#!/bin/bash

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


if [[ "$EUID" -ne 0 ]]; then
	echo "Sorry, you need to run this as root"
	exit 1
fi

if [[ ! -e /dev/net/tun ]]; then
	echo "TUN is not available"
	exit 2
fi

if grep -qs "CentOS release 5" "/etc/redhat-release"; then
	echo "CentOS 5 is too old and not supported"
	exit 3
fi

if [[ -e /etc/debian_version ]]; then
	OS="debian"
	# Getting the version number, to verify that a recent version of OpenVPN is available
	VERSION_ID=$(cat /etc/os-release | grep "VERSION_ID")
	RCLOCAL='/etc/rc.local'
	if [[ "$VERSION_ID" != 'VERSION_ID="7"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="8"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="12.04"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="14.04"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="16.04"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="16.10"' ]]; then
		echo "Your version of Debian/Ubuntu is not supported."
		echo "I can't install a recent version of OpenVPN on your system."
		echo ""
		echo "However, if you're using Debian unstable/testing, or Ubuntu beta,"
		echo "then you can continue, a recent version of OpenVPN is available on these."
		echo "Keep in mind they are not supported, though."
		while [[ $CONTINUE != "y" && $CONTINUE != "n" ]]; do
			read -p "Continue ? [y/n]: " -e CONTINUE
		done
		if [[ "$CONTINUE" = "n" ]]; then
			echo "Ok, bye !"
			exit 4
		fi
	fi
elif [[ -e /etc/centos-release || -e /etc/redhat-release ]]; then
	OS=centos
	RCLOCAL='/etc/rc.d/rc.local'
	# Needed for CentOS 7
	chmod +x /etc/rc.d/rc.local
else
	echo "Looks like you aren't running this installer on a Debian, Ubuntu or CentOS system"
	exit 4
fi

newclient () {
	# Generates the custom client.ovpn
	cp /etc/openvpn/client-common.txt ~/$1.ovpn
	echo "<ca>" >> ~/$1.ovpn
	cat /etc/openvpn/easy-rsa/pki/ca.crt >> ~/$1.ovpn
	echo "</ca>" >> ~/$1.ovpn
	echo "<cert>" >> ~/$1.ovpn
	cat /etc/openvpn/easy-rsa/pki/issued/$1.crt >> ~/$1.ovpn
	echo "</cert>" >> ~/$1.ovpn
	echo "<key>" >> ~/$1.ovpn
	cat /etc/openvpn/easy-rsa/pki/private/$1.key >> ~/$1.ovpn
	echo "</key>" >> ~/$1.ovpn
	echo "key-direction 1" >> ~/$1.ovpn
	echo "<tls-auth>" >> ~/$1.ovpn
	cat /etc/openvpn/tls-auth.key >> ~/$1.ovpn
	echo "</tls-auth>" >> ~/$1.ovpn
}

# Try to get our IP from the system and fallback to the Internet.
# I do this to make the script compatible with NATed servers (LowEndSpirit/Scaleway)
# and to avoid getting an IPv6.
IP=$(ip addr | grep 'inet' | grep -v inet6 | grep -vE '127\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | grep -o -E '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | head -1)
if [[ "$IP" = "" ]]; then
	IP=$(wget -qO- ipv4.icanhazip.com)
fi

if [[ -e /etc/openvpn/server.conf ]]; then
	while :
	do
	clear
		echo "Looks like OpenVPN is already installed"
		echo ""
		echo "What do you want to do?"
		echo "   1) Add a cert for a new user"
		echo "   2) Revoke existing user cert"
		echo "   3) Remove OpenVPN"
		echo "   4) Exit"
		read -p "Select an option [1-4]: " option
		case $option in
			1)
			echo ""
			echo "Tell me a name for the client cert"
			echo "Please, use one word only, no special characters"
			read -p "Client name: " -e -i client CLIENT
			cd /etc/openvpn/easy-rsa/
			./easyrsa build-client-full $CLIENT nopass
			# Generates the custom client.ovpn
			newclient "$CLIENT"
			echo ""
			echo "Client $CLIENT added, certs available at ~/$CLIENT.ovpn"
			exit
			;;
			2)
			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 5
			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 [[ "$NUMBEROFCLIENTS" = '1' ]]; then
				read -p "Select one client [1]: " CLIENTNUMBER
			else
				read -p "Select one client [1-$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 $CLIENT
			./easyrsa gen-crl
			rm -rf pki/reqs/$CLIENT.req
			rm -rf pki/private/$CLIENT.key
			rm -rf pki/issued/$CLIENT.crt
			rm -rf /etc/openvpn/crl.pem
			cp /etc/openvpn/easy-rsa/pki/crl.pem /etc/openvpn/crl.pem
			echo ""
			echo "Certificate for client $CLIENT revoked"
			echo "Exiting..."
			exit
			;;
			3)
			echo ""
			read -p "Do you really want to remove OpenVPN? [y/n]: " -e -i n REMOVE
			if [[ "$REMOVE" = 'y' ]]; then
				PORT=$(grep '^port ' /etc/openvpn/server.conf | cut -d " " -f 2)
				if pgrep firewalld; then
					# Using both permanent and not permanent rules to avoid a firewalld reload.
					firewall-cmd --zone=public --remove-port=$PORT/udp
					firewall-cmd --zone=trusted --remove-source=10.8.0.0/24
					firewall-cmd --permanent --zone=public --remove-port=$PORT/udp
					firewall-cmd --permanent --zone=trusted --remove-source=10.8.0.0/24
				fi
				if iptables -L -n | grep -qE 'REJECT|DROP'; then
					sed -i "/iptables -I INPUT -p udp --dport $PORT -j ACCEPT/d" $RCLOCAL
					sed -i "/iptables -I FORWARD -s 10.8.0.0\/24 -j ACCEPT/d" $RCLOCAL
					sed -i "/iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT/d" $RCLOCAL
				fi
				sed -i '/iptables -t nat -A POSTROUTING -s 10.8.0.0\/24 -j SNAT --to /d' $RCLOCAL
				if hash sestatus 2>/dev/null; then
					if sestatus | grep "Current mode" | grep -qs "enforcing"; then
						if [[ "$PORT" != '1194' ]]; then
							semanage port -d -t openvpn_port_t -p udp $PORT
						fi
					fi
				fi
				if [[ "$OS" = 'debian' ]]; then
					apt-get remove --purge -y openvpn openvpn-blacklist
				else
					yum remove openvpn -y
				fi
				rm -rf /etc/openvpn
				rm -rf /usr/share/doc/openvpn*
				echo ""
				echo "OpenVPN removed!"
			else
				echo ""
				echo "Removal aborted!"
			fi
			exit
			;;
			4) exit;;
		esac
	done
else
	clear
	echo 'Welcome to the secure OpenVPN installer'
	echo ""
	# OpenVPN setup and first user creation
	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 "First, choose which variant of the script you want to use."
	echo '"Fast" is secure, but "slow" provides you the best encryption you can get,'
	echo "at the cost of some speed (not that slow though)"
	echo "   1) Fast (2048 bits RSA and DH, 128 bits AES)"
	echo "   2) Slow (4096 bits RSA and DH, 256 bits AES)"
	while [[ $VARIANT !=  "1" && $VARIANT != "2" ]]; do
		read -p "Variant [1-2]: " -e -i 1 VARIANT
	done
	echo ""
	echo "I need to know the IPv4 address of the network interface you want OpenVPN listening to."
	echo "If you server is running behind a NAT, (e.g. LowEndSpirit, Scaleway) leave the IP adress as it is. (local/private IP)"
	echo "Otherwise, it sould be your public IPv4 address."
	read -p "IP address: " -e -i $IP IP
	echo ""
	echo "What port do you want for OpenVPN?"
	read -p "Port: " -e -i 1194 PORT
	echo ""
	echo "What protocol do you want for OpenVPN?"
	echo "Unless UDP is blocked, you should not use TCP (unnecessarily slower)"
	while [[ $PROTOCOL != "UDP" && $PROTOCOL != "TCP" ]]; do
		read -p "Protocol [UDP/TCP]: " -e -i UDP PROTOCOL
	done
	echo ""
	echo "What DNS do you want to use with the VPN?"
	echo "   1) Current system resolvers (/etc/resolv.conf)"
	echo "   2) FDN (France)"
	echo "   3) DNS.WATCH (Germany)"
	echo "   4) OpenDNS (Anycast: worldwide)"
	echo "   5) Google (Anycast: worldwide)"
	read -p "DNS [1-6]: " -e -i 2 DNS
	echo ""
	echo "Finally, tell me a name for the client certificate and configuration"
	while [[ $CLIENT = "" ]]; do
		echo "Please, use one word only, no special characters"
		read -p "Client name: " -e -i client CLIENT
	done
	echo ""
	echo "Okay, that was all I needed. We are ready to setup your OpenVPN server now"
	read -n1 -r -p "Press any key to continue..."
	if [[ "$OS" = 'debian' ]]; then
		apt-get install ca-certificates -y
		# We add the OpenVPN repo to get the latest version.
		# Debian 7
		if [[ "$VERSION_ID" = 'VERSION_ID="7"' ]]; then
			echo "deb http://swupdate.openvpn.net/apt wheezy main" > /etc/apt/sources.list.d/swupdate-openvpn.list
			wget -O - https://swupdate.openvpn.net/repos/repo-public.gpg | apt-key add -
			apt-get update
		fi
		# Debian 8
		if [[ "$VERSION_ID" = 'VERSION_ID="8"' ]]; then
			echo "deb http://swupdate.openvpn.net/apt jessie main" > /etc/apt/sources.list.d/swupdate-openvpn.list
			wget -O - https://swupdate.openvpn.net/repos/repo-public.gpg | apt-key add -
			apt update
		fi
		# Ubuntu 12.04
		if [[ "$VERSION_ID" = 'VERSION_ID="12.04"' ]]; then
			echo "deb http://swupdate.openvpn.net/apt precise main" > /etc/apt/sources.list.d/swupdate-openvpn.list
			wget -O - https://swupdate.openvpn.net/repos/repo-public.gpg | apt-key add -
			apt-get update
		fi
		# Ubuntu 14.04
		if [[ "$VERSION_ID" = 'VERSION_ID="14.04"' ]]; then
			echo "deb http://swupdate.openvpn.net/apt trusty main" > /etc/apt/sources.list.d/swupdate-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.
		# The we install OpenVPN
		apt-get install openvpn iptables openssl wget ca-certificates curl -y
	else
		# Else, the distro is CentOS
		yum install epel-release -y
		yum 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
	# Get easy-rsa
	wget -O ~/EasyRSA-3.0.1.tgz https://github.com/OpenVPN/easy-rsa/releases/download/3.0.1/EasyRSA-3.0.1.tgz
	tar xzf ~/EasyRSA-3.0.1.tgz -C ~/
	mv ~/EasyRSA-3.0.1/ /etc/openvpn/
	mv /etc/openvpn/EasyRSA-3.0.1/ /etc/openvpn/easy-rsa/
	chown -R root:root /etc/openvpn/easy-rsa/
	rm -rf ~/EasyRSA-3.0.1.tgz
	cd /etc/openvpn/easy-rsa/
	# If the user selected the fast, less hardened version
	if [[ "$VARIANT" = '1' ]]; then
		echo "set_var EASYRSA_KEY_SIZE 2048
set_var EASYRSA_DIGEST "sha256"" > vars
	fi
	# If the user selected the relatively slow, ultra hardened version
	if [[ "$VARIANT" = '2' ]]; then
		echo "set_var EASYRSA_KEY_SIZE 4096
set_var EASYRSA_DIGEST "sha384"" > vars
	fi
	# Create the PKI, set up the CA, the DH params and the server + client certificates
	./easyrsa init-pki
	./easyrsa --batch build-ca nopass
	./easyrsa gen-dh
	./easyrsa build-server-full server nopass
	./easyrsa build-client-full $CLIENT nopass
	./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 pki/dh.pem pki/issued/server.crt pki/private/server.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 $PORT" > /etc/openvpn/server.conf
	if [[ "$PROTOCOL" = 'UDP' ]]; then
		echo "proto udp" >> /etc/openvpn/server.conf
	elif [[ "$PROTOCOL" = 'TCP' ]]; then
		echo "proto tcp" >> /etc/openvpn/server.conf
	fi
	echo "dev tun
ca ca.crt
cert server.crt
key server.key
dh dh.pem
user nobody
group $NOGROUP
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
cipher AES-256-CBC
auth SHA512
tls-version-min 1.2" >> /etc/openvpn/server.conf
	if [[ "$VARIANT" = '1' ]]; then
		# If the user selected the fast, less hardened version
		echo "tls-cipher TLS-DHE-RSA-WITH-AES-128-GCM-SHA256" >> /etc/openvpn/server.conf
	elif [[ "$VARIANT" = '2' ]]; then
		# If the user selected the relatively slow, hardened version
		echo "tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384" >> /etc/openvpn/server.conf
	fi
	echo 'push "redirect-gateway def1 bypass-dhcp"' >> /etc/openvpn/server.conf
	# DNS resolvers
	case $DNS in
		1)
		# Obtain the resolvers from resolv.conf and use them for OpenVPN
		grep -v '#' /etc/resolv.conf | grep 'nameserver' | grep -E -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | while read line; do
			echo "push \"dhcp-option DNS $line\"" >> /etc/openvpn/server.conf
		done
		;;
		2) #FDN
		echo 'push "dhcp-option DNS 80.67.169.12"' >> /etc/openvpn/server.conf
		echo 'push "dhcp-option DNS 80.67.169.40"' >> /etc/openvpn/server.conf
		;;
		3) #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
		;;
		4) #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
		;;
		5) #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
		;;
	esac
	echo "keepalive 10 120
persist-key
persist-tun
crl-verify crl.pem
tls-server
tls-auth tls-auth.key 0
status openvpn-status.log
verb 3" >> /etc/openvpn/server.conf
	# Enable net.ipv4.ip_forward for the system
	sed -i '/\<net.ipv4.ip_forward\>/c\net.ipv4.ip_forward=1' /etc/sysctl.conf
	if ! grep -q "\<net.ipv4.ip_forward\>" /etc/sysctl.conf; then
		echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf
	fi
	# Avoid an unneeded reboot
	echo 1 > /proc/sys/net/ipv4/ip_forward
	# Set NAT for the VPN subnet
	iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -j SNAT --to $IP
	sed -i "1 a\iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -j SNAT --to $IP" $RCLOCAL
	if pgrep firewalld; then
		# We don't use --add-service=openvpn because that would only work with
		# the default port. Using both permanent and not permanent rules to
		# avoid a firewalld reload.
		if [[ "$PROTOCOL" = 'UDP' ]]; then
			firewall-cmd --zone=public --add-port=$PORT/udp
			firewall-cmd --permanent --zone=public --add-port=$PORT/udp
		elif [[ "$PROTOCOL" = 'TCP' ]]; then
			firewall-cmd --zone=public --add-port=$PORT/tcp
			firewall-cmd --permanent --zone=public --add-port=$PORT/tcp
		fi
		firewall-cmd --zone=trusted --add-source=10.8.0.0/24
		firewall-cmd --permanent --zone=trusted --add-source=10.8.0.0/24
	fi
	if iptables -L -n | grep -qE 'REJECT|DROP'; then
		# If iptables has at least one REJECT rule, we asume this is needed.
		# Not the best approach but I can't think of other and this shouldn't
		# cause problems.
		if [[ "$PROTOCOL" = 'UDP' ]]; then
			iptables -I INPUT -p udp --dport $PORT -j ACCEPT
		elif [[ "$PROTOCOL" = 'TCP' ]]; then
			iptables -I INPUT -p tcp --dport $PORT -j ACCEPT
		fi
		iptables -I FORWARD -s 10.8.0.0/24 -j ACCEPT
		iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
		if [[ "$PROTOCOL" = 'UDP' ]]; then
			sed -i "1 a\iptables -I INPUT -p udp --dport $PORT -j ACCEPT" $RCLOCAL
		elif [[ "$PROTOCOL" = 'TCP' ]]; then
			sed -i "1 a\iptables -I INPUT -p tcp --dport $PORT -j ACCEPT" $RCLOCAL
		fi
		sed -i "1 a\iptables -I FORWARD -s 10.8.0.0/24 -j ACCEPT" $RCLOCAL
		sed -i "1 a\iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" $RCLOCAL
	fi
	# If SELinux is enabled and a custom port was selected, we need this
	if hash sestatus 2>/dev/null; then
		if sestatus | grep "Current mode" | grep -qs "enforcing"; then
			if [[ "$PORT" != '1194' ]]; then
				# semanage isn't available in CentOS 6 by default
				if ! hash semanage 2>/dev/null; then
					yum install policycoreutils-python -y
				fi
				if [[ "$PROTOCOL" = 'UDP' ]]; then
					semanage port -a -t openvpn_port_t -p udp $PORT
				elif [[ "$PROTOCOL" = 'TCP' ]]; then
					semanage port -a -t openvpn_port_t -p tcp $PORT
				fi
			fi
		fi
	fi
	# And finally, restart OpenVPN
	if [[ "$OS" = 'debian' ]]; then
		# Little hack to check for systemd
		if pgrep systemd-journal; then
			systemctl restart openvpn@server.service
		else
			/etc/init.d/openvpn restart
		fi
	else
		if pgrep systemd-journal; then
			systemctl restart openvpn@server.service
			systemctl enable openvpn@server.service
		else
			service openvpn restart
			chkconfig openvpn on
		fi
	fi
	# Try to detect a NATed connection and ask about it to potential LowEndSpirit/Scaleway users
	EXTERNALIP=$(wget -qO- ipv4.icanhazip.com)
	if [[ "$IP" != "$EXTERNALIP" ]]; then
		echo ""
		echo "Looks like your server is behind a NAT!"
		echo ""
                echo "If your server is NATed (e.g. LowEndSpirit, Scaleway, or behind a router),"
                echo "then I need to know the address that can be used to access it from outside."
                echo "If that's not the case, just ignore this and leave the next field blank"
                read -p "External IP or domain name: " -e USEREXTERNALIP
		if [[ "$USEREXTERNALIP" != "" ]]; then
			IP=$USEREXTERNALIP
		fi
	fi
	# client-common.txt is created so we have a template to add further users later
	echo "client" > /etc/openvpn/client-common.txt
	if [[ "$PROTOCOL" = 'UDP' ]]; then
		echo "proto udp" >> /etc/openvpn/client-common.txt
	elif [[ "$PROTOCOL" = 'TCP' ]]; then
		echo "proto tcp-client" >> /etc/openvpn/client-common.txt
	fi
	echo "remote $IP $PORT
dev tun
resolv-retry infinite
nobind
persist-key
persist-tun
setenv opt block-outside-dns
verb 3
remote-cert-tls server
cipher AES-256-CBC
auth SHA512
tls-version-min 1.2
tls-client" >> /etc/openvpn/client-common.txt
	if [[ "$VARIANT" = '1' ]]; then
		# If the user selected the fast, less hardened version
		echo "tls-cipher TLS-DHE-RSA-WITH-AES-128-GCM-SHA256" >> /etc/openvpn/client-common.txt
	elif [[ "$VARIANT" = '2' ]]; then
		# If the user selected the relatively slow, hardened version
		echo "tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384" >> /etc/openvpn/client-common.txt
	fi
	# Generate the custom client.ovpn
	newclient "$CLIENT"
	echo ""
	echo "Finished!"
	echo ""
	echo "Your client config is available at ~/$CLIENT.ovpn"
	echo "If you want to add more clients, you simply need to run this script another time!"
fi
exit 0;