diff --git a/openvpn-install.sh b/openvpn-install.sh
index 44647c5..046b319 100644
--- a/openvpn-install.sh
+++ b/openvpn-install.sh
@@ -4,16 +4,19 @@
 # https://github.com/Angristan/OpenVPN-install
 
 
+# Verify root
 if [[ "$EUID" -ne 0 ]]; then
 	echo "Sorry, you need to run this as root"
 	exit 1
 fi
 
+# Verify tun
 if [[ ! -e /dev/net/tun ]]; then
 	echo "TUN is not available"
 	exit 2
 fi
 
+# Check if CentOS 5
 if grep -qs "CentOS release 5" "/etc/redhat-release"; then
 	echo "CentOS 5 is too old and not supported"
 	exit 3
@@ -22,7 +25,7 @@ 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=$(cat /etc/os-release | grep "VERSION_ID")
+	VERSION_ID=$(grep "VERSION_ID" /etc/os-release)
 	IPTABLES='/etc/iptables/iptables.rules'
 	SYSCTL='/etc/sysctl.conf'
 	if [[ "$VERSION_ID" != 'VERSION_ID="7"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="8"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="9"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="14.04"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="16.04"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="17.10"' ]] && [[ "$VERSION_ID" != 'VERSION_ID="18.04"' ]]; then
@@ -33,7 +36,7 @@ if [[ -e /etc/debian_version ]]; then
 		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" && $CONTINUE != "n" ]]; do
-			read -p "Continue ? [y/n]: " -e CONTINUE
+			read -rp "Continue ? [y/n]: " -e CONTINUE
 		done
 		if [[ "$CONTINUE" = "n" ]]; then
 			echo "Ok, bye !"
@@ -59,28 +62,33 @@ fi
 
 newclient () {
 	# Where to write the custom client.ovpn?
-	if [ -e /home/$1 ]; then  # if $1 is a user name
+	if [ -e "/home/$1" ]; then  # if $1 is a user name
 		homeDir="/home/$1"
-	elif [ ${SUDO_USER} ]; then   # if not, use SUDO_USER
+	elif [ "${SUDO_USER}" ]; then   # if not, use SUDO_USER
 		homeDir="/home/${SUDO_USER}"
 	else  # if not SUDO_USER, use /root
 		homeDir="/root"
 	fi
 	# Generates the custom client.ovpn
-	cp /etc/openvpn/client-template.txt $homeDir/$1.ovpn
-	echo "<ca>" >> $homeDir/$1.ovpn
-	cat /etc/openvpn/easy-rsa/pki/ca.crt >> $homeDir/$1.ovpn
-	echo "</ca>" >> $homeDir/$1.ovpn
-	echo "<cert>" >> $homeDir/$1.ovpn
-	cat /etc/openvpn/easy-rsa/pki/issued/$1.crt >> $homeDir/$1.ovpn
-	echo "</cert>" >> $homeDir/$1.ovpn
-	echo "<key>" >> $homeDir/$1.ovpn
-	cat /etc/openvpn/easy-rsa/pki/private/$1.key >> $homeDir/$1.ovpn
-	echo "</key>" >> $homeDir/$1.ovpn
-	echo "key-direction 1" >> $homeDir/$1.ovpn
-	echo "<tls-auth>" >> $homeDir/$1.ovpn
-	cat /etc/openvpn/tls-auth.key >> $homeDir/$1.ovpn
-	echo "</tls-auth>" >> $homeDir/$1.ovpn
+	cp /etc/openvpn/client-template.txt "$homeDir/$1.ovpn"
+	{
+		echo "<ca>"
+		cat "/etc/openvpn/easy-rsa/pki/ca.crt"
+		echo "</ca>"
+
+		echo "<cert>"
+		cat "/etc/openvpn/easy-rsa/pki/issued/$1.crt"
+		echo "</cert>"
+
+		echo "<key>"
+		cat "/etc/openvpn/easy-rsa/pki/private/$1.key"
+		echo "</key>"
+		echo "key-direction 1"
+
+		echo "<tls-auth>"
+		cat "/etc/openvpn/tls-auth.key"
+		echo "</tls-auth>"
+	} >> "$homeDir/$1.ovpn"
 }
 
 # Get Internet network interface with default route
@@ -94,22 +102,27 @@ if [[ -e /etc/openvpn/server.conf ]]; then
 		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
