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[Draft Pull Request] Proof of concept Mac utun support #4100

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[Draft Pull Request] Proof of concept Mac utun support #4100

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84 changes: 65 additions & 19 deletions scapy/layers/tuntap.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,14 +13,15 @@

import socket
import time
import re
from fcntl import ioctl

from scapy.compat import raw, bytes_encode
from scapy.config import conf
from scapy.consts import BIG_ENDIAN, BSD, LINUX
from scapy.data import ETHER_TYPES, MTU
from scapy.error import warning, log_runtime
from scapy.fields import Field, FlagsField, StrFixedLenField, XShortEnumField
from scapy.fields import Field, FlagsField, StrFixedLenField, XShortEnumField, IntField, BitField
from scapy.interfaces import network_name
from scapy.layers.inet import IP
from scapy.layers.inet6 import IPv46, IPv6
Expand All @@ -36,6 +37,10 @@
LINUX_IFF_NO_PI = 0x1000
LINUX_IFNAMSIZ = 16

# MacOS-specific defines (/usr/include/net/if_utun.h and /usr/include/sys/kern_control.h)
DARWIN_CTLIOCGINFO = 0xc0644e03
DARWIN_UTUN_CONTROL_NAME = b"com.apple.net.utun_control"
DARWIN_MAX_KCTL_NAME = 96

class NativeShortField(Field):
def __init__(self, name, default):
Expand All @@ -61,6 +66,17 @@ class LinuxTunIfReq(Packet):
]


class MacOSTunIfReq(Packet):
"""
Structure for issuing MacOS ioctl commands (``struct ctlinfo``).
See net/if_utun.h and sys/kern_control.h for reference.
"""
fields_desc = [
BitField("ctl_id", 0, -32),
StrFixedLenField("ctl_name", DARWIN_UTUN_CONTROL_NAME, DARWIN_MAX_KCTL_NAME)
]


class LinuxTunPacketInfo(TunPacketInfo):
"""
Base for TUN packets.
Expand All @@ -78,6 +94,22 @@ class LinuxTunPacketInfo(TunPacketInfo):
]


class MacOSUtunPacketInfo(Packet):
fields_desc = [
IntField("addr_family", socket.AF_INET)
]

def guess_payload_class(self, payload):
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Use bind_layers() rather than implementing guess_payload_class.

match self.getfieldval("addr_family"):
case socket.AF_INET:
return IP
case socket.AF_INET6:
return IPv6
case _:
raise NotImplementedError(
"Non-IP address families are not supported")


class TunTapInterface(SimpleSocket):
"""
A socket to act as the host's peer of a tun / tap interface.
Expand Down Expand Up @@ -116,7 +148,8 @@ def __init__(self, iface=None, mode_tun=None, default_read_size=MTU,

self.mode_tun = mode_tun
if self.mode_tun is None:
if self.iface.startswith(b"tun"):
if (self.iface.startswith(b"tun") or
self.iface.startswith(b"utun")):
self.mode_tun = True
elif self.iface.startswith(b"tap"):
self.mode_tun = False
Expand Down Expand Up @@ -153,23 +186,6 @@ def __init__(self, iface=None, mode_tun=None, default_read_size=MTU,
"truncating!" % (LINUX_IFNAMSIZ,))
self.iface = self.iface[:LINUX_IFNAMSIZ]

elif BSD: # also DARWIN
if not (self.iface.startswith(b"tap") or
self.iface.startswith(b"tun")):
raise ValueError("Interface names must start with `tun` or "
"`tap` on BSD and Darwin")
devname = b"/dev/" + self.iface
if not self.strip_packet_info:
warning("tun/tap devices on BSD and Darwin never include "
"packet info!")
self.strip_packet_info = True
else:
raise NotImplementedError("TunTapInterface is not supported on "
"this platform!")

sock = open(devname, "r+b", buffering=0)

if LINUX:
if self.mode_tun:
flags = LINUX_IFF_TUN
else:
Expand All @@ -188,8 +204,38 @@ def __init__(self, iface=None, mode_tun=None, default_read_size=MTU,
ifrn_name=self.iface,
ifru_flags=flags))

sock = open(devname, "r+b", buffering=0)
ioctl(sock, LINUX_TUNSETIFF, tsetiff)

elif BSD:
if not (self.iface.startswith(b"tap") or
self.iface.startswith(b"tun") or
self.iface.startswith(b"utun")):
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@micolous micolous Aug 28, 2023 •
edited
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utun is Darwin-specific, so shouldn't be attempted on BSD.

However, tap and tun on Darwin are provided by a third-party kext (which works the same way as BSD's tap and tun), so Darwin will still need to hit this BSD branch.

raise ValueError("Interface names must start with `tun`, `utun`, or "
"`tap` on BSD and Darwin")

if (self.iface.startswith(b"utun")):
self.kernel_packet_class = MacOSUtunPacketInfo
self.mtu_overhead = 4

match = re.match(r"([a-z]+)([0-9]+)", self.iface.decode("utf-8"), re.I)
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@micolous micolous Aug 28, 2023 •
edited
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Don't need to import re or decode bytestrings - just strip the prefix (b'utun') from the string:

# self.iface = b'utun0'
interface_num = int(self.iface[4:])

if match:
interfaceNum = int(match.group(2))

rawSocket = socket.socket(socket.PF_SYSTEM, socket.SOCK_DGRAM, socket.SYSPROTO_CONTROL)
ctl_info = ioctl(rawSocket, DARWIN_CTLIOCGINFO, raw(MacOSTunIfReq()))
rawSocket.connect((MacOSTunIfReq(ctl_info).getfieldval("ctl_id"), interfaceNum + 1))

sock = rawSocket.makefile(mode="rwb", buffering=0)

else:
devname = b"/dev/" + self.iface
sock = open(devname, "r+b", buffering=0)

else:
raise NotImplementedError("TunTapInterface is not supported on "
"this platform!")

self.closed = False
self.default_read_size = default_read_size
super(TunTapInterface, self).__init__(sock)
Expand Down
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