Up first is a clever attack against VPNs, using some clever DNS and routing tricks. The technique is known as TunnelCrack (PDF), and every VPN tested was vulnerable to one of the two attacks, on at…
The mitigation is to disable local network access while the VPN is connected. Many clients do this, at least on some platforms. It was interesting to see that on iOS every tested app was vulnerable to this data leaking attack, and nearly every one of them on the macOS. It appears that the iOS API for working with VPNs has only recently introduced a control for how to handle local network traffic, leading to the abysmal results.
Not surprised mac OS sucks at this but is Linux vulnerable as well?
This isn’t exactly a platform specific problem because having local network access while using a VPN is actually a feature called “split-tunnelling”. The tunnelcrack issue goes beyond this but can be mitigated by using full tunnel VPN that resolves the server by IP address instead of DNS.
You are right, it’s very simple. Traffic will go wherever is shortest by default, because that’s just how networking works on your pc. Shut off the shortest path (or every other path) and it’s forced through your VPN connection.
Not surprised mac OS sucks at this but is Linux vulnerable as well?
This isn’t exactly a platform specific problem because having local network access while using a VPN is actually a feature called “split-tunnelling”. The tunnelcrack issue goes beyond this but can be mitigated by using full tunnel VPN that resolves the server by IP address instead of DNS.
as long as you have a firewall via iptables or something similar forcing everything through the VPN only, you should be fine I would think.
if not I’ll have to change my configs a lot lol.
You are right, it’s very simple. Traffic will go wherever is shortest by default, because that’s just how networking works on your pc. Shut off the shortest path (or every other path) and it’s forced through your VPN connection.
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