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'XML' Summary: 6 errors (**), 0 flaws (~~), 7 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT G. Clemm 3 draft-ietf-webdav-bind-01 Rational Software 4 J. Crawford 5 IBM Research 6 J. Reschke 7 Greenbytes 8 J. Slein 9 Xerox 10 E.J. Whitehead 11 U.C. Santa Cruz 13 Expires August 7, 2003 February 7, 2003 15 Binding Extensions to WebDAV 17 Status of this Memo 18 This document is an Internet-Draft and is in full conformance with all 19 provisions of RFC 2026, Section 10. 21 Internet-Drafts are working documents of the Internet Engineering Task 22 Force (IETF), its areas, and its working groups. Note that other groups 23 may also distribute working documents as Internet-Drafts. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference material 28 or to cite them other than as "work in progress." 30 The list of current Internet-Drafts can be accessed at 31 http://www.ietf.org/ietf/1id-abstracts.txt 33 The list of Internet-Draft Shadow Directories can be accessed at 34 http://www.ietf.org/shadow.html. 36 Abstract 37 This specification defines bindings, and the BIND method for creating 38 multiple bindings to the same resource. Creating a new binding to a 39 resource causes at least one new URI to be mapped to that resource. 40 Servers are required to insure the integrity of any bindings that they 41 allow to be created. 43 Table of Contents 45 1 INTRODUCTION............................................3 46 1.1 Terminology...........................................4 47 1.2 Rationale for Distinguishing Bindings from URI Mappings 48 ......................................................6 50 2 OVERVIEW OF BINDINGS....................................6 51 2.1 Bindings to Collections...............................7 52 2.2 URI Mappings Created by a new Binding.................7 53 2.3 DELETE and Bindings...................................8 54 2.4 COPY and Bindings.....................................9 55 2.5 MOVE and Bindings.....................................9 56 2.6 Determining Whether Two Bindings Are to the Same Resource 57 .....................................................10 58 2.7 Discovering the Bindings to a Resource...............11 60 3 PROPERTIES.............................................11 61 3.1 DAV:resource-id Property.............................12 62 3.2 DAV:parent-set Property..............................12 64 4 BIND METHOD............................................12 65 4.1 Example: BIND........................................14 67 5 ADDITIONAL STATUS CODES................................14 68 5.1 506 Loop Detected....................................14 70 6 SECURITY CONSIDERATIONS................................16 71 6.1 Privacy Concerns.....................................16 72 6.2 Redirect Loops.......................................16 73 6.3 Bindings, and Denial of Service......................16 74 6.4 Private Locations May Be Revealed....................16 75 6.5 DAV:parent-set and Denial of Service.................17 77 7 INTERNATIONALIZATION CONSIDERATIONS....................17 79 8 IANA CONSIDERATIONS....................................17 81 9 INTELLECTUAL PROPERTY..................................17 83 10 ACKNOWLEDGEMENTS.....................................17 85 11 REFERENCES...........................................18 87 12 AUTHORS' ADDRESSES...................................18 88 1 INTRODUCTION 90 This specification extends the WebDAV Distributed Authoring 91 Protocol to enable clients to create new access paths to existing 92 resources. This capability is useful for several reasons: 94 URIs of WebDAV-compliant resources are hierarchical and correspond 95 to a hierarchy of collections in resource space. The WebDAV 96 Distributed Authoring Protocol makes it possible to organize these 97 resources into hierarchies, placing them into groupings, known as 98 collections, which are more easily browsed and manipulated than a 99 single flat collection. However, hierarchies require 100 categorization decisions that locate resources at a single location 101 in the hierarchy, a drawback when a resource has multiple valid 102 categories. For example, in a hierarchy of vehicle descriptions 103 containing collections for cars and boats, a description of a 104 combination car/boat vehicle could belong in either collection. 105 Ideally, the description should be accessible from both. Allowing 106 clients to create new URIs that access the existing resource lets 107 them put that resource into multiple collections. 109 Hierarchies also make resource sharing more difficult, since 110 resources that have utility across many collections are still 111 forced into a single collection. For example, the mathematics 112 department at one university might create a collection of 113 information on fractals that contains bindings to some local 114 resources, but also provides access to some resources at other 115 universities. For many reasons, it may be undesirable to make 116 physical copies of the shared resources on the local server: to 117 conserve disk space, to respect copyright constraints, or to make 118 any changes in the shared resources visible automatically. Being 119 able to create new access paths to existing resources in other 120 collections or even on other servers is useful for this sort of 121 case. 123 The BIND method defined here provides a mechanism for allowing 124 clients to create alternative access paths to existing WebDAV 125 resources. HTTP and WebDAV methods are able to work because there 126 are mappings between URIs and resources. A method is addressed to 127 a URI, and the server follows the mapping from that URI to a 128 resource, applying the method to that resource. Multiple URIs may 129 be mapped to the same resource, but until now there has been no way 130 for clients to create additional URIs mapped to existing resources. 132 BIND lets clients associate a new URI with an existing WebDAV 133 resource, and this URI can then be used to submit requests to the 134 resource. Since URIs of WebDAV resources are hierarchical, and 135 correspond to a hierarchy of collections in resource space, the 136 BIND method also has the effect of adding the resource to a 137 collection. As new URIs are associated with the resource, it 138 appears in additional collections. 140 A BIND request does not create a new resource, but simply makes 141 available a new URI for submitting requests to an existing 142 resource. The new URI is indistinguishable from any other URI when 143 submitting a request to a resource. Only one round trip is needed 144 to submit a request to the intended target. Servers are required 145 to enforce the integrity of the relationships between the new URIs 146 and the resources associated with them. Consequently, it may be 147 very costly for servers to support BIND requests that cross server 148 boundaries. 150 This specification is organized as follows. Section 1.1 defines 151 terminology used in the rest of the specification, while Section 2 152 overviews bindings. Section 3 specifies the BIND method, used to 153 create multiple bindings to the same resource. Sections Error! 154 Reference source not found. defines the new properties needed to 155 support multiple bindings to the same resource. 157 1.1 Terminology 159 The terminology used here follows and extends that in the WebDAV 160 Distributed Authoring Protocol specification [RFC2518]. 162 URI Mapping 164 A relation between an absolute URI and a resource. For an absolute 165 URI U and the resource it identifies R, the URI mapping can be 166 thought of as (U => R). Since a resource can represent items that 167 are not network retrievable, as well as those that are, it is 168 possible for a resource to have zero, one, or many URI mappings. 169 Mapping a resource to an "http" scheme URL makes it possible to 170 submit HTTP protocol requests to the resource using the URL. 172 Path Segment 174 Informally, the characters found between slashes ("/") in a URI. 175 Formally, as defined in section 3.3 of [RFC2396]. 177 Binding 179 A relation between a single path segment (in a collection) and a 180 resource. A binding is part of the state of a collection. If two 181 different collections contain a binding between the same path 182 segment and the same resource, these are two distinct bindings. So 183 for a collection C, a path segment S, and a resource R, the binding 184 can be thought of as C:(S -> R). Bindings create URI mappings, and 185 hence allow requests to be sent to a single resource from multiple 186 locations in a URI namespace. For example, given a collection C 187 (accessible through the URI http://www.example.com/coll/), a path 188 segment S (equal to "foo.html"), and a resource R, then creating 189 the binding C: (S -> R) makes it possible to use the URI 190 http://www.example.com/coll/foo.html to access R. 192 Collection 194 A resource that contains, as part of its state, a set of bindings 195 that identify internal member resources. 197 Internal Member URI 199 The URI that identifies an internal member of a collection, and 200 that consists of the URI for the collection, followed by a slash 201 character ('/'), followed by the path segment of the binding for 202 that internal member. 204 1.2 Rationale for Distinguishing Bindings from URI Mappings 206 In [RFC2518], the state of a collection is defined as containing a 207 list of internal member URIs. If there are multiple mappings to a 208 collection, then the state of the collection is different when you 209 refer to it via a different URI. This is undesirable, since ideally 210 a collection's membership should remain the same, independent of 211 which URI was used to reference it. 213 The notion of binding is introduced to separate the final segment 214 of a URI from its parent collection's contribution. This done, a 215 collection can be defined as containing a set of bindings, thus 216 permitting new mappings to a collection without modifying its 217 membership. The authors of this specification anticipate and 218 recommend that future revisions of [RFC2518] will update the 219 definition of the state of a collection to correspond to the 220 definition in this document. 222 2 OVERVIEW OF BINDINGS 224 Bindings are part of the state of a collection. They define the 225 internal members of the collection, and the names of those internal 226 members. 228 Bindings are added and removed by a variety of existing HTTP 229 methods. A method that creates a new resource, such as PUT, COPY, 230 and MKCOL, adds a binding. A method that deletes a resource, such 231 as DELETE, removes a binding. A method that moves a resource (e.g. 232 MOVE) both adds a binding (in the destination collection) and 233 removes a binding (in the source collection). The BIND method 234 introduced here provides a mechanism for adding a second binding to 235 an existing resource. There is no difference between an initial 236 binding added by PUT, COPY, or MKCOL, and additional bindings added 237 with BIND. 239 It would be very undesirable if one binding could be destroyed as a 240 side effect of operating on the resource through a different 241 binding. In particular, the removal of one binding to a resource 242 (e.g. with a DELETE or a MOVE) MUST NOT disrupt another binding to 243 that resource, e.g. by turning that binding into a dangling path 244 segment. The server MUST NOT reclaim system resources after 245 removing one binding, while other bindings to the resource remain. 246 In other words, the server MUST maintain the integrity of a 247 binding. 249 2.1 Bindings to Collections 251 Bindings to collections can result in loops, which servers MUST 252 detect when processing "Depth: infinity" requests. It is sometimes 253 possible to complete an operation in spite of the presence of a 254 loop. However, the 506 (Loop Detected) status code is defined in 255 Section 5 for use in contexts where an operation is terminated 256 because a loop was encountered. 258 Creating a new binding to a collection makes each resource 259 associated with a binding in that collection accessible via a new 260 URI, and thus creates new URI mappings to those resources but no 261 new bindings. 263 For example, suppose a new binding CollY is created for collection 264 C1 in the figure below. It immediately becomes possible to access 265 resource R1 using the URI /CollY/x.gif and to access resource R2 266 using the URI /CollY/y.jpg, but no new bindings for these child 267 resources were created. This is because bindings are part of the 268 state of a collection, and associate a URI that is relative to that 269 collection with its target resource. No change to the bindings in 270 Collection C1 is needed to make its children accessible using 271 /CollY/x.gif and /CollY/y.jpg. 273 +-------------------------+ 274 | Root Collection | 275 | (properties) | 276 | bindings: | 277 | CollX CollY | 278 +-------------------------+ 279 | / 280 | / 281 | / 282 +------------------+ 283 | Collection C1 | 284 | (properties) | 285 | bindings: | 286 | x.gif y.jpg | 287 +------------------+ 288 | \ 289 | \ 290 | \ 291 +-------------+ +-------------+ 292 | Resource R1 | | Resource R2 | 293 +-------------+ +-------------+ 295 2.2 URI Mappings Created by a new Binding 297 Suppose a binding from "Binding-Name" to resource R to be added to 298 a collection, C. Then if C-MAP is the set of URI's that were 299 mapped to C before the BIND request, then for each URI "C-URI" in 300 C-MAP, the URI "C-URI/Binding-Name" is mapped to resource R 301 following the BIND request. 