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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group G. Clemm 3 Internet-Draft IBM 4 Updates: 4918 (if approved) J. Crawford 5 Intended status: Standards Track IBM Research 6 Expires: April 6, 2009 J. Reschke, Ed. 7 greenbytes 8 J. Whitehead 9 U.C. Santa Cruz 10 October 3, 2008 12 Binding Extensions to Web Distributed Authoring and Versioning (WebDAV) 13 draft-ietf-webdav-bind-21 15 Status of this Memo 17 By submitting this Internet-Draft, each author represents that any 18 applicable patent or other IPR claims of which he or she is aware 19 have been or will be disclosed, and any of which he or she becomes 20 aware will be disclosed, in accordance with Section 6 of BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF), its areas, and its working groups. Note that 24 other groups may also distribute working documents as Internet- 25 Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 The list of current Internet-Drafts can be accessed at 33 http://www.ietf.org/ietf/1id-abstracts.txt. 35 The list of Internet-Draft Shadow Directories can be accessed at 36 http://www.ietf.org/shadow.html. 38 This Internet-Draft will expire on April 6, 2009. 40 Abstract 42 This specification defines bindings, and the BIND method for creating 43 multiple bindings to the same resource. Creating a new binding to a 44 resource causes at least one new URI to be mapped to that resource. 45 Servers are required to insure the integrity of any bindings that 46 they allow to be created. 48 Editorial Note (To be removed by RFC Editor before publication) 50 Please send comments to the Distributed Authoring and Versioning 51 (WebDAV) working group at , which may be 52 joined by sending a message with subject "subscribe" to 53 . Discussions of the WEBDAV 54 working group are archived at 55 . 57 lists 58 all registered issues since draft 02. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 63 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 64 1.2. Method Preconditions and Postconditions . . . . . . . . . 7 65 2. Overview of Bindings . . . . . . . . . . . . . . . . . . . . . 7 66 2.1. Bindings to Collections . . . . . . . . . . . . . . . . . 8 67 2.1.1. Bind Loops . . . . . . . . . . . . . . . . . . . . . . 9 68 2.2. URI Mappings Created by a new Binding . . . . . . . . . . 9 69 2.3. COPY and Bindings . . . . . . . . . . . . . . . . . . . . 10 70 2.3.1. Example: COPY with 'Depth: infinity' in Presence 71 of Bind Loops . . . . . . . . . . . . . . . . . . . . 12 72 2.3.2. Example: COPY with 'Depth: infinity' with Multiple 73 Bindings to a Leaf Resource . . . . . . . . . . . . . 14 74 2.4. DELETE and Bindings . . . . . . . . . . . . . . . . . . . 15 75 2.5. MOVE and Bindings . . . . . . . . . . . . . . . . . . . . 15 76 2.5.1. Example: Simple MOVE . . . . . . . . . . . . . . . . . 16 77 2.5.2. Example: MOVE Request causing a Bind Loop . . . . . . 16 78 2.6. PROPFIND and Bindings . . . . . . . . . . . . . . . . . . 18 79 2.7. Determining Whether Two Bindings Are to the Same 80 Resource . . . . . . . . . . . . . . . . . . . . . . . . . 18 81 2.8. Discovering the Bindings to a Resource . . . . . . . . . . 19 82 3. Properties . . . . . . . . . . . . . . . . . . . . . . . . . . 19 83 3.1. DAV:resource-id Property . . . . . . . . . . . . . . . . . 19 84 3.2. DAV:parent-set Property . . . . . . . . . . . . . . . . . 20 85 3.2.1. Example for DAV:parent-set Property . . . . . . . . . 20 86 4. BIND Method . . . . . . . . . . . . . . . . . . . . . . . . . 21 87 4.1. Example: BIND . . . . . . . . . . . . . . . . . . . . . . 24 88 5. UNBIND Method . . . . . . . . . . . . . . . . . . . . . . . . 24 89 5.1. Example: UNBIND . . . . . . . . . . . . . . . . . . . . . 26 90 6. REBIND Method . . . . . . . . . . . . . . . . . . . . . . . . 26 91 6.1. Example: REBIND . . . . . . . . . . . . . . . . . . . . . 28 92 6.2. Example: REBIND in Presence of Locks and Bind Loops . . . 29 93 7. Additional Status Codes . . . . . . . . . . . . . . . . . . . 31 94 7.1. 208 Already Reported . . . . . . . . . . . . . . . . . . . 31 95 7.1.1. Example: PROPFIND by Bind-Aware Client . . . . . . . . 32 96 7.1.2. Example: PROPFIND by Non-Bind-Aware Client . . . . . . 34 97 7.2. 506 Loop Detected . . . . . . . . . . . . . . . . . . . . 34 98 8. Capability Discovery . . . . . . . . . . . . . . . . . . . . . 34 99 8.1. OPTIONS Method . . . . . . . . . . . . . . . . . . . . . . 34 100 8.2. 'DAV' Request Header . . . . . . . . . . . . . . . . . . . 34 101 9. Relationship to WebDAV Access Control Protocol . . . . . . . . 35 102 10. Security Considerations . . . . . . . . . . . . . . . . . . . 35 103 10.1. Privacy Concerns . . . . . . . . . . . . . . . . . . . . . 35 104 10.2. Bind Loops . . . . . . . . . . . . . . . . . . . . . . . . 35 105 10.3. Bindings, and Denial of Service . . . . . . . . . . . . . 35 106 10.4. Private Locations May Be Revealed . . . . . . . . . . . . 36 107 10.5. DAV:parent-set and Denial of Service . . . . . . . . . . . 36 108 11. Internationalization Considerations . . . . . . . . . . . . . 36 109 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 110 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 36 111 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 37 112 14.1. Normative References . . . . . . . . . . . . . . . . . . . 37 113 14.2. Informative References . . . . . . . . . . . . . . . . . . 37 114 Appendix A. Clarification to RFC2518bis' Usage of the term 115 'lock root' . . . . . . . . . . . . . . . . . . . . . 37 116 Appendix B. Change Log (to be removed by RFC Editor before 117 publication) . . . . . . . . . . . . . . . . . . . . 38 118 B.1. Since draft-ietf-webdav-bind-02 . . . . . . . . . . . . . 38 119 B.2. Since draft-ietf-webdav-bind-03 . . . . . . . . . . . . . 38 120 B.3. Since draft-ietf-webdav-bind-04 . . . . . . . . . . . . . 38 121 B.4. Since draft-ietf-webdav-bind-05 . . . . . . . . . . . . . 39 122 B.5. Since draft-ietf-webdav-bind-06 . . . . . . . . . . . . . 39 123 B.6. Since draft-ietf-webdav-bind-07 . . . . . . . . . . . . . 39 124 B.7. Since draft-ietf-webdav-bind-08 . . . . . . . . . . . . . 39 125 B.8. Since draft-ietf-webdav-bind-09 . . . . . . . . . . . . . 39 126 B.9. Since draft-ietf-webdav-bind-10 . . . . . . . . . . . . . 39 127 B.10. Since draft-ietf-webdav-bind-11 . . . . . . . . . . . . . 40 128 B.11. Since draft-ietf-webdav-bind-12 . . . . . . . . . . . . . 40 129 B.12. Since draft-ietf-webdav-bind-13 . . . . . . . . . . . . . 40 130 B.13. Since draft-ietf-webdav-bind-14 . . . . . . . . . . . . . 40 131 B.14. Since draft-ietf-webdav-bind-15 . . . . . . . . . . . . . 41 132 B.15. Since draft-ietf-webdav-bind-16 . . . . . . . . . . . . . 41 133 B.16. Since draft-ietf-webdav-bind-17 . . . . . . . . . . . . . 41 134 B.17. Since draft-ietf-webdav-bind-18 . . . . . . . . . . . . . 41 135 B.18. Since draft-ietf-webdav-bind-19 . . . . . . . . . . . . . 41 136 B.19. Since draft-ietf-webdav-bind-20 . . . . . . . . . . . . . 41 137 Appendix C. Open issues (to be removed by RFC Editor prior to 138 publication) . . . . . . . . . . . . . . . . . . . . 41 139 C.1. edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 140 C.2. status-codes . . . . . . . . . . . . . . . . . . . . . . . 42 141 C.3. relation-to-deltav . . . . . . . . . . . . . . . . . . . . 42 142 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 143 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 44 144 Intellectual Property and Copyright Statements . . . . . . . . . . 46 146 1. Introduction 148 This specification extends the WebDAV Distributed Authoring Protocol 149 ([RFC4918]) to enable clients to create new access paths to existing 150 resources. This capability is useful for several reasons: 152 URIs of WebDAV-compliant resources are hierarchical and correspond to 153 a hierarchy of collections in resource space. The WebDAV Distributed 154 Authoring Protocol makes it possible to organize these resources into 155 hierarchies, placing them into groupings, known as collections, which 156 are more easily browsed and manipulated than a single flat 157 collection. However, hierarchies require categorization decisions 158 that locate resources at a single location in the hierarchy, a 159 drawback when a resource has multiple valid categories. For example, 160 in a hierarchy of vehicle descriptions containing collections for 161 cars and boats, a description of a combination car/boat vehicle could 162 belong in either collection. Ideally, the description should be 163 accessible from both. Allowing clients to create new URIs that 164 access the existing resource lets them put that resource into 165 multiple collections. 167 Hierarchies also make resource sharing more difficult, since 168 resources that have utility across many collections are still forced 169 into a single collection. For example, the mathematics department at 170 one university might create a collection of information on fractals 171 that contains bindings to some local resources, but also provides 172 access to some resources at other universities. For many reasons, it 173 may be undesirable to make physical copies of the shared resources on 174 the local server: to conserve disk space, to respect copyright 175 constraints, or to make any changes in the shared resources visible 176 automatically. Being able to create new access paths to existing 177 resources in other collections or even on other servers is useful for 178 this sort of case. 180 The BIND method defined here provides a mechanism for allowing 181 clients to create alternative access paths to existing WebDAV 182 resources. HTTP [RFC2616] and WebDAV [RFC4918] methods are able to 183 work because there are mappings between URIs and resources. A method 184 is addressed to a URI, and the server follows the mapping from that 185 URI to a resource, applying the method to that resource. Multiple 186 URIs may be mapped to the same resource, but until now there has been 187 no way for clients to create additional URIs mapped to existing 188 resources. 190 BIND lets clients associate a new URI with an existing WebDAV 191 resource, and this URI can then be used to submit requests to the 192 resource. Since URIs of WebDAV resources are hierarchical, and 193 correspond to a hierarchy of collections in resource space, the BIND 194 method also has the effect of adding the resource to a collection. 195 As new URIs are associated with the resource, it appears in 196 additional collections. 198 A BIND request does not create a new resource, but simply makes 199 available a new URI for submitting requests to an existing resource. 200 The new URI is indistinguishable from any other URI when submitting a 201 request to a resource. Only one round trip is needed to submit a 202 request to the intended target. Servers are required to enforce the 203 integrity of the relationships between the new URIs and the resources 204 associated with them. Consequently, it may be very costly for 205 servers to support BIND requests that cross server boundaries. 207 This specification is organized as follows. Section 1.1 defines 208 terminology used in the rest of the specification, while Section 2 209 overviews bindings. Section 3 defines the new properties needed to 210 support multiple bindings to the same resource. Section 4 specifies 211 the BIND method, used to create multiple bindings to the same 212 resource. Section 5 specifies the UNBIND method, used to remove a 213 binding to a resource. Section 6 specifies the REBIND method, used 214 to move a binding to another collection. 216 1.1. Terminology 218 The terminology used here follows and extends that in the WebDAV 219 Distributed Authoring Protocol specification [RFC4918]. 221 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 222 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 223 document are to be interpreted as described in [RFC2119]. 225 This document uses XML DTD fragments ([XML]) as a notational 226 convention, using the rules defined in Section 17 of [RFC4918]. 228 URI Mapping 230 A relation between an absolute URI and a resource. For an 231 absolute URI U and the resource it identifies R, the URI mapping 232 can be thought of as (U => R). Since a resource can represent 233 items that are not network retrievable, as well as those that are, 234 it is possible for a resource to have zero, one, or many URI 235 mappings. Mapping a resource to an "http" scheme URI makes it 236 possible to submit HTTP protocol requests to the resource using 237 the URI. 239 Path Segment 240 Informally, the characters found between slashes ("/") in a URI. 241 Formally, as defined in Section 3.3 of [RFC3986]. 243 Binding 245 A relation between a single path segment (in a collection) and a 246 resource. A binding is part of the state of a collection. If two 247 different collections contain a binding between the same path 248 segment and the same resource, these are two distinct bindings. 249 So for a collection C, a path segment S, and a resource R, the 250 binding can be thought of as C:(S -> R). Bindings create URI 251 mappings, and hence allow requests to be sent to a single resource 252 from multiple locations in a URI namespace. For example, given a 253 collection C (accessible through the URI 254 http://www.example.com/CollX), a path segment S (equal to 255 "foo.html"), and a resource R, then creating the binding C: (S -> 256 R) makes it possible to use the URI 257 http://www.example.com/CollX/foo.html to access R. 259 Collection 261 A resource that contains, as part of its state, a set of bindings 262 that identify internal member resources. 264 Internal Member URI 266 The URI that identifies an internal member of a collection, and 267 that consists of the URI for the collection, followed by a slash 268 character ('/'), followed by the path segment of the binding for 269 that internal member. 271 1.2. Method Preconditions and Postconditions 273 See Section 16 of [RFC4918] for the definitions of "precondition" and 274 "postcondition". 276 2. Overview of Bindings 278 Bindings are part of the state of a collection. They define the 279 internal members of the collection, and the names of those internal 280 members. 282 Bindings are added and removed by a variety of existing HTTP methods. 283 A method that creates a new resource, such as PUT, COPY, and MKCOL, 284 adds a binding. A method that deletes a resource, such as DELETE, 285 removes a binding. A method that moves a resource (e.g. MOVE) both 286 adds a binding (in the destination collection) and removes a binding 287 (in the source collection). The BIND method introduced here provides 288 a mechanism for adding a second binding to an existing resource. 289 There is no difference between an initial binding added by PUT, COPY, 290 or MKCOL, and additional bindings added with BIND. 292 It would be very undesirable if one binding could be destroyed as a 293 side effect of operating on the resource through a different binding. 294 In particular, the removal of one binding to a resource (e.g. with a 295 DELETE or a MOVE) MUST NOT disrupt another binding to that resource, 296 e.g. by turning that binding into a dangling path segment. The 297 server MUST NOT reclaim system resources after removing one binding, 298 while other bindings to the resource remain. In other words, the 299 server MUST maintain the integrity of a binding. It is permissible, 300 however, for future method definitions (e.g., a DESTROY method) to 301 have semantics that explicitly remove all bindings and/or immediately 302 reclaim system resources. 304 2.1. Bindings to Collections 306 Creating a new binding to a collection makes each resource associated 307 with a binding in that collection accessible via a new URI, and thus 308 creates new URI mappings to those resources but no new bindings. 310 For example, suppose a new binding CollY is created for collection C1 311 in the figure below. It immediately becomes possible to access 312 resource R1 using the URI /CollY/x.gif and to access resource R2 313 using the URI /CollY/y.jpg, but no new bindings for these child 314 resources were created. This is because bindings are part of the 315 state of a collection, and associate a URI that is relative to that 316 collection with its target resource. No change to the bindings in 317 Collection C1 is needed to make its children accessible using /CollY/ 318 x.gif and /CollY/y.jpg. 320 +-------------------------+ 321 | Root Collection | 322 | bindings: | 323 | CollX CollY | 324 +-------------------------+ 325 | / 326 | / 327 | / 328 +------------------+ 329 | Collection C1 | 330 | bindings: | 331 | x.gif y.jpg | 332 +------------------+ 333 | \ 334 | \ 335 | \ 336 +-------------+ +-------------+ 337 | Resource R1 | | Resource R2 | 338 +-------------+ +-------------+ 340 2.1.1. Bind Loops 342 Bindings to collections can result in loops ("cycles"), which servers 343 MUST detect when processing "Depth: infinity" requests. It is 344 sometimes possible to complete an operation in spite of the presence 345 of a loop. For instance, a PROPFIND can still succeed if the server 346 uses the new status code 208 (Already Reported) defined in 347 Section 7.1. 349 However, the 506 (Loop Detected) status code is defined in 350 Section 7.2 for use in contexts where an operation is terminated 351 because a loop was encountered. 353 Support for loops is OPTIONAL: servers MAY reject requests that would 354 lead to the creation of a bind loop (see DAV:cycle-allowed 355 precondition defined in Section 4). 357 2.2. URI Mappings Created by a new Binding 359 Suppose a binding from "Binding-Name" to resource R is to be added to 360 a collection, C. Then if C-MAP is the set of URIs that were mapped to 361 C before the BIND request, then for each URI "C-URI" in C-MAP, the 362 URI "C-URI/Binding-Name" is mapped to resource R following the BIND 363 request. 