Ensure There Are No Accounts With Blank or Null Passwords
Description
Check the “/etc/shadow” file for blank passwords with the
following command:
$ sudo awk -F: '!$2 {print $1}' /etc/shadow
If the command returns any results, this is a finding.
Configure all accounts on the system to have a password or lock
the account with the following commands:
Perform a password reset:
Lock an account:
$ sudo passwd -l [username]
Rationale
If an account has an empty password, anyone could log in and
run commands with the privileges of that account. Accounts with
empty passwords should never be used in operational environments.
Shell script
The following script can be run on the host to remediate the issue.
# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then
readarray -t users\_with\_empty\_pass < <(sudo awk -F: '!$2 {print $1}' /etc/shadow)
for user\_with\_empty\_pass in "${users\_with\_empty\_pass[@]}"
do
passwd -l $user\_with\_empty\_pass
done
else
>&2 echo 'Remediation is not applicable, nothing was done'
fi
Ansible playbook
The following playbook can be run with Ansible to remediate the issue.
- name: Collect users with no password
command: |
awk -F: '!$2 {print $1}' /etc/shadow
register: users\_nopasswd
when: ansible\_virtualization\_type not in ["docker", "lxc", "openvz", "podman", "container"]
tags:
- NIST-800-53-CM-6(b)
- NIST-800-53-CM-6.1(iv)
- high\_severity
- low\_complexity
- low\_disruption
- no\_empty\_passwords\_etc\_shadow
- no\_reboot\_needed
- restrict\_strategy
- name: Lock users with no password
command: |
passwd -l {{ item }}
with\_items: '{{ users\_nopasswd.stdout\_lines }}'
when:
- ansible\_virtualization\_type not in ["docker", "lxc", "openvz", "podman", "container"]
- users\_nopasswd.stdout\_lines | length > 0
tags:
- NIST-800-53-CM-6(b)
- NIST-800-53-CM-6.1(iv)
- high\_severity
- low\_complexity
- low\_disruption
- no\_empty\_passwords\_etc\_shadow
- no\_reboot\_needed
- restrict\_strategy
Warning
Note that this rule is not applicable for systems running within a container. Having user with empty password within a container is not considered a risk, because it should not be possible to directly login into a container anyway.
