#!/bin/bash

config=/etc/chrony.conf
keyfile=/etc/chrony.keys
chronyc=/usr/bin/chronyc
dhclient_servers=/var/lib/dhclient/chrony.servers.*
service_name=chronyd.service

get_key() {
    awk '/^[ \t]*'$1'\>/ { print $2; exit }' < $keyfile
}

get_commandkeyid() {
    awk '/^[ \t]*commandkey\>/ { keyid=$2 } END { print keyid }' < $config
}

chrony_command() {
    commandkeyid=$(get_commandkeyid)
    [ -z "$commandkeyid" ] && return 1
    commandkey=$(get_key $commandkeyid)
    [ -z "$commandkey" ] && return 2

    $chronyc <<EOF
password $commandkey
$1
EOF
}

generate_commandkey() {
    commandkeyid=$(get_commandkeyid)
    [ -z "$commandkeyid" ] && return 1
    commandkey=$(get_key $commandkeyid)
    [ -z "$commandkey" ] || return 0

    commandkey=$(tr -c -d '[\041-\176]' < /dev/urandom | head -c 16)
    [ -n "$commandkey" ] && echo "$commandkeyid $commandkey" >> $keyfile
}

add_dhclient_servers() {
    command=$(cat $dhclient_servers 2> /dev/null |
        while read server serverargs; do
            echo "add server $server $serverargs"
        done)
    if [ -n "$command" ]; then
        chrony_command "$command" &> /dev/null
    fi
}

is_running() {
    systemctl status $service_name &> /dev/null
}

case "$1" in
    generate-commandkey)
        generate_commandkey
        ;;
    add-dhclient-servers)
        add_dhclient_servers
        ;;
    command)
        is_running && chrony_command "$2"
        ;;
    forced-command)
        chrony_command "$2"
        ;;
    *)
        echo $"Usage: $0 {generate-commandkey|add-dhclient-servers|command|forced-command}"
        exit 2
esac
exit $?