Verify User Who Owns /var/log/auth.log File

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Description

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

$ sudo chown syslog /var/log/auth.log

or

$ sudo chown root /var/log/auth.log

Rationale

The /var/log/auth.log file contains records information about user login attempts and authentication processes 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 id "syslog" >/dev/null 2>&1; then
  newown="syslog"
elif id "root" >/dev/null 2>&1; then
  newown="root"
fi
if [[ -z ${newown} ]]; then
  echo "syslog and root is not a defined user on the system"
  exit 1
fi
chown $newown /var/log/auth.log

Ansible playbook

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

- name: Check that the syslog user is defined
  getent:
    database: passwd
    key: syslog
  ignore_errors: true
  tags:
  - configure_strategy
  - file_owner_var_log_auth
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Set the file_owner_var_log_auth_newown variable if syslog found
  set_fact:
    file_owner_var_log_auth_newown: syslog
  when: ansible_facts.getent_passwd["syslog"] is defined
  tags:
  - configure_strategy
  - file_owner_var_log_auth
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Check that the root user is defined
  getent:
    database: passwd
    key: root
  ignore_errors: true
  when: file_owner_var_log_auth_newown is undefined
  tags:
  - configure_strategy
  - file_owner_var_log_auth
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

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

- name: Test for existence /var/log/auth.log
  stat:
    path: /var/log/auth.log
  register: file_exists
  tags:
  - configure_strategy
  - file_owner_var_log_auth
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Ensure owner on /var/log/auth.log
  file:
    path: /var/log/auth.log
    owner: '{{ file_owner_var_log_auth_newown }}'
  when: file_exists.stat is defined and file_exists.stat.exists
  tags:
  - configure_strategy
  - file_owner_var_log_auth
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed