Verify Groupownership of Files in /var/log/gdm3

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Description

To properly set the group owner of /var/log/gdm3/*, run the command:

$ sudo chgrp gdm /var/log/gdm3/*

or

$ sudo chgrp gdm3 /var/log/gdm3/*

or

$ sudo chgrp root /var/log/gdm3/*

Rationale

The /var/log/gdm3 directory contains information about the GDM daemon and should only be accessed by authorized personnel.

Remediation

Shell script

The following script can be run on the host to remediate the issue.

#!/bin/bash

if getent group "gdm" >/dev/null 2>&1; then
  newgroup="gdm"
elif getent group "gdm3" >/dev/null 2>&1; then
  newgroup="gdm3"
elif getent group "root" >/dev/null 2>&1; then
  newgroup="root"
fi
if [[ -z ${newgroup} ]]; then
  echo "gdm and gdm3 and root is not a defined group on the system"
  exit 1
fi

find  /var/log/gdm3/  -type f  ! -group gdm ! -group gdm3 ! -group root -regextype posix-extended -regex '.*' -exec chgrp -L $newgroup {} \;

Ansible playbook

The following playbook can be run with Ansible to remediate the issue.

- name: Check that the gdm group is defined
  getent:
    database: group
    key: gdm
  ignore_errors: true
  when: file_groupownerships_var_log_gdm3_newgroup is undefined
  tags:
  - configure_strategy
  - file_groupownerships_var_log_gdm3
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set the file_groupownerships_var_log_gdm3_newgroup variable if gdm found
  set_fact:
    file_groupownerships_var_log_gdm3_newgroup: gdm
  when: ansible_facts.getent_group["gdm"] is defined
  tags:
  - configure_strategy
  - file_groupownerships_var_log_gdm3
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Check that the gdm3 group is defined
  getent:
    database: group
    key: gdm3
  ignore_errors: true
  when: file_groupownerships_var_log_gdm3_newgroup is undefined
  tags:
  - configure_strategy
  - file_groupownerships_var_log_gdm3
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set the file_groupownerships_var_log_gdm3_newgroup variable if gdm3 found
  set_fact:
    file_groupownerships_var_log_gdm3_newgroup: gdm3
  when: ansible_facts.getent_group["gdm3"] is defined
  tags:
  - configure_strategy
  - file_groupownerships_var_log_gdm3
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Check that the root group is defined
  getent:
    database: group
    key: root
  ignore_errors: true
  when: file_groupownerships_var_log_gdm3_newgroup is undefined
  tags:
  - configure_strategy
  - file_groupownerships_var_log_gdm3
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set the file_groupownerships_var_log_gdm3_newgroup variable if root found
  set_fact:
    file_groupownerships_var_log_gdm3_newgroup: root
  when: ansible_facts.getent_group["root"] is defined
  tags:
  - configure_strategy
  - file_groupownerships_var_log_gdm3
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Find /var/log/gdm3/ file(s) matching .* recursively
  command: find  /var/log/gdm3/  -type f  ! -group gdm ! -group gdm3 ! -group root
    -regextype posix-extended -regex ".*"
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  tags:
  - configure_strategy
  - file_groupownerships_var_log_gdm3
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure group owner on /var/log/gdm3/ file(s) matching .*
  file:
    path: '{{ item }}'
    group: '{{ file_groupownerships_var_log_gdm3_newgroup }}'
    state: file
  with_items:
  - '{{ files_found.stdout_lines }}'
  tags:
  - configure_strategy
  - file_groupownerships_var_log_gdm3
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed