← Back to Canonical Ubuntu 20.04 LTS Security Technical Implementation Guide

V-238218

CAT I (High)

The Ubuntu operating system must not allow unattended or automatic login via SSH.

Rule ID

SV-238218r991591_rule

STIG

Canonical Ubuntu 20.04 LTS Security Technical Implementation Guide

Version

V2R4

CCIs

CCI-000366

Discussion

Failure to restrict system access to authenticated users negatively impacts Ubuntu operating system security.

Check Content

Verify that unattended or automatic login via SSH is disabled with the following command:

$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iEH '^\s*(permit(.*?)(passwords|environment))'

PermitEmptyPasswords no
PermitUserEnvironment no

If "PermitEmptyPasswords" or "PermitUserEnvironment" keywords are not set to "no", are missing completely, or are commented out, this is a finding.

If conflicting results are returned, this is a finding.

Fix Text

Configure the Ubuntu operating system to allow the SSH daemon to not allow unattended or automatic login to the system. 
 
Add or edit the following lines in the "/etc/ssh/sshd_config" file: 
 
PermitEmptyPasswords no 
PermitUserEnvironment no 
 
Restart the SSH daemon for the changes to take effect: 
 
$ sudo systemctl restart sshd.service