Files
odiseectf/uncrackable/decryptAESCBC.py
2018-11-13 14:25:33 +01:00

86 lines
2.7 KiB
Python

import sys
import os
import getpass
from Crypto.Cipher import AES
# from Crypto.Random import get_random_bytes, random
# from Crypto.Util import Padding
from Crypto.Hash import MD5, SHA256
# generates key based on password
def generatekey():
password = getpass.getpass('Password for decryption: ')
h = MD5.new()
h.update(''.join(password))
return h.digest()
# calculates and return hash for message
def calculatehash(message):
h = SHA256.new()
h.update(message)
# use hexdigest to prevent problems with control characters
# e.g. \r in charcter 5, appends 4, then overwrites beginning of message with rest of digest
return h.hexdigest()
# check integrity and return cleartext or error message
def checkintegrity(decryptedcontent):
return calculatehash(decryptedcontent[0:-64]) == decryptedcontent[-64:]
# encrypts content in AES CBC mode
def decrypt_AES_CBC(inputfilename, encryptedContent):
# create encrypted filename, keep extension
outputfilename = inputfilename[0:inputfilename.find('.', len(inputfilename) - 5)] + '_decrypted' + inputfilename[
inputfilename.find(
'.'):len(
inputfilename)]
key = generatekey()
temp = open("hash34.txt", "r").read()
print(type(temp))
print(type(key))
decipher = AES.new(temp, AES.MODE_CBC)
decryptedcontent = decipher.decrypt(encryptedContent)
ivlength = 16
# remove iv and padding
decryptedcontent = decryptedcontent[ivlength:-ord(decryptedcontent[-1])]
# check Integrity and retain cleartext
if checkintegrity(decryptedcontent):
cleartext = decryptedcontent[0:-64]
else:
cleartext = 'Integrity check error'
# useful only for decrypted text files
# print(cleartext)
# write to file
outputfile = open(outputfilename, 'wb')
outputfile.write(cleartext)
outputfile.close()
for i in sys.argv[1:]:
inputfilename = i
try:
inputfile = open(inputfilename, 'rb')
except IOError:
print("File " + inputfilename + " not found, working directory: " + os.getcwd())
continue
else:
# if file opened, read content into variable
content = inputfile.read()
inputfile.close()
# apply symmetric encryption
decrypt_AES_CBC(inputfilename, content)
# encrypt_AES_ECB(inputfilename,content)