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import os
import importlib
import socket
import struct
import errno
from sshuttle.helpers import Fatal, debug3
def original_dst(sock):
try:
SO_ORIGINAL_DST = 80
SOCKADDR_MIN = 16
sockaddr_in = sock.getsockopt(socket.SOL_IP,
SO_ORIGINAL_DST, SOCKADDR_MIN)
(proto, port, a, b, c, d) = struct.unpack('!HHBBBB', sockaddr_in[:8])
# FIXME: decoding is IPv4 only.
assert(socket.htons(proto) == socket.AF_INET)
ip = '%d.%d.%d.%d' % (a, b, c, d)
return (ip, port)
except socket.error as e:
if e.args[0] == errno.ENOPROTOOPT:
return sock.getsockname()
raise
class Features(object):
pass
class BaseMethod(object):
def __init__(self, name):
self.firewall = None
self.name = name
def set_firewall(self, firewall):
self.firewall = firewall
@staticmethod
def get_supported_features():
result = Features()
result.ipv6 = False
result.udp = False
result.dns = True
result.user = False
return result
@staticmethod
def get_tcp_dstip(sock):
return original_dst(sock)
@staticmethod
def recv_udp(udp_listener, bufsize):
debug3('Accept UDP using recvfrom.\n')
data, srcip = udp_listener.recvfrom(bufsize)
return (srcip, None, data)
def send_udp(self, sock, srcip, dstip, data):
if srcip is not None:
Fatal("Method %s send_udp does not support setting srcip to %r"
% (self.name, srcip))
sock.sendto(data, dstip)
def setup_tcp_listener(self, tcp_listener):
pass
def setup_udp_listener(self, udp_listener):
pass
def assert_features(self, features):
avail = self.get_supported_features()
for key in ["udp", "dns", "ipv6", "user"]:
if getattr(features, key) and not getattr(avail, key):
raise Fatal(
"Feature %s not supported with method %s.\n" %
(key, self.name))
def setup_firewall(self, port, dnsport, nslist, family, subnets, udp,
user):
raise NotImplementedError()
def restore_firewall(self, port, family, udp, user):
raise NotImplementedError()
@staticmethod
def firewall_command(line):
return False
def _program_exists(name):
paths = (os.getenv('PATH') or os.defpath).split(os.pathsep)
for p in paths:
fn = '%s/%s' % (p, name)
if os.path.exists(fn):
return not os.path.isdir(fn) and os.access(fn, os.X_OK)
def get_method(method_name):
module = importlib.import_module("sshuttle.methods.%s" % method_name)
return module.Method(method_name)
def get_auto_method():
if _program_exists('iptables'):
method_name = "nat"
elif _program_exists('pfctl'):
method_name = "pf"
elif _program_exists('ipfw'):
method_name = "ipfw"
else:
raise Fatal(
"can't find either iptables or pfctl; check your PATH")
return get_method(method_name)
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