BOOT-5122 - Set boot loader password

(Boot)

This information is provided as part of the Lynis community project. It is related to Lynis control BOOT-5122 and should be considered as-is and without guarantees. Any advice and commands should be tested before implementing them in production environments.

Description

By default anyone with physical access to the machine can load alternative software or another operating system during the boot phase. Configure a password in grub to prevent this possibility.

How to solve

The boot loader is started at the beginning of the boot cycle, and enables the user to select what operating system to start. Normally one entry is selected as default, with a timer of a few seconds. When this timer expires, this default entry is selected, trigger the start of the related operating system.

Often the boot loader contains the primary operating system and several fallback options. The same operating system with a previous Linux kernel version is a common option to see in such configuration. Another option is a rescue image, to perform emergency maintenance when the system does not longer boot.

Although a rescue option or fallback version are great during emergency, they can become a weakness. Evildoers with physical access to the system could use this option to reset the root password. Especially for notebooks this is a risk, as it is common that people are in the physical presence of such device. When hosting systems in a shared data center, this could also be a situation in which it makes sense to set a password on the boot loader.

Additional resources

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Lynis is a technical security auditing tool for Unix flavors like Linux, macOS, AIX, Solaris, and *BSD. It is open source software and free to use. Typical usage include system hardening, compliance testing, and vulnerability scanning. The project has an active community, including development via GitHub.

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