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Novel attack against virtually all VPN apps neuters their entire purpose (arstechnica.com)

submitted 7 months ago by jeffw to c/technology

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[–] [email protected] 17 points 7 months ago* (last edited 7 months ago) (2 children)

If i get this right, that attack only works before the tunnel is initiated (i.e. traffic encrypted), if the hosts is compromised, right? No danger from untrusted points inbetween, right?

[–] [email protected] 22 points 7 months ago (1 children)

This technique can also be used against an already established VPN connection once the VPN user’s host needs to renew a lease from our DHCP server. We can artificially create that scenario by setting a short lease time in the DHCP lease, so the user updates their routing table more frequently. In addition, the VPN control channel is still intact because it already uses the physical interface for its communication. In our testing, the VPN always continued to report as connected, and the kill switch was never engaged to drop our VPN connection.

Sounds to me like it totally works even after the tunnel has started.

[–] [email protected] 2 points 6 months ago (1 children)

Yeah, it's like a fake traffic cop basically, sending your (network) traffic down the wrong route

[–] [email protected] 1 points 6 months ago (1 children)

More like a corrupt traffic cop. There are reasons you might want this kind of functionality, which is why it exists. Normally you can trust the cop (DHCP server) but in this case the cop has decided to send everyone from all streets down to the docks.

[–] [email protected] 1 points 6 months ago (1 children)

These types of attacks would likely be implemented via DHCP spoofing / poisoning, unless you're on a malicious network

[–] [email protected] 1 points 6 months ago

I’d think the place most people use VPN is public wifi, unless they are utilizing workplace VPN.

[–] DreamlandLividity 13 points 6 months ago* (last edited 6 months ago) (2 children)

No, it works at any point and the local network needs to be compromised (untrusted), the host can be secure.

So it is likely not an issue at your home unless you have weak Wi-Fi password. But on any public/untrusted Wi-Fi, it is an issue.

[–] [email protected] 2 points 6 months ago (1 children)

Yikes

[–] DreamlandLividity 2 points 6 months ago* (last edited 6 months ago)

That being said, it apparently does not affect Mullvad apps on any platform other than iOS (Apple does not allow fixing it on iOS). I suspect other serious VPNs are also not vulnerable outside iOS, since it is prevented by simple leak prevention mechanism.