From fdc2bfbdace91a8e456f9623c0d9215978f7d888 Mon Sep 17 00:00:00 2001
From: Nyr <me@nyr.be>
Date: Fri, 8 Jun 2018 17:46:09 +0200
Subject: [PATCH] Improve iptables configuration

See #464.
---
 openvpn-install.sh | 32 +++++++++++---------------------
 1 file changed, 11 insertions(+), 21 deletions(-)

diff --git a/openvpn-install.sh b/openvpn-install.sh
index 403e0fd..2b26c7e 100644
--- a/openvpn-install.sh
+++ b/openvpn-install.sh
@@ -25,11 +25,9 @@ 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
@@ -133,16 +131,12 @@ if [[ -e /etc/openvpn/server.conf ]]; then
 					firewall-cmd --direct --remove-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 --remove-rule ipv4 nat POSTROUTING 0 -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $IP
 				else
-					IP=$(grep 'iptables -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to ' $RCLOCAL | cut -d " " -f 14)
+					IP=$(grep 'iptables -t nat -C POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to ' /etc/openvpn/iptables-init | cut -d " " -f 14)
 					iptables -t nat -D POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $IP
-					sed -i '/iptables -t nat -A POSTROUTING -s 10.8.0.0\/24 ! -d 10.8.0.0\/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 10.8.0.0/24 -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 10.8.0.0\/24 -j ACCEPT/d" $RCLOCAL
-						sed -i "/iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT/d" $RCLOCAL
 					fi
 				fi
 				if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing" && [[ "$PORT" != '1194' ]]; then
@@ -321,26 +315,22 @@ crl-verify crl.pem" >> /etc/openvpn/server.conf
 		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 $IP
 	else
-		# Needed to use rc.local with some systemd distros
-		if [[ "$OS" = 'debian' && ! -e $RCLOCAL ]]; then
-			echo '#!/bin/sh -e
-exit 0' > $RCLOCAL
-		fi
-		chmod +x $RCLOCAL
 		# Set NAT for the VPN subnet
-		iptables -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $IP
-		sed -i "1 a\iptables -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $IP" $RCLOCAL
+		# iptables-init checks if the rules already exist, so duplicates aren't
+		# added when iptables-init is called after an OpenVPN service restart.
+		echo '#!/bin/bash' > /etc/openvpn/iptables-init
+echo "iptables -t nat -C POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $IP || iptables -t nat -A POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to $IP" >> /etc/openvpn/iptables-init
 		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 10.8.0.0/24 -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 10.8.0.0/24 -j ACCEPT" $RCLOCAL
-			sed -i "1 a\iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" $RCLOCAL
+			echo "iptables -C INPUT -p $PROTOCOL --dport $PORT -j ACCEPT || iptables -I INPUT -p $PROTOCOL --dport $PORT -j ACCEPT
+iptables -C FORWARD -s 10.8.0.0/24 -j ACCEPT || iptables -I FORWARD -s 10.8.0.0/24 -j ACCEPT
+iptables -C FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT || iptables -I FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT" >> /etc/openvpn/iptables-init
 		fi
+		chmod +x /etc/openvpn/iptables-init
+		echo "script-security 2
+up /etc/openvpn/iptables-init" >> /etc/openvpn/server.conf
 	fi
 	# If SELinux is enabled and a custom port was selected, we need this
 	if sestatus 2>/dev/null | grep "Current mode" | grep -q "enforcing" && [[ "$PORT" != '1194' ]]; then