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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: 3 errors (**), 1 flaw (~~), 5 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 IBM Research 6 (if approved) J. Reschke, Ed. 7 Intended status: Standards Track greenbytes 8 Expires: September 14, 2007 J. Whitehead 9 U.C. Santa Cruz 10 March 13, 2007 12 Binding Extensions to Web Distributed Authoring and Versioning (WebDAV) 13 draft-ietf-webdav-bind-18 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 September 14, 2007. 40 Copyright Notice 42 Copyright (C) The IETF Trust (2007). 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. Clarification to RFC2518bis' Usage of the term 118 'lock root' . . . . . . . . . . . . . . . . . . . . . 34 119 Appendix B. Change Log (to be removed by RFC Editor before 120 publication) . . . . . . . . . . . . . . . . . . . . 35 121 B.1. Since draft-ietf-webdav-bind-02 . . . . . . . . . . . . . 35 122 B.2. Since draft-ietf-webdav-bind-03 . . . . . . . . . . . . . 35 123 B.3. Since draft-ietf-webdav-bind-04 . . . . . . . . . . . . . 35 124 B.4. Since draft-ietf-webdav-bind-05 . . . . . . . . . . . . . 36 125 B.5. Since draft-ietf-webdav-bind-06 . . . . . . . . . . . . . 36 126 B.6. Since draft-ietf-webdav-bind-07 . . . . . . . . . . . . . 36 127 B.7. Since draft-ietf-webdav-bind-08 . . . . . . . . . . . . . 36 128 B.8. Since draft-ietf-webdav-bind-09 . . . . . . . . . . . . . 36 129 B.9. Since draft-ietf-webdav-bind-10 . . . . . . . . . . . . . 36 130 B.10. Since draft-ietf-webdav-bind-11 . . . . . . . . . . . . . 37 131 B.11. Since draft-ietf-webdav-bind-12 . . . . . . . . . . . . . 37 132 B.12. Since draft-ietf-webdav-bind-13 . . . . . . . . . . . . . 37 133 B.13. Since draft-ietf-webdav-bind-14 . . . . . . . . . . . . . 37 134 B.14. Since draft-ietf-webdav-bind-15 . . . . . . . . . . . . . 38 135 B.15. Since draft-ietf-webdav-bind-16 . . . . . . . . . . . . . 38 136 B.16. Since draft-ietf-webdav-bind-17 . . . . . . . . . . . . . 38 137 Appendix C. Open issues (to be removed by RFC Editor prior to 138 publication) . . . . . . . . . . . . . . . . . . . . 38 139 C.1. edit . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 140 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 141 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 40 142 Intellectual Property and Copyright Statements . . . . . . . . . . 42 144 1. Introduction 146 This specification extends the WebDAV Distributed Authoring Protocol 147 ([draft-ietf-webdav-rfc2518bis]) to enable clients to create new 148 access paths to existing resources. This capability is useful for 149 several reasons: 151 URIs of WebDAV-compliant resources are hierarchical and correspond to 152 a hierarchy of collections in resource space. The WebDAV Distributed 153 Authoring Protocol makes it possible to organize these resources into 154 hierarchies, placing them into groupings, known as collections, which 155 are more easily browsed and manipulated than a single flat 156 collection. However, hierarchies require categorization decisions 157 that locate resources at a single location in the hierarchy, a 158 drawback when a resource has multiple valid categories. For example, 159 in a hierarchy of vehicle descriptions containing collections for 160 cars and boats, a description of a combination car/boat vehicle could 161 belong in either collection. Ideally, the description should be 162 accessible from both. Allowing clients to create new URIs that 163 access the existing resource lets them put that resource into 164 multiple collections. 166 Hierarchies also make resource sharing more difficult, since 167 resources that have utility across many collections are still forced 168 into a single collection. For example, the mathematics department at 169 one university might create a collection of information on fractals 170 that contains bindings to some local resources, but also provides 171 access to some resources at other universities. For many reasons, it 172 may be undesirable to make physical copies of the shared resources on 173 the local server: to conserve disk space, to respect copyright 174 constraints, or to make any changes in the shared resources visible 175 automatically. Being able to create new access paths to existing 176 resources in other collections or even on other servers is useful for 177 this sort of case. 179 The BIND method defined here provides a mechanism for allowing 180 clients to create alternative access paths to existing WebDAV 181 resources. HTTP [RFC2616] and WebDAV [draft-ietf-webdav-rfc2518bis] 182 methods are able to work because there are mappings between URIs and 183 resources. A method is addressed to a URI, and the server follows 184 the mapping from that URI to a resource, applying the method to that 185 resource. Multiple URIs may be mapped to the same resource, but 186 until now there has been no way for clients to create additional URIs 187 mapped to existing resources. 189 BIND lets clients associate a new URI with an existing WebDAV 190 resource, and this URI can then be used to submit requests to the 191 resource. Since URIs of WebDAV resources are hierarchical, and 192 correspond to a hierarchy of collections in resource space, the BIND 193 method also has the effect of adding the resource to a collection. 194 As new URIs are associated with the resource, it appears in 195 additional collections. 197 A BIND request does not create a new resource, but simply makes 198 available a new URI for submitting requests to an existing resource. 199 The new URI is indistinguishable from any other URI when submitting a 200 request to a resource. Only one round trip is needed to submit a 201 request to the intended target. Servers are required to enforce the 202 integrity of the relationships between the new URIs and the resources 203 associated with them. Consequently, it may be very costly for 204 servers to support BIND requests that cross server boundaries. 206 This specification is organized as follows. Section 1.1 defines 207 terminology used in the rest of the specification, while Section 2 208 overviews bindings. Section 3 defines the new properties needed to 209 support multiple bindings to the same resource. Section 4 specifies 210 the BIND method, used to create multiple bindings to the same 211 resource. Section 5 specifies the UNBIND method, used to remove a 212 binding to a resource. Section 6 specifies the REBIND method, used 213 to move a binding to another collection. 215 1.1. Terminology 217 The terminology used here follows and extends that in the WebDAV 218 Distributed Authoring Protocol specification 219 [draft-ietf-webdav-rfc2518bis]. 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 227 [draft-ietf-webdav-rfc2518bis]. 229 URI Mapping 231 A relation between an absolute URI and a resource. For an 232 absolute URI U and the resource it identifies R, the URI mapping 233 can be thought of as (U => R). Since a resource can represent 234 items that are not network retrievable, as well as those that are, 235 it is possible for a resource to have zero, one, or many URI 236 mappings. Mapping a resource to an "http" scheme URI makes it 237 possible to submit HTTP protocol requests to the resource using 238 the URI. 240 Path Segment 242 Informally, the characters found between slashes ("/") in a URI. 243 Formally, as defined in Section 3.3 of [RFC3986]. 245 Binding 247 A relation between a single path segment (in a collection) and a 248 resource. A binding is part of the state of a collection. If two 249 different collections contain a binding between the same path 250 segment and the same resource, these are two distinct bindings. 