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V-260472

CAT III (Low)

Ubuntu 22.04 LTS must restrict access to the kernel message buffer.

Rule ID

SV-260472r1137695_rule

STIG

Canonical Ubuntu 22.04 LTS Security Technical Implementation Guide

Version

V2R8

CCIs

CCI-001090

Discussion

Restricting access to the kernel message buffer limits access only to root. This prevents attackers from gaining additional system information as a nonprivileged user.

Check Content

Verify Ubuntu 22.04 LTS is configured to restrict access to the kernel message buffer by using the following command: 
 
     $ sysctl kernel.dmesg_restrict 
     kernel.dmesg_restrict = 1 
 
If "kernel.dmesg_restrict" is not set to "1" or is missing, this is a finding. 
 
Verify that there are no configurations that enable the kernel dmesg function: 
 
     $ sudo grep -ir kernel.dmesg_restrict /run/sysctl.d/* /etc/sysctl.d/* /usr/local/lib/sysctl.d/* /usr/lib/sysctl.d/* /lib/sysctl.d/* /etc/sysctl.conf 2> /dev/null 
     /etc/sysctl.d/10-kernel-hardening.conf:kernel.dmesg_restrict = 1 
 
If "kernel.dmesg_restrict" is not set to "1", is commented out, is missing, or conflicting results are returned, this is a finding.

Fix Text

Configure Ubuntu 22.04 LTS to restrict access to the kernel message buffer. 
 
Add or modify the following line in the "/etc/sysctl.conf" file: 
 
kernel.dmesg_restrict = 1 
 
Remove any configurations that conflict with the above from the following locations:  
 
/run/sysctl.d/ 
/etc/sysctl.d/ 
/usr/local/lib/sysctl.d/ 
/usr/lib/sysctl.d/ 
/lib/sysctl.d/ 
/etc/sysctl.conf 
 
Reload settings from all system configuration files by using the following command: 
 
     $ sudo sysctl --system