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import struct
from sshuttle.firewall import subnet_weight
from sshuttle.helpers import family_to_string
from sshuttle.linux import ipt, ipt_chain_exists
from sshuttle.methods import BaseMethod
from sshuttle.helpers import debug1, debug2, debug3, Fatal, which
import socket
import os
IP_TRANSPARENT = 19
IP_ORIGDSTADDR = 20
IP_RECVORIGDSTADDR = IP_ORIGDSTADDR
SOL_IPV6 = 41
IPV6_ORIGDSTADDR = 74
IPV6_RECVORIGDSTADDR = IPV6_ORIGDSTADDR
def recv_udp(listener, bufsize):
debug3('Accept UDP python using recvmsg.')
data, ancdata, _, srcip = listener.recvmsg(
4096, socket.CMSG_SPACE(24))
dstip = None
family = 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
else:
raise Fatal("Unsupported socket type '%s'" % family)
ip = socket.inet_ntop(family, cmsg_data[start:start + length])
dstip = (ip, port)
break
elif cmsg_level == SOL_IPV6 and cmsg_type == IPV6_ORIGDSTADDR:
family, port = struct.unpack('=HH', cmsg_data[0:4])
port = socket.htons(port)
if family == socket.AF_INET6:
start = 8
length = 16
else:
raise Fatal("Unsupported socket type '%s'" % family)
ip = socket.inet_ntop(family, cmsg_data[start:start + length])
dstip = (ip, port)
break
return (srcip, dstip, data)
class Method(BaseMethod):
def get_supported_features(self):
result = super(Method, self).get_supported_features()
result.ipv6 = True
result.udp = True
result.dns = True
return result
def get_tcp_dstip(self, sock):
return sock.getsockname()
def recv_udp(self, udp_listener, bufsize):
srcip, dstip, data = recv_udp(udp_listener, bufsize)
if not dstip:
debug1(
"-- ignored UDP from %r: "
"couldn't determine destination IP address\n" % (srcip,))
return None
return srcip, dstip, data
def setsockopt_error(self, e):
"""The tproxy method needs root permissions to successfully
set the IP_TRANSPARENT option on sockets. This method is
called when we receive a PermissionError when trying to do
so."""
raise Fatal("Insufficient permissions for tproxy method.\n"
"Your effective UID is %d, not 0. Try rerunning as root.\n"
% os.geteuid())
def send_udp(self, sock, srcip, dstip, data):
if not srcip:
debug1(
"-- ignored UDP to %r: "
"couldn't determine source IP address\n" % (dstip,))
return
sender = socket.socket(sock.family, socket.SOCK_DGRAM)
sender.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
try:
sender.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
except PermissionError as e:
self.setsockopt_error(e)
sender.bind(srcip)
sender.sendto(data, dstip)
sender.close()
def setup_tcp_listener(self, tcp_listener):
try:
tcp_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
except PermissionError as e:
self.setsockopt_error(e)
def setup_udp_listener(self, udp_listener):
try:
udp_listener.setsockopt(socket.SOL_IP, IP_TRANSPARENT, 1)
except PermissionError as e:
self.setsockopt_error(e)
if udp_listener.v4 is not None:
udp_listener.v4.setsockopt(
socket.SOL_IP, IP_RECVORIGDSTADDR, 1)
if udp_listener.v6 is not None:
udp_listener.v6.setsockopt(SOL_IPV6, IPV6_RECVORIGDSTADDR, 1)
def setup_firewall(self, port, dnsport, nslist, family, subnets, udp,
user, group, tmark):
if family not in [socket.AF_INET, socket.AF_INET6]:
raise Exception(
'Address family "%s" unsupported by tproxy method'
% family_to_string(family))
table = "mangle"
def _ipt(*args):
return ipt(family, table, *args)
def _ipt_proto_ports(proto, fport, lport):
return proto + ('--dport', '%d:%d' % (fport, lport)) \
if fport else proto
mark_chain = 'sshuttle-m-%s' % port
tproxy_chain = 'sshuttle-t-%s' % port
divert_chain = 'sshuttle-d-%s' % port
# basic cleanup/setup of chains
self.restore_firewall(port, family, udp, user)
_ipt('-N', mark_chain)
_ipt('-F', mark_chain)
_ipt('-N', divert_chain)
_ipt('-F', divert_chain)
_ipt('-N', tproxy_chain)
_ipt('-F', tproxy_chain)
_ipt('-I', 'OUTPUT', '1', '-j', mark_chain)
_ipt('-I', 'PREROUTING', '1', '-j', tproxy_chain)
