|WebDAV Working Group||L. Dusseault, Editor|
|Obsoletes: 2518 (if approved)||February 5, 2006|
|Intended status: Standards Track|
|Expires: August 9, 2006|
HTTP Extensions for Distributed Authoring - WebDAV
Note: a later version of this document has been published as RFC4918.
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Copyright © The Internet Society (2006). All Rights Reserved.
WebDAV consists of a set of methods, headers, and content-types ancillary to HTTP/1.1 for the management of resource properties, creation and management of resource collections, URL namespace manipulation, and resource locking (collision avoidance).
RFC2518 was published in February 1999, and this specification makes minor revisions mostly due to interoperability experience.
This document describes an extension to the HTTP/1.1 protocol that allows clients to perform remote web content authoring operations. This extension provides a coherent set of methods, headers, request entity body formats, and response entity body formats that provide operations for:
Properties: The ability to create, remove, and query information about Web pages, such as their authors, creation dates, etc. Also, the ability to link pages of any media type to related pages.
Collections: The ability to create sets of documents and to retrieve a hierarchical membership listing (like a directory listing in a file system).
Locking: The ability to keep more than one person from working on a document at the same time. This prevents the "lost update problem", in which modifications are lost as first one author then another writes changes without merging the other author's changes.
Namespace Operations: The ability to instruct the server to copy and move Web resources, operations which change the URL.
Requirements and rationale for these operations are described in a companion document, "Requirements for a Distributed Authoring and Versioning Protocol for the World Wide Web" [RFC2291].
The sections below provide a detailed introduction to various WebDAV abstractions: resource properties (Section 4), collections of resources (Section 5), locks (Section 6) in general and write locks (Section 7) specifically.
While the status codes provided by HTTP/1.1 are sufficient to describe most error conditions encountered by WebDAV methods, there are some errors that do not fall neatly into the existing categories. This specification defines new status codes developed for WebDAV methods (Section 11) and describes existing HTTP status codes (Section 12) as used in WebDAV. Since some WebDAV methods may operate over many resources, the Multi-Status response (Section 13) has been introduced to return status information for multiple resources. Finally, this version of WebDAV introduces precondition and postcondition (Section 16) XML elements in error response bodies.
WebDAV uses [XML] for property names and some values, and also uses XML to marshal complicated request and response. This specification contains DTD and text definitions of all all properties (Section 15) and all other XML elements (Section 14) used in marshalling. WebDAV includes a few special rules on extending (Section 17) WebDAV XML marshalling in backwards-compatible ways.
Finishing off the specification are sections on what it means for a resource to be compliant with this specification (Section 18), on internationalization support (Section 19), and on security (Section 20).
Since this document describes a set of extensions to the HTTP/1.1 protocol, the augmented BNF used herein to describe protocol elements is exactly the same as described in section 2.1 of [RFC2616], including the rules about implied linear white-space. Since this augmented BNF uses the basic production rules provided in section 2.2 of [RFC2616], these rules apply to this document as well.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
Note that in natural language, a property like the "creationdate" property in the "DAV:" XML namespace is sometimes referred to as "DAV:creationdate" for brevity.
URI/URL - A Uniform Resource Identifier and Uniform Resource Locator, respectively. These terms (and the distinction between them) are defined in [RFC3986].
URI/URL Mapping - A relation between an absolute URI and a resource. Since a resource can represent items that are not network retrievable, as well as those that are, it is possible for a resource to have zero, one, or many URI mappings. Mapping a resource to an "http" scheme URI makes it possible to submit HTTP protocol requests to the resource using the URI.
Collection - A resource that contains a set of URLs, which identify and locate member resources and which meet the collections requirements (Section 5).
Member URL - A URL which is a member of the set of URLs contained by a collection.
Path Segment - Informally, the characters found between slashes ("/") in a URI. Formally, as defined in Section 3.3 of [RFC3986].
Internal Member URL - A member URL that is immediately relative to the URL of the collection. That is, the internal member URL is equal to a containing collection's URL plus an additional path segment for non-collection resources, or additional segment plus trailing slash "/" for collection resources.
Property - A name/value pair that contains descriptive information about a resource.
Live Property - A property whose semantics and syntax are enforced by the server. For example, the live property DAV:getcontentlength has its value, the length of the entity returned by a GET request, automatically calculated by the server.
Dead Property - A property whose semantics and syntax are not enforced by the server. The server only records the value of a dead property; the client is responsible for maintaining the consistency of the syntax and semantics of a dead property.
Principal - A "principal" is a distinct human or computational actor that initiates access to network resources.
Properties are pieces of data that describe the state of a resource. Properties are data about data.
Properties are used in distributed authoring environments to provide for efficient discovery and management of resources. For example, a 'subject' property might allow for the indexing of all resources by their subject, and an 'author' property might allow for the discovery of what authors have written which documents.
The DAV property model consists of name/value pairs. The name of a property identifies the property's syntax and semantics, and provides an address by which to refer to its syntax and semantics.
There are two categories of properties: "live" and "dead". A live property has its syntax and semantics enforced by the server. Live properties include cases where a) the value of a property is read-only, maintained by the server, and b) the value of the property is maintained by the client, but the server performs syntax checking on submitted values. All instances of a given live property MUST comply with the definition associated with that property name. A dead property has its syntax and semantics enforced by the client; the server merely records the value of the property verbatim.
Properties already exist, in a limited sense, in HTTP message headers. However, in distributed authoring environments a relatively large number of properties are needed to describe the state of a resource, and setting/returning them all through HTTP headers is inefficient. Thus a mechanism is needed which allows a principal to identify a set of properties in which the principal is interested and to set or retrieve just those properties.
The value of a property is always a (well-formed) XML fragment.
XML has been chosen because it is a flexible, self-describing, structured data format that supports rich schema definitions, and because of its support for multiple character sets. XML's self-describing nature allows any property's value to be extended by adding new elements. Older clients will not break when they encounter extensions because they will still have the data specified in the original schema and MUST ignore elements they do not understand.
XML's support for multiple character sets allows any human-readable property to be encoded and read in a character set familiar to the user. XML's support for multiple human languages, using the "xml:lang" attribute, handles cases where the same character set is employed by multiple human languages. Note that xml:lang scope is recursive, so a xml:lang attribute on any element containing a property name element applies to the property value unless it has been overridden by a more locally scoped attribute. Note that a property only has one value, in one language (or language MAY be left undefined), not multiple values in different languages or a single value in multiple languages.
A property is always represented with an XML element consisting of the property name, called the "property name element". The simplest example is an empty property, which is different from a property that does not exist:
The value of the property appears inside the property name element. The value may be any kind of well-formed XML content, including both text-only and mixed content. Servers MUST preserve the following XML Information Items (using the terminology from [W3C.REC-xml-infoset-20040204]) in storage and transmission of dead properties:
For the property name Element Information Item itself:
On all Element Information Items in the property value:
On Attribute Information Items in the property value:
On Character Information Items in the property value:
Since prefixes are used in some XML vocabularies (XPath and XML Schema, for example), servers SHOULD preserve, for any Information Item in the value:
XML Infoset attributes not listed above MAY be preserved by the server, but clients MUST NOT rely on them being preserved. The above rules would also apply by default to live properties, unless defined otherwise.
Servers MUST ignore the XML attribute xml:space if present and never use it to change white space handling. White space in property values is significant.
Consider a dead property 'author' created by the client as follows:
<D:prop xml:lang="en" xmlns:D="DAV:"> <x:author xmlns:x='http://example.com/ns'> <x:name>Jane Doe</x:name> <!-- Jane's contact info --> <x:uri type='email' added='2005-11-26'>mailto:email@example.com</x:uri> <x:uri type='web' added='2005-11-27'>http://www.example.com</x:uri> <x:notes xmlns:h='http://www.w3.org/1999/xhtml'> Jane has been working way <h:em>too</h:em> long on the long-awaited revision of <![CDATA[<RFC2518>]]>. </x:notes> </x:author> </D:prop>
When this property is requested, a server might return:
<D:prop xmlns:D='DAV:'><author xml:lang='en' xmlns:x='http://example.com/ns' xmlns='http://example.com/ns' xmlns:h='http://www.w3.org/1999/xhtml'> <x:name>Jane Doe</x:name> <x:uri added="2005-11-26" type="email" >mailto:firstname.lastname@example.org</x:uri> <x:uri added="2005-11-27" type="web" >http://www.example.com</x:uri> <x:notes> Jane has been working way <h:em>too</h:em> long on the long-awaited revision of <RFC2518>. </x:notes> </author> </D:prop>
Note in this example:
Implementation note: there are cases such as editing scenarios where clients may require that XML content is preserved character-by-character (such as attribute ordering or quoting style). In this case, clients should consider using a text-only property value by escaping all characters that have a special meaning in XML parsing.
A property name is a universally unique identifier that is associated with a schema that provides information about the syntax and semantics of the property.
Because a property's name is universally unique, clients can depend upon consistent behavior for a particular property across multiple resources, on the same and across different servers, so long as that property is "live" on the resources in question, and the implementation of the live property is faithful to its definition.
The XML namespace mechanism, which is based on URIs ([RFC3986]), is used to name properties because it prevents namespace collisions and provides for varying degrees of administrative control.
The property namespace is flat; that is, no hierarchy of properties is explicitly recognized. Thus, if a property A and a property A/B exist on a resource, there is no recognition of any relationship between the two properties. It is expected that a separate specification will eventually be produced which will address issues relating to hierarchical properties.
Finally, it is not possible to define the same property twice on a single resource, as this would cause a collision in the resource's property namespace.
Some HTTP resources are dynamically generated by the server. For these resources, there presumably exists source code somewhere governing how that resource is generated. The relationship of source files to output HTTP resources may be one to one, one to many, many to one or many to many. There is no mechanism in HTTP to determine whether a resource is even dynamic, let alone where its source files exist or how to author them. Although this problem would usefully be solved, interoperable WebDAV implementations have been widely deployed without actually solving this problem, by dealing only with static resources. Thus, the source vs. output problem is not solved in this specification and has been deferred to a separate document.
This section provides a description of a new type of Web resource, the collection, and discusses its interactions with the HTTP URL namespace. The purpose of a collection resource is to model collection-like objects (e.g., file system directories) within a server's namespace.
All DAV compliant resources MUST support the HTTP URL namespace model specified herein.
The HTTP URL namespace is a hierarchical namespace where the hierarchy is delimited with the "/" character.
An HTTP URL namespace is said to be consistent if it meets the following conditions: for every URL in the HTTP hierarchy there exists a collection that contains that URL as an internal member. The root, or top-level collection of the namespace under consideration is exempt from the previous rule. The top-level collection of the namespace under consideration is not necessarily the collection identified by the absolute path '/', it may be identified by one or more path segments (e.g. /servlets/webdav/...)
Neither HTTP/1.1 nor WebDAV require that the entire HTTP URL namespace be consistent -- a WebDAV-compatible resource may not have a parent collection. However, certain WebDAV methods are prohibited from producing results that cause namespace inconsistencies.
Collection resources differ from other resources in that they also act as containers. A collection is a resource whose state consists of at least a set of mappings between path segments and resources, and a set of properties on the collection itself. A collection MAY have additional state such as entity bodies returned by GET.
Any given internal member URL MUST only belong to the collection once, i.e., it is illegal to have multiple instances of the same URL in a collection. Properties defined on collections behave exactly as do properties on non-collection resources.
For all WebDAV compliant resources A and B, identified by URLs U and V, for which U is immediately relative to V, B MUST be a collection that has U as an internal member URL. So, if the resource with URL http://example.com/bar/blah is WebDAV compliant and if the resource with URL http://example.com/bar/ is WebDAV compliant then the resource with URL http://example.com/bar/ must be a collection and must contain URL http://example.com/bar/blah as an internal member.
Collection resources MAY list the URLs of non-WebDAV compliant children in the HTTP URL namespace hierarchy as internal members but are not required to do so. For example, if the resource with URL http://example.com/bar/blah is not WebDAV compliant and the URL http://example.com/bar/ identifies a collection then URL http://example.com/bar/blah may or may not be an internal member of the collection with URL http://example.com/bar/.
If a WebDAV compliant resource has no WebDAV compliant children in the HTTP URL namespace hierarchy then the WebDAV compliant resource is not required to be a collection.
There is a standing convention that when a collection is referred to by its name without a trailing slash, the server MAY handle the request as if the trailing slash were present. In this case it SHOULD return a Content-Location header in the response, pointing to the URL ending with the "/". For example, if a client invokes a method on http://example.com/blah (no trailing slash), the server may respond as if the operation were invoked on http://example.com/blah/ (trailing slash), and should return a Content-Location header with the value http://example.com/blah/. Wherever a server produces a URL referring to a collection, the server SHOULD include the trailing slash. In general clients SHOULD use the trailing slash form of collection names. If clients do not use the trailing slash form the client needs to be prepared to see a redirect response. Clients will find the DAV:resourcetype property more reliable than the URL to find out if a resource is a collection.
Clients MUST be able to support the case where WebDAV resources are contained inside non-WebDAV resources. For example, if a OPTIONS response from "http://example.com/servlet/dav/collection" indicates WebDAV support, the client cannot assume that "http://example.com/servlet/dav/" or its parent necessarily are WebDAV collections.
The ability to lock a resource provides a mechanism for serializing access to that resource. Using a lock, an authoring client can provide a reasonable guarantee that another principal will not modify a resource while it is being edited. In this way, a client can prevent the "lost update" problem.
This specification allows locks to vary over two client-specified parameters, the number of principals involved (exclusive vs. shared) and the type of access to be granted. This document defines locking for only one access type, write. However, the syntax is extensible, and permits the eventual specification of locking for other access types.
This section provides a concise model for how locking behaves. Later sections will provide more detail on some of the concepts and refer back to these model statements. Normative statements related to LOCK and UNLOCK handling can be found in the sections on those methods, whereas normative statements that cover any method are gathered here.
The most basic form of lock is an exclusive lock. Exclusive locks avoid having to deal with content change conflicts, without requiring any coordination other than the methods described in this specification.
However, there are times when the goal of a lock is not to exclude others from exercising an access right but rather to provide a mechanism for principals to indicate that they intend to exercise their access rights. Shared locks are provided for this case. A shared lock allows multiple principals to receive a lock. Hence any principal with appropriate access can use the lock.
With shared locks there are two trust sets that affect a resource. The first trust set is created by access permissions. Principals who are trusted, for example, may have permission to write to the resource. Among those who have access permission to write to the resource, the set of principals who have taken out a shared lock also must trust each other, creating a (typically) smaller trust set within the access permission write set.
Starting with every possible principal on the Internet, in most situations the vast majority of these principals will not have write access to a given resource. Of the small number who do have write access, some principals may decide to guarantee their edits are free from overwrite conflicts by using exclusive write locks. Others may decide they trust their collaborators will not overwrite their work (the potential set of collaborators being the set of principals who have write permission) and use a shared lock, which informs their collaborators that a principal may be working on the resource.
The WebDAV extensions to HTTP do not need to provide all of the communications paths necessary for principals to coordinate their activities. When using shared locks, principals may use any out of band communication channel to coordinate their work (e.g., face-to-face interaction, written notes, post-it notes on the screen, telephone conversation, Email, etc.) The intent of a shared lock is to let collaborators know who else may be working on a resource.
Shared locks are included because experience from web distributed authoring systems has indicated that exclusive locks are often too rigid. An exclusive lock is used to enforce a particular editing process: take out an exclusive lock, read the resource, perform edits, write the resource, release the lock. This editing process has the problem that locks are not always properly released, for example when a program crashes, or when a lock creator leaves without unlocking a resource. While both timeouts (Section 6.6) and administrative action can be used to remove an offending lock, neither mechanism may be available when needed; the timeout may be long or the administrator may not be available.
A successful request for a new shared lock MUST result in the generation of a unique lock token associated with the requesting principal. Thus if five principals have taken out shared write locks on the same resource there will be five locks and five lock tokens, one for each principal.
A WebDAV compliant resource is not required to support locking in any form. If the resource does support locking it may choose to support any combination of exclusive and shared locks for any access types.
The reason for this flexibility is that locking policy strikes to the very heart of the resource management and versioning systems employed by various storage repositories. These repositories require control over what sort of locking will be made available. For example, some repositories only support shared write locks while others only provide support for exclusive write locks while yet others use no locking at all. As each system is sufficiently different to merit exclusion of certain locking features, this specification leaves locking as the sole axis of negotiation within WebDAV.
The creator of a lock has special privileges to use the locked resource. The server MUST restrict the usage of a lock token to the creator of the lock, both for shared and exclusive locks. For multi-user shared lock cases, each authenticated principal MUST obtain its own shared lock.
The server MAY allow privileged users other than the lock creator to destroy a lock (for example, the resource owner or an administrator) as a special case of lock usage.
If an anonymous user requests a lock, the server MAY refuse the request.
A lock token is a type of state token, represented as a URI, which identifies a particular lock. Each lock has exactly one unique lock token generated by the server. Clients MUST NOT attempt to interpret lock tokens in any way.
Lock token URIs MUST be unique across all resources for all time. This uniqueness constraint allows lock tokens to be submitted across resources and servers without fear of confusion. Since lock tokens are unique, a client MAY submit a lock token in an If header on a resource other than the one that returned it.
When a LOCK operation creates a new lock, the new lock token is returned in the Lock-Token response header defined in Section 10.5, and also in the body of the response.
Submitting a lock token does not confer full privilege to use the lock token or modify the locked resource. Write access and other privileges MUST be enforced through normal privilege or authentication mechanisms, not based on the possible obscurity of lock token values.
Servers MAY make lock tokens publicly readable (e.g. in the DAV:lockdiscovery property). One use case for making lock tokens readable is so that a long-lived lock can be removed by the resource owner (the client that obtained the lock might have crashed or disconnected before cleaning up the lock). Except for the case of using UNLOCK under user guidance, a client SHOULD NOT use a lock tokens created by another client instance.
This specification encourages servers to create UUIDs for lock tokens, and to use the URI form defined by "A Universally Unique Identifier (UUID) URN Namespace" ([RFC4122]). However servers are free to use any URI (e.g. from another scheme) so long as it meets the uniqueness requirements. For example, a valid lock token might be constructed using the "opaquelocktoken" scheme defined in Appendix C.
A lock MAY have a limited lifetime. The lifetime is suggested by the client when creating or refreshing the lock, but the server ultimately chooses the timeout value. Servers MUST remove locks reasonably soon after the timeout expires if the lock is not refreshed and given a new timeout.
Clients MUST assume that locks may arbitrarily disappear at any time, regardless of the value given in the Timeout header. The Timeout header only indicates the behavior of the server if extraordinary circumstances do not occur. For example, a sufficiently privileged user may remove a lock at any time or the system may crash in such a way that it loses the record of the lock's existence.
Since server lock support is optional, a client trying to lock a resource on a server can either try the lock and hope for the best, or perform some form of discovery to determine what lock capabilities the server supports. This is known as lock capability discovery. A client can determine what lock types the server supports by retrieving the DAV:supportedlock property.
Any DAV compliant resource that supports the LOCK method MUST support the DAV:supportedlock property.
If another principal locks a resource that a principal wishes to access, it is useful for the second principal to be able to find out who the first principal is. For this purpose the DAV:lockdiscovery property is provided. This property lists all outstanding locks, describes their type, and MAY even provide the lock tokens.
Any DAV compliant resource that supports the LOCK method MUST support the DAV:lockdiscovery property.
A resource may be made available through more than one URI. A lock MUST cover the resource as well as the URI to which the LOCK request was addressed. The lock MAY cover other URIs mapped to the same resource as well.
This section describes the semantics specific to the write lock type. The write lock is a specific instance of a lock type, and is the only lock type described in this specification.
An exclusive write lock will prevent parallel changes to a resource by any principal other than the lock creator and in any case where the lock token is not submitted (e.g. by a client process other than the one holding the lock).
Clients MUST submit a lock-token they are authorized to use in any request which modifies a write-locked resource. The list of modifications covered by a write-lock include:
Of the methods defined in HTTP and WebDAV, PUT, POST, PROPPATCH, LOCK, UNLOCK, MOVE, COPY (for the destination resource), DELETE, and MKCOL are affected by write locks. All other HTTP/WebDAV methods defined so far, GET in particular, function independently of a write lock.
The next few sections describe in more specific terms how write locks interact with various operations.
While those without a write lock may not alter a property on a resource it is still possible for the values of live properties to change, even while locked, due to the requirements of their schemas. Only dead properties and live properties defined to respect locks are guaranteed not to change while write locked.
Although the write locks provide some help in preventing lost updates, they cannot guarantee that updates will never be lost. Consider the following scenario:
Two clients A and B are interested in editing the resource 'index.html'. Client A is an HTTP client rather than a WebDAV client, and so does not know how to perform locking.
Client A doesn't lock the document, but does a GET and begins editing.
Client B does LOCK, performs a GET and begins editing.
Client B finishes editing, performs a PUT, then an UNLOCK.
Client A performs a PUT, overwriting and losing all of B's changes.
There are several reasons why the WebDAV protocol itself cannot prevent this situation. First, it cannot force all clients to use locking because it must be compatible with HTTP clients that do not comprehend locking. Second, it cannot require servers to support locking because of the variety of repository implementations, some of which rely on reservations and merging rather than on locking. Finally, being stateless, it cannot enforce a sequence of operations like LOCK / GET / PUT / UNLOCK.
WebDAV servers that support locking can reduce the likelihood that clients will accidentally overwrite each other's changes by requiring clients to lock resources before modifying them. Such servers would effectively prevent HTTP 1.0 and HTTP 1.1 clients from modifying resources.
WebDAV clients can be good citizens by using a lock / retrieve / write /unlock sequence of operations (at least by default) whenever they interact with a WebDAV server that supports locking.
HTTP 1.1 clients can be good citizens, avoiding overwriting other clients' changes, by using entity tags in If-Match headers with any requests that would modify resources.
Information managers may attempt to prevent overwrites by implementing client-side procedures requiring locking before modifying WebDAV resources.
WebDAV provides the ability to lock an unmapped URL in order to reserve the name for use. This is a simple way to avoid the lost-update problem on the creation of a new resource (another way is to use If-None-Match header specified in HTTP 1.1). It has the side benefit of locking the new resource immediately for use of the creator.
Note that the lost-update problem is not an issue for collections because MKCOL can only be used to create a collection, not to overwrite an existing collection. When trying to lock a collection upon creation, clients may attempt to increase the likelihood of getting the lock by pipelining the MKCOL and LOCK requests together (but because this doesn't convert two separate operations into one atomic operation there's no guarantee this will work).
A successful lock request to an unmapped URL MUST result in the creation of an locked resource with empty content. Subsequently, a successful PUT request (with the correct lock token) provides the content for the resource, and a server that normally uses the client-provided content-type MUST also use the content-type and content-language information from this request.
The original WebDAV model for locking unmapped URLs created "lock-null resources". This model was over-complicated and some interoperability and implementation problems were discovered. The new WebDAV model for locking unmapped URLs creates "locked empty resources". Servers MUST implement either lock-null resources or locked empty resources, but servers SHOULD implement locked empty resources. This section discusses the original model briefly and the new model more completely, because clients MUST be able to handle either model.
In the original "lock-null resource" model, which is no longer recommended for implementation:
In the "locked empty resource" model, which is now the recommended implementation, a resource created with a LOCK is empty but otherwise behaves in every way as a normal resource. It behaves as a same resource that would result from a PUT request with an empty body (and where a Content-Type and Content-Language was not specified), followed by a LOCK request to the same resource. Following from this model, a locked empty resource:
The client is expected to update the locked empty resource shortly after locking it, using PUT and possibly PROPPATCH.
Clients can easily interoperate both with servers that support the old model "lock-null resources" and the recommended model of "locked empty resources" by only attempting PUT after a LOCK to an unmapped URL, not MKCOL or GET.
A write lock on a collection, whether created by a "Depth: 0" or "Depth: infinity" lock request, prevents the addition or removal of member URLs of the collection by principals other than the lock creator.
A zero-depth lock on a collection affects changes to the direct membership of that collection. When a principal issues a write request to create a new resource in a write locked collection, or isses a DELETE, MOVE or other request that would remove an existing internal member URL of a write locked collection or change the binding name, this request MUST fail if the principal does not provide the correct lock token for the locked collection.
This means that if a collection is locked (depth 0 or infinity), its lock-token is required in all these cases:
The collection's lock token is required in addition to the lock token on the internal member itself, if it is locked separately.
In addition, a depth-infinity lock affects all write operations to all descendents of the locked collection. With a depth-infinity lock, the root of the lock is directly locked, and all its descendants are indirectly locked.
If a depth-infinity write LOCK request is issued to a collection containing member URLs identifying resources that are currently locked in a manner which conflicts with the new lock (see Section 6.1 point 3), the request MUST fail with a 423 (Locked) status code, and the response SHOULD contain the 'no-conflicting-lock' precondition.
If a lock creator causes the URL of a resource to be added as an internal member URL of a depth-infinity locked collection then the new resource MUST be automatically added to the lock. This is the only mechanism that allows a resource to be added to a write lock. Thus, for example, if the collection /a/b/ is write locked and the resource /c is moved to /a/b/c then resource /a/b/c will be added to the write lock.
If a user agent is not required to have knowledge about a lock when requesting an operation on a locked resource, the following scenario might occur. Program A, run by User A, takes out a write lock on a resource. Program B, also run by User A, has no knowledge of the lock taken out by Program A, yet performs a PUT to the locked resource. In this scenario, the PUT succeeds because locks are associated with a principal, not a program, and thus program B, because it is acting with principal A's credential, is allowed to perform the PUT. However, had program B known about the lock, it would not have overwritten the resource, preferring instead to present a dialog box describing the conflict to the user. Due to this scenario, a mechanism is needed to prevent different programs from accidentally ignoring locks taken out by other programs with the same authorization.
In order to prevent these collisions a lock token MUST be submitted by an authorized principal for all locked resources that a method may change or the method MUST fail. A lock token is submitted when it appears in an If header. For example, if a resource is to be moved and both the source and destination are locked then two lock tokens must be submitted in the if header, one for the source and the other for the destination.
COPY /~fielding/index.html HTTP/1.1 Host: www.example.com Destination: http://www.example.com/users/f/fielding/index.html If: <http://www.example.com/users/f/fielding/index.html> (<urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>)
HTTP/1.1 204 No Content
In this example, even though both the source and destination are locked, only one lock token must be submitted, for the lock on the destination. This is because the source resource is not modified by a COPY, and hence unaffected by the write lock. In this example, user agent authentication has previously occurred via a mechanism outside the scope of the HTTP protocol, in the underlying transport layer.
Consider a collection "/locked" exclusively write-locked with Depth: Infinity, and an attempt to delete an internal member "/locked/member":
DELETE /locked/member HTTP/1.1 Host: example.com
HTTP/1.1 423 Locked Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:error xmlns:D="DAV:"> <D:lock-token-submitted> <D:href>/locked/</D:href> </D:lock-token-submitted> </D:error>
Thus the client would need to submit the lock token with the request to make it succeed. To do that, various forms of the If header (see Section 10.4) could be used.
"Tagged-List" format, for "http://example.com/locked/":
If: <http://example.com/locked/> (<urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf>)
"Tagged-List" format, for "http://example.com/locked/member":
If: <http://example.com/locked/member> (<urn:uuid:150852e2-3847-42d5-8cbe-0f4f296f26cf>)
Note that for the purpose of submitting the lock token the actual form doesn't matter; what's relevant is that the lock token appears in the If header, and that the If header itself evaluates to true.
A COPY method invocation MUST NOT duplicate any write locks active on the source. However, as previously noted, if the COPY copies the resource into a collection that is locked with "Depth: infinity", then the resource will be added to the lock.
A successful MOVE request on a write locked resource MUST NOT move the write lock with the resource. However, if there is an existing lock at the destination, the server MUST add the moved resource to the destination lock scope. For example, if the MOVE makes the resource a child of a collection that is locked with "Depth: infinity", then the resource will be added to that collection's lock. Additionally, if a resource locked with "Depth: infinity" is moved to a destination that is within the scope of the same lock (e.g., within the URL namespace tree covered by the lock), the moved resource will again be a added to the lock. In both these examples, as specified in Section 7.5, an If header must be submitted containing a lock token for both the source and destination.
A client MUST NOT submit the same write lock request twice. Note that a client is always aware it is resubmitting the same lock request because it must include the lock token in the If header in order to make the request for a resource that is already locked.
However, a client may submit a LOCK method with an If header but without a body. This form of LOCK MUST only be used to "refresh" a lock. Meaning, at minimum, that any timers associated with the lock MUST be re-set.
A server may return a Timeout header with a lock refresh that is different than the Timeout header returned when the lock was originally requested. Additionally clients may submit Timeout headers of arbitrary value with their lock refresh requests. Servers, as always, may ignore Timeout headers submitted by the client. Note that timeout is measured in seconds remaining until expiration.
If an error is received in response to a refresh LOCK request the client MUST NOT assume that the lock was refreshed.
In HTTP/1.1, method parameter information was exclusively encoded in HTTP headers. Unlike HTTP/1.1, WebDAV encodes method parameter information either in an [XML] request entity body, or in an HTTP header. The use of XML to encode method parameters was motivated by the ability to add extra XML elements to existing structures, providing extensibility; and by XML's ability to encode information in ISO 10646 character sets, providing internationalization support.
In addition to encoding method parameters, XML is used in WebDAV to encode the responses from methods, providing the extensibility and internationalization advantages of XML for method output, as well as input.
All DAV compliant clients and resources MUST use XML parsers that are compliant with [XML] and XML Namespaces [W3C.REC-xml-names-19990114]. All XML used in either requests or responses MUST be, at minimum, well formed and use namespaces correctly. If a server receives XML that is not well-formed then the server MUST reject the entire request with a 400 (Bad Request). If a client receives XML that is not well-formed in a response then the client MUST NOT assume anything about the outcome of the executed method and SHOULD treat the server as malfunctioning.
Note that processing XML submitted by an untrusted source may cause risks connected to privacy, security, and service quality (see Section 20). Servers MAY reject questionable requests (even though they consist of well-formed XML), for instance with a 400 (Bad Request) status code and an optional response body explaining the problem.
URLs appear in many places in requests and responses. Interoperability experience with [RFC2518] showed that many clients parsing Multi-Status responses did not fully implement the full Reference Resolution defined in Section 5 of [RFC3986]. Thus, servers in particular need to be careful in handling URLs in responses, to ensure that clients have enough context to be able to interpret all the URLs. The rules in this section apply not only to resource URLs in the 'href' element in Multi-Status responses, but also to the Destination and If header resource URLs.
The sender has a choice between two approaches: using a relative reference, which is resolved against the Request-URI, or a full URI. A sender SHOULD generally be consistent once it has chosen one of these approaches, but a server MUST ensure that every 'href' value within a Multi-Status response uses the same format.
WebDAV only uses one form of relative reference in its extensions, the absolute path.
Simple-ref = absolute-URI | ( path-absolute [ "?" query ] )
The absolute-URI and path-absolute productions are defined in section 4.3 and 4.1 of [RFC3986].
Within Simple-ref productions, senders MUST NOT:
Identifiers for collections SHOULD end in a '/' character.
Consider the collection http://example.com/sample/ with the internal member URL http://example.com/sample/a%20test and the PROPFIND request below:
PROPFIND /sample/ HTTP/1.1 Host: example.com Depth: 1
In this case, the server should return two 'href' elements containing either
Note that even though the server may be storing the member resource internally as 'a test', it has to be percent-encoded when used inside a URI reference (see Section 2.1 of [RFC3986]). Also note that a legal URI may still contain characters that need to be escaped within XML character data, such as the ampersand character.
Some of these new methods do not define bodies. Servers MUST examine all requests for a body, even when a body was not expected. In cases where a request body is present but would be ignored by a server, the server MUST reject the request with 415 (Unsupported Media Type). This informs the client (which may have been attempting to use an extension) that the body could not be processed as they intended.
HTTP defines many headers that can be used in WebDAV requests and responses. Not all of these are appropriate in all situations and some interactions may be undefined. Note that HTTP 1.1 requires the Date header in all responses if possible (see section 14.18, [RFC2616]).
The server MUST do authorization checks before checking any HTTP conditional header.
HTTP 1.1 recommends the use of the ETag header in responses to GET and PUT requests. Correct use of ETags is even more important in a distributed authoring environment, because ETags are necessary along with locks to avoid the lost-update problem. A client might fail to renew a lock, for example when the lock times out and the client is accidentally offline or in the middle of a long upload. When a client fails to renew the lock, it's quite possible the resource can still be relocked and the user can go on editing, as long as no changes were made in the meantime. ETags are required for the client to be able to distinguish this case. Otherwise, the client is forced to ask the user whether to overwrite the resource on the server without even being able to tell the user whether it has changed. Timestamps do not solve this problem nearly as well as ETags.
Strong ETags are much more useful for authoring use cases than weak ETags. Semantic equivalence can be a useful concept but that depends on the document type and the application type, and interoperability might require some agreement or standard outside the scope of this specification and HTTP. Note also that weak ETags have certain restrictions in HTTP, e.g. these cannot be used in If-Match headers.
Note that the meaning of an ETag in a PUT response is not clearly defined either in this document or in RFC2616 (i.e., whether the ETag means that the resource is octet-for-octet equivalent to the body of the PUT request, or whether the server could have made minor changes in the formatting or content of the document upon storage). It is hoped that future specification work will clarify this confusion.
Because clients may be forced to prompt users or throw away changed content if the ETag changes, a WebDAV server SHOULD NOT change the ETag (or the Last-Modified time) for a resource that has an unchanged body and location. The ETag represents the state of the body or contents of the resource. There is no similar way to tell if properties have changed.
HTTP and WebDAV did not use the bodies of most error responses for machine-parsable information until DeltaV introduced a mechanism to include more specific information in the body of an error response (section 1.6 of [RFC3253]). The error body mechanism is appropriate to use with any error response that may take a body but does not already have a body defined. The mechanism is particularly appropriate when a status code can mean many things (for example, 400 Bad Request can mean required headers are missing, headers are incorrectly formatted, or much more). This error body mechanism is covered in Section 16
Note that the HTTP response headers "Etag" and "Last-Modified" (see [RFC2616], Sections 14.19 and 14.29) are defined per URL (not per resource), and are used by clients for caching. Therefore servers must ensure that executing any operation that affects the URL namespace (such as COPY, MOVE, DELETE, PUT or MKCOL) does preserve their semantics, in particular:
In practice this means that servers
Note that these considerations also apply to specific use cases, such as using PUT to create a new resource at a URL that has been mapped before, but has been deleted since then.
Finally, WebDAV properties (such as DAV:getetag and DAV: getlastmodified) that inherit their semantics from HTTP headers must behave accordingly.
The PROPFIND method retrieves properties defined on the resource identified by the Request-URI, if the resource does not have any internal members, or on the resource identified by the Request-URI and potentially its member resources, if the resource is a collection that has internal member URLs. All DAV compliant resources MUST support the PROPFIND method and the propfind XML element (Section 14.20) along with all XML elements defined for use with that element.
A client may submit a Depth header with a value of "0", "1", or "infinity" with a PROPFIND on a collection resource. Servers MUST support "0" and "1" depth requests on WebDAV-compliant resources and SHOULD support "infinity" requests. In practice, support for depth infinity requests MAY be disabled, due to the performance and security concerns associated with this behavior. By default, the PROPFIND method without a Depth header MUST act as if a "Depth: infinity" header was included.
A client may submit a 'propfind' XML element in the body of the request method describing what information is being requested. It is possible to:
A client may choose not to submit a request body. An empty PROPFIND request body MUST be treated as if it were an 'allprop' request.
Note that 'allprop' does not return values for all live properties. WebDAV servers increasingly have expensively-calculated or lengthy properties (see [RFC3253] and [RFC3744]) and do not return all properties already. Instead, WebDAV clients can use propname requests to discover what live properties exist, and request named properties when retrieving values. For a live property defined elsewhere, that definition can specify whether that live property would be returned in 'allprop' requests or not.
All servers MUST support returning a response of content type text/xml or application/xml that contains a multistatus XML element that describes the results of the attempts to retrieve the various properties.
If there is an error retrieving a property then a proper error result MUST be included in the response. A request to retrieve the value of a property which does not exist is an error and MUST be noted, if the response uses a 'multistatus' XML element, with a 'response' XML element which contains a 404 (Not Found) status value.
Consequently, the 'multistatus' XML element for a collection resource with member URLs MUST include a 'response' XML element for each member URL of the collection, to whatever depth was requested. Each 'response' XML element MUST contain an 'href' XML element that contains the URL of the resource on which the properties in the prop XML element are defined. Results for a PROPFIND on a collection resource with internal member URLs are returned as a flat list whose order of entries is not significant. Note that a resource may have only one value for a property of a given name, so the property may only show up once in PROPFIND responses.
Properties may be subject to access control. In the case of 'allprop' and 'propname' requests, if a principal does not have the right to know whether a particular property exists then the property MAY be silently excluded from the response.
Some PROPFIND results MAY be cached, with care as there is no cache validation mechanism for most properties. This method is both safe and idempotent (see section 9.1 of [RFC2616]).
This section, as with similar sections for other methods, provides some guidance on error codes and preconditions or postconditions (defined in Section 16) that might be particularly useful with PROPFIND.
403 Forbidden - A server MAY reject PROPFIND requests on collections with depth header of "Infinity", in which case it SHOULD use this error with the precondition code 'propfind-finite-depth' inside the error body.
The following are examples of response codes one would expect to be used in a 207 (Multi-Status) response for this method. Note, however, that unless explicitly prohibited any 2/3/4/5xx series response code may be used in a 207 (Multi-Status) response.
PROPFIND /file HTTP/1.1 Host: www.example.com Content-type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:"> <D:prop xmlns:R="http://ns.example.com/boxschema/"> <R:bigbox/> <R:author/> <R:DingALing/> <R:Random/> </D:prop> </D:propfind>
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D="DAV:"> <D:response xmlns:R="http://ns.example.com/boxschema/"> <D:href>http://www.example.com/file</D:href> <D:propstat> <D:prop> <R:bigbox> <R:BoxType>Box type A</R:BoxType> </R:bigbox> <R:author> <R:Name>J.J. Johnson</R:Name> </R:author> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> <D:propstat> <D:prop><R:DingALing/><R:Random/></D:prop> <D:status>HTTP/1.1 403 Forbidden</D:status> <D:responsedescription> The user does not have access to the DingALing property. </D:responsedescription> </D:propstat> </D:response> <D:responsedescription> There has been an access violation error. </D:responsedescription> </D:multistatus>
In this example, PROPFIND is executed on a non-collection resource http://www.example.com/file. The propfind XML element specifies the name of four properties whose values are being requested. In this case only two properties were returned, since the principal issuing the request did not have sufficient access rights to see the third and fourth properties.
PROPFIND /mycol/ HTTP/1.1 Host: www.example.com Depth: 1 Content-type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:"> <D:prop> <D:creationdate/> <D:getlastmodified/> </D:prop> <D:dead-props/> </D:propfind>
In this example, PROPFIND is executed on a collection resource http://www.example.com/mycol/. The client requests the values of two specific live properties plus all dead properties (names and values). The response is not shown.
PROPFIND /container/ HTTP/1.1 Host: www.example.com Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <propfind xmlns="DAV:"> <propname/> </propfind>
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <multistatus xmlns="DAV:"> <response> <href>http://www.example.com/container/</href> <propstat> <prop xmlns:R="http://ns.example.com/boxschema/"> <R:bigbox/> <R:author/> <creationdate/> <displayname/> <resourcetype/> <supportedlock/> </prop> <status>HTTP/1.1 200 OK</status> </propstat> </response> <response> <href>http://www.example.com/container/front.html</href> <propstat> <prop xmlns:R="http://ns.example.com/boxschema/"> <R:bigbox/> <creationdate/> <displayname/> <getcontentlength/> <getcontenttype/> <getetag/> <getlastmodified/> <resourcetype/> <supportedlock/> </prop> <status>HTTP/1.1 200 OK</status> </propstat> </response> </multistatus>
In this example, PROPFIND is invoked on the collection resource http://www.example.com/container/, with a propfind XML element containing the propname XML element, meaning the name of all properties should be returned. Since no Depth header is present, it assumes its default value of "infinity", meaning the name of the properties on the collection and all its descendents should be returned.
Consistent with the previous example, resource http://www.example.com/container/ has six properties defined on it: bigbox and author in the "http://ns.example.com/boxschema/" namespace, and creationdate, displayname, resourcetype, and supportedlock in the "DAV:" namespace.
The resource http://www.example.com/container/index.html, a member of the "container" collection, has nine properties defined on it, bigbox in the "http://ns.example.com/boxschema/" namespace and, creationdate, displayname, getcontentlength, getcontenttype, getetag, getlastmodified, resourcetype, and supportedlock in the "DAV:" namespace.
This example also demonstrates the use of XML namespace scoping and the default namespace. Since the "xmlns" attribute does not contain a prefix, the namespace applies by default to all enclosed elements. Hence, all elements which do not explicitly state the namespace to which they belong are members of the "DAV:" namespace.
Note that 'allprop', despite its name which remains for backward-compatibility, does not return every property, but only dead properties and the live properties defined in this specification.
PROPFIND /container/ HTTP/1.1 Host: www.example.com Depth: 1 Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:"> <D:allprop/> </D:propfind>
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D="DAV:"> <D:response> <D:href>/container/</D:href> <D:propstat> <D:prop xmlns:R="http://ns.example.com/boxschema/"> <R:bigbox><R:BoxType>Box type A</R:BoxType></R:bigbox> <R:author><R:Name>Hadrian</R:Name></R:author> <D:creationdate>1997-12-01T17:42:21-08:00</D:creationdate> <D:displayname>Example collection</D:displayname> <D:resourcetype><D:collection/></D:resourcetype> <D:supportedlock> <D:lockentry> <D:lockscope><D:exclusive/></D:lockscope> <D:locktype><D:write/></D:locktype> </D:lockentry> <D:lockentry> <D:lockscope><D:shared/></D:lockscope> <D:locktype><D:write/></D:locktype> </D:lockentry> </D:supportedlock> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> <D:response> <D:href>/container/front.html</D:href> <D:propstat> <D:prop xmlns:R="http://ns.example.com/boxschema/"> <R:bigbox><R:BoxType>Box type B</R:BoxType> </R:bigbox> <D:creationdate>1997-12-01T18:27:21-08:00</D:creationdate> <D:displayname>Example HTML resource</D:displayname> <D:getcontentlength>4525</D:getcontentlength> <D:getcontenttype>text/html</D:getcontenttype> <D:getetag>"zzyzx"</D:getetag> <D:getlastmodified >Mon, 12 Jan 1998 09:25:56 GMT</D:getlastmodified> <D:resourcetype/> <D:supportedlock> <D:lockentry> <D:lockscope><D:exclusive/></D:lockscope> <D:locktype><D:write/></D:locktype> </D:lockentry> <D:lockentry> <D:lockscope><D:shared/></D:lockscope> <D:locktype><D:write/></D:locktype> </D:lockentry> </D:supportedlock> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> </D:multistatus>
In this example, PROPFIND was invoked on the resource http://www.example.com/container/ with a Depth header of 1, meaning the request applies to the resource and its children, and a propfind XML element containing the allprop XML element, meaning the request should return the name and value of all the dead properties defined on the resources, plus the name and value of all the properties defined in this specification. This example illustrates the use of relative references in the 'href' elements of the response.
The resource http://www.example.com/container/ has six properties defined on it: 'bigbox' and 'author in the "http://ns.example.com/boxschema/" namespace, DAV:creationdate, DAV:displayname, DAV:resourcetype, and DAV:supportedlock.
The last four properties are WebDAV-specific, defined in Section 15. Since GET is not supported on this resource, the get* properties (e.g., DAV:getcontentlength) are not defined on this resource. The WebDAV-specific properties assert that "container" was created on December 1, 1997, at 5:42:21PM, in a time zone 8 hours west of GMT (DAV:creationdate), has a name of "Example collection" (DAV:displayname), a collection resource type (DAV:resourcetype), and supports exclusive write and shared write locks (DAV:supportedlock).
The resource http://www.example.com/container/front.html has nine properties defined on it:
'bigbox' in the "http://ns.example.com/boxschema/" namespace (another instance of the "bigbox" property type), DAV:creationdate, DAV:displayname, DAV:getcontentlength, DAV:getcontenttype, DAV:getetag, DAV:getlastmodified, DAV:resourcetype, and DAV:supportedlock.
The DAV-specific properties assert that "front.html" was created on December 1, 1997, at 6:27:21PM, in a time zone 8 hours west of GMT (DAV:creationdate), has a name of "Example HTML resource" (DAV:displayname), a content length of 4525 bytes (DAV:getcontentlength), a MIME type of "text/html" (DAV:getcontenttype), an entity tag of "zzyzx" (DAV:getetag), was last modified on Monday, January 12, 1998, at 09:25:56 GMT (DAV:getlastmodified), has an empty resource type, meaning that it is not a collection (DAV:resourcetype), and supports both exclusive write and shared write locks (DAV:supportedlock).
The PROPPATCH method processes instructions specified in the request body to set and/or remove properties defined on the resource identified by the Request-URI.
All DAV compliant resources MUST support the PROPPATCH method and MUST process instructions that are specified using the propertyupdate, set, and remove XML elements. Execution of the directives in this method is, of course, subject to access control constraints. DAV compliant resources SHOULD support the setting of arbitrary dead properties.
The request message body of a PROPPATCH method MUST contain the propertyupdate XML element. Clients SHOULD NOT alter the same property more than once in a single PROPPATCH request.
Servers MUST process PROPPATCH instructions in document order (an exception to the normal rule that ordering is irrelevant). Instructions MUST either all be executed or none executed. Thus if any error occurs during processing all executed instructions MUST be undone and a proper error result returned. Instruction processing details can be found in the definition of the set and remove instructions in Section 14.23 and Section 14.26.
This method is idempotent, but not safe (see section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.
The following are examples of response codes one would expect to be used in a 207 (Multi-Status) response for this method. Note, however, that unless explicitly prohibited any 2/3/4/5xx series response code may be used in a 207 (Multi-Status) response.
200 (OK) - The property set or change succeeded. Note that if this appears for one property, it appears for every property in the response, due to the atomicity of PROPPATCH.
403 (Forbidden) - The client, for reasons the server chooses not to specify, cannot alter one of the properties.
403 (Forbidden): The client has attempted to set a read-only property, such as DAV:getetag. If returning this error, the server SHOULD use the precondition code 'cannot-modify-protected-property' inside the response body.
409 (Conflict) - The client has provided a value whose semantics are not appropriate for the property.
424 (Failed Dependency) - The property change could not be made because of another property change that failed.
507 (Insufficient Storage) - The server did not have sufficient space to record the property.
PROPPATCH /bar.html HTTP/1.1 Host: www.example.com Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:propertyupdate xmlns:D="DAV:" xmlns:Z="http://ns.example.com/standards/z39.50/"> <D:set> <D:prop> <Z:Authors> <Z:Author>Jim Whitehead</Z:Author> <Z:Author>Roy Fielding</Z:Author> </Z:Authors> </D:prop> </D:set> <D:remove> <D:prop><Z:Copyright-Owner/></D:prop> </D:remove> </D:propertyupdate>
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D="DAV:" xmlns:Z="http://ns.example.com/standards/z39.50/"> <D:response> <D:href>http://www.example.com/bar.html</D:href> <D:propstat> <D:prop><Z:Authors/></D:prop> <D:status>HTTP/1.1 424 Failed Dependency</D:status> </D:propstat> <D:propstat> <D:prop><Z:Copyright-Owner/></D:prop> <D:status>HTTP/1.1 409 Conflict</D:status> </D:propstat> <D:responsedescription> Copyright Owner can not be deleted or altered.</D:responsedescription> </D:response> </D:multistatus>
In this example, the client requests the server to set the value of the "Authors" property in the "http://ns.example.com/standards/z39.50/" namespace, and to remove the property "Copyright-Owner" in the same namespace. Since the Copyright-Owner property could not be removed, no property modifications occur. The 424 (Failed Dependency) status code for the Authors property indicates this action would have succeeded if it were not for the conflict with removing the Copyright-Owner property.
The MKCOL method is used to create a new collection. All WebDAV compliant resources MUST support the MKCOL method.
MKCOL creates a new collection resource at the location specified by the Request-URI. If the Request-URI is already mapped to a resource then the MKCOL MUST fail. During MKCOL processing, a server MUST make the Request-URI a member of its parent collection, unless the Request-URI is "/". If no such ancestor exists, the method MUST fail. When the MKCOL operation creates a new collection resource, all ancestors MUST already exist, or the method MUST fail with a 409 (Conflict) status code. For example, if a request to create collection /a/b/c/d/ is made, and /a/b/c/ does not exist, the request must fail.
When MKCOL is invoked without a request body, the newly created collection SHOULD have no members.
A MKCOL request message may contain a message body. The precise behavior of a MKCOL request when the body is present is undefined, but limited to creating collections, members of a collection, bodies of members and properties on the collections or members. If the server receives a MKCOL request entity type it does not support or understand it MUST respond with a 415 (Unsupported Media Type) status code. If the server decides to reject the request based on the presence of an entity or the type of an entity, it should use the 415 (Unsupported Media Type) status code.
This method is idempotent, but not safe (see section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.
In addition to the general status codes possible, the following status codes have specific applicability to MKCOL:
201 (Created) - The collection was created.
403 (Forbidden) - This indicates at least one of two conditions: 1) the server does not allow the creation of collections at the given location in its URL namespace, or 2) the parent collection of the Request-URI exists but cannot accept members.
405 (Method Not Allowed) - MKCOL can only be executed on an unmapped URL.
409 (Conflict) - A collection cannot be made at the Request-URI until one or more intermediate collections have been created. The server MUST NOT create those intermediate collections automatically.
415 (Unsupported Media Type) - The server does not support the request body type (since this specification does not define any body for MKCOL requests).
507 (Insufficient Storage) - The resource does not have sufficient space to record the state of the resource after the execution of this method.
This example creates a collection called /webdisc/xfiles/ on the server www.example.com.
MKCOL /webdisc/xfiles/ HTTP/1.1 Host: www.example.com
HTTP/1.1 201 Created
The semantics of GET are unchanged when applied to a collection, since GET is defined as, "retrieve whatever information (in the form of an entity) is identified by the Request-URI" [RFC2616]. GET when applied to a collection may return the contents of an "index.html" resource, a human-readable view of the contents of the collection, or something else altogether. Hence it is possible that the result of a GET on a collection will bear no correlation to the membership of the collection.
Similarly, since the definition of HEAD is a GET without a response message body, the semantics of HEAD are unmodified when applied to collection resources.
Since by definition the actual function performed by POST is determined by the server and often depends on the particular resource, the behavior of POST when applied to collections cannot be meaningfully modified because it is largely undefined. Thus the semantics of POST are unmodified when applied to a collection.
DELETE is defined in [RFC2616], section 9.7, to "delete the resource identified by the Request-URI". However, WebDAV changes some DELETE handling requirements.
A server processing a successful DELETE request:
Thus, after a successful DELETE operation (and in the absence of other actions) a subsequent GET/HEAD/PROPFIND request to the target Request-URI MUST return 404 (Not Found).
The DELETE method on a collection MUST act as if a "Depth: infinity" header was used on it. A client MUST NOT submit a Depth header with a DELETE on a collection with any value but infinity.
DELETE instructs that the collection specified in the Request-URI and all resources identified by its internal member URLs are to be deleted.
If any resource identified by a member URL cannot be deleted then all of the member's ancestors MUST NOT be deleted, so as to maintain URL namespace consistency.
Any headers included with DELETE MUST be applied in processing every resource to be deleted.
