="...", opaque="..." 820 821 822 823 824 825 827 >> Response << 829 HTTP/1.1 207 Multi-Status 830 Content-Type: text/xml; charset="utf-8" 831 Content-Length: xxx 833 834 835 836 http://www.example.com/papers/ 837 838 839 840 841 842 843 844 Any operation 845 846 847 848 Read any object 849 850 851 852 853 Read ACL 854 855 856 857 858 859 860 861 Read current user privilege set property 862 863 864 865 866 867 868 Write any object 869 870 871 872 Write ACL 873 874 875 876 877 878 Write properties 879 880 881 882 883 Write resource content 884 885 886 887 888 889 Unlock resource 890 891 892 893 894 HTTP/1.1 200 OK 895 896 897 899 5.3 DAV:current-user-privilege-set 901 DAV:current-user-privilege-set is a protected property containing 902 the exact set of privileges (as computed by the server) granted to 903 the currently authenticated HTTP user. Aggregate privileges and 904 their contained privileges are listed. A user-agent can use the 905 value of this property to adjust its user interface to make 906 actions inaccessible (e.g., by graying out a menu item or button) 907 for which the current principal does not have permission. This 908 property is also useful for determining what operations the 909 current principal can perform, without having to actually execute 910 an operation. 912 913 915 If the current user is granted a specific privilege, that 916 privilege must belong to the set of privileges that may be set on 917 this resource. Therefore, each element in the DAV:current-user- 918 privilege-set property MUST identify a non-abstract privilege from 919 the DAV:supported-privilege-set property. 921 5.3.1 Example: Retrieving the User's Current Set of Assigned Privileges 923 Continuing the example from Section 5.2.1, this example shows a 924 client requesting the DAV:current-user-privilege-set property from 925 the resource with URL http://www.example.com/papers/. The username 926 of the principal making the request is "khare", and Digest 927 authentication is used in the request. The principal with username 928 "khare" has been granted the DAV:read privilege. Since the 929 DAV:read privilege contains the DAV:read-acl and DAV:read-current- 930 user-privilege-set privileges (see Section 5.2.1), the principal 931 with username "khare" can read the ACL property, and the 932 DAV:current-user-privilege-set property. However, the DAV:all, 933 DAV:read-acl, DAV:write-acl and DAV:read-current-user-privilege- 934 set privileges are not listed in the value of DAV:current-user- 935 privilege-set, since (for this example) they are abstract 936 privileges. DAV:write is not listed since the principal with 937 username "khare" is not listed in an ACE granting that principal 938 write permission. 939 >> Request << 941 PROPFIND /papers/ HTTP/1.1 942 Host: www.example.com 943 Content-type: text/xml; charset="utf-8" 944 Content-Length: xxx 945 Depth: 0 946 Authorization: Digest username="khare", 947 realm="khare@webdav.org", nonce="...", 948 uri="/papers/", response="...", opaque="..." 950 951 952 953 954 955 957 >> Response << 959 HTTP/1.1 207 Multi-Status 960 Content-Type: text/xml; charset="utf-8" 961 Content-Length: xxx 963 964 965 966 http://www.example.com/papers/ 967 968 969 970 971 972 973 HTTP/1.1 200 OK 974 975 976 978 5.4 DAV:acl 980 This is a protected property that specifies the list of access 981 control entries (ACEs), which define what principals are to get 982 what privileges for this resource. 984 986 Each DAV:ace element specifies the set of privileges to be either 987 granted or denied to a single principal. If the DAV:acl property 988 is empty, no principal is granted any privilege. 990 993 5.4.1 ACE Principal 995 The DAV:principal element identifies the principal to which this 996 ACE applies. 998 1002 The current user matches DAV:href only if that user is 1003 authenticated as being (or being a member of) the principal 1004 identified by the URL contained by that DAV:href. 1005 The current user always matches DAV:all. 1006 1008 The current user matches DAV:authenticated only if authenticated. 1009 1011 The current user matches DAV:unauthenticated only if not 1012 authenticated. 1013 1015 DAV:all is the union of DAV:authenticated, and 1016 DAV:unauthenticated. For a given request, the user matches either 1017 DAV:authenticated, or DAV:unauthenticated, but not both (that is, 1018 DAV:authenticated and DAV:unauthenticated are disjoint sets). 1019 The current user matches a DAV:property principal in a DAV:acl 1020 property of a resource only if the value of the identified 1021 property of that resource contains at most one DAV:href XML 1022 element, the URI value of DAV:href identifies a principal, and the 1023 current user is authenticated as being (or being a member of) that 1024 principal. For example, if the DAV:property element contained 1025 , the current user would match the DAV:property 1026 principal only if the current user is authenticated as matching 1027 the principal identified by the DAV:owner property of the 1028 resource. 1029 1031 The current user matches DAV:self in a DAV:acl property of the 1032 resource only if that resource is a principal and that principal 1033 matches the current user or, if the principal is a group, a member 1034 of that group matches the current user. 1035 1037 Some servers may support ACEs applying to those users 1038 NOT matching the current principal, e.g. all users not in a 1039 particular group. This can be done by wrapping the DAV:principal 1040 element with DAV:invert. 1041 1043 5.4.2 ACE Grant and Deny 1045 Each DAV:grant or DAV:deny element specifies the set of privileges 1046 to be either granted or denied to the specified principal. A 1047 DAV:grant or DAV:deny element of the DAV:acl of a resource MUST 1048 only contain non-abstract elements specified in the DAV:supported- 1049 privilege-set of that resource. 1051 1052 1053 1055 5.4.3 ACE Protection 1057 A server indicates an ACE is protected by including the 1058 DAV:protected element in the ACE. If the ACL of a resource 1059 contains an ACE with a DAV:protected element, an attempt to remove 1060 that ACE from the ACL MUST fail. 1062 1064 5.4.4 ACE Inheritance 1066 The presence of a DAV:inherited element indicates that this ACE is 1067 inherited from another resource that is identified by the URL 1068 contained in a DAV:href element. An inherited ACE cannot be 1069 modified directly, but instead the ACL on the resource from which 1070 it is inherited must be modified. 1072 Note that ACE inheritance is not the same as ACL initialization. 1073 ACL initialization defines the ACL that a newly created resource 1074 will use (if not specified). ACE inheritance refers to an ACE 1075 that is logically shared - where an update to the resource 1076 containing an ACE will affect the ACE of each resource that 1077 inherits that ACE. The method by which ACLs are initialized or by 1078 which ACEs are inherited is not defined by this document. 1079 1081 5.4.5 Example: Retrieving a Resource's Access Control List 1083 Continuing the example from Sections 5.2.1 and 5.3.1, this example 1084 shows a client requesting the DAV:acl property from the resource 1085 with URL http://www.example.com/papers/. There are two ACEs 1086 defined in this ACL: 1087 ACE #1: The group identified by URL 1088 http://www.example.com/acl/groups/maintainers (the group of site 1089 maintainers) is granted DAV:write privilege. Since (for this 1090 example) DAV:write contains the DAV:write-acl privilege (see 1091 Section 5.2.1), this means the "maintainers" group can also modify 1092 the access control list. 1093 ACE #2: All principals (DAV:all) are granted the DAV:read 1094 privilege. Since (for this example) DAV:read contains DAV:read-acl 1095 and DAV:read-current-user-privilege-set, this means all users 1096 (including all members of the "maintainers" group) can read the 1097 DAV:acl property and the DAV:current-user-privilege-set property. 1099 >> Request << 1101 PROPFIND /papers/ HTTP/1.1 1102 Host: www.example.com 1103 Content-type: text/xml; charset="utf-8" 1104 Content-Length: xxx 1105 Depth: 0 1106 Authorization: Digest username="masinter", 1107 realm="webdav.org", nonce="...", 1108 uri="/papers/", response="...", opaque="..." 1110 1111 1112 1113 1114 1116 >> Response << 1118 HTTP/1.1 207 Multi-Status 1119 Content-Type: text/xml; charset="utf-8" 1120 Content-Length: xxx 1122 1123 1124 http://www.example.com/papers/ 1125 1126 1127 1128 1129 1130 http://www.example.com/acl/groups/maintainers 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 HTTP/1.1 200 OK 1147 1148 1149 1151 5.5 DAV: acl-restrictions 1153 This protected property defines the types of ACLs supported by 1154 this server, to avoid clients needlessly getting errors. When a 1155 client tries to set an ACL via the ACL method, the server may 1156 reject the attempt to set the ACL as specified. The following 1157 properties indicate the restrictions the client must observe 1158 before setting an ACL: 1159 Deny ACEs are not supported 1160 Inverted ACEs are not supported 1161 All deny ACEs must occur before any grant 1162 ACEs 1163 Indicates which principals are 1164 required to be present 1166 1169 5.5.1 DAV:grant-only 1171 This element indicates that ACEs with deny clauses are not 1172 allowed. 1174 1176 5.5.2 DAV:no-invert ACE Constraint 1178 This element indicates that ACEs with the element are not 1179 allowed. 1180 1182 5.5.3 DAV:deny-before-grant 1184 This element indicates that all deny ACEs must precede all grant 1185 ACEs. 1186 1188 5.5.4 Required Principals 1190 The required principal elements identify which principals must 1191 have an ACE defined in the ACL. 1192 1196 For example, the following element requires that the ACL contain a 1197 DAV:owner property ACE: 1198 1199 1200 1202 Example: Retrieving DAV:acl-restrictions 1204 In this example, the client requests the value of the DAV:acl- 1205 restrictions property. Digest authentication provides credentials 1206 for the principal operating the client. 1208 >> Request << 1210 PROPFIND /papers/ HTTP/1.1 1211 Host: www.example.com 1212 Content-type: text/xml; charset="utf-8" 1213 Content-Length: xxx 1214 Depth: 0 1215 Authorization: Digest username="srcarter", 1216 realm="srcarter@webdav.org", nonce="...", 1217 uri="/papers/", response="...", opaque="..." 1219 1220 1221 1222 1223 1224 1226 >> Response << 1228 HTTP/1.1 207 Multi-Status 1229 Content-Type: text/xml; charset="utf-8" 1230 Content-Length: xxx 1232 1233 1234 1235 http://www.example.com/papers/ 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 HTTP/1.1 200 OK 1246 1247 1248 1250 5.6 DAV:inherited-acl-set 1252 This protected property contains a set of URLs that identify other 1253 resources that also control the access to this resource. To have 1254 a privilege on a resource, not only must the ACL on that resource 1255 (specified in the DAV:acl property of that resource) grant the 1256 privilege, but so must the ACL of each resource identified in the 1257 DAV:inherited-acl-set property of that resource. Effectively, the 1258 privileges granted by the current ACL are ANDed with the 1259 privileges granted by each inherited ACL. 1260 1262 5.7 DAV:principal-collection-set 1264 This protected property of a resource contains a set of URLs that 1265 identify the root collections that contain the principals that are 1266 available on the server that implements this resource. A WebDAV 1267 Access Control Protocol user agent could use the contents of 1268 DAV:principal-collection-set to retrieve the DAV:displayname 1269 property (specified in Section 13.2 of [RFC2518]) of all 1270 principals on that server, thereby yielding human-readable names 1271 for each principal that could be displayed in a user interface. 1272 1273 Since different servers can control different parts of the URL 1274 namespace, different resources on the same host MAY have different 1275 DAV:principal-collection-set values. The collections specified in 1276 the DAV:principal-collection-set MAY be located on different hosts 1277 from the resource. The URLs in DAV:principal-collection-set SHOULD 1278 be http or https scheme URLs. For security and scalability 1279 reasons, a server MAY report only a subset of the entire set of 1280 known principal collections, and therefore clients should not 1281 assume they have retrieved an exhaustive listing. Additionally, a 1282 server MAY elect to report none of the principal collections it 1283 knows about, in which case the property value would be empty. 1284 The value of DAV:principal-collection-set gives the scope of the 1285 DAV:principal-property-search REPORT (defined in Section 9.4). 1286 Clients use the DAV:principal-property-search REPORT to populate 1287 their user interface with a list of principals. Therefore, servers 1288 that limit a client's ability to obtain principal information will 1289 interfere with the client's ability to manipulate access control 1290 lists, due to the difficulty of getting the URL of a principal for 1291 use in an ACE. 1293 5.7.1 Example: Retrieving DAV:principal-collection-set 1295 In this example, the client requests the value of the 1296 DAV:principal-collection-set property on the collection resource 1297 identified by URL http://www.example.com/papers/. The property 1298 contains the two URLs, http://www.example.com/acl/users/ and 1299 http://www.example.com/acl/groups/, both wrapped in DAV:href XML 1300 elements. Digest authentication provides credentials for the 1301 principal operating the client. 1302 The client might reasonably follow this request with two separate 1303 PROPFIND requests to retrieve the DAV:displayname property of the 1304 members of the two collections (/acl/users and /acl/groups). This 1305 information could be used when displaying a user interface for 1306 creating access control entries. 1308 >> Request << 1310 PROPFIND /papers/ HTTP/1.1 1311 Host: www.example.com 1312 Content-type: text/xml; charset="utf-8" 1313 Content-Length: xxx 1314 Depth: 0 1315 Authorization: Digest username="yarong", 1316 realm="yarong@webdav.org", nonce="...", 1317 uri="/papers/", response="...", opaque="..." 1319 1320 1321 1322 1323 1324 1325 >> Response << 1327 HTTP/1.1 207 Multi-Status 1328 Content-Type: text/xml; charset="utf-8" 1329 Content-Length: xxx 1331 1332 1333 1334 http://www.example.com/papers/ 1335 1336 1337 1338 http://www.example.com/acl/users/ 1339 http://www.example.com/acl/groups/ 1340 1341 1342 HTTP/1.1 200 OK 1343 1344 1345 1347 5.8 Example: PROPFIND to retrieve access control properties 1349 The following example shows how access control information can be 1350 retrieved by using the PROPFIND method to fetch the values of the 1351 DAV:owner, DAV:supported-privilege-set, DAV:current-user- 1352 privilege-set, and DAV:acl properties. 1353 >> Request << 1355 PROPFIND /top/container/ HTTP/1.1 1356 Host: www.example.com 1357 Content-type: text/xml; charset="utf-8" 1358 Content-Length: xxx 1359 Depth: 0 1360 Authorization: Digest username="ejw", 1361 realm="users@foo.org", nonce="...", 1362 uri="/top/container/", response="...", opaque="..." 1364 1365 1366 1367 1368 1369 1370 1371 1372 1374 >> Response << 1376 HTTP/1.1 207 Multi-Status 1377 Content-Type: text/xml; charset="utf-8" 1378 Content-Length: xxx 1380 1381 1384 http://www.example.com/top/container/ 1385 1386 1387 1388 http://www.example.com/users/gclemm 1389 1390 1391 1392 1393 1394 Any operation 1395 1396 1397 Read any 1398 object 1399 1400 1401 1402 1403 Write any 1404 object 1405 1406 1407 Create an 1408 object 1409 1410 1411 1412 Update an 1413 object 1414 1415 1416 1417 Remove binding to an 1418 object 1419 1420 1421 1422 1423 Read the 1424 ACL 1425 1426 1427 1428 Write the 1429 ACL 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 http://www.example.com/users/esedlar 1441 1442 1443 1444 1445 1446 1447 1448 1449 http://www.example.com/groups/marketing 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 http://www.example.com/top 1467 1468 1469 1470 HTTP/1.1 200 OK 1471 1473 The value of the DAV:owner property is a single DAV:href XML 1474 element containing the URL of the principal that owns this 1475 resource. 1476 The value of the DAV:supported-privilege-set property is a tree of 1477 supported privileges (using "[XML Namespace , localname]" to 1478 identify each privilege): 1480 [DAV:, all] (aggregate, abstract) 1481 | 1482 +-- [DAV:, read] 1483 +-- [DAV:, write] (aggregate, abstract) 1484 | 1485 +-- [http://www.example.com/acl, create] 1486 +-- [http://www.example.com/acl, update] 1487 +-- [http://www.example.com/acl, delete] 1488 +-- [DAV:, read-acl] 1489 +-- [DAV:, write-acl] 1491 The DAV:current-user-privilege-set property contains two 1492 privileges, DAV:read, and DAV:read-acl. This indicates that the 1493 current authenticated user only has the ability to read the 1494 resource, and read the DAV:acl property on the resource. 1495 The DAV:acl property contains a set of four ACEs: 1496 ACE #1: The principal identified by the URL 1497 http://www.example.com/users/esedlar is granted the DAV:read, 1498 DAV:write, and DAV:read-acl privileges. 1499 ACE #2: The principals identified by the URL 1500 http://www.example.com/groups/marketing are denied the DAV:read 1501 privilege. In this example, the principal URL identifies a group. 1502 ACE #3: In this ACE, the principal is a property principal, 1503 specifically the DAV:owner property. When evaluating this ACE, the 1504 value of the DAV:owner property is retrieved, and is examined to 1505 see if it contains a DAV:href XML element. If so, the URL within 1506 the DAV:href element is read, and identifies a principal. In this 1507 ACE, the owner is granted DAV:read-acl, and DAV:write-acl 1508 privileges. 1509 ACE #4: This ACE grants the DAV:all principal (all users) the 1510 DAV:read privilege. This ACE is inherited from the resource 1511 http://www.example.com/top, the parent collection of this 1512 resource. 1514 6 ACL EVALUATION 1516 WebDAV ACLs are evaluated in similar manner as ACLs on Windows NT 1517 and in NFSv4 [NFSV4]). An ACL is evaluated to determine whether 1518 or not access will be granted for a WebDAV request. ACEs are 1519 maintained in a particular order, and are evaluated until all of 1520 the permissions required by the current request have been granted, 1521 at which point the ACL evaluation is terminated and access is 1522 granted. If, during ACL evaluation, a ACE (matching the 1523 current user) is encountered for a privilege which has not yet 1524 been granted, the ACL evaluation is terminated and access is 1525 denied. Failure to have all required privileges granted results 1526 in access being denied. 1528 Note that the semantics of many other existing ACL systems may be 1529 represented via this mechanism, by mixing deny and grant ACEs. 1530 For example, consider the standard "rwx" privilege scheme used by 1531 UNIX. In this scheme, if the current user is the owner of the 1532 file, access is granted if the corresponding privilege bit is set 1533 and denied if not set, regardless of the permissions set on the 1534 file�s group and for the world. An ACL for UNIX permissions of 1535 "r--rw-r--"might be constructed like: 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 and the would be defined as: 1564 1565 1566 1567 1568 1569 1570 Note that the client can still get errors from a UNIX server in 1571 spite of obeying the , including (adding an ACE specifying a principal other than the 1573 ones in the ACL above) or (by trying to reorder 1574 the ACEs in the example above), as these particular implementation 1575 semantics are too complex to be captured with the simple (but 1576 general) declarative restrictions. 1578 7 ACCESS CONTROL AND EXISTING METHODS 1580 This section defines the impact of access control functionality on 1581 existing methods. 1583 7.1 ANY HTTP METHOD 1585 7.1.1 Error Handling 1587 The WebDAV ACL mechanism requires the usage of HTTP method 1588 "preconditions" as described in section 1.6 of RFC3253 for ALL 1589 HTTP methods. All HTTP methods have an additional precondition 1590 called DAV:need-privileges. If an HTTP method fails due to 1591 insufficient privileges, the response body to the "403 Forbidden" 1592 error MUST contain the element, which in turn contains 1593 the element, which contains one or more 1594 elements indicating which resource had insufficient 1595 privileges, and what the lacking privileges were: 1596 1597 1599 Since some methods require multiple permissions on multiple 1600 resources, this information is needed to resolve any ambiguity. 1601 There is no requirement that all privilege violations be reported� 1602 for implementation reasons, some servers may only report the first 1603 privilege violation. For example: 1605 >> Request << 1607 MOVE /a/b/ HTTP/1.1 1608 Host: www.example.com 1609 Destination: http://www.example.com/c/d 1611 >> Response << 1613 HTTP/1.1 403 Forbidden 1614 Content-Type: text/xml; charset="utf-8" 1615 Content-Length: xxx 1617 1618 1619 1620 /a 1621 1622 1623 1624 /c 1625 1626 1627 1628 1630 7.2 OPTIONS 1632 If the server supports access control, it MUST return "access- 1633 control" as a field in the DAV response header from an OPTIONS 1634 request on any resource implemented by that server. A value of 1635 "access-control" in the DAV header MUST indicate that the server 1636 supports all MUST level requirements and REQUIRED features 1637 specified in this document. 1639 7.2.1 Example - OPTIONS 1641 >> Request << 1643 OPTIONS /foo.html HTTP/1.1 1644 Host: www.example.com 1645 Content-Length: 0 1647 >> Response << 1649 HTTP/1.1 200 OK 1650 DAV: 1, 2, access-control 1651 Allow: OPTIONS, GET, PUT, PROPFIND, PROPPATCH, ACL 1653 In this example, the OPTIONS response indicates that the server 1654 supports access control and that /foo.html can have its access 1655 control list modified by the ACL method. 1657 7.3 MOVE 1659 When a resource is moved from one location to another due to a 1660 MOVE request, the non-inherited and non-protected ACEs in the 1661 DAV:acl property of the resource MUST NOT be modified, or the MOVE 1662 request fails. Handling of inherited and protected ACEs is 1663 intentionally undefined to give server implementations flexibility 1664 in how they implement ACE inheritance and protection. 1666 7.4 COPY 1668 The DAV:acl property on the resource at the destination of a COPY 1669 MUST be the same as if the resource was created by an individual 1670 resource creation request (e.g. MKCOL, PUT). Clients wishing to 1671 preserve the DAV:acl property across a copy need to read the 1672 DAV:acl property prior to the COPY, then perform an ACL operation 1673 on the new resource at the destination to restore, insofar as this 1674 is possible, the original access control list. 1676 7.5 LOCK 1678 A lock on a resource ensures that only the lock owner can modify 1679 ACEs that are not inherited and not protected (these are the only 1680 ACEs that a client can modify with an ACL request). A lock does 1681 not protect inherited or protected ACEs, since a client cannot 1682 modify them with an ACL request on that resource. 1684 8 ACCESS CONTROL METHODS 1686 8.1 ACL 1688 The ACL method modifies the access control list (which can be read 1689 via the DAV:acl property) of a resource. Specifically, the ACL 1690 method only permits modification to ACEs that are not inherited, 1691 and are not protected. An ACL method invocation modifies all non- 1692 inherited and non-protected ACEs in a resource's access control 1693 list to exactly match the ACEs contained within in the DAV:acl XML 1694 element (specified in Section 5.4) of the request body. An ACL 1695 request body MUST contain only one DAV:acl XML element. Unless the 1696 non-inherited and non-protected ACEs of the DAV:acl property of 1697 the resource can be updated to be exactly the value specified in 1698 the ACL request, the ACL request MUST fail. 1699 It is possible that the ACEs visible to the current user in the 1700 DAV:acl property may only be a portion of the complete set of ACEs 1701 on that resource. If this is the case, an ACL request only 1702 modifies the set of ACEs visible to the current user, and does not 1703 affect any non-visible ACE. 1704 In order to avoid overwriting DAV:acl changes by another client, a 1705 client SHOULD acquire a WebDAV lock on the resource before 1706 retrieving the DAV:acl property of a resource that it intends on 1707 updating. 1708 Implementation Note: Two common operations are to add or remove 1709 an ACE from an existing access control list. To accomplish 1710 this, a client uses the PROPFIND method to retrieve the value 1711 of the DAV:acl property, then parses the returned access 1712 control list to remove all inherited and protected ACEs (these 1713 ACEs are tagged with the DAV:inherited and DAV:protected XML 1714 elements). In the remaining set of non-inherited, non-protected 1715 ACEs, the client can add or remove one or more ACEs before 1716 submitting the final ACE set in the request body of the ACL 1717 method. 1719 8.1.1 ACL Preconditions 1721 An implementation MUST enforce the following constraints on an ACL 1722 request. If the constraint is violated, a 403 (Forbidden) or 409 1723 (Conflict) response MUST be returned and the indicated XML element 1724 MUST be returned as a child of a top level DAV:error element in an 1725 XML response body. 1726 Though these status elements are generally expressed as empty XML 1727 elements (and are defined as EMPTY in the DTD), implementations 1728 MAY return additional descriptive XML elements as children of the 1729 status element. Clients MUST be able to accept children of these 1730 status elements. Clients that do not understand the additional XML 1731 elements should ignore them. 1732 (DAV:no-ace-conflict): The ACEs submitted in the ACL request MUST 1733 NOT conflict with each other. This is a catchall error code 1734 indicating that an implementation-specific ACL restriction has 1735 been violated. 1736 (DAV:no-protected-ace-conflict): The ACEs submitted in the ACL 1737 request MUST NOT conflict with the protected ACEs on the resource. 