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Just to clarify a question I had when reading about KRACK - If you are using a VPN over WiFi, you still have some degree of safety, right? Any way that the KRA

Just to clarify a question I had when reading about KRACK - If you are using a VPN over WiFi, you still have some degree of safety, right? Any way that the KRACK vulnerability can be elevated to sniff and decrypt VPN packets in transit?

wskinner 9y ago
Yes. It appears that since KRACK can allow the attacker to hijack a TCP handshake that they could potentially downgrade an HTTPS connection where HSTS is not used, but that shouldn’t affect your VPN connection.
- iancarroll 9y ago
  To be clear, if a client makes an HTTPS request, you cannot downgrade it to HTTP, even if you're in control of the TCP socket. You can only hijack connections that are initially made over HTTP.
  - wskinner 9y ago
    In fact, you can, using sslstrip. It was demonstrated in the video, as well as in this article: https://arstechnica.com/information-technology/2017/10/severe-flaw-in-wpa2-protocol-leaves-wi-fi-traffic-open-to-eavesdropping/ https://arstechnica.com/information-technology/2017/10/sever.... I think this will only work against android/linux clients, since in that case the attacker actually knows the key, and can perform a proper MITM.
    - iancarroll 9y ago
      You cannot. sslstrip exists to attempt to work around the fact you can't directly downgrade HTTPS to HTTP. In that video, because HSTS isn't used on match.com (unfortunate), the browser doesn't attempt to make an HTTPS connection at first. Obviously, if you have control of that TCP connection, you can do whatever you want. The browser is oblivious to HTTPS existing. Also, be careful not to confuse the layers here. The encryption algorithms in WPA2 are completely unrelated to TLS/HTTPS. TLS is... somewhere in the OSI model, but it's well above WPA2/packet handling, and TLS can/does work with a compromised network.
manfredo 9y ago
A properly working VPN should still maintain privacy even if an attacker is in complete control of your modem. The data is encrypted from your device all the way to a VPN server. Conceivably, they could redirect traffic to an alternative malicious VPN but that should fail authentication. (somebody let me know if I'm wrong in this)
- ktta 9y ago
  You are right, but only for the perfect 'VPN'. There are also many insecure VPNs out there, which don't cover all your bases (for ex: VPNs that don't tunnel DNS requests through the VPN is a common mistake) So while there are VPNs with great security, you have to make sure your VPN is not vulnerable to common MITM attacks. So choose your VPN which has been well vetted. I'm a fan of OpenVPN due to it being able to pass as HTTPS traffic, but a popular recommendation is algo which is IKEv2 based IPSec VPN. https://github.com/trailofbits/algo https://github.com/trailofbits/algo

wskinner 9y ago

Yes. It appears that since KRACK can allow the attacker to hijack a TCP handshake that they could potentially downgrade an HTTPS connection where HSTS is not used, but that shouldn’t affect your VPN connection.

iancarroll 9y ago
To be clear, if a client makes an HTTPS request, you cannot downgrade it to HTTP, even if you're in control of the TCP socket. You can only hijack connections that are initially made over HTTP.
- wskinner 9y ago
  In fact, you can, using sslstrip. It was demonstrated in the video, as well as in this article: https://arstechnica.com/information-technology/2017/10/severe-flaw-in-wpa2-protocol-leaves-wi-fi-traffic-open-to-eavesdropping/ https://arstechnica.com/information-technology/2017/10/sever.... I think this will only work against android/linux clients, since in that case the attacker actually knows the key, and can perform a proper MITM.
  - iancarroll 9y ago
    You cannot. sslstrip exists to attempt to work around the fact you can't directly downgrade HTTPS to HTTP. In that video, because HSTS isn't used on match.com (unfortunate), the browser doesn't attempt to make an HTTPS connection at first. Obviously, if you have control of that TCP connection, you can do whatever you want. The browser is oblivious to HTTPS existing. Also, be careful not to confuse the layers here. The encryption algorithms in WPA2 are completely unrelated to TLS/HTTPS. TLS is... somewhere in the OSI model, but it's well above WPA2/packet handling, and TLS can/does work with a compromised network.

manfredo 9y ago

A properly working VPN should still maintain privacy even if an attacker is in complete control of your modem. The data is encrypted from your device all the way to a VPN server. Conceivably, they could redirect traffic to an alternative malicious VPN but that should fail authentication. (somebody let me know if I'm wrong in this)

ktta 9y ago
You are right, but only for the perfect 'VPN'. There are also many insecure VPNs out there, which don't cover all your bases (for ex: VPNs that don't tunnel DNS requests through the VPN is a common mistake) So while there are VPNs with great security, you have to make sure your VPN is not vulnerable to common MITM attacks. So choose your VPN which has been well vetted. I'm a fan of OpenVPN due to it being able to pass as HTTPS traffic, but a popular recommendation is algo which is IKEv2 based IPSec VPN. https://github.com/trailofbits/algo https://github.com/trailofbits/algo