Created
October 23, 2021 16:10
-
-
Save sysopfb/93e859bf1db194d0bf928ba4de595bfe to your computer and use it in GitHub Desktop.
pure python LZNT1 wrapped in try block to allow for partial decompression or decompression of data that doesn't error out on extra data at the end
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
# Rekall Memory Forensics | |
# Copyright 2014 Google Inc. All Rights Reserved. | |
# | |
# Author: Michael Cohen scudette@google.com. | |
# | |
# 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 2 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
# | |
# Added try block to prevent erroring out on extra data at the end, primarily for malware research | |
"""Decompression support for the LZNT1 compression algorithm. | |
Reference: | |
http://msdn.microsoft.com/en-us/library/jj665697.aspx | |
(2.5 LZNT1 Algorithm Details) | |
https://github.com/libyal/reviveit/ | |
https://github.com/sleuthkit/sleuthkit/blob/develop/tsk/fs/ntfs.c | |
""" | |
import array | |
import cStringIO | |
import logging | |
import struct | |
def get_displacement(offset): | |
"""Calculate the displacement.""" | |
result = 0 | |
while offset >= 0x10: | |
offset >>= 1 | |
result += 1 | |
return result | |
DISPLACEMENT_TABLE = array.array( | |
'B', [get_displacement(x) for x in xrange(8192)]) | |
COMPRESSED_MASK = 1 << 15 | |
SIGNATURE_MASK = 3 << 12 | |
SIZE_MASK = (1 << 12) - 1 | |
TAG_MASKS = [(1 << i) for i in range(0, 8)] | |
def decompress_data(cdata, logger=None): | |
"""Decompresses the data.""" | |
if not logger: | |
lznt1_logger = logging.getLogger("ntfs.lznt1") | |
else: | |
lznt1_logger = logger.getChild("lznt1") | |
# Change to DEBUG to turn on module level debugging. | |
lznt1_logger.setLevel(logging.ERROR) | |
in_fd = cStringIO.StringIO(cdata) | |
output_fd = cStringIO.StringIO() | |
block_end = 0 | |
try: | |
while in_fd.tell() < len(cdata): | |
block_offset = in_fd.tell() | |
uncompressed_chunk_offset = output_fd.tell() | |
block_header = struct.unpack("<H", in_fd.read(2))[0] | |
lznt1_logger.debug("Header %#x @ %#x", block_header, block_offset) | |
if block_header & SIGNATURE_MASK != SIGNATURE_MASK: | |
break | |
size = (block_header & SIZE_MASK) | |
lznt1_logger.debug("Block size %s", size + 3) | |
block_end = block_offset + size + 3 | |
if block_header & COMPRESSED_MASK: | |
while in_fd.tell() < block_end: | |
header = ord(in_fd.read(1)) | |
lznt1_logger.debug("Tag %#x", header) | |
for mask in TAG_MASKS: | |
if in_fd.tell() >= block_end: | |
break | |
if header & mask: | |
pointer = struct.unpack("<H", in_fd.read(2))[0] | |
displacement = DISPLACEMENT_TABLE[ | |
output_fd.tell() - uncompressed_chunk_offset - 1] | |
symbol_offset = (pointer >> (12 - displacement)) + 1 | |
symbol_length = (pointer & (0xFFF >> displacement)) + 3 | |
output_fd.seek(-symbol_offset, 2) | |
data = output_fd.read(symbol_length) | |
# Pad the data to make it fit. | |
if 0 < len(data) < symbol_length: | |
data = data * (symbol_length / len(data) + 1) | |
data = data[:symbol_length] | |
output_fd.seek(0, 2) | |
lznt1_logger.debug( | |
"Wrote %s @ %s/%s: Phrase %s %s %x", | |
len(data), in_fd.tell(), | |
output_fd.tell(), symbol_length, symbol_offset, | |
pointer) | |
output_fd.write(data) | |
else: | |
data = in_fd.read(1) | |
lznt1_logger.debug("Symbol %#x", ord(data)) | |
output_fd.write(data) | |
else: | |
# Block is not compressed | |
data = in_fd.read(size + 1) | |
output_fd.write(data) | |
except: | |
pass | |
result = output_fd.getvalue() | |
return result |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment