python反编译教程之2048小游戏实例

一.背景

一道ctf题，通过破解2048游戏获得flag

游戏的规则很简单，需要控制所有方块向同一个方向运动，两个相同数字方块撞在一起之后合并成为他们的和，每次操作之后会随机生成一个2或者4，最终得到一个“2048”的方块就算胜利了。

二.工具准备

1.pyinstxtractor.py脚本用于反编译python

脚本内容如下

from __future__ import print_function
import os
import struct
import marshal
import zlib
import sys
import imp
import types
from uuid import uuid4 as uniquename


class CTOCEntry:
 def __init__(self, position, cmprsdDataSize, uncmprsdDataSize, cmprsFlag, typeCmprsData, name):
 self.position = position
 self.cmprsdDataSize = cmprsdDataSize
 self.uncmprsdDataSize = uncmprsdDataSize
 self.cmprsFlag = cmprsFlag
 self.typeCmprsData = typeCmprsData
 self.name = name


class PyInstArchive:
 PYINST20_COOKIE_SIZE = 24  # For pyinstaller 2.0
 PYINST21_COOKIE_SIZE = 24 + 64 # For pyinstaller 2.1+
 MAGIC = b'MEI\014\013\012\013\016' # Magic number which identifies pyinstaller

 def __init__(self, path):
 self.filePath = path


 def open(self):
 try:
  self.fPtr = open(self.filePath, 'rb')
  self.fileSize = os.stat(self.filePath).st_size
 except:
  print('[*] Error: Could not open {0}'.format(self.filePath))
  return False
 return True


 def close(self):
 try:
  self.fPtr.close()
 except:
  pass


 def checkFile(self):
 print('[*] Processing {0}'.format(self.filePath))
 # Check if it is a 2.0 archive
 self.fPtr.seek(self.fileSize - self.PYINST20_COOKIE_SIZE, os.SEEK_SET)
 magicFromFile = self.fPtr.read(len(self.MAGIC))

 if magicFromFile == self.MAGIC:
  self.pyinstVer = 20 # pyinstaller 2.0
  print('[*] Pyinstaller version: 2.0')
  return True

 # Check for pyinstaller 2.1+ before bailing out
 self.fPtr.seek(self.fileSize - self.PYINST21_COOKIE_SIZE, os.SEEK_SET)
 magicFromFile = self.fPtr.read(len(self.MAGIC))

 if magicFromFile == self.MAGIC:
  print('[*] Pyinstaller version: 2.1+')
  self.pyinstVer = 21 # pyinstaller 2.1+
  return True

 print('[*] Error : Unsupported pyinstaller version or not a pyinstaller archive')
 return False


 def getCArchiveInfo(self):
 try:
  if self.pyinstVer == 20:
  self.fPtr.seek(self.fileSize - self.PYINST20_COOKIE_SIZE, os.SEEK_SET)

  # Read CArchive cookie
  (magic, lengthofPackage, toc, tocLen, self.pyver) = \
  struct.unpack('!8siiii', self.fPtr.read(self.PYINST20_COOKIE_SIZE))

  elif self.pyinstVer == 21:
  self.fPtr.seek(self.fileSize - self.PYINST21_COOKIE_SIZE, os.SEEK_SET)

  # Read CArchive cookie
  (magic, lengthofPackage, toc, tocLen, self.pyver, pylibname) = \
  struct.unpack('!8siiii64s', self.fPtr.read(self.PYINST21_COOKIE_SIZE))

 except:
  print('[*] Error : The file is not a pyinstaller archive')
  return False

 print('[*] Python version: {0}'.format(self.pyver))

 # Overlay is the data appended at the end of the PE
 self.overlaySize = lengthofPackage
 self.overlayPos = self.fileSize - self.overlaySize
 self.tableOfContentsPos = self.overlayPos + toc
 self.tableOfContentsSize = tocLen

 print('[*] Length of package: {0} bytes'.format(self.overlaySize))
 return True


 def parseTOC(self):
 # Go to the table of contents
 self.fPtr.seek(self.tableOfContentsPos, os.SEEK_SET)

 self.tocList = []
 parsedLen = 0

 # Parse table of contents
 while parsedLen < self.tableOfContentsSize:
  (entrySize, ) = struct.unpack('!i', self.fPtr.read(4))
  nameLen = struct.calcsize('!iiiiBc')