303 For example, if a binding from "foo.html" to R is added to a 304 collection C, and if the following URI's are mapped to C: 306 http://www.example.com/A/1/ 307 http://example.com/A/one/ 309 then the following new mappings to R are introduced: 311 http://www.example.com/A/1/foo.html 312 http://example.com/A/one/foo.html 314 Note that if R is a collection, additional URI mappings are created 315 to the descendents of R. Also, note that if a binding is made in 316 collection C to C itself (or to a parent of C), an infinite number 317 of mappings are introduced. 319 For example, if a binding from "myself" to C is then added to C, 320 the following infinite number of additional mappings to C are 321 introduced: 323 http://www.example.com/A/1/myself 324 http://www.example.com/A/1/myself/myself 325 ... 327 and the following infinite number of additional mappings to R are 328 introduced: 330 http://www.example.com/A/1/myself/foo.html 331 http://www.example.com/A/1/myself/myself/foo.html 332 ... 334 2.3 DELETE and Bindings 336 The DELETE method was originally defined in [RFC2616]. This section 337 redefines the behavior of DELETE in terms of bindings, an 338 abstraction not available when writing [RFC2616]. [RFC2616] states 339 that "the DELETE method requests that the origin server delete the 340 resource identified by the Request-URI." Because [RFC2616] did not 341 distinguish between bindings and resources, the intent of its 342 definition of DELETE is unclear. The definition presented here is 343 a clarification of the definition in [RFC2616]. 345 The DELETE method requests that the server remove the binding 346 between the resource identified by the Request-URI and the binding 347 name, the last path segment of the Request-URI. The binding MUST be 348 removed from its parent collection, identified by the Request-URI 349 minus its trailing slash (if present) and final segment. 351 Once a resource is unreachable by any URI mapping, the server MAY 352 reclaim system resources associated with that resource. If DELETE 353 removes a binding to a resource, but there remain URI mappings to 354 that resource, the server MUST NOT reclaim system resources 355 associated with the resource. 357 Although [RFC2518] allows a DELETE to be a non-atomic operation, 358 the DELETE operation defined here is atomic. In particular, a 359 DELETE on a hierarchy of resources is simply the removal of a 360 binding to the collection identified by the Request-URI, and so is 361 a single (and therefore atomic) operation. 363 Section 8.6.1 of [RFC2518] states that during DELETE processing, a 364 server "MUST remove any URI for the resource identified by the 365 Request-URI from collections which contain it as a member." 366 Servers that support bindings MUST NOT follow this requirement. 368 2.4 COPY and Bindings 370 As defined in Section 8.8 of [RFC2518], COPY causes the resource 371 identified by the Request-URI to be duplicated, and makes the new 372 resource accessible using the URI specified in the Destination 373 header. Upon successful completion of a COPY, a new binding is 374 created between the last path segment of the Destination header, 375 and the destination resource. The new binding is added to its 376 parent collection, identified by the Destination header minus its 377 trailing slash (if present) and final segment. 379 The following figure shows an example: Suppose that a COPY is 380 issued to URI 3 for resource R (which is also mapped to URI 1 and 381 URI 2), with the Destination header set to URIX. After successful 382 completion of the COPY operation, resource R is duplicated to 383 create resource R', and a new binding has been created which 384 creates at least the URI mapping between URIX and the new resource 385 (although other URI mappings may also have been created). 387 URI 1 URI 2 URI 3 URIX 388 | | | | 389 | | | <---- URI Mappings ----> | 390 | | | | 391 +---------------------+ +------------------------+ 392 | Resource R | | Resource R' | 393 +---------------------+ +------------------------+ 395 It might be thought that a COPY request with "Depth: 0" on a 396 collection would duplicate its bindings, since bindings are part of 397 the collection's state. This is not the case, however. The 398 definition of Depth in [RFC2518] makes it clear that a "Depth: 0" 399 request does not apply to a collection's members. Consequently, a 400 COPY with "Depth: 0" does not duplicate the bindings contained by 401 the collection. 403 2.5 MOVE and Bindings 405 The MOVE method has the effect of creating a new binding to a 406 resource (at the Destination), and removing an existing binding (at 407 the Request-URI). The name of the new binding is the last path 408 segment of the Destination header, and the new binding is added to 409 its parent collection, identified by the Destination header minus 410 its trailing slash (if present) and final segment. 412 As an example, suppose that a MOVE is issued to URI 3 for resource 413 R below (which is also mapped to URI 1 and URI 2), with the 414 Destination header set to URIX. After successful completion of the 415 MOVE operation, a new binding has been created which creates at 416 least the URI mapping between URIX and resource R (although other 417 URI mappings may also have been created). The binding 418 corresponding to the final segment of URI 3 has been removed, which 419 also causes the URI mapping between URI 3 and R to be removed. 421 >> Before Request: 423 URI 1 URI 2 URI 3 424 | | | 425 | | | <---- URI Mappings 426 | | | 427 +---------------------+ 428 | Resource R | 429 +---------------------+ 431 >> After Request: 433 URI 1 URI 2 URIX 434 | | | 435 | | | <---- URI Mappings 436 | | | 437 +---------------------+ 438 | Resource R | 439 +---------------------+ 441 Although [RFC2518] allows a MOVE on a collection to be a non-atomic 442 operation, the MOVE operation defined here MUST be atomic. Even 443 when the Request-URI identifies a collection, the MOVE operation 444 involves only removing one binding to that collection and adding 445 another. There are no operations on bindings to any of its 446 children, so the case of MOVE on a collection is the same as the 447 case of MOVE on a non-collection resource. Both are atomic. 449 2.5.1Additional MOVE Semantics 451 Additional Preconditions: 453 (DAV:cycle-allowed): If the request-URL identifies a collection, 454 and the parent of the Destination is that collection or is a member 455 of that collection, the server MUST support cycles in the URL 456 namespace. 458 2.6 Determining Whether Two Bindings Are to the Same Resource 460 It is useful to have some way of determining whether two bindings 461 are to the same resource. Two resources might have identical 462 contents and properties, but not be the same resource (e.g. an 463 update to one resource does not affect the other resource). 465 The REQUIRED DAV:resource-id property defined in Section 3.1 is a 466 resource identifier, which MUST be unique across all resources for 467 all time. If the values of DAV:resource-id returned by PROPFIND 468 requests through two bindings are identical, the client can be 469 assured that the two bindings are to the same resource. 471 The DAV:resource-id property is created, and its value assigned, 472 when the resource is created. The value of DAV:resource-id MUST 473 NOT be changed. Even after the resource is no longer accessible 474 through any URI, that value MUST NOT be reassigned to another 475 resource's DAV:resource-id property. 477 Any method that creates a new resource MUST assign a new, unique 478 value to its DAV:resource-id property. For example, a PUT that 479 creates a new resource must assign a new, unique value to its 480 DAV:resource-id property. A COPY, since it creates a new resource 481 at the Destination URI, must assign a new, unique value to its 482 DAV:resource-id property. 484 On the other hand, any method that affects an existing resource 485 MUST NOT change the value of its DAV:resource-id property. For 486 example, a PUT that updates an existing resource must not change 487 the value of its DAV:resource-id property. A MOVE, since it does 488 not create a new resource, but only changes the location of an 489 existing resource, must not change the value of its DAV:resource-id 490 property. 492 2.7 Discovering the Bindings to a Resource 494 An OPTIONAL DAV:parent-set property on a resource provides a list 495 of the bindings that associate a collection and a URI segment with 496 that resource. If the DAV:parent-set property exists on a given 497 resource, it MUST contain a complete list of all bindings to that 498 resource that the client is authorized to see. When deciding 499 whether to support the DAV:parent-set property, server implementers 500 / administrators should balance the benefits it provides against 501 the cost of maintaining the property and the security risks 502 enumerated in Sections 6.4 and 6.5. 504 3 PROPERTIES 506 The bind feature introduces the following properties for a 507 resource. 509 3.1 DAV:resource-id Property 511 The DAV:resource-id property is a REQUIRED property that enables 512 clients to determine whether two bindings are to the same resource. 513 The value of DAV:resource-id is a URI, and may use any registered 514 URI scheme that guarantees the uniqueness of the value across all 515 resources for all time (e.g. the opaquelocktoken: scheme defined in 516 [RFC2518]). 518 520 3.2 DAV:parent-set Property 522 The DAV:parent-set property is an OPTIONAL property that enables 523 clients to discover what collections contain a binding to this 524 resource (i.e. what collections have that resource as an internal 525 member). It contains an of href/segment pair for each collection 526 that has a binding to the resource. The href identifies the 527 collection, and the segment identifies the binding name of that 528 resource in that collection. 530 A given collection MUST appear only once in the DAV:parent-set for 531 any given binding, even if there are multiple URI mappings to that 532 collection. For example, if collection C1 is mapped to both /CollX 533 and /CollY, and C1 contains a binding named "x.gif" to a resource 534 R1, then either [/CollX, x.gif] or [/CollY, y.gif] can appear in 535 the DAV:parent-set of R1, but not both. But if C1 also had a 536 binding named "y.gif" to R1, then there would be two entries for C1 537 in the DAV:binding-set of R1 (i.e. either both [/CollX, x.gif] and 538 [/CollX, y.gif] or alternatively, both [/CollY, x.gif] and [/CollY, 539 y.gif]). 541 542 543 544 PCDATA value: segment, as defined in section 3.3 of [RFC2396] 546 4 BIND METHOD 548 The BIND method modifies the collection identified by the Request- 549 URI, by adding a new binding from the segment specified in the BIND 550 body to the resource identified in the BIND body. 552 If a server cannot guarantee the integrity of the binding, the BIND 553 request MUST fail. Note that it is especially difficult to 554 maintain the integrity of cross-server bindings. Unless the server 555 where the resource resides knows about all bindings on all servers 556 to that resource, it may unwittingly destroy the resource or make 557 it inaccessible without notifying another server that manages a 558 binding to the resource. For example, if server A permits creation 559 of a binding to a resource on server B, server A must notify server 560 B about its binding and must have an agreement with B that B will 561 not destroy the resource while A's binding exists. Otherwise 562 server B may receive a DELETE request that it thinks removes the 563 last binding to the resource and destroy the resource while A's 564 binding still exists. Status code 507 (Cross-server Binding 565 Forbidden) is defined in Section 5.1 for cases where servers fail 566 cross-server BIND requests because they cannot guarantee the 567 integrity of cross-server bindings. 569 By default, if there already is a binding for the specified segment 570 in the collection, the new binding replaces the existing binding. 571 This default binding replacement behavior can be overridden using 572 the Overwrite header defined in Section 9.6 of [RFC2518]. 574 Marshalling: 576 The request MAY include an Overwrite header. 578 The request body MUST be a DAV:bind XML element. 580 581 583 If the request succeeds, the server MUST return 201 (Created) when 584 a new binding was created and 204 (No Content) when an existing 585 binding was replaced. 587 If a response body for a successful request is included, it MUST be 588 a DAV:bind-response XML element. Note that this document does not 589 define any elements for the BIND response body, but the DAV:bind- 590 response element is defined to ensure interoperability between 591 future extensions that do define elements for the BIND response 592 body. 594 595 Preconditions: 597 (DAV:bind-into-collection): The Request-URL MUST identify a 598 collection. 600 (DAV:bind-source-exists): The DAV:href element MUST identify a 601 resource. 603 (DAV:binding-allowed): The resource identified by the DAV:href 604 supports multiple bindings to it. 606 (DAV:cross-server-binding): If the resource identified by the 607 DAV:href element in the request body is on another server from the 608 collection identified by the request-URL, the server MUST support 609 cross-server bindings. 611 (DAV:name-allowed): The name specified by the DAV:segment is 612 available for use as a new binding name. 614 (DAV:can-overwrite): If the collection already contains a binding 615 with the specified path segment, and if an Overwrite header is 616 included, the value of the Overwrite header MUST be "T". 618 (DAV:cycle-allowed): If the DAV:href element identifies a 619 collection, and if the request-URL identifies a collection that is 620 a member of that collection, the server MUST support cycles in the 621 URL namespace. 623 Postconditions: 625 (DAV:new-binding): The collection MUST have a binding that maps the 626 segment specified in the DAV:segment element in the request body, 627 to the resource identified by the DAV:href element in the request 628 body. 630 4.1 Example: BIND 632 >> Request: 634 BIND /coll HTTP/1.1 635 Host: www.example.com 636 Content-Type: text/xml; charset="utf-8" 637 Content-Length: xxx 639 640 641 bar.html 642 http://www.example.com/coll/foo.html 643 645 >> Response: 647 HTTP/1.1 200 OK 649 The server added a new binding to the collection, 650 "http://www.example.com/coll", associating "bar.html" with the 651 resource identified by the URL 652 "http://www.example.com/coll/foo.html". Clients can now use the 653 URL "http://www.example.com/coll/bar.html", to submit requests to 654 that resource. 656 5 ADDITIONAL STATUS CODES 658 5.1 506 Loop Detected 660 The 506 (Loop Detected) status code indicates that the server 661 terminated an operation because it encountered an infinite loop 662 while processing a request with "Depth: infinity". 664 When this status code is the top-level status code for the 665 operation, it indicates that the entire operation failed. 667 When this status code occurs inside a multi-status response, it 668 indicates only that a loop is being terminated, but does not 669 indicate failure of the operation as a whole. 671 For example, consider a PROPFIND request on /Coll (bound to 672 collection C), where the members of /Coll are /Coll/Foo (bound to 673 resource R) and /Coll/Bar (bound to collection C). 675 >> Request: 677 PROPFIND /Coll/ HTTP/1.1 678 Host: www.example.com 679 Depth: infinity 680 Content-Type: text/xml; charset="utf-8" 681 Content-Length: xxx 683 684 685 686 688 >> Response: 690 HTTP/1.1 207 Multi-Status 691 Content-Type: text/xml; charset="utf-8" 692 Content-Length: xxx 694 695 696 697 http://www.example.com/Coll/ 698 699 700 Loop Demo 701 702 HTTP/1.1 200 OK 703 704 705 706 http://www.example.com/Coll/Foo 707 708 709 Bird Inventory 710 711 HTTP/1.1 200 OK 712 713 714 715 http://www.example.com/Coll/Bar 716 HTTP/1.1 506 Loop Detected 717 718 719 6 SECURITY CONSIDERATIONS 721 This section is provided to make WebDAV applications aware of the 722 security implications of this protocol. 724 All of the security considerations of HTTP/1.1 and the WebDAV 725 Distributed Authoring Protocol specification also apply to this 726 protocol specification. In addition, bindings introduce several 727 new security concerns and increase the risk of some existing 728 threats. These issues are detailed below. 730 6.1 Privacy Concerns 732 In a context where cross-server bindings are supported, creating 733 bindings on a trusted server may make it possible for a hostile 734 agent to induce users to send private information to a target on a 735 different server. 737 6.2 Redirect Loops 739 Although redirect loops were already possible in HTTP 1.1, the 740 introduction of the BIND method creates a new avenue for clients to 741 create loops accidentally or maliciously. If the binding and its 742 target are on the same server, the server may be able to detect 743 BIND requests that would create loops. Servers are required to 744 detect loops that are caused by bindings to collections during the 745 processing of any requests with "Depth: infinity". 747 6.3 Bindings, and Denial of Service 749 Denial of service attacks were already possible by posting URLs 750 that were intended for limited use at heavily used Web sites. The 751 introduction of BIND creates a new avenue for similar denial of 752 service attacks. If cross-server bindings are supported, clients 753 can now create bindings at heavily used sites to target locations 754 that were not designed for heavy usage. 756 6.4 Private Locations May Be Revealed 758 If the DAV:parent-set property is maintained on a resource, the 759 owners of the bindings risk revealing private locations. The 760 directory structures where bindings are located are available to 761 anyone who has access to the DAV:parent-set property on the 762 resource. Moving a binding may reveal its new location to anyone 763 with access to DAV:parent-set on its resource. 