Copied from “Mac OS X Panther Hacks” from O’Reilly, hack #69

WebDAV (Web-based Distributed Authoring and Versioning, also called DAV) is a set of extensions to HTTP/1.1 that allows you to edit documents on remote web server. DAV provides support for:

  • Editing: Creating, updating, deleting
  • Properties: Title, author, publication date, and so on
  • Collections: Analogous to a filesystem’s directory or Desktop folder
  • Locking: Prevents the confusion and data corruption caused by two or more people editing the same content at the same time

WebDAV is platform-independent, in terms of both client and server. This means that Macintosh, Unix, and Windows users can collaborate on web content without all the usual conversion problems. Furthermore, it doesn’t matter whether your documents are hosted on an Apache or Microsoft IIS server.

WebDAV is software agnostic. As long as your web-authoring tools are DAV-compliant, the particular product you’re using makes little difference. It is (at least should be) seamless. Decause DAV is simply a set of extensions to HTTP, it’s easy for companies to build support into any product that already understands the Web. And, since DAV rides on top of HTTP, firewalls tend not to get in the way of accessing your web content remotely.

WebDAV makes use of the standard authorization and authentication methods built right into every web server. In the same manner as one restricts access to a portion (a file, folder, or entire site) of one’s web site to a particular set of usrs or machines, so too can one finely tune WebDAV access to resources.

Best of all, WebDAV is built into the Apache web server that is part of Mac OS X.

Configuring WebDAV in Apache

Open the Apcache server’s main configuration file, /etc/httpd/httpd.conf, for editing. You’ll neecd to authenticate yourself as an administrator by using sudo:

$ sudo pico /etc/httpd/httpd.conf

You’ll need to hunt down two lines in your Apache configuration and uncomment them. These are the two lines to look for in /etc/httpd/httpd.conf:

# LoadModule dav_module libexec/httpd/
# AddModule mod_dav.c

Since these lines are commented out by default, we’ll have to uncomment them in order to make WebDAV functional. Do so, and the lines should now look like this:

LoadModule dav_module libexec/httpd/
AddModule mod_dav.c

Once the WebDAV module is activated, you’ll need to add a configuration directive to enable a DAV share. Zoom down to the end of the file and add the following lines:

  DAVLockDB /etc/httpd/dav/DAVLock
  DAVMinTimeout 600
  <Location /dav/>
     DAV On
     AuthType Basic
     AuthName "WebDAV Restricted"
     AuthUserFile /etc/httpd/dav/.passwd
     <LimitExcept GET HEAD OPTIONS>
         Require valid-user

The first line sets up a database file that WebDAV uses to track who’s editing which file. It locks a file to prevent something dangerous from happening, such as two people trying to update it at once. The second line tells the web server not to wait forever if the remote computer loses the connection with it. The <Location> tags set the context of the WebDAV settings to the /dav directory, which we will set up under document root.

We’re using AuthTypeBasic security, which requires a username and password to make modifications. We’ll store the password in a file called /Library/WebServer/.passwd, and the required username is webdav.

The <LimitExcept> directive gives us some protection from malicious intent. First, it locks down all the actions that can be performed on WebDAV files, except those actions that are read-only. Second, it limits the write privileges to one user, named webdav. The only ability this user has on the system is to write files in this directioy.

Setting up directories

First, you need to set up the realm of WebDAV documents. Based on what we put in the configuration file, this will be in a subdirectory of the document root called /dav (that’s /Library/WebServer/Documents/dav). You’ll need to create that directory yourself and change the permissions and ownership to that the web server can write to it:

$ sudo mkdir /Library/WebServer/Documents/dav
$ sudo chgrp www /Library/WebServer/Documents/dav
$ sudo chmod 775 /Library/WebServer/Documents/dav

Next, you need to find a place for the WebDAV lock database file. For lack of a better place, I created a directory alongside the httpd.conf configuration file, /etc/httpd/dav. Again, set the permissions so that the server can write files here:

$ sudo mkdir /etc/httpd/dav
$ sudo chgrp www /etc/httpd/dav
$ sudo chmod 775 /etc/httpd/dav

Creating users

While our configuration specifies that only valid users are allowed to alter the contents of the /dav directory via WebDAV, we haven’t yet created said users. Will’ll do so now.

Don’t use an existing username and password. A malicious hacker sniffing your communications can grab that username and use it to sneak inside your system. The username we will create will be limited to WebDAV files only, which will be useless to a would-be intruder.

First, create a password file by using the htpasswd utility. (Again, to keep everything related to DAV together, I used /etc/httpd/dav/.) You’ll simultaneously create a user account and a password for webdav. You’ll be prompted for a password unique (don’t use one that you use elsewhere), because of the basic authentication risk I mentioned earlier:

$ sudo htpasswd -c /etc/httpd/dav.passwd webdav
New password:
Re-type new password:
Adding password for user webdav

See also

WebDAV Resources (