251 So for a collection C, a path segment S, and a resource R, the 252 binding can be thought of as C:(S -> R). Bindings create URI 253 mappings, and hence allow requests to be sent to a single resource 254 from multiple locations in a URI namespace. For example, given a 255 collection C (accessible through the URI 256 http://www.example.com/CollX), a path segment S (equal to 257 "foo.html"), and a resource R, then creating the binding C: (S -> 258 R) makes it possible to use the URI 259 http://www.example.com/CollX/foo.html to access R. 261 Collection 263 A resource that contains, as part of its state, a set of bindings 264 that identify internal member resources. 266 Internal Member URI 268 The URI that identifies an internal member of a collection, and 269 that consists of the URI for the collection, followed by a slash 270 character ('/'), followed by the path segment of the binding for 271 that internal member. 273 1.2. Method Preconditions and Postconditions 275 See Section 16 of [draft-ietf-webdav-rfc2518bis] for the definitions 276 of "precondition" and "postcondition". 278 2. Overview of Bindings 280 Bindings are part of the state of a collection. They define the 281 internal members of the collection, and the names of those internal 282 members. 284 Bindings are added and removed by a variety of existing HTTP methods. 285 A method that creates a new resource, such as PUT, COPY, and MKCOL, 286 adds a binding. A method that deletes a resource, such as DELETE, 287 removes a binding. A method that moves a resource (e.g. MOVE) both 288 adds a binding (in the destination collection) and removes a binding 289 (in the source collection). The BIND method introduced here provides 290 a mechanism for adding a second binding to an existing resource. 291 There is no difference between an initial binding added by PUT, COPY, 292 or MKCOL, and additional bindings added with BIND. 294 It would be very undesirable if one binding could be destroyed as a 295 side effect of operating on the resource through a different binding. 296 In particular, the removal of one binding to a resource (e.g. with a 297 DELETE or a MOVE) MUST NOT disrupt another binding to that resource, 298 e.g. by turning that binding into a dangling path segment. The 299 server MUST NOT reclaim system resources after removing one binding, 300 while other bindings to the resource remain. In other words, the 301 server MUST maintain the integrity of a binding. It is permissible, 302 however, for future method definitions (e.g., a DESTROY method) to 303 have semantics that explicitly remove all bindings and/or immediately 304 reclaim system resources. 306 2.1. Bindings to Collections 308 Creating a new binding to a collection makes each resource associated 309 with a binding in that collection accessible via a new URI, and thus 310 creates new URI mappings to those resources but no new bindings. 312 For example, suppose a new binding CollY is created for collection C1 313 in the figure below. It immediately becomes possible to access 314 resource R1 using the URI /CollY/x.gif and to access resource R2 315 using the URI /CollY/y.jpg, but no new bindings for these child 316 resources were created. This is because bindings are part of the 317 state of a collection, and associate a URI that is relative to that 318 collection with its target resource. No change to the bindings in 319 Collection C1 is needed to make its children accessible using /CollY/ 320 x.gif and /CollY/y.jpg. 322 +-------------------------+ 323 | Root Collection | 324 | bindings: | 325 | CollX CollY | 326 +-------------------------+ 327 | / 328 | / 329 | / 330 +------------------+ 331 | Collection C1 | 332 | bindings: | 333 | x.gif y.jpg | 334 +------------------+ 335 | \ 336 | \ 337 | \ 338 +-------------+ +-------------+ 339 | Resource R1 | | Resource R2 | 340 +-------------+ +-------------+ 342 2.1.1. Bind loops 344 Bindings to collections can result in loops, which servers MUST 345 detect when processing "Depth: infinity" requests. It is sometimes 346 possible to complete an operation in spite of the presence of a loop. 347 For instance, a PROPFIND can still succeed if the server uses the new 348 status code 208 (Already Reported) defined in Section 7.1. 350 However, the 506 (Loop Detected) status code is defined in 351 Section 7.2 for use in contexts where an operation is terminated 352 because a loop was encountered. 354 2.2. URI Mappings Created by a new Binding 356 Suppose a binding from "Binding-Name" to resource R is to be added to 357 a collection, C. Then if C-MAP is the set of URIs that were mapped to 358 C before the BIND request, then for each URI "C-URI" in C-MAP, the 359 URI "C-URI/Binding-Name" is mapped to resource R following the BIND 360 request. 362 For example, if a binding from "foo.html" to R is added to a 363 collection C, and if the following URIs are mapped to C: 365 http://www.example.com/A/1/ 366 http://example.com/A/one/ 367 then the following new mappings to R are introduced: 369 http://www.example.com/A/1/foo.html 370 http://example.com/A/one/foo.html 372 Note that if R is a collection, additional URI mappings are created 373 to the descendents of R. Also, note that if a binding is made in 374 collection C to C itself (or to a parent of C), an infinite number of 375 mappings are introduced. 377 For example, if a binding from "myself" to C is then added to C, the 378 following infinite number of additional mappings to C are introduced: 380 http://www.example.com/A/1/myself 381 http://www.example.com/A/1/myself/myself 382 ... 384 and the following infinite number of additional mappings to R are 385 introduced: 387 http://www.example.com/A/1/myself/foo.html 388 http://www.example.com/A/1/myself/myself/foo.html 389 ... 391 2.3. COPY and Bindings 393 As defined in Section 9.8 of [draft-ietf-webdav-rfc2518bis], COPY 394 causes the resource identified by the Request-URI to be duplicated, 395 and makes the new resource accessible using the URI specified in the 396 Destination header. Upon successful completion of a COPY, a new 397 binding is created between the last path segment of the Destination 398 header, and the destination resource. The new binding is added to 399 its parent collection, identified by the Destination header minus its 400 final segment. 402 The following figure shows an example: Suppose that a COPY is issued 403 to URI-3 for resource R (which is also mapped to URI-1 and URI-2), 404 with the Destination header set to URI-X. After successful 405 completion of the COPY operation, resource R is duplicated to create 406 resource R', and a new binding has been created which creates at 407 least the URI mapping between URI-X and the new resource (although 408 other URI mappings may also have been created). 410 URI-1 URI-2 URI-3 URI-X 411 | | | | 412 | | | <---- URI Mappings ----> | 413 | | | | 414 +---------------------+ +------------------------+ 415 | Resource R | | Resource R' | 416 +---------------------+ +------------------------+ 418 It might be thought that a COPY request with "Depth: 0" on a 419 collection would duplicate its bindings, since bindings are part of 420 the collection's state. This is not the case, however. The 421 definition of Depth in [draft-ietf-webdav-rfc2518bis] makes it clear 422 that a "Depth: 0" request does not apply to a collection's members. 423 Consequently, a COPY with "Depth: 0" does not duplicate the bindings 424 contained by the collection. 426 If a COPY request causes an existing resource to be updated, the 427 bindings to that resource MUST be unaffected by the COPY request. 428 Using the preceding example, suppose that a COPY request is issued to 429 URI-X for resource R', with the Destination header set to URI-2. The 430 content and dead properties of resource R would be updated to be a 431 copy of those of resource R', but the mappings from URI-1, URI-2, and 432 URI-3 to resource R remain unaffected. If because of multiple 433 bindings to a resource, more than one source resource updates a 434 single destination resource, the order of the updates is server 435 defined. 