Security-enhanced Linux is a patch of the Linux® kernel and a
number of utilities with enhanced security functionality designed
to add mandatory access controls to Linux. The Security-enhanced
Linux kernel contains new architectural components originally
developed to improve the security of the Flask operating system.
These architectural components provide general support for the
enforcement of many kinds of mandatory access control policies,
including those based on the concepts of Type Enforcement®,
Role-based Access Control, and Multi-level Security.

libselinux provides an API for SELinux applications to get and set
process and file security contexts and to obtain security policy
decisions. Required for any applications that use the SELinux API.