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etl2pcap.py
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etl2pcap.py
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#!/usr/bin/env python3
#
# etl2pcap: extract network frames from ETL trace files and export them to .pcap
#
# Copyright (C) 2019 Aurelien Aptel <[email protected]>
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
#
import struct
import math
from datetime import datetime
import sys
import argparse
import os
VERBOSE = False
def main():
global VERBOSE
ap = argparse.ArgumentParser(description="Extract network frames from ETL trace file and export them to .pcap")
ap.add_argument("--verbose", help="print more information while processing", action="store_true", default=False)
ap.add_argument("etl", help="path to etl file to process")
ap.add_argument("pcap", nargs='?', help="path to pcap file to write to. defaults to same name as input with the .pcap extension", default=None)
args = ap.parse_args()
if args.pcap is None:
if args.etl[-4:].lower() == '.etl':
args.pcap = args.etl[:-4]+".pcap"
else:
args.pcap = args.etl+".pcap"
if args.verbose:
VERBOSE = True
if not os.path.exists(args.etl):
print("%s doesn't exist"%args.etl)
exit(1)
etl_to_pcap(args.etl, args.pcap)
def etl_frames(etl_data):
b = Buf(etl_data)
ndis_provider = guid_to_bytes('2ed6006e-4729-4609-b423-3ee7bcd678ef')
while b.off < len(b.data):
wmi_start = b.off
dbg("WMI 0x%x"%wmi_start)
# WMI_BUFFER_HEADER
wmi_size = b.read('<I')
b.skip('<IIi')
start_timestamp = b.read('<q')
b.skip('<qQBBHI')
wmi_useful_size = b.read('<I')
flags = b.read('<H')
b.skip('<Hqq')
if flags & 0x40:
# compressed, skip
dbg("skipping compressed WMI_BUFFER at 0x%x"%wmi_start)
else:
while b.off < wmi_start+wmi_useful_size:
ev_start = b.off
dbg("EV 0x%x"%ev_start)
ev_size = b.read('<H')
ev_type = b.read('<B')
b.set(ev_start)
if ev_type in [1,2,3,4,16,17]:
b.skip('<HBB')
ev_size = b.read('<H')
b.set(ev_start)
elif ev_type == 18 or ev_type == 19:
b.skip('<HBBHHII')
off_timestamp = b.read('<q')
ev_provider = b.read_bytes(16)
if ev_provider == ndis_provider:
b.skip('<HBBBBHQII 16B')
b.skip('<II')
frag_size = b.read('<I')
ev_left = ev_size - (b.off-ev_start)
assert(frag_size == ev_left)
t = start_timestamp + off_timestamp
yield (t, b.read_bytes(ev_size - (b.off - ev_start)))
assert(ev_size > 0 and ev_start+ev_size <= wmi_start+wmi_useful_size)
b.set(ev_start + ev_size)
al = 8 - (b.off%8)
if al < 8:
b.skip_bytes(al)
b.set(wmi_start+wmi_size)
def etl_to_pcap(etl_fn, pcap_fn):
etl_data = None
info("reading etl file %s in memory..."%etl_fn)
with open(etl_fn, 'rb') as f:
etl_data = f.read()
info("looking for etl frames...")
frames = []
for t, data in etl_frames(etl_data):
dbg("found frame at t=%d, %d bytes"%(t, len(data)))
frames.append((t, data))
info("sorting %d frames by timestamp..."%(len(frames)))
frames.sort(key=lambda x: x[0])
info("opening pcap file %s for writing..."%pcap_fn)
with open(pcap_fn, 'wb+') as f:
info("writing pcap header")
f.write(struct.pack('<I', 0xa1b2c3d4)) # magic
f.write(struct.pack('<H', 2)) # major version
f.write(struct.pack('<H', 4)) # minor version
f.write(struct.pack('<i', 0)) # local time seconds offset to gmt
f.write(struct.pack('<I', 0)) # sigfigs
f.write(struct.pack('<I', 65535)) # max pkt len
f.write(struct.pack('<I', 1)) # ethernet
info("writing frames to pcap...")
for t, data in frames:
unix = filetime_to_epoch(t)
usec, sec = math.modf(unix)
usec = int(usec*1000)
sec = int(sec)
dbg("writing frame at t=%s.%d, %d bytes..."%(epoch_to_str(sec), usec, len(data)))
f.write(struct.pack('<I', sec))
f.write(struct.pack('<I', usec))
f.write(struct.pack('<I', len(data)))
f.write(struct.pack('<I', len(data)))
f.write(data)
info("closing...")
info("dumped %d frames to %s. done."%(len(frames), pcap_fn))
class Buf:
def __init__(self, data):
self.data = data
self.off = 0
def peek(self, fmt, off):
return struct.unpack_from(fmt, self.data, self.off+off)[0]
def read(self, fmt):
size = struct.calcsize(fmt)
r = struct.unpack_from(fmt, self.data, self.off)[0]
self.off += size
return r
def set(self, off):
# allow setting at the exact end
assert(0 <= off <= len(self.data))
self.off = off
def skip(self, fmt):
size = struct.calcsize(fmt)
assert(self.off + size < len(self.data))
self.off += size
def read_bytes(self, n):
assert(n >= 0)
r = self.data[self.off:self.off+n]
self.off += n
return r
def skip_bytes(self, n):
assert(n >= 0)
self.off += n
def read_ucs2_str(self):
buf = bytearray()
c = self.read('<H')
while c != 0:
buf.append((c>>8) & 0xff)
buf.append(c & 0xff)
c = self.read('H')
return buf.decode('utf-16-be')
def dbg(s):
if VERBOSE:
print(s)
def info(s):
print("[*]",s)
def filetime_to_epoch(t):
start = 0x019DB1DED53E8000;
ticks_per_sec = 10000000
return (t-start)/ticks_per_sec
def epoch_to_str(t):
return datetime.utcfromtimestamp(t).strftime('%Y-%m-%d %H:%M:%S')
def guid_to_bytes(g):
a,b,c,d,e = [int(x, 16) for x in g.split("-")]
return struct.pack('<IHH', a,b,c) + struct.pack('>HIH', d, e>>16, e & 0xffff)
if __name__ == '__main__':
main()