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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 2616 (Obsoleted by RFC 7230, RFC 7231, RFC 7232, RFC 7233, RFC 7234, RFC 7235) -- Possible downref: Non-RFC (?) normative reference: ref. 'XML' Summary: 5 errors (**), 1 flaw (~~), 6 warnings (==), 8 comments (--). 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: J. Crawford 5 draft-ietf-webdav-rfc2518bis (if IBM Research 6 approved) J. Reschke 7 Expires: August 26, 2006 greenbytes 8 J. Whitehead 9 U.C. Santa Cruz 10 February 22, 2006 12 Binding Extensions to Web Distributed Authoring and Versioning (WebDAV) 13 draft-ietf-webdav-bind-14 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 August 26, 2006. 40 Copyright Notice 42 Copyright (C) The Internet Society (2006). 44 Abstract 46 This specification defines bindings, and the BIND method for creating 47 multiple bindings to the same resource. Creating a new binding to a 48 resource causes at least one new URI to be mapped to that resource. 50 Servers are required to insure the integrity of any bindings that 51 they allow to be created. 53 Editorial Note (To be removed by RFC Editor before publication) 55 Please send comments to the Distributed Authoring and Versioning 56 (WebDAV) working group at , which may be 57 joined by sending a message with subject "subscribe" to 58 . Discussions of the WEBDAV 59 working group are archived at 60 . 62 lists 63 all registered issues since draft 02. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 69 1.2. Method Preconditions and Postconditions . . . . . . . . . 6 70 2. Overview of Bindings . . . . . . . . . . . . . . . . . . . . . 6 71 2.1. Bindings to Collections . . . . . . . . . . . . . . . . . 7 72 2.1.1. Bind loops . . . . . . . . . . . . . . . . . . . . . . 8 73 2.2. URI Mappings Created by a new Binding . . . . . . . . . . 8 74 2.3. COPY and Bindings . . . . . . . . . . . . . . . . . . . . 9 75 2.3.1. Example: COPY with 'Depth: infinity' in presence 76 of bind loops . . . . . . . . . . . . . . . . . . . . 11 77 2.3.2. Example: COPY with 'Depth: infinity' with multiple 78 bindings to a leaf resource . . . . . . . . . . . . . 13 79 2.4. DELETE and Bindings . . . . . . . . . . . . . . . . . . . 14 80 2.5. MOVE and Bindings . . . . . . . . . . . . . . . . . . . . 14 81 2.6. PROPFIND and Bindings . . . . . . . . . . . . . . . . . . 15 82 2.7. Determining Whether Two Bindings Are to the Same 83 Resource . . . . . . . . . . . . . . . . . . . . . . . . . 15 84 2.8. Discovering the Bindings to a Resource . . . . . . . . . . 16 85 3. Properties . . . . . . . . . . . . . . . . . . . . . . . . . . 16 86 3.1. DAV:resource-id Property . . . . . . . . . . . . . . . . . 17 87 3.2. DAV:parent-set Property . . . . . . . . . . . . . . . . . 17 88 3.2.1. Example for DAV:parent-set property . . . . . . . . . 17 89 4. BIND Method . . . . . . . . . . . . . . . . . . . . . . . . . 18 90 4.1. Example: BIND . . . . . . . . . . . . . . . . . . . . . . 21 91 5. UNBIND Method . . . . . . . . . . . . . . . . . . . . . . . . 21 92 5.1. Example: UNBIND . . . . . . . . . . . . . . . . . . . . . 23 93 6. REBIND Method . . . . . . . . . . . . . . . . . . . . . . . . 23 94 6.1. Example: REBIND . . . . . . . . . . . . . . . . . . . . . 25 95 6.2. Example: REBIND in presence of locks and bind loops . . . 26 96 7. Additional Status Codes . . . . . . . . . . . . . . . . . . . 28 97 7.1. 208 Already Reported . . . . . . . . . . . . . . . . . . . 28 98 7.1.1. Example: PROPFIND by bind-aware client . . . . . . . . 29 99 7.1.2. Example: PROPFIND by non-bind-aware client . . . . . . 31 100 7.2. 506 Loop Detected . . . . . . . . . . . . . . . . . . . . 31 101 8. Capability discovery . . . . . . . . . . . . . . . . . . . . . 31 102 8.1. OPTIONS method . . . . . . . . . . . . . . . . . . . . . . 31 103 8.2. 'DAV' request header . . . . . . . . . . . . . . . . . . . 31 104 9. Relationship to WebDAV Access Control Protocol . . . . . . . . 32 105 10. Security Considerations . . . . . . . . . . . . . . . . . . . 32 106 10.1. Privacy Concerns . . . . . . . . . . . . . . . . . . . . . 32 107 10.2. Bind Loops . . . . . . . . . . . . . . . . . . . . . . . . 32 108 10.3. Bindings, and Denial of Service . . . . . . . . . . . . . 32 109 10.4. Private Locations May Be Revealed . . . . . . . . . . . . 33 110 10.5. DAV:parent-set and Denial of Service . . . . . . . . . . . 33 111 11. Internationalization Considerations . . . . . . . . . . . . . 33 112 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 33 113 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 33 114 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 34 115 14.1. Normative References . . . . . . . . . . . . . . . . . . . 34 116 14.2. Informative References . . . . . . . . . . . . . . . . . . 34 117 Appendix A. Change Log (to be removed by RFC Editor before 118 publication) . . . . . . . . . . . . . . . . . . . . 34 119 A.1. Since draft-ietf-webdav-bind-02 . . . . . . . . . . . . . 34 120 A.2. Since draft-ietf-webdav-bind-03 . . . . . . . . . . . . . 35 121 A.3. Since draft-ietf-webdav-bind-04 . . . . . . . . . . . . . 35 122 A.4. Since draft-ietf-webdav-bind-05 . . . . . . . . . . . . . 35 123 A.5. Since draft-ietf-webdav-bind-06 . . . . . . . . . . . . . 35 124 A.6. Since draft-ietf-webdav-bind-07 . . . . . . . . . . . . . 35 125 A.7. Since draft-ietf-webdav-bind-08 . . . . . . . . . . . . . 35 126 A.8. Since draft-ietf-webdav-bind-09 . . . . . . . . . . . . . 36 127 A.9. Since draft-ietf-webdav-bind-10 . . . . . . . . . . . . . 36 128 A.10. Since draft-ietf-webdav-bind-11 . . . . . . . . . . . . . 36 129 A.11. Since draft-ietf-webdav-bind-12 . . . . . . . . . . . . . 36 130 A.12. Since draft-ietf-webdav-bind-13 . . . . . . . . . . . . . 36 131 Appendix B. Resolved issues (to be removed by RFC Editor 132 before publication) . . . . . . . . . . . . . . . . . 37 133 B.1. webdav-rev . . . . . . . . . . . . . . . . . . . . . . . . 37 134 Appendix C. Open issues (to be removed by RFC Editor prior to 135 publication) . . . . . . . . . . . . . . . . . . . . 37 136 C.1. edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 137 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 138 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40 139 Intellectual Property and Copyright Statements . . . . . . . . . . 41 141 1. Introduction 143 This specification extends the WebDAV Distributed Authoring Protocol 144 ([draft-ietf-webdav-rfc2518bis]) to enable clients to create new 145 access paths to existing resources. This capability is useful for 146 several reasons: 148 URIs of WebDAV-compliant resources are hierarchical and correspond to 149 a hierarchy of collections in resource space. The WebDAV Distributed 150 Authoring Protocol makes it possible to organize these resources into 151 hierarchies, placing them into groupings, known as collections, which 152 are more easily browsed and manipulated than a single flat 153 collection. However, hierarchies require categorization decisions 154 that locate resources at a single location in the hierarchy, a 155 drawback when a resource has multiple valid categories. For example, 156 in a hierarchy of vehicle descriptions containing collections for 157 cars and boats, a description of a combination car/boat vehicle could 158 belong in either collection. Ideally, the description should be 159 accessible from both. Allowing clients to create new URIs that 160 access the existing resource lets them put that resource into 161 multiple collections. 