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 users and roles


Within SELinux systems, the moment a user logs in, the login system checks which SELinux user his or her login is mapped to. Then, when a SELinux user is found, the system looks up the role and domain that the user should be in and sets that as the user's context.

Listing SELinux user mappings

When logged in to the system, we can use id -Z to obtain the current SELinux context. For many users, this context will be unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023, regardless of their username. If not that, it will be a context based on one of sysadm_u, staff_u, or user_u. This is because the majority of Linux distributions will only provide a limited set of SELinux users by default, aligned with the SELinux roles that they support.

When the login process is triggered, a local definition file will be checked to see which SELinux user is mapped to the Linux account. Let's take a look at the existing login mappings using semanage login -l. The following output is the...