SELinux Notes

SELinux is enabled by default on Centos 7 and on RHEL. It's a good thing to enable for internet-facing servers. It makes it far, far more complex to run a web server.

References:

• https://wiki.centos.org/HowTos/SELinux
• https://wiki.gentoo.org/wiki/SELinux/Tutorials/What_is_this_unconfined_thingie_and_tell_me_about_attributes
• https://stackoverflow.com/questions/5326531/php-warning-unknown-failed-to-open-stream
• https://wiki.centos.org/HowTos/SELinux
• https://www.lisenet.com/2016/advanced-apache-configuration-with-selinux-on-rhel-7/

Problem: apache can't access the files

   sudo /sbin/restorecon -R /var/www

   setsebool -P httpd_read_user_content 1

Running a web server:

If you can't run PHP, you may have the files in the wrong SELinux security context. You can change the security

1. Use ls -lZ /var/www/html/xxx to check the security context
2. You can give the web server read/write access to the files with:

   chcon -R -t httpd_sys_rw_content_t /var/www/html/xxx

CGI scripts under SELinux

You can see the selinux policy for cgi-bin with:

   $ semanage fcontext --list | grep cgi-bin

You can give the script the SELinux context with:

   $ chcon -t httpd_sys_script_exec_t /var/www/html/script.cgi

Check the file's SELinux attributes with `ls -laZ`:

   $ ls -laZ /var/www/html/script.cgi

References:

• https://serverfault.com/questions/691501/apache-permission-denied-exec-of-var-www-html-cgi-test-first-pl-failed

Disabling SELinux

• https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Security-Enhanced_Linux/sect-Security-Enhanced_Linux-Working_with_SELinux-Changing_SELinux_Modes.html#sect-Security-Enhanced_Linux-Enabling_and_Disabling_SELinux-Permissive_Mode

• edit /etc/selinux/config and change SELINUX from 'enforcing' to 'permissive'