1738 For example, if the resource has a protected ACE granting 1739 DAV:write to a given principal, then it would not be consistent if 1740 the ACL request submitted an ACE denying DAV:write to the same 1741 principal. 1742 (DAV:no-inherited-ace-conflict): The ACEs submitted in the ACL 1743 request MUST NOT conflict with the inherited ACEs on the resource. 1744 For example, if the resource inherits an ACE from its parent 1745 collection granting DAV:write to a given principal, then it would 1746 not be consistent if the ACL request submitted an ACE denying 1747 DAV:write to the same principal. Note that reporting of this error 1748 will be implementation-dependent. Implementations MUST either 1749 report this error or allow the ACE to be set, and then let normal 1750 ACE evaluation rules determine whether the new ACE has any impact 1751 on the privileges available to a specific principal. 1752 (DAV:limited-number-of-aces): The number of ACEs submitted in the 1753 ACL request MUST NOT exceed the number of ACEs allowed on that 1754 resource. However, ACL-compliant servers MUST support at least 1755 one ACE granting privileges to a single principal, and one ACE 1756 granting privileges to a group. 1757 (DAV:deny-before-grant): All non-inherited deny ACEs MUST precede 1758 all non-inherited grant ACEs. 1759 (DAV:grant-only): The ACEs submitted in the ACL request MUST NOT 1760 include a deny ACE. This precondition applies only when the ACL 1761 restrictions of the resource include the DAV:grant-only constraint 1762 (defined in Section 5.5.1). 1763 (DAV:no-invert): The ACL request MUST NOT include a DAV:invert 1764 element. This precondition applies only when the ACL semantics 1765 of the resource includes the DAV:no-invert constraint (defined in 1766 Section 6.3.4). 1767 (DAV:no-abstract): The ACL request MUST NOT attempt to grant or 1768 deny an abstract privilege (see Section 5.2). 1769 (DAV:not-supported-privilege): The ACEs submitted in the ACL 1770 request MUST be supported by the resource. 1771 (DAV:missing-required-principal): The result of the ACL request 1772 MUST have at least one ACE for each principal identified in a 1773 DAV:required-principal XML element in the ACL semantics of that 1774 resource (see Section 5.5.4). 1775 (DAV:recognized-principal): Every principal URL in the ACL request 1776 MUST identify a principal resource. 1777 (DAV:allowed-principal): The principals specified in the ACEs 1778 submitted in the ACL request MUST be allowed as principals for the 1779 resource. For example, a server where only authenticated 1780 principals can access resources would not allow the DAV:all or 1781 DAV:unauthenticated principals to be used in an ACE, since these 1782 would allow unauthenticated access to resources. 1784 8.1.2 Example: the ACL method 1786 In the following example, user "fielding", authenticated by 1787 information in the Authorization header, grants the principal 1788 identified by the URL http://www.example.com/users/esedlar (i.e., 1789 the user "esedlar") read and write privileges, grants the owner of 1790 the resource read-acl and write-acl privileges, and grants 1791 everyone read privileges. 1792 >> Request << 1794 ACL /top/container/ HTTP/1.1 1795 Host: www.example.com 1796 Content-Type: text/xml; charset="utf-8" 1797 Content-Length: xxxx 1798 Authorization: Digest username="fielding", 1799 realm="users@foo.org", nonce="...", 1800 uri="/top/container/", response="...", opaque="..." 1802 1803 1804 1805 1806 http://www.example.com/users/esedlar 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1829 >> Response << 1831 HTTP/1.1 200 OK 1833 8.1.3 Example: ACL method failure due to protected ACE conflict 1835 In the following request, user "fielding", authenticated by 1836 information in the Authorization header, attempts to deny the 1837 principal identified by the URL 1838 http://www.example.com/users/esedlar (i.e., the user "esedlar") 1839 write privileges. Prior to the request, the DAV:acl property on 1840 the resource contained a protected ACE (see Section 5.4.3) 1841 granting DAV:owner the DAV:read and DAV:write privileges. The 1842 principal identified by URL http://www.example.com/users/esedlar 1843 is the owner of the resource. The ACL method invocation fails 1844 because the submitted ACE conflicts with the protected ACE, thus 1845 violating the semantics of ACE protection. 1846 >> Request << 1848 ACL /top/container/ HTTP/1.1 1849 Host: www.example.com 1850 Content-Type: text/xml; charset="utf-8" 1851 Content-Length: xxxx 1852 Authorization: Digest username="fielding", 1853 realm="users@foo.org", nonce="...", 1854 uri="/top/container/", response="...", opaque="..." 1856 1857 1858 1859 1860 http://www.example.com/users/esedlar 1861 1862 1863 1864 1865 1866 1868 >> Response << 1870 HTTP/1.1 403 Forbidden 1871 Content-Type: text/xml; charset="utf-8" 1872 Content-Length: xxx 1874 1875 1876 1877 1879 8.1.4 Example: ACL method failure due to an inherited ACE conflict 1881 In the following request, user "ejw", authenticated by information 1882 in the Authorization header, tries to change the access control 1883 list on the resource http://www.example.com/top/index.html. This 1884 resource has two inherited ACEs. 1885 Inherited ACE #1 grants the principal identified by URL 1886 http://www.example.com/users/ejw (i.e., the user "ejw") 1887 http://www.example.com/privs/write-all and DAV:read-acl 1888 privileges. On this server, http://www.example.com/privs/write-all 1889 is an aggregate privilege containing DAV:write, and DAV:write-acl. 1890 Inherited ACE #2 grants principal DAV:all the DAV:read privilege. 1891 The request attempts to set a (non-inherited) ACE, denying the 1892 principal identified by the URL http://www.example.com/users/ejw 1893 (i.e., the user "ejw") DAV:write permission. This conflicts with 1894 inherited ACE #1. Note that the decision to report an inherited 1895 ACE conflict is specific to this server implementation. Another 1896 server implementation could have allowed the new ACE to be set, 1897 and then used normal ACE evaluation rules to determine whether the 1898 new ACE has any impact on the privileges available to a principal. 1899 >> Request << 1901 ACL /top/index.html HTTP/1.1 1902 Host: www.example.com 1903 Content-Type: text/xml; charset="utf-8" 1904 Content-Length: xxxx 1905 Authorization: Digest username="ejw", 1906 realm="users@foo.org", nonce="...", 1907 uri="/top/index.html", response="...", opaque="..." 1909 1910 1911 1912 1913 http://www.example.com/users/ejw 1914 1915 1916 1917 1919 >> Response << 1921 HTTP/1.1 403 Forbidden 1922 Content-Type: text/xml; charset="utf-8" 1923 Content-Length: xxx 1925 1926 1927 1928 1930 8.1.5 Example: ACL method failure due to an attempt to set grant and 1931 deny in a single ACE. 1933 In this example, user "ygoland", authenticated by information in 1934 the Authorization header, tries to change the access control list 1935 on the resource http://www.example.com/diamond/engagement- 1936 ring.gif. The ACL request includes a single, syntactically and 1937 semantically incorrect ACE, which attempts to grant the group 1938 identified by the URL http://www.example.com/users/friends 1939 DAV:read privilege and deny the principal identified by URL 1940 http://www.example.com/users/ygoland-so (i.e., the user "ygoland- 1941 so") DAV:read privilege. However, it is illegal to have multiple 1942 principal elements, as well as both a grant and deny element in 1943 the same ACE, so the request fails due to poor syntax. 1944 >> Request << 1946 ACL /diamond/engagement-ring.gif HTTP/1.1 1947 Host: www.example.com 1948 Content-Type: text/xml; charset="utf-8" 1949 Content-Length: xxxx 1950 Authorization: Digest username="ygoland", 1951 realm="users@foo.org", nonce="...", 1952 uri="/diamond/engagement-ring.gif", response="...", 1953 opaque="..." 1955 1956 1957 1958 1959 http://www.example.com/users/friends 1960 1961 1962 1963 http://www.example.com/users/ygoland-so 1964 1965 1966 1967 1969 >> Response << 1971 HTTP/1.1 400 Bad Request 1972 Content-Length: 0 1974 Note that if the request had been divided into two ACEs, one to 1975 grant, and one to deny, the request would have been syntactically 1976 well formed. 1978 9 ACCESS CONTROL REPORTS 1980 9.1 REPORT Method 1982 The REPORT method (defined in Section 3.6 of [RFC3253]) provides 1983 an extensible mechanism for obtaining information about a 1984 resource. Unlike the PROPFIND method, which returns the value of 1985 one or more named properties, the REPORT method can involve more 1986 complex processing. REPORT is valuable in cases where the server 1987 has access to all of the information needed to perform the complex 1988 request (such as a query), and where it would require multiple 1989 requests for the client to retrieve the information needed to 1990 perform the same request. 