platform_util.h

00001 /**
00002  * \file platform_util.h
00003  *
00004  * \brief Common and shared functions used by multiple modules in the Mbed TLS
00005  *        library.
00006  */
00007 /*
00008  *  Copyright (C) 2018, Arm Limited, All Rights Reserved
00009  *  SPDX-License-Identifier: Apache-2.0
00010  *
00011  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
00012  *  not use this file except in compliance with the License.
00013  *  You may obtain a copy of the License at
00014  *
00015  *  http://www.apache.org/licenses/LICENSE-2.0
00016  *
00017  *  Unless required by applicable law or agreed to in writing, software
00018  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00019  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00020  *  See the License for the specific language governing permissions and
00021  *  limitations under the License.
00022  *
00023  *  This file is part of Mbed TLS (https://tls.mbed.org)
00024  */
00025 #ifndef MBEDTLS_PLATFORM_UTIL_H
00026 #define MBEDTLS_PLATFORM_UTIL_H
00027 
00028 #if !defined(MBEDTLS_CONFIG_FILE)
00029 #include "mbedtls/config.h"
00030 #else
00031 #include MBEDTLS_CONFIG_FILE
00032 #endif
00033 
00034 #include <stddef.h>
00035 #if defined(MBEDTLS_HAVE_TIME_DATE)
00036 #include "mbedtls/platform_time.h"
00037 #include <time.h>
00038 #endif /* MBEDTLS_HAVE_TIME_DATE */
00039 
00040 #ifdef __cplusplus
00041 extern "C" {
00042 #endif
00043 
00044 /**
00045  * \brief       Securely zeroize a buffer
00046  *
00047  *              The function is meant to wipe the data contained in a buffer so
00048  *              that it can no longer be recovered even if the program memory
00049  *              is later compromised. Call this function on sensitive data
00050  *              stored on the stack before returning from a function, and on
00051  *              sensitive data stored on the heap before freeing the heap
00052  *              object.
00053  *
00054  *              It is extremely difficult to guarantee that calls to
00055  *              mbedtls_platform_zeroize() are not removed by aggressive
00056  *              compiler optimizations in a portable way. For this reason, Mbed
00057  *              TLS provides the configuration option
00058  *              MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure
00059  *              mbedtls_platform_zeroize() to use a suitable implementation for
00060  *              their platform and needs
00061  *
00062  * \param buf   Buffer to be zeroized
00063  * \param len   Length of the buffer in bytes
00064  *
00065  */
00066 void mbedtls_platform_zeroize( void *buf, size_t len );
00067 
00068 #if defined(MBEDTLS_HAVE_TIME_DATE)
00069 /**
00070  * \brief      Platform-specific implementation of gmtime_r()
00071  *
00072  *             The function is a thread-safe abstraction that behaves
00073  *             similarly to the gmtime_r() function from Unix/POSIX.
00074  *
00075  *             Mbed TLS will try to identify the underlying platform and
00076  *             make use of an appropriate underlying implementation (e.g.
00077  *             gmtime_r() for POSIX and gmtime_s() for Windows). If this is
00078  *             not possible, then gmtime() will be used. In this case, calls
00079  *             from the library to gmtime() will be guarded by the mutex
00080  *             mbedtls_threading_gmtime_mutex if MBEDTLS_THREADING_C is
00081  *             enabled. It is recommended that calls from outside the library
00082  *             are also guarded by this mutex.
00083  *
00084  *             If MBEDTLS_PLATFORM_GMTIME_R_ALT is defined, then Mbed TLS will
00085  *             unconditionally use the alternative implementation for
00086  *             mbedtls_platform_gmtime_r() supplied by the user at compile time.
00087  *
00088  * \param tt     Pointer to an object containing time (in seconds) since the
00089  *               epoch to be converted
00090  * \param tm_buf Pointer to an object where the results will be stored
00091  *
00092  * \return      Pointer to an object of type struct tm on success, otherwise
00093  *              NULL
00094  */
00095 struct tm *mbedtls_platform_gmtime_r( const mbedtls_time_t *tt,
00096                                       struct tm *tm_buf );
00097 #endif /* MBEDTLS_HAVE_TIME_DATE */
00098 
00099 #ifdef __cplusplus
00100 }
00101 #endif
00102 
00103 #endif /* MBEDTLS_PLATFORM_UTIL_H */