Enforce usage of pam_wheel for su authentication
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Description
To ensure that only users who are members of the wheel group can
run commands with altered privileges through the su command, make
sure that the following line exists in the file /etc/pam.d/su:
auth required pam_wheel.so use_uid
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 rpm --quiet -q pam; then
# uncomment the option if commented
sed '/^[[:space:]]*#[[:space:]]*auth[[:space:]]\+required[[:space:]]\+pam_wheel\.so[[:space:]]\+use_uid$/s/^[[:space:]]*#//' -i /etc/pam.d/su
else
>&2 echo 'Remediation is not applicable, nothing was done'
fi
Ansible playbook
The following playbook can be run with Ansible to remediate the issue.
- name: Gather the package facts
package_facts:
manager: auto
tags:
- CCE-85855-5
- low_complexity
- low_disruption
- medium_severity
- no_reboot_needed
- restrict_strategy
- use_pam_wheel_for_su
- name: Restrict usage of su command only to members of wheel group
replace:
path: /etc/pam.d/su
regexp: ^[\s]*#[\s]*auth[\s]+required[\s]+pam_wheel\.so[\s]+use_uid$
replace: auth required pam_wheel.so use_uid
when: '"pam" in ansible_facts.packages'
tags:
- CCE-85855-5
- low_complexity
- low_disruption
- medium_severity
- no_reboot_needed
- restrict_strategy
- use_pam_wheel_for_su
Warning
Members of “wheel” or GID 0 groups are checked by default if the group option is not set
for pam_wheel.so module. Therefore, members of these groups should be manually checked or
a different group should be informed according to the site policy.
