InformIT: Mac OS X Unleashed > WebDAVmod

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WebDAV—`mod_dav`

Something that Apple hasn't advertised with Mac OS X is the integration of WebDAV as a native file-sharing format. WebDAV (Distributed Authoring and Versioning) is a relatively new protocol that operates on top of HTTP. What makes this attractive is the fact it doesn't require additional inetd or system daemons to be present.

WebDAV is entirely cross-platform, is integrated into the Windows operating system, and supported natively in software such as Macromedia Dreamweaver as well. Using WebDAV, you can distribute authoring and editing Web sites across a number of different computers and operating systems. Best of all, WebDAV is easy to use and, because it operates through Apache, the same configuration directives you've already seen can apply directly to its setup.

Installing and Configuring WebDAV

You can download the WebDAV Apache module (mod_dav) from www.webdav.org/mod_dav/. Installing WebDAV is an excellent example of a typical Apache module compilation.

First, unarchive and uncompress the software:

[primal:~] jray% tar zxf mod_dav-1.0.2-1.3.6.tar.gz

Next, configure the application. You should use the --with-apxs directive to enable automatic configuration and installation of the Apache module:

[primal:~/mod_dav-1.0.2-1.3.6] jray% ./configure --with-apxs
creating cache ./config.cache
checking for gcc... no
checking for cc... cc
checking whether the C compiler (cc  ) works... yes
checking whether the C compiler (cc  ) is a cross-compiler... no
checking whether we are using GNU C... yes
checking whether cc accepts -g... yes
checking for ranlib... ranlib

Finally, make and install the module:

[primal:~/mod_dav-1.0.2-1.3.6] jray% sudo make install
cc -c   -I/usr/include/httpd -I/usr/include/httpd/xml -g -O2 -DDARWIN -DUSE_HSREGEX

      
    -DUSE_EXPAT -I../lib/expat-lite -g -O3 -pipe-DHARD_SERVER_LIMIT=1024 -DEAPI

      
    -DSHARED_MODULE dav_props.c -o dav_props.o
...
cp libdav.so /usr/libexec/httpd/libdav.so
chmod 755 /usr/libexec/httpd/libdav.so
[activating module `dav' in /private/etc/httpd/httpd.conf]

To finish the configuration and activation of WebDAV service on your Apache server, you need to create a directory that will hold WebDAV lock files and then turn on the service for a particular directory or location.

Use the DAVLockDB directive to set the directory and base filename for WebDAV's lockfiles. This should fall anywhere after the LoadModule/AddModule lines in the /etc/httpd/httpd.conf file:

DAVLockDB /var/tmp/davlock

This example specifies that the directory /var/tmp will be used to hold lock files, and that davlock will be the base filename for the lock files. Be sure to include the base filename, not just a directory name. If the lockfile is not properly set, mod_dav will start, but won't operate correctly.

Now, choose one of the directory or container objects that will support WebDAV service and add the DAV On directive:

<Directory "/Library/WebServer/Documents">
     DAV On
     Options Indexes FollowSymLinks MultiViews
     AllowOverride None
     Order allow,deny
     Allow from all
</Directory>

You should limit access to the DAV services using the same require directive in the standard Apache configuration. WebDAV relies on the HTTP protocol to authenticate users for editing. This means you will need to create a password file just like we did earlier. Unlike the previous example, however, a valid user will be required only when performing a modification to the file system. To create this sort of selective authentication, we'll use the Limit directive. For example, the following configuration file fragment defines an authentication scheme and limits it to the operations that WebDAV uses to add and update files.

AuthType Basic
AuthName "The Poisontooth Webserver"
AuthUserFile /Users/jray/webpasswords
<Limit PUT DELETE PROPPATCH MKCOL COPY MOVE LOCK UNLOCK>
          Require valid-user
</Limit>

To finish things up, just combine the authentication block with the resource that WebDAV support has been enabled (DAV On):

1: <Directory "/Library/WebServer/Documents">
2:      DAV On
3:      Options Indexes FollowSymLinks MultiViews
4:      AllowOverride None
5:      Order allow,deny
6:      Allow from all
7:      AuthType Basic
8:      AuthName "The Poisontooth Webserver"
9:      AuthUserFile /Users/jray/webpasswords
10:     <Limit PUT DELETE PROPPATCH MKCOL COPY MOVE LOCK UNLOCK>
11:          Require valid-user
12:     </Limit>
13: </Directory>

Line 1 sets up the directory to WebDAV enable. This can be a directory that is already defined in the main Apache http.conf or one of the user configuration files.

Line 2 turns on DAV support, and lines 3 through 6 are standard directory security directives—not WebDAV related.

Lines 7 through 9 set up basic HTTP authentication. This will be used to authenticate potential WebDAV clients. Lines 10–12 limit the HTTP authentication to only those actions that would be triggered by a WedDAV client.

There's still one small thing that needs to be adjusted before WebDAV can be used—the permissions on the directory that has DAV support enabled. Because WebDAV is nothing more than an extension to Apache, it has no more user rights than the Apache server process. This means that if Apache can't write to a resource (that is, it isn't owned by www or isn't set to world-writable), WebDAV won't be able to modify the resource either. To make a directory editable using DAV, you must use chown to modify the file and directory ownership. Type chown -R www:admin <directory to DAV-enable> and you're done!

Restart Apache (/usr/sbin/apachectl restart) to begin using WebDAV.

Mounting WebDAV Shares

First, from within a Finder window, use the Go menu to choose Connect to Server (Command+K). The dialog box shown in Figure 27.4 will appear.

Figure 27.4 Use the Connect to Server menu item to connect to WebDAV-enabled servers.

Fill in the URL of the directory with DAV access in the Address field. This should be the Web path to the resource, not the actual file path on the server. In the screenshot shown, the main root directory of the Web server has been enabled, so the URL given is just set to the main Web site URL. When satisfied that your settings are correct, click Connect. You will be prompted for a username and password for the resource. Use the username/password pair defined with htpasswd.

After a few seconds, the remote site should be mounted as if it were a local drive on your computer.

Using WebDAV on Windows

Like Mac OS X, WebDAV is integrated into recent releases of the Windows operating system. To access a WebDAV share from your Linux Web server, you must create a new Network Place.

Double-click My Network Places to open the Network Places window. Next, double-click Add Network Place to start the Network Place wizard, as seen in Figure 27.5.

Figure 27.5 The Network Place connection wizard will help set up a WebDAV resource in Windows.

Fill in the URL of the WebDAV resource, and then click Next. As with Mac OS X, you will be prompted for the username and password that were set using htpasswd. Click Next to finish and mount the resource.

WebDAV support is an integral part of Mac OS X and Windows, and can be used to unite a multiplatform environment for collaboration on Web sites and other projects. In a pinch, WebDAV can even serve as a file server for things other than Web-related files.

That's enough work for now. On to something a bit more entertaining—streaming audio from Apache!

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WebDAV—mod_dav

Installing and Configuring WebDAV

Mounting WebDAV Shares

Using WebDAV on Windows

WebDAV—`mod_dav`