Security Handbook/Kernel security

This section is on securing the system's kernel.

Removing functionality

The basic rule when configuring the kernel is to remove everything that you do not need. This will not only create a small kernel but also remove the vulnerabilities that may lie inside drivers and other features.

Also consider turning off loadable module support (CONFIG_MODULES=n). Even though it is possible to add root kits without this features, it does make it harder for normal attackers to install root kits via kernel modules. For further information see the dedicated kernel modules page.

An alternative to turning the loadable modules off completely is forcing the kernel to load only digitally signed modules. See the dedicated page.

Kerneli

Kerneli is a patch that adds encryption to the existing kernel. By patching your kernel you will get new options such as cryptographic ciphers, digest algorithms and cryptographic loop filters.

See also

• Kernel Modules — object files that contain code to extend the kernel of an operating system.
• Signed kernel module support — allows further hardening of the system by disallowing unsigned kernel modules, or kernel modules signed with the wrong key, to be loaded.

External resources

• The OpenWall Project
• Rule Set Based Access Control (RSBAC)
• NSA's security enhanced kernel (SE Linux)