GratisDNS.sh

#!/bin/sh
# gratisdns.sh - A GratisDNS.dk DDNSd module for Synology DSM
#
# Author:
#       Brian Schmidt Pedersen (http://briped.net)
#
# Version:
#       1.0.0
#
# Description:
#       This is a custom DDNSd module, for use with my Synology DiskStation. It
#       allows me to use the DSM interface for GratisDNS.dk DDNS service.
#
#       To use this script, put it in the "/sbin" folder of the DiskStation,
#       i.e. "/sbin/gratisdns.sh"
#
#       Then edit the "/etc.defaults/ddnsd_provider.conf" file and add the
#       following section at the end of that file:
#
#       [GratisDNS.dk]
#               modulepath=/sbin/gratisdns.sh
#               queryurl=https://ssl.gratisdns.dk/ddns.phtml?u=__USERNAME__&p=__PASSWORD__&d=__DOMAIN__&h=__HOSTNAME__&i=__MYIP__
#
#
# Changelist:
#       1.0.0
#           + Release
#
# Todo:
#       Add support for multiple DDNS hosts, either through a conf file, or
#       through a delimited string from DSM. Only with same admin user though.
#       F.ex.: sub1.example.com|sub2.example.com
#
#       Specify the target interface. This would probably be a hack that won't
#       be visible through DSM, since it appears DSM only uses the LAN1/eth0
#       interface for DDNS.
#
#       Convert the update code block to a function. That way it's simple to
#       call the function on each iteration of a loop containing hostnames that
#       should be updated.
#
###############################################################################

# Set variables based on parameters.
__USERNAME__="$(echo ${@} | cut -d' ' -f1)"
__PASSWORD__="$(echo ${@} | cut -d' ' -f2)"
__HOSTNAME__="$(echo ${@} | cut -d' ' -f3)"
__DOMAIN__="$(echo ${__HOSTNAME__} | cut -d. -f2-3)"
__MYIP__="$(echo ${@}  | cut -d' ' -f4)"

# System Configuration
__IP_CACHE__=/tmp/gratisdns_ddnsd_ip.txt
__LOGFILE__=/var/log/gratisdns_ddnsd.log


log() {
    __LOGTIME__=$(date +"%b %e %T")
    if [ "${#}" -lt 1 ]; then
        false
    else
        __LOGMSG__="${1}"
    fi
    if [ "${#}" -lt 2 ]; then
        __LOGPRIO__=7
    else
        __LOGPRIO__=${2}
    fi

    #logger -p ${__LOGPRIO__} -t "$(basename ${0})" "${__LOGMSG__}"
    echo "${__LOGTIME__} $(basename ${0}) (${__LOGPRIO__}): ${__LOGMSG__}" >> ${__LOGFILE__}
}

# Get the last known DDNS IP
if [ ! -f ${__IP_CACHE__} ]; then
    # If the file wasn't found, create it to avoid errors.
    echo "127.0.0.1" > ${__IP_CACHE__}
fi
__OLDIP__=$(cat ${__IP_CACHE__})

# Get the current IP
#__MYIP__=$(curl --silent --interface ${__INTERFACE__} "http://automation.whatismyip.com/n09230945.asp")

if [ "${__OLDIP__}" == "${__MYIP__}" ]; then
    log "IP not changed. ${__MYIP__}. Not updating." 6
else
    log "IP changed. ${__OLDIP__} > ${__MYIP__}. Attempting to update DNS." 6

    __URL__="https://ssl.gratisdns.dk/ddns.phtml?u=${__USERNAME__}&p=${__PASSWORD__}&d=${__DOMAIN__}&h=${__HOSTNAME__}&i=${__MYIP__}"

    # The cURL query needs the --insecure option, or the update will fail. I'm
    # assuming this is because there's no CA bundle with cURL in DSM.
    # I could of course add a check to see whether or not there's a local CA
    # bundle, and if it's "out of date", then download one and point to it.
    #
    # Set the location of the CA bundle:
    #__CABUNDLE__="/tmp/cacert.pem"
    #
    # If the CA bundle is more than a week old, fetch a fresh copy:
    #if [ some date comparison here ]; then
    #   curl --silent --continue-at - --output "${__CABUNDLE__}" "http://curl.haxx.se/ca/cacert.pem"
    #fi
    #
    # Update DNS record:
    #__STATUS__=$(curl --silent --cacert "__CABUNDLE__" "${__URL__}")
    __STATUS__=$(curl --silent --insecure "${__URL__}")

    # Output:
    #    When you write your own module, you can use the following words to tell user what happen by print it.
    #    You can use your own message, but there is no multiple-language support.
    #
    #       good -  Update successfully.
    #       nochg - Update successfully but the IP address have not changed.
    #       nohost - The hostname specified does not exist in this user account.
    #       abuse - The hostname specified is blocked for update abuse.
    #       notfqdn - The hostname specified is not a fully-qualified domain name.
    #       badauth - Authenticate failed.
    #       911 - There is a problem or scheduled maintenance on provider side
    #       badagent - The user agent sent bad request(like HTTP method/parameters is not permitted)
    #       badresolv - Failed to connect to  because failed to resolve provider address.
    #       badconn - Failed to connect to provider because connection timeout.
    case ${__STATUS__} in
        'OK<br>')
            echo ${__MYIP__} > ${__IP_CACHE__}
            __OUTPUT__='good'
            ;;
        'OK<br>Opdateret i forvejen')
            __OUTPUT__='nochg'
            ;;
        'Forkerte værdier, opdatering kan ikke laves.<br><br>A record findes ikke.'|'Domæne kan IKKE administreres af bruger')
            __OUTPUT__='nohost'
            ;;
        'Forkerte værdier, opdatering kan ikke laves.<br><br>A record findes ikke.Hostnavn er ulovligt.')
            __OUTPUT__='notfqdn'
            ;;
        'Bruger login: 1Fejl i kodeord, prøv igen. Husk serveren ser forskel på STORE Og små BOGstAvER.'|'Bruger login: Bruger eksistere ikke, husk serveren ser forskel på STORE Og smÅ BOGstAvER.')
            __OUTPUT__='badauth'
            ;;
        'Bruger login: MD5 invalid') # The error from the provider doesn't really match up with the response I forward to DDNSd. But it seems that a malformed URL, f.ex. if the URL isn't enclosed in quotes or contains spaces etc. will give this error.
            __OUTPUT__='badagent'
            ;;
        *)
            __OUTPUT__="${__STATUS__}"
            ;;
    esac
    log "DDNS Response: ${__OUTPUT__}" 6
    printf "%s" "${__OUTPUT__}"
fi