Apache Module mod_dav
Description: | Distributed Authoring and Versioning (WebDAV) functionality |
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Status: | Extension |
ModuleIdentifier: | dav_module |
SourceFile: | 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.
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" <Directory "/usr/local/apache2/htdocs/foo"> Require all granted Dav On AuthType Basic AuthName DAV AuthUserFile "user.passwd" <LimitExcept GET POST OPTIONS> Require user admin </LimitExcept> </Directory>
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 |
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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 |
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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 |
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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>
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