diff --git a/common/mbedtls/platform_util_arm.c b/common/mbedtls/platform_util_arm.c new file mode 100644 index 00000000..13f3be00 --- /dev/null +++ b/common/mbedtls/platform_util_arm.c @@ -0,0 +1,68 @@ +/* + * 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 +#include + +#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. + */ + +void mbedtls_platform_zeroize( void *buf, size_t len ) +{ + memset( buf, 0, len ); +} +#endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */ diff --git a/common/mbedtls/platform_util_arm.h b/common/mbedtls/platform_util_arm.h new file mode 100644 index 00000000..79404ce6 --- /dev/null +++ b/common/mbedtls/platform_util_arm.h @@ -0,0 +1,64 @@ +/** + * \file platform_util.h + * + * \brief 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) + */ +#ifndef MBEDTLS_PLATFORM_UTIL_H +#define MBEDTLS_PLATFORM_UTIL_H + +#include + +#ifdef __cplusplus +extern "C" { +#endif + +/** + * \brief Securely zeroize a buffer + * + * The function is meant to wipe the data contained in a buffer so + * that it can no longer be recovered even if the program memory + * is later compromised. Call this function on sensitive data + * stored on the stack before returning from a function, and on + * sensitive data stored on the heap before freeing the heap + * object. + * + * It is extremely difficult to guarantee that calls to + * mbedtls_platform_zeroize() are not removed by aggressive + * compiler optimizations in a portable way. For this reason, Mbed + * TLS 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 + * + * \param buf Buffer to be zeroized + * \param len Length of the buffer in bytes + * + */ +void mbedtls_platform_zeroize( void *buf, size_t len ); + +#ifdef __cplusplus +} +#endif + +#endif /* MBEDTLS_PLATFORM_UTIL_H */