Book Image

SELinux System Administration - Second Edition

By : Sven Vermeulen
Book Image

SELinux System Administration - Second Edition

By: Sven Vermeulen

Overview of this book

Do you have the crucial job of protecting your private and company systems from malicious attacks and undefined application behavior? Are you looking to secure your Linux systems with improved access controls? Look no further, intrepid administrator! This book will show you how to enhance your system’s secure state across Linux distributions, helping you keep application vulnerabilities at bay. This book covers the core SELinux concepts and shows you how to leverage SELinux to improve the protection measures of a Linux system. You will learn the SELinux fundamentals and all of SELinux’s configuration handles including conditional policies, constraints, policy types, and audit capabilities. These topics are paired with genuine examples of situations and issues you may come across as an administrator. In addition, you will learn how to further harden the virtualization offering of both libvirt (sVirt) and Docker through SELinux. By the end of the book you will know how SELinux works and how you can tune it to meet your needs.
Table of Contents (16 chapters)
SELinux System Administration - Second Edition
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface

Limiting the scope of transitions


For security reasons, Linux systems can reduce the ability for processes to gain elevated privileges under certain situations or provide additional constraints to reduce the likelihood of vulnerabilities to be exploitable. The SELinux developers too honor these situations.

Sanitizing environments on transition

When a higher-privileged command is executed (be it a setuid application or one where capabilities are added to the session), the GNU C Library (glibc) will sanitize the environment. This means that a set of sensitive environment variables is discarded to make sure that attackers or malicious persons or applications cannot influence the session.

This secure execution is controlled through an Executable and Linkable Format (ELF) auxiliary vector called AT_SECURE. When set, environment variables such as LD_PRELOAD, LD_AUDIT, LD_DEBUG, TMPDIR, and NLSPATH are removed from the session.

SELinux will force this sanitation on domain transitions as well, ensuring...