108 lines
3.0 KiB
Python
108 lines
3.0 KiB
Python
# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
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# All Rights Reserved. See LICENSE file for details.
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from functools import wraps
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from base64 import b64encode, b64decode
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from copy import deepcopy
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from hashlib import md5
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from os import urandom, chmod
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from os.path import exists
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from stat import S_IRUSR, S_IWUSR, S_IXUSR
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from cryptography.hazmat.backends import default_backend
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from cryptography.hazmat.primitives.hashes import SHA256
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from cryptography.hazmat.primitives.hmac import HMAC as _HMAC
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from cryptography.exceptions import InvalidSignature
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from tfw.networking.serialization import message_bytes
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from tfw.decorators.lazy_property import lazy_property
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from tfw.config import TFWENV
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def message_checksum(message):
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return md5(message_bytes(message)).hexdigest()
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def sign_message(key, message):
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signature = message_signature(key, message)
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message['signature'] = b64encode(signature).decode()
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def message_signature(key, message):
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return HMAC(key, message_bytes(message)).signature
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def verify_message(key, message):
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message = deepcopy(message)
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try:
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signature_b64 = message.pop('signature')
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signature = b64decode(signature_b64)
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actual_signature = message_signature(key, message)
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return signature == actual_signature
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except KeyError:
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return False
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class KeyManager:
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def __init__(self):
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self.keyfile = TFWENV.AUTH_KEY
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if not exists(self.keyfile):
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self._init_auth_key()
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@lazy_property
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def auth_key(self):
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with open(self.keyfile, 'rb') as ifile:
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return ifile.read()
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def _init_auth_key(self):
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key = self.generate_key()
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with open(self.keyfile, 'wb') as ofile:
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ofile.write(key)
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self._chmod_700_keyfile()
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return key
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@staticmethod
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def generate_key():
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return urandom(32)
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def _chmod_700_keyfile(self):
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chmod(self.keyfile, S_IRUSR | S_IWUSR | S_IXUSR)
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class HMAC:
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def __init__(self, key, message):
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self.key = key
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self.message = message
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self._hmac = _HMAC(
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key=key,
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algorithm=SHA256(),
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backend=default_backend()
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)
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def _reload_if_finalized(f):
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# pylint: disable=no-self-argument,not-callable
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@wraps(f)
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def wrapped(instance, *args, **kwargs):
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if getattr(instance, '_finalized', False):
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instance.__init__(instance.key, instance.message)
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ret_val = f(instance, *args, **kwargs)
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setattr(instance, '_finalized', True)
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return ret_val
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return wrapped
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@property
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@_reload_if_finalized
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def signature(self):
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self._hmac.update(self.message)
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signature = self._hmac.finalize()
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return signature
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@_reload_if_finalized
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def verify(self, signature):
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self._hmac.update(self.message)
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try:
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self._hmac.verify(signature)
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return True
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except InvalidSignature:
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return False
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