Book Image

SELinux System Administration, Third Edition - Third Edition

By : Sven Vermeulen
Book Image

SELinux System Administration, Third Edition - Third Edition

By: Sven Vermeulen

Overview of this book

Linux is a dominant player in many organizations and in the cloud. Securing the Linux environment is extremely important for any organization, and Security-Enhanced Linux (SELinux) acts as an additional layer to Linux system security. SELinux System Administration covers basic SELinux concepts and shows you how to enhance Linux system protection measures. You will get to grips with SELinux and understand how it is integrated. As you progress, you’ll get hands-on experience of tuning and configuring SELinux and integrating it into day-to-day administration tasks such as user management, network management, and application maintenance. Platforms such as Kubernetes, system services like systemd, and virtualization solutions like libvirt and Xen, all of which offer SELinux-specific controls, will be explained effectively so that you understand how to apply and configure SELinux within these applications. If applications do not exert the expected behavior, you’ll learn how to fine-tune policies to securely host these applications. In case no policies exist, the book will guide you through developing custom policies on your own. By the end of this Linux book, you’ll be able to harden any Linux system using SELinux to suit your needs and fine-tune existing policies and develop custom ones to protect any app and service running on your Linux systems.
Table of Contents (22 chapters)
1
Section 1: Using SELinux
8
Section 2: SELinux-Aware Platforms
14
Section 3: Policy Management

SELinux and PAM

With all the information about SELinux users and roles, we have not touched upon how exactly applications or services create and assign an SELinux context to a user. As mentioned earlier on, this is coordinated through the use of Linux's PAM services.

Assigning contexts through PAM

End users log in to a Linux system through either a login process (triggered through a getty process), a networked service (for example, the OpenSSH daemon), or through a graphical login manager (xdm, kdm, gdm, slim, and so on).

These services are responsible for switching our effective user ID (upon successful authentication, of course) so that we are not active on the system as the root user. For SELinux systems, these processes also need to switch the SELinux user (and role) accordingly, as otherwise, the context will be inherited from the service, which is obviously wrong for any interactive session.

In theory, all these applications can be made fully SELinux aware, linking...