mirror of
https://github.com/sshuttle/sshuttle.git
synced 2025-07-08 02:27:27 +02:00
534 lines
23 KiB
Python
534 lines
23 KiB
Python
import os
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import sys
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from ipaddress import ip_address, ip_network
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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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from struct 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 log, debug3, debug1, debug2, get_verbose_level, Fatal
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try:
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# https://reqrypt.org/windivert-doc.html#divert_iphdr
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# https://www.reqrypt.org/windivert-changelog.txt
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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 = int(os.environ.get('WINDIVERT_MAX_CONNECTIONS', 1024))
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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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@staticmethod
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def from_ip_version(version):
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return IPFamily.IPv6 if version == 4 else IPFamily.IPv4
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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 ip_address("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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try:
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direction = p.direction.name
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if p.is_loopback:
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direction += "/lo"
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except AttributeError: # windiver > 2.0
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direction = 'OUT' if p.address.Outbound == 1 else 'IN'
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if p.address.Loopback == 1:
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direction += '/lo'
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r = f"{direction} {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(">" + "".join(("B", "B", "16s", "H", "16s", "H", "L", "B")))
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self.struct_src_tuple = Struct(">" + "".join(("B", "B", "16s", "H")))
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self.struct_state_tuple = 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} cap={len(self.shm_list)} item_sz={self.struct_full_tuple.size}B"
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f"shm_name={self.shm_list.shm.name} shm_sz={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 = ip_address(src_addr)
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dst_addr = 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 = 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 = 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 = 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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def dump(self):
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for entry in self.shm_list:
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if not entry:
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continue
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conn = self._unpack(entry)
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proto, ip_version, src_addr, src_port, dst_addr, dst_port, state_epoch, state = conn
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log(f"{proto.name}/{ip_version} {src_addr}:{src_port} -> {dst_addr}:{dst_port} {state.name}@{state_epoch}")
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@synchronized_method("rlock")
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def gc(self, connection_timeout_sec=15):
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# self.dump()
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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 = ip_address(dst_addr_packed if ip_version == 6 else dst_addr_packed[:4]).exploded
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src_addr = ip_address(src_addr_packed if ip_version == 6 else src_addr_packed[:4]).exploded
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proto = IPProtocol(proto)
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state = ConnState(state)
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return ConnectionTuple(proto, ip_version, src_addr, src_port, dst_addr, dst_port, state_epoch, state)
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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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def __init__(self, name):
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super().__init__(name)
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def _get_bind_address_for_port(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(errors='ignore').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 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, proxy_port, dnsport, nslist, family, subnets, udp, user, group, tmark):
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debug2(f"{proxy_port=}, {dnsport=}, {nslist=}, {family=}, {subnets=}, {udp=}, {user=}, {group=} {tmark=}")
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if nslist or user or udp or group:
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raise NotImplementedError("user, group, nslist, udp are not supported")
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family = IPFamily(family)
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proxy_ip = None
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# using loopback only proxy binding won't work with windivert.
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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, finding another interface ip instead. (client should not bind proxy to loopback address)
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proxy_bind_addr = self._get_bind_address_for_port(proxy_port, family)
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if proxy_bind_addr.is_loopback:
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raise Fatal("Windivert method requires proxy to be reachable by a non loopback address.")
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if not proxy_bind_addr.is_unspecified:
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proxy_ip = proxy_bind_addr
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else:
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local_addresses = [ip_address(info[4][0]) for info in socket.getaddrinfo(socket.gethostname(), 0, family=family)]
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for addr in local_addresses:
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if not addr.is_loopback and not addr.is_link_local:
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proxy_ip = addr
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break
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else:
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raise Fatal("Windivert method requires proxy to be reachable by a non loopback address."
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f"No address found for {family.name} in {local_addresses}")
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debug2(f"Found non loopback address to connect to proxy: {proxy_ip}")
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subnet_addresses = []
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for (_, mask, exclude, network_addr, fport, lport) in subnets:
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if fport and lport:
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if lport > fport:
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raise Fatal("lport must be less than or equal to fport")
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ports = (fport, lport)
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else:
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ports = None
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subnet_addresses.append((ip_network(f"{network_addr}/{mask}"), ports, exclude))
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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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"proxy_addr": (proxy_ip, proxy_port)
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}
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def wait_for_firewall_ready(self, sshuttle_pid):
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debug2(f"network_config={self.network_config}")
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self.conntrack = ConnTrack(f"sshuttle-windivert-{sshuttle_pid}", WINDIVERT_MAX_CONNECTIONS)
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if not self.conntrack.is_owner:
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raise Fatal("ConnTrack should be owner in wait_for_firewall_ready()")
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thread_target_funcs = (self._egress_divert, self._ingress_divert, self._connection_gc)
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ready_events = []
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for fn in thread_target_funcs:
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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, group):
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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_proxy_port = False
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result.user = False
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result.dns = False
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# ipv6 only able to support with Windivert 2.x due to bugs in filter parsing
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# TODO(nom3ad): Enable ipv6 once https://github.com/ffalcinelli/pydivert/pull/57 merged
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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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if self.conntrack.is_owner:
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raise Fatal("ConnTrack should not be owner in get_tcp_dstip()")
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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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"""divert outgoing packets to proxy"""
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proto = IPProtocol.TCP
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filter = f"outbound and {proto.filter}"
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af_filters = []
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for af, c in self.network_config.items():
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subnet_include_filters = []
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subnet_exclude_filters = []
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for ip_net, ports, exclude in c["subnets"]:
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first_ip = ip_net.network_address.exploded
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last_ip = ip_net.broadcast_address.exploded
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if first_ip == last_ip:
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_subnet_filter = f"{af.filter}.DstAddr=={first_ip}"
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else:
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_subnet_filter = f"{af.filter}.DstAddr>={first_ip} and {af.filter}.DstAddr<={last_ip}"
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if ports:
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if ports[0] == ports[1]:
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_subnet_filter += f" and {proto.filter}.DstPort=={ports[0]}"
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else:
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_subnet_filter += f" and tcp.DstPort>={ports[0]} and tcp.DstPort<={ports[1]}"
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(subnet_exclude_filters if exclude else subnet_include_filters).append(f"({_subnet_filter})")
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_af_filter = f"{af.filter}"