437 If a COPY request would cause a new resource to be created as a copy 438 of an existing resource, and that COPY request has already created a 439 copy of that existing resource, the COPY request instead creates 440 another binding to the previous copy, instead of creating a new 441 resource. 443 2.3.1. Example: COPY with 'Depth: infinity' in presence of bind loops 445 As an example of how COPY with Depth infinity would work in the 446 presence of bindings, consider the following collection: 448 +------------------+ 449 | Root Collection | 450 | bindings: | 451 | CollX | 452 +------------------+ 453 | 454 | 455 +-------------------------------+ 456 | Collection C1 |<-------+ 457 | bindings: | | 458 | x.gif CollY | | 459 +-------------------------------+ | 460 | \ (creates loop) | 461 | \ | 462 +-------------+ +------------------+ | 463 | Resource R1 | | Collection C2 | | 464 +-------------+ | bindings: | | 465 | y.gif CollZ | | 466 +------------------+ | 467 | | | 468 | +--------+ 469 | 470 +-------------+ 471 | Resource R2 | 472 +-------------+ 474 If a COPY with Depth infinity is submitted to /CollX, with 475 destination of /CollA, the outcome of the copy operation is: 477 +------------------+ 478 | Root Collection | 479 | bindings: | 480 | CollX CollA | 481 +------------------+ 482 | | 483 | +---------------------------+ 484 | | 485 +-------------------+ | 486 | Collection C1 |<------------------+ | 487 | bindings: | | | 488 | x.gif CollY | | | 489 +-------------------+ | | 490 | \ (creates loop) | | 491 | \ | | 492 +-------------+ +-----------------+ | | 493 | Resource R1 | | Collection C2 | | | 494 +-------------+ | bindings: | | | 495 | y.gif CollZ | | | 496 +-----------------+ | | 497 | | | | 498 | +-------+ | 499 | | 500 +-------------+ | 501 | Resource R2 | | 502 +-------------+ | 503 | 504 +-------------------------------+ 505 | 506 +-------------------+ 507 | Collection C3 |<------------------+ 508 | bindings: | | 509 | x.gif CollY | | 510 +-------------------+ | 511 | \ (creates loop) | 512 | \ | 513 +-------------+ +-----------------+ | 514 | Resource R3 | | Collection C4 | | 515 +-------------+ | bindings: | | 516 | y.gif CollZ | | 517 +-----------------+ | 518 | | | 519 | +-------+ 520 | 521 +-------------+ 522 | Resource R4 | 523 +-------------+ 525 2.3.2. Example: COPY with 'Depth: infinity' with multiple bindings to a 526 leaf resource 528 Given the following collection hierarchy: 530 +------------------+ 531 | Root Collection | 532 | bindings: | 533 | CollX | 534 +------------------+ 535 | 536 | 537 | 538 +----------------+ 539 | Collection C1 | 540 | bindings: | 541 | x.gif y.gif | 542 +----------------+ 543 | | 544 | | 545 +-------------+ 546 | Resource R1 | 547 +-------------+ 549 A COPY of /CollX with Depth infinity to /CollY results in the 550 following collection hierarchy: 552 +------------------+ 553 | Root Collection | 554 | bindings: | 555 | CollX CollY | 556 +------------------+ 557 | \ 558 | \ 559 | \ 560 +----------------+ +-----------------+ 561 | Collection C1 | | Collection C2 | 562 | bindings: | | bindings: | 563 | x.gif y.gif | | x.gif y.gif | 564 +----------------+ +-----------------+ 565 | | | | 566 | | | | 567 +-------------+ +-------------+ 568 | Resource R1 | | Resource R2 | 569 +-------------+ +-------------+ 571 2.4. DELETE and Bindings 573 When there are multiple bindings to a resource, a DELETE applied to 574 that resource MUST NOT remove any bindings to that resource other 575 than the one identified by the Request-URI. For example, suppose the 576 collection identified by the URI "/a" has a binding named "x" to a 577 resource R, and another collection identified by "/b" has a binding 578 named "y" to the same resource R. Then a DELETE applied to "/a/x" 579 removes the binding named "x" from "/a" but MUST NOT remove the 580 binding named "y" from "/b" (i.e. after the DELETE, "/y/b" continues 581 to identify the resource R). 583 When DELETE is applied to a collection, it MUST NOT modify the 584 membership of any other collection that is not itself a member of the 585 collection being deleted. For example, if both "/a/.../x" and 586 "/b/.../y" identify the same collection, C, then applying DELETE to 587 "/a" must not delete an internal member from C or from any other 588 collection that is a member of C, because that would modify the 589 membership of "/b". 591 If a collection supports the UNBIND method (see Section 5), a DELETE 592 of an internal member of a collection MAY be implemented as an UNBIND 593 request. In this case, applying DELETE to a Request-URI has the 594 effect of removing the binding identified by the final segment of the 595 Request-URI from the collection identified by the Request-URI minus 596 its final segment. Although [draft-ietf-webdav-rfc2518bis] allows a 597 DELETE to be a non-atomic operation, when the DELETE operation is 598 implemented as an UNBIND, the operation is atomic. In particular, a 599 DELETE on a hierarchy of resources is simply the removal of a binding 600 to the collection identified by the Request-URI. 602 2.5. MOVE and Bindings 604 When MOVE is applied to a resource, the other bindings to that 605 resource MUST be unaffected, and if the resource being moved is a 606 collection, the bindings to any members of that collection MUST be 607 unaffected. Also, if MOVE is used with Overwrite:T to delete an 608 existing resource, the constraints specified for DELETE apply. 610 If the destination collection of a MOVE request supports the REBIND 611 method (see Section 6), a MOVE of a resource into that collection MAY 612 be implemented as a REBIND request. Although 613 [draft-ietf-webdav-rfc2518bis] allows a MOVE to be a non-atomic 614 operation, when the MOVE operation is implemented as a REBIND, the 615 operation is atomic. In particular, applying a MOVE to a Request-URI 616 and a Destination URI has the effect of removing a binding to a 617 resource (at the Request-URI), and creating a new binding to that 618 resource (at the Destination URI). Even when the Request-URI 619 identifies a collection, the MOVE operation involves only removing 620 one binding to that collection and adding another. 622 As an example, suppose that a MOVE is issued to URI-3 for resource R 623 below (which is also mapped to URI-1 and URI-2), with the Destination 624 header set to URI-X. After successful completion of the MOVE 625 operation, a new binding has been created which creates the URI 626 mapping between URI-X and resource R. The binding corresponding to 627 the final segment of URI-3 has been removed, which also causes the 628 URI mapping between URI-3 and R to be removed. If resource R were a 629 collection, old URI-3 based mappings to members of R would have been 630 removed, and new URI-X based mappings to members of R would have been 631 created. 633 >> Before Request: 635 URI-1 URI-2 URI-3 636 | | | 637 | | | <---- URI Mappings 638 | | | 639 +---------------------+ 640 | Resource R | 641 +---------------------+ 643 >> After Request: 645 URI-1 URI-2 URI-X 646 | | | 647 | | | <---- URI Mappings 648 | | | 649 +---------------------+ 650 | Resource R | 651 +---------------------+ 653 2.6. PROPFIND and Bindings 655 Consistent with [draft-ietf-webdav-rfc2518bis], the value of a dead 656 property MUST be independent of the number of bindings to its host 657 resource or of the path submitted to PROPFIND. On the other hand, 658 the behaviour for each live property depends on its individual 659 definition (for example, see [RFC3744], Section 5, paragraph 2). 661 2.7. Determining Whether Two Bindings Are to the Same Resource 663 It is useful to have some way of determining whether two bindings are 664 to the same resource. Two resources might have identical contents 665 and properties, but not be the same resource (e.g. an update to one 666 resource does not affect the other resource). 668 The REQUIRED DAV:resource-id property defined in Section 3.1 is a 669 resource identifier, which MUST be unique across all resources for 670 all time. If the values of DAV:resource-id returned by PROPFIND 671 requests through two bindings are identical character by character, 672 the client can be assured that the two bindings are to the same 673 resource. 675 The DAV:resource-id property is created, and its value assigned, when 676 the resource is created. The value of DAV:resource-id MUST NOT be 677 changed. Even after the resource is no longer accessible through any 678 URI, that value MUST NOT be reassigned to another resource's DAV: 679 resource-id property. 681 Any method that creates a new resource MUST assign a new, unique 682 value to its DAV:resource-id property. For example, a PUT applied to 683 a null resource, COPY (when not overwriting an existing target) and 684 CHECKIN (see [RFC3253], Section 4.4) must assign a new, unique value 685 to the DAV:resource-id property of the new resource they create. 687 On the other hand, any method that affects an existing resource must 688 not change the value of its DAV:resource-id property. Specifically, 689 a PUT or a COPY that updates an existing resource must not change the 690 value of its DAV:resource-id property. A REBIND, since it does not 691 create a new resource, but only changes the location of an existing 692 resource, must not change the value of the DAV:resource-id property. 694 2.8. Discovering the Bindings to a Resource 696 An OPTIONAL DAV:parent-set property on a resource provides a list of 697 the bindings that associate a collection and a URI segment with that 698 resource. If the DAV:parent-set property exists on a given resource, 699 it MUST contain a complete list of all bindings to that resource that 700 the client is authorized to see. When deciding whether to support 701 the DAV:parent-set property, server implementers / administrators 702 should balance the benefits it provides against the cost of 703 maintaining the property and the security risks enumerated in 704 Sections 10.4 and 10.5. 706 3. Properties 708 The bind feature introduces the properties defined below. 710 A DAV:allprop PROPFIND request SHOULD NOT return any of the 711 properties defined by this document. This allows a binding server to 712 perform efficiently when a naive client, which does not understand 713 the cost of asking a server to compute all possible live properties, 714 issues a DAV:allprop PROPFIND request. 716 3.1. DAV:resource-id Property 718 The DAV:resource-id property is a REQUIRED property that enables 719 clients to determine whether two bindings are to the same resource. 720 The value of DAV:resource-id is a URI, and may use any registered URI 721 scheme that guarantees the uniqueness of the value across all 722 resources for all time (e.g. the urn:uuid: URN namespace defined in 723 [RFC4122] or the opaquelocktoken: URI scheme defined in 724 [draft-ietf-webdav-rfc2518bis]). 726 728 3.2. DAV:parent-set Property 730 The DAV:parent-set property is an OPTIONAL property that enables 731 clients to discover what collections contain a binding to this 732 resource (i.e. what collections have that resource as an internal 733 member). It contains an of href/segment pair for each collection 734 that has a binding to the resource. The href identifies the 735 collection, and the segment identifies the binding name of that 736 resource in that collection. 738 A given collection MUST appear only once in the DAV:parent-set for 739 any given binding, even if there are multiple URI mappings to that 740 collection. 742 743 744 745 748 3.2.1. Example for DAV:parent-set property 750 For example, if collection C1 is mapped to both /CollX and /CollY, 751 and C1 contains a binding named "x.gif" to a resource R1, then either 752 [/CollX, x.gif] or [/CollY, x.gif] can appear in the DAV:parent-set 753 of R1, but not both. But if C1 also had a binding named "y.gif" to 754 R1, then there would be two entries for C1 in the DAV:binding-set of 755 R1 (i.e. both [/CollX, x.gif] and [/CollX, y.gif] or, alternatively, 756 both [/CollY, x.gif] and [/CollY, y.gif]). 758 +-------------------------+ 759 | Root Collection | 760 | bindings: | 761 | CollX CollY | 762 +-------------------------+ 763 | / 764 | / 765 | / 766 +-----------------+ 767 | Collection C1 | 768 | bindings: | 769 | x.gif y.gif | 770 +-----------------+ 771 | | 772 | | 773 | | 774 +--------------+ 775 | Resource R1 | 776 +--------------+ 778 In this case, one possible value for DAV:parent-set property on 779 "/CollX/x.gif" would be: 781 782 783 /CollX 784 x.gif 785 786 787 /CollX 788 y.gif 789 790 792 4. BIND Method 794 The BIND method modifies the collection identified by the Request- 795 URI, by adding a new binding from the segment specified in the BIND 796 body to the resource identified in the BIND body. 798 If a server cannot guarantee the integrity of the binding, the BIND 799 request MUST fail. Note that it is especially difficult to maintain 800 the integrity of cross-server bindings. Unless the server where the 801 resource resides knows about all bindings on all servers to that 802 resource, it may unwittingly destroy the resource or make it 803 inaccessible without notifying another server that manages a binding 804 to the resource. For example, if server A permits creation of a 805 binding to a resource on server B, server A must notify server B 806 about its binding and must have an agreement with B that B will not 807 destroy the resource while A's binding exists. Otherwise server B 808 may receive a DELETE request that it thinks removes the last binding 809 to the resource and destroy the resource while A's binding still 810 exists. The precondition DAV:cross-server-binding is defined below 811 for cases where servers fail cross-server BIND requests because they 812 cannot guarantee the integrity of cross-server bindings. 814 By default, if there already is a binding for the specified segment 815 in the collection, the new binding replaces the existing binding. 816 This default binding replacement behavior can be overridden using the 817 Overwrite header defined in Section 10.6 of 818 [draft-ietf-webdav-rfc2518bis]. 820 If a BIND request fails, the server state preceding the request MUST 821 be restored. This method is unsafe and idempotent (see [RFC2616], 822 Section 9.1). 824 Marshalling: 826 The request MAY include an Overwrite header. 828 The request body MUST be a DAV:bind XML element. 830 832 If the request succeeds, the server MUST return 201 (Created) when 833 a new binding was created and 200 (OK) when an existing binding 834 was replaced. 836 If a response body for a successful request is included, it MUST 837 be a DAV:bind-response XML element. Note that this document does 838 not define any elements for the BIND response body, but the DAV: 839 bind-response element is defined to ensure interoperability 840 between future extensions that do define elements for the BIND 841 response body. 843 845 Preconditions: 847 (DAV:bind-into-collection): The Request-URI MUST identify a 848 collection. 850 (DAV:bind-source-exists): The DAV:href element MUST identify a 851 resource. 853 (DAV:binding-allowed): The resource identified by the DAV:href 854 supports multiple bindings to it. 856 (DAV:cross-server-binding): If the resource identified by the DAV: 857 href element in the request body is on another server from the 858 collection identified by the Request-URI, the server MUST support 859 cross-server bindings. 861 (DAV:name-allowed): The name specified by the DAV:segment is 862 available for use as a new binding name. 864 (DAV:can-overwrite): If the collection already contains a binding 865 with the specified path segment, and if an Overwrite header is 866 included, the value of the Overwrite header MUST be "T". 868 (DAV:cycle-allowed): If the DAV:href element identifies a 869 collection, and if the Request-URI identifies a collection that is 870 a member of that collection, the server MUST support cycles in the 871 URI namespace. 873 (DAV:locked-update-allowed): If the collection identified by the 874 Request-URI is write-locked, then the appropriate token MUST be 875 specified in an If request header. 877 (DAV:locked-overwrite-allowed): If the collection already contains 878 a binding with the specified path segment, and if that binding is 879 protected by a write-lock, then the appropriate token MUST be 880 specified in an If request header. 882 Postconditions: 884 (DAV:new-binding): The collection MUST have a binding that maps 885 the segment specified in the DAV:segment element in the request 886 body, to the resource identified by the DAV:href element in the 887 request body. 889 4.1. Example: BIND 891 >> Request: 893 BIND /CollY HTTP/1.1 894 Host: www.example.com 895 Content-Type: application/xml; charset="utf-8" 896 Content-Length: xxx 898 899 900 bar.html 901 http://www.example.com/CollX/foo.html 902 904 >> Response: 906 HTTP/1.1 201 Created 908 The server added a new binding to the collection, 909 "http://www.example.com/CollY", associating "bar.html" with the 910 resource identified by the URI 911 "http://www.example.com/CollX/foo.html". Clients can now use the URI 912 "http://www.example.com/CollY/bar.html" to submit requests to that 913 resource. 915 5. UNBIND Method 917 The UNBIND method modifies the collection identified by the Request- 918 URI, by removing the binding identified by the segment specified in 919 the UNBIND body. 921 Once a resource is unreachable by any URI mapping, the server MAY 922 reclaim system resources associated with that resource. If UNBIND 923 removes a binding to a resource, but there remain URI mappings to 924 that resource, the server MUST NOT reclaim system resources 925 associated with the resource. 927 If an UNBIND request fails, the server state preceding the request 928 MUST be restored. This method is unsafe and idempotent (see 929 [RFC2616], Section 9.1). 931 Marshalling: 933 The request body MUST be a DAV:unbind XML element. 935 936 If the request succeeds, the server MUST return 200 (OK) when the 937 binding was successfully deleted. 939 If a response body for a successful request is included, it MUST 940 be a DAV:unbind-response XML element. Note that this document 941 does not define any elements for the UNBIND response body, but the 942 DAV:unbind-response element is defined to ensure interoperability 943 between future extensions that do define elements for the UNBIND 944 response body. 946 948 Preconditions: 950 (DAV:unbind-from-collection): The Request-URI MUST identify a 951 collection. 953 (DAV:unbind-source-exists): The DAV:segment element MUST identify 954 a binding in the collection identified by the Request-URI. 956 (DAV:locked-update-allowed): If the collection identified by the 957 Request-URI is write-locked, then the appropriate token MUST be 958 specified in the request. 960 (DAV:protected-url-deletion-allowed): If the binding identified by 961 the segment is protected by a write-lock, then the appropriate 962 token MUST be specified in the request. 964 Postconditions: 966 (DAV:binding-deleted): The collection MUST NOT have a binding for 967 the segment specified in the DAV:segment element in the request 968 body. 970 (DAV:lock-deleted): If the internal member URI of the binding 971 specified by the Request-URI and the DAV:segment element in the 972 request body was protected by a write-lock at the time of the 973 request, that write-lock must have been deleted by the request. 975 5.1. Example: UNBIND 977 >> Request: 979 UNBIND /CollX HTTP/1.1 980 Host: www.example.com 981 Content-Type: application/xml; charset="utf-8" 982 Content-Length: xxx 984 985 986 foo.html 987 989 >> Response: 991 HTTP/1.1 200 OK 993 The server removed the binding named "foo.html" from the collection, 994 "http://www.example.com/CollX". A request to the resource named 995 "http://www.example.com/CollX/foo.html" will return a 404 (Not Found) 996 response. 998 6. REBIND Method 1000 The REBIND method removes a binding to a resource from a collection, 1001 and adds a binding to that resource into the collection identified by 1002 the Request-URI. The request body specifies the binding to be added 1003 (segment) and the old binding to be removed (href). It is 1004 effectively an atomic form of a MOVE request, and MUST be treated the 1005 same way as MOVE for the purpose of determining access permissions. 1007 If a REBIND request fails, the server state preceding the request 1008 MUST be restored. This method is unsafe and idempotent (see 1009 [RFC2616], Section 9.1). 1011 Marshalling: 1013 The request MAY include an Overwrite header. 1015 The request body MUST be a DAV:rebind XML element. 1017 1019 If the request succeeds, the server MUST return 201 (Created) when 1020 a new binding was created and 200 (OK) when an existing binding 1021 was replaced. 1023 If a response body for a successful request is included, it MUST 1024 be a DAV:rebind-response XML element. Note that this document 1025 does not define any elements for the REBIND response body, but the 1026 DAV:rebind-response element is defined to ensure interoperability 1027 between future extensions that do define elements for the REBIND 1028 response body. 1030 1032 Preconditions: 1034 (DAV:rebind-into-collection): The Request-URI MUST identify a 1035 collection. 1037 (DAV:rebind-source-exists): The DAV:href element MUST identify a 1038 resource. 1040 (DAV:cross-server-binding): If the resource identified by the DAV: 1041 href element in the request body is on another server from the 1042 collection identified by the Request-URI, the server MUST support 1043 cross-server bindings. 1045 (DAV:name-allowed): The name specified by the DAV:segment is 1046 available for use as a new binding name. 1048 (DAV:can-overwrite): If the collection already contains a binding 1049 with the specified path segment, and if an Overwrite header is 1050 included, the value of the Overwrite header MUST be "T". 1052 (DAV:cycle-allowed): If the DAV:href element identifies a 1053 collection, and if the Request-URI identifies a collection that is 1054 a member of that collection, the server MUST support cycles in the 1055 URI namespace. 1057 (DAV:locked-update-allowed): If the collection identified by the 1058 Request-URI is write-locked, then the appropriate token MUST be 1059 specified in the request. 1061 (DAV:protected-url-modification-allowed): If the collection 1062 identified by the Request-URI already contains a binding with the 1063 specified path segment, and if that binding is protected by a 1064 write-lock, then the appropriate token MUST be specified in the 1065 request. 1067 (DAV:locked-source-collection-update-allowed): If the collection 1068 identified by the parent collection prefix of the DAV:href URI is 1069 write-locked, then the appropriate token MUST be specified in the 1070 request. 1072 (DAV:protected-source-url-deletion-allowed): If the DAV:href URI 1073 is protected by a write lock, then the appropriate token MUST be 1074 specified in the request. 1076 Postconditions: 1078 (DAV:new-binding): The collection MUST have a binding that maps 1079 the segment specified in the DAV:segment element in the request 1080 body, to the resource that was identified by the DAV:href element 1081 in the request body. 1083 (DAV:binding-deleted): The URL specified in the DAV:href element 1084 in the request body MUST NOT be mapped to a resource. 1086 (DAV:lock-deleted): If the URL specified in the DAV:href element 1087 in the request body was protected by a write-lock at the time of 1088 the request, that write-lock must have been deleted by the 1089 request. 