/usr/lib/python2.7/dist-packages/rekall/plugins/darwin/WKdm.py is in python-rekall-core 1.6.0+dfsg-2.
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#
# Copyright 2014 Google Inc. All Rights Reserved.
#
# 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
"""A WKdm decompressor.
This code is very closely based on the C implementation by
Paul Wilson -- wilson@cs.utexas.edu
and
Scott F. Kaplan -- sfkaplan@cs.utexas.edu
from September 1997.
"""
__author__ = "Andreas Moser <amoser@google.com>"
import itertools
import math
import struct
import time
DICTIONARY_SIZE = 16
TAGS_AREA_OFFSET = 4
TAGS_AREA_SIZE = 64
NUM_LOW_BITS = 10
LOW_BITS_MASK = 0x3FF
ZERO_TAG = 0x0
PARTIAL_TAG = 0x1
MISS_TAG = 0x2
EXACT_TAG = 0x3
# Set up the dictionary before performing compression or
# decompression. Each element is loaded with some value, the
# high-bits version of that value, and a next pointer.
# these are the constants for the hash function lookup table.
# Only zero maps to zero. The rest of the tabale is the result
# of appending 17 randomizations of 1 to 14. Generated by a Scheme
# script in hash.scm.
HASH_LOOKUP_TABLE_CONTENTS = [
0, 13, 2, 14, 4, 3, 7, 5, 1, 9, 12, 6, 11, 10, 8, 15,
2, 3, 7, 5, 1, 15, 4, 9, 6, 12, 11, 8, 13, 14, 10, 3,
2, 12, 4, 13, 15, 7, 14, 8, 5, 6, 9, 10, 11, 1, 2, 10,
15, 8, 5, 11, 1, 9, 13, 6, 4, 14, 12, 3, 7, 4, 2, 10,
9, 7, 8, 3, 1, 11, 13, 5, 6, 12, 15, 14, 10, 12, 2, 8,
7, 9, 1, 11, 5, 14, 15, 6, 13, 4, 3, 3, 1, 12, 5, 2,
13, 4, 15, 6, 9, 11, 7, 14, 10, 8, 9, 5, 6, 15, 10, 11,
13, 4, 8, 1, 12, 2, 7, 14, 3, 7, 8, 10, 13, 9, 4, 5,
12, 2, 1, 15, 6, 14, 11, 3, 2, 9, 6, 7, 4, 15, 5, 14,
8, 10, 12, 3, 1, 11, 13, 11, 10, 3, 14, 2, 9, 6, 15, 7,
12, 1, 8, 5, 4, 13, 15, 3, 6, 9, 2, 1, 4, 14, 12, 11,
10, 13, 8, 5, 7, 8, 3, 9, 7, 6, 14, 10, 4, 13, 11, 1,
5, 15, 2, 12, 12, 13, 3, 5, 8, 11, 9, 7, 1, 10, 6, 2,
14, 15, 4, 9, 8, 2, 10, 1, 13, 6, 11, 5, 3, 7, 12, 14,
4, 15, 1, 13, 15, 12, 5, 4, 14, 11, 6, 2, 10, 3, 8, 7,
9, 6, 8, 3, 1, 5, 4, 15, 9, 7, 2, 13, 10, 12, 11, 14
]
# /***********************************************************************
# * THE PACKING ROUTINES
# */
def WK_pack_2bits(source_buf):
res = []
it = itertools.izip(*([iter(source_buf)] * 16))
for (in1, in2, in3, in4, in5, in6, in7, in8,
in9, in10, in11, in12, in13, in14, in15, in16) in it:
res.extend([
in1 + (in5 << 2) + (in9 << 4) + (in13 << 6),
in2 + (in6 << 2) + (in10 << 4) + (in14 << 6),
in3 + (in7 << 2) + (in11 << 4) + (in15 << 6),
in4 + (in8 << 2) + (in12 << 4) + (in16 << 6)
])
