File systems that contain user home directories must be mounted to prevent files with the setuid and setguid bit set from being executed.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-75575	UBTU-16-010800	SV-90255r2_rule		Medium

Description
The "nosuid" mount option causes the system to not execute setuid and setgid files with owner privileges. This option must be used for mounting any file system not containing approved setuid and setguid files. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

STIG	Date
Canonical Ubuntu 16.04 LTS Security Technical Implementation Guide	2018-07-18

Details

Check Text ( C-75279r1_chk )
Verify file systems that contain user home directories are mounted with the "nosuid" option. Note: If a separate file system has not been created for the user home directories (user home directories are mounted under "/"), this is not a finding as the "nosuid" option cannot be used on the "/" system. Find the file system(s) that contain the user home directories with the following command: # awk -F: '($3>=1000)&&($1!="nobody"){print $1,$3,$6}' /etc/passwd smithj:1001: /home/smithj robinst:1002: /home/robinst Check the file systems that are mounted at boot time with the following command: # more /etc/fstab UUID=a411dc99-f2a1-4c87-9e05-184977be8539 /home ext4 rw,relatime,discard,data=ordered,nosuid 0 2 If a file system found in "/etc/fstab" refers to the user home directory file system and it does not have the "nosuid" option set, this is a finding.

Check Text ( C-75279r1_chk )

Verify file systems that contain user home directories are mounted with the "nosuid" option.

Note: If a separate file system has not been created for the user home directories (user home directories are mounted under "/"), this is not a finding as the "nosuid" option cannot be used on the "/" system.

Find the file system(s) that contain the user home directories with the following command:

# awk -F: '($3>=1000)&&($1!="nobody"){print $1,$3,$6}' /etc/passwd

smithj:1001: /home/smithj
robinst:1002: /home/robinst

Check the file systems that are mounted at boot time with the following command:

# more /etc/fstab

UUID=a411dc99-f2a1-4c87-9e05-184977be8539 /home ext4 rw,relatime,discard,data=ordered,nosuid 0 2

If a file system found in "/etc/fstab" refers to the user home directory file system and it does not have the "nosuid" option set, this is a finding.

Fix Text (F-82203r1_fix)
Configure the "/etc/fstab" to use the "nosuid" option on file systems that contain user home directories for interactive users.