#!/bin/bash

# Secure OpenVPN server installer for Debian, Ubuntu, CentOS and Arch Linux
# 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 OpenVPN 2.4 on your system."
		echo ""
		echo "However, if you're using Debian unstable/testing, or Ubuntu beta,"
		echo "then you can continue, this version of OpenVPN is available on these."
		echo "Keep in mind these releases 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
	# We put everything in the client file
	cp /etc/openvpn/client-template.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 "<tls-crypt>" >> ~/$1.ovpn
	cat /etc/openvpn/tls-crypt.key >> ~/$1.ovpn
	echo "</tls-crypt>" >> ~/$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 "OpenVPN-install (github.com/Angristan/OpenVPN-install)"
		echo ""
		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 (github.com/Angristan/OpenVPN-install)"
	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 "I need to know the IPv4 address of the network interface you want OpenVPN listening to."
	echo "If your server is running behind a NAT, (e.g. LowEndSpirit, Scaleway) leave the IP address as it is. (local/private IP)"
	echo "Otherwise, it should 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 (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)"
	while [[ $DNS != "1" && $DNS != "2" && $DNS != "3" && $DNS != "4" && $DNS != "5" ]]; do
		read -p "DNS [1-5]: " -e -i 2 DNS
	done
	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://build.openvpn.net/debian/openvpn/release/2.4 wheezy 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
		# Debian 8
		if [[ "$VERSION_ID" = 'VERSION_ID="8"' ]]; then
			echo "deb http://build.openvpn.net/debian/openvpn/release/2.4 jessie main" > /etc/apt/sources.list.d/openvpn.list
			wget -O - https://swupdate.openvpn.net/repos/repo-public.gpg | apt-key add -
			apt update
		fi
		# Ubuntu 12.04
		if [[ "$VERSION_ID" = 'VERSION_ID="12.04"' ]]; then
			echo "deb http://build.openvpn.net/debian/openvpn/release/2.4 precise 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 14.04
		if [[ "$VERSION_ID" = 'VERSION_ID="14.04"' ]]; then
			echo "deb http://build.openvpn.net/debian/openvpn/release/2.4 trusty main" > /etc/apt/sources.list.d/openvpn.list
			wget -O - https://swupdate.openvpn.net/repos/repo-public.gpg | apt-key add -
			apt-get update
		fi
		# Ubuntu 16.04
		if [[ "$VERSION_ID" = 'VERSION_ID="16.04"' ]]; then
			echo "deb http://build.openvpn.net/debian/openvpn/release/2.4 xenial 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
		# Then 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/
	echo 'set_var EASYRSA_ALGO ec
set_var EASYRSA_CURVE sect571r1
set_var EASYRSA_DIGEST "sha512"' > 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 build-server-full server nopass
	./easyrsa build-client-full $CLIENT nopass
	./easyrsa gen-crl
	# Generate tls-crypt key
	openvpn --genkey --secret /etc/openvpn/tls-crypt.key
	# Move all the generated files
	cp pki/ca.crt pki/private/ca.key 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
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)
		# 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 'push "redirect-gateway def1 bypass-dhcp" '>> /etc/openvpn/server.conf
echo "crl-verify crl.pem
ca ca.crt
cert server.crt
key server.key
tls-crypt tls-crypt.key 0
dh none
ecdh-curve sect571r1 
auth SHA512
cipher AES-256-GCM
tls-server
tls-version-min 1.2
tls-cipher TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384
status openvpn.log
verb 3" >> /etc/openvpn/server.conf

	# Create the sysctl configuration file if needed (mainly for Arch Linux)
	if [[ ! -e /etc/sysctl.conf ]]; then
		touch /etc/sysctl.conf
	fi

	# 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=$USEREXTERNALIP
		fi
	fi
	# client-template.txt is created so we have a template to add further users later
	echo "client" > /etc/openvpn/client-template.txt
	if [[ "$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
auth SHA512
cipher AES-256-GCM
tls-client
tls-version-min 1.2
tls-cipher TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384
setenv opt block-outside-dns
verb 3" >> /etc/openvpn/client-template.txt

	# 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;