1091 6.1. Example: REBIND 1093 >> Request: 1095 REBIND /CollX HTTP/1.1 1096 Host: www.example.com 1097 Content-Type: application/xml; charset="utf-8" 1098 Content-Length: xxx 1100 1101 1102 foo.html 1103 http://www.example.com/CollY/bar.html 1104 1106 >> Response: 1108 HTTP/1.1 200 OK 1110 The server added a new binding to the collection, 1111 "http://www.example.com/CollX", associating "foo.html" with the 1112 resource identified by the URI 1113 "http://www.example.com/CollY/bar.html", and removes the binding 1114 named "bar.html" from the collection identified by the URI 1115 "http://www.example.com/CollY". Clients can now use the URI 1116 "http://www.example.com/CollX/foo.html" to submit requests to that 1117 resource, and requests on the URI 1118 "http://www.example.com/CollY/bar.html" will fail with a 404 (Not 1119 Found) response. 1121 6.2. Example: REBIND in presence of locks and bind loops 1123 To illustrate the effects of locks and bind loops on a REBIND 1124 operation, consider the following collection: 1126 +------------------+ 1127 | Root Collection | 1128 | bindings: | 1129 | CollW | 1130 +------------------+ 1131 | 1132 | 1133 | 1134 +-------------------------------+ 1135 | Collection C1 |<--------+ 1136 | LOCKED infinity | | 1137 | (lock token L1) | | 1138 | bindings: | | 1139 | CollX CollY | | 1140 +-------------------------------+ | 1141 | | | 1142 | | (creates loop) | 1143 | | | 1144 +-----------------+ +------------------+ | 1145 | Collection C2 | | Collection C3 | | 1146 | (inherit lock) | | (inherit lock) | | 1147 | (lock token L1) | | (lock token L1) | | 1148 | bindings: | | bindings: | | 1149 | {none} | | y.gif CollZ | | 1150 +-----------------+ +------------------+ | 1151 | | | 1152 | +-----+ 1153 | 1154 +---------------------------+ 1155 | Resource R2 | 1156 | (lock inherited from C1) | 1157 | (lock token L1) | 1158 +---------------------------+ 1160 (where L1 is "opaquelocktoken:f92d4fae-7012-11ab-a765-00c0ca1f6bf9"). 1162 Note that the binding between CollZ and C1 creates a loop in the 1163 containment hierarchy. Servers are not required to support such 1164 loops, though the server in this example does. 1166 The REBIND request below will remove the segment "CollZ" from C3 and 1167 add a new binding from "CollA" to the collection C2. 1169 REBIND /CollW/CollX HTTP/1.1 1170 Host: www.example.com 1171 If: () 1172 Content-Type: application/xml; charset="utf-8" 1173 Content-Length: xxx 1175 1176 1177 CollA 1178 /CollW/CollY/CollZ 1179 1180 The outcome of the REBIND operation is: 1182 +------------------+ 1183 | Root Collection | 1184 | bindings: | 1185 | CollW | 1186 +------------------+ 1187 | 1188 | 1189 | 1190 +-------------------------------+ 1191 | Collection C1 | 1192 | LOCKED infinity | 1193 | (lock token L1) | 1194 | bindings: | 1195 | CollX CollY | 1196 +-------------------------------+ 1197 | ^ | 1198 | | | 1199 +-----------------+ | +------------------+ 1200 | Collection C2 | | | Collection C3 | 1201 |(inherited lock) | | | (inherited lock) | 1202 |(lock token L1) | | | (lock token L1) | 1203 | bindings: | | | bindings: | 1204 | CollA | | | y.gif | 1205 +-----------------+ | +------------------+ 1206 | | | 1207 +---------------+ | 1208 (creates loop) | 1209 +---------------------------+ 1210 | Resource R2 | 1211 | (inherited lock from C1) | 1212 | (lock token L1) | 1213 +---------------------------+ 1215 7. Additional Status Codes 1217 7.1. 208 Already Reported 1219 The 208 (Already Reported) status code can be used inside a DAV: 1220 propstat response element to avoid enumerating the internal members 1221 of multiple bindings to the same collection repeatedly. For each 1222 binding to a collection inside the request's scope, only one will be 1223 reported with a 200 status, while subsequent DAV:response elements 1224 for all other bindings will use the 208 status, and no DAV:response 1225 elements for their descendants are included. 1227 Note that the 208 status will only occur for "Depth: infinity" 1228 requests, and that it is of particular importance when the multiple 1229 collection bindings cause a bind loop as discussed in Section 2.2. 1231 A client can request the DAV:resource-id property in a PROPFIND 1232 request to guarantee that they can accurately reconstruct the binding 1233 structure of a collection with multiple bindings to a single 1234 resource. 1236 For backward compatibility with clients not aware of the 208 status 1237 code appearing in multistatus response bodies, it SHOULD NOT be used 1238 unless the client has signalled support for this specification using 1239 the "DAV" request header (see Section 8.2). Instead, a 506 status 1240 should be returned when a binding loop is discovered. This allows 1241 the server to return the 506 as the top level return status, if it 1242 discovers it before it started the response, or in the middle of a 1243 multistatus, if it discovers it in the middle of streaming out a 1244 multistatus response. 1246 7.1.1. Example: PROPFIND by bind-aware client 1248 For example, consider a PROPFIND request on /Coll (bound to 1249 collection C), where the members of /Coll are /Coll/Foo (bound to 1250 resource R) and /Coll/Bar (bound to collection C). 1252 >> Request: 1254 PROPFIND /Coll/ HTTP/1.1 1255 Host: www.example.com 1256 Depth: infinity 1257 DAV: bind 1258 Content-Type: application/xml; charset="utf-8" 1259 Content-Length: xxx 1261 1262 1263 1264 1265 1266 1267 1269 >> Response: 1271 HTTP/1.1 207 Multi-Status 1272 Content-Type: application/xml; charset="utf-8" 1273 Content-Length: xxx 1275 1276 1277 1278 http://www.example.com/Coll/ 1279 1280 1281 Loop Demo 1282 1283 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf8 1285 1286 1287 HTTP/1.1 200 OK 1288 1289 1290 1291 http://www.example.com/Coll/Foo 1292 1293 1294 Bird Inventory 1295 1296 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf9 1298 1299 1300 HTTP/1.1 200 OK 1301 1302 1303 1304 http://www.example.com/Coll/Bar 1305 1306 1307 Loop Demo 1308 1309 urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf8 1311 1312 1313 HTTP/1.1 208 Already Reported 1314 1315 1316 1318 7.1.2. Example: PROPFIND by non-bind-aware client 1320 In this example, the client isn't aware of the 208 status code 1321 introduced by this specification. As the "Depth: infinity" PROPFIND 1322 request would cause a loop condition, the whole request is rejected 1323 with a 506 status. 1325 >> Request: 1327 PROPFIND /Coll/ HTTP/1.1 1328 Host: www.example.com 1329 Depth: infinity 1330 Content-Type: application/xml; charset="utf-8" 1331 Content-Length: xxx 1333 1334 1335 1336 1338 >> Response: 1340 HTTP/1.1 506 Loop Detected 1342 7.2. 506 Loop Detected 1344 The 506 (Loop Detected) status code indicates that the server 1345 terminated an operation because it encountered an infinite loop while 1346 processing a request with "Depth: infinity". This status indicates 1347 that the entire operation failed. 1349 8. Capability discovery 1351 8.1. OPTIONS method 1353 If the server supports bindings, it MUST return the compliance class 1354 name "bind" as a field in the "DAV" response header (see 1355 [draft-ietf-webdav-rfc2518bis], Section 10.1) from an OPTIONS request 1356 on any resource implemented by that server. A value of "bind" in the 1357 "DAV" header MUST indicate that the server supports all MUST level 1358 requirements and REQUIRED features specified in this document. 1360 8.2. 'DAV' request header 1362 Clients SHOULD signal support for all MUST level requirements and 1363 REQUIRED features by submitting a "DAV" request header containing the 1364 compliance class name "bind". In particular, the client MUST 1365 understand the 208 status code defined in Section 7.1. 1367 9. Relationship to WebDAV Access Control Protocol 1369 BIND and REBIND behave the same as MOVE with respect to the DAV:acl 1370 property (see [RFC3744], Section 7.3). 