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SELinux Administration, Part II
By: Pax Dickinson

Policy booleans are sections of policy that can be switched on or off, providing a basic level of policy configurability at runtime without requiring the recompilation of the entire security policy. For example, you might be running a webmail application on your server that requires the webserver process to be able to connect to your mail server ports and read mail files out of user's home directories. Rather than adding those permissions to the security policy where they would reduce security for those not running webmail, a policy developer would create a boolean that the local administrator could enable only if it is required. This helps maintain a high level of security and follows the principle of least privilege.

To view a list of the policy booleans in your running policy and their current states, use the sestatus command. This command will list your current enforcing mode and the enforcing mode from the /etc/selinux/config file among other information, and a list of all policy booleans and whether they are active or inactive.

You can view the current status of a single boolean by using the command getsebool and passing it the name of the boolean you want to view the state of. Booleans are set using the setsebool command, and passing it the name of the boolean you want to set followed by a 1 or 0 to set the boolean active or inactive respectively.

Some sample booleans from the EnGarde Secure Linux SELinux policy are httpd_webmail and user_ping. The httpd_webmail boolean is used for the exact situation used as an example above, while the user_ping boolean determines whether or not regular users are able to send ping packets over the network. Booleans can be as simple as a single allow statement, or can enable or disable large swathes of the policy depending on their purpose.

Our SELinux journey is almost done. Next time, we'll discuss policy development basics and see how we can troubleshoot policy denials and write new SELinux policy or modify existing policy to allow our SELinux system to get its jobs done while maintaining a high level of security. Until then, farewell and remember to stay secure.

Read Entire Article:
http://www.linuxsecurity.com/content/view/120700/49/

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