1991 A server that supports the WebDAV Access Control Protocol MUST 1992 support the DAV:expand-property report (defined in Section 3.8 of 1993 [RFC3253]). 1995 9.2 DAV:acl-principal-prop-set Report 1997 The DAV:acl-principal-prop-set report returns, for all principals 1998 in the DAV:acl property (of the Request-URI) that are identified 1999 by http(s) URLs or by a DAV:property principal, the value of the 2000 properties specified in the REPORT request body. In the case where 2001 a principal URL appears multiple times, the DAV:acl-principal- 2002 prop-set report MUST return the properties for that principal only 2003 once. Support for this report is REQUIRED. 2004 One expected use of this report is to retrieve the human readable 2005 name (found in the DAV:displayname property) of each principal 2006 found in an ACL. This is useful for constructing user interfaces 2007 that show each ACE in a human readable form. 2008 Marshalling 2009 The request body MUST be a DAV:acl-principal-prop-set XML element. 2010 2011 ANY value: a sequence of one or more elements, with at most one 2012 DAV:prop element. 2013 prop: see RFC 2518, Section 12.11 2015 This report is only defined when the Depth header has value "0"; 2016 other values result in a 400 (Bad Request) error response. Note 2017 that [RFC3253], Section 3.6, states that if the Depth header is 2018 not present, it defaults to a value of "0". 2019 The response body for a successful request MUST be a 2020 DAV:multistatus XML element (i.e., the response uses the same 2021 format as the response for PROPFIND). In the case where there are 2022 no response elements, the returned multistatus XML element is 2023 empty. 2024 multistatus: see RFC 2518, Section 12.9 2026 The response body for a successful DAV:acl-principal-prop-set 2027 REPORT request MUST contain a DAV:response element for each 2028 principal identified by an http(s) URL listed in a DAV:principal 2029 XML element of an ACE within the DAV:acl property of the resource 2030 identified by the Request-URI. 2031 Postconditions: 2032 (DAV:number-of-matches-within-limits): The number of matching 2033 principals must fall within server-specific, predefined limits. 2034 For example, this condition might be triggered if a search 2035 specification would cause the return of an extremely large number 2036 of responses. 2038 9.2.1 Example: DAV:acl-principal-prop-set Report 2040 Resource http://www.example.com/index.html has an ACL with three 2041 ACEs: 2042 ACE #1: All principals (DAV:all) have DAV:read and DAV:read- 2043 current-user-privilege-set access. 2044 ACE #2: The principal identified by 2045 http://www.example.com/people/gstein (the user "gstein") is 2046 granted DAV:write, DAV:write-acl, DAV:read-acl privileges. 2048 ACE #3: The group identified by 2049 http://www.example.com/groups/authors (the "authors" group) is 2050 granted DAV:write and DAV:read-acl privileges. 2051 The following example shows a DAV:acl-principal-prop-set report 2052 requesting the DAV:displayname property. It returns the value of 2053 DAV:displayname for resources http://www.example.com/people/gstein 2054 and http://www.example.com/groups/authors , but not for DAV:all, 2055 since this is not an http(s) URL. 2057 >> Request << 2059 REPORT /index.html HTTP/1.1 2060 Host: www.example.com 2061 Content-Type: text/xml; charset="utf-8" 2062 Content-Length: xxxx 2063 Depth: 0 2065 2066 2067 2068 2069 2070 2072 >> Response << 2073 HTTP/1.1 207 Multi-Status 2074 Content-Type: text/xml; charset="utf-8" 2075 Content-Length: xxxx 2077 2078 2079 2080 http://www.example.com/people/gstein 2081 2082 2083 Greg Stein 2084 2085 HTTP/1.1 200 OK 2086 2087 2088 2089 http://www.example.com/groups/authors 2090 2091 2092 Site authors 2093 2094 HTTP/1.1 200 OK 2095 2096 2097 2098 9.3 DAV:principal-match REPORT 2100 The DAV:principal-match REPORT is used to identify all members (at 2101 any depth) of the collection identified by the Request-URI that 2102 are principals and that match the current user. In particular, if 2103 the collection contains principals, the report can be used to 2104 identify all members of the collection that match the current 2105 user. Alternatively, if the collection contains resources that 2106 have a property that identifies a principal (e.g. DAV:owner), the 2107 report can be used to identify all members of the collection whose 2108 property identifies a principal that matches the current user. For 2109 example, this report can return all of the resources in a 2110 collection hierarchy that are owned by the current user. Support 2111 for this report is REQUIRED. 2112 Marshalling: 2113 The request body MUST be a DAV:principal-match XML element. 2114 2115 2116 ANY value: an element whose value identifies a property. The 2117 expectation is the value of the named property typically contains 2118 an href element that contains the URI of a principal 2119 2120 prop: see RFC 2518, Section 12.11 2122 This report is only defined when the Depth header has value "0"; 2123 other values result in a 400 (Bad Request) error response. Note 2124 that [RFC3253], Section 3.6, states that if the Depth header is 2125 not present, it defaults to a value of "0". 2126 The response body for a successful request MUST be a 2127 DAV:multistatus XML element. In the case where there are no 2128 response elements, the returned multistatus XML element is empty. 2129 multistatus: see RFC 2518, Section 12.9 2131 The response body for a successful DAV:principal-match REPORT 2132 request MUST contain a DAV:response element for each member of the 2133 collection that matches the current user. When the DAV:principal- 2134 property element is used, a match occurs if the current user is 2135 matched by the principal identified by the URI found in the 2136 DAV:href element of the property identified by the DAV:principal- 2137 property element. When the DAV:self element is used in a 2138 DAV:principal-match report issued against a group, it matches the 2139 group if a member identifies the same principal as the current 2140 user. 2141 If DAV:prop is specified in the request body, the properties 2142 specified in the DAV:prop element MUST be reported in the 2143 DAV:response elements. 2145 9.3.1 Example: DAV:principal-match REPORT 2147 The following example identifies the members of the collection 2148 identified by the URL http://www.example.com/doc that are owned by 2149 the current user. The current user ("gclemm") is authenticated 2150 using Digest authentication. 2151 >> Request << 2152 REPORT /doc/ HTTP/1.1 2153 Host: www.example.com 2154 Authorization: Digest username="gclemm", 2155 realm="gclemm@webdav.org", nonce="...", 2156 uri="/papers/", response="...", opaque="..." 2157 Content-Type: text/xml; charset="utf-8" 2158 Content-Length: xxxx 2159 Depth: 0 2161 2162 2163 2164 2165 2166 2168 >> Response << 2170 HTTP/1.1 207 Multi-Status 2171 Content-Type: text/xml; charset="utf-8" 2172 Content-Length: xxxx 2174 2175 2176 2177 http://www.example.com/doc/foo.html 2178 HTTP/1.1 200 OK 2179 2180 2181 http://www.example.com/doc/img/bar.gif 2182 HTTP/1.1 200 OK 2183 2184 2186 9.4 DAV:principal-property-search REPORT 2188 The DAV:principal-property-search REPORT performs a search for all 2189 principals whose properties contain character data that matches 2190 the search criteria specified in the request. One expected use of 2191 this report is to discover the URL of a principal associated with 2192 a given person or group by searching for them by name. This is 2193 done by searching over DAV:displayname, which is defined on all 2194 principals. 2195 The actual search method (exact matching vs. substring matching 2196 vs, prefix-matching, case-sensitivity) deliberately is left to the 2197 server implementation to allow implementation on a wide set of 2198 possible user management systems. In cases where the 2199 implementation of DAV:principal-property-search is not constrained 2200 by the semantics of an underlying user management repository, 2201 preferred default semantics are caseless substring matches. 2202 For implementation efficiency, servers do not typically support 2203 searching on all properties. A search requesting properties that 2204 are not searchable for a particular principal will not match that 2205 principal. 2206 Support for the DAV:principal-property-search report is REQUIRED. 