👉 Overview
👀 What ?
SELinux (Security-Enhanced Linux) is a Linux kernel security module that provides a mechanism for supporting access control security policies. It is a flexible and robust system for managing access control policies, including mandatory access control (MAC).
🧐 Why ?
SELinux is important as it provides an additional layer of system security. Traditional Linux systems use discretionary access control (DAC), which is based on user ownership and permissions. However, DAC can be bypassed by processes running as root. SELinux implements MAC, which restricts processes based on policy rules, regardless of the user's permissions. This helps to limit the potential damage that can be caused by a compromised system.
⛏️ How ?
To take advantage of SELinux, you first need to ensure it is installed and enabled on your Linux system. You can check this by running the command 'sestatus'. If SELinux is running, you will see the current status and policy being used. SELinux policies are complex and can be difficult to configure correctly. It is recommended to start with a pre-existing policy, such as the targeted policy provided by most Linux distributions, and modify it to suit your needs. Tools such as 'semanage' and 'setsebool' can be used to manage SELinux policies and booleans.
⏳ When ?
SELinux was first introduced by the NSA (National Security Agency) and became part of the Linux kernel in version 2.6, released in December 2003. It has been a standard part of most Linux distributions since then.
⚙️ Technical Explanations
SELinux operates by defining a set of policy rules that dictate what system operations are allowed. These rules are enforced by the Linux kernel. When a process attempts to perform an operation, the kernel checks the policy rules to see if the operation is allowed. If the operation is not allowed, it is blocked and a message is logged. This is a form of mandatory access control, as the policy rules are enforced by the system, not the user. SELinux policies are extremely flexible, allowing for fine-grained control over system operations. They can be used to restrict what files a process can access, what capabilities a process can use, and even what network ports a process can bind to.