I am trying to execute an attack that requires a full-duplex MiTM position. This is the reason why I choose to use Ettercap. I have picked DHCP spoofing as the attack of choice.
The problem that I am facing is that Ettercap executes the attack as half-duplex, meaning that I can only intercept messages coming from the client. I also want to intercept the messages coming the other way i.e. I need a full-duplex MiTM.
From what I understand, Ettercap acts as a gateway router in this scenario. The client thinks that I am the gateway so it sends me a request whose destination is not on the subnetwork, expecting that I will forward the layer 3 packet appropriately. Ettercap does this. However, when the response is received by the actual gateway router, it sends it immediately to the client (victim) because that is where the request packet originated from (source IP). This is shown in Figure 1.
What I basically want is to stop Ettercap from doing anything after the initial DHCP spoofing attack. Then I will add my own script that will make the same request as the client did, effectively acting like a forward proxy. This way, when the response is received by the actual gateway router, it will be sent to me. Then I can change things as I like and forward the changed response to the client. This is shown in Figure 2.
I hope that everyone understands what I meant to say. Does anyone know how this can be achieved?
Thank you! Cheers.