163 Hierarchies also make resource sharing more difficult, since 164 resources that have utility across many collections are still forced 165 into a single collection. For example, the mathematics department at 166 one university might create a collection of information on fractals 167 that contains bindings to some local resources, but also provides 168 access to some resources at other universities. For many reasons, it 169 may be undesirable to make physical copies of the shared resources on 170 the local server: to conserve disk space, to respect copyright 171 constraints, or to make any changes in the shared resources visible 172 automatically. Being able to create new access paths to existing 173 resources in other collections or even on other servers is useful for 174 this sort of case. 176 The BIND method defined here provides a mechanism for allowing 177 clients to create alternative access paths to existing WebDAV 178 resources. HTTP [RFC2616] and WebDAV [draft-ietf-webdav-rfc2518bis] 179 methods are able to work because there are mappings between URIs and 180 resources. A method is addressed to a URI, and the server follows 181 the mapping from that URI to a resource, applying the method to that 182 resource. Multiple URIs may be mapped to the same resource, but 183 until now there has been no way for clients to create additional URIs 184 mapped to existing resources. 186 BIND lets clients associate a new URI with an existing WebDAV 187 resource, and this URI can then be used to submit requests to the 188 resource. Since URIs of WebDAV resources are hierarchical, and 189 correspond to a hierarchy of collections in resource space, the BIND 190 method also has the effect of adding the resource to a collection. 191 As new URIs are associated with the resource, it appears in 192 additional collections. 194 A BIND request does not create a new resource, but simply makes 195 available a new URI for submitting requests to an existing resource. 196 The new URI is indistinguishable from any other URI when submitting a 197 request to a resource. Only one round trip is needed to submit a 198 request to the intended target. Servers are required to enforce the 199 integrity of the relationships between the new URIs and the resources 200 associated with them. Consequently, it may be very costly for 201 servers to support BIND requests that cross server boundaries. 203 This specification is organized as follows. Section 1.1 defines 204 terminology used in the rest of the specification, while Section 2 205 overviews bindings. Section 3 defines the new properties needed to 206 support multiple bindings to the same resource. Section 4 specifies 207 the BIND method, used to create multiple bindings to the same 208 resource. Section 5 specifies the UNBIND method, used to remove a 209 binding to a resource. Section 6 specifies the REBIND method, used 210 to move a binding to another collection. 212 1.1. Terminology 214 The terminology used here follows and extends that in the WebDAV 215 Distributed Authoring Protocol specification 216 [draft-ietf-webdav-rfc2518bis]. 218 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 219 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 220 document are to be interpreted as described in [RFC2119]. 222 This document uses XML DTD fragments ([XML]) as a notational 223 convention, using the rules defined in Section 17 of 224 [draft-ietf-webdav-rfc2518bis]. 226 URI Mapping 228 A relation between an absolute URI and a resource. For an 229 absolute URI U and the resource it identifies R, the URI mapping 230 can be thought of as (U => R). Since a resource can represent 231 items that are not network retrievable, as well as those that are, 232 it is possible for a resource to have zero, one, or many URI 233 mappings. Mapping a resource to an "http" scheme URI makes it 234 possible to submit HTTP protocol requests to the resource using 235 the URI. 237 Path Segment 239 Informally, the characters found between slashes ("/") in a URI. 240 Formally, as defined in Section 3.3 of [RFC3986]. 242 Binding 244 A relation between a single path segment (in a collection) and a 245 resource. A binding is part of the state of a collection. If two 246 different collections contain a binding between the same path 247 segment and the same resource, these are two distinct bindings. 248 So for a collection C, a path segment S, and a resource R, the 249 binding can be thought of as C:(S -> R). Bindings create URI 250 mappings, and hence allow requests to be sent to a single resource 251 from multiple locations in a URI namespace. For example, given a 252 collection C (accessible through the URI 253 http://www.example.com/CollX), a path segment S (equal to 254 "foo.html"), and a resource R, then creating the binding C: (S -> 255 R) makes it possible to use the URI 256 http://www.example.com/CollX/foo.html to access R. 258 Collection 260 A resource that contains, as part of its state, a set of bindings 261 that identify internal member resources. 263 Internal Member URI 265 The URI that identifies an internal member of a collection, and 266 that consists of the URI for the collection, followed by a slash 267 character ('/'), followed by the path segment of the binding for 268 that internal member. 270 1.2. Method Preconditions and Postconditions 272 See Section 16 of [draft-ietf-webdav-rfc2518bis] for the definitions 273 of "precondition" and "postcondition". 275 2. Overview of Bindings 277 Bindings are part of the state of a collection. They define the 278 internal members of the collection, and the names of those internal 279 members. 281 Bindings are added and removed by a variety of existing HTTP methods. 282 A method that creates a new resource, such as PUT, COPY, and MKCOL, 283 adds a binding. A method that deletes a resource, such as DELETE, 284 removes a binding. A method that moves a resource (e.g. MOVE) both 285 adds a binding (in the destination collection) and removes a binding 286 (in the source collection). The BIND method introduced here provides 287 a mechanism for adding a second binding to an existing resource. 288 There is no difference between an initial binding added by PUT, COPY, 289 or MKCOL, and additional bindings added with BIND. 291 It would be very undesirable if one binding could be destroyed as a 292 side effect of operating on the resource through a different binding. 293 In particular, the removal of one binding to a resource (e.g. with a 294 DELETE or a MOVE) MUST NOT disrupt another binding to that resource, 295 e.g. by turning that binding into a dangling path segment. The 296 server MUST NOT reclaim system resources after removing one binding, 297 while other bindings to the resource remain. In other words, the 298 server MUST maintain the integrity of a binding. It is permissible, 299 however, for future method definitions (e.g., a DESTROY method) to 300 have semantics that explicitly remove all bindings and/or immediately 301 reclaim system resources. 303 2.1. Bindings to Collections 305 Creating a new binding to a collection makes each resource associated 306 with a binding in that collection accessible via a new URI, and thus 307 creates new URI mappings to those resources but no new bindings. 309 For example, suppose a new binding CollY is created for collection C1 310 in the figure below. It immediately becomes possible to access 311 resource R1 using the URI /CollY/x.gif and to access resource R2 312 using the URI /CollY/y.jpg, but no new bindings for these child 313 resources were created. This is because bindings are part of the 314 state of a collection, and associate a URI that is relative to that 315 collection with its target resource. No change to the bindings in 316 Collection C1 is needed to make its children accessible using /CollY/ 317 x.gif and /CollY/y.jpg. 319 +-------------------------+ 320 | Root Collection | 321 | bindings: | 322 | CollX CollY | 323 +-------------------------+ 324 | / 325 | / 326 | / 327 +------------------+ 328 | Collection C1 | 329 | bindings: | 330 | x.gif y.jpg | 331 +------------------+ 332 | \ 333 | \ 334 | \ 335 +-------------+ +-------------+ 336 | Resource R1 | | Resource R2 | 337 +-------------+ +-------------+ 339 2.1.1. Bind loops 341 Bindings to collections can result in loops, which servers MUST 342 detect when processing "Depth: infinity" requests. It is sometimes 343 possible to complete an operation in spite of the presence of a loop. 344 For instance, a PROPFIND can still succeed if the server uses the new 345 status code 208 (Already Reported) defined in Section 7.1. 347 However, the 506 (Loop Detected) status code is defined in 348 Section 7.2 for use in contexts where an operation is terminated 349 because a loop was encountered. 351 2.2. URI Mappings Created by a new Binding 353 Suppose a binding from "Binding-Name" to resource R is to be added to 354 a collection, C. Then if C-MAP is the set of URIs that were mapped to 355 C before the BIND request, then for each URI "C-URI" in C-MAP, the 356 URI "C-URI/Binding-Name" is mapped to resource R following the BIND 357 request. 359 For example, if a binding from "foo.html" to R is added to a 360 collection C, and if the following URIs are mapped to C: 362 http://www.example.com/A/1/ 363 http://example.com/A/one/ 364 then the following new mappings to R are introduced: 366 http://www.example.com/A/1/foo.html 367 http://example.com/A/one/foo.html 369 Note that if R is a collection, additional URI mappings are created 370 to the descendents of R. Also, note that if a binding is made in 371 collection C to C itself (or to a parent of C), an infinite number of 372 mappings are introduced. 374 For example, if a binding from "myself" to C is then added to C, the 375 following infinite number of additional mappings to C are introduced: 377 http://www.example.com/A/1/myself 378 http://www.example.com/A/1/myself/myself 379 ... 381 and the following infinite number of additional mappings to R are 382 introduced: 384 http://www.example.com/A/1/myself/foo.html 385 http://www.example.com/A/1/myself/myself/foo.html 386 ... 388 2.3. COPY and Bindings 390 As defined in Section 9.8 of [draft-ietf-webdav-rfc2518bis], COPY 391 causes the resource identified by the Request-URI to be duplicated, 392 and makes the new resource accessible using the URI specified in the 393 Destination header. Upon successful completion of a COPY, a new 394 binding is created between the last path segment of the Destination 395 header, and the destination resource. The new binding is added to 396 its parent collection, identified by the Destination header minus its 397 final segment. 399 The following figure shows an example: Suppose that a COPY is issued 400 to URI-3 for resource R (which is also mapped to URI-1 and URI-2), 401 with the Destination header set to URI-X. After successful 402 completion of the COPY operation, resource R is duplicated to create 403 resource R', and a new binding has been created which creates at 404 least the URI mapping between URI-X and the new resource (although 405 other URI mappings may also have been created). 407 URI-1 URI-2 URI-3 URI-X 408 | | | | 409 | | | <---- URI Mappings ----> | 410 | | | | 411 +---------------------+ +------------------------+ 412 | Resource R | | Resource R' | 413 +---------------------+ +------------------------+ 415 It might be thought that a COPY request with "Depth: 0" on a 416 collection would duplicate its bindings, since bindings are part of 417 the collection's state. This is not the case, however. The 418 definition of Depth in [draft-ietf-webdav-rfc2518bis] makes it clear 419 that a "Depth: 0" request does not apply to a collection's members. 420 Consequently, a COPY with "Depth: 0" does not duplicate the bindings 421 contained by the collection. 423 If a COPY request causes an existing resource to be updated, the 424 bindings to that resource MUST be unaffected by the COPY request. 425 Using the preceding example, suppose that a COPY request is issued to 426 URI-X for resource R', with the Destination header set to URI-2. The 427 content and dead properties of resource R would be updated to be a 428 copy of those of resource R', but the mappings from URI-1, URI-2, and 429 URI-3 to resource R remain unaffected. If because of multiple 430 bindings to a resource, more than one source resource updates a 431 single destination resource, the order of the updates is server 432 defined. 434 If a COPY request would cause a new resource to be created as a copy 435 of an existing resource, and that COPY request has already created a 436 copy of that existing resource, the COPY request instead creates 437 another binding to the previous copy, instead of creating a new 438 resource. 440 2.3.1. Example: COPY with 'Depth: infinity' in presence of bind loops 442 As an example of how COPY with Depth infinity would work in the 443 presence of bindings, consider the following collection: 445 +------------------+ 446 | Root Collection | 447 | bindings: | 448 | CollX | 449 +------------------+ 450 | 451 | 452 +-------------------------------+ 453 | Collection C1 |<-------+ 454 | bindings: | | 455 | x.gif CollY | | 456 +-------------------------------+ | 457 | \ (creates loop) | 458 | \ | 459 +-------------+ +------------------+ | 460 | Resource R1 | | Collection C2 | | 461 +-------------+ | bindings: | | 462 | y.gif CollZ | | 463 +------------------+ | 464 | | | 465 | +--------+ 466 | 467 +-------------+ 468 | Resource R2 | 469 +-------------+ 471 If a COPY with Depth infinity is submitted to /CollX, with 472 destination of /CollA, the outcome of the copy operation is: 474 +------------------+ 475 | Root Collection | 476 | bindings: | 477 | CollX CollA | 478 +------------------+ 479 | | 480 | +---------------------------+ 481 | | 482 +-------------------+ | 483 | Collection C1 |<------------------+ | 484 | bindings: | | | 485 | x.gif CollY | | | 486 +-------------------+ | | 487 | \ (creates loop) | | 488 | \ | | 489 +-------------+ +-----------------+ | | 490 | Resource R1 | | Collection C2 | | | 491 +-------------+ | bindings: | | | 492 | y.gif CollZ | | | 493 +-----------------+ | | 494 | | | | 495 | +-------+ | 496 | | 497 +-------------+ | 498 | Resource R2 | | 499 +-------------+ | 500 | 501 +-------------------------------+ 502 | 503 +-------------------+ 504 | Collection C3 |<------------------+ 505 | bindings: | | 506 | x.gif CollY | | 507 +-------------------+ | 508 | \ (creates loop) | 509 | \ | 510 +-------------+ +-----------------+ | 511 | Resource R3 | | Collection C4 | | 512 +-------------+ | bindings: | | 513 | y.gif CollZ | | 514 +-----------------+ | 515 | | | 516 | +-------+ 517 | 518 +-------------+ 519 | Resource R4 | 520 +-------------+ 522 2.3.2. Example: COPY with 'Depth: infinity' with multiple bindings to a 523 leaf resource 525 Given the following collection hierarchy: 527 +------------------+ 528 | Root Collection | 529 | bindings: | 530 | CollX | 531 +------------------+ 532 | 533 | 534 | 535 +----------------+ 536 | Collection C1 | 537 | bindings: | 538 | x.gif y.gif | 539 +----------------+ 540 | | 541 | | 542 +-------------+ 543 | Resource R1 | 544 +-------------+ 546 A COPY of /CollX with Depth infinity to /CollY results in the 547 following collection hierarchy: 549 +------------------+ 550 | Root Collection | 551 | bindings: | 552 | CollX CollY | 553 +------------------+ 554 | \ 555 | \ 556 | \ 557 +----------------+ +-----------------+ 558 | Collection C1 | | Collection C2 | 559 | bindings: | | bindings: | 560 | x.gif y.gif | | x.gif y.gif | 561 +----------------+ +-----------------+ 562 | | | | 563 | | | | 564 +-------------+ +-------------+ 565 | Resource R1 | | Resource R2 | 566 +-------------+ +-------------+ 568 2.4. DELETE and Bindings 570 When there are multiple bindings to a resource, a DELETE applied to 571 that resource MUST NOT remove any bindings to that resource other 572 than the one identified by the Request-URI. For example, suppose the 573 collection identified by the URI "/a" has a binding named "x" to a 574 resource R, and another collection identified by "/b" has a binding 575 named "y" to the same resource R. Then a DELETE applied to "/a/x" 576 removes the binding named "x" from "/a" but MUST NOT remove the 577 binding named "y" from "/b" (i.e. after the DELETE, "/y/b" continues 578 to identify the resource R). 580 When DELETE is applied to a collection, it MUST NOT modify the 581 membership of any other collection that is not itself a member of the 582 collection being deleted. For example, if both "/a/.../x" and 583 "/b/.../y" identify the same collection, C, then applying DELETE to 584 "/a" must not delete an internal member from C or from any other 585 collection that is a member of C, because that would modify the 586 membership of "/b". 