2207 Implementation Note: The value of a WebDAV property is a 2208 sequence of well-formed XML, and hence can include any 2209 character in the Unicode/ISO-10646 standard, that is, most 2210 known characters in human languages. Due to the idiosyncrasies 2211 of case mapping across human languages, implementation of case- 2212 insensitive matching is non-trivial. Implementors of servers 2213 that do perform substring matching are strongly encouraged to 2214 consult [CaseMap], especially Section 2.3 ("Caseless 2215 Matching"), for guidance when implementing their case- 2216 insensitive matching algorithms. 2217 Implementation Note: Some implementations of this protocol will 2218 use an LDAP repository for storage of principal metadata. The 2219 schema describing each attribute (akin to a WebDAV property) in 2220 an LDAP repository specifies whether it supports case-sensitive 2221 or caseless searching. One of the benefits of leaving the 2222 search method to the discretion of the server implementation is 2223 the default LDAP attribute search behavior can be used when 2224 implementing the DAV:principal-property-search report. 2225 Marshalling: 2226 The request body MUST be a DAV:principal-property-search XML 2227 element containing a search specification and an optional list of 2228 properties. For every principal that matches the search 2229 specification, the response will contain the value of the 2230 requested properties on that principal. 2231 2234 By default, the report searches all members (at any depth) of the 2235 collection identified by the Request-URI. If DAV:apply-to- 2236 principal-collection-set is specified in the request body, the 2237 request is applied instead to each collection identified by the 2238 DAV:prinicipal-collection-set property of the resource identified 2239 by the Request-URI. 2240 The DAV:property-search element contains a prop element 2241 enumerating the properties to be searched and a match element, 2242 containing the search string. 2243 2244 prop: see RFC 2518, Section 12.11 2245 2247 Multiple property-search elements or multiple elements within a 2248 DAV:prop element will be interpreted with a logical AND. 2249 This report is only defined when the Depth header has value "0"; 2250 other values result in a 400 (Bad Request) error response. Note 2251 that [RFC3253], Section 3.6, states that if the Depth header is 2252 not present, it defaults to a value of "0". 2253 The response body for a successful request MUST be a 2254 DAV:multistatus XML element. In the case where there are no 2255 response elements, the returned multistatus XML element is empty. 2256 multistatus: see RFC 2518, Section 12.9 2258 The response body for a successful DAV:principal-property-search 2259 REPORT request MUST contain a DAV:response element for each 2260 principal whose property values satisfy the search specification 2261 given in DAV:principal-property-search. 2262 The response body for an unsuccessful DAV:principal-property- 2263 search REPORT request MUST contain, after the XML element 2264 indicating the failed precondition or postcondition, a DAV:prop 2265 element containing the property that caused the pre/postcondition 2266 to fail. 2267 If DAV:prop is specified in the request body, the properties 2268 specified in the DAV:prop element MUST be reported in the 2269 DAV:response elements. 2270 Preconditions: 2271 None 2272 Postconditions: 2273 (DAV:number-of-matches-within-limits): The number of matching 2274 principals must fall within server-specific, predefined limits. 2275 For example, this condition might be triggered if a search 2276 specification would cause the return of an extremely large number 2277 of responses. 2279 9.4.1 Matching 2281 There are several cases to consider when matching strings. The 2282 easiest case is when a property value is "simple" and has only 2283 character information item content (see [REC-XML-INFOSET]). For 2284 example, the search string "julian" would match the 2285 DAV:displayname property with value "Julian Reschke". Note that 2286 the on-the-wire marshalling of DAV:displayname in this case is: 2287 Julian Reschke 2289 The name of the property is encoded into the XML element 2290 information item, and the character information item content of 2291 the property is "Julian Reschke". 2293 A more complicated case occurs when properties have mixed content 2294 (that is, compound values consisting of multiple child element 2295 items, other types of information items, and character information 2296 item content). Consider the property "aprop" in the namespace 2297 "http://www.example.com/props/", marshalled as: 2298 2299 {cdata 0}{cdata 1} 2300 {cdata 2}{cdata 3} 2301 2303 In this case, matching is performed on each individual contiguous 2304 sequence of character information items. In the example above, a 2305 search string would be compared to the four following strings: 2306 {cdata 0} 2307 {cdata 1} 2308 {cdata 2} 2309 {cdata 3} 2311 That is, four individual matches would be performed, one each for 2312 {cdata 0}, {cdata 1}, {cdata 2}, and {cdata 3}. 2314 9.4.2 Example: successful DAV:principal-property-search REPORT 2316 In this example, the client requests the principal URLs of all 2317 users whose DAV:displayname property contains the substring "doE" 2318 and whose "title" property in the namespace 2319 "http://BigCorp.com/ns/" (that is, their professional title) 2320 contains "Sales". In addition, the client requests five 2321 properties to be returned with the matching principals: 2322 In the DAV: namespace: displayname 2323 In the http://www.example.com/ns/ namespace: department, phone, 2324 office, salary 2325 The response shows that two principal resources meet the search 2326 specification, "John Doe" and "Zygdoebert Smith". The property 2327 "salary" in namespace "http://www.example.com/ns/" is not 2328 returned, since the principal making the request does not have 2329 sufficient access permissions to read this property. 2330 >> Request << 2331 REPORT /users/ HTTP/1.1 2332 Host: www.example.com 2333 Content-Type: text/xml; charset=utf-8 2334 Content-Length: xxxx 2335 Depth: 0 2337 2338 2339 2340 2341 2342 2343 doE 2344 2345 2346 2347 2348 2349 Sales 2350 2351 2352 2353 2354 2355 2356 2357 2358 2360 >> Response << 2362 HTTP/1.1 207 Multi-Status 2363 Content-Type: text/xml; charset=utf-8 2364 Content-Length: xxxx 2366 2367 2368 2369 http://www.example.com/users/jdoe 2370 2371 2372 John Doe 2373 Widget Sales 2374 234-4567 2375 209 2376 2377 HTTP/1.1 200 OK 2378 2379 2380 2381 2382 2383 HTTP/1.1 403 Forbidden 2384 2385 2386 2387 http://www.example.com/users/zsmith 2388 2389 2390 Zygdoebert Smith 2391 Gadget Sales 2392 234-7654 2393 114 2394 2395 HTTP/1.1 200 OK 2396 2397 2398 2399 2400 2401 HTTP/1.1 403 Forbidden 2402 2403 2404 2406 9.5 DAV:principal-search-property-set REPORT 2408 The DAV:principal-search-property-set REPORT identifies those 2409 properties that may be searched using the DAV:principal-property- 2410 search REPORT (defined in Section 9.4). 2411 Servers MUST support the DAV:principal-search-property-set REPORT 2412 on all collections identified in the value of a DAV:principal- 2413 collection-set property. 2414 An access control protocol user agent could use the results of the 2415 DAV:principal-search-property-set REPORT to present a query 2416 interface to the user for retrieving principals. 2417 Support for this report is REQUIRED. 2418 Implementation Note: Some clients will have only limited screen 2419 real estate for the display of lists of searchable properties. 2420 In this case, a user might appreciate having the most 2421 frequently searched properties be displayed on-screen, rather 2422 than having to scroll through a long list of searchable 2423 properties. One mechanism for signaling the most frequently 2424 searched properties is to return them towards the start of a 2425 list of properties. A client can then preferentially display 2426 the list of properties in order, increasing the likelihood that 2427 the most frequently searched properties will appear on-screen, 2428 and will not require scrolling for their selection. 2429 Marshalling: 2430 The request body MUST be an empty DAV:principal-search-property- 2431 set XML element. 2432 This report is only defined when the Depth header has value "0"; 2433 other values result in a 400 (Bad Request) error response. Note 2434 that [RFC3253], Section 3.6, states that if the Depth header is 2435 not present, it defaults to a value of "0". 2436 The response body MUST be a DAV:principal-search-property-set XML 2437 element, containing a DAV:principal-search-property XML element 2438 for each property that may be searched with the DAV:principal- 2439 property-search REPORT. A server MAY limit its response to just a 2440 subset of the searchable properties, such as those likely to be 2441 useful to an interactive access control client. 2443 2446 Each DAV:principal-search-property XML element contains exactly 2447 one searchable property, and a description of the property. 2448 2450 The DAV:prop element contains one principal property on which the 2451 server is able to perform a DAV:principal-property-search REPORT. 2452 prop: see RFC 2518, Section 12.11 2454 The description element is a human-readable description of what 2455 information this property represents. Servers MUST indicate the 2456 human language of the description using the xml:lang attribute and 2457 SHOULD consider the HTTP Accept-Language request header when 2458 selecting one of multiple available languages. 2459 2461 9.5.1 Example: DAV:principal-search-property-set REPORT 2463 In this example, the client determines the set of searchable 2464 principal properties by requesting the DAV:principal-search- 2465 property-set REPORT on the root of the server's principal URL 2466 collection set, identified by http://www.example.com/users/. 2467 >> Request << 2468 REPORT /users/ HTTP/1.1 2469 Host: www.example.com 2470 Content-Type: text/xml; charset="utf-8" 2471 Content-Length: xxx 2472 Accept-Language: en, de 2473 Authorization: BASIC d2FubmFtYWs6cGFzc3dvcmQ= 2474 Depth: 0 2476 2477 2479 >> Response << 2480 HTTP/1.1 200 OK 2481 Content-Type: text/xml; charset="utf-8" 2482 Content-Length: xxx 2484 2485 2486 2487 2488 2489 2490 Full name 2491 2492 2493 2494 2495 2496 Job title 2497 2498 2500 10 XML PROCESSING 2502 Implementations of this specification MUST support the XML element 2503 ignore rule, as specified in Section 23.3.2 of [RFC2518], and the 2504 XML Namespace recommendation [REC-XML-NAMES]. 2505 Note that use of the DAV namespace is reserved for XML elements 2506 and property names defined in a standards-track or Experimental 2507 IETF RFC. 2509 11 INTERNATIONALIZATION CONSIDERATIONS 2511 In this specification, the only human-readable content can be 2512 found in the description XML element, found within the 2513 DAV:supported-privilege-set property. This element contains a 2514 human-readable description of the capabilities controlled by a 2515 privilege. As a result, the description element must be capable 2516 of representing descriptions in multiple character sets. Since 2517 the description element is found within a WebDAV property, it is 2518 represented on the wire as XML [REC-XML], and hence can leverage 2519 XML's language tagging and character set encoding capabilities. 2520 Specifically, XML processors at minimum must be able to read XML 2521 elements encoded using the UTF-8 [UTF-8] encoding of the ISO 10646 2522 multilingual plane. XML examples in this specification demonstrate 2523 use of the charset parameter of the Content-Type header, as 2524 defined in [RFC3023], as well as the XML "encoding" attribute, 2525 which together provide charset identification information for MIME 2526 and XML processors. Futhermore, this specification requires server 2527 implementations to tag description fields with the xml:lang 2528 attribute (see Section 2.12 of [REC-XML]), which specifies the 2529 human language of the description. Additionally, server 2530 implementations should take into account the value of the Accept- 2531 Language HTTP header to determine which description string to 2532 return. 2533 For XML elements other than the description element, it is 2534 expected that implementations will treat the property names, 2535 privilege names, and values as tokens, and convert these tokens 2536 into human-readable text in the user's language and character set 2537 when displayed to a person. Only a generic WebDAV property 2538 display utility would display these values in their raw form to a 2539 human user. 2540 For error reporting, we follow the convention of HTTP/1.1 status 2541 codes, including with each status code a short, English 2542 description of the code (e.g., 200 (OK)). While the possibility 2543 exists that a poorly crafted user agent would display this message 2544 to a user, internationalized applications will ignore this 2545 message, and display an appropriate message in the user's language 2546 and character set. 2547 Further internationalization considerations for this protocol are 2548 described in the WebDAV Distributed Authoring protocol 2549 specification [RFC2518]. 2551 12 SECURITY CONSIDERATIONS 2553 Applications and users of this access control protocol should be 2554 aware of several security considerations, detailed below. In 2555 addition to the discussion in this document, the security 2556 considerations detailed in the HTTP/1.1 specification [RFC2616], 2557 the WebDAV Distributed Authoring Protocol specification [RFC2518], 2558 and the XML Media Types specification [RFC3023] should be 2559 considered in a security analysis of this protocol. 2561 12.1 Increased Risk of Compromised Users 2563 In the absence of a mechanism for remotely manipulating access 2564 control lists, if a single user's authentication credentials are 2565 compromised, only those resources for which the user has access 2566 permission can be read, modified, moved, or deleted. With the 2567 introduction of this access control protocol, if a single 2568 compromised user has the ability to change ACLs for a broad range 2569 of other users (e.g., a super-user), the number of resources that 2570 could be altered by a single compromised user increases. This risk 2571 can be mitigated by limiting the number of people who have write- 2572 acl privileges across a broad range of resources. 2574 12.2 Risks of the DAV:read-acl and DAV:current-user-privilege-set 2575 Privileges 2577 The ability to read the access privileges (stored in the DAV:acl 2578 property), or the privileges permitted the currently authenticated 2579 user (stored in the DAV:current-user-privilege-set property) on a 2580 resource may seem innocuous, since reading an ACL cannot possibly 2581 affect the resource's state. However, if all resources have world- 2582 readable ACLs, it is possible to perform an exhaustive search for 2583 those resources that have inadvertently left themselves in a 2584 vulnerable state, such as being world-writeable. In particular, 2585 the property retrieval method PROPFIND, executed with Depth 2586 infinity on an entire hierarchy, is a very efficient way to 2587 retrieve the DAV:acl or DAV:current-user-privilege-set properties. 2588 Once found, this vulnerability can be exploited by a denial of 2589 service attack in which the open resource is repeatedly 2590 overwritten. Alternately, writeable resources can be modified in 2591 undesirable ways. 2592 To reduce this risk, read-acl privileges should not be granted to 2593 unauthenticated principals, and restrictions on read-acl and read- 2594 current-user-privilege-set privileges for authenticated principals 2595 should be carefully analyzed when deploying this protocol. Access 2596 to the current-user-privilege-set property will involve a tradeoff 2597 of usability versus security. When the current-user-privilege-set 2598 is visible, user interfaces are expected to provide enhanced 2599 information concerning permitted and restricted operations, yet 2600 this information may also indicate a vulnerability that could be 2601 exploited. Deployment of this protocol will need to evaluate this 2602 tradeoff in light of the requirements of the deployment 2603 environment. 2605 12.3 No Foreknowledge of Initial ACL 2607 In an effort to reduce protocol complexity, this protocol 2608 specification intentionally does not address the issue of how to 2609 manage or discover the initial ACL that is placed upon a resource 2610 when it is created. The only way to discover the initial ACL is to 2611 create a new resource, then retrieve the value of the DAV:acl 2612 property. This assumes the principal creating the resource also 2613 has been granted the DAV:read-acl privilege. 2614 As a result, it is possible that a principal could create a 2615 resource, and then discover that its ACL grants privileges that 2616 are undesirable. Furthermore, this protocol makes it possible 2617 (though unlikely) that the creating principal could be unable to 2618 modify the ACL, or even delete the resource. Even when the ACL can 2619 be modified, there will be a short period of time when the 2620 resource exists with the initial ACL before its new ACL can be 2621 set. 2622 Several factors mitigate this risk. Human principals are often 2623 aware of the default access permissions in their editing 2624 environments and take this into account when writing information. 