Lockpick/source/mbedtls/lib/platform_util.c

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2018-12-08 02:17:01 +01:00
/*
* Common and shared functions used by multiple modules in the Mbed TLS
* library.
*
* Copyright (C) 2018, Arm Limited, All Rights Reserved
* SPDX-License-Identifier: GPL-2.0
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* This file is part of Mbed TLS (https://tls.mbed.org)
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#include "mbedtls/platform_util.h"
#include <stddef.h>
#include <string.h>
#if !defined(MBEDTLS_PLATFORM_ZEROIZE_ALT)
/*
* 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:
*
* http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html
*
* 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 http://www.daemonology.net/blog/2014-09-05-erratum.html 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 );
}
#endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */