Ensure the Group Used by pam_wheel.so Module Exists on System and is Empty
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Description
Ensure that the group sugroup
referenced by
var_pam_wheel_group_for_su
variable and used as value for the pam_wheel.so
group
option exists and has no members. This empty group used by
pam_wheel.so
in /etc/pam.d/su
ensures that no user can run commands with
altered privileges through the su
command.
Rationale
The su
program allows to run commands with a substitute user and group ID.
It is commonly used to run commands as the root user.
Limiting access to such command is considered a good security practice.
Shell script
The following script can be run on the host to remediate the issue.
#!/bin/bash
# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q installed; then
var_pam_wheel_group_for_su='sugroup'
if ! grep -q "^${var_pam_wheel_group_for_su}:[^:]*:[^:]*:[^:]*" /etc/group; then
groupadd ${var_pam_wheel_group_for_su}
fi
# group must be empty
gpasswd -M '' ${var_pam_wheel_group_for_su}
else
>&2 echo 'Remediation is not applicable, nothing was done'
fi
Ansible playbook
The following playbook can be run with Ansible to remediate the issue.
- name: Gather the package facts
package_facts:
manager: auto
tags:
- PCI-DSSv4-2.2
- PCI-DSSv4-2.2.6
- ensure_pam_wheel_group_empty
- low_complexity
- low_disruption
- medium_severity
- no_reboot_needed
- restrict_strategy
- name: XCCDF Value var_pam_wheel_group_for_su # promote to variable
set_fact:
var_pam_wheel_group_for_su: !!str sugroup
tags:
- always
- name: Ensure the Group Used by pam_wheel.so Module Exists on System and is Empty
- Ensure {{ var_pam_wheel_group_for_su }} Group Exists
ansible.builtin.group:
name: '{{ var_pam_wheel_group_for_su }}'
state: present
when: '"libpam-runtime" in ansible_facts.packages'
tags:
- PCI-DSSv4-2.2
- PCI-DSSv4-2.2.6
- ensure_pam_wheel_group_empty
- low_complexity
- low_disruption
- medium_severity
- no_reboot_needed
- restrict_strategy
- name: Ensure the Group Used by pam_wheel.so Module Exists on System and is Empty
- Ensure {{ var_pam_wheel_group_for_su }} Group is Empty
ansible.builtin.lineinfile:
path: /etc/group
regexp: ^({{ var_pam_wheel_group_for_su }}:[^:]+:[0-9]+:).*$
line: \1
backrefs: true
when: '"libpam-runtime" in ansible_facts.packages'
tags:
- PCI-DSSv4-2.2
- PCI-DSSv4-2.2.6
- ensure_pam_wheel_group_empty
- low_complexity
- low_disruption
- medium_severity
- no_reboot_needed
- restrict_strategy
Warning
Note that this rule just ensures the group exists and has no members. This rule does not
configure pam_wheel.so
module. The pam_wheel.so
module configuration is
accomplished by use_pam_wheel_group_for_su
rule.