#!/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
		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
		fi
	else
		echo "Looks like you aren't running this installer on a Debian 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 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 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) 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)
			exit 0
		;;
	esac
}

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

# Check if OpenVPN is already installed
if [[ -e /etc/openvpn/server.conf ]]; then
	manageMenu
else
	echo 'No configuration file detected!'
fi