Improve Apache Web Server Security: Use ServerTokens and ServerSignature to Disable Header

When Apache HTTPD web server generates any web pages or error pages, some important information about the version and other details implemented on the system are displayed in th web site server header. For example, the information text may be like this:

Server: Apache/1.3.37 (Unix) mod_auth_passthrough/1.8 mod_log_bytes/1.2 mod_bwlimited/1.4 FrontPage/5.0.2.2635.SR1.2 mod_ssl/2.8.28 OpenSSL/0.9.7a PHP-CGI/0.1b

Server: Apache/2.0.53 (Ubuntu) PHP/4.3.10-10ubuntu4 Server at xx.xx.xx.xx Port 80

The line in the server header expose important version and variant information about the Linux operating system and Apache software used on the machine, indirectly expose the possible security holes that are existed to the hackers, or at least make malicious attackers easier to identify your system for available attack points.

To ensure that the Apache HTTP web server does not broadcast this message to the whole world publicly and fix possible security issue, modify these two directives ServerTokes and ServerSignature in httpd.conf configuration file.

1. Login as root user or perform a sudo to the web server.
2. Open and edit httpd.conf or apache2.conf (in Apache 2) with vi or other text editor. The Apache configuration normally located in /etc/httpd/conf/ or /etc/apache2/ or /etc/apache/ (for Apache1.3) depending on which Unix you’re using.
3. Locate the line with ServerTokens. You can perform a search by typing “/ServerTokes” and hit Enter.
4. In Apache 1.3, you will likely to see a line starts with #ServerTokes Full In this case, remove or delete the # character (by pressing d key). Also modify the Full to become Prod (press r key to replace one character, or R to replace multiple characters), so that the line becomes ServerTokens Prod. In Apache 2.0 or 2.2, the line normally does not exist. So the search will fail. In this case, go to the bottom of config file, and add the new line with the following text. You can add new line by pressing o key.

   ServerTokens Prod

5. Next, search for ServerSignature. In Apache13, the line should just above the line of ServerTokens. Edit the line so that it looks like this, and in Apache2 which doesn’t already have this line, add in at new one.

   ServerSignature Off

6. By now the Apache configuration file should have this two directives set as below:

   ServerSignature Off
   ServerTokens Prod

   The first line “ServerSignature Off” instructs Apache not to display a trailing footer line under server-generated documents (error messages, mod_proxy ftp directory listings, mod_info output, and etc) which displays server version number, ServerName of the serving virtual host, email setting, and creates a “mailto:” reference to the ServerAdmin of the referenced document.

   The second line “ServerTokens Prod” configures Apache to return only Apache as product in the server response header on very page request, suppressing OS, major and minor version info.

7. Save and close the config file by pressing Shift-Colon, and then type wq keys, and hit Enter.
8. Restart Apache. Typical command is service httpd restart or /etc/init.d/apache2 restart.
9. Now, you will get only the Apache in the server response header:

   Server: Apache

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This entry was posted on Sunday, July 22nd, 2007 at 3:31 am and is filed under Webmaster Resources. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.