class Decoder:
MODES = {'GCM': 8}
MODE_LENGTH = 1
def __init__(self, password, image_folder_path):
self.image_folder_path = image_folder_path
self.mode = None
self._gcm = None
self._password = password
self._data_length = 0
self.extractor = Extractor(image_folder_path)
def get_header_length(self):
return GCM.get_iv_length() + GCM.get_salt_length()
def decode_header(self, raw_header):
# assume raw_header is bytearray of values
salt_end = GCM.get_salt_length()
gcm_end = salt_end + GCM.get_iv_length()
password_salt = bytes(raw_header[:salt_end])
iv = bytes(raw_header[salt_end:gcm_end])
self._gcm = GCM(iv=iv, password_salt=password_salt)
self._gcm.make_key(self._password)
del self._password
def get_tag(self, raw_data):
tag = bytes(raw_data[-GCM.get_tag_length():])
self._gcm.set_tag(tag)
def decrypt_and_save_data(self, raw_data, destination_file):
decrypted = self._gcm.decrypt(
raw_data[self.get_header_length():-GCM.get_tag_length()])
# with open("temp", "wb") as f:
# f.write(decrypted)
self._gcm.decrypt_finalize()
with open(destination_file, "wb") as f:
f.write(decrypted)
def decode_file(self, file_path):
raw_data = self.extractor.load_images()
# with open("decode-test", "wb") as f:
# f.write(raw_data)
raw_header = raw_data[:self.get_header_length()]
self.decode_header(raw_header)
self.get_tag(raw_data)
self.decrypt_and_save_data(raw_data, file_path)
