mirror of
https://github.com/PiBrewing/craftbeerpi4.git
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77 lines
2.9 KiB
Python
77 lines
2.9 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, hashes
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@utils.register_interface(hashes.HashContext)
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class _HMACContext(object):
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def __init__(self, backend, key, algorithm, ctx=None):
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self._algorithm = algorithm
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self._backend = backend
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if ctx is None:
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ctx = self._backend._lib.HMAC_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.HMAC_CTX_free)
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evp_md = self._backend._evp_md_from_algorithm(algorithm)
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if evp_md == self._backend._ffi.NULL:
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raise UnsupportedAlgorithm(
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"{} is not a supported hash on this backend".format(
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algorithm.name
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),
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_Reasons.UNSUPPORTED_HASH,
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)
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key_ptr = self._backend._ffi.from_buffer(key)
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res = self._backend._lib.HMAC_Init_ex(
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ctx, key_ptr, len(key), evp_md, self._backend._ffi.NULL
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)
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self._backend.openssl_assert(res != 0)
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self._ctx = ctx
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self._key = key
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algorithm = utils.read_only_property("_algorithm")
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def copy(self):
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copied_ctx = self._backend._lib.HMAC_CTX_new()
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self._backend.openssl_assert(copied_ctx != self._backend._ffi.NULL)
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copied_ctx = self._backend._ffi.gc(
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copied_ctx, self._backend._lib.HMAC_CTX_free
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)
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res = self._backend._lib.HMAC_CTX_copy(copied_ctx, self._ctx)
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self._backend.openssl_assert(res != 0)
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return _HMACContext(
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self._backend, self._key, self.algorithm, ctx=copied_ctx
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)
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def update(self, data):
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data_ptr = self._backend._ffi.from_buffer(data)
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res = self._backend._lib.HMAC_Update(self._ctx, data_ptr, len(data))
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self._backend.openssl_assert(res != 0)
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def finalize(self):
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buf = self._backend._ffi.new(
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"unsigned char[]", self._backend._lib.EVP_MAX_MD_SIZE
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)
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outlen = self._backend._ffi.new("unsigned int *")
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res = self._backend._lib.HMAC_Final(self._ctx, buf, outlen)
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self._backend.openssl_assert(res != 0)
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self._backend.openssl_assert(outlen[0] == self.algorithm.digest_size)
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return self._backend._ffi.buffer(buf)[: outlen[0]]
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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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