gratisdns.sh

#!/bin/sh

# gratisdns.sh - A GratisDNS.dk DDNSd module for Synology DSM
#
# Author:
#		Brian Schmidt Pedersen (http://blog.briped.net)
#
# Version:
#		1.3.5

# 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.
#
#		You can either add the provider manually or by using the "--install"
#		feature.
#
#		Using the "--install" feature
#		Execute the script with the "--install" option:
#		> gratisdns.sh --install
#		If the script isn't executable, you can prepend sh:
#		> sh gratisdns.sh --install
#
#		This will copy (and overwrite if already exists) the gratisdns.sh file
#		'/sbin/gratisdns.sh' and chmod +x it (make it eXecutable).
#
#		If no other arguments are added to the "--install" option, a provider
#		with the name "GratisDNS.dk" will be added. In order to use more hosts
#		you can add a custom provider name after the "--install" option:
#		> gratisdns.sh --install example.org
#		or
#		> gratisdns.sh --install My Custom Provider
#		This adds a provider with the name "example.org", which will use the
#		GratisDNS.dk DDNS module.
#
#		You don't have to worry about spaces. The script reads everything after
#		"--install" as one string. You might have to beware of using certain
#		characters that might act as an escape character (backslash, ticks,
#		backticks, single- and double quotes spring to mind).
#
#		Manual installation
#		Copy the 'gratisdns.sh' file to the '/sbin' folder:
#		> cp /volume1/homes/USERNAME/gratisdns.sh /sbin/gratisdns.sh
#		The above copy command assumes you have enabled "User home service" on
#		your Synology, and also assumes that the home shares are located on
#		your first volume "volume1".
#
#		Then make the file eXecutable:
#		> chmod +x /sbin/gratisdns.sh
#
#		Then edit the "/etc.defaults/ddnsd_provider.conf" file to add DDNS
#		providers. I only know of 'vi' editor on the Synolgoy devices, which
#		can be a bit annoying to navigate, if you don't know how.
#		Open "/etc.defaults/ddnsd_provider.conf" in vi:
#		> vi /etc.defaults/ddnsd_provider.conf
#		When opened, hold the DOWN ARROW until you reach the end of the config
#		file, then hit (once only) the O key (the letter,not the number). This
#		opens edit mode, below the current line. Then simply type (or paste, 
#		but remember to not paste the # comments) the following:
#		[GratisDNS.dk]
#		        modulepath=/sbin/gratisdns.sh
#		        queryurl=https://ssl.gratisdns.dk/ddns.phtml?u=__USERNAME__&p=__PASSWORD__&d=__DOMAIN__&h=__HOSTNAME__&i=__MYIP__
#
#		You can add multiple sections by adding the above, and changing the
#		text between the square brackets (i.e. [GratisDNS.dk]).
#
#		If you have a DS with two interfaces (like me), and the DDNS/ezCloud
#		interface doesn't show the IP for the right interface, then you can
#		make it, by setting the gateway manually in Network settings, to be the
#		gateway of the interface which you want DDNS to use. Just bear in mind
#		that this also affects which interface all the other services on the DS
#		uses.

# Changelist:
#		1.3.5
#			* Added a simple check, to ensure that DDNS wouldn't update if IP was 0.0.0.0
#				(yes, I've had that happen to me)
#		1.3.4
#			* Changed from cut to awk, to find the __DOMAIN__ from __HOSTNAME__, this
#				is to ensure that the last two delimeters are always found (i.e.
#				'example.org' found from 'example.org', 'sub.example.org' and 
#				'sub.sub.example.org' etc.)
#		1.3.3
#			* Minor fixes and modifications to the "--install" feature.
#		1.3.2
#			+ Modified the "--install" feature to add a custom provider/domain.
#				See the description for more details.
#		1.3.1
#			* Fixed the "--install" feature.
#		1.3.0
#			+ Added a simple "--install" argument which simply appends the GratisDNS
#				provider to the /etc.defaults/ddns_provider.conf file, if not already
#				added.
#		1.2.7
#			* __DOMAIN__ would be incorrect, if using 2nd. or 3rd. (or higher)
#				level subdomains, since it was just the 2nd. and 3rd. delimiter
#				that was returned. Changed to 2nd. delimiter and the rest.
#				Thanks to Mathias Neerup for bringing my attention to this.
#		1.2.6
#			* Just minor changes to the code, so Notepad++ could code-fold :)
#		1.2.5
#			* Changed update_ca_bundle() a bit, since the age checking didn't
#				seem to work before.
#		1.2.4
#			* Fixed script to return "nochg" when IP isn't changed from IPcache
#		1.2.3
#			* Fixed so the IP cache is also updated, even when DDNS provider
#				responds with 'nochg', since obivously then the cached IP were
#				wrong.
#		1.2.2
#			* Fixed some return code checking.
#		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:
#
###############################################################################

{ # Read the supplied arguments into variables used in this script.
	__USERNAME__="$(echo ${@} | cut -d' ' -f1)"
	__PASSWORD__="$(echo ${@} | cut -d' ' -f2)"
	__HOSTNAME__="$(echo ${@} | cut -d' ' -f3)"
	__DOMAIN__="$(echo ${__HOSTNAME__} | awk -F. '{print $(NF-1) "." $NF}')"
	__MYIP__="$(echo ${@}  | cut -d' ' -f4)"
	# Alternate methods for getting the IP:
	#__INTERFACE_IP__="$(ifconfig ${__INTERFACE__} | sed '/inet\ /!d;s/.*r://g;s/\ .*//g')"
	#__MYIP__=$(curl --silent --interface ${__INTERFACE__} "http://automation.whatismyip.com/n09230945.asp")

	# 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"
	# The ddns_provider.conf path and filename:
	__CONFIGFILE__="/etc.defaults/ddns_provider.conf"
	# The scriptfile (this file) path and filename (used for the --install parameter):
	__SCRIPTFILE__="/sbin/gratisdns.sh"
}
if [ "$(echo ${@} | cut -d' ' -f1)" == "--install" ]; then
	cp -f ${0} ${__SCRIPTFILE__}
	chmod +x ${__SCRIPTFILE__}

	if [ "$(echo ${@} | cut -d' ' -f2-)" == "--install" ]; then
		__MYDOMAIN__="GratisDNS.dk"
	else
		__MYDOMAIN__="$(echo ${@} | cut -d' ' -f2-)"
	fi
	if [ ! $(grep "${__MYDOMAIN__}" ${__CONFIGFILE__}) ]; then
		# Add the custom domain to the ddns_provider.conf file.
		echo "[${__MYDOMAIN__}]" >> ${__CONFIGFILE__}
		echo "        modulepath=/sbin/gratisdns.sh" >> ${__CONFIGFILE__}
		echo "        queryurl=https://ssl.gratisdns.dk/ddns.phtml?u=__USERNAME__&p=__PASSWORD__&d=__DOMAIN__&h=__HOSTNAME__&i=__MYIP__" >> ${__CONFIGFILE__}
		echo "Added '${__MYDOMAIN__}' to the DDNS Provider list."
	fi
	echo "Done!"
	exit
fi

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__=${__MAXAGE__}" 7
	local download="0"
	if [ ! -f "${__CA_BUNDLE__}" ]; then
		log "update_ca_bundle(): Local CA bundle doesn't exist. Set to download." 7
		download="1"
	fi
	if [ "$(find '${__CA_BUNDLE__}' -type f -mtime +${__MAXAGE__})" = "${__CA_BUNDLE__}" ]; then
		log "update_ca_bundle(): Local CA bundle older than ${__MAXAGE__} days. Set to download." 7
		download="1"
	fi
	if [ "${download}" = "1" ]; then
		curl --silent --output "${__CA_BUNDLE__}" "http://curl.haxx.se/ca/cacert.pem"
		if [ "${?}" -ne "0" ]; 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 "${__URL__}")
	fi
	if [ "${?}" -ne "0" ]; 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')
			echo ${__MYIP__} > ${__IP_CACHE__}
			__STATUS__='nochg'
			true
			;;
		'Forkerte værdier, opdatering kan ikke laves.<br><br>A record findes ikke.'|'Domæne kan IKKE administreres af bruger')
			__STATUS__='nohost'
			false
			;;
		'Forkerte værdier, opdatering kan ikke laves.<br><br>A record findes ikke.Hostnavn er ulovligt.')
			__STATUS__='notfqdn'
			false
			;;
		'Bruger login: 1Fejl i kodeord, prøv igen. Husk serveren ser forskel på STORE Og små BOGstAvER.'|'Bruger login: Bruger eksistere ikke, husk serveren ser forskel på STORE Og smÅ BOGstAvER.')
			__STATUS__='badauth'
			false
			;;
		'Bruger login: MD5 invalid')
			# The error from the provider doesn't really match up with the 
			# status I forward to DDNSd. But it seems that a malformed URL,
			# such as if the URL isn't enclosed in quotes or contains spaces
			# etc. will give this error.
			__STATUS__='badagent'
			false
			;;
		*)
			__STATUS__="${__RESPONSE__}"
			false
			;;
	esac
	log "update_ddns(): DDNSd Status: ${__STATUS__}" 6
}

{ # 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 ${__IP_CACHE__})
}
if [ "${__MYIP__}" == "0.0.0.0" ] || [ "${__MYIP__}" == "0.0.0.0" ]; then
	log "IP was '0.0.0.0', which is wrong. Not updating." 5
elif [ "${__OLDIP__}" == "${__MYIP__}" ]; then
	log "IP not changed. ${__MYIP__}. Not updating." 6
	__STATUS__="nochg"
else
	update_ca_bundle "${__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 from DDNS provider."
	__STATUS__="No status returned from update_ddns()."

	log "IP changed. ${__OLDIP__} > ${__MYIP__}. Attempting to update DNS." 6
	update_ddns "${__URL__}"
	if [ "${?}" -ne "0" ]; then
		log "update_dns(): ${__RESPONSE__}" 3
	else
		log "update_dns(): ${__RESPONSE__}" 6
	fi
fi
printf "%s" "${__STATUS__}"