#!/bin/bash
# OpenVPN road warrior installer for Debian, Ubuntu and CentOS

# This script will work on Debian, Ubuntu, CentOS and probably other distros
# of the same families, although no support is offered for them. It isn't
# bulletproof but it will probably work if you simply want to setup a VPN on
# your Debian/Ubuntu/CentOS box. It has been designed to be as unobtrusive and
# universal as possible.


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
	RCLOCAL='/etc/rc.local'
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
}


# 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)
			# This option could be documented a bit better and maybe even be simplimplified
			# ...but what can I say, I want some sleep too
			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 $CLIENT revoked"
			exit
			;;
			3) 
			echo ""
			read -p "Do you really want to remove OpenVPN? [y/n]: " -e -i n REMOVE
			if [[ "$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 | 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 this quick OpenVPN "road warrior" 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 "Read carefully the README on GitHub before choosing. Use legacy of you're not sure."
	echo "   1) Latest (High encryption, not compatible with all servers and clients)"
	echo "   2) Legacy (Work with most devices)"
	read -p "Variant [1-2]: " -e -i 2 VER
	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. (10.x.x.x)"
	echo "Otherwise, it sould be your public IPv4 address."
	read -p "IP address: " -e -i $IP IP
	echo ""
	echo "What port do you want for OpenVPN?"
	read -p "Port: " -e -i 1194 PORT
	echo ""
	echo "What DNS do you want to use with the VPN?"
	echo "   1) Current system resolvers"
	echo "   2) FDN (recommended)"
	echo "   3) OpenDNS"
	echo "   4) NTT"
	echo "   5) Google"
	echo "   6) Hurricane Electric"
	read -p "DNS [1-6]: " -e -i 2 DNS
	echo ""
	echo "Finally, tell me your name for the client cert"
	echo "Please, use one word only, no special characters"
	read -p "Client name: " -e -i client CLIENT
	echo ""
	echo "Okay, that was all I needed. We are ready to setup your OpenVPN server now"
	read -n1 -r -p "Press any key to continue..."
	if [[ "$OS" = 'debian' ]]; then
		apt-get update
		apt-get install openvpn iptables openssl ca-certificates -y
	else
		# Else, the distro is CentOS
		yum install epel-release -y
		yum install openvpn iptables openssl wget ca-certificates -y
	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/
	#Use 4096 bits DH instead of 2048 bits
	echo "set_var EASYRSA_KEY_SIZE 4096" > vars
	# 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
	# Move the stuff we need
	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
	# Generate server.conf
	echo "port $PORT
proto udp
dev tun
sndbuf 0
rcvbuf 0
ca ca.crt
cert server.crt
key server.key
dh dh.pem
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt" > /etc/openvpn/server.conf
	if [[ "$VER" = '1' ]]; then 
		#If we're using the latest variant
		echo "tls-cipher TLS-DHE-RSA-WITH-AES-128-GCM-SHA256
tls-version-min 1.2" >> /etc/openvpn/server.conf
	else
		# If the user slected legacy
		# Or if the user selected a non-existant variant, we fallback to legacy
		echo "cipher AES-256-CBC" >> /etc/openvpn/server.conf
	fi
	echo 'push "redirect-gateway def1 bypass-dhcp"' >> /etc/openvpn/server.conf
	# DNS
	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 $line\"" >> /etc/openvpn/server.conf
		done
		;;
		2) 
		echo 'push "dhcp-option DNS 80.67.169.12"' >> /etc/openvpn/server.conf
		echo 'push "dhcp-option DNS 80.67.169.40"' >> /etc/openvpn/server.conf
		;;
		3)
		echo 'push "dhcp-option DNS 208.67.222.222"' >> /etc/openvpn/server.conf
		echo 'push "dhcp-option DNS 208.67.220.220"' >> /etc/openvpn/server.conf
		;;
		4) 
		echo 'push "dhcp-option DNS 129.250.35.250"' >> /etc/openvpn/server.conf
		echo 'push "dhcp-option DNS 129.250.35.251"' >> /etc/openvpn/server.conf
		;;
		5)
		echo 'push "dhcp-option DNS 8.8.8.8"' >> /etc/openvpn/server.conf
		echo 'push "dhcp-option DNS 8.8.4.4"' >> /etc/openvpn/server.conf
		;;
		6) 
		echo 'push "dhcp-option DNS 74.82.42.42"' >> /etc/openvpn/server.conf
		;;
	esac
	echo "keepalive 10 120
comp-lzo
persist-key
persist-tun
crl-verify crl.pem" >> /etc/openvpn/server.conf
	# Enable net.ipv4.ip_forward for the system
	if [[ "$OS" = 'debian' ]]; then
		sed -i 's|#net.ipv4.ip_forward=1|net.ipv4.ip_forward=1|' /etc/sysctl.conf
	else
		# CentOS 5 and 6
		sed -i 's|net.ipv4.ip_forward = 0|net.ipv4.ip_forward = 1|' /etc/sysctl.conf
		# CentOS 7
		if ! grep -q "net.ipv4.ip_forward=1" "/etc/sysctl.conf"; then
			echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf
		fi
	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" $RCLOCAL
	if pgrep firewalld; then
		# We don't use --add-service=openvpn because that would only work with
		# the default port. Using both permanent and not permanent rules to
		# avoid a firewalld reload.
		firewall-cmd --zone=public --add-port=$PORT/udp
		firewall-cmd --zone=trusted --add-source=10.8.0.0/24
		firewall-cmd --permanent --zone=public --add-port=$PORT/udp
		firewall-cmd --permanent --zone=trusted --add-source=10.8.0.0/24
	fi
	if iptables -L | 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.
		iptables -I INPUT -p udp --dport $PORT -j ACCEPT
		iptables -I FORWARD -s 10.8.0.0/24 -j ACCEPT
		iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
		sed -i "1 a\iptables -I INPUT -p udp --dport $PORT -j ACCEPT" $RCLOCAL
		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
				semanage port -a -t openvpn_port_t -p udp $PORT
			fi
		fi
	fi
	# And finally, restart OpenVPN
	if [[ "$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" != "$EXTERNALIP" ]]; then
		echo ""
		echo "Looks like your server is behind a NAT!"
		echo ""
		echo "If your server is NATed (e.g. LowEndSpirit, Scaleway), I need to know the external IP"
		echo "If that's not the case, just ignore this and leave the next field blank"
		read -p "External IP: " -e USEREXTERNALIP
		if [[ "$USEREXTERNALIP" != "" ]]; then
			IP=$USEREXTERNALIP
		fi
	fi
	# client-common.txt is created so we have a template to add further users later
	echo "client
dev tun
proto udp
sndbuf 0
rcvbuf 0
remote $IP $PORT
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
comp-lzo" > /etc/openvpn/client-common.txt
	if [[ "$VER" = '1' ]]; then 
		#If we're using the latest variant
		echo "tls-cipher TLS-DHE-RSA-WITH-AES-128-GCM-SHA256
tls-version-min 1.2" >> /etc/openvpn/client-common.txt
	else
		# If the user slected legacy
		# Or if the user selected a non-existant variant, we fallback to legacy
		echo "cipher AES-256-CBC" >> /etc/openvpn/client-common.txt
	fi
	# Generates 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