Resolve "Create a "fake ssh" binary for proxies"

Sets the changes for #48 (closed) to await approval of #34 (closed)

scripts/defense/wanssh.src

+// Must be renamed as "ssh" and installed on machines not meant to have LAN redirection capability
+// In particular, public proxies for the "ssh rental" missions
+if params.len < 2 or params.len > 3 then exit(command_info("ssh_usage"))
+
+// Only modification : blocking LAN adresses
+if active_user != "root" and is_lan_ip(params[1]) then exit("Access refused: this server is intended as a WAN proxy")
+
+credentials = params[0].split("@")
+user = credentials[0]
+password = credentials[1]
+
+port = 22
+// params is a list of strings, so you have to convert it to integer, which is what connect_service accepts
+if params.len == 3 then port = params[2].to_int
+if typeof(port) != "number" then exit("Invalid port: " + port)
+print("Connecting...")
+
+shell = get_shell.connect_service(params[1], port, user, password, "ssh")
+if shell then shell.start_terminal
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