#!/bin/bash

# Secure OpenVPN server installer for Debian, Ubuntu, CentOS and Fedora
# https://github.com/angristan/openvpn-install

function isRoot () {
	if [ "$EUID" -ne 0 ]; then
		return 1
	fi
}

function tunAvailable () {
	if [ ! -e /dev/net/tun ]; then
		return 1
	fi
}

function checkOS () {
	if [[ -e /etc/debian_version ]]; then
		OS="debian"
		# Getting the version number, to verify that a recent version of OpenVPN is available
		source /etc/os-release
		if [[ ! $VERSION_ID =~ (8|9|16.04|17.10|18.04) ]]; then
			echo "⚠️ Your version of Debian/Ubuntu is not supported."
			echo ""
			echo "However, if you're using Debian unstable/testing, or Ubuntu beta, then you can continue."
			echo "Keep in mind they are not supported, though."
			echo ""
			while [[ $CONTINUE != "y" && $CONTINUE != "n" ]]; do
				read -rp "Continue? [y/n]: " -e CONTINUE
			done
			if [[ "$CONTINUE" = "n" ]]; then
				echo "Ok, bye!"
				exit 1
			fi
		fi
	elif [[ -e /etc/fedora-release ]]; then
		OS=fedora
	elif [[ -e /etc/centos-release ]]; then
		if ! grep -qs "^CentOS Linux release 7" /etc/centos-release; then
			echo "Your version of CentOS is not supported."
			echo "The script only support CentOS 7."
			echo ""
			unset CONTINUE
			while [[ $CONTINUE != "y" && $CONTINUE != "n" ]]; do
				read -rp "Continue anyway? [y/n]: " -e CONTINUE
			done
			if [[ "$CONTINUE" = "n" ]]; then
				echo "Ok, bye!"
				exit 1
			fi
		fi
		OS=centos
	else
		echo "Looks like you aren't running this installer on a Debian, Ubuntu, Fedora or CentOS system"
		exit 1
	fi
}

function initialCheck () {
	if ! isRoot; then
		echo "Sorry, you need to run this as root"
		exit 1
	fi
	if ! tunAvailable; then
		echo "TUN is not available"
		exit 1
	fi
	checkOS
}

function installUnbound () {
	if [[ ! -e /etc/unbound/unbound.conf ]]; then

		if [[ "$OS" = "debian" ]]; then
			apt-get install -y unbound

			# Configuration
			echo 'interface: 10.8.0.1
access-control: 10.8.0.1/24 allow
hide-identity: yes
hide-version: yes
use-caps-for-id: yes
prefetch: yes' >> /etc/unbound/unbound.conf

		elif [[ "$OS" = "centos" ]]; then
			yum install -y unbound

			# Configuration
			sed -i 's|# interface: 0.0.0.0$|interface: 10.8.0.1|' /etc/unbound/unbound.conf
			sed -i 's|# access-control: 127.0.0.0/8 allow|access-control: 10.8.0.1/24 allow|' /etc/unbound/unbound.conf
			sed -i 's|# hide-identity: no|hide-identity: yes|' /etc/unbound/unbound.conf
			sed -i 's|# hide-version: no|hide-version: yes|' /etc/unbound/unbound.conf
			sed -i 's|use-caps-for-id: no|use-caps-for-id: yes|' /etc/unbound/unbound.conf

		elif [[ "$OS" = "fedora" ]]; then
			dnf install -y unbound

			# Configuration
			sed -i 's|# interface: 0.0.0.0$|interface: 10.8.0.1|' /etc/unbound/unbound.conf
			sed -i 's|# access-control: 127.0.0.0/8 allow|access-control: 10.8.0.1/24 allow|' /etc/unbound/unbound.conf
			sed -i 's|# hide-identity: no|hide-identity: yes|' /etc/unbound/unbound.conf
			sed -i 's|# hide-version: no|hide-version: yes|' /etc/unbound/unbound.conf
			sed -i 's|# use-caps-for-id: no|use-caps-for-id: yes|' /etc/unbound/unbound.conf
		fi

		if [[ ! "$OS" =~ (fedora|centos) ]];then
			# DNS Rebinding fix
			echo "private-address: 10.0.0.0/8
private-address: 172.16.0.0/12
private-address: 192.168.0.0/16
private-address: 169.254.0.0/16
private-address: fd00::/8
private-address: fe80::/10
private-address: 127.0.0.0/8
private-address: ::ffff:0:0/96" >> /etc/unbound/unbound.conf
		fi
	else # Unbound is already installed
		echo 'include: /etc/unbound/openvpn.conf' >> /etc/unbound/unbound.conf

