Apache: The Definitive Guide, 3rd Edition

Protect server files by default

One aspect of Apache, which is occasionally misunderstood, is the feature of default access. That is, unless you take steps to change it, if the server can find its way to a file through normal URL mapping rules, it can serve it to clients. For instance, consider the following example:

1. # cd /; ln -s / public_html

2. Accessing http://localhost/~root/

   This would allow clients to walk through the entire filesystem. To work around this, add the following block to your server’s configuration:

   <Directory />
       Order Deny,Allow
       Deny from all
   </Directory>

This will forbid default access to filesystem locations. Add appropriate <Directory> blocks to allow access only in those areas you wish. For example:

<Directory /usr/users/*/public_html>
    Order Deny,Allow
    Allow from all
</Directory>
<Directory /usr/local/httpd>
    Order Deny,Allow
    Allow from all
</Directory>

Pay particular attention to the interactions of <Location> and <Directory> directives; for instance, even if <Directory /> denies access, a <Location /> directive might overturn it.

Also be wary of playing games with the UserDir directive; setting it to something like ./ would have the same effect, for root, as the first example earlier. If you are using Apache 1.3 or above, we strongly recommend that you include the following line in your server configuration files:

UserDir disabled root

Tip

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