mirror of
https://github.com/PiBrewing/craftbeerpi4.git
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83 lines
2.8 KiB
Python
83 lines
2.8 KiB
Python
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from __future__ import absolute_import, division, print_function
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from cryptography import utils
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from cryptography.exceptions import (
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InvalidSignature,
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UnsupportedAlgorithm,
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_Reasons,
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)
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from cryptography.hazmat.primitives import constant_time
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from cryptography.hazmat.primitives.ciphers.modes import CBC
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class _CMACContext(object):
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def __init__(self, backend, algorithm, ctx=None):
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if not backend.cmac_algorithm_supported(algorithm):
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raise UnsupportedAlgorithm(
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"This backend does not support CMAC.",
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_Reasons.UNSUPPORTED_CIPHER,
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)
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self._backend = backend
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self._key = algorithm.key
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self._algorithm = algorithm
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self._output_length = algorithm.block_size // 8
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if ctx is None:
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registry = self._backend._cipher_registry
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adapter = registry[type(algorithm), CBC]
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evp_cipher = adapter(self._backend, algorithm, CBC)
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ctx = self._backend._lib.CMAC_CTX_new()
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self._backend.openssl_assert(ctx != self._backend._ffi.NULL)
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ctx = self._backend._ffi.gc(ctx, self._backend._lib.CMAC_CTX_free)
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key_ptr = self._backend._ffi.from_buffer(self._key)
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res = self._backend._lib.CMAC_Init(
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ctx,
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key_ptr,
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len(self._key),
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evp_cipher,
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self._backend._ffi.NULL,
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)
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self._backend.openssl_assert(res == 1)
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self._ctx = ctx
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algorithm = utils.read_only_property("_algorithm")
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def update(self, data):
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res = self._backend._lib.CMAC_Update(self._ctx, data, len(data))
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self._backend.openssl_assert(res == 1)
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def finalize(self):
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buf = self._backend._ffi.new("unsigned char[]", self._output_length)
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length = self._backend._ffi.new("size_t *", self._output_length)
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res = self._backend._lib.CMAC_Final(self._ctx, buf, length)
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self._backend.openssl_assert(res == 1)
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self._ctx = None
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return self._backend._ffi.buffer(buf)[:]
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def copy(self):
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copied_ctx = self._backend._lib.CMAC_CTX_new()
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copied_ctx = self._backend._ffi.gc(
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copied_ctx, self._backend._lib.CMAC_CTX_free
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)
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res = self._backend._lib.CMAC_CTX_copy(copied_ctx, self._ctx)
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self._backend.openssl_assert(res == 1)
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return _CMACContext(self._backend, self._algorithm, ctx=copied_ctx)
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def verify(self, signature):
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digest = self.finalize()
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if not constant_time.bytes_eq(digest, signature):
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raise InvalidSignature("Signature did not match digest.")
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