blob: 1a57de939305989ade3da82920aca4af051e256b [file] [log] [blame]
* Common and shared functions used by multiple modules in the Mbed TLS
* library.
* Copyright (C) 2018, Arm Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
* 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
* 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.
* This file is part of Mbed TLS (
#include "mbedtls/config.h"
#include "mbedtls/platform_util.h"
#include <stddef.h>
#include <string.h>
* This implementation should never be optimized out by the compiler
* This implementation for mbedtls_platform_zeroize() was inspired from Colin
* Percival's blog article at:
* It uses a volatile function pointer to the standard memset(). Because the
* pointer is volatile the compiler expects it to change at
* any time and will not optimize out the call that could potentially perform
* other operations on the input buffer instead of just setting it to 0.
* Nevertheless, as pointed out by davidtgoldblatt on Hacker News
* (refer to for
* details), optimizations of the following form are still possible:
* if( memset_func != memset )
* memset_func( buf, 0, len );
* Note that it is extremely difficult to guarantee that
* mbedtls_platform_zeroize() will not be optimized out by aggressive compilers
* in a portable way. For this reason, Mbed TLS also provides the configuration
* option MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure
* mbedtls_platform_zeroize() to use a suitable implementation for their
* platform and needs.
static void * (* const volatile memset_func)( void *, int, size_t ) = memset;
void mbedtls_platform_zeroize( void *buf, size_t len )
memset_func( buf, 0, len );