[柏鹭杯 2021]baby_python Wp keyword：Pyinstaller密码破解 z3计算矩阵乘法

思路

• 解题大致思路

  首先放进DIE分析程序，发现是PyInstaller打包的，我们就拿，pyinstxtractor去解决包

• 这里注意程序是python3.7的，所以要提前用python3.7去解包，解包发现加密了，PyInstaller加密的key会一起打包，所以是不安全的，我们可以pyimod00_crypto_key.pyc里面看到key的值

  key = 'f8c0870eba862579'
  ​

• 然后我们就可以写一个解密的程序

  from Crypto.Cipher import AES
  from Crypto.Util import Counter
  import zlib
  
  CRYPT_BLOCK_SIZE = 16
  
  # key obtained from pyimod00_crypto_key
  key = bytes('f8c0870eba862579', 'utf-8')
  
  inf = open('baby_python.baby_core.pyc.encrypted', 'rb') # encrypted file input
  outf = open('baby_python.baby_core.pyc', 'wb') # output file
  
  # Initialization vector
  iv = inf.read(CRYPT_BLOCK_SIZE)
  
  ctr = Counter.new(128, initial_value=int.from_bytes(iv, byteorder='big'))
  
  cipher = AES.new(key, AES.MODE_CTR, counter=ctr)
  
  # Decrypt and decompress
  plaintext = zlib.decompress(cipher.decrypt(inf.read()))
  
  # Write pyc header
  # The header below is for Python 3.8
  outf.write(b'\x42\x0d\x0d\x0a\x00\x00\x00\x00\x70\x79\x69\x30\x10\x01\x00\x00')
  
  # Write decrypted data
  outf.write(plaintext)
  
  inf.close()
  outf.close()
  ​
              
  AI代码解释
              
                  
              
          

  解密后生成baby_python.baby_core.pyc，拿去反编译然后发现是一个简单的矩阵乘法嗷，乘法结果md5加密就是答案，我们写一个z3去解决

EXP

• 具体攻击代码

• from z3 import *
  co = [
          [
              158,
              195,
              205,
              229,
              213,
              238,
              211,
              198,
              190,
              226,
              135,
              119,
              145,
              205,
              113,
              122],
          [
              234,
              256,
              185,
              253,
              244,
              134,
              102,
              117,
              190,
              106,
              131,
              205,
              198,
              234,
              162,
              218],
          [
              164,
              164,
              209,
              200,
              168,
              226,
              189,
              151,
              253,
              241,
              232,
              151,
              193,
              119,
              226,
              193],
          [
              213,
              117,
              151,
              103,
              249,
              148,
              103,
              213,
              218,
              222,
              104,
              228,
              100,
              206,
              218,
              177],
          [
              217,
              202,
              126,
              214,
              195,
              125,
              144,
              105,
              152,
              118,
              167,
              137,
              171,
              173,
              206,
              240],
          [
              160,
              134,
              131,
              135,
              186,
              213,
              146,
              129,
              125,
              139,
              174,
              205,
              177,
              240,
              194,
              181],
          [
              183,
              213,
              127,
              136,
              136,
              209,
              199,
              191,
              150,
              218,
              160,
              111,
              191,
              226,
              154,
              191],
          [
              247,
              188,
              210,
              219,
              179,
              204,
              155,
              220,
              215,
              127,
              225,
              214,
              195,
              162,
              214,
              239],
          [
              108,
              112,
              104,
              133,
              178,
              138,
              110,
              176,
              232,
              124,
              193,
              239,
              131,
              138,
              161,
              218],
          [
              140,
              213,
              142,
              181,
              179,
              173,
              203,
              208,
              184,
              129,
              129,
              119,
              122,
              152,
              186,
              124],
          [
              105,
              205,
              124,
              142,
              175,
              184,
              234,
              119,
              195,
              218,
              141,
              122,
              202,
              202,
              190,
              178],
          [
              183,
              178,
              256,
              124,
              241,
              132,
              163,
              209,
              204,
              104,
              175,
              211,
              196,
              136,
              158,
              210],
          [
              224,
              144,
              189,
              106,
              177,
              251,
              206,
              163,
              167,
              144,
              208,
              254,
              117,
              253,
              100,
              106],
          [
              251,
              251,
              136,
              170,
              145,
              177,
              175,
              124,
              193,
              188,
              193,
              198,
              208,
              171,
              151,
              230],
          [
              143,
              200,
              143,
              150,
              243,
              148,
              136,
              213,
              161,
              224,
              170,
              208,
              185,
              117,
              189,
              242],
          [
              234,
              188,
              226,
              194,
              248,
              168,
              250,
              244,
              166,
              106,
              113,
              218,
              209,
              220,
              158,
              228]]
  r = [
        472214,
        480121,
        506256,
        449505,
        433390,
        435414,
        453899,
        536361,
        423332,
        427624,
        440268,
        488759,
        469049,
        484574,
        480266,
        522818]
  s = Solver()
  v = [Int('v[%d]'%i) for i in range(16)]
  for i in range(16):
    s.add(v[i]>0)
  for i in range(16):
    s.add(v[i]<1000)
  
  for i in range(16):
    vv = 0
    for j in range(16):
      vv += co[i][j] * v[j]
    s.add(vv=r[i])
  print(s.check())
  print(s.solver())
  m = s.model()
  for i in range(16):
    print(m[v[i]],end = '')
  ​
              
  AI代码解释
              
                  
              
          

总结

• 对该题的考点总结

  学会对一般的Pyinstaller加密打包程序的破解

  会z3解密矩阵乘法