Multiple users sharing the same IP

Question

I'm setting up a quite unusual proxy for a very specific niche case.

I'm allocating (ip,port) addresses to users, from which they can send and receive UDP and TCP packets.

e.g. say someone is allocated 1.2.3.4:50000, they can then send packets from that address and receive packets to that address.

Another person might be allocated 1.2.3.4:80, from which they can then send and receive packets.

Assuming our implementation is sound, and we allocate on IPs we control and ports > 0, are there any security liabilities here?

I know NAT is very similar indeed. I'm wondering as the user will be able to see and choose which of available IPs and port combinations to use, and thus there could be different potentially malicious users with access to port 25, 80, 443, etc, whether this breaks the assumptions of any important protocol.

Answer 1

I dont fully understand your question. Are you trying to limit users using particular IP and port? In the real world we use random ports to connect to the target server port, i.e. you are using 65311 port to connect to google.com 80 port. So if you want to block the user's connection port from connecting to outside is quite usual. However you can still use NAT to limit what port can pass through the router from internal to external.

Moreover, you can assign MAC address to certain IP otherwise unauthorised or unset MAC address has no right to connect to outside.