예제 #1
0
파일: set2.py 프로젝트: rohitg15/matasano
def c15(s):
  """
    This function attempts to check whether PKCS#7 padding is being used
    properly in the given string
    If the padding is wron, it raises an exception
  """
  # if PKCS#7 padding were used then the last byte must indicate the same
  pad_chr = s[-1]

  try:
    size = ord(pad_chr)
    Flag = True
    # the last size bytes must be equal to size for a valid PKCS#7 padding
    # if not, we have wrong padding here
    for i in range(size):
      if ord(s[-i-1]) != size:
        Flag = False
        break

    # raise exception if we don't have proper padding
    if Flag == True:
      print base.pkcs7_unpad(s)
      print s[:-ord(s[-1])]
    else:
      raise Exception


  except:
    # raise exception if any of the operations throws an exception
    print "exception!"
    raise Exception
예제 #2
0
파일: set2.py 프로젝트: rohitg15/matasano
def c10(filename):
    f = open(filename,"r")
    data = f.readlines()
    f.close()

    pad = "\x04"
    decoded_data = base.base64_to_hex(''.join(data).strip()).decode('hex')
    block_size = 16
    key = "YELLOW SUBMARINE"

    iv = ''.join(["\x00" for i in range(block_size)])
    blocks = [str(decoded_data[i*block_size : (i+1)*block_size]) for i in range(int(len(decoded_data)/block_size))]

    op = []
    size = len(blocks)
    for i in range(size):
        pt = base.AES_ECB_decrypt(blocks[i],key)
        res = base.equal_size_xor(bytearray(pt),bytearray(iv))
        res = base.bytearray_to_ASCII(res)
        op.append(res)
        iv = blocks[i]

    plaintext = base.pkcs7_unpad(''.join(op))
    print plaintext