365 For example, if a binding from "foo.html" to R is added to a 366 collection C, and if the following URIs are mapped to C: 368 http://www.example.com/A/1/ 369 http://example.com/A/one/ 371 then the following new mappings to R are introduced: 373 http://www.example.com/A/1/foo.html 374 http://example.com/A/one/foo.html 376 Note that if R is a collection, additional URI mappings are created 377 to the descendents of R. Also, note that if a binding is made in 378 collection C to C itself (or to a parent of C), an infinite number of 379 mappings are introduced. 381 For example, if a binding from "myself" to C is then added to C, the 382 following infinite number of additional mappings to C are introduced: 384 http://www.example.com/A/1/myself 385 http://www.example.com/A/1/myself/myself 386 ... 388 and the following infinite number of additional mappings to R are 389 introduced: 391 http://www.example.com/A/1/myself/foo.html 392 http://www.example.com/A/1/myself/myself/foo.html 393 ... 395 2.3. COPY and Bindings 397 As defined in Section 9.8 of [RFC4918], COPY causes the resource 398 identified by the Request-URI to be duplicated, and makes the new 399 resource accessible using the URI specified in the Destination 400 header. Upon successful completion of a COPY, a new binding is 401 created between the last path segment of the Destination header, and 402 the destination resource. The new binding is added to its parent 403 collection, identified by the Destination header minus its final 404 segment. 406 The following figure shows an example: Suppose that a COPY is issued 407 to URI-3 for resource R (which is also mapped to URI-1 and URI-2), 408 with the Destination header set to URI-X. After successful 409 completion of the COPY operation, resource R is duplicated to create 410 resource R', and a new binding has been created which creates at 411 least the URI mapping between URI-X and the new resource (although 412 other URI mappings may also have been created). 414 URI-1 URI-2 URI-3 URI-X 415 | | | | 416 | | | <---- URI Mappings ----> | 417 | | | | 418 +---------------------+ +------------------------+ 419 | Resource R | | Resource R' | 420 +---------------------+ +------------------------+ 422 It might be thought that a COPY request with "Depth: 0" on a 423 collection would duplicate its bindings, since bindings are part of 424 the collection's state. This is not the case, however. The 425 definition of Depth in [RFC4918] makes it clear that a "Depth: 0" 426 request does not apply to a collection's members. Consequently, a 427 COPY with "Depth: 0" does not duplicate the bindings contained by the 428 collection. 430 If a COPY request causes an existing resource to be updated, the 431 bindings to that resource MUST be unaffected by the COPY request. 432 Using the preceding example, suppose that a COPY request is issued to 433 URI-X for resource R', with the Destination header set to URI-2. The 434 content and dead properties of resource R would be updated to be a 435 copy of those of resource R', but the mappings from URI-1, URI-2, and 436 URI-3 to resource R remain unaffected. If because of multiple 437 bindings to a resource, more than one source resource updates a 438 single destination resource, the order of the updates is server 439 defined. 441 If a COPY request would cause a new resource to be created as a copy 442 of an existing resource, and that COPY request has already created a 443 copy of that existing resource, the COPY request instead creates 444 another binding to the previous copy, instead of creating a new 445 resource. 447 2.3.1. Example: COPY with 'Depth: infinity' in Presence of Bind Loops 449 As an example of how COPY with Depth infinity would work in the 450 presence of bindings, consider the following collection: 452 +------------------+ 453 | Root Collection | 454 | bindings: | 455 | CollX | 456 +------------------+ 457 | 458 | 459 +-------------------------------+ 460 | Collection C1 |<-------+ 461 | bindings: | | 462 | x.gif CollY | | 463 +-------------------------------+ | 464 | \ (creates loop) | 465 | \ | 466 +-------------+ +------------------+ | 467 | Resource R1 | | Collection C2 | | 468 +-------------+ | bindings: | | 469 | y.gif CollZ | | 470 +------------------+ | 471 | | | 472 | +--------+ 473 | 474 +-------------+ 475 | Resource R2 | 476 +-------------+ 478 If a COPY with Depth infinity is submitted to /CollX, with 479 destination of /CollA, the outcome of the copy operation is: 481 +------------------+ 482 | Root Collection | 483 | bindings: | 484 | CollX CollA | 485 +------------------+ 486 | | 487 | +---------------------------+ 488 | | 489 +-------------------+ | 490 | Collection C1 |<------------------+ | 491 | bindings: | | | 492 | x.gif CollY | | | 493 +-------------------+ | | 494 | \ (creates loop) | | 495 | \ | | 496 +-------------+ +-----------------+ | | 497 | Resource R1 | | Collection C2 | | | 498 +-------------+ | bindings: | | | 499 | y.gif CollZ | | | 500 +-----------------+ | | 501 | | | | 502 | +-------+ | 503 | | 504 +-------------+ | 505 | Resource R2 | | 506 +-------------+ | 507 | 508 +-------------------------------+ 509 | 510 +-------------------+ 511 | Collection C3 |<------------------+ 512 | bindings: | | 513 | x.gif CollY | | 514 +-------------------+ | 515 | \ (creates loop) | 516 | \ | 517 +-------------+ +-----------------+ | 518 | Resource R3 | | Collection C4 | | 519 +-------------+ | bindings: | | 520 | y.gif CollZ | | 521 +-----------------+ | 522 | | | 523 | +-------+ 524 | 525 +-------------+ 526 | Resource R4 | 527 +-------------+ 529 2.3.2. Example: COPY with 'Depth: infinity' with Multiple Bindings to a 530 Leaf Resource 532 Given the following collection hierarchy: 534 +------------------+ 535 | Root Collection | 536 | bindings: | 537 | CollX | 538 +------------------+ 539 | 540 | 541 | 542 +----------------+ 543 | Collection C1 | 544 | bindings: | 545 | x.gif y.gif | 546 +----------------+ 547 | | 548 | | 549 +-------------+ 550 | Resource R1 | 551 +-------------+ 553 A COPY of /CollX with Depth infinity to /CollY results in the 554 following collection hierarchy: 556 +------------------+ 557 | Root Collection | 558 | bindings: | 559 | CollX CollY | 560 +------------------+ 561 | \ 562 | \ 563 | \ 564 +----------------+ +-----------------+ 565 | Collection C1 | | Collection C2 | 566 | bindings: | | bindings: | 567 | x.gif y.gif | | x.gif y.gif | 568 +----------------+ +-----------------+ 569 | | | | 570 | | | | 571 +-------------+ +-------------+ 572 | Resource R1 | | Resource R2 | 573 +-------------+ +-------------+ 575 2.4. DELETE and Bindings 577 When there are multiple bindings to a resource, a DELETE applied to 578 that resource MUST NOT remove any bindings to that resource other 579 than the one identified by the Request-URI. For example, suppose the 580 collection identified by the URI "/a" has a binding named "x" to a 581 resource R, and another collection identified by "/b" has a binding 582 named "y" to the same resource R. Then a DELETE applied to "/a/x" 583 removes the binding named "x" from "/a" but MUST NOT remove the 584 binding named "y" from "/b" (i.e. after the DELETE, "/y/b" continues 585 to identify the resource R). 587 When DELETE is applied to a collection, it MUST NOT modify the 588 membership of any other collection that is not itself a member of the 589 collection being deleted. For example, if both "/a/.../x" and 590 "/b/.../y" identify the same collection, C, then applying DELETE to 591 "/a" must not delete an internal member from C or from any other 592 collection that is a member of C, because that would modify the 593 membership of "/b". 595 If a collection supports the UNBIND method (see Section 5), a DELETE 596 of an internal member of a collection MAY be implemented as an UNBIND 597 request. In this case, applying DELETE to a Request-URI has the 598 effect of removing the binding identified by the final segment of the 599 Request-URI from the collection identified by the Request-URI minus 600 its final segment. Although [RFC4918] allows a DELETE to be a non- 601 atomic operation, when the DELETE operation is implemented as an 602 UNBIND, the operation is atomic. In particular, a DELETE on a 603 hierarchy of resources is simply the removal of a binding to the 604 collection identified by the Request-URI. 606 2.5. MOVE and Bindings 608 When MOVE is applied to a resource, the other bindings to that 609 resource MUST be unaffected, and if the resource being moved is a 610 collection, the bindings to any members of that collection MUST be 611 unaffected. Also, if MOVE is used with Overwrite:T to delete an 612 existing resource, the constraints specified for DELETE apply. 614 If the destination collection of a MOVE request supports the REBIND 615 method (see Section 6), a MOVE of a resource into that collection MAY 616 be implemented as a REBIND request. Although [RFC4918] allows a MOVE 617 to be a non-atomic operation, when the MOVE operation is implemented 618 as a REBIND, the operation is atomic. In particular, applying a MOVE 619 to a Request-URI and a Destination URI has the effect of removing a 620 binding to a resource (at the Request-URI), and creating a new 621 binding to that resource (at the Destination URI). Even when the 622 Request-URI identifies a collection, the MOVE operation involves only 623 removing one binding to that collection and adding another. 625 2.5.1. Example: Simple MOVE 627 As an example, suppose that a MOVE is issued to URI-3 for resource R 628 below (which is also mapped to URI-1 and URI-2), with the Destination 629 header set to URI-X. After successful completion of the MOVE 630 operation, a new binding has been created which creates the URI 631 mapping between URI-X and resource R. The binding corresponding to 632 the final segment of URI-3 has been removed, which also causes the 633 URI mapping between URI-3 and R to be removed. If resource R were a 634 collection, old URI-3 based mappings to members of R would have been 635 removed, and new URI-X based mappings to members of R would have been 636 created. 638 >> Before Request: 640 URI-1 URI-2 URI-3 641 | | | 642 | | | <---- URI Mappings 643 | | | 644 +---------------------+ 645 | Resource R | 646 +---------------------+ 648 >> After Request: 650 URI-1 URI-2 URI-X 651 | | | 652 | | | <---- URI Mappings 653 | | | 654 +---------------------+ 655 | Resource R | 656 +---------------------+ 658 2.5.2. Example: MOVE Request causing a Bind Loop 660 Note that in the presence of collection bindings, a MOVE request can 661 cause the creating of a bind loop. 663 Consider a the top level collections C1 and C2 with URIs "/CollW/" 664 and "/CollX/". C1 also contains an additional binding named "CollY" 665 to C2: 667 +------------------+ 668 | Root Collection | 669 | bindings: | 670 | CollW CollX | 671 +------------------+ 672 | | 673 | | 674 +------------------+ | 675 | Collection C1 | | 676 | bindings: | | 677 | CollY | | 678 +------------------+ | 679 | | 680 | | 681 +------------------+ 682 | Collection C2 | 683 | | 684 | | 685 +------------------+ 687 In this case, the MOVE request below would cause a bind loop: 689 >> Request: 691 MOVE /CollW HTTP/1.1 692 Host: example.com 693 Destination: /CollX/CollZ 694 If the request succeeded, the resulting state would be: 696 +------------------+ 697 | Root Collection | 698 | bindings: | 699 | CollX | 700 +------------------+ 701 | 702 | 703 +------------------+ | 704 | Collection C1 | | 705 +----> | bindings: | | 706 | | CollY | | 707 | +------------------+ | 708 | | | 709 | | | 710 | +------------------+ 711 | | Collection C2 | 712 | | bindings: | 713 | | CollZ | 714 | +------------------+ 715 | | 716 | | 717 +-------------------+ 719 2.6. PROPFIND and Bindings 721 Consistent with [RFC4918], the value of a dead property MUST be 722 independent of the number of bindings to its host resource or of the 723 path submitted to PROPFIND. On the other hand, the behaviour for 724 each live property depends on its individual definition (for example, 725 see [RFC3744], Section 5, paragraph 2). 727 2.7. Determining Whether Two Bindings Are to the Same Resource 729 It is useful to have some way of determining whether two bindings are 730 to the same resource. Two resources might have identical contents 731 and properties, but not be the same resource (e.g. an update to one 732 resource does not affect the other resource). 734 The REQUIRED DAV:resource-id property defined in Section 3.1 is a 735 resource identifier, which MUST be unique across all resources for 736 all time. If the values of DAV:resource-id returned by PROPFIND 737 requests through two bindings are identical character by character, 738 the client can be assured that the two bindings are to the same 739 resource. 741 The DAV:resource-id property is created, and its value assigned, when 742 the resource is created. The value of DAV:resource-id MUST NOT be 743 changed. Even after the resource is no longer accessible through any 744 URI, that value MUST NOT be reassigned to another resource's DAV: 745 resource-id property. 747 Any method that creates a new resource MUST assign a new, unique 748 value to its DAV:resource-id property. For example, a PUT applied to 749 a null resource, COPY (when not overwriting an existing target) and 750 CHECKIN (see [RFC3253], Section 4.4) must assign a new, unique value 751 to the DAV:resource-id property of the new resource they create. 753 On the other hand, any method that affects an existing resource must 754 not change the value of its DAV:resource-id property. Specifically, 755 a PUT or a COPY that updates an existing resource must not change the 756 value of its DAV:resource-id property. A REBIND, since it does not 757 create a new resource, but only changes the location of an existing 758 resource, must not change the value of the DAV:resource-id property. 760 2.8. Discovering the Bindings to a Resource 762 An OPTIONAL DAV:parent-set property on a resource provides a list of 763 the bindings that associate a collection and a URI segment with that 764 resource. If the DAV:parent-set property exists on a given resource, 765 it MUST contain a complete list of all bindings to that resource that 766 the client is authorized to see. When deciding whether to support 767 the DAV:parent-set property, server implementers / administrators 768 should balance the benefits it provides against the cost of 769 maintaining the property and the security risks enumerated in 770 Sections 10.4 and 10.5. 772 3. Properties 774 The bind feature introduces the properties defined below. 776 A DAV:allprop PROPFIND request SHOULD NOT return any of the 777 properties defined by this document. This allows a binding server to 778 perform efficiently when a naive client, which does not understand 779 the cost of asking a server to compute all possible live properties, 780 issues a DAV:allprop PROPFIND request. 782 3.1. DAV:resource-id Property 784 The DAV:resource-id property is a REQUIRED property that enables 785 clients to determine whether two bindings are to the same resource. 786 The value of DAV:resource-id is a URI, and may use any registered URI 787 scheme that guarantees the uniqueness of the value across all 788 resources for all time (e.g. the urn:uuid: URN namespace defined in 790 [RFC4122] or the opaquelocktoken: URI scheme defined in [RFC4918]). 792 794 Note: by definition, the URI specified in the DAV:resource-id 795 property always is an alternate URI for that resource. 797 3.2. DAV:parent-set Property 799 The DAV:parent-set property is an OPTIONAL property that enables 800 clients to discover what collections contain a binding to this 801 resource (i.e. what collections have that resource as an internal 802 member). It contains an href/segment pair for each collection that 803 has a binding to the resource. The href identifies the collection, 804 and the segment identifies the binding name of that resource in that 805 collection. 807 A given collection MUST appear only once in the DAV:parent-set for 808 any given binding, even if there are multiple URI mappings to that 809 collection. 811 812 813 814 817 3.2.1. Example for DAV:parent-set Property 819 For example, if collection C1 is mapped to both /CollX and /CollY, 820 and C1 contains a binding named "x.gif" to a resource R1, then either 821 [/CollX, x.gif] or [/CollY, x.gif] can appear in the DAV:parent-set 822 of R1, but not both. But if C1 also had a binding named "y.gif" to 823 R1, then there would be two entries for C1 in the DAV:binding-set of 824 R1 (i.e. both [/CollX, x.gif] and [/CollX, y.gif] or, alternatively, 825 both [/CollY, x.gif] and [/CollY, y.gif]). 827 +-------------------------+ 828 | Root Collection | 829 | bindings: | 830 | CollX CollY | 831 +-------------------------+ 832 | / 833 | / 834 | / 835 +-----------------+ 836 | Collection C1 | 837 | bindings: | 838 | x.gif y.gif | 839 +-----------------+ 840 | | 841 | | 842 | | 843 +--------------+ 844 | Resource R1 | 845 +--------------+ 847 In this case, one possible value for DAV:parent-set property on 848 "/CollX/x.gif" would be: 850 851 852 /CollX 853 x.gif 854 855 856 /CollX 857 y.gif 858 859 861 4. BIND Method 863 The BIND method modifies the collection identified by the Request- 864 URI, by adding a new binding from the segment specified in the BIND 865 body to the resource identified in the BIND body. 867 If a server cannot guarantee the integrity of the binding, the BIND 868 request MUST fail. Note that it is especially difficult to maintain 869 the integrity of cross-server bindings. Unless the server where the 870 resource resides knows about all bindings on all servers to that 871 resource, it may unwittingly destroy the resource or make it 872 inaccessible without notifying another server that manages a binding 873 to the resource. For example, if server A permits creation of a 874 binding to a resource on server B, server A must notify server B 875 about its binding and must have an agreement with B that B will not 876 destroy the resource while A's binding exists. Otherwise server B 877 may receive a DELETE request that it thinks removes the last binding 878 to the resource and destroy the resource while A's binding still 879 exists. The precondition DAV:cross-server-binding is defined below 880 for cases where servers fail cross-server BIND requests because they 881 cannot guarantee the integrity of cross-server bindings. 