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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 UnsupportedAlgorithm, _Reasons
from cryptography.hazmat.primitives import hashes
@utils.register_interface(hashes.HashContext)
class _HashContext(object):
def __init__(self, backend, algorithm, ctx=None):
self._algorithm = algorithm
self._backend = backend
if ctx is None:
ctx = self._backend._lib.Cryptography_EVP_MD_CTX_new()
ctx = self._backend._ffi.gc(
ctx, self._backend._lib.Cryptography_EVP_MD_CTX_free
)
evp_md = self._backend._evp_md_from_algorithm(algorithm)
if evp_md == self._backend._ffi.NULL:
raise UnsupportedAlgorithm(
"{} is not a supported hash on this backend.".format(
algorithm.name),
_Reasons.UNSUPPORTED_HASH
)
res = self._backend._lib.EVP_DigestInit_ex(ctx, evp_md,
self._backend._ffi.NULL)
self._backend.openssl_assert(res != 0)
self._ctx = ctx
algorithm = utils.read_only_property("_algorithm")
def copy(self):
copied_ctx = self._backend._lib.Cryptography_EVP_MD_CTX_new()
copied_ctx = self._backend._ffi.gc(
copied_ctx, self._backend._lib.Cryptography_EVP_MD_CTX_free
)
res = self._backend._lib.EVP_MD_CTX_copy_ex(copied_ctx, self._ctx)
self._backend.openssl_assert(res != 0)
return _HashContext(self._backend, self.algorithm, ctx=copied_ctx)
def update(self, data):
data_ptr = self._backend._ffi.from_buffer(data)
res = self._backend._lib.EVP_DigestUpdate(
self._ctx, data_ptr, len(data)
)
self._backend.openssl_assert(res != 0)
def finalize(self):
if isinstance(self.algorithm, hashes.ExtendableOutputFunction):
# extendable output functions use a different finalize
return self._finalize_xof()
else:
buf = self._backend._ffi.new("unsigned char[]",
self._backend._lib.EVP_MAX_MD_SIZE)
outlen = self._backend._ffi.new("unsigned int *")
res = self._backend._lib.EVP_DigestFinal_ex(self._ctx, buf, outlen)
self._backend.openssl_assert(res != 0)
self._backend.openssl_assert(
outlen[0] == self.algorithm.digest_size
)
return self._backend._ffi.buffer(buf)[:outlen[0]]
def _finalize_xof(self):
buf = self._backend._ffi.new("unsigned char[]",
self.algorithm.digest_size)
res = self._backend._lib.EVP_DigestFinalXOF(
self._ctx, buf, self.algorithm.digest_size
)
self._backend.openssl_assert(res != 0)
return self._backend._ffi.buffer(buf)[:self.algorithm.digest_size]
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