baseimage-tutorial-framework/lib/tfw/crypto.py

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# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
# All Rights Reserved. See LICENSE file for details.
from functools import wraps
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.hashes import SHA256
from cryptography.hazmat.primitives.hmac import HMAC as _HMAC
from cryptography.exceptions import InvalidSignature
class HMAC:
def __init__(self, key, message):
self.key = key
self.message = message
self._hmac = _HMAC(
key=key,
algorithm=SHA256(),
backend=default_backend()
)
def _reload_if_finalized(f):
# pylint: disable=no-self-argument,not-callable
@wraps(f)
def wrapped(instance, *args, **kwargs):
if getattr(instance, '_finalized', False):
instance.__init__(instance.key, instance.message)
ret_val = f(instance, *args, **kwargs)
setattr(instance, '_finalized', True)
return ret_val
return wrapped
@property
@_reload_if_finalized
def signature(self):
self._hmac.update(self.message)
signature = self._hmac.finalize()
return signature
@_reload_if_finalized
def verify(self, signature):
self._hmac.update(self.message)
try:
self._hmac.verify(signature)
return True
except InvalidSignature:
return False