883 By default, if there already is a binding for the specified segment 884 in the collection, the new binding replaces the existing binding. 885 This default binding replacement behavior can be overridden using the 886 Overwrite header defined in Section 10.6 of [RFC4918]. 888 If a BIND request fails, the server state preceding the request MUST 889 be restored. This method is unsafe and idempotent (see [RFC2616], 890 Section 9.1). 892 Marshalling: 894 The request MAY include an Overwrite header. 896 The request body MUST be a DAV:bind XML element. 898 900 If the request succeeds, the server MUST return 201 (Created) when 901 a new binding was created and 200 (OK) when an existing binding 902 was replaced. 904 If a response body for a successful request is included, it MUST 905 be a DAV:bind-response XML element. Note that this document does 906 not define any elements for the BIND response body, but the DAV: 907 bind-response element is defined to ensure interoperability 908 between future extensions that do define elements for the BIND 909 response body. 911 913 Preconditions: 915 (DAV:bind-into-collection): The Request-URI MUST identify a 916 collection. 918 (DAV:bind-source-exists): The DAV:href element MUST identify a 919 resource. 921 (DAV:binding-allowed): The resource identified by the DAV:href 922 supports multiple bindings to it. 924 (DAV:cross-server-binding): If the resource identified by the DAV: 925 href element in the request body is on another server from the 926 collection identified by the Request-URI, the server MUST support 927 cross-server bindings (servers that do not support cross-server 928 bindings can use this condition code to signal the client exactly 929 why the request failed). 931 (DAV:name-allowed): The name specified by the DAV:segment is 932 available for use as a new binding name. 934 (DAV:can-overwrite): If the collection already contains a binding 935 with the specified path segment, and if an Overwrite header is 936 included, the value of the Overwrite header MUST be "T". 938 (DAV:cycle-allowed): If the DAV:href element identifies a 939 collection, and if the Request-URI identifies a collection that is 940 a member of that collection, the server MUST support cycles in the 941 URI namespace (servers that do not support cycles can use this 942 condition code to signal the client exactly why the request 943 failed). 945 (DAV:locked-update-allowed): If the collection identified by the 946 Request-URI is write-locked, then the appropriate token MUST be 947 specified in an If request header. 949 (DAV:locked-overwrite-allowed): If the collection already contains 950 a binding with the specified path segment, and if that binding is 951 protected by a write-lock, then the appropriate token MUST be 952 specified in an If request header. 954 Postconditions: 956 (DAV:new-binding): The collection MUST have a binding that maps 957 the segment specified in the DAV:segment element in the request 958 body, to the resource identified by the DAV:href element in the 959 request body. 961 4.1. Example: BIND 963 >> Request: 965 BIND /CollY HTTP/1.1 966 Host: www.example.com 967 Content-Type: application/xml; charset="utf-8" 968 Content-Length: xxx 970 971 972 bar.html 973 http://www.example.com/CollX/foo.html 974 976 >> Response: 978 HTTP/1.1 201 Created 980 The server added a new binding to the collection, 981 "http://www.example.com/CollY", associating "bar.html" with the 982 resource identified by the URI 983 "http://www.example.com/CollX/foo.html". Clients can now use the URI 984 "http://www.example.com/CollY/bar.html" to submit requests to that 985 resource. 987 5. UNBIND Method 989 The UNBIND method modifies the collection identified by the Request- 990 URI, by removing the binding identified by the segment specified in 991 the UNBIND body. 993 Once a resource is unreachable by any URI mapping, the server MAY 994 reclaim system resources associated with that resource. If UNBIND 995 removes a binding to a resource, but there remain URI mappings to 996 that resource, the server MUST NOT reclaim system resources 997 associated with the resource. 999 If an UNBIND request fails, the server state preceding the request 1000 MUST be restored. This method is unsafe and idempotent (see 1001 [RFC2616], Section 9.1). 1003 Marshalling: 1005 The request body MUST be a DAV:unbind XML element. 1007 1008 If the request succeeds, the server MUST return 200 (OK) when the 1009 binding was successfully deleted. 1011 If a response body for a successful request is included, it MUST 1012 be a DAV:unbind-response XML element. Note that this document 1013 does not define any elements for the UNBIND response body, but the 1014 DAV:unbind-response element is defined to ensure interoperability 1015 between future extensions that do define elements for the UNBIND 1016 response body. 1018 1020 Preconditions: 1022 (DAV:unbind-from-collection): The Request-URI MUST identify a 1023 collection. 1025 (DAV:unbind-source-exists): The DAV:segment element MUST identify 1026 a binding in the collection identified by the Request-URI. 1028 (DAV:locked-update-allowed): If the collection identified by the 1029 Request-URI is write-locked, then the appropriate token MUST be 1030 specified in the request. 1032 (DAV:protected-url-deletion-allowed): If the binding identified by 1033 the segment is protected by a write-lock, then the appropriate 1034 token MUST be specified in the request. 1036 Postconditions: 1038 (DAV:binding-deleted): The collection MUST NOT have a binding for 1039 the segment specified in the DAV:segment element in the request 1040 body. 1042 (DAV:lock-deleted): If the internal member URI of the binding 1043 specified by the Request-URI and the DAV:segment element in the 1044 request body was protected by a write-lock at the time of the 1045 request, that write-lock must have been deleted by the request. 1047 5.1. Example: UNBIND 1049 >> Request: 1051 UNBIND /CollX HTTP/1.1 1052 Host: www.example.com 1053 Content-Type: application/xml; charset="utf-8" 1054 Content-Length: xxx 1056 1057 1058 foo.html 1059 1061 >> Response: 1063 HTTP/1.1 200 OK 1065 The server removed the binding named "foo.html" from the collection, 1066 "http://www.example.com/CollX". A request to the resource named 1067 "http://www.example.com/CollX/foo.html" will return a 404 (Not Found) 1068 response. 1070 6. REBIND Method 1072 The REBIND method removes a binding to a resource from a collection, 1073 and adds a binding to that resource into the collection identified by 1074 the Request-URI. The request body specifies the binding to be added 1075 (segment) and the old binding to be removed (href). It is 1076 effectively an atomic form of a MOVE request, and MUST be treated the 1077 same way as MOVE for the purpose of determining access permissions. 1079 If a REBIND request fails, the server state preceding the request 1080 MUST be restored. This method is unsafe and idempotent (see 1081 [RFC2616], Section 9.1). 1083 Marshalling: 1085 The request MAY include an Overwrite header. 1087 The request body MUST be a DAV:rebind XML element. 1089 1091 If the request succeeds, the server MUST return 201 (Created) when 1092 a new binding was created and 200 (OK) when an existing binding 1093 was replaced. 1095 If a response body for a successful request is included, it MUST 1096 be a DAV:rebind-response XML element. Note that this document 1097 does not define any elements for the REBIND response body, but the 1098 DAV:rebind-response element is defined to ensure interoperability 1099 between future extensions that do define elements for the REBIND 1100 response body. 1102 1104 Preconditions: 1106 (DAV:rebind-into-collection): The Request-URI MUST identify a 1107 collection. 1109 (DAV:rebind-source-exists): The DAV:href element MUST identify a 1110 resource. 1112 (DAV:cross-server-binding): If the resource identified by the DAV: 1113 href element in the request body is on another server from the 1114 collection identified by the Request-URI, the server MUST support 1115 cross-server bindings (servers that do not support cross-server 1116 bindings can use this condition code to signal the client exactly 1117 why the request failed). 1119 (DAV:name-allowed): The name specified by the DAV:segment is 1120 available for use as a new binding name. 1122 (DAV:can-overwrite): If the collection already contains a binding 1123 with the specified path segment, and if an Overwrite header is 1124 included, the value of the Overwrite header MUST be "T". 