vpn killswitch

vans25 · 10-30-2019, 09:41 AM

Hi
Looking for help to correctly setup killswitch after I disconnect from nordvpn (linux app) ( for example if manually disconnected and forget about it or switching to different location etc. becouse killswitch dosn't work in that case/time)
Buildin "killswitch" automatically stops all internet traffic while the VPN connection suddenly fails But it doesn't work if you disconnected manually or connecting to next location (in linux).
also while connected with vpn ,nordvpn diable my ufw and setingup own firewall (but for a time it's connected)

Generally the only way to connect internet must be through nordvpn this is what I'm looking for

How to do it?
Looking for guide how to do it properly
debian10

/dev/random · 11-12-2019, 01:49 PM

Easy, block all packets from all interfaces but the vpns
You need to run this after the vpn is up otherwise it will not work

Code:

#!/bin/sh

iptables -P INPUT DROP
iptables -P OUTPUT DROP

# Allow loopback
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT

# Allow vpn
iptables -A INPUT -i tun0 -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -o tun0 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT

# Allow vpn service though eth0 only (to keep the tunnel established)
iptables -A INPUT -i eth0 -d <vpn ip> -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -o eth0 -s <vpn ip> -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT