cis-ubuntu2004-v300-6-3-3-14

DevOps & Security

Ensure events that modify the system's Mandatory Access Controls are collected

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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-v300-6-3-3-14/SKILL.md

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6.3.3.14 Ensure events that modify the system's Mandatory Access Controls are collected (Automated)

Profile

Level 2 - Server
Level 2 - Workstation

Description

Monitor AppArmor, an implementation of mandatory access controls. The parameters below monitor any write access (potential additional, deletion or modification of files in the directory) or attribute changes to the /etc/apparmor/ and /etc/apparmor.d/ directories.

Note: If a different Mandatory Access Control method is used, changes to the corresponding directories should be audited.

Rationale

Changes to files in the /etc/apparmor/ and /etc/apparmor.d/ directories could indicate that an unauthorized user is attempting to modify access controls and change security contexts, leading to a compromise of the system.

Audit Procedure

Command Line

On disk configuration - Run the following command to check the on disk rules:

# awk '/^ *-w/ \
&&(/\/etc\/apparmor/ \
  ||/\/etc\/apparmor.d/) \
&&/ +-p *wa/ \
&&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules

Verify the output matches:

-w /etc/apparmor/ -p wa -k MAC-policy
-w /etc/apparmor.d/ -p wa -k MAC-policy

Running configuration - Run the following command to check loaded rules:

# auditctl -l | awk '/^ *-w/ \
&&(/\/etc\/apparmor/ \
  ||/\/etc\/apparmor.d/) \
&&/ +-p *wa/ \
&&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)'

Verify the output matches:

-w /etc/apparmor/ -p wa -k MAC-policy
-w /etc/apparmor.d/ -p wa -k MAC-policy

Expected Result

Both on disk and running configuration should show MAC-policy audit rules.

Remediation

Command Line

Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's Mandatory Access Controls.

Example:

# printf "
-w /etc/apparmor/ -p wa -k MAC-policy
-w /etc/apparmor.d/ -p wa -k MAC-policy
" >> /etc/audit/rules.d/50-MAC-policy.rules

Merge and load the rules into active configuration:

# augenrules --load

Check if reboot is required:

# if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi

References

NIST SP 800-53 Rev. 5: AU-3, CM-6

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	8.5 Collect Detailed Audit Logs		X	X
v7	5.5 Implement Automated Configuration Monitoring Systems		X	X

MITRE ATT&CK Mappings: T1562, T1562.006 / TA0004 / M1022