# 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]