765 6.5 DAV:parent-set and Denial of Service 767 If the server maintains the DAV:parent-set property in response to 768 bindings created in other administrative domains, it is exposed to 769 hostile attempts to make it devote resources to adding bindings to 770 the list. 772 7 INTERNATIONALIZATION CONSIDERATIONS 774 All internationalization considerations mentioned in [RFC2518] also 775 apply to this document. 777 8 IANA CONSIDERATIONS 779 All IANA considerations mentioned in [RFC2518] also apply to this 780 document. 782 9 INTELLECTUAL PROPERTY 784 The following notice is copied from RFC 2026, Section 10.4, and 785 describes the position of the IETF concerning intellectual property 786 claims made against this document. 788 The IETF takes no position regarding the validity or scope of any 789 intellectual property or other rights that might be claimed to 790 pertain to the implementation or use other technology described in 791 this document or the extent to which any license under such rights 792 might or might not be available; neither does it represent that it 793 has made any effort to identify any such rights. Information on 794 the procedures of the IETF with respect to rights in standards- 795 track and standards-related documentation can be found in BCP-11. 796 Copies of claims of rights made available for publication and any 797 assurances of licenses to be made available, or the result of an 798 attempt made to obtain a general license or permission for the use 799 of such proprietary rights by implementers or users of this 800 specification can be obtained from the IETF Secretariat. 802 The IETF invites any interested party to bring to its attention any 803 copyrights, patents or patent applications, or other proprietary 804 rights that may cover technology that may be required to practice 805 this standard. Please address the information to the IETF 806 Executive Director. 808 10 ACKNOWLEDGEMENTS 810 This draft is the collaborative product of the authors and Tyson 811 Chihaya, Jim Davis, and Chuck Fay. This draft has benefited from 812 thoughtful discussion by Jim Amsden, Peter Carlson, Steve Carter, 813 Ken Coar, Ellis Cohen, Dan Connolly, Bruce Cragun, Spencer Dawkins, 814 Mark Day, Rajiv Dulepet, David Durand, Roy Fielding, Yaron Goland, 815 Fred Hitt, Alex Hopmann, James Hunt, Marcus Jager, Chris Kaler, 816 Manoj Kasichainula, Rohit Khare, Daniel LaLiberte, Steve Martin, 817 Larry Masinter, Jeff McAffer, Surendra Koduru Reddy, Max Rible, Sam 818 Ruby, Bradley Sergeant, Nick Shelness, John Stracke, John Tigue, 819 John Turner, Kevin Wiggen, and other members of the WebDAV working 820 group. 822 11 REFERENCES 824 [RFC2026] S.Bradner, "The Internet Standards Process", RFC 2026, 825 October 1996. 827 [RFC2119] S.Bradner, "Key words for use in RFCs to Indicate 828 Requirement Levels", RFC 2119, March 1997. 830 [RFC2277] H.Alvestrand, "IETF Policy on Character Sets and 831 Languages." RFC 2277, January 1998. 833 [RFC2396] T. Berners-Lee, R. Fielding, L. Masinter, "Uniform 834 Resource Identifiers (URI): Generic Syntax." RFC 2396, August 1998. 836 [RFC2518] Y.Goland, E.Whitehead, A.Faizi, S.R.Carter, D.Jensen, 837 "HTTP Extensions for Distributed Authoring - WEBDAV", RFC 2518, 838 February 1999. 840 [RFC2616] R.Fielding, J.Gettys, J.C.Mogul, H.Frystyk, L.Masinter, 841 P.Leach, and T.Berners-Lee, "Hypertext Transfer Protocol -- 842 HTTP/1.1", RFC 2616, June 1999. 844 [XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible Markup 845 Language (XML) 1.0 (Second Edition)" W3C Recommendation 6 October 846 2000. http://www.w3.org/TR/2000/REC-xml-20001006. 848 12 AUTHORS' ADDRESSES 850 Geoffrey Clemm 851 Rational Software Corporation 852 20 Maguire Road 853 Lexington, MA 02173-3104 854 Email: geoffrey.clemm@rational.com 856 Jason Crawford 857 IBM Research 858 P.O. Box 704 859 Yorktown Heights, NY 10598 860 Email: ccjason@us.ibm.com 862 Julian F. Reschke 863 greenbytes GmbH 864 Salzmannstrasse 152 865 Muenster, NW 48159, Germany 866 Email: julian.reschke@greenbytes.de 867 Judy Slein 868 Xerox Corporation 869 800 Phillips Road, 105-50C 870 Webster, NY 14580 871 Email: jslein@crt.xerox.com 873 Jim Whitehead 874 UC Santa Cruz, Dept. of Computer Science 875 1156 High Street, Santa Cruz, CA 95064 876 Email: ejw@cse.ucsc.edu