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better windivert filters
This commit is contained in:
nom3ad
Brian May
parent
8fa15c3ca8
commit
dadfba488b
@ -19,6 +19,7 @@ from sshuttle.helpers import debug3, log, debug1, debug2, get_verbose_level, Fat
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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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@ -275,12 +276,11 @@ 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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def _get_bind_addresses_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().splitlines():
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try:
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@ -292,31 +292,28 @@ class Method(BaseMethod):
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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, port, dnsport, nslist, family, subnets, udp, user, group, tmark):
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log(f"{port=}, {dnsport=}, {nslist=}, {family=}, {subnets=}, {udp=}, {user=}, {tmark=}")
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def setup_firewall(self, proxy_port, dnsport, nslist, family, subnets, udp, user, group, tmark):
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log(f"{proxy_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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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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local_addr = self._get_bind_addresses_for_port(proxy_port, family)
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for addr in (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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proxy_ip = 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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raise Fatal("Windivert method requires proxy to listen on a non loopback address")
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subnet_addresses = []
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for (_, mask, exclude, network_addr, fport, lport) in subnets:
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@ -329,10 +326,11 @@ class Method(BaseMethod):
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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):
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debug2(f"network_config={self.network_config} proxy_addr={self.proxy_addr}")
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debug2(f"network_config={self.network_config}")
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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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@ -380,6 +378,7 @@ class Method(BaseMethod):
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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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@ -391,20 +390,21 @@ class Method(BaseMethod):
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ip_net = ip_network(cidr)
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first_ip = ip_net.network_address
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last_ip = ip_net.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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subnet_filters.append(f"({af.filter}.DstAddr>={first_ip} and {af.filter}.DstAddr<={last_ip})")
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proxy_ip, proxy_port = c["proxy_addr"]
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proxy_guard_filter = f'({af.filter}.DstAddr!={proxy_ip} or tcp.DstPort!={proxy_port})'
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family_filters.append(f"{af.filter} and ({' or '.join(subnet_filters)}) and {proxy_guard_filter}")
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filter = f"{filter} and ({' or '.join(family_filters)})"
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debug1(f"[OUTBOUND] {filter=}")
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debug1(f"[EGRESS] {filter=}")
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with pydivert.WinDivert(filter, layer=pydivert.Layer.NETWORK, flags=pydivert.Flag.DEFAULT) 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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proxy_ipv4 = self.network_config[IPFamily.IPv4]["proxy_addr"] if IPFamily.IPv4 in self.network_config else None
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proxy_ipv6 = self.network_config[IPFamily.IPv6]["proxy_addr"] if IPFamily.IPv6 in self.network_config else None
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verbose = get_verbose_level()
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for pkt in w:
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verbose >= 3 and debug3(">>> " + repr_pkt(pkt))
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verbose >= 3 and debug3("[EGRESS] " + 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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@ -423,11 +423,10 @@ class Method(BaseMethod):
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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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if pkt.ipv4 and proxy_ipv4:
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pkt.dst_addr, pkt.tcp.dst_port = proxy_ipv4
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if pkt.ipv6 and proxy_ipv6:
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pkt.dst_addr, pkt.tcp.dst_port = proxy_ipv6
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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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@ -435,30 +434,28 @@ class Method(BaseMethod):
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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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# >>> pkt.dst_addr = proxy_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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"""handles incoming packets from proxy"""
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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 (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}"
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# Windivert treats all local process traffic as outbound, regardless of origin external/loopback iface
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direction = "outbound"
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proxy_addr_filters = []
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for af, c in self.network_config.items():
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proxy_ip, proxy_port = c["proxy_addr"]
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# "ip.SrcAddr=={hex(int(proxy_ip))}" # only Windivert >=2 supports this
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proxy_addr_filters.append(f"{af.filter}.SrcAddr=={proxy_ip} and tcp.SrcPort=={proxy_port}")
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if not proxy_addr_filters:
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raise Fatal("At least one ipv4 or ipv6 address is expected")
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filter = f"{direction} and {proto.filter} and ({' or '.join(proxy_addr_filters)})"
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debug1(f"[INGRESS] {filter=}")
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with pydivert.WinDivert(filter, layer=pydivert.Layer.NETWORK, flags=pydivert.Flag.DEFAULT) as w:
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ready_cb()
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verbose = get_verbose_level()
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for pkt in w:
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verbose >= 3 and debug3("<<< " + repr_pkt(pkt))
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verbose >= 3 and debug3("[INGRESS] " + repr_pkt(pkt))
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if pkt.tcp.syn and pkt.tcp.ack:
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# SYN+ACK received (connection established)
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conn = self.conntrack.update(IPProtocol.TCP, pkt.dst_addr, pkt.dst_port, ConnState.TCP_ESTABLISHED)
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