In light of the recent TunnelVision vulnerability I wanted to share a simple firewall that I wrote for wireguard VPNs.
https://codeberg.org/xabadak/wg-lockdown
If you use a fancy official VPN client from Mullvad, PIA, etc, you won’t need this since most clients already have a kill switch built in (also called Lockdown Mode in Mullvad). This is if you use a barebones wireguard VPN like me, or if your VPN client has a poorly-designed kill switch (like NordVPN, more info here).
A firewall should mitigate the vulnerability, though it does create a side-channel that can be exploited in extremely unlikely circumstances, so a better solution would be to use network namespaces (more info here). Unfortunately I’m a noob and I couldn’t find any scripts or tools to do it that way.
The vulnerability doesn’t work on Linux
You’re still right in 99% of all use cases.
Nobody operates VPNs for privacy in split tunnel. So everyone running Linux that would be concerned about this is unaffected.
I thought TunnelVision applies to all VPN users that don’t use firewall / network namespaces
It doesn’t apply to Linux unless you do split tunnel, which no commercial VPN configs use, because it doesn’t make sense to
Unfortunately Linux is affected https://github.com/leviathansecurity/TunnelVision
TunnelVision appears to work on any operating system that has a DHCP client that implements support for DHCP option 121. Most modern operating systems support this such as Linux, Windows, iOS and MacOS. Notably, Android does not appear to have support for option 121 and remains unaffected.
A fix is available on Linux when configuring the VPN users host to utilize network namespaces.
I read the Arstechnica article too where they say Linux isn’t affected then link to the researchers video where they show Linux being affected…
Oh. It doesn’t work with WireGuard then. It probably works with garbage. Thank you.
I am afraid you are still a bit misled; WireGuard is exactly what they use for the demo video. In general the underlying protocol does not matter, since the vulnerability is about telling the system to direct the packages to the attacker, completely bypassing the VPN.