		# Add Unbound 'server' for the OpenVPN subnet
		echo 'server:
interface: 10.8.0.1
access-control: 10.8.0.1/24 allow
hide-identity: yes
hide-version: yes
use-caps-for-id: yes
prefetch: yes
private-address: 10.0.0.0/8
private-address: 172.16.0.0/12
private-address: 192.168.0.0/16
private-address: 169.254.0.0/16
private-address: fd00::/8
private-address: fe80::/10
private-address: 127.0.0.0/8
private-address: ::ffff:0:0/96' > /etc/unbound/openvpn.conf
	fi

		systemctl enable unbound
		systemctl restart unbound
}

function installOpenVPN () {
	echo "Welcome to the OpenVPN installer!"
	echo "The git repository is available at: https://github.com/angristan/openvpn-install"
	echo ""

	echo "I need to ask you a few questions before starting the setup."
	echo "You can leave the default options and just press enter if you are ok with them."
	echo ""
	echo "I need to know the IPv4 address of the network interface you want OpenVPN listening to."
	echo "Unless your server is behind NAT, it should be your public IPv4 address."

	# Detect public IPv4 address and pre-fill for the user
	IP=$(ip addr | grep 'inet' | grep -v inet6 | grep -vE '127\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | grep -oE '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | head -1)
	read -rp "IP address: " -e -i "$IP" IP
	# If $IP is a private IP address, the server must be behind NAT
	if echo "$IP" | grep -qE '^(10\.|172\.1[6789]\.|172\.2[0-9]\.|172\.3[01]\.|192\.168)'; then
		echo ""
		echo "It seems this server is behind NAT. What is its public IPv4 address?"
		echo "We need it for the clients to connect to the server."
		until [[ "$PUBLICIP" =~ ^((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])$ ]];do
			read -rp "Public IPv4 address: " -e PUBLICIP
		done
	fi

	echo ""
	echo "Checking for IPv6 connectivity..."
	echo ""
	if ping -c4 ipv6.google.com > /dev/null 2>&1; then
		echo "Your host appears to have IPv6 connectivity."
		SUGGESTION="y"
	else
		echo "Your host does not appear to have IPv6 connectivity."
		SUGGESTION="n"
	fi
	echo ""
	# Ask the user if they want to enable IPv6 regardless its availability.
	while [[ $IPV6_SUPPORT != "y" && $IPV6_SUPPORT != "n" ]]; do
		read -rp "Do you want to enable IPv6 support (NAT)? [y/n]: " -e -i $SUGGESTION IPV6_SUPPORT
	done
	echo ""
	echo "What port do you want OpenVPN to listen to?"
	echo "   1) Default: 1194"
	echo "   2) Custom"
	echo "   3) Random [49152-65535]"
	until [[ "$PORT_CHOICE" =~ ^[1-3]$ ]]; do
		read -rp "Port choice [1-3]: " -e -i 1 PORT_CHOICE
	done
	case $PORT_CHOICE in
		1)
			PORT="1194"
		;;
		2)
			until [[ "$PORT" =~ ^[0-9]+$ ]] && [ "$PORT" -ge 1 ] && [ "$PORT" -le 65535 ]; do
				read -rp "Custom port [1-65535]: " -e -i 1194 PORT
			done
		;;
		3)
			# Generate random number within private ports range
			PORT=$(shuf -i49152-65535 -n1)
			echo "Random Port: $PORT"
		;;
	esac
	echo ""
	echo "What protocol do you want OpenVPN to use?"
	echo "UDP is faster. Unless it is not available, you shoudn't use TCP."
	echo "   1) UDP"
	echo "   2) TCP"
	until [[ "$PROTOCOL_CHOICE" =~ ^[1-2] ]]; do
		read -rp "Protocol [1-2]: " -e -i 1 PROTOCOL_CHOICE
	done
	case $PROTOCOL_CHOICE in
		1)
			PROTOCOL="udp"
		;;
		2)
			PROTOCOL="tcp"
		;;
	esac
	echo ""
	echo "What DNS resolvers do you want to use with the VPN?"
	echo "   1) Current system resolvers (from /etc/resolv.conf)"
	echo "   2) Self-hosted DNS Resolver (Unbound)"
	echo "   3) Cloudflare (Anycast: worldwide)"
	echo "   4) Quad9 (Anycast: worldwide)"
	echo "   5) FDN (France)"
	echo "   6) DNS.WATCH (Germany)"
	echo "   7) OpenDNS (Anycast: worldwide)"
	echo "   8) Google (Anycast: worldwide)"
	echo "   9) Yandex Basic (Russia)"
	echo "   10) AdGuard DNS (Russia)"
	until [[ "$DNS" =~ ^[0-9]+$ ]] && [ "$DNS" -ge 1 ] && [ "$DNS" -le 10 ]; do
		read -rp "DNS [1-10]: " -e -i 3 DNS
			if [[ $DNS == 2 ]] && [[ -e /etc/unbound/unbound.conf ]]; then
				echo ""
				echo "Unbound is already installed."
				echo "You can allow the script to configure it in order to use it from your OpenVPN clients"
				echo "We will simply add a second server to /etc/unbound/unbound.conf for the OpenVPN subnet."
				echo "No changes are made to the current configuration."
				echo ""

				while [[ $CONTINUE != "y" && $CONTINUE != "n" ]]; do
					read -rp "Apply configuration changes to Unbound? [y/n]: " -e CONTINUE
				done
				if [[ $CONTINUE = "n" ]];then
					# Break the loop and cleanup
					unset DNS
					unset CONTINUE
				fi
			fi
	done
	echo ""
	echo "Do you want to customize encryption settings?"
	echo "Unless you know what you're doing, you should stick with the default parameters provided by the script."
	echo "Note that whatever you choose, all the choices presented in the script are safe. (Unlike OpenVPN's defaults)"
	echo "See https://github.com/angristan/openvpn-install#encryption to learn more."
	echo ""
	until [[ $CUSTOMIZE_ENC =~ (y|n) ]]; do
		read -rp "Customize encryption settings? [y/n]: " -e -i n CUSTOMIZE_ENC
	done
	if [[ $CUSTOMIZE_ENC == "n" ]];then
		# Use default, sane and fast paramters
		CIPHER="cipher AES-128-CBC"
		DH_KEY_SIZE="2048"
		RSA_KEY_SIZE="2048"
	else
		echo ""
		echo "Choose which cipher you want to use for the data channel:"
		echo "   1) AES-128-CBC (recommended)"
		echo "   2) AES-192-CBC"
		echo "   3) AES-256-CBC"
		until [[ "$CIPHER_CHOICE" =~ ^[0-9]+$ ]] && [ "$CIPHER_CHOICE" -ge 1 ] && [ "$CIPHER_CHOICE" -le 3 ]; do
			read -rp "Cipher [1-7]: " -e -i 1 CIPHER_CHOICE
		done
		case $CIPHER_CHOICE in
			1)
				CIPHER="cipher AES-128-CBC"
			;;
			2)
				CIPHER="cipher AES-192-CBC"
			;;
			3)
				CIPHER="cipher AES-256-CBC"
			;;
		esac
		echo ""
		echo "Choose what size of Diffie-Hellman key you want to use:"
		echo "   1) 2048 bits (fastest)"
		echo "   2) 3072 bits (recommended, best compromise)"
		echo "   3) 4096 bits (most secure)"
		until [[ "$DH_KEY_SIZE_CHOICE" =~ ^[0-9]+$ ]] && [ "$DH_KEY_SIZE_CHOICE" -ge 1 ] && [ "$DH_KEY_SIZE_CHOICE" -le 3 ]; do
			read -rp "DH key size [1-3]: " -e -i 2 DH_KEY_SIZE_CHOICE
		done
		case $DH_KEY_SIZE_CHOICE in
			1)
				DH_KEY_SIZE="2048"
			;;
			2)
				DH_KEY_SIZE="3072"
			;;
			3)
				DH_KEY_SIZE="4096"
			;;
		esac
		echo ""
		echo "Choose what size of RSA key you want to use for the certificate:"
		echo "   1) 2048 bits (fastest)"
		echo "   2) 3072 bits (recommended, best compromise)"
		echo "   3) 4096 bits (most secure)"
		until [[ "$RSA_KEY_SIZE_CHOICE" =~ ^[0-9]+$ ]] && [ "$RSA_KEY_SIZE_CHOICE" -ge 1 ] && [ "$RSA_KEY_SIZE_CHOICE" -le 3 ]; do
			read -rp "RSA key size [1-3]: " -e -i 2 RSA_KEY_SIZE_CHOICE
		done
		case $RSA_KEY_SIZE_CHOICE in
			1)
				RSA_KEY_SIZE="2048"
			;;
			2)
				RSA_KEY_SIZE="3072"
			;;
			3)
				RSA_KEY_SIZE="4096"
			;;
		esac
	fi
	echo ""
	echo "Okay, that was all I needed. We are ready to setup your OpenVPN server now."
	echo "You will be able to generate a client at the end of the installtion."
	read -n1 -r -p "Press any key to continue..."