When the DELETE method has completed processing it MUST result in a consistent URL namespace.
If an error occurs deleting an internal resource (a resource other than the resource identified in the Request-URI) then the response can be a 207 (Multi-Status). Multi-Status is used here to indicate which internal resources could NOT be deleted, including an error code which should help the client understand which resources caused the failure. For example, the Multi-Status body could include a response with status 423 (Locked) if an internal resource was locked.
The server MAY return a 4xx status response, rather than a 207, if the request failed completely.
424 (Failed Dependency) status codes SHOULD NOT be in the 207 (Multi-Status) response for DELETE. They can be safely left out because the client will know that the ancestors of a resource could not be deleted when the client receives an error for the ancestor's progeny. Additionally 204 (No Content) errors SHOULD NOT be returned in the 207 (Multi-Status). The reason for this prohibition is that 204 (No Content) is the default success code.
DELETE /container/ HTTP/1.1 Host: www.example.com
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <d:multistatus xmlns:d="DAV:"> <d:response> <d:href>http://www.example.com/container/resource3</d:href> <d:status>HTTP/1.1 423 Locked</d:status> <d:error><d:lock-token-submitted/></d:error> </d:response> </d:multistatus>
In this example the attempt to delete http://www.example.com/container/resource3 failed because it is locked, and no lock token was submitted with the request. Consequently, the attempt to delete http://www.example.com/container/ also failed. Thus the client knows that the attempt to delete http://www.example.com/container/ must have also failed since the parent can not be deleted unless its child has also been deleted. Even though a Depth header has not been included, a depth of infinity is assumed because the method is on a collection.
A PUT performed on an existing resource replaces the GET response entity of the resource. Properties defined on the resource may be recomputed during PUT processing but are not otherwise affected. For example, if a server recognizes the content type of the request body, it may be able to automatically extract information that could be profitably exposed as properties.
A PUT that would result in the creation of a resource without an appropriately scoped parent collection MUST fail with a 409 (Conflict).
A PUT request is the only way a client has to indicate to the server what Content-Type a resource should have, and whether it should change if the resource is overwritten. Thus, a client MUST provide a Content-Type for a new resource if any is known, and a server SHOULD use the Content-Type header value on any PUT request as the resource's type (unless security concerns or policy dictates otherwise). If the client does not provide a Content-Type for a new resource, the server MAY create a resource with no Content-Type assigned, or it MAY attempt to assign a reasonable and legal Content-Type.
Note that although a recipient should treat metadata supplied with an HTTP request as authorative, in practice there's no guarantee that a server will accept Content- headers. Many servers do not allow configuring the Content-Type on a per-resource basis in the first place. Thus, clients should not rely on the ability to directly influence the content type by including a Content-Type request header.
This specification does not define the behavior of the PUT method for existing collections. A PUT request to an existing collection MAY be treated as an error (405 Method Not Allowed).
The MKCOL method is defined to create collections.
The COPY method creates a duplicate of the source resource identified by the Request-URI, in the destination resource identified by the URI in the Destination header. The Destination header MUST be present. The exact behavior of the COPY method depends on the type of the source resource.
All WebDAV compliant resources MUST support the COPY method. However, support for the COPY method does not guarantee the ability to copy a resource. For example, separate programs may control resources on the same server. As a result, it may not be possible to copy a resource to a location that appears to be on the same server.
This method is idempotent, but not safe (see section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.
When the source resource is not a collection the result of the COPY method is the creation of a new resource at the destination whose state and behavior match that of the source resource as closely as possible. Since the environment at the destination may be different than at the source due to factors outside the scope of control of the server, such as the absence of resources required for correct operation, it may not be possible to completely duplicate the behavior of the resource at the destination. Subsequent alterations to the destination resource will not modify the source resource. Subsequent alterations to the source resource will not modify the destination resource.
After a successful COPY invocation, all dead properties on the source resource MUST be duplicated on the destination resource, along with all properties as appropriate. Live properties described in this document SHOULD be duplicated as identically behaving live properties at the destination resource, but not necessarily with the same values. Servers SHOULD NOT convert live properties into dead properties on the destination resource, because clients may then draw incorrect conclusions about the state or functionality of a resource. Note that some live properties are defined such that the absence of the property has a specific meaning (e.g. a flag with one meaning if present and the opposite if absent), and in these cases, a successful COPY might result in the property being reported as "Not Found" in subsequent requests.
A COPY operation creates a new resource, much like a PUT operation does. Live properties which are related to resource creation (such as DAV:creationdate) should have their values set accordingly.
The COPY method on a collection without a Depth header MUST act as if a Depth header with value "infinity" was included. A client may submit a Depth header on a COPY on a collection with a value of "0" or "infinity". Servers MUST support the "0" and "infinity" Depth header behaviors on WebDAV-compliant resources.
A COPY of depth infinity instructs that the collection resource identified by the Request-URI is to be copied to the location identified by the URI in the Destination header, and all its internal member resources are to be copied to a location relative to it, recursively through all levels of the collection hierarchy. Note that a depth infinity COPY of /A/ into /A/B/ could lead to infinite recursion if not handled correctly.
A COPY of "Depth: 0" only instructs that the collection and its properties but not resources identified by its internal member URLs, are to be copied.
Any headers included with a COPY MUST be applied in processing every resource to be copied with the exception of the Destination header.
The Destination header only specifies the destination URI for the Request-URI. When applied to members of the collection identified by the Request-URI the value of Destination is to be modified to reflect the current location in the hierarchy. So, if the Request-URI is /a/ with Host header value http://example.com/ and the Destination is http://example.com/b/ then when http://example.com/a/c/d is processed it must use a Destination of http://example.com/b/c/d.
When the COPY method has completed processing it MUST have created a consistent URL namespace at the destination (see Section 5.1 for the definition of namespace consistency). However, if an error occurs while copying an internal collection, the server MUST NOT copy any resources identified by members of this collection (i.e., the server must skip this subtree), as this would create an inconsistent namespace. After detecting an error, the COPY operation SHOULD try to finish as much of the original copy operation as possible (i.e., the server should still attempt to copy other subtrees and their members, that are not descendents of an error-causing collection).
So, for example, if an infinite depth copy operation is performed on collection /a/, which contains collections /a/b/ and /a/c/, and an error occurs copying /a/b/, an attempt should still be made to copy /a/c/. Similarly, after encountering an error copying a non-collection resource as part of an infinite depth copy, the server SHOULD try to finish as much of the original copy operation as possible.
If an error in executing the COPY method occurs with a resource other than the resource identified in the Request-URI then the response MUST be a 207 (Multi-Status), and the URL of the resource causing the failure MUST appear with the specific error.
The 424 (Failed Dependency) status code SHOULD NOT be returned in the 207 (Multi-Status) response from a COPY method. These responses can be safely omitted because the client will know that the progeny of a resource could not be copied when the client receives an error for the parent. Additionally 201 (Created)/204 (No Content) status codes SHOULD NOT be returned as values in 207 (Multi-Status) responses from COPY methods. They, too, can be safely omitted because they are the default success codes.
If a COPY request has an Overwrite header with a value of "F", and a resource exists at the Destination URL, the server MUST fail the request.
When a server executes a COPY request and overwrites a destination resource, the exact behavior MAY depend on many factors, including WebDAV extension capabilities (see particularly [RFC3253]). For example, when an ordinary resource is overwritten, the server could delete the target resource before doing the copy, or could do an in-place overwrite to preserve live properties.
When a collection is overwritten, the membership of the destination collection after the successful COPY request MUST be the same membership as the source collection immediately before the COPY. Thus, merging the membership of the source and destination collections together in the destination is not a compliant behavior.
In general, if clients require the state of the destination URL to be wiped out prior to a COPY (e.g. to force live properties to be reset), then the client could send a DELETE to the destination before the COPY request to ensure this reset.
In addition to the general status codes possible, the following status codes have specific applicability to COPY:
201 (Created) - The source resource was successfully copied. The COPY operation resulted in the creation of a new resource.
204 (No Content) - The source resource was successfully copied to a pre-existing destination resource.
207 (Multi-Status) - Multiple resources were to be affected by the COPY, but errors on some of them prevented the operation from taking place. Specific error messages, together with the most appropriate of the source and destination URLs, appear in the body of the multi-status response. E.g. if a destination resource was locked and could not be overwritten, then the destination resource URL appears with the 423 (Locked) status.
403 (Forbidden) - The operation is forbidden. A special case for COPY could be that the source and destination resources are the same resource.
409 (Conflict) - A resource cannot be created at the destination until one or more intermediate collections have been created. The server MUST NOT create those intermediate collections automatically.
412 (Precondition Failed) - A precondition header check failed, e.g. the Overwrite header is "F" and the destination URL is already mapped to a resource.
423 (Locked) - The destination resource, or resource within the destination collection, was locked. This response SHOULD contain the 'lock-token-submitted' precondition element.
502 (Bad Gateway) - This may occur when the destination is on another server, repository or URL namespace. Either the source namespace does not support copying to the destination namespace, or the destination namespace refuses to accept the resource. The client may wish to try GET/PUT and PROPFIND/PROPPATCH instead.
507 (Insufficient Storage) - The destination resource does not have sufficient space to record the state of the resource after the execution of this method.
This example shows resource http://www.example.com/~fielding/index.html being copied to the location http://www.example.com/users/f/fielding/index.html. The 204 (No Content) status code indicates the existing resource at the destination was overwritten.
COPY /~fielding/index.html HTTP/1.1 Host: www.example.com Destination: http://www.example.com/users/f/fielding/index.html
HTTP/1.1 204 No Content
The following example shows the same copy operation being performed, but with the Overwrite header set to "F." A response of 412 (Precondition Failed) is returned because the destination URL is already mapped to a resource.
COPY /~fielding/index.html HTTP/1.1 Host: www.example.com Destination: http://www.example.com/users/f/fielding/index.html Overwrite: F
HTTP/1.1 412 Precondition Failed
COPY /container/ HTTP/1.1 Host: www.example.com Destination: http://www.example.com/othercontainer/ Depth: infinity
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <d:multistatus xmlns:d="DAV:"> <d:response> <d:href>http://www.example.com/othercontainer/R2/</d:href> <d:status>HTTP/1.1 423 Locked</d:status> </d:response> </d:multistatus>
The Depth header is unnecessary as the default behavior of COPY on a collection is to act as if a "Depth: infinity" header had been submitted. In this example most of the resources, along with the collection, were copied successfully. However the collection R2 failed because the destination R2 is locked. Because there was an error copying R2, none of R2's members were copied. However no errors were listed for those members due to the error minimization rules.
The MOVE operation on a non-collection resource is the logical equivalent of a copy (COPY), followed by consistency maintenance processing, followed by a delete of the source, where all three actions are performed atomically. The consistency maintenance step allows the server to perform updates caused by the move, such as updating all URLs other than the Request-URI which identify the source resource, to point to the new destination resource. Consequently, the Destination header MUST be present on all MOVE methods and MUST follow all COPY requirements for the COPY part of the MOVE method. All WebDAV compliant resources MUST support the MOVE method. However, support for the MOVE method does not guarantee the ability to move a resource to a particular destination.
For example, separate programs may actually control different sets of resources on the same server. Therefore, it may not be possible to move a resource within a namespace that appears to belong to the same server.
If a resource exists at the destination, the destination resource will be deleted as a side-effect of the MOVE operation, subject to the restrictions of the Overwrite header.
Live properties described in this document SHOULD be moved along with the resource, such that the resource has identically behaving live properties at the destination resource, but not necessarily with the same values. Note that some live properties are defined such that the absence of the property has a specific meaning (e.g. a flag with one meaning if present and the opposite if absent), and in these cases, a successful MOVE might result in the property being reported as "Not Found" in subsequent requests. If the live properties will not work the same way at the destination, the server MAY fail the request.
MOVE is frequently used by clients to rename a file without changing its parent collection, so it's not appropriate to reset all live properties which are set at resource creation. For example, the DAV:creationdate property value SHOULD remain the same after a MOVE.
Dead properties MUST be moved along with the resource.
A MOVE with "Depth: infinity" instructs that the collection identified by the Request-URI be moved to the address specified in the Destination header, and all resources identified by its internal member URLs are to be moved to locations relative to it, recursively through all levels of the collection hierarchy.
The MOVE method on a collection MUST act as if a "Depth: infinity" header was used on it. A client MUST NOT submit a Depth header on a MOVE on a collection with any value but "infinity".
Any headers included with MOVE MUST be applied in processing every resource to be moved with the exception of the Destination header. The behavior of the Destination header is the same as given for COPY on collections.
When the MOVE method has completed processing it MUST have created a consistent URL namespace at both the source and destination (see section 5.1 for the definition of namespace consistency). However, if an error occurs while moving an internal collection, the server MUST NOT move any resources identified by members of the failed collection (i.e., the server must skip the error-causing subtree), as this would create an inconsistent namespace. In this case, after detecting the error, the move operation SHOULD try to finish as much of the original move as possible (i.e., the server should still attempt to move other subtrees and the resources identified by their members, that are not descendents of an error-causing collection). So, for example, if an infinite depth move is performed on collection /a/, which contains collections /a/b/ and /a/c/, and an error occurs moving /a/b/, an attempt should still be made to try moving /a/c/. Similarly, after encountering an error moving a non-collection resource as part of an infinite depth move, the server SHOULD try to finish as much of the original move operation as possible.
If an error occurs with a resource other than the resource identified in the Request-URI then the response MUST be a 207 (Multi-Status), and the errored resource's URL MUST appear with the specific error.
The 424 (Failed Dependency) status code SHOULD NOT be returned in the 207 (Multi-Status) response from a MOVE method. These errors can be safely omitted because the client will know that the progeny of a resource could not be moved when the client receives an error for the parent. Additionally 201 (Created)/204 (No Content) responses SHOULD NOT be returned as values in 207 (Multi-Status) responses from a MOVE. These responses can be safely omitted because they are the default success codes.
If a resource exists at the destination and the Overwrite header is "T" then prior to performing the move the server MUST perform a DELETE with "Depth: infinity" on the destination resource. If the Overwrite header is set to "F" then the operation will fail.
In addition to the general status codes possible, the following status codes have specific applicability to MOVE:
201 (Created) - The source resource was successfully moved, and a new URL mapping was created at the destination.
204 (No Content) - The source resource was successfully moved to a URL that was already mapped.
207 (Multi-Status) - Multiple resources were to be affected by the MOVE, but errors on some of them prevented the operation from taking place. Specific error messages, together with the most appropriate of the source and destination URLs, appear in the body of the multi-status response. E.g. if a source resource was locked and could not be moved, then the source resource URL appears with the 423 (Locked) status.
403 (Forbidden) - Among many possible reasons for forbidding a MOVE operation, this status code is recommended for use when the source and destination resources are the same.
409 (Conflict) - A resource cannot be created at the destination until one or more intermediate collections have been created. The server MUST NOT create those intermediate collections automatically. Or, the server was unable to preserve the behavior of the live properties and still move the resource to the destination (see 'preserved-live-properties' postcondition).
412 (Precondition Failed) - A condition header failed. Specific to MOVE, this could mean that the Overwrite header is "F" and the state of the destination URL is already mapped to a resource.
423 (Locked) - The source or the destination resource, the source or destination resource parent, or some resource within the source or destination collection, was locked. This response SHOULD contain the 'lock-token-submitted' precondition element.
502 (Bad Gateway) - This may occur when the destination is on another server and the destination server refuses to accept the resource. This could also occur when the destination is on another sub-section of the same server namespace.
This example shows resource http://www.example.com/~fielding/index.html being moved to the location http://www.example.com/users/f/fielding/index.html. The contents of the destination resource would have been overwritten if the destination URL was already mapped to a resource. In this case, since there was nothing at the destination resource, the response code is 201 (Created).
MOVE /~fielding/index.html HTTP/1.1 Host: www.example.com Destination: http://www.example/users/f/fielding/index.html
HTTP/1.1 201 Created Location: http://www.example.com/users/f/fielding/index.html
MOVE /container/ HTTP/1.1 Host: www.example.com Destination: http://www.example.com/othercontainer/ Overwrite: F If: (<urn:uuid:fe184f2e-6eec-41d0-c765-01adc56e6bb4>) (<urn:uuid:e454f3f3-acdc-452a-56c7-00a5c91e4b77>)
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <d:multistatus xmlns:d='DAV:'> <d:response> <d:href>http://www.example.com/othercontainer/C2/</d:href> <d:status>HTTP/1.1 423 Locked</d:status> </d:response> </d:multistatus>
In this example the client has submitted a number of lock tokens with the request. A lock token will need to be submitted for every resource, both source and destination, anywhere in the scope of the method, that is locked. In this case the proper lock token was not submitted for the destination http://www.example.com/othercontainer/C2/. This means that the resource /container/C2/ could not be moved. Because there was an error moving /container/C2/, none of /container/C2's members were moved. However no errors were listed for those members due to the error minimization rules. User agent authentication has previously occurred via a mechanism outside the scope of the HTTP protocol, in an underlying transport layer.
The following sections describe the LOCK method, which is used to take out a lock of any access type and to refresh an existing lock. These sections on the LOCK method describe only those semantics that are specific to the LOCK method and are independent of the access type of the lock being requested.
Any resource which supports the LOCK method MUST, at minimum, support the XML request and response formats defined herein.
This method is neither idempotent nor safe (see section 9.1 of [RFC2616]). Responses to this method MUST NOT be cached.
A LOCK request to an existing resource will create a lock on the resource identified by the Request-URI, provided the resource is not already locked with a conflicting lock. The resource identified in the Request-URI becomes the root of the lock. Lock method requests to create a new lock MUST have a XML request body. The server MUST preserve the information provided by the client in the 'owner' field in the request body when the lock information is requested. The LOCK request MAY have a Timeout header.
When a new lock is created, the LOCK response:
A lock is refreshed by sending a LOCK request to the URL of a resource within the scope of the lock. This request MUST NOT have a body and it MUST specify which lock to refresh by using the 'Lock-Token' header with a single lock token (only one lock may be refreshed at a time). It MAY contain a Timeout header, which a server MAY accept to change the duration remaining on the lock to the new value. A server MUST ignore the Depth header on a LOCK refresh.
If the resource has other (shared) locks, those locks are unaffected by a lock refresh. Additionally, those locks do not prevent the named lock from being refreshed.
Note that in RFC2518, clients were indicated through the example in the text to use the If header to specify what lock to refresh (rather than the Lock-Token header). Servers are encouraged to continue to support this as well as the Lock-Token header.
Note that the Lock-Token header is not be returned in the response for a successful refresh LOCK request, but the LOCK response body MUST contain the new value for the DAV:lockdiscovery body.
The Depth header may be used with the LOCK method. Values other than 0 or infinity MUST NOT be used with the Depth header on a LOCK method. All resources that support the LOCK method MUST support the Depth header.
A Depth header of value 0 means to just lock the resource specified by the Request-URI.
If the Depth header is set to infinity then the resource specified in the Request-URI along with all its internal members, all the way down the hierarchy, are to be locked. A successful result MUST return a single lock token which represents all the resources that have been locked. If an UNLOCK is successfully executed on this token, all associated resources are unlocked. Hence, partial success is not an option. Either the entire hierarchy is locked or no resources are locked.
If the lock cannot be granted to all resources, the server MUST return a Multi-Status response with a 'response' element for at least one resource which prevented the lock from being granted, along with a suitable status code for that failure (e.g. 403 (Forbidden) or 423 (Locked)). Additionally, if the resource causing the failure was not the resource requested, then the server SHOULD include a 'response' element for the Request-URI as well, with a 'status' element containing 424 Failed Dependency.
If no Depth header is submitted on a LOCK request then the request MUST act as if a "Depth:infinity" had been submitted.
A successful LOCK method MUST result in the creation of an empty resource which is locked (and which is not a collection), when a resource did not previously exist at that URL. Later on, the lock may go away but the empty resource remains. Empty resources MUST then appear in PROPFIND responses including that URL in the response scope. A server MUST respond successfully to a GET request to an empty resource, either by using a 204 No Content response, or by using 200 OK with a Content-Length header indicating zero length and no Content-Type.
The table below describes the behavior that occurs when a lock request is made on a resource.
|Current State||Shared Lock OK||Exclusive Lock OK|
Legend: True = lock may be granted. False = lock MUST NOT be granted. *=It is illegal for a principal to request the same lock twice.
The current lock state of a resource is given in the leftmost column, and lock requests are listed in the first row. The intersection of a row and column gives the result of a lock request. For example, if a shared lock is held on a resource, and an exclusive lock is requested, the table entry is "false", indicating the lock must not be granted.
In addition to the general status codes possible, the following status codes have specific applicability to LOCK:
200 (OK) - The LOCK request succeeded and the value of the DAV:lockdiscovery property is included in the response body.
201 (Created) - The LOCK request was to an unmapped URL, the request succeeded and resulted in the creation of a new resource, and the value of the DAV:lockdiscovery property is included in the response body.
409 (Conflict) - A resource cannot be created at the destination until one or more intermediate collections have been created. The server MUST NOT create those intermediate collections automatically.
423 (Locked), potentially with 'no-conflicting-lock' precondition code - There is already a lock on the resource which is not compatible with the requested lock (see lock compatibility table above).
400 (Bad Request), with 'lock-token-matches-request-uri' precondition code - The LOCK request was made with a Lock-Token header, indicating that the client wishes to refresh the given lock. However, the Request-URI did not fall within the scope of the lock identified by the token. The lock may have a scope that does not include the Request-URI, or the lock could have disappeared, or the token may be invalid.
LOCK /workspace/webdav/proposal.doc HTTP/1.1 Host: example.com Timeout: Infinite, Second-4100000000 Content-Type: application/xml; charset="utf-8" Content-Length: xxxx Authorization: Digest username="ejw", realm="email@example.com", nonce="...", uri="/workspace/webdav/proposal.doc", response="...", opaque="..." <?xml version="1.0" encoding="utf-8" ?> <D:lockinfo xmlns:D='DAV:'> <D:lockscope><D:exclusive/></D:lockscope> <D:locktype><D:write/></D:locktype> <D:owner> <D:href>http://example.org/~ejw/contact.html</D:href> </D:owner> </D:lockinfo>
HTTP/1.1 200 OK Lock-Token: <urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4> Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:prop xmlns:D="DAV:"> <D:lockdiscovery> <D:activelock> <D:locktype><D:write/></D:locktype> <D:lockscope><D:exclusive/></D:lockscope> <D:depth>infinity</D:depth> <D:owner> <D:href>http://example.org/~ejw/contact.html</D:href> </D:owner> <D:timeout>Second-604800</D:timeout> <D:locktoken> <D:href >urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4</D:href> </D:locktoken> <D:lockroot> <D:href >http://example.com/workspace/webdav/proposal.doc</D:href> </D:lockroot> </D:activelock> </D:lockdiscovery> </D:prop>
This example shows the successful creation of an exclusive write lock on resource http://example.com/workspace/webdav/proposal.doc. The resource http://example.org/~ejw/contact.html contains contact information for the creator of the lock. The server has an activity-based timeout policy in place on this resource, which causes the lock to automatically be removed after 1 week (604800 seconds). Note that the nonce, response, and opaque fields have not been calculated in the Authorization request header.
LOCK /workspace/webdav/proposal.doc HTTP/1.1 Host: example.com Timeout: Infinite, Second-4100000000 Lock-Token: <urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4> Authorization: Digest username="ejw", realm="firstname.lastname@example.org", nonce="...", uri="/workspace/webdav/proposal.doc", response="...", opaque="..."
HTTP/1.1 200 OK Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:prop xmlns:D="DAV:"> <D:lockdiscovery> <D:activelock> <D:locktype><D:write/></D:locktype> <D:lockscope><D:exclusive/></D:lockscope> <D:depth>infinity</D:depth> <D:owner> <D:href>http://example.org/~ejw/contact.html</D:href> </D:owner> <D:timeout>Second-604800</D:timeout> <D:locktoken> <D:href >urn:uuid:e71d4fae-5dec-22d6-fea5-00a0c91e6be4</D:href> </D:locktoken> <D:lockroot> <D:href >http://example.com/workspace/webdav/proposal.doc</D:href> </D:lockroot> </D:activelock> </D:lockdiscovery> </D:prop>
This request would refresh the lock, attempting to reset the timeout to the new value specified in the timeout header. Notice that the client asked for an infinite time out but the server choose to ignore the request. In this example, the nonce, response, and opaque fields have not been calculated in the Authorization request header.
LOCK /webdav/ HTTP/1.1 Host: example.com Timeout: Infinite, Second-4100000000 Depth: infinity Content-Type: application/xml; charset="utf-8" Content-Length: xxxx Authorization: Digest username="ejw", realm="email@example.com", nonce="...", uri="/workspace/webdav/proposal.doc", response="...", opaque="..." <?xml version="1.0" encoding="utf-8" ?> <D:lockinfo xmlns:D="DAV:"> <D:locktype><D:write/></D:locktype> <D:lockscope><D:exclusive/></D:lockscope> <D:owner> <D:href>http://example.org/~ejw/contact.html</D:href> </D:owner> </D:lockinfo>
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D="DAV:"> <D:response> <D:href>http://example.com/webdav/secret</D:href> <D:status>HTTP/1.1 403 Forbidden</D:status> </D:response> <D:response> <D:href>http://example.com/webdav/</D:href> <D:status>HTTP/1.1 424 Failed Dependency</D:status> </D:response> </D:multistatus>
This example shows a request for an exclusive write lock on a collection and all its children. In this request, the client has specified that it desires an infinite length lock, if available, otherwise a timeout of 4.1 billion seconds, if available. The request entity body contains the contact information for the principal taking out the lock, in this case a web page URL.
The error is a 403 (Forbidden) response on the resource http://example.com/webdav/secret. Because this resource could not be locked, none of the resources were locked. Note also that the a 'response' element for the Request-URI itself has been included as required.
In this example, the nonce, response, and opaque fields have not been calculated in the Authorization request header.
The UNLOCK method removes the lock identified by the lock token in the Lock-Token request header. The Request-URI MUST identify a resource within the scope of the lock.
Note that use of Lock-Token header to provide the lock token is not consistent with other state-changing methods which all require an If header with the lock token. Thus, the If header is not needed to provide the lock token. Naturally when the If header is present it has its normal meaning as a conditional header.
For a successful response to this method, the server MUST remove the lock from the resource identified by the Request-URI and from all other resources included in the lock.
If all resources which have been locked under the submitted lock token can not be unlocked then the UNLOCK request MUST fail.
A successful response to an UNLOCK method does not mean that the resource is necessarily unlocked. It means that the specific lock corresponding to the specified token no longer exists.
Any DAV compliant resource which supports the LOCK method MUST support the UNLOCK method.
In addition to the general status codes possible, the following status codes have specific applicability to UNLOCK:
204 (No Content) - Normal success response (rather than 200 OK, since 200 OK would imply a response body, and an UNLOCK success response does not normally contain a body)
400 (Bad Request) - No lock token was provided (see 'lock-token-submitted' precondition), or request was made to a Request-URI that was not within the scope of the lock (see 'lock-token-matches-request-uri' precondition).
403 (Forbidden) - The currently authenticated principal does not have permission to remove the lock.
409 (Conflict) - The resource was not locked and thus could not be unlocked.
UNLOCK /workspace/webdav/info.doc HTTP/1.1 Host: example.com Lock-Token: <urn:uuid:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7> Authorization: Digest username="ejw" realm="firstname.lastname@example.org", nonce="...", uri="/workspace/webdav/proposal.doc", response="...", opaque="..."
HTTP/1.1 204 No Content
In this example, the lock identified by the lock token "urn:uuid:a515cfa4-5da4-22e1-f5b5-00a0451e6bf7" is successfully removed from the resource http://example.com/workspace/webdav/info.doc. If this lock included more than just one resource, the lock is removed from all resources included in the lock. The 204 (No Content) status code is used instead of 200 (OK) because there is no response entity body.
In this example, the nonce, response, and opaque fields have not been calculated in the Authorization request header.
All DAV headers follow the same basic formatting rules as HTTP headers. This includes rules like line continuation and how to combine (or separate) multiple instances of the same header using commas. WebDAV adds two new conditional headers to the set defined in HTTP: the If and Overwrite headers.
DAV = "DAV" ":" #( compliance-class ) compliance-class = ( "1" | "2" | "3" | extend ) extend = Coded-URL | token Coded-URL = "<" absolute-URI ">" ; No LWS allowed in Coded-URL ; absolute-URI is defined in RFC3986
This general-header appearing in the response indicates that the resource supports the DAV schema and protocol as specified. All DAV compliant resources MUST return the DAV header with compliance-class "1" on all OPTIONS responses. In cases where WebDAV is only supported in part of the server namespace, an OPTIONS request to non-WebDAV resources (including "/") SHOULD NOT advertise WebDAV support.
The value is a comma-separated list of all compliance class identifiers that the resource supports. Class identifiers may be Coded-URLs or tokens (as defined by [RFC2616]). Identifiers can appear in any order. Identifiers that are standardized through the IETF RFC process are tokens, but other identifiers SHOULD be Coded-URLs to encourage uniqueness.
A resource must show class 1 compliance if it shows class 2 or 3 compliance. In general, support for one compliance class does not entail support for any other, and in particular, support for compliance class 3 does not require support for compliance class 2. Please refer to Section 18 for more details on compliance classes defined in this specification.
Note that many WebDAV servers do not advertise WebDAV support in response to "OPTIONS *".
As a request header, this header allows the client to advertise compliance with named features when the server needs that information. Clients SHOULD NOT send this header unless a standards track specification requires it. Any extension that makes use of this as a request header will need to carefully consider caching implications.
Depth = "Depth" ":" ("0" | "1" | "infinity")
The Depth request header is used with methods executed on resources which could potentially have internal members to indicate whether the method is to be applied only to the resource ("Depth: 0"), to the resource and its immediate children, ("Depth: 1"), or the resource and all its progeny ("Depth: infinity").
The Depth header is only supported if a method's definition explicitly provides for such support.
The following rules are the default behavior for any method that supports the Depth header. A method may override these defaults by defining different behavior in its definition.
Methods which support the Depth header may choose not to support all of the header's values and may define, on a case by case basis, the behavior of the method if a Depth header is not present. For example, the MOVE method only supports "Depth: infinity" and if a Depth header is not present will act as if a "Depth: infinity" header had been applied.
Clients MUST NOT rely upon methods executing on members of their hierarchies in any particular order or on the execution being atomic unless the particular method explicitly provides such guarantees.
Upon execution, a method with a Depth header will perform as much of its assigned task as possible and then return a response specifying what it was able to accomplish and what it failed to do.
So, for example, an attempt to COPY a hierarchy may result in some of the members being copied and some not.
By default, the Depth header does not interact with other headers. That is, each header on a request with a Depth header MUST be applied only to the Request-URI if it applies to any resource, unless specific Depth behavior is defined for that header.
If a resource, source or destination, within the scope of the method with a Depth header is locked in such a way as to prevent the successful execution of the method, then the lock token for that resource MUST be submitted with the request in the If request header.
The Depth header only specifies the behavior of the method with regards to internal children. If a resource does not have internal children then the Depth header MUST be ignored.
Please note, however, that it is always an error to submit a value for the Depth header that is not allowed by the method's definition. Thus submitting a "Depth: 1" on a COPY, even if the resource does not have internal members, will result in a 400 (Bad Request). The method should fail not because the resource doesn't have internal members, but because of the illegal value in the header.
The Destination request header specifies the URI which identifies a destination resource for methods such as COPY and MOVE, which take two URIs as parameters.
Destination = "Destination" ":" ( Simple-ref )
If the Destination value is an absolute URI, it may name a different server (or different port or scheme). If the source server cannot attempt a copy to the remote server, it MUST fail the request with a 502 (Bad Gateway) response.
If the Destination value is too long or otherwise unacceptable, the server SHOULD return 400 (Bad Request), ideally with helpful information in an error body.
If = "If" ":" ( 1*No-tag-list | 1*Tagged-list) No-tag-list = List Tagged-list = Resource 1*List Resource = Coded-Reference List = "(" 1*(["Not"](State-token | "[" entity-tag "]")) ")" ; No LWS allowed between "[", entity-tag and "]" State-token = Coded-URL Coded-Reference = "<" Simple-ref ">" ; No LWS allowed in Coded-Reference
The If request header is intended to have similar functionality to the If-Match header defined in section 14.24 of [RFC2616]. However the If header is intended for use with any URI which represents state information, referred to as a state token, about a resource as well as ETags. A typical example of a state token is a lock token, and lock tokens are the only state tokens defined in this specification. The <DAV:no-lock> state token is an example of a state token that will never match an actual valid lock token (not that it's special in this regard). The purpose of this is described in Section 10.4.4.
The If header's purpose is to describe a series of state lists. If the state of the resource to which the header is applied does not match any of the specified state lists then the request MUST fail with a 412 (Precondition Failed). If one of the described state lists matches the state of the resource then the request may succeed.
The server MUST do authorization checks before checking this or any conditional header. Assuming no other errors, the server MUST parse the If header when it appears on any request, evaluate all the clauses, and if the conditional evaluates to false, fail as described above.
The No-tag-list production describes a series of state tokens and ETags. If multiple No-tag-list productions are used then one only needs to match the state of the resource for the method to be allowed to continue. All untagged tokens apply to the resource identified in the Request-URI.
Example - no-tag-list production
If: (<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> ["I am an ETag"]) (["I am another ETag"])
The previous header would require that the resource identified in the Request-URI be locked with the specified lock token and in the state identified by the "I am an ETag" ETag or in the state identified by the second ETag "I am another ETag". To put the matter more plainly one can think of the previous If header as being in the form (or (and <urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> ["I am an ETag"]) (and ["I am another ETag"])).
The tagged-list production may be used instead of the no-tag-list production, in order to scope each token to a specific resource. That is, it specifies that the lists following the resource specification only apply to the specified resource. The scope of the resource production begins with the list production immediately following the resource production and ends with the next resource production, if any. All clauses must be evaluated. If the state of the resource named in the tag does not match any of the associated state lists then the request MUST fail with a 412 (Precondition Failed).
The same URI MUST NOT appear more than once in a resource production in an If header.
COPY /resource1 HTTP/1.1 Host: www.example.com Destination: http://www.example.com/resource2 If: <http://www.example.com/resource1> (<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> [W/"A weak ETag"]) (["strong ETag"]) <http://www.example.com/random> (["another strong ETag"])
In this example http://www.example.com/resource1 is being copied to http://www.example.com/resource2. When the method is first applied to http://www.example.com/resource1, resource1 must be in the state specified by "(<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> [W/"A weak ETag"]) (["strong ETag"])", that is, it either must be locked with a lock token of "urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2" and have a weak entity tag W/"A weak ETag" or it must have a strong entity tag "strong ETag".
That is the only success condition since the resource http://www.example.com/random never has the method applied to it (the only other resource listed in the If header) and http://www.example.com/resource2 is not listed in the If header.
Every state token or ETag is either current, and hence describes the state of a resource, or is not current, and does not describe the state of a resource. The boolean operation of matching a state token or ETag to the current state of a resource thus resolves to a true or false value. The "Not" production is used to reverse that value. The scope of the not production is the state-token or entity-tag immediately following it.
If: (Not <urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2> <urn:uuid:58f202ac-22cf-11d1-b12d-002035b29092>)
When submitted with a request, this If header requires that all operand resources must not be locked with urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2 and must be locked with urn:uuid:58f202ac-22cf-11d1-b12d-002035b29092.
The Not production is particularly useful with a state token that never identifies a lock, such as the "<DAV:no-lock>" state token. The server MUST evaluate any unrecognized state token as false. Thus, for example:
When performing If header processing, the definition of a matching state token or entity tag is as follows.
Identifying a resource: The resource is identified by the URI along with the token, in tagged list production, or by the Request-URI in untagged list production.
Matching entity tag: Where the entity tag matches an entity tag associated with the identified resource.
Matching state token: Where there is an exact match between the state token in the If header and any state token on the identified resource. A lock state token is considered to match if the resource is anywhere in the scope of the lock.
Example - Matching lock tokens with collection locks
DELETE /specs/rfc2518.txt HTTP/1.1 Host: www.example.com If: <http://www.example.com/specs/> (<urn:uuid:181d4fae-7d8c-11d0-a765-00a0c91e6bf2>)
For this example, the lock token must be compared to the identified resource, which is the 'specs' collection identified by the URL in the tagged list production. If the 'specs' collection is not locked or has a lock with a different token, the request MUST fail. If the 'specs' collection is locked (depth infinity) with that lock token, then this request could succeed, both because the If header evaluates to true, and because the lock token for the lock affecting the affected resource has been provided. Alternatively, a request where the 'rfc2518.txt' URL is associated with the lock token in the If header could also succeed.
Non-DAV aware proxies will not honor the If header, since they will not understand the If header, and HTTP requires non-understood headers to be ignored. When communicating with HTTP/1.1 proxies, the "Cache-Control: no-cache" request header MUST be used so as to prevent the proxy from improperly trying to service the request from its cache. When dealing with HTTP/1.0 proxies the "Pragma: no-cache" request header MUST be used for the same reason.
Lock-Token = "Lock-Token" ":" Coded-URL
The Lock-Token request header is used with the UNLOCK method to identify the lock to be removed. The lock token in the Lock-Token request header MUST identify a lock that contains the resource identified by Request-URI as a member.
The Lock-Token response header is used with the LOCK method to indicate the lock token created as a result of a successful LOCK request to create a new lock.
Overwrite = "Overwrite" ":" ("T" | "F")
The Overwrite request header specifies whether the server should overwrite a resource mapped to the destination URL during a COPY or MOVE. A value of "F" states that the server must not perform the COPY or MOVE operation if the state of the destination URL does map to a resource. If the overwrite header is not included in a COPY or MOVE request then the resource MUST treat the request as if it has an overwrite header of value "T". While the Overwrite header appears to duplicate the functionality of the If-Match: * header of HTTP/1.1, If-Match applies only to the Request-URI, and not to the Destination of a COPY or MOVE.
If a COPY or MOVE is not performed due to the value of the Overwrite header, the method MUST fail with a 412 (Precondition Failed) status code. The server MUST do authorization checks before checking this or any conditional header.
All DAV compliant resources MUST support the Overwrite header.
TimeOut = "Timeout" ":" 1#TimeType TimeType = ("Second-" DAVTimeOutVal | "Infinite") ; No LWS allowed within TimeType DAVTimeOutVal = 1*DIGIT
Clients may include Timeout request headers in their LOCK requests. However, the server is not required to honor or even consider these requests. Clients MUST NOT submit a Timeout request header with any method other than a LOCK method.
Timeout response values MUST use a Second value or Infinite.
The "Second" TimeType specifies the number of seconds that will elapse between granting of the lock at the server, and the automatic removal of the lock. The timeout value for TimeType "Second" MUST NOT be greater than 2^32-1.
The timeout counter MUST be restarted if a refresh LOCK request is successful. The timeout counter SHOULD NOT be restarted at any other time.
If the timeout expires then the lock may be lost. Specifically, if the server wishes to harvest the lock upon time-out, the server SHOULD act as if an UNLOCK method was executed by the server on the resource using the lock token of the timed-out lock, performed with its override authority. Thus logs should be updated with the disposition of the lock, notifications should be sent, etc., just as they would be for an UNLOCK request.
Servers are advised to pay close attention to the values submitted by clients, as they will be indicative of the type of activity the client intends to perform. For example, an applet running in a browser may need to lock a resource, but because of the instability of the environment within which the applet is running, the applet may be turned off without warning. As a result, the applet is likely to ask for a relatively small timeout value so that if the applet dies, the lock can be quickly harvested. However, a document management system is likely to ask for an extremely long timeout because its user may be planning on going off-line.
A client MUST NOT assume that just because the time-out has expired the lock has been lost. Likewise, a client MUST NOT assume that just because the time-out has not expired, the lock still exists (and for this reason, clients are strongly advised to use ETags as well).
The following status codes are added to those defined in HTTP/1.1 [RFC2616].
The 207 (Multi-Status) status code provides status for multiple independent operations (see Section 13 for more information).
The 422 (Unprocessable Entity) status code means the server understands the content type of the request entity (hence a 415(Unsupported Media Type) status code is inappropriate), and the syntax of the request entity is correct (thus a 400 (Bad Request) status code is inappropriate) but was unable to process the contained instructions. For example, this error condition may occur if an XML request body contains well-formed (i.e., syntactically correct), but semantically erroneous XML instructions.
The 423 (Locked) status code means the source or destination resource of a method is locked. This response SHOULD contain an appropriate precondition or postcondition code, such as 'lock-token-submitted' or 'no-conflicting-lock".
The 424 (Failed Dependency) status code means that the method could not be performed on the resource because the requested action depended on another action and that action failed. For example, if a command in a PROPPATCH method fails then, at minimum, the rest of the commands will also fail with 424 (Failed Dependency).
The 507 (Insufficient Storage) status code means the method could not be performed on the resource because the server is unable to store the representation needed to successfully complete the request. This condition is considered to be temporary. If the request which received this status code was the result of a user action, the request MUST NOT be repeated until it is requested by a separate user action.
These HTTP codes are not redefined, but their use is somewhat extended by WebDAV methods and requirements. In general, many HTTP status codes can be used in response to any request, not just in cases described in this document. Note also that WebDAV servers are known to use 300-level redirect responses (and early interoperability tests found clients unprepared to see those responses). A 300-level request MUST NOT be used when the server has created a new resource in response to the request.
Any request can contain a conditional header defined in HTTP (If-Match, If-Modified-Since, etc.) or the "If" or "Overwrite" conditional headers defined in this specification. If the server evaluates a conditional header, and if that condition fails to hold, then this error code MUST be returned. On the other hand, if the client did not include a conditional header in the request, then the server MUST NOT use this error.
This status code is used in HTTP 1.1 only for Request-URIs, not URIs in other locations.
A Multi-Status response contains one 'response' element for each resource in the scope of the request (in no required order) or MAY be empty if no resources match the request. The default 207 (Multi-Status) response body is a text/xml or application/xml HTTP entity that contains a single XML element called 'multistatus', which contains a set of XML elements called response which contain 200, 300, 400, and 500 series status codes generated during the method invocation. 100 series status codes SHOULD NOT be recorded in a 'response' XML element. The 207 status code itself MUST NOT be considered a success response, it is only completely successful if all 'response' elements inside contain success status codes.
The body of a 207 Multi-Status response MUST contain a URL associated with each specific status code, so that the client can tell whether the error occurred with the source resource, destination resource or some other resource in the scope of the request.
HTTP defines the Location header to indicate a preferred URL for the resource that was addressed in the Request-URI (e.g. in response to successful PUT requests or in redirect responses). However, use of this header creates ambiguity when there are URLs in the body of the response, as with Multi-Status. Thus, use of the Location header with the Multi-Status response is intentionally undefined.
Redirect responses (300-303, 305 and 307) defined in HTTP 1.1 normally take a Location header to indicate the new URI for the single resource redirected from the Request-URI. Multi-Status responses contain many resource addresses, but the original definition in RFC2518 did not have any place for the server to provide the new URI for redirected resources. This specification does define a 'location' element for this information (see Section 14.9). Servers MUST use this new element with redirect responses in Multi-Status.
Clients encountering redirected resources in Multi-Status MUST NOT rely on the 'location' element being present with a new URI. If the element is not present, the client MAY reissue the request to the individual redirected resource, because the response to that request can be redirected with a Location header containing the new URI.
In this section, the final line of each section gives the element type declaration using the format defined in [XML]. The "Value" field, where present, specifies further restrictions on the allowable contents of the XML element using BNF (i.e., to further restrict the values of a PCDATA element). The "Extensibility" field discusses how the element may be extended in the future (or in existing extensions to WebDAV.
All of the elements defined here may be extended by the addition of attributes and child elements not defined in this specification. All elements defined here are in the "DAV:" namespace.
<!ELEMENT activelock (lockscope, locktype, depth, owner?, timeout?, locktoken?, lockroot)>
<!ELEMENT allprop EMPTY >
<!ELEMENT collection EMPTY >
<!ELEMENT depth (#PCDATA) >
<!ELEMENT error ANY >
<!ELEMENT exclusive EMPTY >
<!ELEMENT href (#PCDATA)>
<!ELEMENT include ANY >
<!ELEMENT location (href)>
<!ELEMENT lockentry (lockscope, locktype) >
<!ELEMENT lockinfo (lockscope, locktype, owner?) >
<!ELEMENT lockroot (href) >
<!ELEMENT lockscope (exclusive | shared) >
<!ELEMENT locktoken (href) >
<!ELEMENT locktype (write) >
<!ELEMENT multistatus (response*, responsedescription?) >
<!ELEMENT owner ANY >
<!ELEMENT prop ANY >
<!ELEMENT propertyupdate (remove | set)+ >
<!ELEMENT propfind ( propname | (allprop, include?) | prop ) >
<!ELEMENT propname EMPTY >
<!ELEMENT propstat (prop, status, error?, responsedescription?) >
<!ELEMENT remove (prop) >
<!ELEMENT response (href, ((href*, status)|(propstat+)), error?, responsedescription? , location?) >
<!ELEMENT responsedescription (#PCDATA) >
<!ELEMENT set (prop) >
<!ELEMENT shared EMPTY >
<!ELEMENT status (#PCDATA) >
<!ELEMENT timeout (#PCDATA) >
<!ELEMENT write EMPTY >
For DAV properties, the name of the property is also the same as the name of the XML element that contains its value. In the section below, the final line of each section gives the element type declaration using the format defined in [XML]. The "Value" field, where present, specifies further restrictions on the allowable contents of the XML element using BNF (i.e., to further restrict the values of a PCDATA element).
A protected property is one which cannot be changed with a PROPPATCH request. There may be other requests which would result in a change to a protected property (as when a LOCK request affects the value of DAV:lockdiscovery). Note that a given property could be protected on one type of resource, but not protected on another type of resource.
A computed property is one with a value defined in terms of a computation (based on the content and other properties of that resource, or even of some other resource). A computed property is always a protected property.
COPY and MOVE behavior refers to local COPY and MOVE operations.
For properties defined based on HTTP GET response headers (DAV:get*), the value could include LWS as defined in [RFC2616], section 4.2. Server implementors SHOULD NOT include extra LWS in these values, however client implementors MUST be prepared to handle extra LWS.
<!ELEMENT creationdate (#PCDATA) >
<!ELEMENT displayname (#PCDATA) >
<!ELEMENT getcontentlanguage (#PCDATA) >
<!ELEMENT getcontentlength (#PCDATA) >
<!ELEMENT getcontenttype (#PCDATA) >
<!ELEMENT getetag (#PCDATA) >
<!ELEMENT getlastmodified (#PCDATA) >
<!ELEMENT lockdiscovery (activelock)* >
PROPFIND /container/ HTTP/1.1 Host: www.example.com Content-Length: xxxx Content-Type: application/xml; charset="utf-8" <?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D='DAV:'> <D:prop><D:lockdiscovery/></D:prop> </D:propfind>
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D='DAV:'> <D:response> <D:href>http://www.example.com/container/</D:href> <D:propstat> <D:prop> <D:lockdiscovery> <D:activelock> <D:locktype><D:write/></D:locktype> <D:lockscope><D:exclusive/></D:lockscope> <D:depth>0</D:depth> <D:owner>Jane Smith</D:owner> <D:timeout>Infinite</D:timeout> <D:locktoken> <D:href >urn:uuid:f81de2ad-7f3d-a1b2-4f3c-00a0c91a9d76</D:href> </D:locktoken> <D:lockroot> <D:href>http://www.example.com/container/</D:href> </D:lockroot> </D:activelock> </D:lockdiscovery> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> </D:multistatus>
This resource has a single exclusive write lock on it, with an infinite timeout.
Example: (fictional example to show extensibility)
<x:resourcetype xmlns:x="DAV:"> <x:collection/> <f:search-results xmlns:f="http://www.example.com/ns"/> </x:resourcetype>
<!ELEMENT supportedlock (lockentry)* >
PROPFIND /container/ HTTP/1.1 Host: www.example.com Content-Length: xxxx Content-Type: application/xml; charset="utf-8" <?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:"> <D:prop><D:supportedlock/></D:prop> </D:propfind>
HTTP/1.1 207 Multi-Status Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:multistatus xmlns:D="DAV:"> <D:response> <D:href>http://www.example.com/container/</D:href> <D:propstat> <D:prop> <D:supportedlock> <D:lockentry> <D:lockscope><D:exclusive/></D:lockscope> <D:locktype><D:write/></D:locktype> </D:lockentry> <D:lockentry> <D:lockscope><D:shared/></D:lockscope> <D:locktype><D:write/></D:locktype> </D:lockentry> </D:supportedlock> </D:prop> <D:status>HTTP/1.1 200 OK</D:status> </D:propstat> </D:response> </D:multistatus>
As introduced in section Section 8.6, extra information on error conditions can be included in the body of many status responses. This section makes requirements on the use of the error body mechanism and introduces a number of precondition and postcondition codes.
A "precondition" of a method describes the state of the server that must be true for that method to be performed. A "postcondition" of a method describes the state of the server that must be true after that method has been completed.
Each precondition and postcondition has a unique XML element associated with it. In a 207 Multi-Status response, the XML element MUST appear inside an 'error' element in the appropriate 'propstat or 'response' element depending on whether the condition applies to one or more properties or the resource as a whole. In all other error responses, the XML element MUST be returned as the child of a top-level 'error' element in the response body, unless otherwise negotiated by the request, along with an appropriate response status. The most common response status codes are 403 (Forbidden) if the request should not be repeated because it will always fail, and 409 (Conflict) if it is expected that the user might be able to resolve the conflict and resubmit the request. The 'error' element MAY contain child elements with specific error information and MAY be extended with any custom child elements.
This mechanism does not take the place of using a correct numeric error code as defined here or in HTTP, because the client MUST always be able to take a reasonable course of action based only on the numeric error. However, it does remove the need to define new numeric error codes. The machine-readable codes used for this purpose are XML elements classified as preconditions and postconditions, so naturally any group defining a new error code can use their own namespace. As always, the "DAV:" namespace is reserved for use by IETF-chartered WebDAV working groups.
A server supporting this specification SHOULD use the XML error whenever a precondition or postcondition defined in this document is violated. For error conditions not specified in this document, the server MAY simply choose an appropriate numeric status and leave the response body blank. However, a server MAY instead use a custom error code and other supporting text, because even when clients do not automatically recognize error codes they can be quite useful in interoperability testing and debugging.
Example - Response with precondition code"
HTTP/1.1 423 Locked Content-Type: application/xml; charset="utf-8" Content-Length: xxxx <?xml version="1.0" encoding="utf-8" ?> <D:error xmlns:D="DAV:"> <D:lock-token-submitted> <D:href>/workspace/webdav/</D:href> </D:lock-token-submitted> </D:error>
In this example, a client unaware of a "Depth: infinity" lock on the parent collection "/workspace/webdav/" attempted to modify the collection member "/workspace/webdav/proposal.doc".
All these elements are in the "DAV:" namespace.
<!ELEMENT lock-token-matches-request-uri EMPTY >
<!ELEMENT lock-token-submitted (href+) >
<!ELEMENT no-conflicting-lock (href)* >
<!ELEMENT no-external-entities EMPTY >
<!ELEMENT preserved-live-properties EMPTY >
<!ELEMENT propfind-finite-depth EMPTY >
<!ELEMENT cannot-modify-protected-property EMPTY >
The XML namespace extension [W3C.REC-xml-names-19990114] is used in this specification in order to allow for new XML elements to be added without fear of colliding with other element names. Although WebDAV request and response bodies can be extended by arbitrary XML elements, which can be ignored by the message recipient, an XML element in the "DAV:" namespace SHOULD NOT be used in the request or response body unless that XML element is explicitly defined in an IETF RFC reviewed by a WebDAV working group.
For WebDAV to be both extensibile and backwards-compatible, both clients and servers need to know how to behave when unexpected or unrecognized command extensions are received. For XML processing, this means that clients and servers MUST process received XML documents as if unexpected elements and attributes (and all children of unrecognized elements) were not there. An unexpected element or attribute includes one which may be used in another context but is not expected here. Ignoring such items for purposes of processing can of course be consistent with logging all information or presenting for debugging.
This restriction also applies to the processing, by clients, of DAV property values where unexpected XML elements SHOULD be ignored unless the property's schema declares otherwise.
This restriction does not apply to setting dead DAV properties on the server where the server MUST record all XML elements.
Additionally, this restriction does not apply to the use of XML where XML happens to be the content type of the entity body, for example, when used as the body of a PUT.
When XML is used for a request or response body, the Content-Type type SHOULD be application/xml. Implementations MUST accept both text/xml and application/xml in request and response bodies. Use of text/xml is deprecated.
Processing instructions in XML SHOULD be ignored by recipients. Thus, specifications extending WebDAV SHOULD NOT use processing instructions to define normative behavior.
XML DTD fragments are included for all the XML elements defined in this specification. However, correct XML will not be valid according to any DTD due to namespace usage and extension rules. In particular:
Note that this means that elements containing elements cannot be extended to contain text, and vice versa.
With DTD validation relaxed by the rules above, the constraints described by the DTD fragments are normative (see for example Appendix A A recipient of a WebDAV message with an XML body MUST NOT validate the XML document according to any hard-coded or dynamically-declared DTD.
Note that this section describes backwards-compatible extensibility rules. There might also be times when an extension is designed not to be backwards-compatible, for example defining an extension that reuses an XML element defined in this document but omitting one of the child elements required by the DTDs in this specification.
A DAV compliant resource can advertise several classes of compliance. A client can discover the compliance classes of a resource by executing OPTIONS on the resource, and examining the "DAV" header which is returned. Note particularly that resources are spoken of as being compliant, rather than servers. That is because theoretically some resources on a server could support different feature sets. E.g. a server could have a sub-repository where an advanced feature like server was supported, even if that feature was not supported on all servers.
Since this document describes extensions to the HTTP/1.1 protocol, minimally all DAV compliant resources, clients, and proxies MUST be compliant with [RFC2616].
A resource that is class 2 compliant must also be class 1 compliant, and a resource that is class 3 compliant must also be class 1 compliant.
A class 1 compliant resource MUST meet all "MUST" requirements in all sections of this document.
Class 1 compliant resources MUST return, at minimum, the value "1" in the DAV header on all responses to the OPTIONS method.
A class 2 compliant resource MUST meet all class 1 requirements and support the LOCK method, the DAV:supportedlock property, the DAV:lockdiscovery property, the Time-Out response header and the Lock-Token request header. A class "2" compliant resource SHOULD also support the Time-Out request header and the 'owner' XML element.
Class 2 compliant resources MUST return, at minimum, the values "1" and "2" in the DAV header on all responses to the OPTIONS method.
A resource can explicitly advertise its support for the revisions to RFC2518 made in this document. Class 1 MUST be supported as well. Class 2 MAY be supported. Advertising class 3 support in addition to class 1 and 2 means that the server supports all the requirements in this specification. Advertising class 3 and class 1 support, but not class 2, means that the server supports all the requirements in this specification except possibly those that involve locking support.
DAV: 1, 3
In the realm of internationalization, this specification complies with the IETF Character Set Policy [RFC2277]. In this specification, human-readable fields can be found either in the value of a property, or in an error message returned in a response entity body. In both cases, the human-readable content is encoded using XML, which has explicit provisions for character set tagging and encoding, and requires that XML processors read XML elements encoded, at minimum, using the UTF-8 [RFC3629] and UTF-16 encodings of the ISO 10646 multilingual plane. XML examples in this specification demonstrate use of the charset parameter of the Content-Type header, as defined in [RFC3023], as well as the XML declarations which provide charset identification information for MIME and XML processors.
XML also provides a language tagging capability for specifying the language of the contents of a particular XML element. The "xml:lang" attribute appears on an XML element to identify the language of its content and attributes. See [XML] for definitions of values and scoping.
WebDAV applications MUST support the character set tagging, character set encoding, and the language tagging functionality of the XML specification. Implementors of WebDAV applications are strongly encouraged to read "XML Media Types" [RFC3023] for instruction on which MIME media type to use for XML transport, and on use of the charset parameter of the Content-Type header.
Names used within this specification fall into four categories: names of protocol elements such as methods and headers, names of XML elements, names of properties, and names of conditions. Naming of protocol elements follows the precedent of HTTP, using English names encoded in USASCII for methods and headers. Since these protocol elements are not visible to users, and are simply long token identifiers, they do not need to support multiple languages. Similarly, the names of XML elements used in this specification are not visible to the user and hence do not need to support multiple languages.
WebDAV property names are qualified XML names (pairs of XML namespace name and local name). Although some applications (e.g., a generic property viewer) will display property names directly to their users, it is expected that the typical application will use a fixed set of properties, and will provide a mapping from the property name and namespace to a human-readable field when displaying the property name to a user. It is only in the case where the set of properties is not known ahead of time that an application need display a property name to a user. We recommend that applications provide human-readable property names wherever feasible.
For error reporting, we follow the convention of HTTP/1.1 status codes, including with each status code a short, English description of the code (e.g., 423 (Locked)). While the possibility exists that a poorly crafted user agent would display this message to a user, internationalized applications will ignore this message, and display an appropriate message in the user's language and character set.
Since interoperation of clients and servers does not require locale information, this specification does not specify any mechanism for transmission of this information.
This section is provided to detail issues concerning security implications of which WebDAV applications need to be aware.
All of the security considerations of HTTP/1.1 (discussed in [RFC2616]) and XML (discussed in [RFC3023]) also apply to WebDAV. In addition, the security risks inherent in remote authoring require stronger authentication technology, introduce several new privacy concerns, and may increase the hazards from poor server design. These issues are detailed below.
Due to their emphasis on authoring, WebDAV servers need to use authentication technology to protect not just access to a network resource, but the integrity of the resource as well. Furthermore, the introduction of locking functionality requires support for authentication.
A password sent in the clear over an insecure channel is an inadequate means for protecting the accessibility and integrity of a resource as the password may be intercepted. Since Basic authentication for HTTP/1.1 performs essentially clear text transmission of a password, Basic authentication MUST NOT be used to authenticate a WebDAV client to a server unless the connection is secure. Furthermore, a WebDAV server MUST NOT send Basic authentication credentials in a WWW-Authenticate header unless the connection is secure. Examples of secure connections include a Transport Layer Security (TLS) connection employing a strong cipher suite with mutual authentication of client and server, or a connection over a network which is physically secure, for example, an isolated network in a building with restricted access.
WebDAV applications MUST support the Digest authentication scheme [RFC2617]. Since Digest authentication verifies that both parties to a communication know a shared secret, a password, without having to send that secret in the clear, Digest authentication avoids the security problems inherent in Basic authentication while providing a level of authentication which is useful in a wide range of scenarios.
Denial of service attacks are of special concern to WebDAV servers. WebDAV plus HTTP enables denial of service attacks on every part of a system's resources.
WebDAV servers need to be aware of the possibility of a denial of service attack at all levels. The proper response to such an attack MAY be to simply drop the connection, or if the server is able to make a response, the server MAY use a 400-level status request such as 400 (Bad Request) and indicate why the request was refused (a 500-level status response would indicate that the problem is with the server, whereas unintentional DOS attacks are something the client is capable of remedying).
WebDAV provides, through the PROPFIND method, a mechanism for listing the member resources of a collection. This greatly diminishes the effectiveness of security or privacy techniques that rely only on the difficulty of discovering the names of network resources. Users of WebDAV servers are encouraged to use access control techniques to prevent unwanted access to resources, rather than depending on the relative obscurity of their resource names.
When submitting a lock request a user agent may also submit an 'owner' XML field giving contact information for the person taking out the lock (for those cases where a person, rather than a robot, is taking out the lock). This contact information is stored in a DAV:lockdiscovery property on the resource, and can be used by other collaborators to begin negotiation over access to the resource. However, in many cases this contact information can be very private, and should not be widely disseminated. Servers SHOULD limit read access to the DAV:lockdiscovery property as appropriate. Furthermore, user agents SHOULD provide control over whether contact information is sent at all, and if contact information is sent, control over exactly what information is sent.
Since property values are typically used to hold information such as the author of a document, there is the possibility that privacy concerns could arise stemming from widespread access to a resource's property data. To reduce the risk of inadvertent release of private information via properties, servers are encouraged to develop access control mechanisms that separate read access to the resource body and read access to the resource's properties. This allows a user to control the dissemination of their property data without overly restricting access to the resource's contents.
XML supports a facility known as "external entities", defined in section 4.2.2 of [XML], which instruct an XML processor to retrieve and include additional XML. An external XML entity can be used to append or modify the document type declaration (DTD) associated with an XML document. An external XML entity can also be used to include XML within the content of an XML document. For non-validating XML, such as the XML used in this specification, including an external XML entity is not required by XML. However, XML does state that an XML processor may, at its discretion, include the external XML entity.
External XML entities have no inherent trustworthiness and are subject to all the attacks that are endemic to any HTTP GET request. Furthermore, it is possible for an external XML entity to modify the DTD, and hence affect the final form of an XML document, in the worst case significantly modifying its semantics, or exposing the XML processor to the security risks discussed in [RFC3023]. Therefore, implementers must be aware that external XML entities should be treated as untrustworthy. If a server implementor chooses not to handle external XML entities, it SHOULD respond to requests containing external entities with the precondition defined above (no-external-entities).
There is also the scalability risk that would accompany a widely deployed application which made use of external XML entities. In this situation, it is possible that there would be significant numbers of requests for one external XML entity, potentially overloading any server which fields requests for the resource containing the external XML entity.
Furthermore, there's also a risk based on the evaluation of "internal entities" as defined in section 4.2.2 of [XML]. A small, carefully crafted request using nested internal entities may require enormous amounts of memory and/or processing time to process. Server implementors should be aware of this risk and configure their XML parsers so that requests like these can be detected and rejected as early as possible.
This specification encourages the use of "A Universally Unique Identifier (UUID) URN Namespace" ([RFC4122]) for lock tokens Section 6.5, in order to guarantee their uniqueness across space and time. Version 1 UUIDs (defined in section 4) MAY contain a "node" field that "consists of an IEEE 802 MAC address, usually the host address. For systems with multiple IEEE addresses, any available one can be used". Since a WebDAV server will issue many locks over its lifetime, the implication is that it may also be publicly exposing its IEEE 802 address.
There are several risks associated with exposure of IEEE 802 addresses. Using the IEEE 802 address:
This risk only applies to host address based UUID versions. Section 4 of [RFC4122] describes several other mechanisms for generating UUIDs that do involve the host address and therefore do not suffer from this risk.
HTTP has the ability to host programs which are executed on client machines. These programs can take many forms including web scripts, executables, plug in modules, and macros in documents. WebDAV does not change any of the security concerns around these programs yet often WebDAV is used in contexts where a wide range of users can publish documents on a server. The server might not have a close trust relationship with the author that is publishing the document. Servers that allow clients to publish arbitrary content can usefully implement precautions to check that content published to the server is not harmful to other clients. Servers could do this by techniques such as restricting the types of content that is allowed to be published and running virus and malware detection software on published content. Servers can also mitigate the risk by having appropriate access restriction and authentication of users that are allowed to publish content to the server.
This specification defines two URI schemes:
Note that defining new URI schemes for XML namespaces is now discouraged. "DAV:" was defined before standard best practices emerged.
XML namespaces disambiguate WebDAV property names and XML elements. Any WebDAV user or application can define a new namespace in order to create custom properties or extend WebDAV XML syntax. IANA does not need to manage such namespaces, property names or element names.
The message header fields below should be added to the permanent registry (see [RFC3864]).
Header field name: DAV
Applicable protocol: http
Author/Change controller: IETF
Specification document: this specification (Section 10.1)
Header field name: Depth
Applicable protocol: http
Author/Change controller: IETF
Specification document: this specification (Section 10.2)
Header field name: Destination
Applicable protocol: http
Author/Change controller: IETF
Specification document: this specification (Section 10.3)
Header field name: If
Applicable protocol: http
Author/Change controller: IETF
Specification document: this specification (Section 10.4)
Header field name: Lock-Token
Applicable protocol: http
Author/Change controller: IETF
Specification document: this specification (Section 10.5)
Header field name: Overwrite
Applicable protocol: http
Author/Change controller: IETF
Specification document: this specification (Section 10.6)
A specification such as this thrives on piercing critical review and withers from apathetic neglect. The authors gratefully acknowledge the contributions of the following people, whose insights were so valuable at every stage of our work.
Contributors to RFC2518
Terry Allen, Harald Alvestrand, Jim Amsden, Becky Anderson, Alan Babich, Sanford Barr, Dylan Barrell, Bernard Chester, Tim Berners-Lee, Dan Connolly, Jim Cunningham, Ron Daniel, Jr., Jim Davis, Keith Dawson, Mark Day, Brian Deen, Martin Duerst, David Durand, Lee Farrell, Chuck Fay, Wesley Felter, Roy Fielding, Mark Fisher, Alan Freier, George Florentine, Jim Gettys, Phill Hallam-Baker, Dennis Hamilton, Steve Henning, Mead Himelstein, Alex Hopmann, Andre van der Hoek, Ben Laurie, Paul Leach, Ora Lassila, Karen MacArthur, Steven Martin, Larry Masinter, Michael Mealling, Keith Moore, Thomas Narten, Henrik Nielsen, Kenji Ota, Bob Parker, Glenn Peterson, Jon Radoff, Saveen Reddy, Henry Sanders, Christopher Seiwald, Judith Slein, Mike Spreitzer, Einar Stefferud, Greg Stein, Ralph Swick, Kenji Takahashi, Richard N. Taylor, Robert Thau, John Turner, Sankar Virdhagriswaran, Fabio Vitali, Gregory Woodhouse, and Lauren Wood.
Two from this list deserve special mention. The contributions by Larry Masinter have been invaluable, both in helping the formation of the working group and in patiently coaching the authors along the way. In so many ways he has set high standards we have toiled to meet. The contributions of Judith Slein in clarifying the requirements, and in patiently reviewing draft after draft, both improved this specification and expanded our minds on document management.
We would also like to thank John Turner for developing the XML DTD.
The authors of RFC2518 were Yaron Goland, Jim Whitehead, A. Faizi, Steve Carter and D. Jensen. Although their names had to be removed due to IETF author count restrictions they can take credit for the majority of the design of WebDAV.
Additional Contributors to This Specification
Valuable contributions to this specification came from some already named. New and significant contributors to this specification must also be gratefully acknowledged. Julian Reschke, Geoff Clemm, Joel Soderberg, and Dan Brotsky hashed out specific text on the list or in meetings. Joe Hildebrand and Cullen Jennings helped close many issues. Barry Lind described an additional security consideration and Cullen Jennings provided text for that consideration. Jason Crawford tracked issue status for this document for a period of years, followed by Elias Sinderson. Elias and Jim Whitehead collaborated on specific document text.
Y. Y. Goland, Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399. Email: email@example.com.
E. J. Whitehead, Jr., Dept. Of Information and Computer Science, University of California, Irvine, Irvine, CA 92697-3425. Email: firstname.lastname@example.org.
A. Faizi, Netscape, 685 East Middlefield Road, Mountain View, CA 94043. Email: email@example.com.
S. R. Carter, Novell, 1555 N. Technology Way, M/S ORM F111, Orem, UT 84097-2399. Email: firstname.lastname@example.org.
D. Jensen, Novell, 1555 N. Technology Way, M/S ORM F111, Orem, UT 84097-2399. Email: email@example.com.
|[RFC2119]||Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels”, BCP 14, RFC 2119, March 1997.|
|[RFC2277]||Alvestrand, H., “IETF Policy on Character Sets and Languages”, BCP 18, RFC 2277, January 1998.|
|[RFC2616]||Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, “Hypertext Transfer Protocol -- HTTP/1.1”, RFC 2616, June 1999.|
|[RFC2617]||Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A., and L. Stewart, “HTTP Authentication: Basic and Digest Access Authentication”, RFC 2617, June 1999.|
|[RFC3339]||Klyne, G., Ed. and C. Newman, “Date and Time on the Internet: Timestamps”, RFC 3339, July 2002.|
|[RFC3629]||Yergeau, F., “UTF-8, a transformation format of ISO 10646”, STD 63, RFC 3629, November 2003.|
|[RFC3986]||Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax”, STD 66, RFC 3986, January 2005.|
|[RFC4122]||Leach, P., Mealling, M., and R. Salz, “A Universally Unique IDentifier (UUID) URN Namespace”, RFC 4122, July 2005.|
|[W3C.REC-xml-infoset-20040204]||Cowan, J. and R. Tobin, “XML Information Set (Second Edition)”, World Wide Web Consortium Recommendation REC-xml-infoset-20040204, February 2004, <http://www.w3.org/TR/2004/REC-xml-infoset-20040204>.|
|[W3C.REC-xml-names-19990114]||Layman, A., Bray, T., and D. Hollander, “Namespaces in XML”, World Wide Web Consortium FirstEdition REC-xml-names-19990114, January 1999, <http://www.w3.org/TR/1999/REC-xml-names-19990114>.|
|[XML]||Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E., and F. Yergeau, “Extensible Markup Language (XML) 1.0 (Third Edition)”, W3C REC-xml-20040204, February 2004, <http://www.w3.org/TR/2004/REC-xml-20040204>.|
|[RFC2291]||Slein, J., Vitali, F., Whitehead, E., and D. Durand, “Requirements for a Distributed Authoring and Versioning Protocol for the World Wide Web”, RFC 2291, February 1998.|
|[RFC2518]||Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D. Jensen, “HTTP Extensions for Distributed Authoring -- WEBDAV”, RFC 2518, February 1999.|
|[RFC3023]||Murata, M., St. Laurent, S., and D. Kohn, “XML Media Types”, RFC 3023, January 2001.|
|[RFC3253]||Clemm, G., Amsden, J., Ellison, T., Kaler, C., and J. Whitehead, “Versioning Extensions to WebDAV (Web Distributed Authoring and Versioning)”, RFC 3253, March 2002.|
|[RFC3648]||Whitehead, J. and J. Reschke, Ed., “Web Distributed Authoring and Versioning (WebDAV) Ordered Collections Protocol”, RFC 3648, December 2003.|
|[RFC3744]||Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, “Web Distributed Authoring and Versioning (WebDAV) Access Control Protocol”, RFC 3744, May 2004.|
|[RFC3864]||Klyne, G., Nottingham, M., and J. Mogul, “Registration Procedures for Message Header Fields”, BCP 90, RFC 3864, September 2004.|
XML supports two mechanisms for indicating that an XML element does not have any content. The first is to declare an XML element of the form <A></A>. The second is to declare an XML element of the form <A/>. The two XML elements are semantically identical.
XML is a flexible data format that makes it easy to submit data that appears legal but in fact is not. The philosophy of "Be flexible in what you accept and strict in what you send" still applies, but it must not be applied inappropriately. XML is extremely flexible in dealing with issues of white space, element ordering, inserting new elements, etc. This flexibility does not require extension, especially not in the area of the meaning of elements.
There is no kindness in accepting illegal combinations of XML elements. At best it will cause an unwanted result and at worst it can cause real damage.
The following request body for a PROPFIND method is illegal.
<?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:"> <D:allprop/> <D:propname/> </D:propfind>
The definition of the propfind element only allows for the allprop or the propname element, not both. Thus the above is an error and must be responded to with a 400 (Bad Request).
Imagine, however, that a server wanted to be "kind" and decided to pick the allprop element as the true element and respond to it. A client running over a bandwidth limited line who intended to execute a propname would be in for a big surprise if the server treated the command as an allprop.
Additionally, if a server were lenient and decided to reply to this request, the results would vary randomly from server to server, with some servers executing the allprop directive, and others executing the propname directive. This reduces interoperability rather than increasing it.
The previous example was illegal because it contained two elements that were explicitly banned from appearing together in the propfind element. However, XML is an extensible language, so one can imagine new elements being defined for use with propfind. Below is the request body of a PROPFIND and, like the previous example, must be rejected with a 400 (Bad Request) by a server that does not understand the expired-props element.
<?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:" xmlns:E="http://www.example.com/standards/props/"> <E:expired-props/> </D:propfind>
To understand why a 400 (Bad Request) is returned let us look at the request body as the server unfamiliar with expired-props sees it.
<?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:" xmlns:E="http://www.example.com/standards/props/"> </D:propfind>
As the server does not understand the 'expired-props' element, according to the WebDAV-specific XML processing rules specified in Section 17, it must process the request as if the element were not there. Thus the server sees an empty propfind, which by the definition of the propfind element is illegal.
Please note that had the extension been additive it would not necessarily have resulted in a 400 (Bad Request). For example, imagine the following request body for a PROPFIND:
<?xml version="1.0" encoding="utf-8" ?> <D:propfind xmlns:D="DAV:" xmlns:E="http://www.example.com/standards/props/"> <D:propname/> <E:leave-out>*boss*</E:leave-out> </D:propfind>
The previous example contains the fictitious element leave-out. Its purpose is to prevent the return of any property whose name matches the submitted pattern. If the previous example were submitted to a server unfamiliar with 'leave-out', the only result would be that the 'leave-out' element would be ignored and a propname would be executed.
The PUT and DELETE methods are defined in HTTP and thus may be used by HTTP clients, but the responses to PUT and DELETE have been extended in this specification, so some special consideration on backward compatibility is worthwhile.
First, if a PUT or DELETE request includes a header defined in this specification (Depth or If), the server can assume the request comes from a WebDAV-compatible client. The server may even be able to track a number of requests across a session and know that a client is a WebDAV client. However, this kind of detection may not be necessary.
Since any HTTP client ought to handle unrecognized 400-level and 500-level status codes as errors, the following new status codes should not present any issues: 422, 423 and 507. 424 is also a new status code but it appears only in the body of a Multistatus response. So, for example, if a HTTP client attempted to PUT or DELETE a locked resource, the 423 Locked response ought to result in a generic error presented to the user.
The 207 Multistatus response is interesting because a HTTP client issuing a DELETE request to a collection might interpret a 207 response as a success, even though it does not realize the resource is a collection and cannot understand that the DELETE operation might have been a complete or partial failure. Thus, a server MAY choose to treat a DELETE of a collection as an atomic operation, and use either 204 No Content in case of success, or some appropriate error response (400 or 500 level) depending on what the error was. This approach would maximize backward compatibility. However, since interoperability tests and working group discussions have not turned up any instances of HTTP clients issuing a DELETE request against a WebDAV collection, this concern may be more theoretical than practical. Thus, servers MAY instead choose to treat any such DELETE request as a WebDAV request, and send a 207 Multistatus containing more detail about what resources could not be deleted.
The 'opaquelocktoken' URI scheme was defined in RFC2518 (and registered by IANA) in order to create syntactically correct and easy-to-generate URIs out of UUIDs, intended to be used as lock tokens and to be unique across all resources for all time.
An opaquelocktoken URI is constructed by concatenating the 'opaquelocktoken' scheme with a UUID, along with an optional extension. Servers can create new UUIDs for each new lock token. If a server wishes to reuse UUIDs the server MUST add an extension and the algorithm generating the extension MUST guarantee that the same extension will never be used twice with the associated UUID.
OpaqueLockToken-URI = "opaquelocktoken:" UUID [Extension] ; UUID is defined in section 3 of RFC4122. Note that linear white ; space (LWS) is not allowed between elements of this production. Extension = path ; path is defined in section 3.3 of RFC3986
Many WebDAV clients already implemented have account settings (similar to the way email clients store IMAP account settings). Thus, the WebDAV client would be able to authenticate with its first couple requests to the server, provided it had a way to get the authentication challenge from the server with realm name, nonce and other challenge information. Note that the results of some requests might vary according to whether the client is authenticated or not -- a PROPFIND might return more visible resources if the client is authenticated, yet not fail if the client is anonymous.
There are a number of ways the client might be able to trigger the server do provide an authentication challenge. This appendix describes a couple approaches that seem particularly likely to work.
The first approach is to perform a request that ought to require authentication. However, it's possible that a server might handle any request even without authentication, so to be entirely safe the client could add a conditional header to ensure that even if the request passes permissions checks it's not actually handled by the server. An example of following this approach would be to use a PUT request with an "If-Match" header with a made-up ETag value. This approach might fail to result in an authentication challenge if the server does not test authorization before testing conditionals as is required (see Section 8.4), or if the server does not need to test authorization.
Example - forcing auth challenge with write request
PUT /forceauth.txt HTTP/1.1 Host: www.example.com If-Match: "xxx" Content-Type: text/plain Content-Length: 0
The second approach is to use an Authorization header (defined in [RFC2617]) which is likely to be rejected by the server but which will then prompt a proper authentication challenge. For example, the client could start with a PROPFIND request containing an Authorization header containing a made-up Basic userid:password string or with actual plausible credentials. This approach relies on the server responding with a "401 Unauthorized" along with a challenge if it receives an Authorization header with an unrecognized username, invalid password, or if it doesn't even handle Basic authentication. This seems likely to work because of the requirements of RFC2617:
"If the origin server does not wish to accept the credentials sent with a request, it SHOULD return a 401 (Unauthorized) response. The response MUST include a WWW-Authenticate header field containing at least one (possibly new) challenge applicable to the requested resource."
There's a slight problem with implementing that recommendation in some cases, because some servers do not even have challenge information for certain resources. Thus, when there's no way to authenticate to a resource or the resource is entirely publicly available over all accepted methods, the server MAY ignore the Authorization header, and the client presumably try again later.
Example - forcing auth challenge with Authorization header
PROPFIND /docs/ HTTP/1.1 Host: www.example.com Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ== Content-type: application/xml; charset="utf-8" Content-Length: xxxx [body omitted]
This section lists changes that are likely to result in implementation changes due to tightened requirements or changed behavior.
New value for "DAV:" header (Section 10.1) to advertise support for this specification.
Replaced lock-null resources with simpler locked empty resources (Section 7.3).
Support for UTF-16 now required (ref (Section 19)).
Changed meaning of PROPFIND 'allprop' so that it doesn't have to return live properties not defined in this specification; added 'include' syntax so that clients can retrieve specific live properties along with 'allprop' results.
Changes in LOCK refresh (not implicit anymore, uses LOCK without body with Lock-Token request header)
New element 'location' defined for handling redirected resources in Multi-Status.
Defined response bodies for error responses, including several machine-readable precondition or postcondition codes (Section 16) for error detail.
Removed definition of "source" property and special handling for dynamic resources.
The definition of the 102 Processing response was removed and servers ought to stop sending that response when they implement this specification; clients may be able to remove code that handles this.
Tightened requirements for storing property values (Section 4.3) when "xml:lang" appears and also when values are XML fragments (specifically on preserving prefixes, namespaces and whitespace.)
Tightened requirements on which properties are protected and computed (Section 15).
Several tightened requirements for general response handling (Section 8), including ETag and Location header, and reminder to use Date header.
Requirements for URL construction in Multi-Status responses, Destination and If headers: more consistent and mostly tighter requirements.
Tightened requirements for checking identity of lock creators (Section 6.4) during operations affected by locks.
Tightened requirements on preserving 'owner' field in locks (Section 9.10). Added "lockroot" element to lockdiscovery information.
Some changes for "If:" header (Section 10.4) handling, including "DAV:no-lock" state token.
Encouraged servers to change ETags (Section 8.5) only when body of resource changes.
Previously, servers were encouraged to return 409 status code in response to a collection LOCK request if some resource could not be locked. Now servers should use 207 Multi-Status instead.
Only 'rfc1123-date' productions are legal as values for DAV:getlastmodified.
New explicit requirement to do authorization checks before conditional checks (Section 8.4).
Defined idempotence, safeness and cacheability for all new methods.
Depth: Infinity doesn't affect other headers; by default these headers only apply to the Request-URI (Section 10.4).
Tightened requirements for supporting WebDAV collections (Section 5.2) within resources that do not support WebDAV (e.g. servlet containers).
Servers are no longer required to support all depth "infinity" PROPFIND requests, so clients need to be able to handle that and do multiple depth "1" requests instead.
No more "propertybehavior" specification allowed in MOVE and COPY requests
The change in behavior of LOCK with an unmapped URL might affect client implementations that counted on lock-null resources disappearing when the lock expired. Clients can no longer rely on that cleanup happening.
Clients use Lock-Token header, not the If header, to provide lock token when renewing lock. Section 9.10.2
Clients must refresh locks explicitly as this is now the only way to renew timeout.
Specified that a successful LOCK request to an unmapped URL creates a new, empty locked resource.
Resolved UNLOCK_NEEDS_IF_HEADER by clarifying that only Lock-Token header is needed on UNLOCK.
Added Section 16 on preconditions and postconditions and defined a number of preconditions and postconditions. The 'lock-token-submitted' precondition resolves the REPORT_OTHER_RESOURCE_LOCKED issue.
Added example of matching lock token to URI in the case of a collection lock in the If header section.
Removed ability for Destination header to take "abs_path" in order to keep consistent with other places where client provides URLs (If header, href element in request body)
Clarified the href element - that it generally contains HTTP URIs but not always.
Attempted to fix the BNF describing the If header to allow commas
Clarified presence of Depth header on LOCK refresh requests.
Added text to "COPY and the Overwrite Header" section to resolve issue OVERWRITE_DELETE_ALL_TOO_STRONG.
Added text to "HTTP URL Namespace Model" section to provide more clarification and examples on what consistency means and what is not required, to resolve issue CONSISTENCY.
Resolve DEFINE_PRINCIPAL by importing definition of principal from RFC3744.
Resolve INTEROP_DELETE_AND_MULTISTATUS by adding appendix 3 discussing backward-compatibility concerns.
Resolve DATE_FORMAT_GETLASTMODIFIED by allowing only rfc1123-date, not HTTP-date for getlastmodified.
Resolve COPY_INTO_YOURSELF_CLARIFY by adding sentence to first para. of COPY section.
Confirm that WHEN_TO_MULTISTATUS_FOR_DELETE_1 and WHEN_TO_MULTISTATUS_FOR_DELETE_2 are resolved and tweak language in DELETE section slightly to be clearly consistent.
More text clarifications to deal with several of the issues in LOCK_ISSUES. This may not completely resolve that set but we need feedback from the originator of the issues at this point.
Resolved COPY_INTO_YOURSELF_CLARIFY with new sentence in Copy For Collections section.
Double checked that LEVEL_OR_CLASS is resolved by using class, not level.
Further work to resolve IF_AND_AUTH and LOCK_SEMANTICS, clarifying text on using locks and being authenticated.
Added notes on use of 503 status response to resolve issue PROPFIND_INFINITY
Removed section on other uses of Metadata (and associated references)
Added reference to RFC4122 for lock tokens and removed section on generating UUIDs
Explained that even with language variation, a property has only one value (section 4.5).
Added section on lock owner (7.1) and what to do if lock requested by unauthenticated user
Removed section 4.2 -- justification on why to have metadata, not needed now
Removed paragraph in section 5.2 about collections with resource type "DAV:collection" but which are non-WebDAV compliant -- not implemented.
Added security considerations section on scripts and cookie sessions, suggested by Barry Lind
Clarified which error codes are defined and undefined in MultiStatus
Moved opaquelocktoken definition to an appendix and refer to RFC4122 for use of 'urn:uuid:' URI scheme; fix all lock token examples to use this.
Multi-status responses contain URLs which MUST either be absolute (and begin with the Request-URI or MUST be relative with new limitations. (bug 12)
Moved status code sections before example sections within PROPFIND section for section ordering consistency.
Clarified use of Location header with Multi-Status
Bugzilla issue resolutions: bugs 9, 12, 14, 19, 20, 29, 30, 34, 36, 102 and 172.
Bugzilla editorial issues: bugs 30, 57, 63, 68, 88, 89, 168, 180, 182, 185, 187.
More clarity between URL namespaces and XML namespaces, particularly at the beginning of paragraphs using the word namespace
More consistency in referring to properties with the namespace, as in "DAV:lockdiscovery", and referring to XML element names in single quotes, e.g. 'allprop' element.
Figure (example) formatting fixes
Bugzilla issues: bugs 24, 37, 39, 43, 45, 27, 25
Replaced references to "non-null state" of resources with more clear language about URLs that are mapped to resources, bug 25. Also added definition of URL/URI mapping. Bug 40.
Bugzilla issues: bug 7, 8, 9, 41, 47, 51, 62, 93, 171, 172. Bugs 28 and 94 were iterated on.
Bugzilla issues: 56, 59, 79, 99, 103, 175, 178. Part of bug 23. Iteration on bug 10.
Iteration on bugs 10, 46 and 47. Bug 11.
Remove "102 Processing" response
Fix bug 46, 105, 107, 120, 140 and 201.
Another stab at bug 12 - relative v. absolute URLs in Multi-Status response hrefs
Fix bug 6, 11, 15, 16, 28, 32, 42, 51, 52, 53, 58, 60, 62, 186, 189, 191, 199, 200
Fix bug 96
Clarify lock intro text on when a client might use another client's lock token - suggestion by Geoff, Nov 15
Removed Force-Authenticate header and instead added an appendix explaining how existing mechanisms might resolve the need of clients to get an authentication challenge (bug 18).
Bug 62, 113, 125, 131, 143, 144, 171, 193
Bug 176, 177, 179, 181, 184, 206, 207, 208
Bug 10, 50, 92, 213, 214, 215
not recommend use of 414 for over-long Destination URI, bug 179
Changes for bug 10, 31, 42, 44, 46, 47, 80, 86, 99, 124, 132, 143, 147, 152, 166, 177, 188, 216, 218
Various changes discussed in conference call, including bug 10, 42, 44, 80, 97, 152.
Bugs 55, 85, 86
Incorporated GULP (Lock model) into document, making a fair number of changes to rationalize the new order of explaining things, keeping text that explains a lock model concept in more detail but removing text that is redundant or inconsistent.
Various bugs including 46, 48, 53, 97, 152, 179, 184, 188, 200, 210, 211, and 225. Moved URL Handling from Multi-Status section to general request and response handling section as it now applies to Destination and If as well as 'href' in Multi-Status. Moved GR&RH section up one level to be the new Section 8.
Bug 53, 184, 210, 213, 217, 221
Further rewriting of URL Handling section. Changes resulting from discussion of empty locked resources and how servers should handle Content-Type in that situation. Bug 48, 179.
Bug 227, 228,
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