2 * Common and shared functions used by multiple modules in the Mbed TLS
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5 * Copyright (C) 2018, Arm Limited, All Rights Reserved
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6 * SPDX-License-Identifier: Apache-2.0
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8 * Licensed under the Apache License, Version 2.0 (the "License"); you may
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9 * not use this file except in compliance with the License.
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10 * You may obtain a copy of the License at
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12 * http://www.apache.org/licenses/LICENSE-2.0
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14 * Unless required by applicable law or agreed to in writing, software
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15 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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16 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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17 * See the License for the specific language governing permissions and
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18 * limitations under the License.
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20 * This file is part of Mbed TLS (https://tls.mbed.org)
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24 * Ensure gmtime_r is available even with -std=c99; must be defined before
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25 * config.h, which pulls in glibc's features.h. Harmless on other platforms.
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27 #if !defined(_POSIX_C_SOURCE)
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28 #define _POSIX_C_SOURCE 200112L
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31 #if !defined(MBEDTLS_CONFIG_FILE)
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32 #include "mbedtls/config.h"
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34 #include MBEDTLS_CONFIG_FILE
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37 #include "mbedtls/platform_util.h"
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38 #include "mbedtls/platform.h"
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39 #include "mbedtls/threading.h"
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44 #if !defined(MBEDTLS_PLATFORM_ZEROIZE_ALT)
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46 * This implementation should never be optimized out by the compiler
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48 * This implementation for mbedtls_platform_zeroize() was inspired from Colin
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49 * Percival's blog article at:
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51 * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html
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53 * It uses a volatile function pointer to the standard memset(). Because the
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54 * pointer is volatile the compiler expects it to change at
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55 * any time and will not optimize out the call that could potentially perform
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56 * other operations on the input buffer instead of just setting it to 0.
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57 * Nevertheless, as pointed out by davidtgoldblatt on Hacker News
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58 * (refer to http://www.daemonology.net/blog/2014-09-05-erratum.html for
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59 * details), optimizations of the following form are still possible:
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61 * if( memset_func != memset )
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62 * memset_func( buf, 0, len );
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64 * Note that it is extremely difficult to guarantee that
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65 * mbedtls_platform_zeroize() will not be optimized out by aggressive compilers
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66 * in a portable way. For this reason, Mbed TLS also provides the configuration
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67 * option MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure
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68 * mbedtls_platform_zeroize() to use a suitable implementation for their
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69 * platform and needs.
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71 static void * (* const volatile memset_func)( void *, int, size_t ) = memset;
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73 void mbedtls_platform_zeroize( void *buf, size_t len )
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75 memset_func( buf, 0, len );
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77 #endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */
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79 #if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)
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81 #if !defined(_WIN32) && (defined(unix) || \
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82 defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
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85 #endif /* !_WIN32 && (unix || __unix || __unix__ ||
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86 * (__APPLE__ && __MACH__)) */
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88 #if !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \
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89 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \
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90 _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) )
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92 * This is a convenience shorthand macro to avoid checking the long
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93 * preprocessor conditions above. Ideally, we could expose this macro in
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94 * platform_util.h and simply use it in platform_util.c, threading.c and
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95 * threading.h. However, this macro is not part of the Mbed TLS public API, so
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96 * we keep it private by only defining it in this file
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98 #if ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) )
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99 #define PLATFORM_UTIL_USE_GMTIME
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100 #endif /* ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) */
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102 #endif /* !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \
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103 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \
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104 _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) ) */
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106 struct tm *mbedtls_platform_gmtime_r( const mbedtls_time_t *tt,
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107 struct tm *tm_buf )
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109 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
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110 return( ( gmtime_s( tm_buf, tt ) == 0 ) ? tm_buf : NULL );
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111 #elif !defined(PLATFORM_UTIL_USE_GMTIME)
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112 return( gmtime_r( tt, tm_buf ) );
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116 #if defined(MBEDTLS_THREADING_C)
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117 if( mbedtls_mutex_lock( &mbedtls_threading_gmtime_mutex ) != 0 )
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119 #endif /* MBEDTLS_THREADING_C */
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125 memcpy( tm_buf, lt, sizeof( struct tm ) );
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128 #if defined(MBEDTLS_THREADING_C)
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129 if( mbedtls_mutex_unlock( &mbedtls_threading_gmtime_mutex ) != 0 )
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131 #endif /* MBEDTLS_THREADING_C */
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133 return( ( lt == NULL ) ? NULL : tm_buf );
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134 #endif /* _WIN32 && !EFIX64 && !EFI32 */
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136 #endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */
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