	# Get the "public" interface from the default route
	NIC=$(ip -4 route ls | grep default | grep -Po '(?<=dev )(\S+)' | head -1)

	if [[ "$OS" = 'debian' ]]; then
		apt-get update
		apt-get install ca-certificates gnupg -y
		# We add the OpenVPN repo to get the latest version.
		if [[ "$VERSION_ID" = 'VERSION_ID="8"' ]]; then
			echo "deb http://build.openvpn.net/debian/openvpn/stable jessie main" > /etc/apt/sources.list.d/openvpn.list
			wget -O - https://swupdate.openvpn.net/repos/repo-public.gpg | apt-key add -
			apt-get update
		fi
		# Ubuntu >= 16.04 and Debian > 8 have OpenVPN > 2.3.3 without the need of a third party repository.
		apt-get install openvpn iptables openssl wget ca-certificates curl -y
	elif [[ "$OS" = 'centos' ]]; then
		yum install epel-release openvpn iptables openssl wget ca-certificates curl -y
	elif [[ "$OS" = 'fedora' ]]; then
		dnf install openvpn iptables openssl wget ca-certificates curl -y
	fi

	# Find out if the machine uses nogroup or nobody for the permissionless group
	if grep -qs "^nogroup:" /etc/group; then
		NOGROUP=nogroup
	else
		NOGROUP=nobody
	fi

	# An old version of easy-rsa was available by default in some openvpn packages
	if [[ -d /etc/openvpn/easy-rsa/ ]]; then
		rm -rf /etc/openvpn/easy-rsa/
	fi

	# Install the latest version of easy-rsa from source
	local version="3.0.4"
	wget -O ~/EasyRSA-${version}.tgz https://github.com/OpenVPN/easy-rsa/releases/download/v${version}/EasyRSA-${version}.tgz
	tar xzf ~/EasyRSA-${version}.tgz -C ~/
	mv ~/EasyRSA-${version}/ /etc/openvpn/
	mv /etc/openvpn/EasyRSA-${version}/ /etc/openvpn/easy-rsa/
	chown -R root:root /etc/openvpn/easy-rsa/
	rm -f ~/EasyRSA-${version}.tgz

	cd /etc/openvpn/easy-rsa/
	# Generate a random, alphanumeric identifier of 16 characters for CN and one for server name
	SERVER_CN="cn_$(head /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 1)"
	SERVER_NAME="server_$(head /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 1)"
	echo "set_var EASYRSA_KEY_SIZE $RSA_KEY_SIZE" > vars
	echo "set_var EASYRSA_REQ_CN $SERVER_CN" >> vars
	# Create the PKI, set up the CA, the DH params and the server certificate
	./easyrsa init-pki
	./easyrsa --batch build-ca nopass
	openssl dhparam -out dh.pem $DH_KEY_SIZE
	./easyrsa build-server-full "$SERVER_NAME" nopass
	EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
	# Generate tls-auth key
	openvpn --genkey --secret /etc/openvpn/tls-auth.key
	# Move all the generated files
	cp pki/ca.crt pki/private/ca.key dh.pem "pki/issued/$SERVER_NAME.crt" "pki/private/$SERVER_NAME.key" /etc/openvpn/easy-rsa/pki/crl.pem /etc/openvpn
	# Make cert revocation list readable for non-root
	chmod 644 /etc/openvpn/crl.pem

	# Generate server.conf
	echo "port $PORT" > /etc/openvpn/server.conf
	if [[ "$IPV6_SUPPORT" = 'n' ]]; then
		echo "proto $PROTOCOL" >> /etc/openvpn/server.conf
	elif [[ "$IPV6_SUPPORT" = 'y' ]]; then
		echo "proto ${PROTOCOL}6" >> /etc/openvpn/server.conf
	fi

	echo "dev tun
user nobody
group $NOGROUP
persist-key
persist-tun
keepalive 10 120
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt" >> /etc/openvpn/server.conf
	
	# DNS resolvers
	case $DNS in
		1)
			# Locate the proper resolv.conf
			# Needed for systems running systemd-resolved
			if grep -q "127.0.0.53" "/etc/resolv.conf"; then
				RESOLVCONF='/run/systemd/resolve/resolv.conf'
			else
				RESOLVCONF='/etc/resolv.conf'
			fi
			# Obtain the resolvers from resolv.conf and use them for OpenVPN
			grep -v '#' $RESOLVCONF | grep 'nameserver' | grep -E -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | while read -r line; do
				echo "push \"dhcp-option DNS $line\"" >> /etc/openvpn/server.conf
			done
		;;
		2)
			echo 'push "dhcp-option DNS 10.8.0.1"' >> /etc/openvpn/server.conf
		;;
		3) # Cloudflare
			echo 'push "dhcp-option DNS 1.0.0.1"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 1.1.1.1"' >> /etc/openvpn/server.conf	
		;;
		4) # Quad9
			echo 'push "dhcp-option DNS 9.9.9.9"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 149.112.112.112"' >> /etc/openvpn/server.conf
		;;
		5) # FDN
			echo 'push "dhcp-option DNS 80.67.169.40"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 80.67.169.12"' >> /etc/openvpn/server.conf
		;;
		6) # DNS.WATCH
			echo 'push "dhcp-option DNS 84.200.69.80"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 84.200.70.40"' >> /etc/openvpn/server.conf
		;;
		7) # OpenDNS
			echo 'push "dhcp-option DNS 208.67.222.222"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 208.67.220.220"' >> /etc/openvpn/server.conf
		;;
		8) # Google
			echo 'push "dhcp-option DNS 8.8.8.8"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 8.8.4.4"' >> /etc/openvpn/server.conf
		;;
		9) # Yandex Basic
			echo 'push "dhcp-option DNS 77.88.8.8"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 77.88.8.1"' >> /etc/openvpn/server.conf
		;;
		10) # AdGuard DNS
			echo 'push "dhcp-option DNS 176.103.130.130"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 176.103.130.131"' >> /etc/openvpn/server.conf
		;;
	esac
	echo 'push "redirect-gateway def1 bypass-dhcp" '>> /etc/openvpn/server.conf

	# IPv6 network settings if needed
	if [[ "$IPV6_SUPPORT" = 'y' ]]; then
		echo 'server-ipv6 fd42:42:42:42::/112
tun-ipv6
push tun-ipv6
push "route-ipv6 2000::/3"
push "redirect-gateway ipv6"' >> /etc/openvpn/server.conf
	fi

	echo "crl-verify crl.pem
ca ca.crt
cert $SERVER_NAME.crt
key $SERVER_NAME.key
tls-auth tls-auth.key 0
dh dh.pem
auth SHA256
$CIPHER
tls-server
tls-version-min 1.2
tls-cipher TLS-DHE-RSA-WITH-AES-128-GCM-SHA256
status /var/log/openvpn/status.log
verb 3" >> /etc/openvpn/server.conf

	# Create log dir
	mkdir -p /var/log/openvpn

	# Enable routing
	echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.d/20-openvpn.conf
	if [[ "$IPV6_SUPPORT" = 'y' ]]; then
		echo 'net.ipv6.conf.all.forwarding=1' >> /etc/sysctl.d/20-openvpn.conf
	fi
	# Avoid an unneeded reboot
	sysctl --system

	# If SELinux is enabled and a custom port was selected, we need this
	if hash sestatus 2>/dev/null; then
		if sestatus | grep "Current mode" | grep -qs "enforcing"; then
			if [[ "$PORT" != '1194' ]]; then
				semanage port -a -t openvpn_port_t -p "$PROTOCOL" "$PORT"
			fi
		fi
	fi

	# Finally, restart and enable OpenVPN
	if [[ "$OS" = 'fedora' ]]; then
		# Workaround to fix OpenVPN service on OpenVZ
		sed -i 's|LimitNPROC|#LimitNPROC|' /usr/lib/systemd/system/openvpn-server@.service
		# Another workaround to keep using /etc/openvpn/
		sed -i 's|/etc/openvpn/server|/etc/openvpn|' /usr/lib/systemd/system/openvpn-server@.service
		systemctl daemon-reload
		systemctl restart openvpn-server@server
		systemctl enable openvpn-server@server
	else
		# Workaround to fix OpenVPN service on OpenVZ
		sed -i 's|LimitNPROC|#LimitNPROC|' /lib/systemd/system/openvpn\@.service
		# Another workaround to keep using /etc/openvpn/
		sed -i 's|/etc/openvpn/server|/etc/openvpn|' /lib/systemd/system/openvpn\@.service
		systemctl daemon-reload
		systemctl restart openvpn@server
		systemctl enable openvpn@server
	fi

	if [[ $DNS == 2 ]];then
		installUnbound
	fi

	# Add iptables rules in two scripts
	mkdir /etc/iptables

	# Script to add rules
	echo "#!/bin/sh
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o $NIC -j MASQUERADE
iptables -A INPUT -i tun0 -j ACCEPT
iptables -A FORWARD -i $NIC -o tun0 -j ACCEPT
iptables -A FORWARD -i tun0 -o $NIC -j ACCEPT
iptables -A INPUT -i $NIC -p $PROTOCOL --dport $PORT -j ACCEPT" > /etc/iptables/add-openvpn-rules.sh

	if [[ "$IPV6_SUPPORT" = 'y' ]]; then
		echo "ip6tables -t nat -A POSTROUTING -s fd42:42:42:42::/112 -o $NIC -j MASQUERADE
ip6tables -A INPUT -i tun0 -j ACCEPT
ip6tables -A FORWARD -i $NIC -o tun0 -j ACCEPT
ip6tables -A FORWARD -i tun0 -o $NIC -j ACCEPT" >> /etc/iptables/add-openvpn-rules.sh
	fi

	# Script to remove rules
	echo "#!/bin/sh
iptables -t nat -D POSTROUTING -s 10.8.0.0/24 -o $NIC -j MASQUERADE
iptables -D INPUT -i tun0 -j ACCEPT
iptables -D FORWARD -i $NIC -o tun0 -j ACCEPT
iptables -D FORWARD -i tun0 -o $NIC -j ACCEPT
iptables -D INPUT -i $NIC -p $PROTOCOL --dport $PORT -j ACCEPT" > /etc/iptables/rm-openvpn-rules.sh

	if [[ "$IPV6_SUPPORT" = 'y' ]]; then
		echo "ip6tables -t nat -D POSTROUTING -s fd42:42:42:42::/112 -o $NIC -j MASQUERADE
ip6tables -D INPUT -i tun0 -j ACCEPT
ip6tables -D FORWARD -i $NIC -o tun0 -j ACCEPT
ip6tables -D FORWARD -i tun0 -o $NIC -j ACCEPT" >> /etc/iptables/rm-openvpn-rules.sh
	fi

	chmod +x /etc/iptables/add-openvpn-rules.sh
	chmod +x /etc/iptables/rm-openvpn-rules.sh

	# Handle the rules via a systemd script
	echo "[Unit]
Description=iptables rules for OpenVPN
Before=network-pre.target
Wants=network-pre.target

[Service]
Type=oneshot
ExecStart=/etc/iptables/add-openvpn-rules.sh
ExecStop=/etc/iptables/rm-openvpn-rules.sh
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target" > /etc/systemd/system/iptables-openvpn.service

	# Enable service and apply rules
	systemctl daemon-reload
	systemctl enable iptables-openvpn
	systemctl start iptables-openvpn

	# If the server is behind a NAT, use the correct IP address for the clients to connect to
	if [[ "$PUBLICIP" != "" ]]; then
		IP=$PUBLICIP
	fi
	
	# client-template.txt is created so we have a template to add further users later
	echo "client" > /etc/openvpn/client-template.txt
	if [[ "$PROTOCOL" = 'udp' ]]; then
		echo "proto udp" >> /etc/openvpn/client-template.txt
	elif [[ "$PROTOCOL" = 'tcp' ]]; then
		echo "proto tcp-client" >> /etc/openvpn/client-template.txt
	fi
	echo "remote $IP $PORT
dev tun
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
verify-x509-name $SERVER_NAME name
auth SHA256
auth-nocache
$CIPHER
tls-client
tls-version-min 1.2
tls-cipher TLS-DHE-RSA-WITH-AES-128-GCM-SHA256
setenv opt block-outside-dns # Prevent Windows 10 DNS leak
verb 3" >> /etc/openvpn/client-template.txt

	# Generate the custom client.ovpn
	newClient
	echo "If you want to add more clients, you simply need to run this script another time!"
}

function newClient () {
	echo ""
	echo "Tell me a name for the client."
	echo "Use one word only, no special characters."

	until [[ "$CLIENT" =~ ^[a-zA-Z0-9_]+$ ]]; do
		read -rp "Client name: " -e CLIENT
	done

	echo ""
	echo "Do you want to protect the configuration file with a password?"
	echo "(e.g. encrypt the private key with a password)"
	echo "   1) Add a passwordless client"
	echo "   2) Use a password for the client"

	until [[ "$PASS" =~ ^[1-2]$ ]]; do
		read -rp "Select an option [1-2]: " -e -i 1 PASS
	done

	cd /etc/openvpn/easy-rsa/ || return
	case $PASS in
		1)
			./easyrsa build-client-full "$CLIENT" nopass
		;;
		2)
		echo "⚠️ You will be asked for the client password below ⚠️"
			./easyrsa build-client-full "$CLIENT"
		;;
	esac

	# Home directory of the user, where the client configuration (.ovpn) will be written
	if [ -e "/home/$CLIENT" ]; then  # if $1 is a user name
		homeDir="/home/$CLIENT"
	elif [ "${SUDO_USER}" ]; then   # if not, use SUDO_USER
		homeDir="/home/${SUDO_USER}"
	else  # if not SUDO_USER, use /root
		homeDir="/root"
	fi

	# Generates the custom client.ovpn
	cp /etc/openvpn/client-template.txt "$homeDir/$CLIENT.ovpn"
	{
		echo "<ca>"
		cat "/etc/openvpn/easy-rsa/pki/ca.crt"
		echo "</ca>"

		echo "<cert>"
		cat "/etc/openvpn/easy-rsa/pki/issued/$CLIENT.crt"
		echo "</cert>"

		echo "<key>"
		cat "/etc/openvpn/easy-rsa/pki/private/$CLIENT.key"
		echo "</key>"
		echo "key-direction 1"

		echo "<tls-auth>"
		cat "/etc/openvpn/tls-auth.key"
		echo "</tls-auth>"
	} >> "$homeDir/$CLIENT.ovpn"

	echo ""
	echo "Client $CLIENT added, the configuration file is available at $homeDir/$CLIENT.ovpn."
	echo "Download the .ovpn file and import it in your OpenVPN client."
}

function revokeClient () {
	NUMBEROFCLIENTS=$(tail -n +2 /etc/openvpn/easy-rsa/pki/index.txt | grep -c "^V")
	if [[ "$NUMBEROFCLIENTS" = '0' ]]; then
		echo ""
		echo "You have no existing clients!"
		exit 1
	fi

	echo ""
	echo "Select the existing client certificate you want to revoke"
	tail -n +2 /etc/openvpn/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | nl -s ') '
	if [[ "$NUMBEROFCLIENTS" = '1' ]]; then
		read -rp "Select one client [1]: " CLIENTNUMBER
	else
		read -rp "Select one client [1-$NUMBEROFCLIENTS]: " CLIENTNUMBER
	fi

	CLIENT=$(tail -n +2 /etc/openvpn/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | sed -n "$CLIENTNUMBER"p)
	cd /etc/openvpn/easy-rsa/
	./easyrsa --batch revoke "$CLIENT"
	EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
	# Cleanup
	rm -f "pki/reqs/$CLIENT.req"
	rm -f "pki/private/$CLIENT.key"
	rm -f "pki/issued/$CLIENT.crt"
	rm -f /etc/openvpn/crl.pem
	cp /etc/openvpn/easy-rsa/pki/crl.pem /etc/openvpn/crl.pem
	chmod 644 /etc/openvpn/crl.pem
	find /home/ -maxdepth 2 -name "$CLIENT.ovpn" -delete
	rm -f "/root/$CLIENT.ovpn"

	echo ""
	echo "Certificate for client $CLIENT revoked."
}

function removeUnbound () {
	# Remove OpenVPN-related config
	sed -i 's|include: \/etc\/unbound\/openvpn.conf||' /etc/unbound/unbound.conf
	rm /etc/unbound/openvpn.conf
	systemctl restart unbound

	until [[ $REMOVE_UNBOUND == "y" || $REMOVE_UNBOUND == "n" ]]; do
		echo ""
		echo "If you were already using Unbound before installing OpenVPN, I removed the configuration related to OpenVPN."
		read -rp "Do you want to completely remove Unbound? [y/n]: " -e REMOVE_UNBOUND
	done

	if [[ "$REMOVE_UNBOUND" = 'y' ]]; then
		# Stop Unbound
		systemctl stop unbound

		if [[ "$OS" = 'debian' ]]; then
			apt-get autoremove --purge -y unbound
		elif [[ "$OS" = 'centos' ]]; then
			yum remove unbound -y
		elif [[ "$OS" = 'fedora' ]]; then
			dnf remove unbound -y
		fi

		rm -rf /etc/unbound/

		echo ""
		echo "Unbound removed!"
	else
		echo ""
		echo "Unbound wasn't removed."
	fi
}

function removeOpenVPN () {
	echo ""
	read -rp "Do you really want to remove OpenVPN? [y/n]: " -e -i n REMOVE
	if [[ "$REMOVE" = 'y' ]]; then
		# Get OpenVPN port from the configuration
		PORT=$(grep '^port ' /etc/openvpn/server.conf | cut -d " " -f 2)

		# Stop OpenVPN
		if [[ "$OS" = 'fedora' ]]; then
			systemctl stop openvpn-server@server
		else
			systemctl stop openvpn@server
		fi

		# Remove the iptables rules related to the script
		systemctl stop iptables-openvpn
		# Cleanup
		systemctl disable iptables-openvpn
		rm /etc/systemd/system/iptables-openvpn.service
		systemctl daemon-reload
		rm /etc/iptables/add-openvpn-rules.sh
		rm /etc/iptables/rm-openvpn-rules.sh

		# SELinux
		if hash sestatus 2>/dev/null; then
			if sestatus | grep "Current mode" | grep -qs "enforcing"; then
				if [[ "$PORT" != '1194' ]]; then
					semanage port -d -t openvpn_port_t -p udp "$PORT"
				fi
			fi
		fi

		if [[ "$OS" = 'debian' ]]; then
			apt-get autoremove --purge -y openvpn
		elif [[ "$OS" = 'centos' ]]; then
			yum remove openvpn -y
		elif [[ "$OS" = 'fedora' ]]; then
			dnf remove openvpn -y
		fi

		# Cleanup
		find /home/ -maxdepth 2 -name "*.ovpn" -delete
		find /root/ -maxdepth 1 -name "*.ovpn" -delete
		rm -rf /etc/openvpn
		rm -rf /usr/share/doc/openvpn*
		rm -f /etc/sysctl.d/20-openvpn.conf

		# Unbound
		if [[ -e /etc/unbound/openvpn.conf ]]; then
			removeUnbound
		fi
		echo ""
		echo "OpenVPN removed!"
	else
		echo ""
		echo "Removal aborted!"
	fi
}

function manageMenu () {
	clear
	echo "Welcome to OpenVPN-install!"
	echo "The git repository is available at: https://github.com/angristan/openvpn-install"
	echo ""
	echo "It looks like OpenVPN is already installed."
	echo ""
	echo "What do you want to do?"
	echo "   1) Add a new user"
	echo "   2) Revoke existing user"
	echo "   3) Remove OpenVPN"
	echo "   4) Exit"
	until [[ "$MENU_OPTION" =~ ^[1-4]$ ]]; do
		read -rp "Select an option [1-4]: " MENU_OPTION
	done

	case $MENU_OPTION in
		1)
			newClient
		;;
		2)
			revokeClient
		;;
		3)
			removeOpenVPN
		;;
		4)
			exit 0
		;;
	esac
}

# Check for root, TUN, OS...
initialCheck

# Check if OpenVPN is already installed
if [[ -e /etc/openvpn/server.conf ]]; then
	manageMenu
else
	installOpenVPN
fi