projects / proxmark3-svn / blame
| Commit | Line | Data |
|---|---|---|
| 700d8687 OM |
1 | /* |
| 2 | * Common and shared functions used by multiple modules in the Mbed TLS | |
| 3 | * library. | |
| 4 | * | |
| 5 | * Copyright (C) 2018, Arm Limited, All Rights Reserved | |
| 6 | * SPDX-License-Identifier: GPL-2.0 | |
| 7 | * | |
| 8 | * This program is free software; you can redistribute it and/or modify | |
| 9 | * it under the terms of the GNU General Public License as published by | |
| 10 | * the Free Software Foundation; either version 2 of the License, or | |
| 11 | * (at your option) any later version. | |
| 12 | * | |
| 13 | * This program is distributed in the hope that it will be useful, | |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
| 16 | * GNU General Public License for more details. | |
| 17 | * | |
| 18 | * You should have received a copy of the GNU General Public License along | |
| 19 | * with this program; if not, write to the Free Software Foundation, Inc., | |
| 20 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 21 | * | |
| 22 | * This file is part of Mbed TLS (https://tls.mbed.org) | |
| 23 | */ | |
| 24 | ||
| 25 | #if !defined(MBEDTLS_CONFIG_FILE) | |
| 26 | #include "mbedtls/config.h" | |
| 27 | #else | |
| 28 | #include MBEDTLS_CONFIG_FILE | |
| 29 | #endif | |
| 30 | ||
| 31 | #include "mbedtls/platform_util.h" | |
| 32 | ||
| 33 | #include <stddef.h> | |
| 34 | #include <string.h> | |
| 35 | ||
| 36 | #if !defined(MBEDTLS_PLATFORM_ZEROIZE_ALT) | |
| 37 | /* | |
| 38 | * This implementation should never be optimized out by the compiler | |
| 39 | * | |
| 40 | * This implementation for mbedtls_platform_zeroize() was inspired from Colin | |
| 41 | * Percival's blog article at: | |
| 42 | * | |
| 43 | * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html | |
| 44 | * | |
| 45 | * It uses a volatile function pointer to the standard memset(). Because the | |
| 46 | * pointer is volatile the compiler expects it to change at | |
| 47 | * any time and will not optimize out the call that could potentially perform | |
| 48 | * other operations on the input buffer instead of just setting it to 0. | |
| 49 | * Nevertheless, as pointed out by davidtgoldblatt on Hacker News | |
| 50 | * (refer to http://www.daemonology.net/blog/2014-09-05-erratum.html for | |
| 51 | * details), optimizations of the following form are still possible: | |
| 52 | * | |
| 53 | * if( memset_func != memset ) | |
| 54 | * memset_func( buf, 0, len ); | |
| 55 | * | |
| 56 | * Note that it is extremely difficult to guarantee that | |
| 57 | * mbedtls_platform_zeroize() will not be optimized out by aggressive compilers | |
| 58 | * in a portable way. For this reason, Mbed TLS also provides the configuration | |
| 59 | * option MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure | |
| 60 | * mbedtls_platform_zeroize() to use a suitable implementation for their | |
| 61 | * platform and needs. | |
| 62 | */ | |
| 63 | static void * (* const volatile memset_func)( void *, int, size_t ) = memset; | |
| 64 | ||
| 65 | void mbedtls_platform_zeroize( void *buf, size_t len ) | |
| 66 | { | |
| 67 | memset_func( buf, 0, len ); | |
| 68 | } | |
| 69 | #endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */ |