Continuing from the first CentOS Apache configuration article, we now look at some of the other settings in the main httpd.conf file and what they can do.
Concentrating on efficiency and security, this will end our httpd.conf journey (for now).
Default: Not Set
The ServerName is usually a hostname or a FQDN (Fully Qualified Domain Name).
If you set followed the CentOS installing Apache and PHP5 article, you will have already set the ServerName configuration.
If you fail to set the ServerName then on an Apache restart you will see the following warning:
Starting httpd: httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName
If you want happy users and to save traffic, keep this at Off.
Setting this to 'On' will enable DNS lookups so host names can be logged (it performs a reverse DNS check), setting it to 'Double' will not only perform the reverse DNS check it will then check the resulting hostname.
All a bit much and if you desperately need hostname information from your visitors it is advised to use logresolve (located in /usr/bin/logresolve) for this purpose. A small explanation can be found here.
The ServerTokens setting will dictate how much information is sent in the Headers with regard to Apache version and modules in use.
The default (Set as 'OS") would send something like this:
Does this make a difference? Well, yes. If we can suppress that information it will make it harder for someone to find an exploit.
It does not make the actual install any more secure but all someone has to do right now is look for an exploit in CentOS Apache 2.2.3 and so on. Why make it easy for them?
The options are (with example outputs):
Apache/2.2.3 (CentOS) DAV/2 PHP/5.1.6 mod_ssl/2.2.3 OpenSSL/0.9.8b
It's up to you what level of info you want to give out. I prefer setting ServerTokens to Prod.
Server generated pages, such as 404 pages or directory listings, can contain a footer line which includes server information and can include the ServerAdmin email address.
If you navigate to your Slice IP address and a non-existent page:
You will see a 404 Page not found page with the footer information:
Note the image shown has ServerTokens set to 'Prod' so little information is shown in the footer.
The options are:
Off: Produces no footer
On: Produces footer information (at a level defined by the ServerTokens setting)
Email: Adds an email link to the information (level defined by the ServerTokens setting)
After each change to the httpd.conf file, you will need to reload Apache for the settings to take effect:
sudo /etc/init.d/httpd reload
Some simple steps in this article but ones which I believe are very useful and aid in increasing the efficiency of your Slice and assist in the overall security effort on your Slice.