Packet Interception(?)

theoretical question.

There is a client and a server (on a TCP internet connection of coarse). The client is constantly recieving packets from the server. Packets are systematically sent back to the server with keyboard and mouse input into the client.

What i would like to setup is automated packet responses, eliminating user input. To do this though..? I have a few ideas on how it might be done but I do not know the right solution. Assuming I don't have the code for the client, how could this be achieved?

Thanks guys.

Maybe I'm missing something here. But can't you just set up an infinite loop on the client to automatically respond to the server? I have done this many times to "stress test" C/S apps. Are you trying to emulate keyboard and mouse movement as input to be sent to the server?

Bob

Welcome to the forums!

1. Monitor client output with Ethereal.
2. Emulate with a socket.

two different ways Ive done packet filtering in the past, the harder way (but better way) is to write an NDIS filter driver. Don't count on getting much good info on doing this here, or anywhere for that matter. The easier way is to write an LSP (Layered Service Provider), you can use that to filter all winsock calls. It's still a pretty complicated process, but it's all done in user mode. You can only filter things that go through winsock so this will limit you to TCP/IP, it won't filter things like IPX/SPX, but who the hell uses that anymore anyway???

Since your subject says packet interception, I'm assuming you want a 3rd host to get the packets and reply. You can use the pcap library to capture the packets in promiscuous mode. The library supports filtering too so you can get just the packets you need.

Once you've got a request, you can create a RAW socket, create your own IP header to use the IP of the actual client, build the TCP header, attach the payload and send the 'automated' keyboard and mouse values. :p

cool.. this is good stuff. i'll need to do some background work but i've got my head around it thanks! one more question though. say you build or modify outgoing packets.. this is good but at the same time i want the client to react. like moving the coordinace of a sprite in an online game. i want the client and server both react to the automation.


do you know what i mean?

yea, sounds like your trying to cheat to me, but then again, thats me.