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Problem Statment

I am trying to guard against the following scenario.

I have a laptop and it connects over wifi, at home as well as at the workplace.

I am not familiar with the wifi protocol.

I however have some understanding of how it may happen - there is some sort of a device-identifier (I am guessing it looks like a mac-address 'AB:01:CD:23'....) and a user-identifer (Alice_and_Bob_Wifi) that is broadcast. I have configured the SSID's in my laptop.

The understanding is as follows -

As soon as my laptop comes within range, it matches (likely the machine identifier), recognizes it and initiates a protocol (wifi-authentication-protocol-version-x.y.z ??) to connect to the wifi router.

To do that it sends out a password.

Wifi verifies the passwords and lets the client (my-laptop) 'in' (establishes a connection).

My questions:

a) Are both user-identifier (Alice_and_Bob_Wifi) and device-identifier (AB:01:CD:23) broadcast?

b) Is there any secret (like ssh-certificate) that is exchanged during the first handshake that would help guard against an evil twin attack?

c) When my laptop thinks that the rogue router is the legitimate one, it would send out the password to authenticate itself. Does the rogue router acknowledge it and gain knowledge of the password? (or is only a hash of the password sent, to guard against the actual password being revealed in such cases)?

d) If the actual password is transmitted instead of a hash, then would the hacker now be able to login to the legitimate router and use the network masquerading as that router's owner?

e) Is there any equivalent to TLS handshake that happens during wifi connection handshake such that the transmitted password is over an encrypted channel rather than broadcast in clear?

References

  1. How would you detect an Evil Twin attack, especially in a new environment?
  2. https://searchsecurity.techtarget.com/definition/evil-twin
  3. https://null-byte.wonderhowto.com/how-to/hack-wi-fi-creating-evil-twin-wireless-access-point-eavesdrop-data-0147919/
  4. How to mitigate evil twin WIFI social engineering attack?
  5. https://null-byte.wonderhowto.com/how-to/hack-wi-fi-capturing-wpa-passwords-by-targeting-users-with-fluxion-attack-0176134/

1 Answer 1

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a) Are both user-identifier and device-identifier broadcast?

When connecting to a wireless network, a client usually only looks for the ESSID (user-identifier). The way access points work is by advertising the ESSID in a wireless packet, this packet also contains the source MAC (device-identifier). While some clients will look at both the ESSID and the MAC address, most clients will already attempt to connect when the ESSID is the same. While this may seem like a security flaw, this can actually be very useful in a scenario where multiple AP's are used, for example in a mesh network as this allows for seamless roaming between AP's (which should all have different MAC addresses).

b) Is there any secret that is exchanged during the first handshake that would help guard against an evil twin attack?

During an evil twin attack, the attacker will sever the connection between AP and STATION (wireless client), the STATION will automatically attempt to reconnect to a network with the expected ESSID (e.g. Alice_and_Bob_Wifi) and will try to connect to either the real AP or the evil twin if the same ESSID is set.

c,d) When my laptop thinks that the rogue router is the legimate one, it would send out the password to authenticate itself. Does the rogue router simply acknowledge it and gain knowledge of the password? If the actual password is transmitted instead of a hash, then would the hacker now be able to login to the legitimate router and use the network masquerading as that router's owner?

During the WPA handshake the password to the wireless network (or a hashed version) is never transmitted. A functional evil twin will always need to possess the wireless password beforehand or the victim won't be able to properly connect to the evil twin. The link below explains in great detail how exactly the 4-way handshake works.

https://networklessons.com/cisco/ccnp-encor-350-401/wpa-and-wpa2-4-way-handshake

If the WiFi passwords entered by STATION and AP don't match the calculated encryption keys won't match and communication won't be possible. This is due to the fact that the encryption keys are calculated using the password among other factors.

The danger that an evil twin attack poses is by getting in between the victim and the real AP, this allows for follow-up attacks like e.g. DNS spoofing or eavesdropping on unencrypted connections.

e) Is there any equivalent to TLS handshake that happens during wifi connection handshake such that the transmitted password is over encrypted channel rather than broadcast in clear?

As said before the password is never transmitted. Tampering with the 4-way handshake is prevented by sending a Message Integrity Check (MIC) in the 3rd and 4th message of the handshake. This number is used to verify the origin of the packet and prevents an attacker from sending a fake 3rd or 4th message.

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