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# This file is dual licensed under the terms of the Apache License, Version # 2.0, and the BSD License. See the LICENSE file in the root of this repository # for complete details. from __future__ import absolute_import, division, print_function from cryptography import utils from cryptography.exceptions import ( AlreadyFinalized, UnsupportedAlgorithm, _Reasons ) from cryptography.hazmat.backends.interfaces import HMACBackend from cryptography.hazmat.primitives import hashes, mac @utils.register_interface(mac.MACContext) @utils.register_interface(hashes.HashContext) class HMAC(object): def __init__(self, key, algorithm, backend, ctx=None): if not isinstance(backend, HMACBackend): raise UnsupportedAlgorithm( "Backend object does not implement HMACBackend.", _Reasons.BACKEND_MISSING_INTERFACE ) if not isinstance(algorithm, hashes.HashAlgorithm): raise TypeError("Expected instance of hashes.HashAlgorithm.") self._algorithm = algorithm self._backend = backend self._key = key if ctx is None: self._ctx = self._backend.create_hmac_ctx(key, self.algorithm) else: self._ctx = ctx algorithm = utils.read_only_property("_algorithm") def update(self, data): if self._ctx is None: raise AlreadyFinalized("Context was already finalized.") if not isinstance(data, bytes): raise TypeError("data must be bytes.") self._ctx.update(data) def copy(self): if self._ctx is None: raise AlreadyFinalized("Context was already finalized.") return HMAC( self._key, self.algorithm, backend=self._backend, ctx=self._ctx.copy() ) def finalize(self): if self._ctx is None: raise AlreadyFinalized("Context was already finalized.") digest = self._ctx.finalize() self._ctx = None return digest def verify(self, signature): if not isinstance(signature, bytes): raise TypeError("signature must be bytes.") if self._ctx is None: raise AlreadyFinalized("Context was already finalized.") ctx, self._ctx = self._ctx, None ctx.verify(signature)