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--------------------------------------------------------------------------------
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