1372 10. Security Considerations 1374 This section is provided to make WebDAV implementors aware of the 1375 security implications of this protocol. 1377 All of the security considerations of HTTP/1.1 and the WebDAV 1378 Distributed Authoring Protocol specification also apply to this 1379 protocol specification. In addition, bindings introduce several new 1380 security concerns and increase the risk of some existing threats. 1381 These issues are detailed below. 1383 10.1. Privacy Concerns 1385 In a context where cross-server bindings are supported, creating 1386 bindings on a trusted server may make it possible for a hostile agent 1387 to induce users to send private information to a target on a 1388 different server. 1390 10.2. Bind Loops 1392 Although bind loops were already possible in HTTP 1.1, the 1393 introduction of the BIND method creates a new avenue for clients to 1394 create loops accidentally or maliciously. If the binding and its 1395 target are on the same server, the server may be able to detect BIND 1396 requests that would create loops. Servers are required to detect 1397 loops that are caused by bindings to collections during the 1398 processing of any requests with "Depth: infinity". 1400 10.3. Bindings, and Denial of Service 1402 Denial of service attacks were already possible by posting URIs that 1403 were intended for limited use at heavily used Web sites. The 1404 introduction of BIND creates a new avenue for similar denial of 1405 service attacks. If cross-server bindings are supported, clients can 1406 now create bindings at heavily used sites to target locations that 1407 were not designed for heavy usage. 1409 10.4. Private Locations May Be Revealed 1411 If the DAV:parent-set property is maintained on a resource, the 1412 owners of the bindings risk revealing private locations. The 1413 directory structures where bindings are located are available to 1414 anyone who has access to the DAV:parent-set property on the resource. 1415 Moving a binding may reveal its new location to anyone with access to 1416 DAV:parent-set on its resource. 1418 10.5. DAV:parent-set and Denial of Service 1420 If the server maintains the DAV:parent-set property in response to 1421 bindings created in other administrative domains, it is exposed to 1422 hostile attempts to make it devote resources to adding bindings to 1423 the list. 1425 11. Internationalization Considerations 1427 All internationalization considerations mentioned in 1428 [draft-ietf-webdav-rfc2518bis] also apply to this document. 1430 12. IANA Considerations 1432 Section 7 defines the HTTP status codes 208 (Already Reported) and 1433 506 (Loop Detected), to be added to the registry at 1434 . 1436 13. Acknowledgements 1438 This document is the collaborative product of the authors and Tyson 1439 Chihaya, Jim Davis, Chuck Fay and Judith Slein. This draft has 1440 benefited from thoughtful discussion by Jim Amsden, Peter Carlson, 1441 Steve Carter, Ken Coar, Ellis Cohen, Dan Connolly, Bruce Cragun, 1442 Spencer Dawkins, Mark Day, Rajiv Dulepet, David Durand, Lisa 1443 Dusseault, Stefan Eissing, Roy Fielding, Yaron Goland, Joe 1444 Hildebrand, Fred Hitt, Alex Hopmann, James Hunt, Marcus Jager, Chris 1445 Kaler, Manoj Kasichainula, Rohit Khare, Brian Korver, Daniel 1446 LaLiberte, Steve Martin, Larry Masinter, Jeff McAffer, Surendra 1447 Koduru Reddy, Max Rible, Sam Ruby, Bradley Sergeant, Nick Shelness, 1448 John Stracke, John Tigue, John Turner, Kevin Wiggen, and other 1449 members of the WebDAV working group. 1451 14. References 1452 14.1. Normative References 1454 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1455 Requirement Levels", BCP 14, RFC 2119, March 1997. 1457 [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., 1458 Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext 1459 Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 1461 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 1462 Resource Identifier (URI): Generic Syntax", STD 66, 1463 RFC 3986, January 2005. 1465 [XML] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and 1466 F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth 1467 Edition)", W3C REC-xml-20060816, August 2006, 1468 . 1470 [draft-ietf-webdav-rfc2518bis] 1471 Dusseault, L., Ed., "HTTP Extensions for Distributed 1472 Authoring - WebDAV RFC2518 bis", 1473 draft-ietf-webdav-rfc2518bis-18 (work in progress), 1474 February 2007. 1476 14.2. Informative References 1478 [RFC3253] Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. 1479 Whitehead, "Versioning Extensions to WebDAV (Web 1480 Distributed Authoring and Versioning)", RFC 3253, 1481 March 2002. 1483 [RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web 1484 Distributed Authoring and Versioning (WebDAV) Access 1485 Control Protocol", RFC 3744, May 2004. 1487 [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally 1488 Unique IDentifier (UUID) URN Namespace", RFC 4122, 1489 July 2005. 1491 Appendix A. Clarification to RFC2518bis' Usage of the term 'lock root' 1493 [draft-ietf-webdav-rfc2518bis], Section 9.10.1 claims: 1495 A LOCK request to an existing resource will create a lock on the 1496 resource identified by the Request-URI, provided the resource is 1497 not already locked with a conflicting lock. The resource 1498 identified in the Request-URI becomes the root of the lock. 1500 This is incorrect in that it implies that the "lock root" is a 1501 resource, not a URL 1502 (). 1503 However, should a directly locked resource have multiple bindings, 1504 only the one used in the Request-URI of the LOCK request will be the 1505 protected from changes of clients not supplying the lock token. 1507 A correct description would be: 1509 A LOCK request to an existing resource will create a lock on the 1510 resource identified by the Request-URI, provided the resource is 1511 not already locked with a conflicting lock. The Request-URI 1512 becomes the root of the lock. 1514 Note that this change makes the description consistent with the 1515 definition of the DAV:lockroot XML element in Section 14.12 of 1516 [draft-ietf-webdav-rfc2518bis]. 1518 The authors of this specification recommend that future revisions of 1519 [draft-ietf-webdav-rfc2518bis] will update the description as 1520 suggested above. 1522 Appendix B. Change Log (to be removed by RFC Editor before publication) 1524 B.1. Since draft-ietf-webdav-bind-02 1526 Add and resolve issues "2.3_COPY_SHARED_BINDINGS" and 1527 "2.3_MULTIPLE_COPY". Add issue "5.1_LOOP_STATUS" and proposed 1528 resolution, but keep it open. Add issues "ED_references" and 1529 "4_507_status". Started work on index. Rename document to "Binding 1530 Extensions to Web Distributed Authoring and Versioning (WebDAV)". 1531 Rename "References" to "Normative References". Close issue 1532 "ED_references". Close issue "4_507_status". 1534 B.2. Since draft-ietf-webdav-bind-03 1536 Add and close issues "9.2_redirect_loops", "ED_authors" and 1537 "ED_updates". Add section about capability discovery (DAV header). 1538 Close issues "5.1_LOOP_STATUS". Add and resolve new issue 1539 "5.1_506_STATUS_STREAMING". Update XML spec reference. Add issue 1540 "locking" and resolve as invalid. 1542 B.3. Since draft-ietf-webdav-bind-04 1544 Add and close issues "6_precondition_binding_allowed" and 1545 "6_lock_behaviour". Add mailing list and issues list pointers to 1546 front. 1548 B.4. Since draft-ietf-webdav-bind-05 1550 Editorial fixes. Add and resolve issues "1.3_error_negotiation", 1551 "2.5_language" and "7.1.1_add_resource_id". Add historical issue 1552 "4_LOCK_BEHAVIOR" and it's resolution for better tracking. 1554 B.5. Since draft-ietf-webdav-bind-06 1556 Rewrite Editorial Note. Open and resolve issues "2.6_identical", 1557 "specify_safeness_and_idempotence" and "ED_rfc2026_ref". 