  (entryPos, cmprsdDataSize, uncmprsdDataSize, cmprsFlag, typeCmprsData, name) = \
  struct.unpack( \
  '!iiiBc{0}s'.format(entrySize - nameLen), \
  self.fPtr.read(entrySize - 4))

  name = name.decode('utf-8').rstrip('\0')
  if len(name) == 0:
  name = str(uniquename())
  print('[!] Warning: Found an unamed file in CArchive. Using random name {0}'.format(name))

  self.tocList.append( \
    CTOCEntry(   \
     self.overlayPos + entryPos, \
     cmprsdDataSize,  \
     uncmprsdDataSize,  \
     cmprsFlag,   \
     typeCmprsData,  \
     name   \
    ))

  parsedLen += entrySize
 print('[*] Found {0} files in CArchive'.format(len(self.tocList)))



 def extractFiles(self):
 print('[*] Beginning extraction...please standby')
 extractionDir = os.path.join(os.getcwd(), os.path.basename(self.filePath) + '_extracted')

 if not os.path.exists(extractionDir):
  os.mkdir(extractionDir)

 os.chdir(extractionDir)

 for entry in self.tocList:
  basePath = os.path.dirname(entry.name)
  if basePath != '':
  # Check if path exists, create if not
  if not os.path.exists(basePath):
   os.makedirs(basePath)

  self.fPtr.seek(entry.position, os.SEEK_SET)
  data = self.fPtr.read(entry.cmprsdDataSize)

  if entry.cmprsFlag == 1:
  data = zlib.decompress(data)
  # Malware may tamper with the uncompressed size
  # Comment out the assertion in such a case
  assert len(data) == entry.uncmprsdDataSize # Sanity Check

  with open(entry.name, 'wb') as f:
  f.write(data)

  if entry.typeCmprsData == b's':
  print('[+] Possible entry point: {0}'.format(entry.name))

  elif entry.typeCmprsData == b'z' or entry.typeCmprsData == b'Z':
  self._extractPyz(entry.name)


 def _extractPyz(self, name):
 dirName = name + '_extracted'
 # Create a directory for the contents of the pyz
 if not os.path.exists(dirName):
  os.mkdir(dirName)

 with open(name, 'rb') as f:
  pyzMagic = f.read(4)
  assert pyzMagic == b'PYZ\0' # Sanity Check

  pycHeader = f.read(4) # Python magic value

  if imp.get_magic() != pycHeader:
  print('[!] Warning: The script is running in a different python version than the one used to build the executable')
  print(' Run this script in Python{0} to prevent extraction errors(if any) during unmarshalling'.format(self.pyver))

  (tocPosition, ) = struct.unpack('!i', f.read(4))
  f.seek(tocPosition, os.SEEK_SET)

  try:
  toc = marshal.load(f)
  except:
  print('[!] Unmarshalling FAILED. Cannot extract {0}. Extracting remaining files.'.format(name))
  return

  print('[*] Found {0} files in PYZ archive'.format(len(toc)))

  # From pyinstaller 3.1+ toc is a list of tuples
  if type(toc) == list:
  toc = dict(toc)

  for key in toc.keys():
  (ispkg, pos, length) = toc[key]
  f.seek(pos, os.SEEK_SET)

  fileName = key
  try:
   # for Python > 3.3 some keys are bytes object some are str object
   fileName = key.decode('utf-8')
  except:
   pass

  # Make sure destination directory exists, ensuring we keep inside dirName
  destName = os.path.join(dirName, fileName.replace("..", "__"))
  destDirName = os.path.dirname(destName)
  if not os.path.exists(destDirName):
   os.makedirs(destDirName)

  try:
   data = f.read(length)
   data = zlib.decompress(data)
  except:
   print('[!] Error: Failed to decompress {0}, probably encrypted. Extracting as is.'.format(fileName))
   open(destName + '.pyc.encrypted', 'wb').write(data)
   continue

  with open(destName + '.pyc', 'wb') as pycFile:
   pycFile.write(pycHeader) # Write pyc magic
   pycFile.write(b'\0' * 4) # Write timestamp
   if self.pyver >= 33:
   pycFile.write(b'\0' * 4) # Size parameter added in Python 3.3
   pycFile.write(data)


def main():
 if len(sys.argv) < 2:
 print('[*] Usage: pyinstxtractor.py <filename>')

 else:
 arch = PyInstArchive(sys.argv[1])
 if arch.open():
  if arch.checkFile():
  if arch.getCArchiveInfo():
   arch.parseTOC()
   arch.extractFiles()
   arch.close()
   print('[*] Successfully extracted pyinstaller archive: {0}'.format(sys.argv[1]))
   print('')
   print('You can now use a python decompiler on the pyc files within the extracted directory')
   return

  arch.close()


if __name__ == '__main__':
 main()

2.winhex用于编辑16进制的软件

压缩包已上传至博主资源，下载地址：https://blog.csdn.net/qq_50216270?type=download

三.反编译

1.放置脚本

将脚本和待编译的exe文件放在同一路径下后，在路径框中输入cmd打开终端

2.运行脚本

在终端中输入python后输入脚本名和待反编译exe文件名

编译成功后会在原路径生成如下文件夹

3.找到软件名文件和struct文件

4.托入winhex进行对比

5.将struct多出的那一行复制到puzzle前面

6.更改其后缀为.pyc

7.安装第三方库uncompyle

8.python版本为3.8以下可以调用uncompyle

对应路径终端输入uncompyle6 puzzle.pyc > puzzle.py

9.python版本为3.8以上可以选择在线工具（.pyc>.py）

https://tool.lu/pyc/

10.最后可以得到puzzle.py文件

代码如下

#!/usr/bin/env python
# visit http://tool.lu/pyc/ for more information
import random
from tkinter import Frame, Label, CENTER
import logic
import constants as c

class GameGrid(Frame):
 
 def __init__(self):
 Frame.__init__(self)
 self.grid()
 self.master.title('C1CTF2019')
 self.master.bind('<Key>', self.key_down)
 self.commands = {
  c.KEY_J: logic.down,
  c.KEY_K: logic.up,
  c.KEY_L: logic.right,
  c.KEY_H: logic.left,
  c.KEY_RIGHT_ALT: logic.right,
  c.KEY_LEFT_ALT: logic.left,
  c.KEY_DOWN_ALT: logic.down,
  c.KEY_UP_ALT: logic.up,
  c.KEY_RIGHT: logic.right,
  c.KEY_LEFT: logic.left,
  c.KEY_DOWN: logic.down,
  c.KEY_UP: logic.up }
 self.grid_cells = []
 self.init_grid()
 self.init_matrix()
 self.update_grid_cells()
 self.mainloop()

 
 def init_grid(self):
 background = Frame(self, c.BACKGROUND_COLOR_GAME, c.SIZE, c.SIZE, **('bg', 'width', 'height'))
 background.grid()
 for i in range(c.GRID_LEN):
  grid_row = []
  for j in range(c.GRID_LEN):
  cell = Frame(background, c.BACKGROUND_COLOR_CELL_EMPTY, c.SIZE / c.GRID_LEN, c.SIZE / c.GRID_LEN, **('bg', 'width', 'height'))
  cell.grid(i, j, c.GRID_PADDING, c.GRID_PADDING, **('row', 'column', 'padx', 'pady'))
  t = Label(cell, '', c.BACKGROUND_COLOR_CELL_EMPTY, CENTER, c.FONT, 5, 2, **('master', 'text', 'bg', 'justify', 'font', 'width', 'height'))
  t.grid()
  grid_row.append(t)
  
  self.grid_cells.append(grid_row)
 

 
 def gen(self):
 return random.randint(0, c.GRID_LEN - 1)

 
 def init_matrix(self):
 self.matrix = logic.new_game(4)
 self.history_matrixs = list()
 self.matrix = logic.add_two(self.matrix)
 self.matrix = logic.add_two(self.matrix)

 
 def update_grid_cells(self):
 for i in range(c.GRID_LEN):
  for j in range(c.GRID_LEN):
  new_number = self.matrix[i][j]
  if new_number == 0:
   self.grid_cells[i][j].configure('', c.BACKGROUND_COLOR_CELL_EMPTY, **('text', 'bg'))
   continue
  self.grid_cells[i][j].configure(str(new_number), c.BACKGROUND_COLOR_DICT[new_number], c.CELL_COLOR_DICT[new_number], **('text', 'bg', 'fg'))
  
 
 self.update_idletasks()

 
 def key_down(self, event):
 key = repr(event.char)
 if key == c.KEY_BACK and len(self.history_matrixs) > 1:
  self.matrix = self.history_matrixs.pop()
  self.update_grid_cells()
  print('back on step total step:', len(self.history_matrixs))
 elif key in self.commands:
  (self.matrix, done) = self.commands[repr(event.char)](self.matrix)
  if done:
  self.matrix = logic.add_two(self.matrix)
  self.history_matrixs.append(self.matrix)
  self.update_grid_cells()
  done = False
  if logic.game_state(self.matrix) == 'win':
   self.grid_cells[1][0].configure('C1CTF', c.BACKGROUND_COLOR_CELL_EMPTY, **('text', 'bg'))
   self.grid_cells[1][1].configure('{2048', c.BACKGROUND_COLOR_CELL_EMPTY, **('text', 'bg'))
   self.grid_cells[1][2].configure('_1s_', c.BACKGROUND_COLOR_CELL_EMPTY, **('text', 'bg'))
   self.grid_cells[1][3].configure('fun}', c.BACKGROUND_COLOR_CELL_EMPTY, **('text', 'bg'))
  if logic.game_state(self.matrix) == 'lose':
   self.grid_cells[1][1].configure('You', c.BACKGROUND_COLOR_CELL_EMPTY, **('text', 'bg'))
   self.grid_cells[1][2].configure('Lost!', c.BACKGROUND_COLOR_CELL_EMPTY, **('text', 'bg'))

 
 def generate_next(self):
 index = (self.gen(), self.gen())
 while self.matrix[index[0]][index[1]] != 0:
  index = (self.gen(), self.gen())
 self.matrix[index[0]][index[1]] = 2


gamegrid = GameGrid()

11.找到flag大公告成

总结

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