#!/bin/bash
#
# https://github.com/Nyr/openvpn-install
#
# Copyright (c) 2013 Nyr. Released under the MIT License.


# Detect Debian users running the script with "sh" instead of bash
if readlink /proc/$$/exe | grep -q "dash"; then
	echo "This script needs to be run with bash, not sh"
	exit
fi

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

if [[ ! -e /dev/net/tun ]]; then
	echo "The TUN device is not available
You need to enable TUN before running this script"
	exit
fi

if [[ -e /etc/debian_version ]]; then
	OS=debian
	GROUPNAME=nogroup
	RCLOCAL='/etc/rc.local'
elif [[ -e /etc/centos-release || -e /etc/redhat-release ]]; then
	OS=centos
	GROUPNAME=nobody
	RCLOCAL='/etc/rc.d/rc.local'
else
	echo "Looks like you aren't running this installer on Debian, Ubuntu or CentOS"
	exit
fi

UDPNETWORK="10.8.0.0"
TCPNETWORK="10.9.0.0"

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 "<tls-auth>" >> ~/$1.ovpn
	cat /etc/openvpn/ta.key >> ~/$1.ovpn
	echo "</tls-auth>" >> ~/$1.ovpn
}

newserver() {
	local port=$1
	local protocol=$2
	local network=$3
	local dns=$4
	cat << EOF
port $port
proto $protocol
server $network 255.255.255.0
dev tun
sndbuf 0
rcvbuf 0
ca ca.crt
cert server.crt
key server.key
dh dh.pem
auth SHA512
tls-auth ta.key 0
topology subnet
ifconfig-pool-persist ipp.txt
keepalive 10 120
cipher AES-256-CBC
comp-lzo
user nobody
group $GROUPNAME
persist-key
persist-tun
crl-verify crl.pem
status openvpn-status-$protocol.log
verb 3
push "redirect-gateway def1 bypass-dhcp"
EOF
	for addr in $dns; do
		echo "push \"dhcp-option DNS $addr\""
	done
}

setfirewall() {
	local port=$1
	local protocol=$2
	local network=$3
	local ip=$4
	# Using both permanent and not permanent rules to avoid a firewalld reload.
	# We don't use --add-service=openvpn because that would only work with
	# the default port and protocol.
	firewall-cmd --zone=public --add-port=$port/$protocol
	firewall-cmd --zone=trusted --add-source=$network/24
	firewall-cmd --permanent --zone=public --add-port=$port/$protocol
	firewall-cmd --permanent --zone=trusted --add-source=$network/24
	# Set NAT for the VPN subnet
	firewall-cmd --direct --add-rule ipv4 nat POSTROUTING 0 -s $network/24 ! -d $network/24 -j SNAT --to $ip
	firewall-cmd --permanent --direct --add-rule ipv4 nat POSTROUTING 0 -s $network/24 ! -d $network/24 -j SNAT --to $ip
}

unsetfirewall() {
	local port=$1
	local protocol=$2
	local network=$3
	local ip=$(firewall-cmd --direct --get-rules ipv4 nat POSTROUTING | grep "\-s $network/24 '!' -d $network/24 -j SNAT --to " | cut -d " " -f 10)
	# Using both permanent and not permanent rules to avoid a firewalld reload.
	firewall-cmd --zone=public --remove-port=$port/$protocol
	firewall-cmd --zone=trusted --remove-source=$network/24
	firewall-cmd --permanent --zone=public --remove-port=$port/$protocol
	firewall-cmd --permanent --zone=trusted --remove-source=$network/24
	# Unset NAT for the VPN subnet
	firewall-cmd --direct --remove-rule ipv4 nat POSTROUTING 0 -s $network/24 ! -d $network/24 -j SNAT --to $ip
	firewall-cmd --permanent --direct --remove-rule ipv4 nat POSTROUTING 0 -s $network/24 ! -d $network/24 -j SNAT --to $ip
}

setiptables() {
	local port=$1
	local protocol=$2
	local network=$3
	local ip=$4
	# Needed to use rc.local with some systemd distros
	if [[ $OS = "debian" && ! -e $RCLOCAL ]]; then
		echo -e "#!/bin/sh -e\nexit 0" > $RCLOCAL
	fi
	chmod +x $RCLOCAL
	# Set NAT for the VPN subnet
	iptables -t nat -A POSTROUTING -s $network/24 ! -d $network/24 -j SNAT --to $ip
	sed -i "1 a\iptables -t nat -A POSTROUTING -s $network/24 ! -d $network/24 -j SNAT --to $ip" $RCLOCAL
	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.
		iptables -I INPUT -p $protocol --dport $port -j ACCEPT
		iptables -I FORWARD -s $network/24 -j ACCEPT
		iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
		sed -i "1 a\iptables -I INPUT -p $protocol --dport $port -j ACCEPT" $RCLOCAL
		sed -i "1 a\iptables -I FORWARD -s $network/24 -j ACCEPT" $RCLOCAL
		sed -i "1 a\iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" $RCLOCAL
	fi
}

unsetiptables() {
	local port=$1
	local protocol=$2
	local network=$3
	IP=$(grep "iptables -t nat -A POSTROUTING -s $network/24 ! -d $network/24 -j SNAT --to " $RCLOCAL | cut -d " " -f 14)
	iptables -t nat -D POSTROUTING -s $network/24 ! -d $network/24 -j SNAT --to $IP
	sed -i "/iptables -t nat -A POSTROUTING -s $network\/24 ! -d $network\/24 -j SNAT --to /d" $RCLOCAL
	if iptables -L -n | grep -qE '^ACCEPT'; then
		iptables -D INPUT -p $protocol --dport $port -j ACCEPT
		iptables -D FORWARD -s $network/24 -j ACCEPT
		iptables -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
		sed -i "/iptables -I INPUT -p $protocol --dport $port -j ACCEPT/d" $RCLOCAL
		sed -i "/iptables -I FORWARD -s $network\/24 -j ACCEPT/d" $RCLOCAL
		sed -i "/iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT/d" $RCLOCAL
	fi
}

if [[ -d /etc/openvpn ]]; then
	while :
	do
	clear
		echo "Looks like OpenVPN is already installed."
		echo
		echo "What do you want to do?"
		echo "   1) Add a new user"
		echo "   2) Revoke an existing user"
		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 certificate."
			echo "Please, use one word only, no special characters."
			read -p "Client name: " -e CLIENT
			cd /etc/openvpn/easy-rsa/
			./easyrsa build-client-full $CLIENT nopass
			# Generates the custom client.ovpn
			newclient "$CLIENT"
			echo
			echo "Client $CLIENT added, configuration is available at:" ~/"$CLIENT.ovpn"
			exit
			;;
			2)
			# This option could be documented a bit better and maybe even be simplified
			# ...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
			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)
			echo
			read -p "Do you really want to revoke access for client $CLIENT? [y/N]: " -e REVOKE
			if [[ "$REVOKE" = 'y' || "$REVOKE" = 'Y' ]]; then
				cd /etc/openvpn/easy-rsa/
				./easyrsa --batch revoke $CLIENT
				EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
				rm -f pki/reqs/$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
				# CRL is read with each client connection, when OpenVPN is dropped to nobody
				chown nobody:$GROUPNAME /etc/openvpn/crl.pem
				echo
				echo "Certificate for client $CLIENT revoked!"
			else
				echo
				echo "Certificate revocation for client $CLIENT aborted!"
			fi
			exit
			;;
			3)
			echo
			read -p "Do you really want to remove OpenVPN? [y/N]: " -e REMOVE
			if [[ "$REMOVE" = 'y' || "$REMOVE" = 'Y' ]]; then
				if [[ -f /etc/openvpn/server_udp.conf ]]; then
					UDPPORT=$(grep '^port ' /etc/openvpn/server_udp.conf | cut -d " " -f 2)
				fi
				if [[ -f /etc/openvpn/server_tcp.conf ]]; then
					TCPPORT=$(grep '^port ' /etc/openvpn/server_tcp.conf | cut -d " " -f 2)
				fi
				if pgrep firewalld; then
					CMD="unsetfirewall"
				else
					CMD="unsetiptables"
				fi
				if [[ -n $UDPPORT ]]; then
					$CMD $UDPPORT "udp" $UDPNETWORK
				fi
				if [[ -n $TCPPORT ]]; then
					$CMD $TCPPORT "tcp" $TCPNETWORK
				fi
				if pgrep systemd-journal; then
					if [[ -n $UDPPORT ]]; then
						systemctl disable openvpn@server_udp.service
					fi
					if [[ -n $TCPPORT ]]; then
						systemctl disable openvpn@server_tcp.service
					fi
				fi
				if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing"; then
					if [[ -n $UDPPORT && $UDPPORT != "1194" ]]; then
						semanage port -d -t openvpn_port_t -p udp $UDPPORT
					fi
					if [[ -n $TCPPORT && $TCPPORT != "1194" ]]; then
						semanage port -d -t openvpn_port_t -p tcp $TCPPORT
					fi
				fi
				if [[ "$OS" = 'debian' ]]; then
					apt-get remove --purge -y openvpn
				else
					yum remove openvpn -y
				fi
				rm -rf /etc/openvpn
				echo
				echo "OpenVPN removed!"
			else
				echo
				echo "Removal aborted!"
			fi
			exit
			;;
			4) exit;;
		esac
	done
else
	clear
	echo 'Welcome to this 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, provide the IPv4 address of the network interface you want OpenVPN"
	echo "listening to."
	# Autodetect IP 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 -p "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 "This server is behind NAT. What is the public IPv4 address or hostname?"
		read -p "Public IP address / hostname: " -e PUBLICIP
	fi
	while [[ -z $UDPPORT && -z $TCPPORT ]]; do
		echo
		echo "What UDP port do you want OpenVPN listening to?"
		echo "If you don't want to create a UDP instance then leave it empty"
		read -p "Port: " -e -i 1194 UDPPORT
		echo
		echo "What TCP port do you want OpenVPN listening to?"
		echo "If you don't want to create a TCP instance then leave it empty"
		read -p "Port: " -e -i 443 TCPPORT
	done
	echo
	echo "Which DNS do you want to use with the VPN?"
	echo "   1) Current system resolvers"
	echo "   2) 1.1.1.1"
	echo "   3) Google"
	echo "   4) OpenDNS"
	echo "   5) Verisign"
	read -p "DNS [1-5]: " -e -i 1 DNS
	case $DNS in
		1)
		# Locate the proper resolv.conf
		# Needed for systems running systemd-resolved
		if grep -q "127.0.0.53" "/etc/resolv.conf"; then
			RESOLVCONF='/run/systemd/resolve/resolv.conf'
		else
			RESOLVCONF='/etc/resolv.conf'
		fi
		# Obtain the resolvers from resolv.conf and use them for OpenVPN
		DNS=$(grep -v '#' $RESOLVCONF | grep 'nameserver' | grep -E -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | tr '\n' ' ')
		;;
		2)
		DNS="1.1.1.1 1.0.0.1"
		;;
		3)
		DNS="8.8.8.8 8.8.4.4"
		;;
		4)
		DNS="208.67.222.222 208.67.220.220"
		;;
		5)
		DNS="64.6.64.6 64.6.65.6"
		;;
	esac
	echo
	echo "Finally, tell me your name for the client certificate."
	echo "Please, use one word only, no special characters."
	read -p "Client name: " -e -i client CLIENT
	echo
	echo "Okay, that was all I needed. We are ready to set up your OpenVPN server now."
	read -n1 -r -p "Press any key to continue..."
	if [[ "$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 ca-certificates -y
	fi
	# Get easy-rsa
	EASYRSAURL='https://github.com/OpenVPN/easy-rsa/releases/download/v3.0.4/EasyRSA-3.0.4.tgz'
	wget -O ~/easyrsa.tgz "$EASYRSAURL" 2>/dev/null || curl -Lo ~/easyrsa.tgz "$EASYRSAURL"
	tar xzf ~/easyrsa.tgz -C ~/
	mv ~/EasyRSA-3.0.4/ /etc/openvpn/
	mv /etc/openvpn/EasyRSA-3.0.4/ /etc/openvpn/easy-rsa/
	chown -R root:root /etc/openvpn/easy-rsa/
	rm -f ~/easyrsa.tgz
	cd /etc/openvpn/easy-rsa/
	# 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 $CLIENT nopass
	EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
	# Move the stuff we need
	cp pki/ca.crt pki/private/ca.key pki/dh.pem pki/issued/server.crt pki/private/server.key pki/crl.pem /etc/openvpn
	# CRL is read with each client connection, when OpenVPN is dropped to nobody
	chown nobody:$GROUPNAME /etc/openvpn/crl.pem
	# Generate key for tls-auth
	openvpn --genkey --secret /etc/openvpn/ta.key
	# Generate server config
	if [[ -n $UDPPORT ]]; then
		newserver $UDPPORT "udp" $UDPNETWORK "$DNS" > /etc/openvpn/server_udp.conf
	fi
	if [[ -n $TCPPORT ]]; then
		newserver $TCPPORT "tcp-server" $TCPNETWORK "$DNS" > /etc/openvpn/server_tcp.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
	if pgrep firewalld; then
		CMD="setfirewall"
	else
		CMD="setiptables"
	fi
	if [[ -n $UDPPORT ]]; then
		$CMD $UDPPORT "udp" $UDPNETWORK $IP
	fi
	if [[ -n $TCPPORT ]]; then
		$CMD $TCPPORT "tcp" $TCPNETWORK $IP
	fi
	# If SELinux is enabled and a custom port was selected, we need this
	if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing"; then
		# Install semanage if not already present
		if ! hash semanage 2>/dev/null; then
			yum install policycoreutils-python -y
		fi
		if [[ -n $UDPPORT && $UDPPORT != "1194" ]]; then
			semanage port -a -t openvpn_port_t -p udp $UDPPORT
		fi
		if [[ -n $TCPPORT && $TCPPORT != "1194" ]]; then
			semanage port -a -t openvpn_port_t -p tcp $TCPPORT
		fi
	fi
	# And finally, restart OpenVPN
	if pgrep systemd-journal; then
		if [[ -n $UDPPORT ]]; then
			systemctl enable openvpn@server_udp.service
		fi
		if [[ -n $UDPPORT ]]; then
			systemctl enable openvpn@server_tcp.service
		fi
		systemctl restart openvpn
	else
		if [[ "$OS" = 'debian' ]]; then
			/etc/init.d/openvpn restart
		else
			service openvpn restart
			chkconfig openvpn on
		fi
	fi
	# If the server is behind a NAT, use the correct IP address
	if [[ "$PUBLICIP" != "" ]]; then
		IP=$PUBLICIP
	fi
	# client-common.txt is created so we have a template to add further users later
	if [[ -n $UDPPORT ]]; then
		echo "remote $IP $UDPPORT udp" >> /etc/openvpn/client-common.txt
	fi
	if [[ -n $TCPPORT ]]; then
		echo "remote $IP $TCPPORT tcp-client" >> /etc/openvpn/client-common.txt
	fi
	echo "client
dev tun
sndbuf 0
rcvbuf 0
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
auth SHA512
cipher AES-256-CBC
comp-lzo
setenv opt block-outside-dns
key-direction 1
verb 3" >> /etc/openvpn/client-common.txt
	# Generates the custom client.ovpn
	newclient "$CLIENT"
	echo
	echo "Finished!"
	echo
	echo "Your client configuration is available at:" ~/"$CLIENT.ovpn"
	echo "If you want to add more clients, you simply need to run this script again!"
fi