return res
# /* WK_pack_4bits()
# * Pack an even number of words holding 4-bit patterns in the low bits
# * of each byte into half as many words.
# * note: pad out the input with zeroes to an even number of words!
# */
def WK_pack_4bits(source_buf):
res = []
it = itertools.izip(*([iter(source_buf)] * 8))
for in1, in2, in3, in4, in5, in6, in7, in8 in it:
res.extend([
in1 + (in5 << 4),
in2 + (in6 << 4),
in3 + (in7 << 4),
in4 + (in8 << 4)
])
return res
# /* pack_3_tenbits()
# * Pack a sequence of three ten bit items into one word.
# * note: pad out the input with zeroes to an even number of words!
# */
def WK_pack_3_tenbits(source_buf):
packed_input = []
for in1, in2, in3 in itertools.izip(*([iter(source_buf)] * 3)):
packed_input.append(in1 | (in2 << 10) | (in3 << 20))
return packed_input
# /***************************************************************************
# * THE UNPACKING ROUTINES should GO HERE
# */
# /* WK_unpack_2bits takes any number of words containing 16 two-bit values
# * and unpacks them into four times as many words containg those
# * two bit values as bytes (with the low two bits of each byte holding
# * the actual value.
# */
and3_sh0 = []
and3_sh2 = []
and3_sh4 = []
and3_sh6 = []
and_f = []
sh4_and_f = []
for i in xrange(256):
and3_sh0.append((i >> 0) & 3)
and3_sh2.append((i >> 2) & 3)
and3_sh4.append((i >> 4) & 3)
and3_sh6.append((i >> 6) & 3)
and_f.append(i & 0xf)
sh4_and_f.append((i >> 4) & 0xf)
def WK_unpack_2bits(input_buf):
output = []
for in1, in2, in3, in4 in itertools.izip(*([iter(input_buf)] * 4)):
output.extend([
and3_sh0[in1], and3_sh0[in2], and3_sh0[in3], and3_sh0[in4],
and3_sh2[in1], and3_sh2[in2], and3_sh2[in3], and3_sh2[in4],
and3_sh4[in1], and3_sh4[in2], and3_sh4[in3], and3_sh4[in4],
and3_sh6[in1], and3_sh6[in2], and3_sh6[in3], and3_sh6[in4]
])
return output
# /* unpack four bits consumes any number of words (between input_buf
# * and input_end) holding 8 4-bit values per word, and unpacks them
# * into twice as many words, with each value in a separate byte.
# * (The four-bit values occupy the low halves of the bytes in the
# * result).
# */
def WK_unpack_4bits(input_buf):
output = []
for in1, in2, in3, in4 in itertools.izip(*([iter(input_buf)] * 4)):
output.extend([
and_f[in1],
and_f[in2],
and_f[in3],
and_f[in4],
sh4_and_f[in1],
sh4_and_f[in2],
sh4_and_f[in3],
sh4_and_f[in4]])
return output
# /* unpack_3_tenbits unpacks three 10-bit items from (the low 30 bits of)
# * a 32-bit word
# */
def WK_unpack_3_tenbits(input_buf):
output = []
for in1, in2, in3, in4 in itertools.izip(*([iter(input_buf)] * 4)):
output.extend([
in1 & 0x3FF, (in1 >> 10) & 0x3FF, (in1 >> 20) & 0x3FF,
in2 & 0x3FF, (in2 >> 10) & 0x3FF, (in2 >> 20) & 0x3FF,
in3 & 0x3FF, (in3 >> 10) & 0x3FF, (in3 >> 20) & 0x3FF,
in4 & 0x3FF, (in4 >> 10) & 0x3FF, (in4 >> 20) & 0x3FF
])
return output
def WKdm_compress(src_buf):
dictionary = []
for _ in xrange(DICTIONARY_SIZE):
dictionary.append((1, 0))
hashLookupTable = HASH_LOOKUP_TABLE_CONTENTS
tempTagsArray = []
tempQPosArray = []
# Holds words.
tempLowBitsArray = []
# Holds words.
full_patterns = []
input_words = struct.unpack("I" * (len(src_buf) / 4), src_buf)
for input_word in input_words:
# Equivalent to >> 10.
input_high_bits = input_word / 1024
dict_location = hashLookupTable[input_high_bits % 256]
dict_word, dict_high = dictionary[dict_location]
if (input_word == dict_word):
tempTagsArray.append(EXACT_TAG)
tempQPosArray.append(dict_location)
elif (input_word == 0):
tempTagsArray.append(ZERO_TAG)
else:
if input_high_bits == dict_high:
tempTagsArray.append(PARTIAL_TAG)
tempQPosArray.append(dict_location)
tempLowBitsArray.append((input_word % 1024))
else:
tempTagsArray.append(MISS_TAG)
full_patterns.append(input_word)
dictionary[dict_location] = (input_word, input_high_bits)
qpos_start = len(full_patterns) + TAGS_AREA_OFFSET + (len(src_buf) / 64)
packed_tags = WK_pack_2bits(tempTagsArray)
num_bytes_to_pack = len(tempQPosArray)
num_packed_words = math.ceil(num_bytes_to_pack / 8.0)
num_source_bytes = int(num_packed_words * 8)
tempQPosArray += [0] * (num_source_bytes - len(tempQPosArray))
packed_qp = WK_pack_4bits(tempQPosArray)
low_start = qpos_start + int(num_packed_words)
num_packed_words = len(tempLowBitsArray) / 3
# Align to 3 tenbits.
while len(tempLowBitsArray) % 3:
tempLowBitsArray.append(0)
packed_low = WK_pack_3_tenbits(tempLowBitsArray)
low_end = low_start + len(packed_low)
header = [0, qpos_start, low_start, low_end]
return struct.pack(
"IIII" + # header
"B" * len(packed_tags) +
"I" * len(full_patterns) +
"B" * len(packed_qp) +
"I" * len(packed_low),
* (header + packed_tags + full_patterns + packed_qp + packed_low))
def WKdm_decompress_apple(src_buf):
qpos_start, low_start, low_end = struct.unpack("III", src_buf[:12])
return _WKdm_decompress(src_buf, qpos_start, low_start, low_end, 12)
def WKdm_decompress(src_buf):
qpos_start, low_start, low_end = struct.unpack("III", src_buf[4:16])
return _WKdm_decompress(src_buf, qpos_start, low_start, low_end, 16)
def _WKdm_decompress(src_buf, qpos_start, low_start, low_end, header_size):
if max(qpos_start, low_start, low_end) > len(src_buf):
return None
if qpos_start > low_start or low_start > low_end:
return None
dictionary = [1] * DICTIONARY_SIZE
hashLookupTable = HASH_LOOKUP_TABLE_CONTENTS
tags_str = src_buf[header_size : header_size + 256]
tags_array = WK_unpack_2bits(struct.unpack("B" * len(tags_str), tags_str))
qpos_str = src_buf[qpos_start * 4:low_start * 4]
tempQPosArray = WK_unpack_4bits(
struct.unpack("B" * len(qpos_str), qpos_str))
lowbits_str = src_buf[low_start * 4:low_end * 4]
num_lowbits_bytes = len(lowbits_str)
num_lowbits_words = num_lowbits_bytes / 4
num_packed_lowbits = num_lowbits_words * 3
rem = len(lowbits_str) % 16
if rem:
lowbits_str += "\x00" * (16 - rem)
packed_lowbits = struct.unpack("I" * (len(lowbits_str) / 4), lowbits_str)
tempLowBitsArray = WK_unpack_3_tenbits(packed_lowbits)[:num_packed_lowbits]
patterns_str = src_buf[256 + header_size:qpos_start * 4]
full_patterns = struct.unpack("I" * (len(patterns_str) / 4), patterns_str)
p_tempQPosArray = iter(tempQPosArray)
p_tempLowBitsArray = iter(tempLowBitsArray)
p_full_patterns = iter(full_patterns)
output = []
for tag in tags_array:
if tag == ZERO_TAG:
output.append(0)
elif tag == EXACT_TAG:
output.append(dictionary[p_tempQPosArray.next()])
elif tag == PARTIAL_TAG:
dict_idx = p_tempQPosArray.next()
temp = ((dictionary[dict_idx] / 1024) * 1024)
temp += p_tempLowBitsArray.next()
dictionary[dict_idx] = temp
output.append(temp)
elif tag == MISS_TAG:
missed_word = p_full_patterns.next()
dict_idx = hashLookupTable[(missed_word / 1024) % 256]
dictionary[dict_idx] = missed_word
output.append(missed_word)
for p in [p_tempQPosArray, p_tempLowBitsArray, p_full_patterns]:
for leftover in p:
if leftover != 0:
# Something went wrong, we have leftover data to decompress.
return None
return struct.pack("I" * len(output), *output)
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