feat: add configurable VPN subnet (#1394)

Allow users to customize the VPN subnet during installation instead of
using the hardcoded `10.8.0.0/24`.

- Add subnet prompt during interactive installation (default or custom)
- Add `VPN_SUBNET` environment variable for headless installs
- Validate RFC1918 /24 networks (e.g., `10.9.0.0`, `172.16.0.0`,
`192.168.1.0`)

Closes https://github.com/angristan/openvpn-install/issues/153
Closes https://github.com/angristan/openvpn-install/pull/550
Closes https://github.com/angristan/openvpn-install/pull/1150
Closes https://github.com/angristan/openvpn-install/pull/952
Closes https://github.com/angristan/openvpn-install/pull/551

Co-authored-by: browningluke <lrbrowning6@gmail.com>
This commit is contained in:
Stanislas
2025-12-14 10:54:52 +01:00
committed by GitHub
parent cb0ef7b1c2
commit e9deb4b8ab
4 changed files with 86 additions and 30 deletions

View File

@@ -465,8 +465,8 @@ function installUnbound() {
{
echo 'server:'
echo ' # OpenVPN DNS resolver configuration'
echo ' interface: 10.8.0.1'
echo ' access-control: 10.8.0.0/24 allow'
echo " interface: $VPN_GATEWAY"
echo " access-control: $VPN_SUBNET/24 allow"
echo ''
echo ' # Security hardening'
echo ' hide-identity: yes'
@@ -617,6 +617,28 @@ function installQuestions() {
read -rp "Do you want to enable IPv6 support (NAT)? [y/n]: " -e -i $SUGGESTION IPV6_SUPPORT
done
log_menu ""
log_prompt "What subnet do you want for the VPN?"
log_menu " 1) Default: 10.8.0.0/24"
log_menu " 2) Custom"
until [[ $SUBNET_CHOICE =~ ^[1-2]$ ]]; do
read -rp "Subnet choice [1-2]: " -e -i 1 SUBNET_CHOICE
done
case $SUBNET_CHOICE in
1)
VPN_SUBNET="10.8.0.0"
;;
2)
# Skip prompt if VPN_SUBNET is already set (e.g., via environment variable)
if [[ -z $VPN_SUBNET ]]; then
until [[ $VPN_SUBNET =~ ^(10\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])|172\.(1[6-9]|2[0-9]|3[0-1])\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])|192\.168\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9]))\.0$ ]]; do
read -rp "Custom subnet (e.g., 10.9.0.0): " VPN_SUBNET
done
fi
;;
esac
# Calculate gateway (first usable IP in the subnet)
VPN_GATEWAY="${VPN_SUBNET%.*}.1"
log_menu ""
log_prompt "What port do you want OpenVPN to listen to?"
log_menu " 1) Default: 1194"
log_menu " 2) Custom"
@@ -979,6 +1001,13 @@ function installOpenVPN() {
APPROVE_INSTALL=${APPROVE_INSTALL:-y}
APPROVE_IP=${APPROVE_IP:-y}
IPV6_SUPPORT=${IPV6_SUPPORT:-n}
# If VPN_SUBNET is provided, use custom choice; otherwise use default
if [[ -n $VPN_SUBNET ]]; then
SUBNET_CHOICE=${SUBNET_CHOICE:-2}
else
SUBNET_CHOICE=${SUBNET_CHOICE:-1}
VPN_SUBNET="10.8.0.0"
fi
PORT_CHOICE=${PORT_CHOICE:-1}
PROTOCOL_CHOICE=${PROTOCOL_CHOICE:-1}
DNS=${DNS:-3}
@@ -1001,6 +1030,7 @@ function installOpenVPN() {
log_info "Running in auto-install mode with the following settings:"
log_info " ENDPOINT=$ENDPOINT"
log_info " IPV6_SUPPORT=$IPV6_SUPPORT"
log_info " VPN_SUBNET=$VPN_SUBNET"
log_info " PORT_CHOICE=$PORT_CHOICE"
log_info " PROTOCOL_CHOICE=$PROTOCOL_CHOICE"
log_info " DNS=$DNS"
@@ -1219,7 +1249,7 @@ group $OPENVPN_GROUP" >>/etc/openvpn/server/server.conf
persist-tun
keepalive 10 120
topology subnet
server 10.8.0.0 255.255.255.0" >>/etc/openvpn/server/server.conf
server $VPN_SUBNET 255.255.255.0" >>/etc/openvpn/server/server.conf
# ifconfig-pool-persist is incompatible with duplicate-cn
if [[ $MULTI_CLIENT != "y" ]]; then
@@ -1245,7 +1275,7 @@ server 10.8.0.0 255.255.255.0" >>/etc/openvpn/server/server.conf
done
;;
2) # Self-hosted DNS resolver (Unbound)
echo 'push "dhcp-option DNS 10.8.0.1"' >>/etc/openvpn/server/server.conf
echo "push \"dhcp-option DNS $VPN_GATEWAY\"" >>/etc/openvpn/server/server.conf
if [[ $IPV6_SUPPORT == 'y' ]]; then
echo 'push "dhcp-option DNS fd42:42:42:42::1"' >>/etc/openvpn/server/server.conf
fi
@@ -1430,7 +1460,7 @@ verb 3" >>/etc/openvpn/server/server.conf
run_cmd "Adding masquerade to firewalld" firewall-cmd --permanent --add-masquerade
# Add rich rules for VPN traffic (source-based rules work reliably with dynamic tun0 interface)
run_cmd "Adding VPN subnet rule" firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="10.8.0.0/24" accept'
run_cmd "Adding VPN subnet rule" firewall-cmd --permanent --add-rich-rule="rule family=\"ipv4\" source address=\"$VPN_SUBNET/24\" accept"
if [[ $IPV6_SUPPORT == 'y' ]]; then
run_cmd "Adding IPv6 source rule" firewall-cmd --permanent --add-rich-rule='rule family="ipv6" source address="fd42:42:42:42::/112" accept'
@@ -1460,7 +1490,7 @@ verb 3" >>/etc/openvpn/server/server.conf
table ip openvpn-nat {
chain postrouting {
type nat hook postrouting priority 100; policy accept;
ip saddr 10.8.0.0/24 oifname \"$NIC\" masquerade
ip saddr $VPN_SUBNET/24 oifname \"$NIC\" masquerade
}
}" >/etc/nftables/openvpn.nft
@@ -1487,7 +1517,7 @@ table ip6 openvpn-nat {
# Script to add rules
echo "#!/bin/sh
iptables -t nat -I POSTROUTING 1 -s 10.8.0.0/24 -o $NIC -j MASQUERADE
iptables -t nat -I POSTROUTING 1 -s $VPN_SUBNET/24 -o $NIC -j MASQUERADE
iptables -I INPUT 1 -i tun0 -j ACCEPT
iptables -I FORWARD 1 -i $NIC -o tun0 -j ACCEPT
iptables -I FORWARD 1 -i tun0 -o $NIC -j ACCEPT
@@ -1503,7 +1533,7 @@ ip6tables -I INPUT 1 -i $NIC -p $PROTOCOL --dport $PORT -j ACCEPT" >>/etc/iptabl
# Script to remove rules
echo "#!/bin/sh
iptables -t nat -D POSTROUTING -s 10.8.0.0/24 -o $NIC -j MASQUERADE
iptables -t nat -D POSTROUTING -s $VPN_SUBNET/24 -o $NIC -j MASQUERADE
iptables -D INPUT -i tun0 -j ACCEPT
iptables -D FORWARD -i $NIC -o tun0 -j ACCEPT
iptables -D FORWARD -i tun0 -o $NIC -j ACCEPT
@@ -2173,9 +2203,10 @@ function removeOpenVPN() {
log_header "Remove OpenVPN"
read -rp "Do you really want to remove OpenVPN? [y/n]: " -e -i n REMOVE
if [[ $REMOVE == 'y' ]]; then
# Get OpenVPN port from the configuration
# Get OpenVPN configuration
PORT=$(grep '^port ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
PROTOCOL=$(grep '^proto ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
VPN_SUBNET=$(grep '^server ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
# Stop OpenVPN
log_info "Stopping OpenVPN service..."
@@ -2190,7 +2221,7 @@ function removeOpenVPN() {
# firewalld was used
run_cmd "Removing OpenVPN port from firewalld" firewall-cmd --permanent --remove-port="$PORT/$PROTOCOL"
run_cmd "Removing masquerade from firewalld" firewall-cmd --permanent --remove-masquerade
run_cmd "Removing VPN subnet rule" firewall-cmd --permanent --remove-rich-rule='rule family="ipv4" source address="10.8.0.0/24" accept' 2>/dev/null || true
run_cmd "Removing VPN subnet rule" firewall-cmd --permanent --remove-rich-rule="rule family=\"ipv4\" source address=\"$VPN_SUBNET/24\" accept" 2>/dev/null || true
run_cmd "Removing IPv6 source rule" firewall-cmd --permanent --remove-rich-rule='rule family="ipv6" source address="fd42:42:42:42::/112" accept' 2>/dev/null || true
run_cmd "Reloading firewalld" firewall-cmd --reload
elif [[ -f /etc/nftables/openvpn.nft ]]; then