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

Linux netfilter and SECMARK support


The approach with TCP and UDP ports has a few downsides. One of them is that there is no knowledge of the target host, so you cannot govern where an application can connect to. There is also no way of limiting daemons from binding on any interface: in a multi-homed situation, we might want to make sure that a daemon only binds on the interface facing the internal network and not the Internet-facing one, or vice versa.

In the past, SELinux allowed support for this binding issue through the interface and node labels: a domain could only be allowed to bind to one interface and not on any other, or even on a particular address (referred to as the node). This support had its flaws though, and has been largely deprecated in favor of SECMARK filtering.

Introducing netfilter

Before explaining SECMARK and how administrators can control it, let's first take a quick look at Linux's netfilter subsystem, which is the de facto standard for local firewall capabilities on...