feat(openvpn): add interactive subnet prompt in firewall config

Introduce an interactive prompt for specifying allowed subnets for VPN clients (10.8.0.0/24). The script now builds custom iptables rules based on user input and persists them via a systemd service, while retaining the original EasyRSA extraction and configuration.

openvpn-install.sh

@@ -3,7 +3,7 @@
 # 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
@@ -14,8 +14,7 @@ fi
 # Discard stdin. Needed when running from a one-liner which includes a newline
 read -N 999999 -t 0.001
 
-# Detect OS
+# Detect OS (with some variables kept for convenience)
-# $os_version variables aren't always in use, but are kept here for convenience
 if grep -qs "ubuntu" /etc/os-release; then
     os="ubuntu"
     os_version=$(grep 'VERSION_ID' /etc/os-release | cut -d '"' -f 2 | tr -d '.')
@@ -103,7 +102,7 @@ new_client () {
 }
 
 if [[ ! -e /etc/openvpn/server/server.conf ]]; then
-	# Detect some Debian minimal setups where neither wget nor curl are installed
+    # Detect minimal setups where neither wget nor curl are installed
     if ! hash wget 2>/dev/null && ! hash curl 2>/dev/null; then
         echo "Wget is required to use this installer."
         read -n1 -r -p "Press any key to install Wget and continue..."
@@ -112,7 +111,7 @@ if [[ ! -e /etc/openvpn/server/server.conf ]]; then
     fi
     clear
     echo 'Welcome to this OpenVPN road warrior installer!'
-	# If system has a single IPv4, it is selected automatically. Else, ask the user
+    # Choose IPv4 address (if only one exists, it is selected automatically)
     if [[ $(ip -4 addr | grep inet | grep -vEc '127(\.[0-9]{1,3}){3}') -eq 1 ]]; then
         ip=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}')
     else
@@ -128,25 +127,22 @@ if [[ ! -e /etc/openvpn/server/server.conf ]]; then
         [[ -z "$ip_number" ]] && ip_number="1"
         ip=$(ip -4 addr | grep inet | grep -vE '127(\.[0-9]{1,3}){3}' | cut -d '/' -f 1 | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | sed -n "$ip_number"p)
     fi
-	# If $ip is a private IP address, the server must be behind NAT
+    # If $ip is private, ask for public IP or hostname
     if echo "$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?"
-		# Get public IP and sanitize with grep
         get_public_ip=$(grep -m 1 -oE '^[0-9]{1,3}(\.[0-9]{1,3}){3}$' <<< "$(wget -T 10 -t 1 -4qO- "http://ip1.dynupdate.no-ip.com/" || curl -m 10 -4Ls "http://ip1.dynupdate.no-ip.com/")")
         read -p "Public IPv4 address / hostname [$get_public_ip]: " public_ip
-		# If the checkip service is unavailable and user didn't provide input, ask again
         until [[ -n "$get_public_ip" || -n "$public_ip" ]]; do
             echo "Invalid input."
             read -p "Public IPv4 address / hostname: " public_ip
         done
         [[ -z "$public_ip" ]] && public_ip="$get_public_ip"
     fi
-	# If system has a single IPv6, it is selected automatically
+    # Determine IPv6 address if available
     if [[ $(ip -6 addr | grep -c 'inet6 [23]') -eq 1 ]]; then
         ip6=$(ip -6 addr | grep 'inet6 [23]' | cut -d '/' -f 1 | grep -oE '([0-9a-fA-F]{0,4}:){1,7}[0-9a-fA-F]{0,4}')
     fi
-	# If system has multiple IPv6, ask the user to select one
     if [[ $(ip -6 addr | grep -c 'inet6 [23]') -gt 1 ]]; then
         number_of_ip6=$(ip -6 addr | grep -c 'inet6 [23]')
         echo
@@ -199,15 +195,12 @@ if [[ ! -e /etc/openvpn/server/server.conf ]]; then
         echo "$dns: invalid selection."
         read -p "DNS server [1]: " dns
     done
-	# If the user selected custom resolvers, we deal with that here
     if [[ "$dns" = "7" ]]; then
         echo
         until [[ -n "$custom_dns" ]]; do
             echo "Enter DNS servers (one or more IPv4 addresses, separated by commas or spaces):"
             read -p "DNS servers: " dns_input
-			# Convert comma delimited to space delimited
             dns_input=$(echo "$dns_input" | tr ',' ' ')
-			# Validate and build custom DNS IP list
             for dns_ip in $dns_input; do
                 if [[ "$dns_ip" =~ ^[0-9]{1,3}(\.[0-9]{1,3}){3}$ ]]; then
                     if [[ -z "$custom_dns" ]]; then
@@ -225,30 +218,30 @@ if [[ ! -e /etc/openvpn/server/server.conf ]]; then
     echo
     echo "Enter a name for the first client:"
     read -p "Name [client]: " unsanitized_client
-	# Allow a limited set of characters to avoid conflicts
     client=$(sed 's/[^0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-]/_/g' <<< "$unsanitized_client")
     [[ -z "$client" ]] && client="client"
     echo
     echo "OpenVPN installation is ready to begin."
-	# Install a firewall if firewalld or iptables are not already available
+    
+    # Install firewall package if necessary
     if ! systemctl is-active --quiet firewalld.service && ! hash iptables 2>/dev/null; then
         if [[ "$os" == "centos" || "$os" == "fedora" ]]; then
             firewall="firewalld"
-			# We don't want to silently enable firewalld, so we give a subtle warning
-			# If the user continues, firewalld will be installed and enabled during setup
             echo "firewalld, which is required to manage routing tables, will also be installed."
         elif [[ "$os" == "debian" || "$os" == "ubuntu" ]]; then
-			# iptables is way less invasive than firewalld so no warning is given
             firewall="iptables"
         fi
     fi
     read -n1 -r -p "Press any key to continue..."
+    
     # If running inside a container, disable LimitNPROC to prevent conflicts
     if systemd-detect-virt -cq; then
         mkdir /etc/systemd/system/openvpn-server@server.service.d/ 2>/dev/null
         echo "[Service]
 LimitNPROC=infinity" > /etc/systemd/system/openvpn-server@server.service.d/disable-limitnproc.conf
     fi
+    
+    # Install OpenVPN and prerequisites
     if [[ "$os" = "debian" || "$os" = "ubuntu" ]]; then
         apt-get update
         apt-get install -y --no-install-recommends openvpn openssl ca-certificates $firewall
@@ -256,34 +249,36 @@ LimitNPROC=infinity" > /etc/systemd/system/openvpn-server@server.service.d/disab
         dnf install -y epel-release
         dnf install -y openvpn openssl ca-certificates tar $firewall
     else
-		# Else, OS must be Fedora
         dnf install -y openvpn openssl ca-certificates tar $firewall
     fi
-	# If firewalld was just installed, enable it
+    
     if [[ "$firewall" == "firewalld" ]]; then
         systemctl enable --now firewalld.service
     fi
-	# Get easy-rsa
+    
+    # Get EasyRSA: Create the directory and extract EasyRSA files
     easy_rsa_url='https://github.com/OpenVPN/easy-rsa/releases/download/v3.2.2/EasyRSA-3.2.2.tgz'
     mkdir -p /etc/openvpn/server/easy-rsa/
-	{ wget -qO- "$easy_rsa_url" 2>/dev/null || curl -sL "$easy_rsa_url" ; } | tar xz -C /etc/openvpn/server/easy-rsa/ --strip-components 1
+    { wget -qO- "$easy_rsa_url" 2>/dev/null || curl -sL "$easy_rsa_url" ; } | tar xz -C /etc/openvpn/server/easy-rsa/ --strip-components=1
     chown -R root:root /etc/openvpn/server/easy-rsa/
     cd /etc/openvpn/server/easy-rsa/
-	# Create the PKI, set up the CA and the server and client certificates
+    
+    # Create the PKI, set up the CA, and generate server and client certificates
     ./easyrsa --batch init-pki
     ./easyrsa --batch build-ca nopass
     ./easyrsa --batch --days=3650 build-server-full server nopass
     ./easyrsa --batch --days=3650 build-client-full "$client" nopass
     ./easyrsa --batch --days=3650 gen-crl
-	# Move the stuff we need
+    
+    # Move necessary files to /etc/openvpn/server
     cp pki/ca.crt pki/private/ca.key pki/issued/server.crt pki/private/server.key pki/crl.pem /etc/openvpn/server
-	# CRL is read with each client connection, while OpenVPN is dropped to nobody
     chown nobody:"$group_name" /etc/openvpn/server/crl.pem
-	# Without +x in the directory, OpenVPN can't run a stat() on the CRL file
     chmod o+x /etc/openvpn/server/
+    
     # Generate key for tls-crypt
     openvpn --genkey secret /etc/openvpn/server/tc.key
-	# Create the DH parameters file using the predefined ffdhe2048 group
+    
+    # Create the DH parameters file using ffdhe2048
     echo '-----BEGIN DH PARAMETERS-----
 MIIBCAKCAQEA//////////+t+FRYortKmq/cViAnPTzx2LnFg84tNpWp4TZBFGQz
 +8yTnc4kmz75fS/jY2MMddj2gbICrsRhetPfHtXV/WVhJDP1H18GbtCFY2VVPe0a
@@ -292,6 +287,7 @@ YdEIqUuyyOP7uWrat2DX9GgdT0Kj3jlN9K5W7edjcrsZCwenyO4KbXCeAvzhzffi
 7MA0BM0oNC9hkXL+nOmFg/+OTxIy7vKBg8P+OxtMb61zO7X8vC7CIAXFjvGDfRaD
 ssbzSibBsu/6iGtCOGEoXJf//////////wIBAg==
 -----END DH PARAMETERS-----' > /etc/openvpn/server/dh.pem
+    
     # Generate server.conf
     echo "local $ip
 port $port
@@ -305,7 +301,6 @@ auth SHA512
 tls-crypt tc.key
 topology subnet
 server 10.8.0.0 255.255.255.0" > /etc/openvpn/server/server.conf
-	# IPv6
     if [[ -z "$ip6" ]]; then
         echo 'push "redirect-gateway def1 bypass-dhcp"' >> /etc/openvpn/server/server.conf
     else
@@ -313,17 +308,14 @@ server 10.8.0.0 255.255.255.0" > /etc/openvpn/server/server.conf
         echo 'push "redirect-gateway def1 ipv6 bypass-dhcp"' >> /etc/openvpn/server/server.conf
     fi
     echo 'ifconfig-pool-persist ipp.txt' >> /etc/openvpn/server/server.conf
-	# DNS
+    # DNS configuration
     case "$dns" in
         1|"")
-			# Locate the proper resolv.conf
-			# Needed for systems running systemd-resolved
             if grep '^nameserver' "/etc/resolv.conf" | grep -qv '127.0.0.53' ; then
                 resolv_conf="/etc/resolv.conf"
             else
                 resolv_conf="/run/systemd/resolve/resolv.conf"
             fi
-			# Obtain the resolvers from resolv.conf and use them for OpenVPN
             grep -v '^#\|^;' "$resolv_conf" | grep '^nameserver' | grep -v '127.0.0.53' | grep -oE '[0-9]{1,3}(\.[0-9]{1,3}){3}' | while read line; do
                 echo "push \"dhcp-option DNS $line\"" >> /etc/openvpn/server/server.conf
             done
@@ -365,26 +357,17 @@ crl-verify crl.pem" >> /etc/openvpn/server/server.conf
     if [[ "$protocol" = "udp" ]]; then
         echo "explicit-exit-notify" >> /etc/openvpn/server/server.conf
     fi
-	# Enable net.ipv4.ip_forward for the system
     echo 'net.ipv4.ip_forward=1' > /etc/sysctl.d/99-openvpn-forward.conf
-	# Enable without waiting for a reboot or service restart
     echo 1 > /proc/sys/net/ipv4/ip_forward
     if [[ -n "$ip6" ]]; then
-		# Enable net.ipv6.conf.all.forwarding for the system
         echo "net.ipv6.conf.all.forwarding=1" >> /etc/sysctl.d/99-openvpn-forward.conf
-		# Enable without waiting for a reboot or service restart
         echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
     fi
     if systemctl is-active --quiet firewalld.service; then
-		# Using both permanent and not permanent rules to avoid a firewalld
-		# reload.
-		# We don't use --add-service=openvpn because that would only work with
-		# the default port and protocol.
         firewall-cmd --add-port="$port"/"$protocol"
         firewall-cmd --zone=trusted --add-source=10.8.0.0/24
         firewall-cmd --permanent --add-port="$port"/"$protocol"
         firewall-cmd --permanent --zone=trusted --add-source=10.8.0.0/24
-		# Set NAT for the VPN subnet
         firewall-cmd --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
         firewall-cmd --permanent --direct --add-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to "$ip"
         if [[ -n "$ip6" ]]; then
@@ -394,52 +377,70 @@ crl-verify crl.pem" >> /etc/openvpn/server/server.conf
             firewall-cmd --permanent --direct --add-rule ipv6 nat POSTROUTING 0 -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to "$ip6"
         fi
     else
-		# Create a service to set up persistent iptables rules
         iptables_path=$(command -v iptables)
         ip6tables_path=$(command -v ip6tables)
-		# nf_tables is not available as standard in OVZ kernels. So use iptables-legacy
-		# if we are in OVZ, with a nf_tables backend and iptables-legacy is available.
         if [[ $(systemd-detect-virt) == "openvz" ]] && readlink -f "$(command -v iptables)" | grep -q "nft" && hash iptables-legacy 2>/dev/null; then
             iptables_path=$(command -v iptables-legacy)
             ip6tables_path=$(command -v ip6tables-legacy)
         fi
-		echo "[Unit]
+        read -p "Enter allowed subnets for VPN access (separated by spaces or commas): " allowed_input
+        allowed_subnets=$(echo "$allowed_input" | tr ',' ' ' | xargs)
+        echo "Allowed subnets: $allowed_subnets"
+        custom_rules=""
+        for subnet in $allowed_subnets; do
+            custom_rules="${custom_rules}\nExecStart=${iptables_path} -w 5 -A VPN_FILTER -d ${subnet} -j ACCEPT"
+        done
+        cat <<EOF > /etc/systemd/system/openvpn-iptables.service
+[Unit]
 After=network-online.target
 Wants=network-online.target
+
 [Service]
 Type=oneshot
-ExecStart=$iptables_path -w 5 -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $ip
+RemainAfterExit=yes
-ExecStart=$iptables_path -w 5 -I INPUT -p $protocol --dport $port -j ACCEPT
+ExecStart=${iptables_path} -w 5 -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to ${ip}
-ExecStart=$iptables_path -w 5 -I FORWARD -s 10.8.0.0/24 -j ACCEPT
+ExecStart=${iptables_path} -w 5 -I INPUT -p ${protocol} --dport ${port} -j ACCEPT
-ExecStart=$iptables_path -w 5 -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
+ExecStart=${iptables_path} -w 5 -I FORWARD -s 10.8.0.0/24 -j ACCEPT
-ExecStop=$iptables_path -w 5 -t nat -D POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $ip
+ExecStart=${iptables_path} -w 5 -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
-ExecStop=$iptables_path -w 5 -D INPUT -p $protocol --dport $port -j ACCEPT
+ExecStart=-${iptables_path} -w 5 -N VPN_FILTER
-ExecStop=$iptables_path -w 5 -D FORWARD -s 10.8.0.0/24 -j ACCEPT
+ExecStart=${iptables_path} -w 5 -A VPN_FILTER -m state --state RELATED,ESTABLISHED -j ACCEPT
-ExecStop=$iptables_path -w 5 -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" > /etc/systemd/system/openvpn-iptables.service
+ExecStart=${iptables_path} -w 5 -A VPN_FILTER -p tcp -m multiport --dports 22,80,443,8000,9000,8001,8002 -j ACCEPT
+ExecStart=${iptables_path} -w 5 -A VPN_FILTER -p udp --dport 1195 -j ACCEPT
+$custom_rules
+ExecStart=${iptables_path} -w 5 -I FORWARD -s 10.8.0.0/24 -j VPN_FILTER
+ExecStart=${iptables_path} -w 5 -A VPN_FILTER -j DROP
+ExecStop=${iptables_path} -w 5 -t nat -D POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to ${ip}
+ExecStop=${iptables_path} -w 5 -D INPUT -p ${protocol} --dport ${port} -j ACCEPT
+ExecStop=${iptables_path} -w 5 -D FORWARD -s 10.8.0.0/24 -j ACCEPT
+ExecStop=${iptables_path} -w 5 -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
+ExecStop=${iptables_path} -w 5 -F VPN_FILTER
+ExecStop=${iptables_path} -w 5 -X VPN_FILTER
+EOF
         if [[ -n "$ip6" ]]; then
-			echo "ExecStart=$ip6tables_path -w 5 -t nat -A POSTROUTING -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to $ip6
+            cat <<EOF >> /etc/systemd/system/openvpn-iptables.service
-ExecStart=$ip6tables_path -w 5 -I FORWARD -s fddd:1194:1194:1194::/64 -j ACCEPT
+ExecStart=${ip6tables_path} -w 5 -t nat -A POSTROUTING -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to ${ip6}
-ExecStart=$ip6tables_path -w 5 -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
+ExecStart=${ip6tables_path} -w 5 -I FORWARD -s fddd:1194:1194:1194::/64 -j ACCEPT
-ExecStop=$ip6tables_path -w 5 -t nat -D POSTROUTING -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to $ip6
+ExecStart=${ip6tables_path} -w 5 -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
-ExecStop=$ip6tables_path -w 5 -D FORWARD -s fddd:1194:1194:1194::/64 -j ACCEPT
+ExecStop=${ip6tables_path} -w 5 -t nat -D POSTROUTING -s fddd:1194:1194:1194::/64 ! -d fddd:1194:1194:1194::/64 -j SNAT --to ${ip6}
-ExecStop=$ip6tables_path -w 5 -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" >> /etc/systemd/system/openvpn-iptables.service
+ExecStop=${ip6tables_path} -w 5 -D FORWARD -s fddd:1194:1194:1194::/64 -j ACCEPT
+ExecStop=${ip6tables_path} -w 5 -D FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
+EOF
         fi
-		echo "RemainAfterExit=yes
+        cat <<EOF >> /etc/systemd/system/openvpn-iptables.service
 [Install]
-WantedBy=multi-user.target" >> /etc/systemd/system/openvpn-iptables.service
+WantedBy=multi-user.target
+EOF
         systemctl enable --now openvpn-iptables.service
     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" && [[ "$port" != 1194 ]]; then
-		# Install semanage if not already present
         if ! hash semanage 2>/dev/null; then
             dnf install -y policycoreutils-python-utils
         fi
         semanage port -a -t openvpn_port_t -p "$protocol" "$port"
     fi
-	# If the server is behind NAT, use the correct IP address
+
     [[ -n "$public_ip" ]] && ip="$public_ip"
-	# client-common.txt is created so we have a template to add further users later
     echo "client
 dev tun
 proto $protocol
@@ -452,9 +453,7 @@ remote-cert-tls server
 auth SHA512
 ignore-unknown-option block-outside-dns
 verb 3" > /etc/openvpn/server/client-common.txt
-	# Enable and start the OpenVPN service
     systemctl enable --now openvpn-server@server.service
-	# Generates the custom client.ovpn
     new_client
     echo
     echo "Finished!"
@@ -488,15 +487,12 @@ else
             done
             cd /etc/openvpn/server/easy-rsa/
             ./easyrsa --batch --days=3650 build-client-full "$client" nopass
-			# Generates the custom client.ovpn
             new_client
             echo
             echo "$client added. Configuration available in:" "$script_dir"/"$client.ovpn"
             exit
             ;;
         2)
-			# This option could be documented a bit better and maybe even be simplified
-			# ...but what can I say, I want some sleep too
             number_of_clients=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V")
             if [[ "$number_of_clients" = 0 ]]; then
                 echo
@@ -526,7 +522,6 @@ else
                 rm -f /etc/openvpn/server/easy-rsa/pki/reqs/"$client".req
                 rm -f /etc/openvpn/server/easy-rsa/pki/private/"$client".key
                 cp /etc/openvpn/server/easy-rsa/pki/crl.pem /etc/openvpn/server/crl.pem
-				# CRL is read with each client connection, when OpenVPN is dropped to nobody
                 chown nobody:"$group_name" /etc/openvpn/server/crl.pem
                 echo
                 echo "$client revoked!"
@@ -548,7 +543,6 @@ else
                 protocol=$(grep '^proto ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
                 if systemctl is-active --quiet firewalld.service; then
                     ip=$(firewall-cmd --direct --get-rules ipv4 nat POSTROUTING | grep '\-s 10.8.0.0/24 '"'"'!'"'"' -d 10.8.0.0/24' | grep -oE '[^ ]+$')
-					# Using both permanent and not permanent rules to avoid a firewalld reload.
                     firewall-cmd --remove-port="$port"/"$protocol"
                     firewall-cmd --zone=trusted --remove-source=10.8.0.0/24
                     firewall-cmd --permanent --remove-port="$port"/"$protocol"
@@ -576,7 +570,6 @@ else
                     rm -rf /etc/openvpn/server
                     apt-get remove --purge -y openvpn
                 else
-					# Else, OS must be CentOS or Fedora
                     dnf remove -y openvpn
                     rm -rf /etc/openvpn/server
                 fi