mirror of
https://github.com/sshuttle/sshuttle.git
synced 2025-05-01 06:34:53 +02:00
480 lines
20 KiB
Python
480 lines
20 KiB
Python
import os
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import sys
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import ipaddress
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import threading
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from collections import namedtuple
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import socket
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import subprocess
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import re
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from multiprocessing import shared_memory
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import struct
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from functools import wraps
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from enum import IntEnum
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import time
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import traceback
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from sshuttle.methods import BaseMethod
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from sshuttle.helpers import debug3, log, debug1, debug2, Fatal
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try:
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# https://reqrypt.org/windivert-doc.html#divert_iphdr
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import pydivert
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except ImportError:
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raise Exception("Could not import pydivert module. windivert requires https://pypi.org/project/pydivert")
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ConnectionTuple = namedtuple(
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"ConnectionTuple",
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["protocol", "ip_version", "src_addr", "src_port", "dst_addr", "dst_port", "state_epoch", "state"],
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)
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WINDIVERT_MAX_CONNECTIONS = 10_000
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class IPProtocol(IntEnum):
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TCP = socket.IPPROTO_TCP
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UDP = socket.IPPROTO_UDP
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@property
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def filter(self):
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return "tcp" if self == IPProtocol.TCP else "udp"
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class IPFamily(IntEnum):
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IPv4 = socket.AF_INET
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IPv6 = socket.AF_INET6
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@property
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def filter(self):
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return "ip" if self == socket.AF_INET else "ipv6"
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@property
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def version(self):
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return 4 if self == socket.AF_INET else 6
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@property
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def loopback_addr(self):
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return "127.0.0.1" if self == socket.AF_INET else "::1"
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class ConnState(IntEnum):
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TCP_SYN_SENT = 11 # SYN sent
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TCP_ESTABLISHED = 12 # SYN+ACK received
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TCP_FIN_WAIT_1 = 91 # FIN sent
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TCP_CLOSE_WAIT = 92 # FIN received
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@staticmethod
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def can_timeout(state):
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return state in (ConnState.TCP_SYN_SENT, ConnState.TCP_FIN_WAIT_1, ConnState.TCP_CLOSE_WAIT)
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def repr_pkt(p):
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r = f"{p.direction.name} {p.src_addr}:{p.src_port}->{p.dst_addr}:{p.dst_port}"
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if p.tcp:
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t = p.tcp
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r += f" {len(t.payload)}B ("
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r += "+".join(
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f.upper() for f in ("fin", "syn", "rst", "psh", "ack", "urg", "ece", "cwr", "ns") if getattr(t, f)
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)
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r += f") SEQ#{t.seq_num}"
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if t.ack:
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r += f" ACK#{t.ack_num}"
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r += f" WZ={t.window_size}"
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else:
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r += f" {p.udp=} {p.icmpv4=} {p.icmpv6=}"
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return f"<Pkt {r}>"
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def synchronized_method(lock):
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def decorator(method):
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@wraps(method)
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def wrapped(self, *args, **kwargs):
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with getattr(self, lock):
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return method(self, *args, **kwargs)
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return wrapped
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return decorator
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class ConnTrack:
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_instance = None
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def __new__(cls, *args, **kwargs):
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if not cls._instance:
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cls._instance = object.__new__(cls)
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return cls._instance
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raise RuntimeError("ConnTrack can not be instantiated multiple times")
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def __init__(self, name, max_connections=0) -> None:
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self.struct_full_tuple = struct.Struct(">" + "".join(("B", "B", "16s", "H", "16s", "H", "L", "B")))
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self.struct_src_tuple = struct.Struct(">" + "".join(("B", "B", "16s", "H")))
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self.struct_state_tuple = struct.Struct(">" + "".join(("L", "B")))
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try:
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self.max_connections = max_connections
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self.shm_list = shared_memory.ShareableList(
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[bytes(self.struct_full_tuple.size) for _ in range(max_connections)], name=name
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)
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self.is_owner = True
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self.next_slot = 0
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self.used_slots = set()
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self.rlock = threading.RLock()
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except FileExistsError:
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self.is_owner = False
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self.shm_list = shared_memory.ShareableList(name=name)
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self.max_connections = len(self.shm_list)
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debug2(
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f"ConnTrack: is_owner={self.is_owner} entry_size={self.struct_full_tuple.size} shm_name={self.shm_list.shm.name} "
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f"shm_size={self.shm_list.shm.size}B"
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)
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@synchronized_method("rlock")
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def add(self, proto, src_addr, src_port, dst_addr, dst_port, state):
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if not self.is_owner:
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raise RuntimeError("Only owner can mutate ConnTrack")
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if len(self.used_slots) >= self.max_connections:
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raise RuntimeError(f"No slot available in ConnTrack {len(self.used_slots)}/{self.max_connections}")
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if self.get(proto, src_addr, src_port):
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return
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for _ in range(self.max_connections):
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if self.next_slot not in self.used_slots:
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break
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self.next_slot = (self.next_slot + 1) % self.max_connections
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else:
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raise RuntimeError("No slot available in ConnTrack") # should not be here
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src_addr = ipaddress.ip_address(src_addr)
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dst_addr = ipaddress.ip_address(dst_addr)
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assert src_addr.version == dst_addr.version
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ip_version = src_addr.version
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state_epoch = int(time.time())
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entry = (proto, ip_version, src_addr.packed, src_port, dst_addr.packed, dst_port, state_epoch, state)
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packed = self.struct_full_tuple.pack(*entry)
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self.shm_list[self.next_slot] = packed
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self.used_slots.add(self.next_slot)
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proto = IPProtocol(proto)
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debug3(
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f"ConnTrack: added ({proto.name} {src_addr}:{src_port}->{dst_addr}:{dst_port} @{state_epoch}:{state.name}) to "
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f"slot={self.next_slot} | #ActiveConn={len(self.used_slots)}"
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)
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@synchronized_method("rlock")
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def update(self, proto, src_addr, src_port, state):
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if not self.is_owner:
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raise RuntimeError("Only owner can mutate ConnTrack")
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src_addr = ipaddress.ip_address(src_addr)
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packed = self.struct_src_tuple.pack(proto, src_addr.version, src_addr.packed, src_port)
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for i in self.used_slots:
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if self.shm_list[i].startswith(packed):
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state_epoch = int(time.time())
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self.shm_list[i] = self.shm_list[i][:-5] + self.struct_state_tuple.pack(state_epoch, state)
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debug3(
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f"ConnTrack: updated ({proto.name} {src_addr}:{src_port} @{state_epoch}:{state.name}) from slot={i} | "
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f"#ActiveConn={len(self.used_slots)}"
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)
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return self._unpack(self.shm_list[i])
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else:
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debug3(
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f"ConnTrack: ({proto.name} src={src_addr}:{src_port}) is not found to update to {state.name} | "
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f"#ActiveConn={len(self.used_slots)}"
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)
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@synchronized_method("rlock")
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def remove(self, proto, src_addr, src_port):
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if not self.is_owner:
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raise RuntimeError("Only owner can mutate ConnTrack")
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src_addr = ipaddress.ip_address(src_addr)
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packed = self.struct_src_tuple.pack(proto, src_addr.version, src_addr.packed, src_port)
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for i in self.used_slots:
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if self.shm_list[i].startswith(packed):
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conn = self._unpack(self.shm_list[i])
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self.shm_list[i] = b""
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self.used_slots.remove(i)
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debug3(
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f"ConnTrack: removed ({proto.name} src={src_addr}:{src_port} state={conn.state.name}) from slot={i} | "
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f"#ActiveConn={len(self.used_slots)}"
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)
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return conn
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else:
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debug3(
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f"ConnTrack: ({proto.name} src={src_addr}:{src_port}) is not found to remove |"
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f" #ActiveConn={len(self.used_slots)}"
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)
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def get(self, proto, src_addr, src_port):
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src_addr = ipaddress.ip_address(src_addr)
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packed = self.struct_src_tuple.pack(proto, src_addr.version, src_addr.packed, src_port)
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for entry in self.shm_list:
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if entry and entry.startswith(packed):
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return self._unpack(entry)
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@synchronized_method("rlock")
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def gc(self, connection_timeout_sec=15):
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now = int(time.time())
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n = 0
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for i in tuple(self.used_slots):
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state_packed = self.shm_list[i][-5:]
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(state_epoch, state) = self.struct_state_tuple.unpack(state_packed)
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if (now - state_epoch) < connection_timeout_sec:
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continue
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if ConnState.can_timeout(state):
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conn = self._unpack(self.shm_list[i])
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self.shm_list[i] = b""
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self.used_slots.remove(i)
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n += 1
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debug3(
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f"ConnTrack: GC: removed ({conn.protocol.name} src={conn.src_addr}:{conn.src_port} state={conn.state.name})"
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f" from slot={i} | #ActiveConn={len(self.used_slots)}"
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)
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debug3(f"ConnTrack: GC: collected {n} connections | #ActiveConn={len(self.used_slots)}")
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def _unpack(self, packed):
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(
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proto,
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ip_version,
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src_addr_packed,
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src_port,
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dst_addr_packed,
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dst_port,
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state_epoch,
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state,
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) = self.struct_full_tuple.unpack(packed)
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dst_addr = str(ipaddress.ip_address(dst_addr_packed if ip_version == 6 else dst_addr_packed[:4]))
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src_addr = str(ipaddress.ip_address(src_addr_packed if ip_version == 6 else src_addr_packed[:4]))
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return ConnectionTuple(
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IPProtocol(proto), ip_version, src_addr, src_port, dst_addr, dst_port, state_epoch, ConnState(state)
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)
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def __iter__(self):
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def conn_iter():
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for i in self.used_slots:
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yield self._unpack(self.shm_list[i])
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return conn_iter()
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def __repr__(self):
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return f"<ConnTrack(n={len(self.used_slots) if self.is_owner else '?'},cap={len(self.shm_list)},owner={self.is_owner})>"
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class Method(BaseMethod):
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network_config = {}
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proxy_port = None
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proxy_addr = {IPFamily.IPv4: None, IPFamily.IPv6: None}
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def __init__(self, name):
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super().__init__(name)
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def _get_local_proxy_listen_addr(self, port, family):
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proto = "TCPv6" if family.version == 6 else "TCP"
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for line in subprocess.check_output(["netstat", "-a", "-n", "-p", proto]).decode().splitlines():
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try:
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_, local_addr, _, state, *_ = re.split(r"\s+", line.strip())
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except ValueError:
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continue
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port_suffix = ":" + str(port)
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if state == "LISTENING" and local_addr.endswith(port_suffix):
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return ipaddress.ip_address(local_addr[:-len(port_suffix)].strip("[]"))
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raise Fatal("Could not find listening address for {}/{}".format(port, proto))
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def setup_firewall(self, port, dnsport, nslist, family, subnets, udp, user, tmark):
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log(f"{port=}, {dnsport=}, {nslist=}, {family=}, {subnets=}, {udp=}, {user=}, {tmark=}")
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if nslist or user or udp:
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raise NotImplementedError()
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family = IPFamily(family)
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# using loopback proxy address never worked.
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# >>> self.proxy_addr[family] = family.loopback_addr
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# See: https://github.com/basil00/Divert/issues/17#issuecomment-341100167 ,https://github.com/basil00/Divert/issues/82)
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# As a workaround we use another interface ip instead.
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local_addr = self._get_local_proxy_listen_addr(port, family)
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for addr in (ipaddress.ip_address(info[4][0]) for info in socket.getaddrinfo(socket.gethostname(), None)):
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if addr.is_loopback or addr.version != family.version:
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continue
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if local_addr.is_unspecified or local_addr == addr:
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debug2("Found non loopback address to connect to proxy: " + str(addr))
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self.proxy_addr[family] = str(addr)
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break
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else:
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raise Fatal("Windivert method requires proxy to listen on non loopback address")
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self.proxy_port = port
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subnet_addresses = []
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for (_, mask, exclude, network_addr, fport, lport) in subnets:
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if exclude:
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continue
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assert fport == 0, "custom port range not supported"
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assert lport == 0, "custom port range not supported"
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subnet_addresses.append("%s/%s" % (network_addr, mask))
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self.network_config[family] = {
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"subnets": subnet_addresses,
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"nslist": nslist,
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}
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def wait_for_firewall_ready(self):
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debug2(f"network_config={self.network_config} proxy_addr={self.proxy_addr}")
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self.conntrack = ConnTrack(f"sshuttle-windivert-{os.getppid()}", WINDIVERT_MAX_CONNECTIONS)
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methods = (self._egress_divert, self._ingress_divert, self._connection_gc)
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ready_events = []
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for fn in methods:
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ev = threading.Event()
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ready_events.append(ev)
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def _target():
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try:
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fn(ev.set)
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except Exception:
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debug2(f"thread {fn.__name__} exiting due to: " + traceback.format_exc())
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sys.stdin.close() # this will exist main thread
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sys.stdout.close()
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threading.Thread(name=fn.__name__, target=_target, daemon=True).start()
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for ev in ready_events:
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if not ev.wait(5): # at most 5 sec
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raise Fatal("timeout in wait_for_firewall_ready()")
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def restore_firewall(self, port, family, udp, user):
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pass
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def get_supported_features(self):
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result = super(Method, self).get_supported_features()
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result.loopback_port = False
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result.user = False
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result.dns = False
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result.ipv6 = False
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return result
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def get_tcp_dstip(self, sock):
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if not hasattr(self, "conntrack"):
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self.conntrack = ConnTrack(f"sshuttle-windivert-{os.getpid()}")
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src_addr, src_port = sock.getpeername()
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c = self.conntrack.get(IPProtocol.TCP, src_addr, src_port)
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if not c:
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return (src_addr, src_port)
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return (c.dst_addr, c.dst_port)
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def is_supported(self):
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if sys.platform == "win32":
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return True
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return False
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def _egress_divert(self, ready_cb):
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proto = IPProtocol.TCP
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filter = f"outbound and {proto.filter}"
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# with pydivert.WinDivert(f"outbound and tcp and ip.DstAddr == {subnet}") as w:
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family_filters = []
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for af, c in self.network_config.items():
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subnet_filters = []
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for cidr in c["subnets"]:
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ip_network = ipaddress.ip_network(cidr)
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first_ip = ip_network.network_address
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last_ip = ip_network.broadcast_address
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subnet_filters.append(f"(ip.DstAddr>={first_ip} and ip.DstAddr<={last_ip})")
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family_filters.append(f"{af.filter} and ({' or '.join(subnet_filters)}) ")
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filter = f"{filter} and ({' or '.join(family_filters)})"
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debug1(f"[OUTBOUND] {filter=}")
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with pydivert.WinDivert(filter) as w:
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ready_cb()
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proxy_port = self.proxy_port
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proxy_addr_ipv4 = self.proxy_addr[IPFamily.IPv4]
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proxy_addr_ipv6 = self.proxy_addr[IPFamily.IPv6]
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for pkt in w:
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debug3(">>> " + repr_pkt(pkt))
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if pkt.tcp.syn and not pkt.tcp.ack:
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# SYN sent (start of 3-way handshake connection establishment from our side, we wait for SYN+ACK)
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self.conntrack.add(
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socket.IPPROTO_TCP,
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pkt.src_addr,
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pkt.src_port,
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pkt.dst_addr,
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pkt.dst_port,
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ConnState.TCP_SYN_SENT,
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)
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if pkt.tcp.fin:
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# FIN sent (start of graceful close our side, and we wait for ACK)
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self.conntrack.update(IPProtocol.TCP, pkt.src_addr, pkt.src_port, ConnState.TCP_FIN_WAIT_1)
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if pkt.tcp.rst:
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# RST sent (initiate abrupt connection teardown from our side, so we don't expect any reply)
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self.conntrack.remove(IPProtocol.TCP, pkt.src_addr, pkt.src_port)
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# DNAT
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if pkt.ipv4 and proxy_addr_ipv4:
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pkt.dst_addr = proxy_addr_ipv4
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if pkt.ipv6 and proxy_addr_ipv6:
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pkt.dst_addr = proxy_addr_ipv6
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pkt.tcp.dst_port = proxy_port
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# XXX: If we set loopback proxy address (DNAT), then we should do SNAT as well
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# by setting src_addr to loopback address.
