def decrypt_file(self, in_file_path, out_file_path, password = None):
with open(in_file_path, 'rb') as in_file:
#If a password is provided, generate key and iv using salt from file.
if password is not None:
self._salt = in_file.read(32)
self.create_key_from_password(password)
#Key and iv have not been generated or provided, bail out
if self._key is None or self._iv is None:
return False
#Initialize encryption using key and iv
expanded_key = expandKey(self._key)
aes_cipher_256 = AESCipher(expanded_key)
aes_cbc_256 = CBCMode(aes_cipher_256)
aes_cbc_256.set_iv(self._iv)
#Read original file size
filesize = struct.unpack('!L',in_file.read(4))[0]
#Decrypt to eof
with open(out_file_path, 'wb') as out_file:
while 1:
in_data = in_file.read(16)
if not in_data:
self._salt = None
return True
else:
out_data = aes_cbc_256.decrypt_block(bytearray(in_data))
#At end of file, if end of original file is within < 16 bytes slice it out.
out_file.write(fix_bytes(
out_data[:filesize - out_file.tell()] if filesize - out_file.tell() < 16
else fix_bytes(out_data)))