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if subnet_include_filters:
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_af_filter += f" and ({' or '.join(subnet_include_filters)})"
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if subnet_exclude_filters:
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# TODO(noma3ad) use not() operator with Windivert2 after upgrade
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_af_filter += f" and (({' or '.join(subnet_exclude_filters)})? false : true)"
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proxy_ip, proxy_port = c["proxy_addr"]
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# Avoids proxy outbound traffic getting directed to itself
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proxy_guard_filter = f"(({af.filter}.DstAddr=={proxy_ip.exploded} and tcp.DstPort=={proxy_port})? false : true)"
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_af_filter += f" and {proxy_guard_filter}"
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af_filters.append(_af_filter)
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if not af_filters:
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raise Fatal("At least one ipv4 or ipv6 subnet is expected")
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filter = f"{filter} and ({' or '.join(af_filters)})"
|
|
debug1(f"[EGRESS] {filter=}")
|
|
with pydivert.WinDivert(filter, layer=pydivert.Layer.NETWORK, flags=pydivert.Flag.DEFAULT) as w:
|
|
proxy_ipv4, proxy_ipv6 = None, None
|
|
if IPFamily.IPv4 in self.network_config:
|
|
proxy_ipv4 = self.network_config[IPFamily.IPv4]["proxy_addr"]
|
|
proxy_ipv4 = proxy_ipv4[0].exploded, proxy_ipv4[1]
|
|
if IPFamily.IPv6 in self.network_config:
|
|
proxy_ipv6 = self.network_config[IPFamily.IPv6]["proxy_addr"]
|
|
proxy_ipv6 = proxy_ipv6[0].exploded, proxy_ipv6[1]
|
|
ready_cb()
|
|
verbose = get_verbose_level()
|
|
for pkt in w:
|
|
verbose >= 3 and debug3("[EGRESS] " + repr_pkt(pkt))
|
|
if pkt.tcp.syn and not pkt.tcp.ack:
|
|
# SYN sent (start of 3-way handshake connection establishment from our side, we wait for SYN+ACK)
|
|
self.conntrack.add(
|
|
socket.IPPROTO_TCP,
|
|
pkt.src_addr,
|
|
pkt.src_port,
|
|
pkt.dst_addr,
|
|
pkt.dst_port,
|
|
ConnState.TCP_SYN_SENT,
|
|
)
|
|
if pkt.tcp.fin:
|
|
# FIN sent (start of graceful close our side, and we wait for ACK)
|
|
self.conntrack.update(IPProtocol.TCP, pkt.src_addr, pkt.src_port, ConnState.TCP_FIN_WAIT_1)
|
|
if pkt.tcp.rst:
|
|
# RST sent (initiate abrupt connection teardown from our side, so we don't expect any reply)
|
|
self.conntrack.remove(IPProtocol.TCP, pkt.src_addr, pkt.src_port)
|
|
|
|
# DNAT
|
|
if pkt.ipv4 and proxy_ipv4:
|
|
pkt.dst_addr, pkt.tcp.dst_port = proxy_ipv4
|
|
if pkt.ipv6 and proxy_ipv6:
|
|
pkt.dst_addr, pkt.tcp.dst_port = proxy_ipv6
|
|
|
|
# XXX: If we set loopback proxy address (DNAT), then we should do SNAT as well
|
|
# by setting src_addr to loopback address.
|
|
# Otherwise injecting packet will be ignored by Windows network stack
|
|
# as they packet has to cross public to private address space.
|
|
# See: https://github.com/basil00/Divert/issues/82
|
|
# Managing SNAT is more trickier, as we have to restore the original source IP address for reply packets.
|
|
# >>> pkt.dst_addr = proxy_ipv4
|
|
w.send(pkt, recalculate_checksum=True)
|
|
|
|
def _ingress_divert(self, ready_cb):
|
|
"""handles incoming packets from proxy"""
|
|
proto = IPProtocol.TCP
|
|
# Windivert treats all local process traffic as outbound, regardless of origin external/loopback iface
|
|
direction = "outbound"
|
|
proxy_addr_filters = []
|
|
for af, c in self.network_config.items():
|
|
if not c["subnets"]:
|
|
continue
|
|
proxy_ip, proxy_port = c["proxy_addr"]
|
|
# "ip.SrcAddr=={hex(int(proxy_ip))}" # only Windivert >=2 supports this
|
|
proxy_addr_filters.append(f"{af.filter}.SrcAddr=={proxy_ip.exploded} and tcp.SrcPort=={proxy_port}")
|
|
if not proxy_addr_filters:
|
|
raise Fatal("At least one ipv4 or ipv6 address is expected")
|
|
filter = f"{direction} and {proto.filter} and ({' or '.join(proxy_addr_filters)})"
|
|
debug1(f"[INGRESS] {filter=}")
|
|
with pydivert.WinDivert(filter, layer=pydivert.Layer.NETWORK, flags=pydivert.Flag.DEFAULT) as w:
|
|
ready_cb()
|
|
verbose = get_verbose_level()
|
|
for pkt in w:
|
|
verbose >= 3 and debug3("[INGRESS] " + repr_pkt(pkt))
|
|
if pkt.tcp.syn and pkt.tcp.ack:
|
|
# SYN+ACK received (connection established from proxy
|
|
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 proxy. 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 proxy. Don't expect any more packets. proxy expects an ACK)
|
|
conn = self.conntrack.remove(IPProtocol.TCP, pkt.dst_addr, pkt.dst_port)
|
|
elif pkt.tcp.fin:
|
|
# FIN received (proxy initiated graceful close. Expect a final ACK for a FIN packet)
|
|
conn = self.conntrack.update(IPProtocol.TCP, pkt.dst_addr, pkt.dst_port, ConnState.TCP_CLOSE_WAIT)
|
|
else:
|
|
# data fragments and ACKs
|
|
conn = self.conntrack.get(socket.IPPROTO_TCP, pkt.dst_addr, pkt.dst_port)
|
|
if not conn:
|
|
verbose >= 2 and 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()
|