Verify User Who Owns /var/log/lastlog File

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Description

To properly set the owner of /var/log/lastlog, run the command:

$ sudo chown root /var/log/lastlog

Rationale

The /var/log/lastlog file contains logs of reports the most recent login of all users 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

newown=""
if id "0" >/dev/null 2>&1; then
  newown="0"
fi

if [[ -z "$newown" ]]; then
  >&2 echo "0 is not a defined user on the system"
else

find -P /var/log/ -maxdepth 1 -type f  ! -user 0 -regextype posix-extended -regex '.*lastlog(\.[^\/]+)?$' -exec chown --no-dereference "$newown" {} \;

fi

Ansible playbook

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

- name: Set the file_owner_var_log_lastlog_newown variable if represented by uid
  ansible.builtin.set_fact:
    file_owner_var_log_lastlog_newown: '0'
  tags:
  - configure_strategy
  - file_owner_var_log_lastlog
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Find /var/log/ file(s) matching .*lastlog(\.[^\/]+)?$
  ansible.builtin.command: find -P /var/log/ -maxdepth 1 -type f  ! -user 0 -regextype
    posix-extended -regex ".*lastlog(\.[^\/]+)?$"
  register: files_found
  changed_when: false
  failed_when: false
  check_mode: false
  tags:
  - configure_strategy
  - file_owner_var_log_lastlog
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner on /var/log/ file(s) matching .*lastlog(\.[^\/]+)?$
  ansible.builtin.file:
    path: '{{ item }}'
    follow: false
    owner: '{{ file_owner_var_log_lastlog_newown }}'
    state: file
  with_items:
  - '{{ files_found.stdout_lines }}'
  tags:
  - configure_strategy
  - file_owner_var_log_lastlog
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed