GratisDNS.sh

#!/bin/sh

# gratisdns.sh - A GratisDNS.dk DDNSd module for Synology DSM
#
# Author:
#       Brian Schmidt Pedersen (http://briped.net)
#
# Version:
#       1.2.1
#
# 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:
#       1.2.1
#           + Added more debug logging.
#       1.2.0
#           + Moved the entire update ddns routine into its own function.
#           + Moved the CA bundle checking and updating into its own function.
#       1.1.0
#           + Changed the cURL update query to use CA bundle, for better
#               security.
#       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.
#
###############################################################################

# 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)"

# Where to store the IP used for the last DNS update:
__IP_CACHE__="/tmp/gratisdns_ddnsd_ip.txt"
# Where to store the logfile:
__LOGFILE__="/var/log/gratisdns_ddnsd.log"
# Where to store the CA bundle:
__CA_BUNDLE__="/tmp/cacert.pem"

log() {
    # Severity Levels:
    # 0 Emergency       System is unusable.
    #       A "panic" condition usually affecting multiple apps/servers/sites.
    #       At this level it would usually notify all tech staff on call.
    # 1 Alert           Action must be taken immediately.
    #       Should be corrected immediately, therefore notify staff who can fix
    #       the problem.An example would be the loss of a backup ISP connection
    # 2 Critical        Critical conditions.
    #       Should be corrected immediately, but indicates failure in a primary
    #       system, an example is a loss of primary ISP connection.
    # 3 Error           Error conditions.
    #       Non-urgent failures, these should be relayed to developers or
    #       admins; each item must be resolved within a given time.
    # 4 Warning         Warning conditions.
    #       Warning messages, not an error, but indication that an error will
    #       occur if action is not taken, e.g. file system 85% full - each item
    #       must be resolved within a given time.
    # 5 Notice          Normal but significant condition.
    #       Events that are unusual but not error conditions - might be
    #       summarized in an email to developers or admins to spot potential
    #       problems - no immediate action required.
    # 6 Informational   Informational messages.
    #       Normal operational messages - may be harvested for reporting,
    #       measuring throughput, etc - no action required.
    # 7 Debug           Debug-level messages.
    #       Info useful to developers for debugging the application, not useful
    #       during operations.
    __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__}
}

update_ca_bundle() {
    if [ ! -z "${1}" ]; then
        __CA_BUNDLE__="${1}"
    else
        __CA_BUNDLE__="${__CA_BUNDLE__}"
    fi
    log "update_ca_bundle(): __CA_BUNDLE__=${__CA_BUNDLE__}" 7
    if [ ! -z "{2}" ]; then
        __MAXAGE__="${2}"
    else
        __MAXAGE__="7"
    fi
    log "update_ca_bundle(): __MAXAGE__=${__MAXAGE}" 7
    if [ test $(find "${__CA_BUNDLE__}" -mtime +${__MAXAGE__}) -o ! -f "${__CA_BUNDLE__}" ]; then
        log "update_ca_bundle(): Local CA bundle older than ${__MAXAGE__} days, or doesn't exist. Attempting to download fresh copy." 6
        curl --silent --output "${__CA_BUNDLE__}" "http://curl.haxx.se/ca/cacert.pem"
        if [ ${?} ]; then
            log "update_ca_bundle: cURL returned error code ${?} while trying to download CA bundle." 4
        fi
    fi
}

update_ddns() {
    if [ -z "${1}" ]; then
        log "update_ddns(): Missing Argument. URL string required." 3
        false
    else
        __URL__="${1}"
    fi

    # Update DNS record:
    if [ -f "${__CA_BUNDLE__}" ]; then
        log "update_ddns(): Updating using --cacert \"${__CA_BUNDLE__}\"." 7
        __RESPONSE__=$(curl --silent --cacert "${__CA_BUNDLE__}" "${__URL__}")
    else
        log "update_ddns(): Updating using --insecure." 7
        __RESPONSE__=$(curl --silent --insecure "${__URL__}")
    fi
    if [ ${?} ]; then
        log "update_ddns(): cURL returned error code ${?} while trying to update DDNS." 3
        false
    fi
    log "update_ddns(): __RESPONSE__=${__RESPONSE__}" 7

    # 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 ${__RESPONSE__} in
        'OK<br>')
            echo ${__MYIP__} > ${__IP_CACHE__}
            __STATUS__='good'
            true
            ;;
        'OK<br>Opdateret i forvejen')
            __STATUS__='nochg'
            true
            ;;
        'Forkerte værdier, opdatering kan ikke laves.<br><br>A record findes ikke.'|'Domæne kan IKKE administreres af bruger')
            __STATUS__='nohost'
            false
            ;;
        'Forkerte værdier, opdatering kan ikke laves.<br><br>A record findes ikke.Hostnavn er ulovligt.')
            __STATUS__='notfqdn'
            false
            ;;
        'Bruger login: 1Fejl i kodeord, prøv igen. Husk serveren ser forskel på STORE Og små BOGstAvER.'|'Bruger login: Bruger eksistere ikke, husk serveren ser forskel på STORE Og smÅ BOGstAvER.')
            __STATUS__='badauth'
            false
            ;;
        'Bruger login: MD5 invalid')
            # The error from the provider doesn't really match up with the
            # status I forward to DDNSd. But it seems that a malformed URL,
            # such as if the URL isn't enclosed in quotes or contains spaces
            # etc. will give this error.
            __STATUS__='badagent'
            false
            ;;
        *)
            __STATUS__="${__RESPONSE__}"
            false
            ;;
    esac
    log "DDNSd Status: ${__STATUS__}" 6
}

# Get the current IP
#__INTERFACE_IP__="$(ifconfig ${__INTERFACE__} | sed '/inet\ /!d;s/.*r://g;s/\ .*//g')"
#__MYIP__=$(curl --silent --interface ${__INTERFACE__} "http://automation.whatismyip.com/n09230945.asp")

# 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__})

if [ "${__OLDIP__}" == "${__MYIP__}" ]; then
    log "IP not changed. ${__MYIP__}. Not updating." 6
else
    update_ca_bundle "${__CA_BUNDLE__}" "7"

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

    # Set the response and status variables, so they're available globally.
    # That way I can read them outside the update_ddns() function.
    __RESPONSE__="No response returned."
    __STATUS__="No status returned."

    log "IP changed. ${__OLDIP__} > ${__MYIP__}. Attempting to update DNS." 6
    update_ddns "${__URL__}"
    if [ ${?} ]; then
        log "update_dns(): ${__RESPONSE__}" 3
    else
        log "update_dns(): ${__RESPONSE__}" 6
    fi
    printf "%s" "${__STATUS__}"
fi