588 If a collection supports the UNBIND method (see Section 5), a DELETE 589 of an internal member of a collection MAY be implemented as an UNBIND 590 request. In this case, applying DELETE to a Request-URI has the 591 effect of removing the binding identified by the final segment of the 592 Request-URI from the collection identified by the Request-URI minus 593 its final segment. Although [draft-ietf-webdav-rfc2518bis] allows a 594 DELETE to be a non-atomic operation, when the DELETE operation is 595 implemented as an UNBIND, the operation is atomic. In particular, a 596 DELETE on a hierarchy of resources is simply the removal of a binding 597 to the collection identified by the Request-URI. 599 2.5. MOVE and Bindings 601 When MOVE is applied to a resource, the other bindings to that 602 resource MUST be unaffected, and if the resource being moved is a 603 collection, the bindings to any members of that collection MUST be 604 unaffected. Also, if MOVE is used with Overwrite:T to delete an 605 existing resource, the constraints specified for DELETE apply. 607 If the destination collection of a MOVE request supports the REBIND 608 method (see Section 6), a MOVE of a resource into that collection MAY 609 be implemented as a REBIND request. Although 610 [draft-ietf-webdav-rfc2518bis] allows a MOVE to be a non-atomic 611 operation, when the MOVE operation is implemented as a REBIND, the 612 operation is atomic. In particular, applying a MOVE to a Request-URI 613 and a Destination URI has the effect of removing a binding to a 614 resource (at the Request-URI), and creating a new binding to that 615 resource (at the Destination URI). Even when the Request-URI 616 identifies a collection, the MOVE operation involves only removing 617 one binding to that collection and adding another. 619 As an example, suppose that a MOVE is issued to URI-3 for resource R 620 below (which is also mapped to URI-1 and URI-2), with the Destination 621 header set to URI-X. After successful completion of the MOVE 622 operation, a new binding has been created which creates the URI 623 mapping between URI-X and resource R. The binding corresponding to 624 the final segment of URI-3 has been removed, which also causes the 625 URI mapping between URI-3 and R to be removed. If resource R were a 626 collection, old URI-3 based mappings to members of R would have been 627 removed, and new URI-X based mappings to members of R would have been 628 created. 630 >> Before Request: 632 URI-1 URI-2 URI-3 633 | | | 634 | | | <---- URI Mappings 635 | | | 636 +---------------------+ 637 | Resource R | 638 +---------------------+ 640 >> After Request: 642 URI-1 URI-2 URI-X 643 | | | 644 | | | <---- URI Mappings 645 | | | 646 +---------------------+ 647 | Resource R | 648 +---------------------+ 650 2.6. PROPFIND and Bindings 652 Consistent with [draft-ietf-webdav-rfc2518bis], the value of a dead 653 property MUST be independent of the number of bindings to its host 654 resource or of the path submitted to PROPFIND. On the other hand, 655 the behaviour for each live property depends on its individual 656 definition (for example, see [RFC3744], Section 5, paragraph 2). 658 2.7. Determining Whether Two Bindings Are to the Same Resource 660 It is useful to have some way of determining whether two bindings are 661 to the same resource. Two resources might have identical contents 662 and properties, but not be the same resource (e.g. an update to one 663 resource does not affect the other resource). 665 The REQUIRED DAV:resource-id property defined in Section 3.1 is a 666 resource identifier, which MUST be unique across all resources for 667 all time. If the values of DAV:resource-id returned by PROPFIND 668 requests through two bindings are identical character by character, 669 the client can be assured that the two bindings are to the same 670 resource. 672 The DAV:resource-id property is created, and its value assigned, when 673 the resource is created. The value of DAV:resource-id MUST NOT be 674 changed. Even after the resource is no longer accessible through any 675 URI, that value MUST NOT be reassigned to another resource's DAV: 676 resource-id property. 678 Any method that creates a new resource MUST assign a new, unique 679 value to its DAV:resource-id property. For example, a PUT applied to 680 a null resource, COPY (when not overwriting an existing target) and 681 CHECKIN (see [RFC3253], Section 4.4) must assign a new, unique value 682 to the DAV:resource-id property of the new resource they create. 684 On the other hand, any method that affects an existing resource must 685 not change the value of its DAV:resource-id property. Specifically, 686 a PUT or a COPY that updates an existing resource must not change the 687 value of its DAV:resource-id property. A REBIND, since it does not 688 create a new resource, but only changes the location of an existing 689 resource, must not change the value of the DAV:resource-id property. 691 2.8. Discovering the Bindings to a Resource 693 An OPTIONAL DAV:parent-set property on a resource provides a list of 694 the bindings that associate a collection and a URI segment with that 695 resource. If the DAV:parent-set property exists on a given resource, 696 it MUST contain a complete list of all bindings to that resource that 697 the client is authorized to see. When deciding whether to support 698 the DAV:parent-set property, server implementers / administrators 699 should balance the benefits it provides against the cost of 700 maintaining the property and the security risks enumerated in 701 Sections 10.4 and 10.5. 703 3. Properties 705 The bind feature introduces the properties defined below. 707 A DAV:allprop PROPFIND request SHOULD NOT return any of the 708 properties defined by this document. This allows a binding server to 709 perform efficiently when a naive client, which does not understand 710 the cost of asking a server to compute all possible live properties, 711 issues a DAV:allprop PROPFIND request. 713 3.1. DAV:resource-id Property 715 The DAV:resource-id property is a REQUIRED property that enables 716 clients to determine whether two bindings are to the same resource. 717 The value of DAV:resource-id is a URI, and may use any registered URI 718 scheme that guarantees the uniqueness of the value across all 719 resources for all time (e.g. the urn:uuid: URN namespace defined in 720 [RFC4122] or the opaquelocktoken: URI scheme defined in 721 [draft-ietf-webdav-rfc2518bis]). 723 725 3.2. DAV:parent-set Property 727 The DAV:parent-set property is an OPTIONAL property that enables 728 clients to discover what collections contain a binding to this 729 resource (i.e. what collections have that resource as an internal 730 member). It contains an of href/segment pair for each collection 731 that has a binding to the resource. The href identifies the 732 collection, and the segment identifies the binding name of that 733 resource in that collection. 735 A given collection MUST appear only once in the DAV:parent-set for 736 any given binding, even if there are multiple URI mappings to that 737 collection. 739 740 741 742 745 3.2.1. Example for DAV:parent-set property 747 For example, if collection C1 is mapped to both /CollX and /CollY, 748 and C1 contains a binding named "x.gif" to a resource R1, then either 749 [/CollX, x.gif] or [/CollY, x.gif] can appear in the DAV:parent-set 750 of R1, but not both. But if C1 also had a binding named "y.gif" to 751 R1, then there would be two entries for C1 in the DAV:binding-set of 752 R1 (i.e. both [/CollX, x.gif] and [/CollX, y.gif] or, alternatively, 753 both [/CollY, x.gif] and [/CollY, y.gif]). 