Linux Bible, 9th Edition

Enhancing Linux Security with SELinux

IN THIS CHAPTER

Learning about SELinux benefits

Learning how SELinux works

Setting up SELinux

Fixing problems with SELinux

Getting additional information on SELinux

Security Enhanced Linux (SELinux) was developed by the National Security Agency (NSA) along with other security research organizations, such as Secure Computing Corporation (SCC). SELinux was released to the open source community in 2000 and became popular when Red Hat included SELinux in its Linux distributions. Now, SELinux is used by many organizations and is widely available.

Understanding SELinux Benefits

SELinux is a security enhancement module deployed on top of Linux. It provides additional security measures, is included by default, and is set to be in Enforcing mode in RHEL and Fedora.

SELinux provides improved security on the Linux system via Role Based Access Controls (RBAC) on subjects and objects (aka processes and resources). “Traditional” Linux security uses Discretionary Access Controls (DAC).

SELinux is not a replacement for DAC. Instead, it is an additional security layer.

• DAC rules are still used when using SELinux.
• DAC rules are checked first, and if access is allowed, then SELinux policies are checked.
• If DAC rules deny access, SELinux policies are not reviewed.

If a user tries to execute a file that he does not have execute access to (rw-), the “traditional” ...