52 lines
1.8 KiB
Python
Executable file
52 lines
1.8 KiB
Python
Executable file
# This file is part of Scapy
|
|
# See http://www.secdev.org/projects/scapy for more information
|
|
# Copyright (C) Philippe Biondi <phil@secdev.org>
|
|
# This program is published under a GPLv2 license
|
|
|
|
"""
|
|
L2TP (Layer 2 Tunneling Protocol) for VPNs.
|
|
|
|
[RFC 2661]
|
|
"""
|
|
|
|
import struct
|
|
|
|
from scapy.packet import Packet, bind_layers, bind_bottom_up
|
|
from scapy.fields import BitEnumField, ConditionalField, FlagsField, \
|
|
PadField, ShortField
|
|
from scapy.layers.inet import UDP
|
|
from scapy.layers.ppp import PPP
|
|
|
|
|
|
class L2TP(Packet):
|
|
name = "L2TP"
|
|
fields_desc = [
|
|
FlagsField("hdr", 0, 12, ['res00', 'res01', 'res02', 'res03', 'priority', 'offset', # noqa: E501
|
|
'res06', 'sequence', 'res08', 'res09', 'length', 'control']), # noqa: E501
|
|
BitEnumField("version", 2, 4, {2: 'L2TPv2'}),
|
|
|
|
ConditionalField(ShortField("len", 0),
|
|
lambda pkt: pkt.hdr & 'control+length'),
|
|
ShortField("tunnel_id", 0),
|
|
ShortField("session_id", 0),
|
|
ConditionalField(ShortField("ns", 0),
|
|
lambda pkt: pkt.hdr & 'sequence+control'),
|
|
ConditionalField(ShortField("nr", 0),
|
|
lambda pkt: pkt.hdr & 'sequence+control'),
|
|
ConditionalField(
|
|
PadField(ShortField("offset", 0), 4, b"\x00"),
|
|
lambda pkt: not (pkt.hdr & 'control') and pkt.hdr & 'offset'
|
|
)
|
|
]
|
|
|
|
def post_build(self, pkt, pay):
|
|
if self.len is None:
|
|
tmp_len = len(pkt) + len(pay)
|
|
pkt = pkt[:2] + struct.pack("!H", tmp_len) + pkt[4:]
|
|
return pkt + pay
|
|
|
|
|
|
bind_bottom_up(UDP, L2TP, dport=1701)
|
|
bind_bottom_up(UDP, L2TP, sport=1701)
|
|
bind_layers(UDP, L2TP, dport=1701, sport=1701)
|
|
bind_layers(L2TP, PPP,)
|