cis-ubuntu2004-v300-1-4-2

DevOps & Security

Ensure access to bootloader config is configured

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_20.04_LTS_Benchmark_v3.0.0/cis-ubuntu2004-v300-1-4-2/SKILL.md

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1.4.2 Ensure access to bootloader config is configured (Automated)

Profile

Level 1 - Server
Level 1 - Workstation

Description

The grub configuration file contains information on boot settings and passwords for unlocking boot options.

Rationale

Setting the permissions to read and write for root only prevents non-root users from seeing the boot parameters or changing them. Non-root users who read the boot parameters may be able to identify weaknesses in security upon boot and be able to exploit them.

Audit Procedure

Command Line

Run the following command and verify Uid and Gid are both 0/root and Access is 0600 or more restrictive:

# stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /boot/grub/grub.cfg

Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root)

Expected Result

Access should be 0600 or more restrictive, Uid and Gid should both be 0/root.

Remediation

Command Line

Run the following commands to set permissions on your grub configuration:

# chown root:root /boot/grub/grub.cfg
# chmod u-x,go-rwx /boot/grub/grub.cfg

Default Value

Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)

References

NIST SP 800-53 Rev. 5: AC-3

Additional Information

This recommendation is designed around the grub bootloader, if LILO or another bootloader is in use in your environment enact equivalent settings.

Replace /boot/grub/grub.cfg with the appropriate grub configuration file for your environment.

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	3.3 Configure Data Access Control Lists	*	*	*
v7	14.6 Protect Information through Access Control Lists	*	*	*

MITRE ATT&CK Mappings: T1542, T1542.000 | TA0005, TA0007 | M1022