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import itertools
import binascii
import string
class crc32_reverse_class(object):
def __init__(self, crc32, length, tbl=string.printable,
poly=0xEDB88320, accum=0):
self.char_set = set(map(ord, tbl))
self.crc32 = crc32
self.length = length
self.poly = poly
self.accum = accum
self.table = []
self.table_reverse = []
def init_tables(self, poly, reverse=True):
for i in range(256):
for j in range(8):
if i & 1:
i >>= 1
i ^= poly
else:
i >>= 1
self.table.append(i)
assert len(self.table) == 256, "table is wrong size"
if reverse:
found_none = set()
found_multiple = set()
for i in range(256):
found = []
for j in range(256):
if self.table[j] >> 24 == i:
found.append(j)
self.table_reverse.append(tuple(found))
if not found:
found_none.add(i)
elif len(found) > 1:
found_multiple.add(i)
assert len(self.table_reverse) == 256, "reverse table is wrong size"
def rangess(self, i):
return ', '.join(map(lambda x: '[{0},{1}]'.format(*x), self.ranges(i)))
def ranges(self, i):
for kg in itertools.groupby(enumerate(i), lambda x: x[1] - x[0]):
g = list(kg[1])
yield g[0][7], g[-1][8]
def calc(self, data, accum=0):
accum = ~accum
for b in data:
accum = self.table[(accum ^ b) & 0xFF] ^ ((accum >> 8) & 0x00FFFFFF)
accum = ~accum
return accum & 0xFFFFFFFF
def findReverse(self, desired, accum):
solutions = set()
accum = ~accum
stack = [(~desired,)]
while stack:
node = stack.pop()
for j in self.table_reverse[(node[0] >> 24) & 0xFF]:
if len(node) == 4:
a = accum
data = []
node = node[1:] + (j,)
for i in range(3, -1, -1):
data.append((a ^ node[i]) & 0xFF)
a >>= 8
a ^= self.table[node[i]]
solutions.add(tuple(data))
else:
stack.append(((node[0] ^ self.table[j]) << 8,) + node[1:] + (j,))
return solutions
def dfs(self, length, outlist=['']):
tmp_list = []
if length == 0:
return outlist
for list_item in outlist:
tmp_list.extend([list_item + chr(x) for x in self.char_set])
return self.dfs(length - 1, tmp_list)
def run_reverse(self):
self.init_tables(self.poly)
desired = self.crc32
accum = self.accum
if self.length >= 4:
patches = self.findReverse(desired, accum)
for patch in patches:
checksum = self.calc(patch, accum)
print 'verification checksum: 0x{0:08x} ({1})'.format(
checksum, 'OK' if checksum == desired else 'ERROR')
for item in self.dfs(self.length - 4):
patch = map(ord, item)
patches = self.findReverse(desired, self.calc(patch, accum))
for last_4_bytes in patches:
if all(p in self.char_set for p in last_4_bytes):
patch.extend(last_4_bytes)
print '[find]: {1} ({0})'.format(
'OK' if self.calc(patch, accum) == desired else 'ERROR', ''.join(map(chr, patch)))
else:
for item in self.dfs(self.length):
if crc32(item) == desired:
print '[find]: {0} (OK)'.format(item)
def crc32_reverse(crc32, length, char_set=string.printable,
poly=0xEDB88320, accum=0):
'''
:param crc32: the crc32 you wnat to reverse
:param length: the plaintext length
:param char_set: char_set
:param poly: poly , default 0xEDB88320
:param accum: accum , default 0
:return: none
'''
obj = crc32_reverse_class(crc32, length, char_set, poly, accum)
obj.run_reverse()
def crc32(s):
'''
:param s: the string to calculate the crc32
:return: the crc32
'''
return binascii.crc32(s) & 0xffffffff
from my_crc32 import *
l=[0x251dee02,
0xb890530f,
0x6e6b39df,
0x50f684c3,
0xde41b551,
0x24bd35b6,
0xcef2eda8,
0xba2b1745,
0x1f4c7ea9,
0x58b2bfa9,
0x251dee02,
0xe0f81f1e,
0xbd6fbd41,
0x7342a1f6,
0x665648e9,
0xe7c594b3,
0xa60ffdd0,
0xce2ce80b,
0x22459f2d,
0x6f8a6539,
0x2073a2e4,
0x52fa60a8,
0x80410dda,
0xb7c68f27,
0x6e6b39df,
0xbd598041,
0xaa145d64,
0x16da6b3b,
0x7dd590bc,
0xb9eef5a1,
0xf0b958f0,
0x445a43f7,
0x8bd55271,
0xc0340fe2,
0xc0cd9ee5,
0x7fc7de58,
0x53bfec8a,
0x99b5537b,
0xd68019af,
0x73d7ee30,
0x5fbd3f5e]
for k in l:
crc32_reverse(k,5)
print '======='
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