+		read -rp "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 newclient CLIENT
-			cd /etc/openvpn/easy-rsa/
+			read -rp "Client name: " -e -i newclient CLIENT
+
+			cd /etc/openvpn/easy-rsa/ || return
 			./easyrsa build-client-full $CLIENT nopass
+
 			# Generates the custom client.ovpn
 			newclient "$CLIENT"
+
 			echo ""
 			echo "Client $CLIENT added, certs available at $homeDir/$CLIENT.ovpn"
 			exit
@@ -121,16 +134,18 @@ if [[ -e /etc/openvpn/server.conf ]]; then
 				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 [[ "$NUMBEROFCLIENTS" = '1' ]]; then
-				read -p "Select one client [1]: " CLIENTNUMBER
+				read -rp "Select one client [1]: " CLIENTNUMBER
 			else
-				read -p "Select one client [1-$NUMBEROFCLIENTS]: " CLIENTNUMBER
+				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/
+			cd /etc/openvpn/easy-rsa/ || return
 			./easyrsa --batch revoke $CLIENT
 			EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
 			rm -f pki/reqs/$CLIENT.req
@@ -141,6 +156,7 @@ if [[ -e /etc/openvpn/server.conf ]]; then
 			chmod 644 /etc/openvpn/crl.pem
 			rm -f $(find /home -maxdepth 2 | grep $CLIENT.ovpn) 2>/dev/null
 			rm -f /root/$CLIENT.ovpn 2>/dev/null
+
 			echo ""
 			echo "Certificate for client $CLIENT revoked"
 			echo "Exiting..."
@@ -148,7 +164,7 @@ if [[ -e /etc/openvpn/server.conf ]]; then
 			;;
 			3)
 			echo ""
-			read -p "Do you really want to remove OpenVPN? [y/n]: " -e -i n REMOVE
+			read -rp "Do you really want to remove OpenVPN? [y/n]: " -e -i n REMOVE
 			if [[ "$REMOVE" = 'y' ]]; then
 				PORT=$(grep '^port ' /etc/openvpn/server.conf | cut -d " " -f 2)
 				if pgrep firewalld; then
@@ -206,6 +222,7 @@ else
 	clear
 	echo "Welcome to the secure OpenVPN installer (github.com/Angristan/OpenVPN-install)"
 	echo ""
+
 	# OpenVPN setup and first user creation
 	echo "I need to ask you a few questions before starting the setup"
 	echo "You can leave the default options and just press enter if you are ok with them"
@@ -213,23 +230,25 @@ else
 	echo "I need to know the IPv4 address of the network interface you want OpenVPN listening to."
 	echo "If your server is running behind a NAT, (e.g. LowEndSpirit, Scaleway) leave the IP address as it is. (local/private IP)"
 	echo "Otherwise, it should be your public IPv4 address."
+
 	# Autodetect IP address and pre-fill for the user
 	IP=$(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
+	read -rp "IP address: " -e -i $IP IP
 	echo ""
 	echo "What port do you want for OpenVPN?"
-	read -p "Port: " -e -i 1194 PORT
+	read -rp "Port: " -e -i 1194 PORT
+
 	# 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
+		read -rp "Public IP address / hostname: " -e PUBLICIP
 	fi
 	echo ""
 	echo "What protocol do you want for OpenVPN?"
 	echo "Unless UDP is blocked, you should not use TCP (unnecessarily slower)"
-	while [[ $PROTOCOL != "UDP" && $PROTOCOL != "TCP" ]]; do
-		read -p "Protocol [UDP/TCP]: " -e -i UDP PROTOCOL
+	until [[ "$PROTOCOL" == "UDP" || "$PROTOCOL" == "TCP" ]]; do
+		read -rp "Protocol [UDP/TCP]: " -e -i UDP PROTOCOL
 	done
 	echo ""
 	echo "What DNS do you want to use with the VPN?"
@@ -242,8 +261,8 @@ else
 	echo "   7) Google (Anycast: worldwide)"
 	echo "   8) Yandex Basic (Russia)"
 	echo "   9) AdGuard DNS (Russia)"
-	while [[ $DNS != "1" && $DNS != "2" && $DNS != "3" && $DNS != "4" && $DNS != "5" && $DNS != "6" && $DNS != "7" && $DNS != "8" && $DNS != "9" ]]; do
-		read -p "DNS [1-9]: " -e -i 1 DNS
+	until [[ "$DNS" =~ ^[0-9]+$ ]] && [ "$DNS" -ge 1 -a "$DNS" -le 9 ]; do
+		read -rp "DNS [1-9]: " -e -i 1 DNS
 	done
 	echo ""
 	echo "See https://github.com/Angristan/OpenVPN-install#encryption to learn more about "
@@ -261,8 +280,8 @@ else
 	echo "   5) CAMELLIA-192-CBC"
 	echo "   6) CAMELLIA-256-CBC"
 	echo "   7) SEED-CBC"
-	while [[ $CIPHER != "1" && $CIPHER != "2" && $CIPHER != "3" && $CIPHER != "4" && $CIPHER != "5" && $CIPHER != "6" && $CIPHER != "7" ]]; do
-		read -p "Cipher [1-7]: " -e -i 1 CIPHER
+	until [[ "$CIPHER" =~ ^[0-9]+$ ]] && [ "$CIPHER" -ge 1 -a "$CIPHER" -le 7 ]; do
+		read -rp "Cipher [1-7]: " -e -i 1 CIPHER
 	done
 	case $CIPHER in
 		1)
@@ -292,8 +311,8 @@ else
 	echo "   1) 2048 bits (fastest)"
 	echo "   2) 3072 bits (recommended, best compromise)"
 	echo "   3) 4096 bits (most secure)"
-	while [[ $DH_KEY_SIZE != "1" && $DH_KEY_SIZE != "2" && $DH_KEY_SIZE != "3" ]]; do
-		read -p "DH key size [1-3]: " -e -i 2 DH_KEY_SIZE
+	until [[ "$DH_KEY_SIZE" =~ ^[0-9]+$ ]] && [ "$DH_KEY_SIZE" -ge 1 -a "$DH_KEY_SIZE" -le 3 ]; do
+		read -rp "DH key size [1-3]: " -e -i 2 DH_KEY_SIZE
 	done
 	case $DH_KEY_SIZE in
 		1)
@@ -311,8 +330,8 @@ else
 	echo "   1) 2048 bits (fastest)"
 	echo "   2) 3072 bits (recommended, best compromise)"
 	echo "   3) 4096 bits (most secure)"
-	while [[ $RSA_KEY_SIZE != "1" && $RSA_KEY_SIZE != "2" && $RSA_KEY_SIZE != "3" ]]; do
-		read -p "RSA key size [1-3]: " -e -i 2 RSA_KEY_SIZE
+	until [[ "$RSA_KEY_SIZE" =~ ^[0-9]+$ ]] && [ "$RSA_KEY_SIZE" -ge 1 -a "$RSA_KEY_SIZE" -le 3 ]; do
+		read -rp "RSA key size [1-3]: " -e -i 2 RSA_KEY_SIZE
 	done
 	case $RSA_KEY_SIZE in
 		1)
@@ -329,7 +348,9 @@ else
 	echo "Finally, tell me a name for the client certificate and configuration"
 	while [[ $CLIENT = "" ]]; do
 		echo "Please, use one word only, no special characters"
-		read -p "Client name: " -e -i client CLIENT
+		read -rp "Client name: " -e -i client CLIENT
+		# Remove special characters
+		CLIENT=$(echo $CLIENT | tr -dc '[:alnum:]\n\r')
 	done
 	echo ""
 	echo "Okay, that was all I needed. We are ready to setup your OpenVPN server now"
@@ -437,8 +458,8 @@ WantedBy=multi-user.target" > /etc/systemd/system/iptables.service
 		echo "Not doing that could cause problems between dependencies, or missing files in repositories."
 		echo ""
 		echo "Continuing will update your installed packages and install needed ones."
-		while [[ $CONTINUE != "y" && $CONTINUE != "n" ]]; do
-			read -p "Continue ? [y/n]: " -e -i y CONTINUE
+		until [[ $CONTINUE == "y" || $CONTINUE == "n" ]]; do
+			read -rp "Continue ? [y/n]: " -e -i y CONTINUE
 		done
 		if [[ "$CONTINUE" = "n" ]]; then
 			echo "Ok, bye !"
@@ -472,10 +493,10 @@ WantedBy=multi-user.target" > /etc/systemd/system/iptables.service
 	mv /etc/openvpn/EasyRSA-3.0.4/ /etc/openvpn/easy-rsa/
 	chown -R root:root /etc/openvpn/easy-rsa/
 	rm -f ~/EasyRSA-3.0.4.tgz
-	cd /etc/openvpn/easy-rsa/
+	cd /etc/openvpn/easy-rsa/ || return
 	# Generate a random, alphanumeric identifier of 16 characters for CN and one for server name
-	SERVER_CN="cn_$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 1)"
-	SERVER_NAME="server_$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 | head -n 1)"
+	SERVER_CN="cn_$(tr -dc 'a-zA-Z0-9' < /dev/urandom | fold -w 16 | head -n 1)"
+	SERVER_NAME="server_$(tr -dc 'a-zA-Z0-9' < /dev/urandom | fold -w 16 | head -n 1)"
 	echo "set_var EASYRSA_KEY_SIZE $RSA_KEY_SIZE" > vars
 	echo "set_var EASYRSA_REQ_CN $SERVER_CN" >> vars
 	# Create the PKI, set up the CA, the DH params and the server + client certificates
@@ -494,11 +515,7 @@ WantedBy=multi-user.target" > /etc/systemd/system/iptables.service
 
 	# 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 "proto $(echo $PROTOCOL | tr '[:upper:]' '[:lower:]')" >> /etc/openvpn/server.conf
 	echo "dev tun
 user nobody
 group $NOGROUP
@@ -519,7 +536,7 @@ ifconfig-pool-persist ipp.txt" >> /etc/openvpn/server.conf
 			RESOLVCONF='/etc/resolv.conf'
 		fi
 		# Obtain the resolvers from resolv.conf and use them for OpenVPN
-		grep -v '#' $RESOLVCONF | 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
+		grep -v '#' $RESOLVCONF | grep 'nameserver' | grep -E -o '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' | while read -r line; do
 			echo "push \"dhcp-option DNS $line\"" >> /etc/openvpn/server.conf
 		done
 		;;
@@ -556,7 +573,7 @@ ifconfig-pool-persist ipp.txt" >> /etc/openvpn/server.conf
 		echo 'push "dhcp-option DNS 176.103.130.131"' >> /etc/openvpn/server.conf
 		;;
 	esac
-echo 'push "redirect-gateway def1 bypass-dhcp" '>> /etc/openvpn/server.conf
+echo 'push "redirect-gateway def1 bypass-dhcp" ' >> /etc/openvpn/server.conf
 echo "crl-verify crl.pem
 ca ca.crt
 cert $SERVER_NAME.crt
@@ -581,12 +598,16 @@ verb 3" >> /etc/openvpn/server.conf
 	if ! grep -q "\<net.ipv4.ip_forward\>" $SYSCTL; then
 		echo 'net.ipv4.ip_forward=1' >> $SYSCTL
 	fi
+
 	# Avoid an unneeded reboot
 	echo 1 > /proc/sys/net/ipv4/ip_forward
+
 	# Set NAT for the VPN subnet
 	iptables -t nat -A POSTROUTING -o $NIC -s 10.8.0.0/24 -j MASQUERADE
+
 	# Save persitent iptables rules
 	iptables-save > $IPTABLES
+
 	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
@@ -601,6 +622,7 @@ verb 3" >> /etc/openvpn/server.conf
 		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
@@ -613,8 +635,9 @@ verb 3" >> /etc/openvpn/server.conf
 		iptables -I FORWARD -s 10.8.0.0/24 -j ACCEPT
 		iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
 		# Save persitent OpenVPN rules
-        iptables-save > $IPTABLES
+		iptables-save > $IPTABLES
 	fi
+
 	# If SELinux is enabled and a custom port was selected, we need this
 	if hash sestatus 2>/dev/null; then
 		if sestatus | grep "Current mode" | grep -qs "enforcing"; then
@@ -631,6 +654,7 @@ verb 3" >> /etc/openvpn/server.conf
 			fi
 		fi
 	fi
+
 	# And finally, restart OpenVPN
 	if [[ "$OS" = 'debian' ]]; then
 		# Little hack to check for systemd
@@ -663,10 +687,12 @@ verb 3" >> /etc/openvpn/server.conf
 			chkconfig openvpn on
 		fi
 	fi
+
 	# If the server is behind a NAT, use the correct IP address
 	if [[ "$PUBLICIP" != "" ]]; then
 		IP=$PUBLICIP
 	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