# Don't have packets sent to any of our local IP addresses go
# through the tproxy or mark chains.
#
# Without this fix, if a large subnet is redirected through
# sshuttle (i.e., 0/0), then the user may be unable to receive
# UDP responses or connect to their own machine using an IP
# besides (127.0.0.1). Prior to including these lines, the
# documentation reminded the user to use -x to exclude their
# own IP addresses to receive UDP responses if they are
# redirecting a large subnet through sshuttle (i.e., 0/0).
_ipt('-A', tproxy_chain, '-j', 'RETURN', '-m', 'addrtype',
'--dst-type', 'LOCAL')
_ipt('-A', mark_chain, '-j', 'RETURN', '-m', 'addrtype',
'--dst-type', 'LOCAL')
_ipt('-A', divert_chain, '-j', 'MARK', '--set-mark', tmark)
_ipt('-A', divert_chain, '-j', 'ACCEPT')
_ipt('-A', tproxy_chain, '-m', 'socket', '-j', divert_chain,
'-m', 'tcp', '-p', 'tcp')
if udp:
_ipt('-A', tproxy_chain, '-m', 'socket', '-j', divert_chain,
'-m', 'udp', '-p', 'udp')
for _, ip in [i for i in nslist if i[0] == family]:
_ipt('-A', mark_chain, '-j', 'MARK', '--set-mark', tmark,
'--dest', '%s/32' % ip,
'-m', 'udp', '-p', 'udp', '--dport', '53')
_ipt('-A', tproxy_chain, '-j', 'TPROXY',
'--tproxy-mark', tmark,
'--dest', '%s/32' % ip,
'-m', 'udp', '-p', 'udp', '--dport', '53',
'--on-port', str(dnsport))
for _, swidth, sexclude, snet, fport, lport \
in sorted(subnets, key=subnet_weight, reverse=True):
tcp_ports = ('-p', 'tcp')
tcp_ports = _ipt_proto_ports(tcp_ports, fport, lport)
if sexclude:
_ipt('-A', mark_chain, '-j', 'RETURN',
'--dest', '%s/%s' % (snet, swidth),
'-m', 'tcp',
*tcp_ports)
_ipt('-A', tproxy_chain, '-j', 'RETURN',
'--dest', '%s/%s' % (snet, swidth),
'-m', 'tcp',
*tcp_ports)
else:
_ipt('-A', mark_chain, '-j', 'MARK', '--set-mark', tmark,
'--dest', '%s/%s' % (snet, swidth),
'-m', 'tcp',
*tcp_ports)
_ipt('-A', tproxy_chain, '-j', 'TPROXY',
'--tproxy-mark', tmark,
'--dest', '%s/%s' % (snet, swidth),
'-m', 'tcp',
*(tcp_ports + ('--on-port', str(port))))
if udp:
udp_ports = ('-p', 'udp')
udp_ports = _ipt_proto_ports(udp_ports, fport, lport)
if sexclude:
_ipt('-A', mark_chain, '-j', 'RETURN',
'--dest', '%s/%s' % (snet, swidth),
'-m', 'udp',
*udp_ports)
_ipt('-A', tproxy_chain, '-j', 'RETURN',
'--dest', '%s/%s' % (snet, swidth),
'-m', 'udp',
*udp_ports)
else:
_ipt('-A', mark_chain, '-j', 'MARK', '--set-mark', tmark,
'--dest', '%s/%s' % (snet, swidth),
'-m', 'udp',
*udp_ports)
_ipt('-A', tproxy_chain, '-j', 'TPROXY',
'--tproxy-mark', tmark,
'--dest', '%s/%s' % (snet, swidth),
'-m', 'udp',
*(udp_ports + ('--on-port', str(port))))
def restore_firewall(self, port, family, udp, user, group):
if family not in [socket.AF_INET, socket.AF_INET6]:
raise Exception(
'Address family "%s" unsupported by tproxy method'
% family_to_string(family))
table = "mangle"
def _ipt(*args):
return ipt(family, table, *args)
mark_chain = 'sshuttle-m-%s' % port
tproxy_chain = 'sshuttle-t-%s' % port
divert_chain = 'sshuttle-d-%s' % port
# basic cleanup/setup of chains
if ipt_chain_exists(family, table, mark_chain):
_ipt('-D', 'OUTPUT', '-j', mark_chain)
_ipt('-F', mark_chain)
_ipt('-X', mark_chain)
if ipt_chain_exists(family, table, tproxy_chain):
_ipt('-D', 'PREROUTING', '-j', tproxy_chain)
_ipt('-F', tproxy_chain)
_ipt('-X', tproxy_chain)
if ipt_chain_exists(family, table, divert_chain):
_ipt('-F', divert_chain)
_ipt('-X', divert_chain)
def is_supported(self):
if which("iptables") and which("ip6tables"):
return True
debug2("tproxy method not supported because 'iptables' "
"or 'ip6tables' commands are missing.\n")
return False
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