#!/usr/bin/env bash
set -euo pipefail


## CONSTANTS ##
readonly REGEX_IP_ADDRESS="^((([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])(\.([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])){3})|(([0-9a-f]{1,4}:){7,7}[0-9a-f]{1,4}|([0-9a-f]{1,4}:){1,7}:|([0-9a-f]{1,4}:){1,6}:[0-9a-f]{1,4}|([0-9a-f]{1,4}:){1,5}(:[0-9a-f]{1,4}){1,2}|([0-9a-f]{1,4}:){1,4}(:[0-9a-f]{1,4}){1,3}|([0-9a-f]{1,4}:){1,3}(:[0-9a-f]{1,4}){1,4}|([0-9a-f]{1,4}:){1,2}(:[0-9a-f]{1,4}){1,5}|[0-9a-f]{1,4}:((:[0-9a-f]{1,4}){1,6})|:((:[0-9a-f]{1,4}){1,7}|:)|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-f]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])))$"
readonly DATA_DIR="/etc/openvpn-data"
readonly EASYRSA_DIR="${DATA_DIR}/easyrsa"
readonly DATA_SERVER_DIR="${DATA_DIR}/server"
readonly DATA_CLIENT_DIR="${DATA_DIR}/client"
readonly ARG_LIST=("$@")


## LIB: COLOR ##
color_bold=""
color_underline=""
color_standout=""
color_normal=""
color_black=""
color_red=""
color_green=""
color_yellow=""
color_blue=""
color_magenta=""
color_cyan=""
color_white=""
if test -t 1; then
	# check count of supported colors
	color_count=$(tput colors)
	if [[ ! -z "$color_count" && "$color_count" -ge 8 ]]; then
		color_bold="$(tput bold)"
		color_underline="$(tput smul)"
		color_standout="$(tput smso)"
		color_normal="$(tput sgr0)"
		color_black="$(tput setaf 0)"
		color_red="$(tput setaf 1)"
		color_green="$(tput setaf 2)"
		color_yellow="$(tput setaf 3)"
		color_blue="$(tput setaf 4)"
		color_magenta="$(tput setaf 5)"
		color_cyan="$(tput setaf 6)"
		color_white="$(tput setaf 7)"
	fi
fi


## LIB: LOG ##
log_debug(){
	echo -ne "${color_green}[DEBUG]${color_normal} " 1>&2
	echo "$1" 1>&2
}
log_info(){
	echo -ne "${color_blue}[INFO ]${color_normal} " 1>&2
	echo "$1" 1>&2
}
log_warn(){
	echo -ne "${color_yellow}[WARN ]${color_normal} " 1>&2
	echo "$1" 1>&2
}
log_error(){
	echo -ne "${color_red}[ERROR]${color_normal} " 1>&2
	echo "$1" 1>&2
	exit 1
}



#
# Explain usage of script.
#
clientmgmt_help(){
	echo "Usage: $0 <command> [...args]"
	echo
	echo "Commands:"
	echo "    add [name]     - Generate new client keys and output its config"
	echo "    list           - List registered client keys"
	echo "    revoke [name]  - Revoke a client's keys"
	echo
	echo "    help           - Display this help message and exit"
}



#
# Run command `add`.
#
clientmgmt_add(){
	## GET NAME ##
	local exit=0
	local name
	name=$(clientmgmt_askname noexist) || exit=$?
	[[ "$exit" -gt 0 ]] && exit 1
	
	
	## GET PUBLIC IP ##
	# ask whether auto-detection should be used
	local answer="x"
	local first=0
	until [[ -z "$answer" || "$answer" =~ ^(Y|y|N|n)$ ]]; do
		[[ "$first" -le 0 ]] && first=1 || echo "Invalid answer '$answer'"
		read -ep "Auto-detect public IP-Address using icanhazip.com? [Y/n]: " answer
	done
	
	# maybe do auto-detection
	local public_ip=""
	if [[ ! "$answer" =~ ^(N|n)$ ]]; then
		local exit=0
		local icanhazip
		icanhazip=$(wget -O - -q icanhazip.com) || exit=$?
		
		if [[ "$exit" -le 0 && "$icanhazip" =~ $REGEX_IP_ADDRESS ]]; then
			public_ip="$icanhazip"
			log_info "Found public IP-Address: '$public_ip'"
			
		else
			log_warn "Failed to auto-detect public IP-Address"
		fi
	fi
	
	# use ask as fallback
	local first=0
	until [[ "$public_ip" =~ $REGEX_IP_ADDRESS ]]; do
		[[ "$first" -le 0 ]] && first=1 || echo "Invalid IP-Address '$public_ip'"
		read -ep "Public IP-Address: " public_ip
	done
	
	
	## AUTO-DETECT PROTO AND PORT ##
	local proto
	local port
	
	# stream server config
	while IFS= read -r line; do
		# trim whitespaces
		line=$(echo "$line" | sed -E "s/^\s*//g" | sed -E "s/\s*$//g")
		
		# ignore blank lines and comments
		[[ "$line" == "" || "$line" =~ ^# ]] && continue
		
		# match proto
		if [[ "$line" =~ ^proto[[:blank:]] ]]; then
			if [[ ! "$line" =~ ^proto[[:blank:]]+(tcp|udp)$ ]]; then
				log_warn "Unexpected config line format for key 'proto': '$line'"
				continue
			fi
			proto=$(echo "$line" | sed -E "s/^proto[[:blank:]]+(tcp|udp)$/\1/g")
		fi
		
		# match port
		if [[ "$line" =~ ^port[[:blank:]] ]]; then
			if [[ ! "$line" =~ ^port[[:blank:]]+([0-9]+)$ ]]; then
				log_warn "Unexpected config line format for key 'port': '$line'"
				continue
			fi
			local parsed_port=$(echo "$line" | sed -E "s/^port[[:blank:]]+([0-9]+)$/\1/g")
			if [[ "$parsed_port" -le 0 || "$parsed_port" -gt 65535 ]]; then
				log_warn "Configured port number out of range: '$parsed_port'"
				continue
			fi
			port="$parsed_port"
		fi
	done < "${DATA_SERVER_DIR}/server.conf"
	
	# validate
	if [[ -z "${proto:+x}" ]]; then
		proto="udp"
		log_warn "Unable to auto-detect proto from server config file; using fallback: '$proto'"
	fi
	if [[ -z "${port:+x}" ]]; then
		port="1194"
		log_warn "Unable to auto-detect port from server config file; using fallback: '$port'"
	fi
	
	
	## GENERATE CLIENT KEYS ##
	local prev_pwd="$PWD" && cd "$EASYRSA_DIR"
	log_info "Generating client keys"
	/usr/bin/easyrsa --batch --days=7300 build-client-full "$name" nopass
	cd "$prev_pwd"
	
	
	## BUILD CLIENT CONFIG ##
	# header
	echo
	echo -e "${color_magenta}Client Config (${name}.ovpn):${color_normal}"
	echo -e "${color_magenta}----------------------------------------------------------------${color_normal}"
	
	# static content
	echo "client
dev tun
proto $proto
remote $public_ip $port
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
auth SHA512
ignore-unknown-option block-outside-dns
verb 3"
	echo
	
	# ca cert
	echo "<ca>"
	cat "${EASYRSA_DIR}/pki/ca.crt"
	echo "</ca>"
	
	# client cert
	echo "<cert>"
	sed -ne '/BEGIN CERTIFICATE/,$ p' "${EASYRSA_DIR}/pki/issued/${name}.crt"
	echo "</cert>"
	
	# client key
	echo "<key>"
	cat "${EASYRSA_DIR}/pki/private/${name}.key"
	echo "</key>"
	
	# tls-crypt key
	echo "<tls-crypt>"
	sed -ne '/BEGIN OpenVPN Static key/,$ p' "${DATA_SERVER_DIR}/tls-crypt.key"
	echo "</tls-crypt>"
	
	# footer
	echo -e "${color_magenta}----------------------------------------------------------------${color_normal}"
}



#
# Run command `revoke`.
#
clientmgmt_revoke(){
	## GET NAME ##
	local exit=0
	local name
	name=$(clientmgmt_askname exist) || exit=$?
	[[ "$exit" -gt 0 ]] && exit 1
	
	
	## REVOKE CLIENT KEYS ##
	local prev_pwd="$PWD" && cd "$EASYRSA_DIR"
	log_info "Revoking client keys"
	
	# revoke keys
	/usr/bin/easyrsa --batch revoke "$name"
	
	# update revoke list
	/usr/bin/easyrsa --batch --days=7300 gen-crl
	chown nobody:nobody pki/crl.pem
	
	# restore pwd
	cd "$prev_pwd"
	
	# print info
	log_info "Client revoked: '$name'"
}



#
# Run command `list`.
#
clientmgmt_list(){
	## GET LIST ##
	list=$(clientmgmt_clientlist)
	
	
	## PRINT ##
	# warn if there are no clients
	if [[ "$list" == "" ]]; then
		log_warn "No clients registered"
		exit 0
	fi
	
	# list
	echo "Clients:"
	for one_client_name in $list; do
		echo "    $one_client_name"
	done
}



#
# HELPER: Parse name parameter or ask if not provided.
# 
# @param $1		noexist:		Expect this name to be unused
#				exist:			Expect this name to exist already.
# 
# @return		Name entered.
# @exit			0:		Returned name is valid
#				1:		Returned name is invalid.
#
clientmgmt_askname(){
	## ASK ##
	local answer=""
	local first=0
	if [[ "${ARG_LIST[1]:+x}" ]]; then
		answer="${ARG_LIST[1]}"
		first=1
	fi
	until [[ "$answer" =~ ^[abcdefghijklmnopqrstuvwxyz0123456789-]{2,64}$ ]]; do
		[[ "$first" -le 0 ]] && first=1 || echo "Invalid client name '$answer'" 1>&2
		read -ep "Client name: " answer
	done
	
	
	## VALIDATE ##
	# check for reserved names
	if [[ "$answer" =~ ^(ca|server)$ ]]; then
		log_error "Name is reserved for internal use: '$answer'"
	fi
	
	# make sure name is exists or does not exist
	case "$1" in
		noexist)
			if [[ -f "${EASYRSA_DIR}/pki/issued/${answer}.crt" ]]; then
				log_error "Name already in use: '$answer'"
			fi
		;;
		
		exist)
			if [[ ! -f "${EASYRSA_DIR}/pki/issued/${answer}.crt" ]]; then
				log_error "Client does not exist: '$answer'"
			fi
		;;
		
		*) log_error "Unknown exist goal: '$1'";;
	esac
	
	
	## RETURN ##
	echo -n "$answer"
	return 0
}



#
# GETTER: Get list of registered client names.
# 
# @return		Space separated list of registered client names.
#
clientmgmt_clientlist(){
	## GET LIST ##
	# get from directory
	local rawlist=$(echo -n ${EASYRSA_DIR}/pki/issued/*.crt)
	
	# build list
	local list=""
	for one_cert in $rawlist; do
		filename=$(basename $one_cert)
		[[ "$filename" == "server.crt" ]] && continue
		list="$list $(echo ${filename} | sed -E 's/\.crt$//g')"
	done
	list="$(echo $list | xargs)"
	
	
	## RETURN ##
	echo -n "$list"
	return 0
}



#
# HELPER: Make sure config and key files have been fully initialized.
#
clientmgmt_check_init_done(){
	[[ -f "${DATA_SERVER_DIR}/server.conf" ]] && return 0
	log_error "Server is still initializing config and key files; try again in a few seconds"
}



## MAIN ##
case ${1:-""} in
	add)
		clientmgmt_check_init_done
		clientmgmt_add
		exit 0
	;;
	
	list)
		clientmgmt_check_init_done
		clientmgmt_list
		exit 0
	;;
	
	revoke)
		clientmgmt_check_init_done
		clientmgmt_revoke
		exit 0
	;;
	
	help)
		clientmgmt_help
		exit 0
	;;
	
	"")
		log_error "No command given; See '$0 help' for usage information"
		exit 1
	;;
	
	*)
		log_error "Invalid command '$1'; See '$0 help' for usage information"
		exit 1
	;;
esac