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# Otherwise injecting packet will be ignored by Windows network stack
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# as they packet has to cross public to private address space.
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# See: https://github.com/basil00/Divert/issues/82
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# Managing SNAT is more trickier, as we have to restore the original source IP address for reply packets.
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# >>> pkt.dst_addr = proxy_addr_ipv4
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w.send(pkt, recalculate_checksum=True)
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def _ingress_divert(self, ready_cb):
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proto = IPProtocol.TCP
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direction = "inbound" # only when proxy address is not loopback address (Useful for testing)
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ip_filters = []
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for addr in (ipaddress.ip_address(a) for a in self.proxy_addr.values() if a):
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if addr.is_loopback: # Windivert treats all loopback traffic as outbound
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direction = "outbound"
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if addr.version == 4:
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ip_filters.append(f"ip.SrcAddr=={addr}")
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else:
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# ip_checks.append(f"ip.SrcAddr=={hex(int(addr))}") # only Windivert >=2 supports this
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ip_filters.append(f"ipv6.SrcAddr=={addr}")
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if not ip_filters:
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raise Fatal("At least ipv4 or ipv6 address is expected")
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|
filter = f"{direction} and {proto.filter} and ({' or '.join(ip_filters)}) and tcp.SrcPort=={self.proxy_port}"
|
|
debug1(f"[INGRESS] {filter=}")
|
|
with pydivert.WinDivert(filter) as w:
|
|
ready_cb()
|
|
for pkt in w:
|
|
debug3("<<< " + repr_pkt(pkt))
|
|
if pkt.tcp.syn and pkt.tcp.ack:
|
|
# SYN+ACK received (connection established)
|
|
conn = self.conntrack.update(IPProtocol.TCP, pkt.dst_addr, pkt.dst_port, ConnState.TCP_ESTABLISHED)
|
|
elif pkt.tcp.rst:
|
|
# RST received - Abrupt connection teardown initiated by otherside. We don't expect anymore packets
|
|
conn = self.conntrack.remove(IPProtocol.TCP, pkt.dst_addr, pkt.dst_port)
|
|
# https://wiki.wireshark.org/TCP-4-times-close.md
|
|
elif pkt.tcp.fin and pkt.tcp.ack:
|
|
# FIN+ACK received (Passive close by otherside. We don't expect any more packets. Otherside expects an ACK)
|
|
conn = self.conntrack.remove(IPProtocol.TCP, pkt.dst_addr, pkt.dst_port)
|
|
elif pkt.tcp.fin:
|
|
# FIN received (Otherside initiated graceful close. We expects a final ACK for a FIN packet)
|
|
conn = self.conntrack.update(IPProtocol.TCP, pkt.dst_addr, pkt.dst_port, ConnState.TCP_CLOSE_WAIT)
|
|
else:
|
|
conn = self.conntrack.get(socket.IPPROTO_TCP, pkt.dst_addr, pkt.dst_port)
|
|
if not conn:
|
|
debug2("Unexpected packet: " + repr_pkt(pkt))
|
|
continue
|
|
pkt.src_addr = conn.dst_addr
|
|
pkt.tcp.src_port = conn.dst_port
|
|
w.send(pkt, recalculate_checksum=True)
|
|
|
|
def _connection_gc(self, ready_cb):
|
|
ready_cb()
|
|
while True:
|
|
time.sleep(5)
|
|
self.conntrack.gc()
|