#!/bin/bash
############################################################################
#                                                                          #
# This file is part of Plinth.                                             #
#                                                                          #
# This program is free software: you can redistribute it and/or modify     #
# it under the terms of the GNU Affero General Public License as           #
# published by the Free Software Foundation, either version 3 of the       #
# License, or (at your option) any later version.                          #
#                                                                          #
# This program is distributed in the hope that it will be useful,          #
# but WITHOUT ANY WARRANTY; without even the implied warranty of           #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            #
# GNU Affero General Public License for more details.                      #
#                                                                          #
# You should have received a copy of the GNU Affero General Public License #
# along with this program.  If not, see <http://www.gnu.org/licenses/>.    #
#                                                                          #
#                                                                          #
# This script is a wrapper around ez-ipupdate and/or wget                  #
# to update a Dynamic DNS account. The script is used as an                #
# interface between plinth and ez-ipupdate                                 #
# the script will store configuration, return configuration                #
# to plinth UI and do a dynamic DNS update. The script will                #
# also determe if we are behind a NAT device, if we can use                #
# ez-ipupdate tool or if we need to do some wget magic                     #
#                                                                          #
# Todo: IPv6                                                               #
# Todo: GET WAN IP from Router via UPnP if supported                       #
# Todo: licence string?                                                    #
# author: Daniel Steglich <steglich@datasystems24.de>                      #
#                                                                          #
############################################################################

PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# static values
WGET=$(which wget)
WGETOPTIONS="-4 -o /dev/null -t 3 -T 3"
EMPTYSTRING="none"
NOIP="0.0.0.0"
# how often do we poll for IP changes if we are behind a NAT?
UPDATEMINUTES=5
# if we do not have a IP check URL, how often should we do a "blind" update
UPDATEMINUTESUNKNOWN=3600
TOOLNAME=ez-ipupdate
UPDATE_TOOL=$(which ${TOOLNAME})
DISABLED_STRING='disabled'
ENABLED_STRING='enabled'

# Dirs and filenames
CFGDIR="/etc/${TOOLNAME}/"
CFG="${CFGDIR}${TOOLNAME}.conf"
CFG_disabled="${CFGDIR}${TOOLNAME}.inactive"
IPFILE="${CFGDIR}${TOOLNAME}.currentIP"
STATUSFILE="${CFGDIR}${TOOLNAME}.status"
LASTUPDATE="${CFGDIR}/last-update"
HELPERCFG="${CFGDIR}${TOOLNAME}-plinth.cfg"
CRONJOB="/etc/cron.d/${TOOLNAME}"
PIDFILE="/var/run/ez-ipupdate.pid"

# this function will parse commandline options
doGetOpt()
{
    basicauth=0
    ignoreCertError=0

    while getopts ":s:d:u:p:I:U:c:b:" opt; do
        case ${opt} in
            s)
                if [ "${OPTARG}" != "${EMPTYSTRING}" ];then
                    server=${OPTARG}
                else
                    server=""
                fi
            ;;
            d)
                host=${OPTARG}
            ;;
            u)
                user=${OPTARG}
            ;;
            p)
                pass=${OPTARG}
            ;;
            I)
                if [ "${OPTARG}" != "${EMPTYSTRING}" ];then
                    ipurl=${OPTARG}
                else
                    ipurl=""
                fi
            ;;
            U)
                if [ "${OPTARG}" != "${EMPTYSTRING}" ];then
                    updateurl=${OPTARG}
                else
                    updateurl=""
                fi
            ;;
            b)
                basicauth=${OPTARG}
            ;;
            c)
                ignoreCertError=${OPTARG}
            ;;            
            \?)
                echo "Invalid option: -${OPTARG}" >&2
                exit 1
            ;;
        esac
    done
}

# this function will write a persistent config file to disk
doWriteCFG()
{
    mkdir ${CFGDIR} 2> /dev/null
    # always write to the inactive config - needs to be enabled via "start" command later
    local out_file=${CFG_disabled}

    # reset the last update time
    echo 0 > ${LASTUPDATE}

    # reset the last updated IP
    echo "0.0.0.0" > ${IPFILE}

    # reset last update (if there is one)
    rm ${STATUSFILE} 2> /dev/null

    # find the interface (always the default gateway interface)
    default_interface=$(ip route |grep default |awk '{print $5}')

    # store the given options in ez-ipupdate compatible config file
    {
        echo "host=${host}"
        echo "server=${server}"
        echo "user=${user}:${pass}"
        echo "service-type=gnudip"
        echo "retrys=3"
        echo "wildcard"
    } > ${out_file}
    
    # store UPDATE URL params
    {
        echo "POSTURL ${updateurl}"
        echo "POSTAUTH ${basicauth}"
        echo "POSTSSLIGNORE ${ignoreCertError}"
    } > ${HELPERCFG}
    
    # check if we are behind a NAT Router
    echo "IPURL ${ipurl}" >> ${HELPERCFG}
    if [ -z ${ipurl} ];then
        echo "NAT unknown" >> ${HELPERCFG}
    else 
        doGetWANIP
        ISGLOBAL=$(ip addr ls "${default_interface}" | grep "${wanip}")
        if [ -z "${ISGLOBAL}" ];then
            # we are behind NAT
            echo "NAT yes" >> ${HELPERCFG}
        else
            # we are directly connected
            echo "NAT no" >> ${HELPERCFG}
            # if this file is added ez-ipupdate will take ip form this interface
            {
                "interface=${default_interface}"
                # if this line is added to config file, ez-ipupdate will be launched on startup via init.d
                "daemon"
                "execute=${0} success"
            } > ${out_file}
        fi
    fi
}

# this function will read the config file from disk
# special treatment for empty strings is done here:
# plinth will give empty strings like: ''
# but we don't want this single quotes to be used
doReadCFG()
{ 
    host=""
    server=""
    user=""
    pass=""
    ipurl=""

    if [ ! -z "${cfgfile}" ];then
        host=$(grep host "${cfgfile}" 2> /dev/null |cut -d = -f 2)
        server=$(grep server "${cfgfile}" 2> /dev/null |cut -d = -f 2 |grep -v ^\'\')
        user=$(grep user "${cfgfile}" 2> /dev/null |cut -d = -f 2 |cut -d : -f 1 )
        pass=$(grep user "${cfgfile}" 2> /dev/null |cut -d = -f 2 |cut -d : -f 2)
    fi

    if [ ! -z ${HELPERCFG} ];then
        ipurl=$(grep ^IPURL "${HELPERCFG}" 2> /dev/null |awk '{print $2}' |grep -v ^\'\')
        updateurl=$(grep POSTURL "${HELPERCFG}" 2> /dev/null |awk '{print $2}' |grep -v ^\'\')
        basicauth=$(grep POSTAUTH "${HELPERCFG}" 2> /dev/null |awk '{print $2}' |grep -v ^\'\')
        ignoreCertError=$(grep POSTSSLIGNORE "${HELPERCFG}" 2> /dev/null |awk '{print $2}' |grep -v ^\'\')
    fi  
}

# replace vars from url: i.e.:
# https://example.com/update.php?domain=<Domain>&User=<User>&Pass=<Pass>
# also this function will remove the surounding single quotes from the URL string
# as plinth will add them
doReplaceVars()
{
    local url=$(echo "${updateurl}" | sed "s/<Ip>/${wanip}/g")
    url=$(echo "${url}" | sed "s/<Domain>/${host}/g")
    url=$(echo "${url}" | sed "s/<User>/${user}/g")
    url=$(echo "${url}" | sed "s/<Pass>/${pass}/g")
    url=$(echo "${url}" | sed "s/'//g")
    updateurl=${url}
    logger "expanded update URL as ${url}"
}

# doReadCFG() needs to be run before this
# this function will return all configured parameters in a way that
# plinth will understand (plinth know the order of
# parameters this function will return)
doStatus()
{
    PROC=$(pgrep ${TOOLNAME})
    if [ -f "${CRONJOB}" ];then
        echo "${ENABLED_STRING}"
    elif [ ! -z "${PROC}" ];then
        echo "${ENABLED_STRING}"
    else
        echo "${DISABLED_STRING}"
    fi
    if [ ! -z "${server}" ];then
        echo "${server}"
    else
        echo "${DISABLED_STRING}"
    fi
    if [ ! -z "${host}"  ];then
        echo "${host}"
    else
        echo "${DISABLED_STRING}"
    fi
    if [ ! -z "${user}" ];then
        echo "${user}"
    else
        echo "${DISABLED_STRING}"
    fi
    if [ ! -z "${pass}"  ];then
        echo "${pass}"
    else
        echo "${DISABLED_STRING}"
    fi
    if [ ! -z "${ipurl}" ];then
        echo "${ipurl}"
    else
        echo "${DISABLED_STRING}"
    fi
    if [ ! -z "${updateurl}"  ];then
        echo "${updateurl}"
    else
        echo "${DISABLED_STRING}"
    fi
    if [ ! -z "${basicauth}" ];then
        echo "${basicauth}"
    else
        echo "${DISABLED_STRING}"
    fi
    if [ ! -z "${ignoreCertError}" ];then
        echo "${ignoreCertError}"
    else
        echo "${DISABLED_STRING}"
    fi
}

# ask a public WEB Server for the WAN IP we are comming from
# and store this ip within $wanip
doGetWANIP()
{
    if [ ! -z "${ipurl}" ];then
        outfile=$(mktemp)
        local cmd="${WGET} ${WGETOPTIONS} -O ${outfile} ${ipurl}"
        $cmd
        wanip=$(sed s/[^0-9.]//g "${outfile}")
        rm "${outfile}"
        [ -z "${wanip}" ] && wanip=${NOIP}
    else
        # no WAN IP found because of missing check URL
        wanip=${NOIP}
    fi
}

# actualy do the update (using wget or ez-ipupdate or even both)
# this function is called via cronjob
doUpdate()
{
    local dnsentry=$(nslookup "${host}"|tail -n2|grep A|sed s/[^0-9.]//g)
    if [ "${dnsentry}" =  "${wanip}" ];then
        return
    fi
    if [ ! -z "${server}" ];then
        start-stop-daemon -S -x "${UPDATE_TOOL}" -m -p "${PIDFILE}" -- -c "${cfgfile}"
    fi
    if [ ! -z "${updateurl}" ];then
        doReplaceVars
        if [ "${basicauth}" = "enabled" ];then
            WGETOPTIONS="${WGETOPTIONS} --user ${user} --password ${pass} "
        fi
        if [ "${ignoreCertError}" = "enabled" ];then
            WGETOPTIONS="${WGETOPTIONS} --no-check-certificate "
        fi
        local cmd="${WGET} ${WGETOPTIONS} ${updateurl}"
        $cmd
        # ToDo: check the returning text from WEB Server. User need to give expected string.
        if [ ${?} -eq 0 ];then
            ${0} success ${wanip}
        else
            ${0} failed
        fi
    fi
}

cmd=${1}
shift
# decide which config to use
cfgfile="/tmp/none"
[ -f ${CFG_disabled} ] && cfgfile=${CFG_disabled}
[ -f ${CFG} ] && cfgfile=${CFG}

# check what action is requested
case ${cmd} in
    configure)
        doGetOpt "${@}"
        doWriteCFG
    ;;
    start)
        doGetWANIP
        if [ "$(grep ^NAT ${HELPERCFG} | awk '{print $2}')" = "no" ];then
            #if we are not behind a NAT device and we use gnudip, start the daemon tool
            local gnudipServer=$(grep server ${cfgfile} 2> /dev/null |cut -d = -f 2 |grep -v ^\'\')
            if [ -f ${CFG} -a ! -z "${gnudipServer}" ];then
                mv ${CFG_disabled} ${CFG}
                /etc/init.d/${TOOLNAME} start
            fi
            # if we are not behind a NAT device and we use update-URL, add a cronjob
            # (daemon tool does not support update-URL feature)
            if [ ! -z "$(grep ^POSTURL $HELPERCFG | awk '{print $2}')" ];then
                echo "*/${UPDATEMINUTES} * * * * root ${0} update" > ${CRONJOB}
                $0 update
            fi
        else
            # if we are behind a NAT device, add a cronjob (daemon tool cannot monitor WAN IP changes)
            echo "*/${UPDATEMINUTES} * * * * root ${0} update" > $CRONJOB
            $0 update
        fi
    ;;
    get-nat)
        NAT=$(grep ^NAT $HELPERCFG 2> /dev/null | awk '{print $2}')
        [ -z "${NAT}" ] && NAT="unknown"
        echo ${NAT}
    ;;
    update)
        doReadCFG
        dnsentry=$(nslookup "${host}"|tail -n2|grep A|sed s/[^0-9.]//g)
        doGetWANIP
        echo ${wanip} > ${IPFILE}
        grep -v execute ${cfgfile} > ${cfgfile}.tmp
        mv ${cfgfile}.tmp ${cfgfile}
        echo "execute=${0} success ${wanip}" >> ${cfgfile}
        # if we know our WAN IP, only update if IP changes
        if [ "${dnsentry}" != "${wanip}" -a "${wanip}" != ${NOIP} ];then
            doUpdate
        fi
        # if we don't know our WAN IP do a blind update once a hour
        if [ "${wanip}" = ${NOIP} ];then
            uptime=$(cut -d . -f 1 /proc/uptime)
            LAST=0
            [ -f ${LASTUPDATE} ] && LAST=$(cat ${LASTUPDATE})
            diff=$((uptime - LAST))
            if [ ${diff} -gt ${UPDATEMINUTESUNKNOWN} ];then
                doUpdate
            fi
        fi
    ;;
    stop)
        rm ${CRONJOB} 2> /dev/null
        /etc/init.d/${TOOLNAME} stop
        kill "$(cat ${PIDFILE})" 2> /dev/null
        mv ${CFG} ${CFG_disabled}
    ;;
    success)
        date=$(date)
        echo "last update done (${date})" > ${STATUSFILE}
        awk '{print $1}' /proc/uptime |cut -d . -f 1 > ${LASTUPDATE}
        # if called from cronjob, the current IP is given as parameter
        if [ $# -eq 1 ];then
            echo "${1}" > ${IPFILE}
        else
            # if called from ez-ipupdate daemon, no WAN IP is given as parameter
            doGetWANIP
            echo ${wanip} > ${IPFILE}
        fi
    ;;
    failed)
        date=$(date)
        echo "last update failed (${date})" > ${STATUSFILE}
    ;;    
    get-last-success)
        if [ -f ${STATUSFILE} ];then
            cat ${STATUSFILE}
        else
            echo "no successful update recorded since last config change"
        fi
    ;;
    status)
        doReadCFG
        doStatus
    ;;
    get-timer)
        echo ${UPDATEMINUTES}
    ;;
    clean)
        rm ${CFGDIR}/*
        rm ${CRONJOB}
    ;;
    *)
        echo "usage: status|configure <options>|start|stop|update|get-nat|clean|success [updated IP]|failed|get-last-success"
        echo ""
        echo "options are:"
        echo "-s <server>             Gnudip Server address"
        echo "-d <domain>             Domain to be updated"
        echo "-u <user>               Account username"
        echo "-p <password>           Account Password"
        echo "-I <IP check URL>       A URL which returns the IP of the client who is requesting"
        echo "-U <update URL>         The update URL (a HTTP GET on this URL will be done)"
        echo "-c <1|0>                disable SSL check on Update URL"
        echo "-b <1|0>                use HTTP basic auth on Update URL"
        echo ""
        echo "update                  do a one time update"
        echo "clean                   delete configuration"
        echo "success                 store update success and optional the updated IP"
        echo "failed                  store update failure"
        echo "get-nat                 return the detected nat type"
        echo "get-last-success        return date of last successful update"
    ;;
esac
exit 0
