openvpn-install.sh

#!/bin/bash

# Secure OpenVPN server installer for Debian, Ubuntu, CentOS, Fedora and Arch Linux
# 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"
		source /etc/os-release

		if [[ "$ID" == "debian" ]]; then
			if [[ ! $VERSION_ID =~ (8|9) ]]; then
				echo "⚠️ Your version of Debian is not supported."
				echo ""
				echo "However, if you're using Debian >= 9 or unstable/testing then you can continue."
				echo "Keep in mind they are not supported, though."
				echo ""
				until [[ $CONTINUE =~ (y|n) ]]; do
					read -rp "Continue? [y/n]: " -e CONTINUE
				done
				if [[ "$CONTINUE" = "n" ]]; then
					exit 1
				fi
			fi
		elif [[ "$ID" == "ubuntu" ]];then
			OS="ubuntu"
			if [[ ! $VERSION_ID =~ (16.04|18.04) ]]; then
				echo "⚠️ Your version of Ubuntu is not supported."
				echo ""
				echo "However, if you're using Ubuntu > 17 or beta, then you can continue."
				echo "Keep in mind they are not supported, though."
				echo ""
				until [[ $CONTINUE =~ (y|n) ]]; do
					read -rp "Continue? [y/n]: " -e CONTINUE
				done
				if [[ "$CONTINUE" = "n" ]]; then
					exit 1
				fi
			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
			until [[ $CONTINUE =~ (y|n) ]]; do
				read -rp "Continue anyway? [y/n]: " -e CONTINUE
			done
			if [[ "$CONTINUE" = "n" ]]; then
				echo "Ok, bye!"
				exit 1
			fi
		fi
		OS=centos
	elif [[ -e /etc/arch-release ]]; then
		OS=arch
	else
		echo "Looks like you aren't running this installer on a Debian, Ubuntu, Fedora, CentOS or Arch Linux 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|ubuntu) ]]; 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

		elif [[ "$OS" = "arch" ]]; then
			pacman -Syu --noconfirm unbound

			# Get root servers list
			curl -o /etc/unbound/root.hints https://www.internic.net/domain/named.cache

			mv /etc/unbound/unbound.conf /etc/unbound/unbound.conf.old
			
			echo 'server:
	use-syslog: yes
	do-daemonize: no
	username: "unbound"
	directory: "/etc/unbound"
	trust-anchor-file: trusted-key.key
	root-hints: root.hints
	interface: 10.8.0.1
	access-control: 10.8.0.1/24 allow
	port: 53
	num-threads: 2
	use-caps-for-id: yes
	harden-glue: yes
	hide-identity: yes
	hide-version: yes
	qname-minimisation: yes
	prefetch: 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 installQuestions () {
	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 or hostname?"
		echo "We need it for the clients to connect to the server."
		until [[ "$PUBLICIP" != "" ]]; do
			read -rp "Public IPv4 address or hostname: " -e PUBLICIP
		done
	fi

	echo ""
	echo "Checking for IPv6 connectivity..."
	echo ""
	# "ping6" and "ping -6" availability varies depending on the distribution
	if type ping6 > /dev/null 2>&1; then
		PING6="ping6 -c3 ipv6.google.com > /dev/null 2>&1"
	else
		PING6="ping -6 -c3 ipv6.google.com > /dev/null 2>&1"
	fi
	if eval "$PING6"; 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.
	until [[ $IPV6_SUPPORT =~ (y|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: $PORT"
		;;
	esac
	echo ""
	echo "What protocol do you want OpenVPN to use?"
	echo "UDP is faster. Unless it is not available, you shouldn't use TCP."
	echo "   1) UDP"
	echo "   2) TCP"
	until [[ "$PROTOCOL_CHOICE" =~ ^[1-2]$ ]]; do
		read -rp "Protocol [1-2]: " -e -i 1 PROTOCOL_CHOICE
	done
	case $PROTOCOL_CHOICE in
		1)
			PROTOCOL="udp"
		;;
		2)
			PROTOCOL="tcp"
		;;
	esac
	echo ""
	echo "What DNS resolvers do you want to use with the VPN?"
	echo "   1) Current system resolvers (from /etc/resolv.conf)"
	echo "   2) Self-hosted DNS Resolver (Unbound)"
	echo "   3) Cloudflare (Anycast: worldwide)"
	echo "   4) Quad9 (Anycast: worldwide)"
	echo "   5) Quad9 uncensored (Anycast: worldwide)"
	echo "   6) FDN (France)"
	echo "   7) DNS.WATCH (Germany)"
	echo "   8) OpenDNS (Anycast: worldwide)"
	echo "   9) Google (Anycast: worldwide)"
	echo "   10) Yandex Basic (Russia)"
	echo "   11) AdGuard DNS (Russia)"
	until [[ "$DNS" =~ ^[0-9]+$ ]] && [ "$DNS" -ge 1 ] && [ "$DNS" -le 11 ]; 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 ""

				until [[ $CONTINUE =~ (y|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 use compression? It is not recommended since the VORACLE attack make use of it."
	until [[ $COMPRESSION_ENABLED =~ (y|n) ]]; do
		read -rp"Enable compression? [y/n]: " -e -i n COMPRESSION_ENABLED
	done
	if [[ $COMPRESSION_ENABLED == "y" ]];then
		echo "Choose which compression algorithm you want to use:"
		echo "   1) LZ4 (more efficient)"
		echo "   2) LZ0"
		until [[ $COMPRESSION_CHOICE =~ ^[1-2]$ ]]; do
			read -rp"Compression algorithm [1-2]: " -e -i 1 COMPRESSION_CHOICE
		done
		case $COMPRESSION_CHOICE in
			1)
			COMPRESSION_ALG="lz4"
			;;
			2)
			COMPRESSION_ALG="lzo"
			;;
		esac
	fi
	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#security-and-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 [[ $CUSTOMIZE_ENC == "n" ]];then
		# Use default, sane and fast parameters
		CIPHER="AES-128-GCM"
		CERT_TYPE="1" # ECDSA
		CERT_CURVE="prime256v1"
		CC_CIPHER="TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256"
		DH_TYPE="1" # ECDH
		DH_CURVE="prime256v1"
		HMAC_ALG="SHA256"
		TLS_SIG="1" # tls-crypt
	else
		echo ""
		echo "Choose which cipher you want to use for the data channel:"
		echo "   1) AES-128-GCM (recommended)"
		echo "   2) AES-192-GCM"
		echo "   3) AES-256-GCM"
		echo "   4) AES-128-CBC"
		echo "   5) AES-192-CBC"
		echo "   6) AES-256-CBC"
		until [[ "$CIPHER_CHOICE" =~ ^[1-6]$ ]]; do
			read -rp "Cipher [1-6]: " -e -i 1 CIPHER_CHOICE
		done
		case $CIPHER_CHOICE in
			1)
				CIPHER="AES-128-GCM"
			;;
			2)
				CIPHER="AES-192-GCM"
			;;
			3)
				CIPHER="AES-256-GCM"
			;;
			4)
				CIPHER="AES-128-CBC"
			;;
			5)
				CIPHER="AES-192-CBC"
			;;
			6)
				CIPHER="AES-256-CBC"
			;;
		esac
		echo ""
		echo "Choose what kind of certificate you want to use:"
		echo "   1) ECDSA (recommended)"
		echo "   2) RSA"
		until [[ $CERT_TYPE =~ ^[1-2]$ ]]; do
			read -rp"Certificate key type [1-2]: " -e -i 1 CERT_TYPE
		done
		case $CERT_TYPE in
			1)
				echo ""
				echo "Choose which curve you want to use for the certificate's key:"
				echo "   1) prime256v1 (recommended)"
				echo "   2) secp384r1"
				echo "   3) secp521r1"
				until [[ $CERT_CURVE_CHOICE =~ ^[1-3]$ ]]; do
					read -rp"Curve [1-3]: " -e -i 1 CERT_CURVE_CHOICE
				done
				case $CERT_CURVE_CHOICE in
					1)
						CERT_CURVE="prime256v1"
					;;
					2)
						CERT_CURVE="secp384r1"
					;;
					3)
						CERT_CURVE="secp521r1"
					;;
				esac
			;;
			2)
				echo ""
				echo "Choose which size you want to use for the certificate's RSA key:"
				echo "   1) 2048 bits (recommended)"
				echo "   2) 3072 bits"
				echo "   3) 4096 bits"
				until [[ "$RSA_KEY_SIZE_CHOICE" =~ ^[1-3]$ ]]; do
					read -rp "RSA key size [1-3]: " -e -i 1 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
			;;
		esac
		echo ""
		echo "Choose which cipher you want to use for the control channel:"
		case $CERT_TYPE in
			1)
				echo "   1) ECDHE-ECDSA-AES-128-GCM-SHA256 (recommended)"
				echo "   2) ECDHE-ECDSA-AES-256-GCM-SHA384"
				until [[ $CC_CIPHER_CHOICE =~ ^[1-2]$ ]]; do
					read -rp"Control channel cipher [1-2]: " -e -i 1 CC_CIPHER_CHOICE
				done
				case $CC_CIPHER_CHOICE in
					1)
						CC_CIPHER="TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256"
					;;
					2)
						CC_CIPHER="TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384"
					;;
				esac
			;;
			2)
				echo "   1) ECDHE-RSA-AES-128-GCM-SHA256 (recommended)"
				echo "   2) ECDHE-RSA-AES-256-GCM-SHA384"
				until [[ $CC_CIPHER_CHOICE =~ ^[1-2]$ ]]; do
					read -rp"Control channel cipher [1-2]: " -e -i 1 CC_CIPHER_CHOICE
				done
				case $CC_CIPHER_CHOICE in
					1)
						CC_CIPHER="TLS-ECDHE-RSA-WITH-AES-128-GCM-SHA256"
					;;
					2)
						CC_CIPHER="TLS-ECDHE-RSA-WITH-AES-256-GCM-SHA384"
					;;
				esac
			;;
		esac
		echo ""
		echo "Choose what kind of Diffie-Hellman key you want to use:"
		echo "   1) ECDH (recommended)"
		echo "   2) DH"
		until [[ $DH_TYPE =~ [1-2] ]]; do
			read -rp"DH key type [1-2]: " -e -i 1 DH_TYPE
		done
		case $DH_TYPE in
			1)
				echo ""
				echo "Choose which curve you want to use for the ECDH key:"
				echo "   1) prime256v1 (recommended)"
				echo "   2) secp384r1"
				echo "   3) secp521r1"
				while [[ $DH_CURVE_CHOICE != "1" && $DH_CURVE_CHOICE != "2" && $DH_CURVE_CHOICE != "3" ]]; do
					read -rp"Curve [1-3]: " -e -i 1 DH_CURVE_CHOICE
				done
				case $DH_CURVE_CHOICE in
					1)
						DH_CURVE="prime256v1"
					;;
					2)
						DH_CURVE="secp384r1"
					;;
					3)
						DH_CURVE="secp521r1"
					;;
				esac
			;;
			2)
				echo ""
				echo "Choose what size of Diffie-Hellman key you want to use:"
				echo "   1) 2048 bits (recommended)"
				echo "   2) 3072 bits"
				echo "   3) 4096 bits"
				until [[ "$DH_KEY_SIZE_CHOICE" =~ ^[1-3]$ ]]; do
					read -rp "DH key size [1-3]: " -e -i 1 DH_KEY_SIZE_CHOICE
				done
				case $DH_KEY_SIZE_CHOICE in
					1)
						DH_KEY_SIZE="2048"
					;;
					2)
						DH_KEY_SIZE="3072"
					;;
					3)
						DH_KEY_SIZE="4096"
					;;
				esac
			;;
		esac
		echo ""
		# The "auth" options behaves differently with AEAD ciphers
		if [[ "$CIPHER" =~ CBC$ ]]; then
			echo "The digest algorithm authenticates data channel packets and tls-auth packets from the control channel."
		elif [[ "$CIPHER" =~ GCM$ ]]; then
			echo "The digest algorithm authenticates tls-auth packets from the control channel."
		fi
		echo "Which digest algorithm do you want to use for HMAC?"
		echo "   1) SHA-256 (recommended)"
		echo "   2) SHA-384"
		echo "   3) SHA-512"
		until [[ $HMAC_ALG_CHOICE =~ ^[1-3]$ ]]; do
			read -rp "Digest algorithm [1-3]: " -e -i 1 HMAC_ALG_CHOICE
		done
		case $HMAC_ALG_CHOICE in
			1)
				HMAC_ALG="SHA256"
			;;
			2)
				HMAC_ALG="SHA384"
			;;
			3)
				HMAC_ALG="SHA512"
			;;
		esac
		echo ""
		echo "You can add an additional layer of security to the control channel with tls-auth and tls-crypt"
		echo "tls-auth authenticates the packets, while tls-crypt authenticate and encrypt them."
		echo "   1) tls-crypt (recommended)"
		echo "   2) tls-auth"
		until [[ $TLS_SIG =~ [1-2] ]]; do
				read -rp "Control channel additional security mechanism [1-2]: " -e -i 1 TLS_SIG
		done
	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 installation."
	read -n1 -r -p "Press any key to continue..."
}

function installOpenVPN () {
	# Run setup questions first
	installQuestions

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

	if [[ "$OS" =~ (debian|ubuntu) ]]; then
		apt-get update
		apt-get -y install ca-certificates gnupg
		# We add the OpenVPN repo to get the latest version.
		if [[ "$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
		if [[ "$VERSION_ID" = "16.04" ]]; then
			echo "deb http://build.openvpn.net/debian/openvpn/stable trusty main" > /etc/apt/sources.list.d/openvpn.list
			wget -O - https://swupdate.openvpn.net/repos/repo-public.gpg | apt-key add -
			apt-get update
		fi
		# Ubuntu > 16.04 and Debian > 8 have OpenVPN >= 2.4 without the need of a third party repository.
		apt-get install -y openvpn iptables openssl wget ca-certificates curl
	elif [[ "$OS" = 'centos' ]]; then
		yum install -y epel-release
		yum install -y openvpn iptables openssl wget ca-certificates curl
	elif [[ "$OS" = 'fedora' ]]; then
		dnf install -y openvpn iptables openssl wget ca-certificates curl
	elif [[ "$OS" = 'arch' ]]; then
		echo ""
		echo "WARNING: As you're using ArchLinux, I need to update the packages on your system to install those I need."
		echo "Not doing that could cause problems between dependencies, or missing files in repositories (Arch Linux does not support partial upgrades)."
		echo ""
		echo "Continuing will update your installed packages and install needed ones."
		echo ""
		unset CONTINUE
		until [[ $CONTINUE =~ (y|n) ]]; do
			read -rp "Continue? [y/n]: " -e -i y CONTINUE
		done
		if [[ "$CONTINUE" = "n" ]]; then
			echo "Exiting because user did not permit updating the system."
			exit 4
		fi

		# Install required dependencies and upgrade the system
		pacman --needed --noconfirm -Syu openvpn iptables openssl wget ca-certificates curl
	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="3.0.5"
	wget -O ~/EasyRSA-nix-${version}.tgz https://github.com/OpenVPN/easy-rsa/releases/download/v${version}/EasyRSA-nix-${version}.tgz
	tar xzf ~/EasyRSA-nix-${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-nix-${version}.tgz

	cd /etc/openvpn/easy-rsa/
	case $CERT_TYPE in
		1)
			echo "set_var EASYRSA_ALGO ec" > vars
			echo "set_var EASYRSA_CURVE $CERT_CURVE" >> vars
		;;
		2)
			echo "set_var EASYRSA_KEY_SIZE $RSA_KEY_SIZE" > vars
		;;
	esac

	# 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_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

	if [[ $DH_TYPE == "2" ]]; then
		# ECDH keys are generated on-the-fly so we don't need to generate them beforehand
		openssl dhparam -out dh.pem $DH_KEY_SIZE
	fi
	
	./easyrsa build-server-full "$SERVER_NAME" nopass
	EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
	
	case $TLS_SIG in
		1)
			# Generate tls-crypt key
			openvpn --genkey --secret /etc/openvpn/tls-crypt.key
		;;
		2)
			# Generate tls-auth key
			openvpn --genkey --secret /etc/openvpn/tls-auth.key
		;;
	esac
	
	# Move all the generated files
	cp pki/ca.crt pki/private/ca.key "pki/issued/$SERVER_NAME.crt" "pki/private/$SERVER_NAME.key" /etc/openvpn/easy-rsa/pki/crl.pem /etc/openvpn
	if [[ $DH_TYPE == "2" ]]; then
		cp dh.pem /etc/openvpn
	fi
	
	# 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) # Quad9 uncensored
			echo 'push "dhcp-option DNS 9.9.9.10"' >> /etc/openvpn/server.conf
			echo 'push "dhcp-option DNS 149.112.112.10"' >> /etc/openvpn/server.conf
		;;
		6) # 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
		;;
		7) # 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
		;;
		8) # 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
		;;
		9) # 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
		;;
		10) # 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
		;;
		11) # 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

	if [[ $COMPRESSION_ENABLED == "y"  ]]; then
		echo "compress $COMPRESSION_ALG" >> /etc/openvpn/server.conf
	fi

	if [[ $DH_TYPE == "1" ]]; then
		echo "dh none" >> /etc/openvpn/server.conf
		echo "ecdh-curve $DH_CURVE" >> /etc/openvpn/server.conf
	elif [[ $DH_TYPE == "2" ]]; then
		echo "dh dh.pem" >> /etc/openvpn/server.conf
	fi

	case $TLS_SIG in
		1)
			echo "tls-crypt tls-crypt.key 0" >> /etc/openvpn/server.conf
		;;
		2)
			echo "tls-auth tls-auth.key 0" >> /etc/openvpn/server.conf
		;;
	esac

	echo "crl-verify crl.pem
ca ca.crt
cert $SERVER_NAME.crt
key $SERVER_NAME.key 
auth $HMAC_ALG
cipher $CIPHER
ncp-ciphers $CIPHER
tls-server
tls-version-min 1.2
tls-cipher $CC_CIPHER
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 [[ "$OS" = 'arch' || "$OS" = 'fedora' ]]; then
		# Don't modify package-provided service
		cp /usr/lib/systemd/system/openvpn-server@.service /etc/systemd/system/openvpn-server@.service
		
		# Workaround to fix OpenVPN service on OpenVZ
		sed -i 's|LimitNPROC|#LimitNPROC|' /etc/systemd/system/openvpn-server@.service
		# Another workaround to keep using /etc/openvpn/
		sed -i 's|/etc/openvpn/server|/etc/openvpn|' /etc/systemd/system/openvpn-server@.service
		# On fedora, the service hardcodes the ciphers. We want to manage the cipher ourselves, so we remove it from the service
		if [[ "$OS" == "fedora" ]];then
			sed -i 's|--cipher AES-256-GCM --ncp-ciphers AES-256-GCM:AES-128-GCM:AES-256-CBC:AES-128-CBC:BF-CBC||' /etc/systemd/system/openvpn-server@.service
		fi

		systemctl daemon-reload
		systemctl restart openvpn-server@server
		systemctl enable openvpn-server@server
	elif [[ "$OS" == "ubuntu" ]] && [[ "$VERSION_ID" == "16.04" ]]; then
		# On Ubuntu 16.04, we use the package from the OpenVPN repo
		# This package uses a sysvinit service
		systemctl enable openvpn
		systemctl start openvpn
	else
		# Don't modify package-provided service
		cp /lib/systemd/system/openvpn\@.service /etc/systemd/system/openvpn\@.service
		
		# Workaround to fix OpenVPN service on OpenVZ
		sed -i 's|LimitNPROC|#LimitNPROC|' /etc/systemd/system/openvpn\@.service
		# Another workaround to keep using /etc/openvpn/
		sed -i 's|/etc/openvpn/server|/etc/openvpn|' /etc/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-online.target
Wants=network-online.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 $HMAC_ALG
auth-nocache
cipher $CIPHER
tls-client
tls-version-min 1.2
tls-cipher $CC_CIPHER
setenv opt block-outside-dns # Prevent Windows 10 DNS leak
verb 3" >> /etc/openvpn/client-template.txt

if [[ $COMPRESSION_ENABLED == "y"  ]]; then
	echo "compress $COMPRESSION_ALG" >> /etc/openvpn/client-template.txt
fi

	# 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

	# Determine if we use tls-auth or tls-crypt
	if grep -qs "^tls-crypt" /etc/openvpn/server.conf; then
		TLS_SIG="1"
	elif grep -qs "^tls-auth" /etc/openvpn/server.conf; then
		TLS_SIG="2"
	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>"
		awk '/BEGIN/,/END/' "/etc/openvpn/easy-rsa/pki/issued/$CLIENT.crt"
		echo "</cert>"

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

		case $TLS_SIG in
			1)
				echo "<tls-crypt>"
				cat /etc/openvpn/tls-crypt.key
				echo "</tls-crypt>"
			;;
			2)
				echo "key-direction 1"
				echo "<tls-auth>"
				cat /etc/openvpn/tls-auth.key
				echo "</tls-auth>"
			;;
		esac
	} >> "$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"
	sed -i "s|^$CLIENT,.*||" /etc/openvpn/ipp.txt

	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|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 [[ "$OS" =~ (debian|ubuntu) ]]; then
			apt-get autoremove --purge -y unbound
		elif [[ "$OS" = 'arch' ]]; then
			pacman --noconfirm -R unbound
		elif [[ "$OS" = 'centos' ]]; then
			yum remove -y unbound
		elif [[ "$OS" = 'fedora' ]]; then
			dnf remove -y unbound
		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 [[ "$OS" =~ (fedora|arch) ]]; then
			systemctl disable openvpn-server@server
			systemctl stop openvpn-server@server
			# Remove customised service
			rm /etc/systemd/system/openvpn-server@.service
		elif [[ "$OS" == "ubuntu" ]] && [[ "$VERSION_ID" == "16.04" ]]; then
			systemctl disable openvpn
			systemctl stop openvpn
		else
			systemctl disable openvpn@server
			systemctl stop openvpn@server
			# Remove customised service
			rm /etc/systemd/system/openvpn\@.service
		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 [[ "$OS" =~ (debian|ubuntu) ]]; then
			apt-get autoremove --purge -y openvpn
			if [[ -e /etc/apt/sources.list.d/openvpn.list ]];then
				rm /etc/apt/sources.list.d/openvpn.list
				apt-get update
			fi
		elif [[ "$OS" = 'arch' ]]; then
			pacman --noconfirm -R openvpn
		elif [[ "$OS" = 'centos' ]]; then
			yum remove -y openvpn
		elif [[ "$OS" = 'fedora' ]]; then
			dnf remove -y openvpn
		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
		rm -rf /var/log/openvpn

		# 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