cis-ubuntu1604-v200-1-1-4

name	cis-ubuntu1604-v200-1-1-4
description	Ensure nosuid option set on /tmp partition
category	cis-storage
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","filesystem","tmp","nosuid","mount-option"]
cis_id	1.1.4
cis_benchmark	CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure nosuid option set on /tmp partition

Description

The nosuid mount option specifies that the filesystem cannot contain setuid files.

Rationale

Since the /tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /tmp.

Impact

None noted.

Audit Procedure

Command Line

# If a /tmp partition exists, verify that the nosuid option is set
# Run the following command and verify that nothing is returned:
findmnt -n /tmp | grep -v nosuid

Expected Result

No output should be returned.

Remediation

Command Line

# Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /tmp partition.
# See the fstab(5) manual page for more information.
# Run the following command to remount /tmp:
mount -o remount,nosuid /tmp

# OR Edit /etc/systemd/system/local-fs.target.wants/tmp.mount to add nosuid to the /tmp mount options:
# [Mount]
# Options=mode=1777,strictatime,noexec,nodev,nosuid

# Run the following command to remount /tmp:
mount -o remount,nosuid /tmp

Default Value

Not set by default.

References

• CIS Controls Version 7 - 5.1 Establish Secure Configurations: Maintain documented, standard security configuration standards for all authorized operating systems and software.

Profile

Level 1 - Server / Level 1 - Workstation, Assessment: Automated