755 +-------------------------+ 756 | Root Collection | 757 | bindings: | 758 | CollX CollY | 759 +-------------------------+ 760 | / 761 | / 762 | / 763 +-----------------+ 764 | Collection C1 | 765 | bindings: | 766 | x.gif y.gif | 767 +-----------------+ 768 | | 769 | | 770 | | 771 +--------------+ 772 | Resource R1 | 773 +--------------+ 775 In this case, one possible value for DAV:parent-set property on 776 "/CollX/x.gif" would be: 778 779 780 /CollX 781 x.gif 782 783 784 /CollX 785 y.gif 786 787 789 4. BIND Method 791 The BIND method modifies the collection identified by the Request- 792 URI, by adding a new binding from the segment specified in the BIND 793 body to the resource identified in the BIND body. 795 If a server cannot guarantee the integrity of the binding, the BIND 796 request MUST fail. Note that it is especially difficult to maintain 797 the integrity of cross-server bindings. Unless the server where the 798 resource resides knows about all bindings on all servers to that 799 resource, it may unwittingly destroy the resource or make it 800 inaccessible without notifying another server that manages a binding 801 to the resource. For example, if server A permits creation of a 802 binding to a resource on server B, server A must notify server B 803 about its binding and must have an agreement with B that B will not 804 destroy the resource while A's binding exists. Otherwise server B 805 may receive a DELETE request that it thinks removes the last binding 806 to the resource and destroy the resource while A's binding still 807 exists. The precondition DAV:cross-server-binding is defined below 808 for cases where servers fail cross-server BIND requests because they 809 cannot guarantee the integrity of cross-server bindings. 811 By default, if there already is a binding for the specified segment 812 in the collection, the new binding replaces the existing binding. 813 This default binding replacement behavior can be overridden using the 814 Overwrite header defined in Section 10.6 of 815 [draft-ietf-webdav-rfc2518bis]. 817 If a BIND request fails, the server state preceding the request MUST 818 be restored. This method is unsafe and idempotent (see [RFC2616], 819 Section 9.1). 821 Marshalling: 823 The request MAY include an Overwrite header. 825 The request body MUST be a DAV:bind XML element. 827 829 If the request succeeds, the server MUST return 201 (Created) when 830 a new binding was created and 200 (OK) when an existing binding 831 was replaced. 833 If a response body for a successful request is included, it MUST 834 be a DAV:bind-response XML element. Note that this document does 835 not define any elements for the BIND response body, but the DAV: 836 bind-response element is defined to ensure interoperability 837 between future extensions that do define elements for the BIND 838 response body. 840 842 Preconditions: 844 (DAV:bind-into-collection): The Request-URI MUST identify a 845 collection. 847 (DAV:bind-source-exists): The DAV:href element MUST identify a 848 resource. 850 (DAV:binding-allowed): The resource identified by the DAV:href 851 supports multiple bindings to it. 853 (DAV:cross-server-binding): If the resource identified by the DAV: 854 href element in the request body is on another server from the 855 collection identified by the Request-URI, the server MUST support 856 cross-server bindings. 858 (DAV:name-allowed): The name specified by the DAV:segment is 859 available for use as a new binding name. 861 (DAV:can-overwrite): If the collection already contains a binding 862 with the specified path segment, and if an Overwrite header is 863 included, the value of the Overwrite header MUST be "T". 865 (DAV:cycle-allowed): If the DAV:href element identifies a 866 collection, and if the Request-URI identifies a collection that is 867 a member of that collection, the server MUST support cycles in the 868 URI namespace. 870 (DAV:locked-update-allowed): If the collection identified by the 871 Request-URI is write-locked, then the appropriate token MUST be 872 specified in an If request header. 874 (DAV:locked-overwrite-allowed): If the collection already contains 875 a binding with the specified path segment, and if that binding is 876 protected by a write-lock, then the appropriate token MUST be 877 specified in an If request header. 879 Postconditions: 881 (DAV:new-binding): The collection MUST have a binding that maps 882 the segment specified in the DAV:segment element in the request 883 body, to the resource identified by the DAV:href element in the 884 request body. 886 4.1. Example: BIND 888 >> Request: 890 BIND /CollY HTTP/1.1 891 Host: www.example.com 892 Content-Type: application/xml; charset="utf-8" 893 Content-Length: xxx 895 896 897 bar.html 898 http://www.example.com/CollX/foo.html 899 901 >> Response: 903 HTTP/1.1 201 Created 905 The server added a new binding to the collection, 906 "http://www.example.com/CollY", associating "bar.html" with the 907 resource identified by the URI 908 "http://www.example.com/CollX/foo.html". Clients can now use the URI 909 "http://www.example.com/CollY/bar.html" to submit requests to that 910 resource. 912 5. UNBIND Method 914 The UNBIND method modifies the collection identified by the Request- 915 URI, by removing the binding identified by the segment specified in 916 the UNBIND body. 918 Once a resource is unreachable by any URI mapping, the server MAY 919 reclaim system resources associated with that resource. If UNBIND 920 removes a binding to a resource, but there remain URI mappings to 921 that resource, the server MUST NOT reclaim system resources 922 associated with the resource. 924 If an UNBIND request fails, the server state preceding the request 925 MUST be restored. This method is unsafe and idempotent (see 926 [RFC2616], Section 9.1). 928 Marshalling: 930 The request body MUST be a DAV:unbind XML element. 932 933 If the request succeeds, the server MUST return 200 (OK) when the 934 binding was successfully deleted. 936 If a response body for a successful request is included, it MUST 937 be a DAV:unbind-response XML element. Note that this document 938 does not define any elements for the UNBIND response body, but the 939 DAV:unbind-response element is defined to ensure interoperability 940 between future extensions that do define elements for the UNBIND 941 response body. 943 945 Preconditions: 947 (DAV:unbind-from-collection): The Request-URI MUST identify a 948 collection. 950 (DAV:unbind-source-exists): The DAV:segment element MUST identify 951 a binding in the collection identified by the Request-URI. 953 (DAV:locked-update-allowed): If the collection identified by the 954 Request-URI is write-locked, then the appropriate token MUST be 955 specified in the request. 957 (DAV:protected-url-deletion-allowed): If the binding identified by 958 the segment is protected by a write-lock, then the appropriate 959 token MUST be specified in the request. 961 Postconditions: 963 (DAV:binding-deleted): The collection MUST NOT have a binding for 964 the segment specified in the DAV:segment element in the request 965 body. 967 (DAV:lock-deleted): If the internal member URI of the binding 968 specified by the Request-URI and the DAV:segment element in the 969 request body was protected by a write-lock at the time of the 970 request, that write-lock must have been deleted by the request. 972 5.1. Example: UNBIND 974 >> Request: 976 UNBIND /CollX HTTP/1.1 977 Host: www.example.com 978 Content-Type: application/xml; charset="utf-8" 979 Content-Length: xxx 981 982 983 foo.html 984 986 >> Response: 988 HTTP/1.1 200 OK 990 The server removed the binding named "foo.html" from the collection, 991 "http://www.example.com/CollX". A request to the resource named 992 "http://www.example.com/CollX/foo.html" will return a 404 (Not Found) 993 response. 995 6. REBIND Method 997 The REBIND method removes a binding to a resource from a collection, 998 and adds a binding to that resource into the collection identified by 999 the Request-URI. The request body specifies the binding to be added 1000 (segment) and the old binding to be removed (href). It is 1001 effectively an atomic form of a MOVE request, and MUST be treated the 1002 same way as MOVE for the purpose of determining access permissions. 1004 If a REBIND request fails, the server state preceding the request 1005 MUST be restored. This method is unsafe and idempotent (see 1006 [RFC2616], Section 9.1). 1008 Marshalling: 1010 The request MAY include an Overwrite header. 1012 The request body MUST be a DAV:rebind XML element. 