What is rdp2tcp and how does it enable port forwarding over RDP?

rdp2tcp utilizes RDP's virtual channel functionality to multiplex TCP connections. It supports forward and reverse port forwarding, SOCKS5 proxy, and stdin/stdout forwarding. The client-side binary (rdp2tcp) runs on the attacker's machine, while the server-side binary (rdp2tcp64.exe) executes on the target RDP server. After connecting with a patched version of xfreerdp that supports the `/rdp2tcp` option, the attacker can add port forwarding rules to tunnel arbitrary traffic through the RDP session.