Book Image

SELinux System Administration

By : Sven Vermeulen
Book Image

SELinux System Administration

By: Sven Vermeulen

Overview of this book

NSA Security-Enhanced Linux (SELinux) is a set of patches and added utilities to the Linux kernel to incorporate a strong, flexible, mandatory access control architecture into the major subsystems of the kernel. With its fine-grained yet flexible approach, it is no wonder Linux distributions are firing up SELinux as a default security measure. SELinux System Administration covers the majority of SELinux features through a mix of real-life scenarios, descriptions, and examples. Everything an administrator needs to further tune SELinux to suit their needs are present in this book. This book touches on various SELinux topics, guiding you through the configuration of SELinux contexts, definitions, and the assignment of SELinux roles, and finishes up with policy enhancements. All of SELinux's configuration handles, be they conditional policies, constraints, policy types, or audit capabilities, are covered in this book with genuine examples that administrators might come across. By the end, SELinux System Administration will have taught you how to configure your Linux system to be more secure, powered by a formidable mandatory access control.
Table of Contents (13 chapters)

Integrating with Linux netfilter


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 a domain 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 on one interface and not on any other, or even on a particular address (referred to as the node). This support has been deprecated for the regular network access control support because it had a flaw; there was no link between host or interface binding information and the connect or bind permission towards a particular socket.

Consider the example of a web server on a DMZ system. The web server is allowed to receive...