ensure non loopback address for windivert method

sshuttle/client.py

@@ -307,9 +307,9 @@ class FirewallClient:
 
                 def get_pfile():
                     if can_use_stdio:
-                        import io
                         self.p.stdin.write(b'STDIO:\n')
                         self.p.stdin.flush()
+
                         class RWPair:
                             def __init__(self, r, w):
                                 self.r = r
@@ -318,13 +318,15 @@ class FirewallClient:
                                 self.readline = r.readline
                                 self.write = w.write
                                 self.flush = w.flush
+
                             def close(self):
                                 for f in self.r, self.w:
                                     try:
                                         f.close()
-                                    except:
+                                    except Exception:
                                         pass
                         return RWPair(self.p.stdout, self.p.stdin)
+                        # import io
                         # return io.BufferedRWPair(self.p.stdout, self.p.stdin, 1)
                     else:
                         import base64
@@ -885,7 +887,11 @@ def main(listenip_v6, listenip_v4,
 
     # listenip_v4 contains user specified value or it is set to "auto".
     if listenip_v4 == "auto":
+        if sys.platform == 'win32':
+            listenip_v4 = ('0.0.0.0', 0)  # windivert method won't work with loopback interface
+        else:
             listenip_v4 = ('127.0.0.1', 0)
+        debug1("Using default IPv4 listen address " + listenip_v4[0])
 
     # listenip_v6 is...
     #    None when IPv6 is disabled.
@@ -895,8 +901,11 @@ def main(listenip_v6, listenip_v4,
         debug1("IPv6 disabled by --disable-ipv6")
     if listenip_v6 == "auto":
         if avail.ipv6:
-            debug1("IPv6 enabled: Using default IPv6 listen address ::1")
+            if sys.platform == 'win32':
+                listenip_v6 = ('::', 0)  # windivert method won't work with loopback interface
+            else:
                 listenip_v6 = ('::1', 0)
+            debug1("IPv6 enabled: Using default IPv6 listen address " + listenip_v6[0])
         else:
             debug1("IPv6 disabled since it isn't supported by method "
                    "%s." % fw.method.name)

sshuttle/methods/windivert.py

@@ -4,6 +4,8 @@ import ipaddress
 import threading
 from collections import namedtuple
 import socket
+import subprocess
+import re
 from multiprocessing import shared_memory
 import struct
 from functools import wraps
@@ -270,6 +272,18 @@ class Method(BaseMethod):
     def __init__(self, name):
         super().__init__(name)
 
+    def _get_local_proxy_listen_addr(self, port, family):
+        proto = "TCPv6" if family.version == 6 else "TCP"
+        for line in subprocess.check_output(["netstat", "-a", "-n", "-p", proto]).decode().splitlines():
+            try:
+                _, local_addr, _, state, *_ = re.split(r"\s+", line.strip())
+            except ValueError:
+                continue
+            port_suffix = ":" + str(port)
+            if state == "LISTENING" and local_addr.endswith(port_suffix):
+                return ipaddress.ip_address(local_addr[:-len(port_suffix)].strip("[]"))
+        raise Fatal("Could not find listening address for {}/{}".format(port, proto))
+
     def setup_firewall(self, port, dnsport, nslist, family, subnets, udp, user, tmark):
         log(f"{port=}, {dnsport=}, {nslist=}, {family=}, {subnets=}, {udp=}, {user=}, {tmark=}")
 
@@ -279,16 +293,20 @@ class Method(BaseMethod):
         family = IPFamily(family)
 
         # using loopback proxy address never worked.
+        # >>> self.proxy_addr[family] = family.loopback_addr
         # See: https://github.com/basil00/Divert/issues/17#issuecomment-341100167 ,https://github.com/basil00/Divert/issues/82)
         # As a workaround we use another interface ip instead.
-        # self.proxy_addr[family] = family.loopback_addr
+
+        local_addr = self._get_local_proxy_listen_addr(port, family)
         for addr in (ipaddress.ip_address(info[4][0]) for info in socket.getaddrinfo(socket.gethostname(), None)):
             if addr.is_loopback or addr.version != family.version:
                 continue
+            if local_addr.is_unspecified or local_addr == addr:
+                debug2("Found non loopback address to connect to proxy: " + str(addr))
                 self.proxy_addr[family] = str(addr)
                 break
         else:
-            raise Fatal(f"Could not find a non loopback proxy address for {family.name}")
+            raise Fatal("Windivert method requires proxy to listen on non loopback address")
 
         self.proxy_port = port
 
@@ -423,6 +441,8 @@ class Method(BaseMethod):
             else:
                 # ip_checks.append(f"ip.SrcAddr=={hex(int(addr))}") # only Windivert >=2 supports this
                 ip_filters.append(f"ipv6.SrcAddr=={addr}")
+        if not ip_filters:
+            raise Fatal("At least ipv4 or ipv6 address is expected")
         filter = f"{direction} and {proto.filter} and ({' or '.join(ip_filters)}) and tcp.SrcPort=={self.proxy_port}"
         debug2(f"[INGRESS] {filter=}")
         with pydivert.WinDivert(filter) as w:

sshuttle/ssh.py

@@ -12,7 +12,7 @@ import ipaddress
 from urllib.parse import urlparse
 
 import sshuttle.helpers as helpers
-from sshuttle.helpers import debug2, debug3, which, get_path, Fatal
+from sshuttle.helpers import debug2, which, get_path, Fatal
 
 
 def get_module_source(name):