1014 1016 If the request succeeds, the server MUST return 201 (Created) when 1017 a new binding was created and 200 (OK) when an existing binding 1018 was replaced. 1020 If a response body for a successful request is included, it MUST 1021 be a DAV:rebind-response XML element. Note that this document 1022 does not define any elements for the REBIND response body, but the 1023 DAV:rebind-response element is defined to ensure interoperability 1024 between future extensions that do define elements for the REBIND 1025 response body. 1027 1029 Preconditions: 1031 (DAV:rebind-into-collection): The Request-URI MUST identify a 1032 collection. 1034 (DAV:rebind-source-exists): The DAV:href element MUST identify a 1035 resource. 1037 (DAV:cross-server-binding): If the resource identified by the DAV: 1038 href element in the request body is on another server from the 1039 collection identified by the Request-URI, the server MUST support 1040 cross-server bindings. 1042 (DAV:name-allowed): The name specified by the DAV:segment is 1043 available for use as a new binding name. 1045 (DAV:can-overwrite): If the collection already contains a binding 1046 with the specified path segment, and if an Overwrite header is 1047 included, the value of the Overwrite header MUST be "T". 1049 (DAV:cycle-allowed): If the DAV:href element identifies a 1050 collection, and if the Request-URI identifies a collection that is 1051 a member of that collection, the server MUST support cycles in the 1052 URI namespace. 1054 (DAV:locked-update-allowed): If the collection identified by the 1055 Request-URI is write-locked, then the appropriate token MUST be 1056 specified in the request. 1058 (DAV:protected-url-modification-allowed): If the collection 1059 identified by the Request-URI already contains a binding with the 1060 specified path segment, and if that binding is protected by a 1061 write-lock, then the appropriate token MUST be specified in the 1062 request. 1064 (DAV:locked-source-collection-update-allowed): If the collection 1065 identified by the parent collection prefix of the DAV:href URI is 1066 write-locked, then the appropriate token MUST be specified in the 1067 request. 1069 (DAV:protected-source-url-deletion-allowed): If the DAV:href URI 1070 is protected by a write lock, then the appropriate token MUST be 1071 specified in the request. 1073 Postconditions: 1075 (DAV:new-binding): The collection MUST have a binding that maps 1076 the segment specified in the DAV:segment element in the request 1077 body, to the resource that was identified by the DAV:href element 1078 in the request body. 1080 (DAV:binding-deleted): The URL specified in the DAV:href element 1081 in the request body MUST NOT be mapped to a resource. 1083 (DAV:lock-deleted): If the URL specified in the DAV:href element 1084 in the request body was protected by a write-lock at the time of 1085 the request, that write-lock must have been deleted by the 1086 request. 1088 6.1. Example: REBIND 1090 >> Request: 1092 REBIND /CollX HTTP/1.1 1093 Host: www.example.com 1094 Content-Type: application/xml; charset="utf-8" 1095 Content-Length: xxx 1097 1098 1099 foo.html 1100 http://www.example.com/CollY/bar.html 1101 1103 >> Response: 1105 HTTP/1.1 200 OK 1107 The server added a new binding to the collection, 1108 "http://www.example.com/CollX", associating "foo.html" with the 1109 resource identified by the URI 1110 "http://www.example.com/CollY/bar.html", and removes the binding 1111 named "bar.html" from the collection identified by the URI 1112 "http://www.example.com/CollY". Clients can now use the URI 1113 "http://www.example.com/CollX/foo.html" to submit requests to that 1114 resource, and requests on the URI 1115 "http://www.example.com/CollY/bar.html" will fail with a 404 (Not 1116 Found) response. 1118 6.2. Example: REBIND in presence of locks and bind loops 1120 To illustrate the effects of locks and bind loops on a REBIND 1121 operation, consider the following collection: 1123 +------------------+ 1124 | Root Collection | 1125 | bindings: | 1126 | CollW | 1127 +------------------+ 1128 | 1129 | 1130 | 1131 +-------------------------------+ 1132 | Collection C1 |<--------+ 1133 | LOCKED infinity | | 1134 | (lock token L1) | | 1135 | bindings: | | 1136 | CollX CollY | | 1137 +-------------------------------+ | 1138 | | | 1139 | | (creates loop) | 1140 | | | 1141 +-----------------+ +------------------+ | 1142 | Collection C2 | | Collection C3 | | 1143 | (inherit lock) | | (inherit lock) | | 1144 | (lock token L1) | | (lock token L1) | | 1145 | bindings: | | bindings: | | 1146 | {none} | | y.gif CollZ | | 1147 +-----------------+ +------------------+ | 1148 | | | 1149 | +-----+ 1150 | 1151 +---------------------------+ 1152 | Resource R2 | 1153 | (lock inherited from C1) | 1154 | (lock token L1) | 1155 +---------------------------+ 1157 (where L1 is "opaquelocktoken:f92d4fae-7012-11ab-a765-00c0ca1f6bf9"). 1159 Note that the binding between CollZ and C1 creates a loop in the 1160 containment hierarchy. Servers are not required to support such 1161 loops, though the server in this example does. 1163 The REBIND request below will remove the segment "CollZ" from C3 and 1164 add a new binding from "CollA" to the collection C2. 1166 REBIND /CollW/CollX HTTP/1.1 1167 Host: www.example.com 1168 If: () 1169 Content-Type: application/xml; charset="utf-8" 1170 Content-Length: xxx 1172 1173 1174 CollA 1175 /CollW/CollY/CollZ 1176 1177 The outcome of the REBIND operation is: 1179 +------------------+ 1180 | Root Collection | 1181 | bindings: | 1182 | CollW | 1183 +------------------+ 1184 | 1185 | 1186 | 1187 +-------------------------------+ 1188 | Collection C1 | 1189 | LOCKED infinity | 1190 | (lock token L1) | 1191 | bindings: | 1192 | CollX CollY | 1193 +-------------------------------+ 1194 | ^ | 1195 | | | 1196 +-----------------+ | +------------------+ 1197 | Collection C2 | | | Collection C3 | 1198 |(inherited lock) | | | (inherited lock) | 1199 |(lock token L1) | | | (lock token L1) | 1200 | bindings: | | | bindings: | 1201 | CollA | | | y.gif | 1202 +-----------------+ | +------------------+ 1203 | | | 1204 +---------------+ | 1205 (creates loop) | 1206 +---------------------------+ 1207 | Resource R2 | 1208 | (inherited lock from C1) | 1209 | (lock token L1) | 1210 +---------------------------+ 1212 7. Additional Status Codes 1214 7.1. 208 Already Reported 1216 The 208 (Already Reported) status code can be used inside a DAV: 1217 propstat response element to avoid enumerating the internal members 1218 of multiple bindings to the same collection repeatedly. For each 1219 binding to a collection inside the request's scope, only one will be 1220 reported with a 200 status, while subsequent DAV:response elements 1221 for all other bindings will use the 208 status, and no DAV:response 1222 elements for their descendants are included. 1224 Note that the 208 status will only occur for "Depth: infinity" 1225 requests, and that it is of particular importance when the multiple 1226 collection bindings cause a bind loop as discussed in Section 2.2. 1228 A client can request the DAV:resource-id property in a PROPFIND 1229 request to guarantee that they can accurately reconstruct the binding 1230 structure of a collection with multiple bindings to a single 1231 resource. 1233 For backward compatibility with clients not aware of the 208 status 1234 code appearing in multistatus response bodies, it SHOULD NOT be used 1235 unless the client has signalled support for this specification using 1236 the "DAV" request header (see Section 8.2). Instead, a 506 status 1237 should be returned when a binding loop is discovered. This allows 1238 the server to return the 506 as the top level return status, if it 1239 discovers it before it started the response, or in the middle of a 1240 multistatus, if it discovers it in the middle of streaming out a 1241 multistatus response. 1243 7.1.1. Example: PROPFIND by bind-aware client 1245 For example, consider a PROPFIND request on /Coll (bound to 1246 collection C), where the members of /Coll are /Coll/Foo (bound to 1247 resource R) and /Coll/Bar (bound to collection C). 1249 >> Request: 1251 PROPFIND /Coll/ HTTP/1.1 1252 Host: www.example.com 1253 Depth: infinity 1254 DAV: bind 1255 Content-Type: application/xml; charset="utf-8" 1256 Content-Length: xxx 1258 1259 1260 1261 1262 1263 1264 1266 >> Response: 1268 HTTP/1.1 207 Multi-Status 1269 Content-Type: application/xml; charset="utf-8" 1270 Content-Length: xxx 1272 1273 1274 1275 http://www.example.com/Coll/ 1276 1277 1278 Loop Demo 1279 1280 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf8 1282 1283 1284 HTTP/1.1 200 OK 1285 1286 1287 1288 http://www.example.com/Coll/Foo 1289 1290 1291 Bird Inventory 1292 1293 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf9 1295 1296 1297 HTTP/1.1 200 OK 1298 1299 1300 1301 http://www.example.com/Coll/Bar 1302 1303 1304 Loop Demo 1305 1306 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf8 1308 1309 1310 HTTP/1.1 208 Already Reported 1311 1312 1313 1315 7.1.2. Example: PROPFIND by non-bind-aware client 1317 In this example, the client isn't aware of the 208 status code 1318 introduced by this specification. As the "Depth: infinity" PROPFIND 1319 request would cause a loop condition, the whole request is rejected 1320 with a 506 status. 1322 >> Request: 1324 PROPFIND /Coll/ HTTP/1.1 1325 Host: www.example.com 1326 Depth: infinity 1327 Content-Type: application/xml; charset="utf-8" 1328 Content-Length: xxx 1330 1331 1332 1333 1335 >> Response: 1337 HTTP/1.1 506 Loop Detected 1339 7.2. 506 Loop Detected 1341 The 506 (Loop Detected) status code indicates that the server 1342 terminated an operation because it encountered an infinite loop while 1343 processing a request with "Depth: infinity". This status indicates 1344 that the entire operation failed. 1346 8. Capability discovery 1348 8.1. OPTIONS method 1350 If the server supports bindings, it MUST return the compliance class 1351 name "bind" as a field in the "DAV" response header (see 1352 [draft-ietf-webdav-rfc2518bis], Section 10.1) from an OPTIONS request 1353 on any resource implemented by that server. A value of "bind" in the 1354 "DAV" header MUST indicate that the server supports all MUST level 1355 requirements and REQUIRED features specified in this document. 1357 8.2. 'DAV' request header 1359 Clients SHOULD signal support for all MUST level requirements and 1360 REQUIRED features by submitting a "DAV" request header containing the 1361 compliance class name "bind". In particular, the client MUST 1362 understand the 208 status code defined in Section 7.1. 1364 9. Relationship to WebDAV Access Control Protocol 1366 BIND and REBIND behave the same as MOVE with respect to the DAV:acl 1367 property (see [RFC3744], Section 7.3). 1369 10. Security Considerations 1371 This section is provided to make WebDAV implementors aware of the 1372 security implications of this protocol. 1374 All of the security considerations of HTTP/1.1 and the WebDAV 1375 Distributed Authoring Protocol specification also apply to this 1376 protocol specification. In addition, bindings introduce several new 1377 security concerns and increase the risk of some existing threats. 1378 These issues are detailed below. 1380 10.1. Privacy Concerns 1382 In a context where cross-server bindings are supported, creating 1383 bindings on a trusted server may make it possible for a hostile agent 1384 to induce users to send private information to a target on a 1385 different server. 1387 10.2. Bind Loops 1389 Although bind loops were already possible in HTTP 1.1, the 1390 introduction of the BIND method creates a new avenue for clients to 1391 create loops accidentally or maliciously. If the binding and its 1392 target are on the same server, the server may be able to detect BIND 1393 requests that would create loops. Servers are required to detect 1394 loops that are caused by bindings to collections during the 1395 processing of any requests with "Depth: infinity". 1397 10.3. Bindings, and Denial of Service 1399 Denial of service attacks were already possible by posting URIs that 1400 were intended for limited use at heavily used Web sites. The 1401 introduction of BIND creates a new avenue for similar denial of 1402 service attacks. If cross-server bindings are supported, clients can 1403 now create bindings at heavily used sites to target locations that 1404 were not designed for heavy usage. 1406 10.4. Private Locations May Be Revealed 1408 If the DAV:parent-set property is maintained on a resource, the 1409 owners of the bindings risk revealing private locations. The 1410 directory structures where bindings are located are available to 1411 anyone who has access to the DAV:parent-set property on the resource. 1412 Moving a binding may reveal its new location to anyone with access to 1413 DAV:parent-set on its resource. 1415 10.5. DAV:parent-set and Denial of Service 1417 If the server maintains the DAV:parent-set property in response to 1418 bindings created in other administrative domains, it is exposed to 1419 hostile attempts to make it devote resources to adding bindings to 1420 the list. 1422 11. Internationalization Considerations 1424 All internationalization considerations mentioned in 1425 [draft-ietf-webdav-rfc2518bis] also apply to this document. 1427 12. IANA Considerations 1429 There are no IANA considerations related to this specification. 1431 13. Acknowledgements 1433 This document is the collaborative product of the authors and Tyson 1434 Chihaya, Jim Davis, Chuck Fay and Judith Slein. This draft has 1435 benefited from thoughtful discussion by Jim Amsden, Peter Carlson, 1436 Steve Carter, Ken Coar, Ellis Cohen, Dan Connolly, Bruce Cragun, 1437 Spencer Dawkins, Mark Day, Rajiv Dulepet, David Durand, Lisa 1438 Dusseault, Stefan Eissing, Roy Fielding, Yaron Goland, Joe 1439 Hildebrand, Fred Hitt, Alex Hopmann, James Hunt, Marcus Jager, Chris 1440 Kaler, Manoj Kasichainula, Rohit Khare, Brian Korver, Daniel 1441 LaLiberte, Steve Martin, Larry Masinter, Jeff McAffer, Surendra 1442 Koduru Reddy, Max Rible, Sam Ruby, Bradley Sergeant, Nick Shelness, 1443 John Stracke, John Tigue, John Turner, Kevin Wiggen, and other 1444 members of the WebDAV working group. 1446 14. References 1447 14.1. Normative References 1449 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1450 Requirement Levels", BCP 14, RFC 2119, March 1997. 1452 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1453 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 1454 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1456 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1457 Resource Identifier (URI): Generic Syntax", STD 66, 1458 RFC 3986, January 2005. 1460 [XML] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and 1461 F. Yergeau, "Extensible Markup Language (XML) 1.0 (Third 1462 Edition)", W3C REC-xml-20040204, February 2004, 1463 . 1465 [draft-ietf-webdav-rfc2518bis] 1466 Dusseault, L., Ed., "HTTP Extensions for Distributed 1467 Authoring - WebDAV RFC2518 bis", 1468 draft-ietf-webdav-rfc2518bis-14 (work in progress), 1469 February 2006, . 1472 14.2. Informative References 1474 [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. 1475 Whitehead, "Versioning Extensions to WebDAV (Web 1476 Distributed Authoring and Versioning)", RFC 3253, 1477 March 2002. 1479 [RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web 1480 Distributed Authoring and Versioning (WebDAV) Access 1481 Control Protocol", RFC 3744, May 2004. 1483 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 1484 Unique IDentifier (UUID) URN Namespace", RFC 4122, 1485 July 2005. 1487 Appendix A. Change Log (to be removed by RFC Editor before publication) 1489 A.1. Since draft-ietf-webdav-bind-02 1491 Add and resolve issues "2.3_COPY_SHARED_BINDINGS" and 1492 "2.3_MULTIPLE_COPY". Add issue "5.1_LOOP_STATUS" and proposed 1493 resolution, but keep it open. Add issues "ED_references" and 1494 "4_507_status". Started work on index. Rename document to "Binding 1495 Extensions to Web Distributed Authoring and Versioning (WebDAV)". 1496 Rename "References" to "Normative References". Close issue 1497 "ED_references". Close issue "4_507_status". 1499 A.2. Since draft-ietf-webdav-bind-03 1501 Add and close issues "9.2_redirect_loops", "ED_authors" and 1502 "ED_updates". Add section about capability discovery (DAV header). 1503 Close issues "5.1_LOOP_STATUS". Add and resolve new issue 1504 "5.1_506_STATUS_STREAMING". Update XML spec reference. Add issue 1505 "locking" and resolve as invalid. 1507 A.3. Since draft-ietf-webdav-bind-04 1509 Add and close issues "6_precondition_binding_allowed" and 1510 "6_lock_behaviour". Add mailing list and issues list pointers to 1511 front. 1513 A.4. Since draft-ietf-webdav-bind-05 1515 Editorial fixes. Add and resolve issues "1.3_error_negotiation", 1516 "2.5_language" and "7.1.1_add_resource_id". Add historical issue 1517 "4_LOCK_BEHAVIOR" and it's resolution for better tracking. 1519 A.5. Since draft-ietf-webdav-bind-06 1521 Rewrite Editorial Note. Open and resolve issues "2.6_identical", 1522 "specify_safeness_and_idempotence" and "ED_rfc2026_ref". 1524 A.6. Since draft-ietf-webdav-bind-07 1526 Add more index items (no change tracking). Add and resolve issues 1527 "2.3_copy_to_same", "bind_properties", "bind_vs_ACL", 1528 "6_rebind_intro" and "rfc2396bis" (actually an action item). Fix XML 1529 DTD fragment in section 3.3. Make spelling of "Request-URI" 1530 consistent. 1532 A.7. Since draft-ietf-webdav-bind-08 1534 Resolved editorial issues raised by Jim Whitehead in . 1536 Add and resolve issues "atomicity", "2_allow_destroy", 1537 "2.1_separate_loop_discussion", "2.1.1_bind_loops_vs_locks", 1538 "2.3_copy_depth_infinity", "2.3_copy_example", "2.3_copy_vs_loops", 1539 "2.6_resource-id_vs_versions", "3.2_example" and 1540 "6_rebind_premissions". Add issue "2.6_when_do_ids_change". Re-open 1541 and resolve "6_rebind_intro". 1543 A.8. Since draft-ietf-webdav-bind-09 1545 Add and resolve issue "6.1_rebind_vs_locks", adding proposed example 1546 text. Add action item "3.1_uuids". Close issue 1547 "2.6_when_do_ids_change". Add and resolve issues 1548 "2.6_bindings_vs_properties" and "uri_draft_ref". 1550 A.9. Since draft-ietf-webdav-bind-10 1552 Resolve action item "3.1_uuids". Add and resolve issue 1553 "2.7_unlock_vs_bindings". Revisit issue 1554 "2.6_bindings_vs_properties", and remove the part of the sentence 1555 that speaks about live properties. Update "rfc2396bis" references to 1556 "RFC3986". Add issue "9_ns_op_and_acl" and add potential resolution. 1557 Align artwork where applicable (new xml2rfc1.29rc2 feature). 1559 A.10. Since draft-ietf-webdav-bind-11 1561 Updated [draft-mealling-uuid-urn] to [RFC4122]. Add statement about 1562 live properties in Section 2.6. 1564 A.11. Since draft-ietf-webdav-bind-12 1566 Updated Author's address. Uppercase "Section" when referring to 1567 other documents. 1569 Updating from RFC2518 to RFC2518bis: 1571 o Remove own explanation of DTD syntax. 1573 o Remove own definition of precondition/postcondition. 1575 o Remove reference to broken RFC2518 language about DELETE and 1576 UNLOCK. 1578 o Remove own definition of DAV: request header. 1580 o Updated "Rationale for Distinguishing Bindings from URI Mappings" 1581 to reflect the changes in [draft-ietf-webdav-rfc2518bis], making 1582 proposals for more changes so that the issue can be closed (see 1583 also 1584 and ). 1587 A.12. Since draft-ietf-webdav-bind-13 1589 Update [draft-ietf-webdav-rfc2518-bis] to draft 14. Update one 1590 incorrect section reference. Remove Section "Rationale for 1591 Distinguishing Bindings from URI Mappings" as 1592 [draft-ietf-webdav-rfc2518-bis] now uses the proper definition of 1593 collection state. Examples use application/xml instead of text/xml 1594 MIME type. 1596 Fix IANA section (there are no IANA considerations). 1598 Appendix B. Resolved issues (to be removed by RFC Editor before 1599 publication) 1601 Issues that were either rejected or resolved in this version of this 1602 document. 1604 B.1. webdav-rev 1606 Type: edit 1608 julian.reschke@greenbytes.de (2006-01-30): Update from RFC2518 to 1609 RFC2518bis. 1611 Resolution (2006-02-21): Removed own explanation of DTD syntax, 1612 removed own definition of precondition/postcondition, removed 1613 reference to broken RFC2518 language about DELETE and UNLOCK, removed 1614 own definition of DAV: request header, updated examples to use 1615 application/xml instead of text/xml MIME type, removed "Rationale for 1616 Distinguishing Bindings from URI Mappings" to reflect the changes in 1617 draft-ietf-webdav-rfc2518bis-14. 1619 Appendix C. Open issues (to be removed by RFC Editor prior to 1620 publication) 1622 C.1. edit 1624 Type: edit 1626 julian.reschke@greenbytes.de (2004-05-30): Umbrella issue for 1627 editorial fixes/enhancements. 1629 Index 1631 2 1632 208 Already Reported (status code) 28 1634 5 1635 506 Loop Detected (status code) 31 1637 B 1638 BIND method 18 1639 Binding 6 1641 C 1642 Collection 6 1643 Condition Names 1644 DAV:bind-into-collection (pre) 19 1645 DAV:bind-source-exists (pre) 19 1646 DAV:binding-allowed (pre) 20 1647 DAV:binding-deleted (post) 22, 25 1648 DAV:can-overwrite (pre) 20, 24 1649 DAV:cross-server-binding (pre) 20, 24 1650 DAV:cycle-allowed (pre) 20, 24 1651 DAV:lock-deleted (post) 22, 25 1652 DAV:locked-overwrite-allowed (pre) 20 1653 DAV:locked-source-collection-update-allowed (pre) 24 1654 DAV:locked-update-allowed (pre) 20, 22, 24 1655 DAV:name-allowed (pre) 20, 24 1656 DAV:new-binding (post) 20, 25 1657 DAV:protected-source-url-deletion-allowed (pre) 25 1658 DAV:protected-url-deletion-allowed (pre) 22 1659 DAV:protected-url-modification-allowed (pre) 24 1660 DAV:rebind-from-collection (pre) 24 1661 DAV:rebind-source-exists (pre) 24 1662 DAV:unbind-from-collection (pre) 22 1663 DAV:unbind-source-exists (pre) 22 1665 D 1666 DAV header 1667 compliance class 'bind' 31 1668 DAV:bind-into-collection precondition 19 1669 DAV:bind-source-exists precondition 19 1670 DAV:binding-allowed precondition 20 1671 DAV:binding-deleted postcondition 22, 25 1672 DAV:can-overwrite precondition 20, 24 1673 DAV:cross-server-binding precondition 20, 24 1674 DAV:cycle-allowed precondition 20, 24 1675 DAV:lock-deleted postcondition 22, 25 1676 DAV:locked-overwrite-allowed precondition 20 1677 DAV:locked-source-collection-update-allowed precondition 24 1678 DAV:locked-update-allowed precondition 20, 22, 24 1679 DAV:name-allowed precondition 20, 24 1680 DAV:new-binding postcondition 20, 25 1681 DAV:parent-set property 17 1682 DAV:protected-source-url-deletion-allowed precondition 25 1683 DAV:protected-url-deletion-allowed precondition 22 1684 DAV:protected-url-modification-allowed precondition 24 1685 DAV:rebind-from-collection precondition 24 1686 DAV:rebind-source-exists precondition 24 1687 DAV:resource-id property 17 1688 DAV:unbind-from-collection precondition 22 1689 DAV:unbind-source-exists precondition 22 1691 I 1692 Internal Member URI 6 1694 M 1695 Methods 1696 BIND 18 1697 REBIND 23 1698 UNBIND 21 1700 P 1701 Path Segment 6 1702 Properties 1703 DAV:parent-set 17 1704 DAV:resource-id 17 1706 R 1707 REBIND method 23 1709 S 1710 Status Codes 1711 208 Already Reported 28 1712 506 Loop Detected 31 1714 U 1715 UNBIND method 21 1716 URI Mapping 5 1718 Authors' Addresses 1720 Geoffrey Clemm 1721 IBM 1722 20 Maguire Road 1723 Lexington, MA 02421 1725 Email: geoffrey.clemm@us.ibm.com 1727 Jason Crawford 1728 IBM Research 1729 P.O. Box 704 1730 Yorktown Heights, NY 10598 1732 Email: ccjason@us.ibm.com 1734 Julian F. Reschke 1735 greenbytes GmbH 1736 Hafenweg 16 1737 Muenster, NW 48155 1738 Germany 1740 Email: julian.reschke@greenbytes.de 1742 Jim Whitehead 1743 UC Santa Cruz, Dept. of Computer Science 1744 1156 High Street 1745 Santa Cruz, CA 95064 1747 Email: ejw@cse.ucsc.edu 1749 Intellectual Property Statement 1751 The IETF takes no position regarding the validity or scope of any 1752 Intellectual Property Rights or other rights that might be claimed to 1753 pertain to the implementation or use of the technology described in 1754 this document or the extent to which any license under such rights 1755 might or might not be available; nor does it represent that it has 1756 made any independent effort to identify any such rights. 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