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'XML' Summary: 6 errors (**), 0 flaws (~~), 9 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-00 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 April 2, 2002 October 2, 2001 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 Mappings6 49 2 OVERVIEW OF BINDINGS...................................6 50 2.1 Bindings to Collections...............................7 51 2.2 URI Mappings Created by a new Binding.................7 52 2.3 DELETE and Bindings...................................8 53 2.4 COPY and Bindings.....................................9 54 2.5 MOVE and Bindings....................................10 55 2.6 Determining Whether Two Bindings Are to the Same Resource..........10 56 2.7 Discovering the Bindings to a Resource...............11 58 3 PROPERTIES............................................11 59 3.1 DAV:resource-id Property.............................11 60 3.2 DAV:parent-set Property..............................12 62 4 BIND METHOD...........................................12 63 4.1 Example: BIND........................................13 65 5 ADDITIONAL STATUS CODES...............................14 66 5.1 506 Loop Detected....................................14 68 6 SECURITY CONSIDERATIONS...............................15 69 6.1 Privacy Concerns.....................................15 70 6.2 Redirect Loops.......................................15 71 6.3 Bindings, and Denial of Service......................16 72 6.4 Private Locations May Be Revealed....................16 73 6.5 DAV:parent-set and Denial of Service.................16 75 7 INTERNATIONALIZATION CONSIDERATIONS...................16 77 8 IANA CONSIDERATIONS...................................16 79 9 INTELLECTUAL PROPERTY.................................16 81 10 ACKNOWLEDGEMENTS.....................................17 83 11 REFERENCES...........................................17 85 12 AUTHORS' ADDRESSES...................................18 86 1 INTRODUCTION 88 This specification extends the WebDAV Distributed Authoring 89 Protocol to enable clients to create new access paths to existing 90 resources. This capability is useful for several reasons: 92 URIs of WebDAV-compliant resources are hierarchical and correspond 93 to a hierarchy of collections in resource space. The WebDAV 94 Distributed Authoring Protocol makes it possible to organize these 95 resources into hierarchies, placing them into groupings, known as 96 collections, which are more easily browsed and manipulated than a 97 single flat collection. However, hierarchies require 98 categorization decisions that locate resources at a single location 99 in the hierarchy, a drawback when a resource has multiple valid 100 categories. For example, in a hierarchy of vehicle descriptions 101 containing collections for cars and boats, a description of a 102 combination car/boat vehicle could belong in either collection. 103 Ideally, the description should be accessible from both. Allowing 104 clients to create new URIs that access the existing resource lets 105 them put that resource into multiple collections. 107 Hierarchies also make resource sharing more difficult, since 108 resources that have utility across many collections are still 109 forced into a single collection. For example, the mathematics 110 department at one university might create a collection of 111 information on fractals that contains bindings to some local 112 resources, but also provides access to some resources at other 113 universities. For many reasons, it may be undesirable to make 114 physical copies of the shared resources on the local server: to 115 conserve disk space, to respect copyright constraints, or to make 116 any changes in the shared resources visible automatically. Being 117 able to create new access paths to existing resources in other 118 collections or even on other servers is useful for this sort of 119 case. 121 The BIND method defined here provides a mechanism for allowing 122 clients to create alternative access paths to existing WebDAV 123 resources. HTTP and WebDAV methods are able to work because there 124 are mappings between URIs and resources. A method is addressed to 125 a URI, and the server follows the mapping from that URI to a 126 resource, applying the method to that resource. Multiple URIs may 127 be mapped to the same resource, but until now there has been no way 128 for clients to create additional URIs mapped to existing resources. 130 BIND lets clients associate a new URI with an existing WebDAV 131 resource, and this URI can then be used to submit requests to the 132 resource. Since URIs of WebDAV resources are hierarchical, and 133 correspond to a hierarchy of collections in resource space, the 134 BIND method also has the effect of adding the resource to a 135 collection. As new URIs are associated with the resource, it 136 appears in additional collections. 138 A BIND request does not create a new resource, but simply makes 139 available a new URI for submitting requests to an existing 140 resource. The new URI is indistinguishable from any other URI when 141 submitting a request to a resource. Only one round trip is needed 142 to submit a request to the intended target. Servers are required 143 to enforce the integrity of the relationships between the new URIs 144 and the resources associated with them. Consequently, it may be 145 very costly for servers to support BIND requests that cross server 146 boundaries. 148 This specification is organized as follows. Section 1.1 defines 149 terminology used in the rest of the specification, while Section 2 150 overviews bindings. Section 3 specifies the BIND method, used to 151 create multiple bindings to the same resource. Sections Error! 152 Reference source not found. defines the new properties needed to 153 support multiple bindings to the same resource. 155 1.1 Terminology 157 The terminology used here follows and extends that in the WebDAV 158 Distributed Authoring Protocol specification [RFC2518]. 160 URI Mapping 162 A relation between an absolute URI and a resource. For an absolute 163 URI U and the resource it identifies R, the URI mapping can be 164 thought of as (U => R). Since a resource can represent items that 165 are not network retrievable, as well as those that are, it is 166 possible for a resource to have zero, one, or many URI mappings. 167 Mapping a resource to an "http" scheme URL makes it possible to 168 submit HTTP protocol requests to the resource using the URL. 170 Path Segment 172 Informally, the characters found between slashes ("/") in a URI. 173 Formally, as defined in section 3.3 of [RFC2396]. 175 Binding 177 A relation between a single path segment (in a collection) and a 178 resource. A binding is part of the state of a collection. If two 179 different collections contain a binding between the same path 180 segment and the same resource, these are two distinct bindings. So 181 for a collection C, a path segment S, and a resource R, the binding 182 can be thought of as C:(S -> R). Bindings create URI mappings, and 183 hence allow requests to be sent to a single resource from multiple 184 locations in a URI namespace. For example, given a collection C 185 (accessible through the URI http://www.srv.com/coll/), a path 186 segment S (equal to "foo.html"), and a resource R, then creating 187 the binding C: (S -> R) makes it possible to use the URI 188 http://www.srv.com/coll/foo.html to access R. 190 Collection 192 A resource that contains, as part of its state, a set of bindings 193 that identify internal member resources. 195 Internal Member URI 197 The URI that identifies an internal member of a collection, and 198 that consists of the URI for the collection, followed by a slash 199 character ('/'), followed by the path segment of the binding for 200 that internal member. 202 1.2 Rationale for Distinguishing Bindings from URI Mappings 204 In [RFC2518], the state of a collection is defined as containing a 205 list of internal member URIs. If there are multiple mappings to a 206 collection, then the state of the collection is different when you 207 refer to it via a different URI. This is undesirable, since ideally 208 a collection's membership should remain the same, independent of 209 which URI was used to reference it. 211 The notion of binding is introduced to separate the final segment 212 of a URI from its parent collection�s contribution. This done, a 213 collection can be defined as containing a set of bindings, thus 214 permitting new mappings to a collection without modifying its 215 membership. The authors of this specification anticipate and 216 recommend that future revisions of [RFC2518] will update the 217 definition of the state of a collection to correspond to the 218 definition in this document. 220 2 OVERVIEW OF BINDINGS 222 Bindings are part of the state of a collection. They define the 223 internal members of the collection, and the names of those internal 224 members. 226 Bindings are added and removed by a variety of existing HTTP 227 methods. A method that creates a new resource, such as PUT, COPY, 228 and MKCOL, adds a binding. A method that deletes a resource, such 229 as DELETE, removes a binding. A method that moves a resource (e.g. 230 MOVE) both adds a binding (in the destination collection) and 231 removes a binding (in the source collection). The BIND method 232 introduced here provides a mechanism for adding a second binding to 233 an existing resource. There is no difference between an initial 234 binding added by PUT, COPY, or MKCOL, and additional bindings added 235 with BIND. 237 It would be very undesirable if one binding could be destroyed as a 238 side effect of operating on the resource through a different 239 binding. In particular, the removal of one binding to a resource 240 (e.g. with a DELETE or a MOVE) MUST NOT disrupt another binding to 241 that resource, e.g. by turning that binding into a dangling path 242 segment. The server MUST NOT reclaim system resources after 243 removing one binding, while other bindings to the resource remain. 244 In other words, the server MUST maintain the integrity of a 245 binding. 247 2.1 Bindings to Collections 249 Bindings to collections can result in loops, which servers MUST 250 detect when processing "Depth: infinity" requests. It is sometimes 251 possible to complete an operation in spite of the presence of a 252 loop. However, the 506 (Loop Detected) status code is defined in 253 Section 5 for use in contexts where an operation is terminated 254 because a loop was encountered. Servers MUST allow loops to be 255 created. 257 Creating a new binding to a collection makes each resource 258 associated with a binding in that collection accessible via a new 259 URI, and thus creates new URI mappings to those resources but no 260 new bindings. 262 For example, suppose a new binding CollY is created for collection 263 C1 in the figure below. It immediately becomes possible to access 264 resource R1 using the URI /CollY/x.gif and to access resource R2 265 using the URI /CollY/y.jpg, but no new bindings for these child 266 resources were created. This is because bindings are part of the 267 state of a collection, and associate a URI that is relative to that 268 collection with its target resource. No change to the bindings in 269 Collection C1 is needed to make its children accessible using 270 /CollY/x.gif and /CollY/y.jpg. 272 +-------------------------+ 273 | Root Collection | 274 | (properties) | 275 | bindings: | 276 | CollX CollY | 277 +-------------------------+ 278 | / 279 | / 280 | / 281 +------------------+ 282 | Collection C1 | 283 | (properties) | 284 | bindings: | 285 | x.gif y.jpg | 286 +------------------+ 287 | \ 288 | \ 289 | \ 290 +-------------+ +-------------+ 291 | Resource R1 | | Resource R2 | 292 +-------------+ +-------------+ 294 2.2 URI Mappings Created by a new Binding 296 Suppose a binding from "Binding-Name" to resource R to be added to 297 a collection, C. Then if C-MAP is the set of URI's that were 298 mapped to C before the BIND request, then for each URI "C-URI" in 299 C-MAP, the URI "C-URI/Binding-Name" is mapped to resource R 300 following the BIND request. 302 For example, if a binding from "foo.html" to R is added to a 303 collection C, and if the following URI's are mapped to C: 305 http://www.fuzz.com/A/1/ 306 http://fuzz.com/A/one/ 308 then the following new mappings to R are introduced: 310 http://www.fuzz.com/A/1/foo.html 311 http://fuzz.com/A/one/foo.html 313 Note that if R is a collection, additional URI mappings are created 314 to the descendents of R. Also, note that if a binding is made in 315 collection C to C itself (or to a parent of C), an infinite number 316 of mappings are introduced. 318 For example, if a binding from "myself" to C is then added to C, 319 the following infinite number of additional mappings to C are 320 introduced: 322 http://www.fuzz.com/A/1/myself 323 http://www.fuzz.com/A/1/myself/myself 324 ... 326 and the following infinite number of additional mappings to R are 327 introduced: 329 http://www.fuzz.com/A/1/myself/foo.html 330 http://www.fuzz.com/A/1/myself/myself/foo.html 331 ... 333 2.3 DELETE and Bindings 335 The DELETE method was originally defined in [RFC2616]. This section 336 redefines the behavior of DELETE in terms of bindings, an 337 abstraction not available when writing [RFC2616]. [RFC2616] states 338 that "the DELETE method requests that the origin server delete the 339 resource identified by the Request-URI." Because [RFC2616] did not 340 distinguish between bindings and resources, the intent of its 341 definition of DELETE is unclear. The definition presented here is 342 a clarification of the definition in [RFC2616]. 344 The DELETE method requests that the server remove the binding 345 between the resource identified by the Request-URI and the binding 346 name, the last path segment of the Request-URI. The binding MUST be 347 removed from its parent collection, identified by the Request-URI 348 minus its trailing slash (if present) and final segment. 350 Once a resource is unreachable by any URI mapping, the server MAY 351 reclaim system resources associated with that resource. If DELETE 352 removes a binding to a resource, but there remain URI mappings to 353 that resource, the server MUST NOT reclaim system resources 354 associated with the resource. 356 Although [RFC2518] allows a DELETE to be a non-atomic operation, 357 the DELETE operation defined here is atomic. In particular, a 358 DELETE on a hierarchy of resources is simply the removal of a 359 binding to the collection identified by the Request-URI, and so is 360 a single (and therefore atomic) operation. 362 Section 8.6.1 of [RFC2518] states that during DELETE processing, a 363 server "MUST remove any URI for the resource identified by the 364 Request-URI from collections which contain it as a member." 365 Servers that support bindings MUST NOT follow this requirement. 367 2.4 COPY and Bindings 369 As defined in Section 8.8 of [RFC2518], COPY causes the resource 370 identified by the Request-URI to be duplicated, and makes the new 371 resource accessible using the URI specified in the Destination 372 header. Upon successful completion of a COPY, a new binding is 373 created between the last path segment of the Destination header, 374 and the destination resource. The new binding is added to its 375 parent collection, identified by the Destination header minus its 376 trailing slash (if present) and final segment. 378 The following figure shows an example: Suppose that a COPY is 379 issued to URI 3 for resource R (which is also mapped to URI 1 and 380 URI 2), with the Destination header set to URIX. After successful 381 completion of the COPY operation, resource R is duplicated to 382 create resource R', and a new binding has been created which 383 creates at least the URI mapping between URIX and the new resource 384 (although other URI mappings may also have been created). 386 URI 1 URI 2 URI 3 URIX 387 | | | | 388 | | | <---- URI Mappings ----> | 389 | | | | 390 +---------------------+ +------------------------+ 391 | Resource R | | Resource R' | 392 +---------------------+ +------------------------+ 394 It might be thought that a COPY request with "Depth: 0" on a 395 collection would duplicate its bindings, since bindings are part of 396 the collection's state. This is not the case, however. The 397 definition of Depth in [RFC2518] makes it clear that a "Depth: 0" 398 request does not apply to a collection's members. Consequently, a 399 COPY with "Depth: 0" does not duplicate the bindings contained by 400 the collection. 402 2.5 MOVE and Bindings 404 The MOVE method has the effect of creating a new binding to a 405 resource (at the Destination), and removing an existing binding (at 406 the Request-URI). The name of the new binding is the last path 407 segment of the Destination header, and the new binding is added to 408 its parent collection, identified by the Destination header minus 409 its trailing slash (if present) and final segment. 411 As an example, suppose that a MOVE is issued to URI 3 for resource 412 R below (which is also mapped to URI 1 and URI 2), with the 413 Destination header set to URIX. After successful completion of the 414 MOVE operation, a new binding has been created which creates at 415 least the URI mapping between URIX and resource R (although other 416 URI mappings may also have been created). The binding 417 corresponding to the final segment of URI 3 has been removed, which 418 also causes the URI mapping between URI 3 and R to be removed. 420 >> Before Request: 422 URI 1 URI 2 URI 3 423 | | | 424 | | | <---- URI Mappings 425 | | | 426 +---------------------+ 427 | Resource R | 428 +---------------------+ 430 >> After Request: 432 URI 1 URI 2 URIX 433 | | | 434 | | | <---- URI Mappings 435 | | | 436 +---------------------+ 437 | Resource R | 438 +---------------------+ 440 Although [RFC2518] allows a MOVE on a collection to be a non-atomic 441 operation, the MOVE operation defined here MUST be atomic. Even 442 when the Request-URI identifies a collection, the MOVE operation 443 involves only removing one binding to that collection and adding 444 another. There are no operations on bindings to any of its 445 children, so the case of MOVE on a collection is the same as the 446 case of MOVE on a non-collection resource. Both are atomic. 448 2.6 Determining Whether Two Bindings Are to the Same Resource 450 It is useful to have some way of determining whether two bindings 451 are to the same resource. Two resources might have identical 452 contents and properties, but not be the same resource (e.g. an 453 update to one resource does not affect the other resource). 455 The REQUIRED DAV:resource-id property defined in Section 3.1 is a 456 resource identifier, which MUST be unique across all resources for 457 all time. If the values of DAV:resource-id returned by PROPFIND 458 requests through two bindings are identical, the client can be 459 assured that the two bindings are to the same resource. 461 The DAV:resource-id property is created, and its value assigned, 462 when the resource is created. The value of DAV:resource-id MUST 463 NOT be changed. Even after the resource is no longer accessible 464 through any URI, that value MUST NOT be reassigned to another 465 resource's DAV:resource-id property. 467 Any method that creates a new resource MUST assign a new, unique 468 value to its DAV:resource-id property. For example, a PUT that 469 creates a new resource must assign a new, unique value to its 470 DAV:resource-id property. A COPY, since it creates a new resource 471 at the Destination URI, must assign a new, unique value to its 472 DAV:resource-id property. 474 On the other hand, any method that affects an existing resource 475 MUST NOT change the value of its DAV:resource-id property. For 476 example, a PUT that updates an existing resource must not change 477 the value of its DAV:resource-id property. A MOVE, since it does 478 not create a new resource, but only changes the location of an 479 existing resource, must not change the value of its DAV:resource-id 480 property. 482 2.7 Discovering the Bindings to a Resource 484 An OPTIONAL DAV:parent-set property on a resource provides a list 485 of the bindings that associate a collection and a URI segment with 486 that resource. If the DAV:parent-set property exists on a given 487 resource, it MUST contain a complete list of all bindings to that 488 resource that the client is authorized to see. When deciding 489 whether to support the DAV:parent-set property, server implementers 490 / administrators should balance the benefits it provides against 491 the cost of maintaining the property and the security risks 492 enumerated in Sections 6.4 and 6.5. 494 3 PROPERTIES 496 The bind feature introduces the following properties for a 497 resource. 499 3.1 DAV:resource-id Property 501 The DAV:resource-id property is a REQUIRED property that enables 502 clients to determine whether two bindings are to the same resource. 503 The value of DAV:resource-id is a URI, and may use any registered 504 URI scheme that guarantees the uniqueness of the value across all 505 resources for all time (e.g. the opaquelocktoken: scheme defined in 506 [RFC2518]). 508 510 3.2 DAV:parent-set Property 512 The DAV:parent-set property is an OPTIONAL property that enables 513 clients to discover what collections contain a binding to this 514 resource (i.e. what collections have that resource as an internal 515 member). It contains an of href/segment pair for each collection 516 that has a binding to the resource. The href identifies the 517 collection, and the segment identifies the binding name of that 518 resource in that collection. 520 A given collection MUST appear only once in the DAV:parent-set for 521 any given binding, even if there are multiple URI mappings to that 522 collection. For example, if collection C1 is mapped to both /CollX 523 and /CollY, and C1 contains a binding named "x.gif" to a resource 524 R1, then either [/CollX, x.gif] or [/CollY, y.gif] can appear in 525 the DAV:parent-set of R1, but not both. But if C1 also had a 526 binding named "y.gif" to R1, then there would be two entries for C1 527 in the DAV:binding-set of R1 (i.e. either both [/CollX, x.gif] and 528 [/CollX, y.gif] or alternatively, both [/CollY, x.gif] and [/CollY, 529 y.gif]). 531 532 533 534 PCDATA value: segment, as defined in section 3.3 of [RFC2396] 536 4 BIND METHOD 538 The BIND method modifies the collection identified by the Request- 539 URI, by adding a new binding from the segment specified in the BIND 540 body to the resource identified in the BIND body. 542 If a server cannot guarantee the integrity of the binding, the BIND 543 request MUST fail. Note that it is especially difficult to 544 maintain the integrity of cross-server bindings. Unless the server 545 where the resource resides knows about all bindings on all servers 546 to that resource, it may unwittingly destroy the resource or make 547 it inaccessible without notifying another server that manages a 548 binding to the resource. For example, if server A permits creation 549 of a binding to a resource on server B, server A must notify server 550 B about its binding and must have an agreement with B that B will 551 not destroy the resource while A's binding exists. Otherwise 552 server B may receive a DELETE request that it thinks removes the 553 last binding to the resource and destroy the resource while A's 554 binding still exists. Status code 507 (Cross-server Binding 555 Forbidden) is defined in Section 5.1 for cases where servers fail 556 cross-server BIND requests because they cannot guarantee the 557 integrity of cross-server bindings. 559 By default, if there already is a binding for the specified segment 560 in the collection, the new binding replaces the existing binding. 561 This default binding replacement behavior can be overridden using 562 the Overwrite header defined in Section 9.6 of [RFC2518]. 564 Marshalling: 566 The request MAY include an Overwrite header. 568 The request body MUST be a DAV:bind XML element. 570 571 573 If a response body for a successful request is included, it MUST be 574 a DAV:bind-response XML element. Note that this document does not 575 define any elements for the BIND response body, but the DAV:bind- 576 response element is defined to ensure interoperability between 577 future extensions that do define elements for the BIND response 578 body. 580 581 Preconditions: 583 (DAV:bind-into-collection): The Request-URL MUST identify a 584 collection. 586 (DAV:cross-server-binding): If the resource identified by the 587 DAV:href element in the request body is on another server from the 588 collection identified by the request-URL, the server MUST support 589 cross-server bindings. 591 (DAV:can-overwrite): If the collection already contains a binding 592 with the specified path segment, and if an Overwrite header is 593 included, the value of the Overwrite header MUST be "T". 595 Postconditions: 597 (DAV:new-binding): The collection MUST have a binding that maps the 598 segment specified in the DAV:segment element in the request body, 599 to the resource identified by the DAV:href element in the request 600 body. 602 4.1 Example: BIND 604 >> Request: 606 BIND /coll HTTP/1.1 607 Host: www.somehost.com 608 Content-Type: text/xml; charset="utf-8" 609 Content-Length: xxx 611 612 613 bar.html 614 http://www.somehost.com/coll 615 617 >> Response: 619 HTTP/1.1 201 Created 621 The server added a new binding to the collection, 622 "http://www.somehost.com/coll", associating "bar.html" with the 623 resource identified by the URL 624 "http://www.somehost.com/coll/foo.html". Clients can now use the 625 URL "http://www.somehost.com/coll/bar.html", to submit requests to 626 that resource. 628 5 ADDITIONAL STATUS CODES 630 5.1 506 Loop Detected 632 The 506 (Loop Detected) status code indicates that the server 633 terminated an operation because it encountered an infinite loop 634 while processing a request with "Depth: infinity". 636 When this status code is the top-level status code for the 637 operation, it indicates that the entire operation failed. 639 When this status code occurs inside a multi-status response, it 640 indicates only that a loop is being terminated, but does not 641 indicate failure of the operation as a whole. 643 For example, consider a PROPFIND request on /Coll (bound to 644 collection C), where the members of /Coll are /Coll/Foo (bound to 645 resource R) and /Coll/Bar (bound to collection C). 647 >> Request: 649 PROPFIND /Coll/ HTTP/1.1 650 Host: www.somehost.com 651 Depth: infinity 652 Content-Type: text/xml; charset="utf-8" 653 Content-Length: xxx 655 656 657 658 660 >> Response: 662 HTTP/1.1 207 Multi-Status 663 Content-Type: text/xml; charset="utf-8" 664 Content-Length: xxx 666 667 668 669 http://www.somehost.com/Coll/ 670 671 672 Loop Demo 673 674 HTTP/1.1 200 OK 675 676 677 678 http://www.somehost.com/Coll/Foo 679 680 681 Bird Inventory 682 683 HTTP/1.1 200 OK 684 685 686 687 http://www.somehost.com/Coll/Bar 688 HTTP/1.1 506 Loop Detected 689 690 692 6 SECURITY CONSIDERATIONS 694 This section is provided to make WebDAV applications aware of the 695 security implications of this protocol. 697 All of the security considerations of HTTP/1.1 and the WebDAV 698 Distributed Authoring Protocol specification also apply to this 699 protocol specification. In addition, bindings introduce several 700 new security concerns and increase the risk of some existing 701 threats. These issues are detailed below. 703 6.1 Privacy Concerns 705 In a context where cross-server bindings are supported, creating 706 bindings on a trusted server may make it possible for a hostile 707 agent to induce users to send private information to a target on a 708 different server. 710 6.2 Redirect Loops 712 Although redirect loops were already possible in HTTP 1.1, the 713 introduction of the BIND method creates a new avenue for clients to 714 create loops accidentally or maliciously. If the binding and its 715 target are on the same server, the server may be able to detect 716 BIND requests that would create loops. Servers are required to 717 detect loops that are caused by bindings to collections during the 718 processing of any requests with "Depth: infinity". 720 6.3 Bindings, and Denial of Service 722 Denial of service attacks were already possible by posting URLs 723 that were intended for limited use at heavily used Web sites. The 724 introduction of BIND creates a new avenue for similar denial of 725 service attacks. If cross-server bindings are supported, clients 726 can now create bindings at heavily used sites to target locations 727 that were not designed for heavy usage. 729 6.4 Private Locations May Be Revealed 731 If the DAV:parent-set property is maintained on a resource, the 732 owners of the bindings risk revealing private locations. The 733 directory structures where bindings are located are available to 734 anyone who has access to the DAV:parent-set property on the 735 resource. Moving a binding may reveal its new location to anyone 736 with access to DAV:parent-set on its resource. 738 6.5 DAV:parent-set and Denial of Service 740 If the server maintains the DAV:parent-set property in response to 741 bindings created in other administrative domains, it is exposed to 742 hostile attempts to make it devote resources to adding bindings to 743 the list. 745 7 INTERNATIONALIZATION CONSIDERATIONS 747 All internationalization considerations mentioned in [RFC2518] also 748 apply to this document. 750 8 IANA CONSIDERATIONS 752 All IANA considerations mentioned in [RFC2518] also apply to this 753 document. 755 9 INTELLECTUAL PROPERTY 757 The following notice is copied from RFC 2026, Section 10.4, and 758 describes the position of the IETF concerning intellectual property 759 claims made against this document. 761 The IETF takes no position regarding the validity or scope of any 762 intellectual property or other rights that might be claimed to 763 pertain to the implementation or use other technology described in 764 this document or the extent to which any license under such rights 765 might or might not be available; neither does it represent that it 766 has made any effort to identify any such rights. Information on 767 the procedures of the IETF with respect to rights in standards- 768 track and standards-related documentation can be found in BCP-11. 769 Copies of claims of rights made available for publication and any 770 assurances of licenses to be made available, or the result of an 771 attempt made to obtain a general license or permission for the use 772 of such proprietary rights by implementers or users of this 773 specification can be obtained from the IETF Secretariat. 775 The IETF invites any interested party to bring to its attention any 776 copyrights, patents or patent applications, or other proprietary 777 rights that may cover technology that may be required to practice 778 this standard. Please address the information to the IETF 779 Executive Director. 781 10 ACKNOWLEDGEMENTS 783 This draft is the collaborative product of the authors and Tyson 784 Chihaya, Jim Davis, and Chuck Fay. This draft has benefited from 785 thoughtful discussion by Jim Amsden, Peter Carlson, Steve Carter, 786 Ken Coar, Ellis Cohen, Dan Connolly, Bruce Cragun, Spencer Dawkins, 787 Mark Day, Rajiv Dulepet, David Durand, Roy Fielding, Yaron Goland, 788 Fred Hitt, Alex Hopmann, James Hunt, Marcus Jager, Chris Kaler, 789 Manoj Kasichainula, Rohit Khare, Daniel LaLiberte, Steve Martin, 790 Larry Masinter, Jeff McAffer, Surendra Koduru Reddy, Max Rible, Sam 791 Ruby, Bradley Sergeant, Nick Shelness, John Stracke, John Tigue, 792 John Turner, Kevin Wiggen, and other members of the WebDAV working 793 group. 795 11 REFERENCES 797 [RFC2026] S.Bradner, "The Internet Standards Process", RFC 2026, 798 October 1996. 800 [RFC2119] S.Bradner, "Key words for use in RFCs to Indicate 801 Requirement Levels", RFC 2119, March 1997. 803 [RFC2277] H.Alvestrand, "IETF Policy on Character Sets and 804 Languages." RFC 2277, January 1998. 806 [RFC2396] T. Berners-Lee, R. Fielding, L. Masinter, "Uniform 807 Resource Identifiers (URI): Generic Syntax." RFC 2396, August 1998. 809 [RFC2518] Y.Goland, E.Whitehead, A.Faizi, S.R.Carter, D.Jensen, 810 "HTTP Extensions for Distributed Authoring - WEBDAV", RFC 2518, 811 February 1999. 813 [RFC2616] R.Fielding, J.Gettys, J.C.Mogul, H.Frystyk, L.Masinter, 814 P.Leach, and T.Berners-Lee, "Hypertext Transfer Protocol -- 815 HTTP/1.1", RFC 2616, June 1999. 817 [XML] T. Bray, J. Paoli, C.M. Sperberg-McQueen, "Extensible Markup 818 Language (XML)." World Wide Web Consortium Recommendation REC-xml- 819 19980210. http://www.w3.org/TR/1998/REC-xml-19980210. 821 12 AUTHORS' ADDRESSES 823 Geoffrey Clemm 824 Rational Software Corporation 825 20 Maguire Road 826 Lexington, MA 02173-3104 827 Email: geoffrey.clemm@rational.com 829 Jason Crawford 830 IBM Research 831 P.O. Box 704 832 Yorktown Heights, NY 10598 833 Email: ccjason@us.ibm.com 835 Julian F. Reschke 836 greenbytes GmbH 837 Salzmannstrasse 152 838 Muenster, NW 48159, Germany 839 Email: julian.reschke@greenbytes.de 841 Judy Slein 842 Xerox Corporation 843 800 Phillips Road, 105-50C 844 Webster, NY 14580 845 Email: jslein@crt.xerox.com 847 Jim Whitehead 848 UC Santa Cruz, Dept. of Computer Science 849 1156 High Street, Santa Cruz, CA 95064 850 Email: ejw@cse.ucsc.edu