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A transparent proxy prototype using tproxy written in python3 & trio
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| #!/usr/bin/env python3 | |
| import sys | |
| import traceback | |
| import trio | |
| import trio.socket as socket | |
| import struct | |
| """ | |
| ip rule add fwmark 0x1 lookup 100 | |
| ip route add local default dev lo table 100 | |
| iptables -t mangle -A OUTPUT -p udp -m mark --mark 0x42 -j RETURN | |
| iptables -t mangle -A OUTPUT -p udp -j MARK --set-mark 0x1 | |
| iptables -t mangle -A PREROUTING -p udp -m mark --mark 0x1 -j TPROXY --on-port=8881 --on-ip=127.0.0.1 | |
| """ | |
| IP_TRANSPARENT = 19 | |
| IP_ORIGDSTADDR = 20 | |
| IP_RECVORIGDSTADDR = IP_ORIGDSTADDR | |
| SO_MARK = 36 | |
| socket_table = {} | |
| def get_dst(ancdata): | |
| dstip = None | |
| for cmsg_level, cmsg_type, cmsg_data in ancdata: | |
| if cmsg_level == socket.SOL_IP and cmsg_type == IP_ORIGDSTADDR: | |
| family, port = struct.unpack('=HH', cmsg_data[0:4]) | |
| port = socket.htons(port) | |
| if family == socket.AF_INET: | |
| start = 4 | |
| length = 4 | |
| ip = socket.inet_ntop(family, cmsg_data[start:start + length]) | |
| dstip = (ip, port) | |
| break | |
| return dstip | |
| def creat_socket_tuple(srcip, dstip): | |
| remote = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) | |
| remote.setsockopt(socket.SOL_SOCKET, SO_MARK, 0x42) | |
| local = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) | |
| local.setsockopt(socket.IPPROTO_IP, IP_TRANSPARENT, 1) | |
| local.setsockopt(socket.SOL_SOCKET, SO_MARK, 0x42) | |
| ev = trio.Event() | |
| socket_table[(srcip, dstip)] = (local, remote, ev) | |
| return (local, remote, ev) | |
| def get_socket_tuple(srcip, dstip): | |
| socket_tuple = socket_table.get((srcip, dstip)) | |
| if socket_tuple: | |
| return (socket_tuple, False) | |
| return (creat_socket_tuple(srcip, dstip), True) | |
| async def inbound_loop(local, remote, srcip, cancel_scope): | |
| while True: | |
| response, dstip = await remote.recvfrom(4096) | |
| print("[ ] Got response from remote udp://%s:%d" % (dstip[0], dstip[1])) | |
| await local.sendto(response, srcip) | |
| cancel_scope.deadline = trio.current_time() + 30 | |
| async def outbound_loop(event, cancel_scope): | |
| while True: | |
| await event.wait() | |
| event.clear(); | |
| cancel_scope.deadline = trio.current_time() + 30 | |
| async def proxy_data(srcip, dstip, data): | |
| socket_tuple, new = get_socket_tuple(srcip, dstip) | |
| local, remote, ev = socket_tuple | |
| await remote.sendto(data, dstip) | |
| ev.set() #keep alive | |
| if not new: | |
| print("[ ] existing connection") | |
| return | |
| print("[ ] new connection") | |
| try: | |
| await local.bind(dstip) | |
| async with trio.open_nursery() as nursery: | |
| cancel_scope = nursery.cancel_scope | |
| nursery.start_soon(inbound_loop, local, remote, srcip, cancel_scope) | |
| nursery.start_soon(outbound_loop, ev, cancel_scope) | |
| if nursery.cancel_scope.cancelled_caught: | |
| #timeout | |
| print("[-] Timeout for udp://%s:%d" %(dstip[0], dstip[1])) | |
| except: | |
| print("[*] Unexpected error:", sys.exc_info()[0]) | |
| traceback.print_exc() | |
| finally: | |
| local.close() | |
| remote.close() | |
| del socket_table[(srcip, dstip)] | |
| async def main(): | |
| s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) | |
| s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) | |
| s.setsockopt(socket.SOL_IP, IP_RECVORIGDSTADDR, 1) | |
| s.setsockopt(socket.IPPROTO_IP, IP_TRANSPARENT, 1) | |
| await s.bind(('127.0.0.1', 8881)) | |
| print("[+] Bound to udp://127.0.0.1:8881") | |
| async with trio.open_nursery() as nursery: | |
| while True: | |
| data, ancdata, _, srcip = await s.recvmsg(4096, socket.CMSG_SPACE(24)) | |
| dstip = get_dst(ancdata) | |
| if dstip: | |
| print("[ ] Connection from udp://%s:%d to udp://%s:%d" % (srcip[0], srcip[1], dstip[0], dstip[1])) | |
| nursery.start_soon(proxy_data, srcip, dstip, data) | |
| else: | |
| print("[*] Failed to get original dest address") | |
| if __name__ == "__main__": | |
| trio.run(main) |
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