1559 B.6. Since draft-ietf-webdav-bind-07 1561 Add more index items (no change tracking). Add and resolve issues 1562 "2.3_copy_to_same", "bind_properties", "bind_vs_ACL", 1563 "6_rebind_intro" and "rfc2396bis" (actually an action item). Fix XML 1564 DTD fragment in section 3.3. Make spelling of "Request-URI" 1565 consistent. 1567 B.7. Since draft-ietf-webdav-bind-08 1569 Resolved editorial issues raised by Jim Whitehead in . 1571 Add and resolve issues "atomicity", "2_allow_destroy", 1572 "2.1_separate_loop_discussion", "2.1.1_bind_loops_vs_locks", 1573 "2.3_copy_depth_infinity", "2.3_copy_example", "2.3_copy_vs_loops", 1574 "2.6_resource-id_vs_versions", "3.2_example" and 1575 "6_rebind_premissions". Add issue "2.6_when_do_ids_change". Re-open 1576 and resolve "6_rebind_intro". 1578 B.8. Since draft-ietf-webdav-bind-09 1580 Add and resolve issue "6.1_rebind_vs_locks", adding proposed example 1581 text. Add action item "3.1_uuids". Close issue 1582 "2.6_when_do_ids_change". Add and resolve issues 1583 "2.6_bindings_vs_properties" and "uri_draft_ref". 1585 B.9. Since draft-ietf-webdav-bind-10 1587 Resolve action item "3.1_uuids". Add and resolve issue 1588 "2.7_unlock_vs_bindings". Revisit issue 1589 "2.6_bindings_vs_properties", and remove the part of the sentence 1590 that speaks about live properties. Update "rfc2396bis" references to 1591 "RFC3986". Add issue "9_ns_op_and_acl" and add potential resolution. 1592 Align artwork where applicable (new xml2rfc1.29rc2 feature). 1594 B.10. Since draft-ietf-webdav-bind-11 1596 Updated [draft-mealling-uuid-urn] to [RFC4122]. Add statement about 1597 live properties in Section 2.6. 1599 B.11. Since draft-ietf-webdav-bind-12 1601 Updated Author's address. Uppercase "Section" when referring to 1602 other documents. 1604 Updating from RFC2518 to RFC2518bis: 1606 o Remove own explanation of DTD syntax. 1608 o Remove own definition of precondition/postcondition. 1610 o Remove reference to broken RFC2518 language about DELETE and 1611 UNLOCK. 1613 o Remove own definition of DAV: request header. 1615 o Updated "Rationale for Distinguishing Bindings from URI Mappings" 1616 to reflect the changes in [draft-ietf-webdav-rfc2518bis], making 1617 proposals for more changes so that the issue can be closed (see 1618 also 1619 and ). 1622 B.12. Since draft-ietf-webdav-bind-13 1624 Update [draft-ietf-webdav-rfc2518-bis] to draft 14. Update one 1625 incorrect section reference. Remove Section "Rationale for 1626 Distinguishing Bindings from URI Mappings" as 1627 [draft-ietf-webdav-rfc2518-bis] now uses the proper definition of 1628 collection state. Examples use application/xml instead of text/xml 1629 MIME type. 1631 Fix IANA section (there are no IANA considerations). 1633 B.13. Since draft-ietf-webdav-bind-14 1635 Update [draft-ietf-webdav-rfc2518-bis] to draft 15. Update [XML] to 1636 4th edition. 1638 Markup ASCII art for box recognition (doesn't affect ASCII version). 1640 Identify Julian Reschke as Editor. 1642 B.14. Since draft-ietf-webdav-bind-15 1644 Fix typo in RFC2119 keywords section (sorry!). 1646 Update [draft-ietf-webdav-rfc2518-bis] to draft 17. 1648 Add and resolve issue "rfc2518bis-lock-root". 1650 B.15. Since draft-ietf-webdav-bind-16 1652 Add and resolve issue "iana-vs-http-status". 1654 B.16. Since draft-ietf-webdav-bind-17 1656 Update rfc2518bis reference to draft 18 (note that the bug reported 1657 in 1658 is still present). 1660 Appendix C. Open issues (to be removed by RFC Editor prior to 1661 publication) 1663 C.1. edit 1665 Type: edit 1667 julian.reschke@greenbytes.de (2004-05-30): Umbrella issue for 1668 editorial fixes/enhancements. 1670 Index 1672 2 1673 208 Already Reported (status code) 28, 33 1675 5 1676 506 Loop Detected (status code) 31, 33 1678 B 1679 BIND method 18 1680 Marshalling 19 1681 Postconditions 20 1682 Preconditions 19 1683 Binding 6 1685 C 1686 Collection 6 1687 Condition Names 1688 DAV:bind-into-collection (pre) 19 1689 DAV:bind-source-exists (pre) 19 1690 DAV:binding-allowed (pre) 20 1691 DAV:binding-deleted (post) 22, 25 1692 DAV:can-overwrite (pre) 20, 24 1693 DAV:cross-server-binding (pre) 20, 24 1694 DAV:cycle-allowed (pre) 20, 24 1695 DAV:lock-deleted (post) 22, 25 1696 DAV:locked-overwrite-allowed (pre) 20 1697 DAV:locked-source-collection-update-allowed (pre) 24 1698 DAV:locked-update-allowed (pre) 20, 22, 24 1699 DAV:name-allowed (pre) 20, 24 1700 DAV:new-binding (post) 20, 25 1701 DAV:protected-source-url-deletion-allowed (pre) 25 1702 DAV:protected-url-deletion-allowed (pre) 22 1703 DAV:protected-url-modification-allowed (pre) 24 1704 DAV:rebind-from-collection (pre) 24 1705 DAV:rebind-source-exists (pre) 24 1706 DAV:unbind-from-collection (pre) 22 1707 DAV:unbind-source-exists (pre) 22 1709 D 1710 DAV header 1711 compliance class 'bind' 31 1712 DAV:bind-into-collection precondition 19 1713 DAV:bind-source-exists precondition 19 1714 DAV:binding-allowed precondition 20 1715 DAV:binding-deleted postcondition 22, 25 1716 DAV:can-overwrite precondition 20, 24 1717 DAV:cross-server-binding precondition 20, 24 1718 DAV:cycle-allowed precondition 20, 24 1719 DAV:lock-deleted postcondition 22, 25 1720 DAV:locked-overwrite-allowed precondition 20 1721 DAV:locked-source-collection-update-allowed precondition 24 1722 DAV:locked-update-allowed precondition 20, 22, 24 1723 DAV:name-allowed precondition 20, 24 1724 DAV:new-binding postcondition 20, 25 1725 DAV:parent-set property 17 1726 DAV:protected-source-url-deletion-allowed precondition 25 1727 DAV:protected-url-deletion-allowed precondition 22 1728 DAV:protected-url-modification-allowed precondition 24 1729 DAV:rebind-from-collection precondition 24 1730 DAV:rebind-source-exists precondition 24 1731 DAV:resource-id property 17 1732 DAV:unbind-from-collection precondition 22 1733 DAV:unbind-source-exists precondition 22 1735 I 1736 Internal Member URI 6 1738 M 1739 Methods 1740 BIND 18 1741 REBIND 23 1742 UNBIND 21 1744 P 1745 Path Segment 6 1746 Properties 1747 DAV:parent-set 17 1748 DAV:resource-id 17 1750 R 1751 REBIND method 23 1752 Marshalling 23 1753 Postconditions 25 1754 Preconditions 24 1756 S 1757 Status Codes 1758 208 Already Reported 28, 33 1759 506 Loop Detected 31, 33 1761 U 1762 UNBIND method 21 1763 Marshalling 21 1764 Postconditions 22 1765 Preconditions 22 1766 URI Mapping 5 1768 Authors' Addresses 1770 Geoffrey Clemm 1771 IBM 1772 20 Maguire Road 1773 Lexington, MA 02421 1775 Email: geoffrey.clemm@us.ibm.com 1776 Jason Crawford 1777 IBM Research 1778 P.O. Box 704 1779 Yorktown Heights, NY 10598 1781 Email: ccjason@us.ibm.com 1783 Julian F. Reschke (editor) 1784 greenbytes GmbH 1785 Hafenweg 16 1786 Muenster, NW 48155 1787 Germany 1789 Email: julian.reschke@greenbytes.de 1791 Jim Whitehead 1792 UC Santa Cruz, Dept. of Computer Science 1793 1156 High Street 1794 Santa Cruz, CA 95064 1796 Email: ejw@cse.ucsc.edu 1798 Full Copyright Statement 1800 Copyright (C) The IETF Trust (2007). 1802 This document is subject to the rights, licenses and restrictions 1803 contained in BCP 78, and except as set forth therein, the authors 1804 retain all their rights. 1806 This document and the information contained herein are provided on an 1807 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 1808 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 1809 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 1810 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 1811 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 1812 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 1814 Intellectual Property 1816 The IETF takes no position regarding the validity or scope of any 1817 Intellectual Property Rights or other rights that might be claimed to 1818 pertain to the implementation or use of the technology described in 1819 this document or the extent to which any license under such rights 1820 might or might not be available; nor does it represent that it has 1821 made any independent effort to identify any such rights. 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