1 | /*
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2 | * Common and shared functions used by multiple modules in the Mbed TLS
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3 | * library.
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4 | *
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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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7 | *
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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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11 | *
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12 | * http://www.apache.org/licenses/LICENSE-2.0
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13 | *
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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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19 | *
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20 | * This file is part of Mbed TLS (https://tls.mbed.org)
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21 | */
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22 |
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23 | /*
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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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26 | */
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27 | #if !defined(_POSIX_C_SOURCE)
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28 | #define _POSIX_C_SOURCE 200112L
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29 | #endif
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30 |
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31 | #if !defined(MBEDTLS_CONFIG_FILE)
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32 | #include "mbedtls/config.h"
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33 | #else
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34 | #include MBEDTLS_CONFIG_FILE
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35 | #endif
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36 |
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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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40 |
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41 | #include <stddef.h>
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42 | #include <string.h>
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43 |
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44 | #if !defined(MBEDTLS_PLATFORM_ZEROIZE_ALT)
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45 | /*
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46 | * This implementation should never be optimized out by the compiler
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47 | *
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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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50 | *
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51 | * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html
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52 | *
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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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60 | *
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61 | * if( memset_func != memset )
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62 | * memset_func( buf, 0, len );
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63 | *
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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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70 | */
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71 | static void * (* const volatile memset_func)( void *, int, size_t ) = memset;
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72 |
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73 | void mbedtls_platform_zeroize( void *buf, size_t len )
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74 | {
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75 | memset_func( buf, 0, len );
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76 | }
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77 | #endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */
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78 |
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79 | #if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)
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80 | #include <time.h>
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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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83 | defined(__MACH__)))
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84 | #include <unistd.h>
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85 | #endif /* !_WIN32 && (unix || __unix || __unix__ ||
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86 | * (__APPLE__ && __MACH__)) */
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87 |
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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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91 | /*
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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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97 | */
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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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101 |
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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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105 |
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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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108 | {
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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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113 | #else
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114 | struct tm *lt;
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115 |
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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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118 | return( NULL );
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119 | #endif /* MBEDTLS_THREADING_C */
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120 |
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121 | lt = gmtime( tt );
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122 |
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123 | if( lt != NULL )
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124 | {
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125 | memcpy( tm_buf, lt, sizeof( struct tm ) );
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126 | }
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127 |
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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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130 | return( NULL );
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131 | #endif /* MBEDTLS_THREADING_C */
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132 |
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133 | return( ( lt == NULL ) ? NULL : tm_buf );
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134 | #endif /* _WIN32 && !EFIX64 && !EFI32 */
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135 | }
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136 | #endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */
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