1126 (DAV:cycle-allowed): If the DAV:href element identifies a 1127 collection, and if the Request-URI identifies a collection that is 1128 a member of that collection, the server MUST support cycles in the 1129 URI namespace (servers that do not support cycles can use this 1130 condition code to signal the client exactly why the request 1131 failed). 1133 (DAV:locked-update-allowed): If the collection identified by the 1134 Request-URI is write-locked, then the appropriate token MUST be 1135 specified in the request. 1137 (DAV:protected-url-modification-allowed): If the collection 1138 identified by the Request-URI already contains a binding with the 1139 specified path segment, and if that binding is protected by a 1140 write-lock, then the appropriate token MUST be specified in the 1141 request. 1143 (DAV:locked-source-collection-update-allowed): If the collection 1144 identified by the parent collection prefix of the DAV:href URI is 1145 write-locked, then the appropriate token MUST be specified in the 1146 request. 1148 (DAV:protected-source-url-deletion-allowed): If the DAV:href URI 1149 is protected by a write lock, then the appropriate token MUST be 1150 specified in the request. 1152 Postconditions: 1154 (DAV:new-binding): The collection MUST have a binding that maps 1155 the segment specified in the DAV:segment element in the request 1156 body, to the resource that was identified by the DAV:href element 1157 in the request body. 1159 (DAV:binding-deleted): The URL specified in the DAV:href element 1160 in the request body MUST NOT be mapped to a resource. 1162 (DAV:lock-deleted): If the URL specified in the DAV:href element 1163 in the request body was protected by a write-lock at the time of 1164 the request, that write-lock must have been deleted by the 1165 request. 1167 6.1. Example: REBIND 1169 >> Request: 1171 REBIND /CollX HTTP/1.1 1172 Host: www.example.com 1173 Content-Type: application/xml; charset="utf-8" 1174 Content-Length: xxx 1176 1177 1178 foo.html 1179 http://www.example.com/CollY/bar.html 1180 1182 >> Response: 1184 HTTP/1.1 200 OK 1186 The server added a new binding to the collection, 1187 "http://www.example.com/CollX", associating "foo.html" with the 1188 resource identified by the URI 1189 "http://www.example.com/CollY/bar.html", and removes the binding 1190 named "bar.html" from the collection identified by the URI 1191 "http://www.example.com/CollY". Clients can now use the URI 1192 "http://www.example.com/CollX/foo.html" to submit requests to that 1193 resource, and requests on the URI 1194 "http://www.example.com/CollY/bar.html" will fail with a 404 (Not 1195 Found) response. 1197 6.2. Example: REBIND in Presence of Locks and Bind Loops 1199 To illustrate the effects of locks and bind loops on a REBIND 1200 operation, consider the following collection: 1202 +------------------+ 1203 | Root Collection | 1204 | bindings: | 1205 | CollW | 1206 +------------------+ 1207 | 1208 | 1209 | 1210 +-------------------------------+ 1211 | Collection C1 |<--------+ 1212 | LOCKED infinity | | 1213 | (lock token L1) | | 1214 | bindings: | | 1215 | CollX CollY | | 1216 +-------------------------------+ | 1217 | | | 1218 | | (creates loop) | 1219 | | | 1220 +-----------------+ +------------------+ | 1221 | Collection C2 | | Collection C3 | | 1222 | (inherit lock) | | (inherit lock) | | 1223 | (lock token L1) | | (lock token L1) | | 1224 | bindings: | | bindings: | | 1225 | {none} | | y.gif CollZ | | 1226 +-----------------+ +------------------+ | 1227 | | | 1228 | +-----+ 1229 | 1230 +---------------------------+ 1231 | Resource R2 | 1232 | (lock inherited from C1) | 1233 | (lock token L1) | 1234 +---------------------------+ 1236 (where L1 is "urn:uuid:f92d4fae-7012-11ab-a765-00c0ca1f6bf9"). 1238 Note that the binding between CollZ and C1 creates a loop in the 1239 containment hierarchy. Servers are not required to support such 1240 loops, though the server in this example does. 1242 The REBIND request below will remove the segment "CollZ" from C3 and 1243 add a new binding from "CollA" to the collection C2. 1245 REBIND /CollW/CollX HTTP/1.1 1246 Host: www.example.com 1247 If: () 1248 Content-Type: application/xml; charset="utf-8" 1249 Content-Length: xxx 1251 1252 1253 CollA 1254 /CollW/CollY/CollZ 1255 1256 The outcome of the REBIND operation is: 1258 +------------------+ 1259 | Root Collection | 1260 | bindings: | 1261 | CollW | 1262 +------------------+ 1263 | 1264 | 1265 | 1266 +-------------------------------+ 1267 | Collection C1 | 1268 | LOCKED infinity | 1269 | (lock token L1) | 1270 | bindings: | 1271 | CollX CollY | 1272 +-------------------------------+ 1273 | ^ | 1274 | | | 1275 +-----------------+ | +------------------+ 1276 | Collection C2 | | | Collection C3 | 1277 |(inherited lock) | | | (inherited lock) | 1278 |(lock token L1) | | | (lock token L1) | 1279 | bindings: | | | bindings: | 1280 | CollA | | | y.gif | 1281 +-----------------+ | +------------------+ 1282 | | | 1283 +---------------+ | 1284 (creates loop) | 1285 +---------------------------+ 1286 | Resource R2 | 1287 | (inherited lock from C1) | 1288 | (lock token L1) | 1289 +---------------------------+ 1291 7. Additional Status Codes 1293 7.1. 208 Already Reported 1295 The 208 (Already Reported) status code can be used inside a DAV: 1296 propstat response element to avoid enumerating the internal members 1297 of multiple bindings to the same collection repeatedly. For each 1298 binding to a collection inside the request's scope, only one will be 1299 reported with a 200 status, while subsequent DAV:response elements 1300 for all other bindings will use the 208 status, and no DAV:response 1301 elements for their descendants are included. 1303 Note that the 208 status will only occur for "Depth: infinity" 1304 requests, and that it is of particular importance when the multiple 1305 collection bindings cause a bind loop as discussed in Section 2.2. 1307 A client can request the DAV:resource-id property in a PROPFIND 1308 request to guarantee that they can accurately reconstruct the binding 1309 structure of a collection with multiple bindings to a single 1310 resource. 1312 For backward compatibility with clients not aware of the 208 status 1313 code appearing in multistatus response bodies, it SHOULD NOT be used 1314 unless the client has signalled support for this specification using 1315 the "DAV" request header (see Section 8.2). Instead, a 506 status 1316 should be returned when a binding loop is discovered. This allows 1317 the server to return the 506 as the top level return status, if it 1318 discovers it before it started the response, or in the middle of a 1319 multistatus, if it discovers it in the middle of streaming out a 1320 multistatus response. 1322 7.1.1. Example: PROPFIND by Bind-Aware Client 1324 For example, consider a PROPFIND request on /Coll (bound to 1325 collection C), where the members of /Coll are /Coll/Foo (bound to 1326 resource R) and /Coll/Bar (bound to collection C). 1328 >> Request: 1330 PROPFIND /Coll/ HTTP/1.1 1331 Host: www.example.com 1332 Depth: infinity 1333 DAV: bind 1334 Content-Type: application/xml; charset="utf-8" 1335 Content-Length: xxx 1337 1338 1339 1340 1341 1342 1343 1345 >> Response: 1347 HTTP/1.1 207 Multi-Status 1348 Content-Type: application/xml; charset="utf-8" 1349 Content-Length: xxx 1351 1352 1353 1354 http://www.example.com/Coll/ 1355 1356 1357 Loop Demo 1358 1359 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf8 1361 1362 1363 HTTP/1.1 200 OK 1364 1365 1366 1367 http://www.example.com/Coll/Foo 1368 1369 1370 Bird Inventory 1371 1372 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf9 1374 1375 1376 HTTP/1.1 200 OK 1377 1378 1379 1380 http://www.example.com/Coll/Bar 1381 1382 1383 Loop Demo 1384 1385 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf8 1387 1388 1389 HTTP/1.1 208 Already Reported 1390 1391 1392 1394 7.1.2. Example: PROPFIND by Non-Bind-Aware Client 1396 In this example, the client isn't aware of the 208 status code 1397 introduced by this specification. As the "Depth: infinity" PROPFIND 1398 request would cause a loop condition, the whole request is rejected 1399 with a 506 status. 1401 >> Request: 1403 PROPFIND /Coll/ HTTP/1.1 1404 Host: www.example.com 1405 Depth: infinity 1406 Content-Type: application/xml; charset="utf-8" 1407 Content-Length: xxx 1409 1410 1411 1412 1414 >> Response: 1416 HTTP/1.1 506 Loop Detected 1418 7.2. 506 Loop Detected 1420 The 506 (Loop Detected) status code indicates that the server 1421 terminated an operation because it encountered an infinite loop while 1422 processing a request with "Depth: infinity". This status indicates 1423 that the entire operation failed. 1425 8. Capability Discovery 1427 8.1. OPTIONS Method 1429 If the server supports bindings, it MUST return the compliance class 1430 name "bind" as a field in the "DAV" response header (see [RFC4918], 1431 Section 10.1) from an OPTIONS request on any resource implemented by 1432 that server. A value of "bind" in the "DAV" header MUST indicate 1433 that the server supports all MUST level requirements and REQUIRED 1434 features specified in this document. 