Book Image

SELinux System Administration. - Second Edition

Book Image

SELinux System Administration. - Second Edition

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

SELinux file context expressions


When we think that the context of a file is wrong, we need to correct the context. SELinux offers several methods to do so, and some distributions even add in more. We can use tools such as chcon, restorecon (together with semanage), setfiles, rlpkg (Gentoo), and fixfiles (RHEL). Of course, we could also use the setfattr command, but that would be the least user-friendly approach for setting contexts.

Using context expressions

In the SELinux policy, there is a list of regular expressions that informs the SELinux utilities and libraries what the context of a file (or other file system resource) should be. Though this expression list is not enforced on the system, it is meant for administrators to see whether a context is correct, and for tools that need to reset contexts to what they are supposed to be. The list itself is stored on the file system in /etc/selinux/targeted/contexts/files in the file_contexts.* files.

As an administrator, we can query parts of...