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:
/
usr
/
lib64
/
python3.6
/
site-packages
/
cryptography
/
hazmat
/
backends
/
openssl
/
Filename :
cmac.py
back
Copy
# 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 ( InvalidSignature, UnsupportedAlgorithm, _Reasons, ) from cryptography.hazmat.primitives import constant_time, mac from cryptography.hazmat.primitives.ciphers.modes import CBC @utils.register_interface(mac.MACContext) class _CMACContext(object): def __init__(self, backend, algorithm, ctx=None): if not backend.cmac_algorithm_supported(algorithm): raise UnsupportedAlgorithm( "This backend does not support CMAC.", _Reasons.UNSUPPORTED_CIPHER, ) self._backend = backend self._key = algorithm.key self._algorithm = algorithm self._output_length = algorithm.block_size // 8 if ctx is None: registry = self._backend._cipher_registry adapter = registry[type(algorithm), CBC] evp_cipher = adapter(self._backend, algorithm, CBC) ctx = self._backend._lib.CMAC_CTX_new() self._backend.openssl_assert(ctx != self._backend._ffi.NULL) ctx = self._backend._ffi.gc(ctx, self._backend._lib.CMAC_CTX_free) key_ptr = self._backend._ffi.from_buffer(self._key) res = self._backend._lib.CMAC_Init( ctx, key_ptr, len(self._key), evp_cipher, self._backend._ffi.NULL, ) self._backend.openssl_assert(res == 1) self._ctx = ctx algorithm = utils.read_only_property("_algorithm") def update(self, data): res = self._backend._lib.CMAC_Update(self._ctx, data, len(data)) self._backend.openssl_assert(res == 1) def finalize(self): buf = self._backend._ffi.new("unsigned char[]", self._output_length) length = self._backend._ffi.new("size_t *", self._output_length) res = self._backend._lib.CMAC_Final(self._ctx, buf, length) self._backend.openssl_assert(res == 1) self._ctx = None return self._backend._ffi.buffer(buf)[:] def copy(self): copied_ctx = self._backend._lib.CMAC_CTX_new() copied_ctx = self._backend._ffi.gc( copied_ctx, self._backend._lib.CMAC_CTX_free ) res = self._backend._lib.CMAC_CTX_copy(copied_ctx, self._ctx) self._backend.openssl_assert(res == 1) return _CMACContext(self._backend, self._algorithm, ctx=copied_ctx) def verify(self, signature): digest = self.finalize() if not constant_time.bytes_eq(digest, signature): raise InvalidSignature("Signature did not match digest.")