1436 8.2. 'DAV' Request Header 1438 Clients SHOULD signal support for all MUST level requirements and 1439 REQUIRED features by submitting a "DAV" request header containing the 1440 compliance class name "bind". In particular, the client MUST 1441 understand the 208 status code defined in Section 7.1. 1443 9. Relationship to WebDAV Access Control Protocol 1445 BIND and REBIND behave the same as MOVE with respect to the DAV:acl 1446 property (see [RFC3744], Section 7.3). 1448 10. Security Considerations 1450 This section is provided to make WebDAV implementors aware of the 1451 security implications of this protocol. 1453 All of the security considerations of HTTP/1.1 and the WebDAV 1454 Distributed Authoring Protocol specification also apply to this 1455 protocol specification. In addition, bindings introduce several new 1456 security concerns and increase the risk of some existing threats. 1457 These issues are detailed below. 1459 10.1. Privacy Concerns 1461 In a context where cross-server bindings are supported, creating 1462 bindings on a trusted server may make it possible for a hostile agent 1463 to induce users to send private information to a target on a 1464 different server. 1466 10.2. Bind Loops 1468 Although bind loops were already possible in HTTP 1.1, the 1469 introduction of the BIND method creates a new avenue for clients to 1470 create loops accidentally or maliciously. If the binding and its 1471 target are on the same server, the server may be able to detect BIND 1472 requests that would create loops. Servers are required to detect 1473 loops that are caused by bindings to collections during the 1474 processing of any requests with "Depth: infinity". 1476 10.3. Bindings, and Denial of Service 1478 Denial of service attacks were already possible by posting URIs that 1479 were intended for limited use at heavily used Web sites. The 1480 introduction of BIND creates a new avenue for similar denial of 1481 service attacks. If cross-server bindings are supported, clients can 1482 now create bindings at heavily used sites to target locations that 1483 were not designed for heavy usage. 1485 10.4. Private Locations May Be Revealed 1487 If the DAV:parent-set property is maintained on a resource, the 1488 owners of the bindings risk revealing private locations. The 1489 directory structures where bindings are located are available to 1490 anyone who has access to the DAV:parent-set property on the resource. 1491 Moving a binding may reveal its new location to anyone with access to 1492 DAV:parent-set on its resource. 1494 10.5. DAV:parent-set and Denial of Service 1496 If the server maintains the DAV:parent-set property in response to 1497 bindings created in other administrative domains, it is exposed to 1498 hostile attempts to make it devote resources to adding bindings to 1499 the list. 1501 11. Internationalization Considerations 1503 All internationalization considerations mentioned in [RFC4918] also 1504 apply to this document. 1506 12. IANA Considerations 1508 Section 7 defines the HTTP status codes 208 (Already Reported) and 1509 506 (Loop Detected), to be added to the registry at 1510 . 1512 13. Acknowledgements 1514 This document is the collaborative product of the authors and Tyson 1515 Chihaya, Jim Davis, Chuck Fay and Judith Slein. It has benefited 1516 from thoughtful discussion by Jim Amsden, Peter Carlson, Steve 1517 Carter, Ken Coar, Ellis Cohen, Dan Connolly, Bruce Cragun, Spencer 1518 Dawkins, Mark Day, Werner Donne, Rajiv Dulepet, David Durand, Lisa 1519 Dusseault, Stefan Eissing, Roy Fielding, Yaron Goland, Joe 1520 Hildebrand, Fred Hitt, Alex Hopmann, James Hunt, Marcus Jager, Chris 1521 Kaler, Manoj Kasichainula, Rohit Khare, Brian Korver, Daniel 1522 LaLiberte, Steve Martin, Larry Masinter, Jeff McAffer, Surendra 1523 Koduru Reddy, Max Rible, Sam Ruby, Bradley Sergeant, Nick Shelness, 1524 John Stracke, John Tigue, John Turner, Kevin Wiggen, and other 1525 members of the WebDAV working group. 1527 14. References 1528 14.1. Normative References 1530 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1531 Requirement Levels", BCP 14, RFC 2119, March 1997. 1533 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1534 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 1535 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1537 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1538 Resource Identifier (URI): Generic Syntax", STD 66, 1539 RFC 3986, January 2005. 1541 [RFC4918] Dusseault, L., Ed., "HTTP Extensions for Web Distributed 1542 Authoring and Versioning (WebDAV)", RFC 4918, June 2007. 1544 [XML] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and 1545 F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth 1546 Edition)", W3C REC-xml-20060816, August 2006, 1547 . 1549 14.2. Informative References 1551 [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. 1552 Whitehead, "Versioning Extensions to WebDAV (Web 1553 Distributed Authoring and Versioning)", RFC 3253, 1554 March 2002. 1556 [RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web 1557 Distributed Authoring and Versioning (WebDAV) Access 1558 Control Protocol", RFC 3744, May 2004. 1560 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 1561 Unique IDentifier (UUID) URN Namespace", RFC 4122, 1562 July 2005. 1564 Appendix A. Clarification to RFC2518bis' Usage of the term 'lock root' 1566 [RFC4918], Section 9.10.1 claims: 1568 A LOCK request to an existing resource will create a lock on the 1569 resource identified by the Request-URI, provided the resource is 1570 not already locked with a conflicting lock. The resource 1571 identified in the Request-URI becomes the root of the lock. 1573 This is incorrect in that it implies that the "lock root" is a 1574 resource, not a URL 1575 (). However, 1576 should a directly locked resource have multiple bindings, only the 1577 one used in the Request-URI of the LOCK request will be the protected 1578 from changes of clients not supplying the lock token. 1580 A correct description would be: 1582 A LOCK request to an existing resource will create a lock on the 1583 resource identified by the Request-URI, provided the resource is 1584 not already locked with a conflicting lock. The Request-URI 1585 becomes the root of the lock. 1587 Note that this change makes the description consistent with the 1588 definition of the DAV:lockroot XML element in Section 14.12 of 1589 [RFC4918]. 1591 The authors of this specification recommend that future revisions of 1592 [RFC4918] will update the description as suggested above. 1594 Appendix B. Change Log (to be removed by RFC Editor before publication) 1596 B.1. Since draft-ietf-webdav-bind-02 1598 Add and resolve issues "2.3_COPY_SHARED_BINDINGS" and 1599 "2.3_MULTIPLE_COPY". Add issue "5.1_LOOP_STATUS" and proposed 1600 resolution, but keep it open. Add issues "ED_references" and 1601 "4_507_status". Started work on index. Rename document to "Binding 1602 Extensions to Web Distributed Authoring and Versioning (WebDAV)". 1603 Rename "References" to "Normative References". Close issue 1604 "ED_references". Close issue "4_507_status". 1606 B.2. Since draft-ietf-webdav-bind-03 1608 Add and close issues "9.2_redirect_loops", "ED_authors" and 1609 "ED_updates". Add section about capability discovery (DAV header). 1610 Close issues "5.1_LOOP_STATUS". Add and resolve new issue 1611 "5.1_506_STATUS_STREAMING". Update XML spec reference. Add issue 1612 "locking" and resolve as invalid. 1614 B.3. Since draft-ietf-webdav-bind-04 1616 Add and close issues "6_precondition_binding_allowed" and 1617 "6_lock_behaviour". Add mailing list and issues list pointers to 1618 front. 1620 B.4. Since draft-ietf-webdav-bind-05 1622 Editorial fixes. Add and resolve issues "1.3_error_negotiation", 1623 "2.5_language" and "7.1.1_add_resource_id". Add historical issue 1624 "4_LOCK_BEHAVIOR" and it's resolution for better tracking. 1626 B.5. Since draft-ietf-webdav-bind-06 1628 Rewrite Editorial Note. Open and resolve issues "2.6_identical", 1629 "specify_safeness_and_idempotence" and "ED_rfc2026_ref". 1631 B.6. Since draft-ietf-webdav-bind-07 1633 Add more index items (no change tracking). Add and resolve issues 1634 "2.3_copy_to_same", "bind_properties", "bind_vs_ACL", 1635 "6_rebind_intro" and "rfc2396bis" (actually an action item). Fix XML 1636 DTD fragment in section 3.3. Make spelling of "Request-URI" 1637 consistent. 1639 B.7. Since draft-ietf-webdav-bind-08 1641 Resolved editorial issues raised by Jim Whitehead in . 1643 Add and resolve issues "atomicity", "2_allow_destroy", 1644 "2.1_separate_loop_discussion", "2.1.1_bind_loops_vs_locks", 1645 "2.3_copy_depth_infinity", "2.3_copy_example", "2.3_copy_vs_loops", 1646 "2.6_resource-id_vs_versions", "3.2_example" and 1647 "6_rebind_premissions". Add issue "2.6_when_do_ids_change". Re-open 1648 and resolve "6_rebind_intro". 1650 B.8. Since draft-ietf-webdav-bind-09 1652 Add and resolve issue "6.1_rebind_vs_locks", adding proposed example 1653 text. Add action item "3.1_uuids". Close issue 1654 "2.6_when_do_ids_change". Add and resolve issues 1655 "2.6_bindings_vs_properties" and "uri_draft_ref". 1657 B.9. Since draft-ietf-webdav-bind-10 1659 Resolve action item "3.1_uuids". Add and resolve issue 1660 "2.7_unlock_vs_bindings". Revisit issue 1661 "2.6_bindings_vs_properties", and remove the part of the sentence 1662 that speaks about live properties. Update "rfc2396bis" references to 1663 "RFC3986". Add issue "9_ns_op_and_acl" and add potential resolution. 1664 Align artwork where applicable (new xml2rfc1.29rc2 feature). 1666 B.10. Since draft-ietf-webdav-bind-11 1668 Updated [draft-mealling-uuid-urn] to [RFC4122]. Add statement about 1669 live properties in Section 2.6. 1671 B.11. Since draft-ietf-webdav-bind-12 1673 Updated Author's address. Uppercase "Section" when referring to 1674 other documents. 1676 Updating from RFC2518 to RFC2518bis: 1678 o Remove own explanation of DTD syntax. 1680 o Remove own definition of precondition/postcondition. 1682 o Remove reference to broken RFC2518 language about DELETE and 1683 UNLOCK. 1685 o Remove own definition of DAV: request header. 1687 o Updated "Rationale for Distinguishing Bindings from URI Mappings" 1688 to reflect the changes in [draft-ietf-webdav-rfc2518bis], making 1689 proposals for more changes so that the issue can be closed (see 1690 also 1691 and ). 1694 B.12. Since draft-ietf-webdav-bind-13 1696 Update [draft-ietf-webdav-rfc2518-bis] to draft 14. Update one 1697 incorrect section reference. Remove Section "Rationale for 1698 Distinguishing Bindings from URI Mappings" as 1699 [draft-ietf-webdav-rfc2518-bis] now uses the proper definition of 1700 collection state. Examples use application/xml instead of text/xml 1701 MIME type. 1703 Fix IANA section (there are no IANA considerations). 1705 B.13. Since draft-ietf-webdav-bind-14 1707 Update [draft-ietf-webdav-rfc2518-bis] to draft 15. Update [XML] to 1708 4th edition. 1710 Markup ASCII art for box recognition (doesn't affect ASCII version). 1712 Identify Julian Reschke as Editor. 1714 B.14. Since draft-ietf-webdav-bind-15 1716 Fix typo in RFC2119 keywords section (sorry!). 1718 Update [draft-ietf-webdav-rfc2518-bis] to draft 17. 1720 Add and resolve issue "rfc2518bis-lock-root". 1722 B.15. Since draft-ietf-webdav-bind-16 1724 Add and resolve issue "iana-vs-http-status". 1726 B.16. Since draft-ietf-webdav-bind-17 1728 Update rfc2518bis reference to draft 18 (note that the bug reported 1729 in 1730 is still present). 1732 B.17. Since draft-ietf-webdav-bind-18 1734 Update: draft-ietf-webdav-rfc2518bis replaced by RFC4918. 1736 B.18. Since draft-ietf-webdav-bind-19 1738 Add and resolve issues "2.1.1-bind-loops", "2.1.1-cycles", "2.5-move- 1739 creating-cycles", "3.1-clarify-resource-id" and "4-precondition- 1740 language". 1742 B.19. Since draft-ietf-webdav-bind-20 1744 Use "urn:uuid:" instead of "opaquelocktoken:" scheme in examples. 1745 Replace RFC518bis issue link by pointer to RFC Errata Page. 1747 Add issues "relation-to-deltav" and "status-codes". 1749 Appendix C. Open issues (to be removed by RFC Editor prior to 1750 publication) 1752 C.1. edit 1754 Type: edit 1756 julian.reschke@greenbytes.de (2004-05-30): Umbrella issue for 1757 editorial fixes/enhancements. 1759 C.2. status-codes 1761 Type: change 1763 1766 julian.reschke@greenbytes.de (2008-09-26): The spec currently micro- 1767 manages HTTP status codes: for instance, for a successful BIND it 1768 requires status codes of 200 or 201, while - from an HTTP point of 1769 view - a 204 should be acceptable as well. Proposal: rephrase the 1770 text so that other success codes are acceptable as well, or remove 1771 the normative language completely, point to RFC2616, and rely on 1772 examples. 1774 C.3. relation-to-deltav 1776 Type: change 1778 1781 werner.donne@re.be (2008-08-11): ...When supporting version 1782 controlled collections, bindings may be introduced in a server 1783 without actually issuing the BIND method. When a MOVE is performed 1784 of a resource from one collection to another, both collections should 1785 be checked out. An additional binding would be the result if one 1786 collection would be subsequently checked in, while the check-out of 1787 the other is undone. The resulting situation is meaningless if the 1788 binding model is not supported... 1790 Index 1792 2 1793 208 Already Reported (status code) 31, 36 1795 5 1796 506 Loop Detected (status code) 34, 36 1798 B 1799 BIND method 21 1800 Marshalling 22 1801 Postconditions 23 1802 Preconditions 22 1803 Binding 7 1805 C 1806 Collection 7 1807 Condition Names 1808 DAV:bind-into-collection (pre) 22 1809 DAV:bind-source-exists (pre) 22 1810 DAV:binding-allowed (pre) 23 1811 DAV:binding-deleted (post) 25, 28 1812 DAV:can-overwrite (pre) 23, 27 1813 DAV:cross-server-binding (pre) 23, 27 1814 DAV:cycle-allowed (pre) 23, 27 1815 DAV:lock-deleted (post) 25, 28 1816 DAV:locked-overwrite-allowed (pre) 23 1817 DAV:locked-source-collection-update-allowed (pre) 28 1818 DAV:locked-update-allowed (pre) 23, 25, 27 1819 DAV:name-allowed (pre) 23, 27 1820 DAV:new-binding (post) 23, 28 1821 DAV:protected-source-url-deletion-allowed (pre) 28 1822 DAV:protected-url-deletion-allowed (pre) 25 1823 DAV:protected-url-modification-allowed (pre) 27 1824 DAV:rebind-from-collection (pre) 27 1825 DAV:rebind-source-exists (pre) 27 1826 DAV:unbind-from-collection (pre) 25 1827 DAV:unbind-source-exists (pre) 25 1829 D 1830 DAV header 1831 compliance class 'bind' 34 1832 DAV:bind-into-collection precondition 22 1833 DAV:bind-source-exists precondition 22 1834 DAV:binding-allowed precondition 23 1835 DAV:binding-deleted postcondition 25, 28 1836 DAV:can-overwrite precondition 23, 27 1837 DAV:cross-server-binding precondition 23, 27 1838 DAV:cycle-allowed precondition 23, 27 1839 DAV:lock-deleted postcondition 25, 28 1840 DAV:locked-overwrite-allowed precondition 23 1841 DAV:locked-source-collection-update-allowed precondition 28 1842 DAV:locked-update-allowed precondition 23, 25, 27 1843 DAV:name-allowed precondition 23, 27 1844 DAV:new-binding postcondition 23, 28 1845 DAV:parent-set property 20 1846 DAV:protected-source-url-deletion-allowed precondition 28 1847 DAV:protected-url-deletion-allowed precondition 25 1848 DAV:protected-url-modification-allowed precondition 27 1849 DAV:rebind-from-collection precondition 27 1850 DAV:rebind-source-exists precondition 27 1851 DAV:resource-id property 19 1852 DAV:unbind-from-collection precondition 25 1853 DAV:unbind-source-exists precondition 25 1855 I 1856 Internal Member URI 7 1858 M 1859 Methods 1860 BIND 21 1861 REBIND 26 1862 UNBIND 24 1864 P 1865 Path Segment 6 1866 Properties 1867 DAV:parent-set 20 1868 DAV:resource-id 19 1870 R 1871 REBIND method 26 1872 Marshalling 26 1873 Postconditions 28 1874 Preconditions 27 1876 S 1877 Status Codes 1878 208 Already Reported 31, 36 1879 506 Loop Detected 34, 36 1881 U 1882 UNBIND method 24 1883 Marshalling 24 1884 Postconditions 25 1885 Preconditions 25 1886 URI Mapping 6 1888 Authors' Addresses 1890 Geoffrey Clemm 1891 IBM 1892 20 Maguire Road 1893 Lexington, MA 02421 1895 Email: geoffrey.clemm@us.ibm.com 1896 Jason Crawford 1897 IBM Research 1898 P.O. Box 704 1899 Yorktown Heights, NY 10598 1901 Email: ccjason@us.ibm.com 1903 Julian F. Reschke (editor) 1904 greenbytes GmbH 1905 Hafenweg 16 1906 Muenster, NW 48155 1907 Germany 1909 Email: julian.reschke@greenbytes.de 1911 Jim Whitehead 1912 UC Santa Cruz, Dept. of Computer Science 1913 1156 High Street 1914 Santa Cruz, CA 95064 1916 Email: ejw@cse.ucsc.edu 1918 Full Copyright Statement 1920 Copyright (C) The IETF Trust (2008). 1922 This document is subject to the rights, licenses and restrictions 1923 contained in BCP 78, and except as set forth therein, the authors 1924 retain all their rights. 1926 This document and the information contained herein are provided on an 1927 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 1928 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 1929 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 1930 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 1931 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 1932 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 1934 Intellectual Property 1936 The IETF takes no position regarding the validity or scope of any 1937 Intellectual Property Rights or other rights that might be claimed to 1938 pertain to the implementation or use of the technology described in 1939 this document or the extent to which any license under such rights 1940 might or might not be available; nor does it represent that it has 1941 made any independent effort to identify any such rights. 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