def flip_one_bit(s, offset=0, size=None):
""" flip one random bit of the string s, in a byte greater than or equal to offset and less
than offset+size. """
precondition(isinstance(s, binary_type))
if size is None:
size=len(s)-offset
i = randrange(offset, offset+size)
result = s[:i] + bchr(bord(s[i])^(0x01<<randrange(0, 8))) + s[i+1:]
assert result != s, "Internal error -- flip_one_bit() produced the same string as its input: %s == %s" % (result, s)
return result
def decrypt(secret, hash, data, file=False):
"""
Decrypt per telegram docs at https://core.telegram.org/passport.
Args:
secret (:obj:`str` or :obj:`bytes`): The encryption secret, either as bytes or as a
base64 encoded string.
hash (:obj:`str` or :obj:`bytes`): The hash, either as bytes or as a
base64 encoded string.
data (:obj:`str` or :obj:`bytes`): The data to decrypt, either as bytes or as a
base64 encoded string.
file (:obj:`bool`): Force data to be treated as raw data, instead of trying to
b64decode it.
Raises:
:class:`TelegramDecryptionError`: Given hash does not match hash of decrypted data.
Returns:
:obj:`bytes`: The decrypted data as bytes.
"""
# First make sure that if secret, hash, or data was base64 encoded, to decode it into bytes
try:
secret = b64decode(secret)
except (binascii.Error, TypeError):
pass
try:
hash = b64decode(hash)
except (binascii.Error, TypeError):
pass
if not file:
try:
data = b64decode(data)
except (binascii.Error, TypeError):
pass
# Make a SHA512 hash of secret + update
digest = Hash(SHA512(), backend=default_backend())
digest.update(secret + hash)
secret_hash_hash = digest.finalize()
# First 32 chars is our key, next 16 is the initialisation vector
key, iv = secret_hash_hash[:32], secret_hash_hash[32:32 + 16]
# Init a AES-CBC cipher and decrypt the data
cipher = Cipher(AES(key), CBC(iv), backend=default_backend())
decryptor = cipher.decryptor()
data = decryptor.update(data) + decryptor.finalize()
# Calculate SHA256 hash of the decrypted data
digest = Hash(SHA256(), backend=default_backend())
digest.update(data)
data_hash = digest.finalize()
# If the newly calculated hash did not match the one telegram gave us
if data_hash != hash:
# Raise a error that is caught inside telegram.PassportData and transformed into a warning
raise TelegramDecryptionError("Hashes are not equal! {} != {}".format(data_hash, hash))
# Return data without padding
return data[bord(data[0]):]