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CIS Ubuntu 14.04 LTS - 1.4.1 Ensure permissions on bootloader config are configured

DevOps & Security
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Verify that permissions on grub bootloader configuration are restricted to root only

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_14.04_LTS_Benchmark_v2.1.0/cis-ubuntu1404-v210-1-4-1/SKILL.md

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1.4.1 Ensure permissions on bootloader config are configured (Scored)

Profile Applicability

  • Level 1 - Server
  • Level 1 - Workstation

Description

The grub configuration file contains information on boot settings and passwords for unlocking boot options. The grub configuration is usually grub.cfg stored in /boot/grub.

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

Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other:

stat /boot/grub/grub.cfg

Expected Result

Access: (0400/-r--------) Uid: ( 0/ root) Gid: ( 0/ root)

Remediation

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

chown root:root /boot/grub/grub.cfg
chmod og-rwx /boot/grub/grub.cfg

Default Value

Not applicable.

Notes

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

References

  • CIS Controls: 5.1 Minimize And Sparingly Use Administrative Privileges

Profile

  • Level 1 - Server
  • Level 1 - Workstation