| # Licensed under the Apache License, Version 2.0 (the "License"); |
| # you may not use this file except in compliance with the License. |
| # You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, software |
| # distributed under the License is distributed on an "AS IS" BASIS, |
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or |
| # implied. |
| # See the License for the specific language governing permissions and |
| # limitations under the License. |
| |
| from __future__ import absolute_import, division, print_function |
| |
| |
| from cryptography import utils |
| from cryptography.exceptions import UnsupportedAlgorithm, _Reasons |
| from cryptography.hazmat.primitives import interfaces |
| |
| |
| @utils.register_interface(interfaces.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.EVP_MD_CTX_create() |
| ctx = self._backend._ffi.gc(ctx, |
| self._backend._lib.EVP_MD_CTX_destroy) |
| evp_md = self._backend._lib.EVP_get_digestbyname( |
| algorithm.name.encode("ascii")) |
| if evp_md == self._backend._ffi.NULL: |
| raise UnsupportedAlgorithm( |
| "{0} 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) |
| assert res != 0 |
| |
| self._ctx = ctx |
| |
| algorithm = utils.read_only_property("_algorithm") |
| |
| def copy(self): |
| copied_ctx = self._backend._lib.EVP_MD_CTX_create() |
| copied_ctx = self._backend._ffi.gc( |
| copied_ctx, self._backend._lib.EVP_MD_CTX_destroy |
| ) |
| res = self._backend._lib.EVP_MD_CTX_copy_ex(copied_ctx, self._ctx) |
| assert res != 0 |
| return _HashContext(self._backend, self.algorithm, ctx=copied_ctx) |
| |
| def update(self, data): |
| res = self._backend._lib.EVP_DigestUpdate(self._ctx, data, len(data)) |
| assert res != 0 |
| |
| def finalize(self): |
| 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) |
| assert res != 0 |
| assert outlen[0] == self.algorithm.digest_size |
| res = self._backend._lib.EVP_MD_CTX_cleanup(self._ctx) |
| assert res == 1 |
| return self._backend._ffi.buffer(buf)[:outlen[0]] |
