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cis-ubuntu2004-v300-1-1-2-6-1

DevOps & Security
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Ensure separate partition exists for /var/log

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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-v300-1-1-2-6-1/SKILL.md

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Ensure separate partition exists for /var/log

Profile

Level 2 - Server, Level 2 - Workstation, Assessment: Automated

Description

The /var/log directory is used by system services to store log data.

Rationale

The default installation only creates a single / partition. Since the /var/log directory contains log files which can grow quite large, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system as a whole.

Configuring /var/log as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attackers ability to create exploits on the system. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options.

As /var/log contains log files, care should be taken to ensure the security and integrity of the data and mount point.

Impact

Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing, or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations.

Audit Procedure

Command Line

Run the following command and verify output shows /var/log is mounted:

# findmnt -kn /var/log

Example output:

/var/log /dev/sdb ext4   rw,nosuid,nodev,noexec,relatime,seclabel

Expected Result

/var/log should be mounted as a separate partition.

Remediation

Command Line

For new installations, during installation create a custom partition setup and specify a separate partition for /var/log. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate.

Default Value

Not configured by default.

Additional Information

When modifying /var/log it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multiuser mode.

References

  1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/
  2. NIST SP 800-53 Rev. 5:: CM-6 b CM-7
  3. NIST SP 800-53A :: CM-6.1 (iv)
  4. RHEL 8 STIG Vul ID: V-230293
  5. RHEL 8 STIG Rule ID: SV-230293r902720

CIS Controls

v8 - 8.3 Ensure Adequate Audit Log Storage (IG 1, IG 2, IG 3) v7 - 6.4 Ensure adequate storage for logs (IG 2, IG 3)

MITRE ATT&CK Mappings: T1499, T1499.001 | TA0005 | M1022