Apache HTTP Server Version 2.0
Apache Module mod_dav
| Description: | Distributed Authoring and Versioning (WebDAV) functionality |
|---|---|
| Status: | Extension |
| Module Identifier: | dav_module |
| Source File: | mod_dav.c |
Summary
This module provides class 1 and class 2 WebDAV ('Web-based Distributed Authoring and Versioning') functionality for Apache. This extension to the HTTP protocol allows creating, moving, copying, and deleting resources and collections on a remote web server.
See also
Enabling WebDAV
To enable mod_dav, add the following to a
container in your httpd.conf file:
Dav On
This enables the DAV file system provider, which is implemented
by the mod_dav_fs module. Therefore, that module
must be compiled into the server or loaded at runtime using the
LoadModule directive.
In addition, a location for the DAV lock database must be
specified in the global section of your httpd.conf
file using the DavLockDB
directive:
DavLockDB /usr/local/apache2/var/DavLock
The directory containing the lock database file must be
writable by the User
and Group under which
Apache is running.
You may wish to add a <Limit> clause inside the <Location> directive to limit access to
DAV-enabled locations. If you want to set the maximum amount of
bytes that a DAV client can send at one request, you have to use
the LimitXMLRequestBody
directive. The "normal" LimitRequestBody directive has no effect on DAV
requests.
Full Example
DavLockDB /usr/local/apache2/var/DavLock
<Location /foo>
Dav On
AuthType Basic
AuthName DAV
AuthUserFile user.passwd
<LimitExcept GET OPTIONS>
require user admin
</LimitExcept>
</Location>
mod_dav is a descendent of Greg Stein's mod_dav for Apache 1.3. More
information about the module is available from that site.
Security Issues
Since DAV access methods allow remote clients to manipulate
files on the server, you must take particular care to assure that
your server is secure before enabling mod_dav.
Any location on the server where DAV is enabled should be
protected by authentication. The use of HTTP Basic Authentication
is not recommended. You should use at least HTTP Digest
Authentication, which is provided by the
mod_auth_digest module. Nearly all WebDAV clients
support this authentication method. An alternative is Basic
Authentication over an SSL enabled
connection.
In order for mod_dav to manage files, it must
be able to write to the directories and files under its control
using the User and
Group under which
Apache is running. New files created will also be owned by this
User and Group. For this reason, it is
important to control access to this account. The DAV repository
is considered private to Apache; modifying files outside of Apache
(for example using FTP or filesystem-level tools) should not be
allowed.
mod_dav may be subject to various kinds of
denial-of-service attacks. The LimitXMLRequestBody directive can be
used to limit the amount of memory consumed in parsing large DAV
requests. The DavDepthInfinity directive can be
used to prevent PROPFIND requests on a very large
repository from consuming large amounts of memory. Another
possible denial-of-service attack involves a client simply filling
up all available disk space with many large files. There is no
direct way to prevent this in Apache, so you should avoid giving
DAV access to untrusted users.
Complex Configurations
One common request is to use mod_dav to
manipulate dynamic files (PHP scripts, CGI scripts, etc). This is
difficult because a GET request will always run the
script, rather than downloading its contents. One way to avoid
this is to map two different URLs to the content, one of which
will run the script, and one of which will allow it to be
downloaded and manipulated with DAV.
Alias /phparea /home/gstein/php_files
Alias /php-source /home/gstein/php_files
<Location /php-source>
DAV On
ForceType text/plain
</Location>
With this setup, http://example.com/phparea can be
used to access the output of the PHP scripts, and
http://example.com/php-source can be used with a DAV
client to manipulate them.
Dav Directive
| Description: | Enable WebDAV HTTP methods |
|---|---|
| Syntax: | Dav On|Off|provider-name |
| Default: | Dav Off |
| Context: | directory |
| Status: | Extension |
| Module: | mod_dav |
Use the Dav directive to enable the
WebDAV HTTP methods for the given container:
<Location /foo>
Dav On
</Location>
The value On is actually an alias for the default
provider filesystem which is served by the mod_dav_fs module. Note, that once you have DAV enabled
for some location, it cannot be disabled for sublocations.
For a complete configuration example have a look at the section above.
DavDepthInfinity Directive
| Description: | Allow PROPFIND, Depth: Infinity requests |
|---|---|
| Syntax: | DavDepthInfinity on|off |
| Default: | DavDepthInfinity off |
| Context: | server config, virtual host, directory |
| Status: | Extension |
| Module: | mod_dav |
Use the DavDepthInfinity directive to
allow the processing of PROPFIND requests containing the
header 'Depth: Infinity'. Because this type of request could constitute
a denial-of-service attack, by default it is not allowed.
DavMinTimeout Directive
| Description: | Minimum amount of time the server holds a lock on a DAV resource |
|---|---|
| Syntax: | DavMinTimeout seconds |
| Default: | DavMinTimeout 0 |
| Context: | server config, virtual host, directory |
| Status: | Extension |
| Module: | mod_dav |
When a client requests a DAV resource lock, it can also specify a time when the lock will be automatically removed by the server. This value is only a request, and the server can ignore it or inform the client of an arbitrary value.
Use the DavMinTimeout directive to specify, in
seconds, the minimum lock timeout to return to a client.
Microsoft Web Folders defaults to a timeout of 120 seconds; the
DavMinTimeout can override this to a higher value
(like 600 seconds) to reduce the chance of the client losing
the lock due to network latency.
Example
<Location /MSWord>
DavMinTimeout 600
</Location>