Chrony Configure Pool and Server

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Description

Chrony is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information on chrony can be found at https://chrony-project.org/. Chrony can be configured to be a client and/or a server. Add or edit server or pool lines to /etc/chrony/chrony.conf as appropriate:

server <remote-server>

Multiple servers may be configured.

Rationale

If chrony is in use on the system proper configuration is vital to ensuring time synchronization is working properly.

Remediation

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='${db:Status-Status}' 'linux-base' 2>/dev/null | grep -q '^installed$' && { dpkg-query --show --showformat='${db:Status-Status}' 'chrony' 2>/dev/null | grep -q '^installed$'; }; then

var_multiple_time_servers='0.ubuntu.pool.ntp.org,1.ubuntu.pool.ntp.org,2.ubuntu.pool.ntp.org,3.ubuntu.pool.ntp.org'

var_multiple_time_pools='0.ubuntu.pool.ntp.org,1.ubuntu.pool.ntp.org,2.ubuntu.pool.ntp.org,3.ubuntu.pool.ntp.org'


config_file="/etc/chrony/chrony.conf"

# Check and configigure servers in /etc/chrony/chrony.conf
IFS="," read -a SERVERS <<< $var_multiple_time_servers
for srv in "${SERVERS[@]}"
do
   NTP_SRV=$(grep -w $srv $config_file)
   if [[ ! "$NTP_SRV" == "server "* ]]
   then
     time_server="server $srv"
     echo $time_server >> "$config_file"
   fi
done

# Check and configure pools in /etc/chrony/chrony.conf
IFS="," read -a POOLS <<< $var_multiple_time_pools
for srv in "${POOLS[@]}"
do
   NTP_POOL=$(grep -w $srv $config_file)
   if [[ ! "$NTP_POOL" == "pool "* ]]
   then
     time_server="pool $srv"
     echo $time_server >> "$config_file"
   fi
done

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:
  - NIST-800-53-AU-8(1)(a)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-10.4.3
  - chronyd_configure_pool_and_server
  - configure_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
- name: XCCDF Value var_multiple_time_servers # promote to variable
  set_fact:
    var_multiple_time_servers: !!str 0.ubuntu.pool.ntp.org,1.ubuntu.pool.ntp.org,2.ubuntu.pool.ntp.org,3.ubuntu.pool.ntp.org
  tags:
    - always
- name: XCCDF Value var_multiple_time_pools # promote to variable
  set_fact:
    var_multiple_time_pools: !!str 0.ubuntu.pool.ntp.org,1.ubuntu.pool.ntp.org,2.ubuntu.pool.ntp.org,3.ubuntu.pool.ntp.org
  tags:
    - always

- name: Chrony Configure Pool and Server - Add missing / update wrong records for
    remote time servers
  ansible.builtin.lineinfile:
    path: /etc/chrony/chrony.conf
    regexp: ^\s*\bserver\b\s*\b{{ item }}\b$
    state: present
    line: server {{ item }}
    create: true
  with_items:
  - '{{ var_multiple_time_servers.split(",") }}'
  when:
  - '"linux-base" in ansible_facts.packages'
  - '"chrony" in ansible_facts.packages'
  tags:
  - NIST-800-53-AU-8(1)(a)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-10.4.3
  - chronyd_configure_pool_and_server
  - configure_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed

- name: Chrony Configure Pool and Server - Add missing / update wrong records for
    remote time pools
  ansible.builtin.lineinfile:
    path: /etc/chrony/chrony.conf
    regexp: ^\s*\bpool\b\s*\b{{ item }}\b$
    state: present
    line: pool {{ item }}
    create: true
  with_items:
  - '{{ var_multiple_time_pools.split(",") }}'
  when:
  - '"linux-base" in ansible_facts.packages'
  - '"chrony" in ansible_facts.packages'
  tags:
  - NIST-800-53-AU-8(1)(a)
  - NIST-800-53-CM-6(a)
  - PCI-DSS-Req-10.4.3
  - chronyd_configure_pool_and_server
  - configure_strategy
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed