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