2625 Furthermore, default privilege policies are usually very 2626 conservative, limiting the privileges granted by the initial ACL. 2628 13 AUTHENTICATION 2630 Authentication mechanisms defined for use with HTTP and WebDAV 2631 also apply to this WebDAV Access Control Protocol, in particular 2632 the Basic and Digest authentication mechanisms defined in 2633 [RFC2617]. Implementation of the ACL spec requires that Basic 2634 authentication, if used, MUST only be supported over secure 2635 transport such as TLS. 2637 14 IANA CONSIDERATIONS 2639 This document uses the namespace defined by [RFC2518] for XML 2640 elements. That is, this specification uses the "DAV:" URI 2641 namespace, previously registered in the URI schemes registry. All 2642 other IANA considerations mentioned in [RFC2518] are also 2643 applicable to this specification. 2645 15 INTELLECTUAL PROPERTY 2647 The following notice is copied from RFC 2026, section 10.4, and 2648 describes the position of the IETF concerning intellectual 2649 property claims made against this document. 2650 The IETF takes no position regarding the validity or scope of any 2651 intellectual property or other rights that might be claimed to 2652 pertain to the implementation or use other technology described in 2653 this document or the extent to which any license under such rights 2654 might or might not be available; neither does it represent that it 2655 has made any effort to identify any such rights. Information on 2656 the IETF's procedures with respect to rights in standards-track 2657 and standards-related documentation can be found in BCP-11. Copies 2658 of claims of rights made available for publication and any 2659 assurances of licenses to be made available, or the result of an 2660 attempt made to obtain a general license or permission for the use 2661 of such proprietary rights by implementers or users of this 2662 specification can be obtained from the IETF Secretariat. 2663 The IETF invites any interested party to bring to its attention 2664 any copyrights, patents or patent applications, or other 2665 proprietary rights that may cover technology that may be required 2666 to practice this standard. Please address the information to the 2667 IETF Executive Director. 2669 16 ACKNOWLEDGEMENTS 2671 This protocol is the collaborative product of the WebDAV ACL 2672 design team: Bernard Chester, Geoff Clemm, Anne Hopkins, Barry 2673 Lind, Sean Lyndersay, Eric Sedlar, Greg Stein, and Jim Whitehead. 2674 The authors are grateful for the detailed review and comments 2675 provided by Jim Amsden, Dylan Barrell, Gino Basso, Murthy 2676 Chintalapati, Lisa Dusseault, Stefan Eissing, Tim Ellison, Yaron 2677 Goland, Dennis Hamilton, Laurie Harper, Eckehard Hermann, Ron 2678 Jacobs, Chris Knight, Remy Maucherat, Larry Masinter, Joe Orton, 2679 Peter Raymond, Julian Reschke, and Keith Wannamaker. We thank 2680 Keith Wannamaker for the initial text of the principal property 2681 search sections. Prior work on WebDAV access control protocols has 2682 been performed by Yaron Goland, Paul Leach, Lisa Dusseault, Howard 2683 Palmer, and Jon Radoff. We would like to acknowledge the 2684 foundation laid for us by the authors of the DeltaV, WebDAV and 2685 HTTP protocols upon which this protocol is layered, and the 2686 invaluable feedback from the WebDAV working group. 2688 17 REFERENCES 2690 17.1 Normative References 2692 [RFC2119] S.Bradner, "Key words for use in RFCs to Indicate 2693 Requirement Levels." RFC 2119, BCP 14, March, 1997. 2694 [REC-XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible 2695 Markup Language (XML)." World Wide Web Consortium Recommendation 2696 REC-xml.http://www.w3.org/TR/REC-xml 2698 [REC-XML-NAMES] T. Bray, D. Hollander, A. Layman, "Name Spaces in 2699 XML" World Wide Web Consortium Recommendation REC-xml-names. 2700 http://www.w3.org/TR/REC-xml-names/ 2701 [RFC3253] G. Clemm, J. Amsden, T. Ellison, C. Kaler, J. Whitehead, 2702 "Versioning Extensions to WebDAV." RFC 3253, March 2002. 2703 [REC-XML-INFOSET] J. Cowan, R. Tobin, "XML Information Set." World 2704 Wide Web Consortium Recommendation REC-xml-infoset. 2705 http://www.w3.org/TR/xml-infoset/ 2706 [RFC2616] R. Fielding, J. Gettys, J. C. Mogul, H. Frystyk, L. 2707 Masinter, P. Leach, and T. Berners-Lee, "Hypertext Transfer 2708 Protocol -- HTTP/1.1." RFC 2616, June, 1999. 2709 [RFC2617] J. Franks, P. Hallam-Baker, J. Hostetler, S. Lawrence, 2710 P. Leach, A. Luotonen, L. Stewart, "HTTP Authentication: Basic and 2711 Digest Access Authentication." RFC 2617, June, 1999. 2712 [RFC2518] Y. Goland, E. Whitehead, A. Faizi, S. R. Carter, D. 2713 Jensen, "HTTP Extensions for Distributed Authoring -- WEBDAV." RFC 2714 2518, February, 1999. 2715 [RFC2368] P. Hoffman, L. Masinter, J. Zawinski, "The mailto URL 2716 scheme." RFC 2368, July, 1998. 2717 [RFC3023] M. Murata, S. St.Laurent, D. Kohn, "XML Media Types." 2718 RFC 3023, January, 2001. 2719 [RFC3010] S. Shepler, B. Callaghan, D. Robinson, R. Thurlow, C. 2720 Beame, M. Eisler, D.Noveck "NFS version 4 Protocol." RFC 3010, 2721 December 2000. 2722 [UTF-8] F. Yergeau, "UTF-8, a transformation format of Unicode 2723 and ISO 10646." RFC 2279, January, 1998. 2725 17.2 Informational References 2727 [RFC2026] S.Bradner, "The Internet Standards Process - Revision 2728 3." RFC 2026, BCP 9. Harvard, October, 1996. 2729 [RFC2255] T. Howes, M. Smith, "The LDAP URL Format." RFC 2255. 2730 Netscape, December, 1997. 2731 [RFC2251] M. Wahl, T. Howes, S. Kille, "Lightweight Directory 2732 Access Protocol (v3)." RFC 2251. Critical Angle, Netscape, Isode, 2733 December, 1997. 2734 [CaseMap] M. Davis, "Case Mappings", Unicode Standard Annex #21, 2735 March 26, 2001. http://www.unicode.org/unicode/reports/tr21 2736 18 AUTHORS' ADDRESSES 2738 Geoffrey Clemm 2739 IBM 2740 20 Maguire Road 2741 Lexington, MA 02421 2742 Email: geoffrey.clemm@us.ibm.com 2744 Anne Hopkins 2745 Microsoft Corporation 2746 One Microsoft Way 2747 Redmond, WA 98052 2748 Email: annehop@microsoft.com 2750 Eric Sedlar 2751 Oracle Corporation 2752 500 Oracle Parkway 2753 Redwood Shores, CA 94065 2754 Email: eric.sedlar@oracle.com 2756 Jim Whitehead 2757 U.C. Santa Cruz 2758 Dept. of Computer Science 2759 Baskin Engineering 2760 1156 High Street 2761 Santa Cruz, CA 95064 2762 Email: ejw@cse.ucsc.edu 2763 19 APPENDICES 2765 19.1 WebDAV XML Document Type Definition Addendum 2767 All XML elements defined in this Document Type Definition (DTD) 2768 belong to the DAV namespace. This DTD should be viewed as an 2769 addendum to the DTD provided in [RFC2518], section 23.1. 2770 2786 2788 2789 2790 2791 2793 2795 2797 2799 2801 2802 2805 2806 2807 2809 2811 2812 2814 2815 2818 2822 2823 2824 2825 2826 2828 2830 2831 2832 2834 2836 2838 2840 2843 2844 2845 2847 2850 2852 2854 2856 2858 2860 2861 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2878 2880 2881 ANY value: a sequence of one or more elements, with at most one 2882 DAV:prop element. 2884 2885 2886 ANY value: an element whose value identifies a property. The 2887 expectation is the value of the named property typically contains 2888 an href element that contains the URI of a principal 2889 2891 2892 2893 2895 2897 2898 2900 19.2 WebDAV Method Privilege Table (Normative) 2902 The following table of WebDAV methods (as defined in RFC 2518, 2616, 2903 and 3253) clarifies which privileges are required for access for each 2904 method. Note that the privileges listed, if denied, MUST cause access 2905 to be denied. However, given that a specific implementation MAY define 2906 an additional custom privilege to control access to existing methods, 2907 having all of the indicated privileges does not mean that access will 2908 be granted. Note that lack of the indicated privileges does not imply 2909 that access will be denied, since a particular implementation may use a 2910 sub-privilege aggregated under the indicated privilege to control 2911 access. Privileges required refer to the current resource being 2912 processed unless otherwise specified. 2914 METHOD PRIVILEGES 2915 GET 2916 HEAD 2917 OPTIONS 2918 PUT (target exists) on target resource 2919 PUT (no target exists) on parent collection of target 2920 PROPPATCH 2921 ACL 2922 PROPFIND (plus and 2923 as needed) 2924 COPY (target exists) , and on target resource 2926 COPY (no target exists) , on target collection 2927 MOVE (no target exists) on source collection and 2928 on target collection 2929 MOVE (target exists) As above, plus on the target 2930 collection 2931 DELETE on parent collection 2932 LOCK (target exists) 2933 LOCK (no target exists) on parent collection 2934 MKCOL on parent collection 2935 UNLOCK 2936 CHECKOUT 2937 CHECKIN 2938 REPORT (on all referenced resources) 2939 VERSION-CONTROL 2940 MERGE 2941 MKWORKSPACE on parent collection 2942 BASELINE-CONTROL and 2943 MKACTIVITY on parent collection