1 /* SPDX-License-Identifier: Apache-2.0 */ 2 /* 3 * Common and shared functions used by multiple modules in the Mbed TLS 4 * library. 5 * 6 * Copyright (C) 2018, Arm Limited, All Rights Reserved 7 * 8 * Licensed under the Apache License, Version 2.0 (the "License"); you may 9 * not use this file except in compliance with the License. 10 * You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, software 15 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 16 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 17 * See the License for the specific language governing permissions and 18 * limitations under the License. 19 * 20 * This file is part of Mbed TLS (https://tls.mbed.org) 21 */ 22 23 /* 24 * Ensure gmtime_r is available even with -std=c99; must be defined before 25 * config.h, which pulls in glibc's features.h. Harmless on other platforms. 26 */ 27 #if !defined(_POSIX_C_SOURCE) 28 #define _POSIX_C_SOURCE 200112L 29 #endif 30 31 #if !defined(MBEDTLS_CONFIG_FILE) 32 #include "mbedtls/config.h" 33 #else 34 #include MBEDTLS_CONFIG_FILE 35 #endif 36 37 #include "mbedtls/platform_util.h" 38 #include "mbedtls/platform.h" 39 #include "mbedtls/threading.h" 40 41 #include <stddef.h> 42 #include <string.h> 43 44 #if !defined(MBEDTLS_PLATFORM_ZEROIZE_ALT) 45 /* 46 * This implementation should never be optimized out by the compiler 47 * 48 * This implementation for mbedtls_platform_zeroize() was inspired from Colin 49 * Percival's blog article at: 50 * 51 * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html 52 * 53 * It uses a volatile function pointer to the standard memset(). Because the 54 * pointer is volatile the compiler expects it to change at 55 * any time and will not optimize out the call that could potentially perform 56 * other operations on the input buffer instead of just setting it to 0. 57 * Nevertheless, as pointed out by davidtgoldblatt on Hacker News 58 * (refer to http://www.daemonology.net/blog/2014-09-05-erratum.html for 59 * details), optimizations of the following form are still possible: 60 * 61 * if( memset_func != memset ) 62 * memset_func( buf, 0, len ); 63 * 64 * Note that it is extremely difficult to guarantee that 65 * mbedtls_platform_zeroize() will not be optimized out by aggressive compilers 66 * in a portable way. For this reason, Mbed TLS also provides the configuration 67 * option MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure 68 * mbedtls_platform_zeroize() to use a suitable implementation for their 69 * platform and needs. 70 */ 71 static void * (* const volatile memset_func)( void *, int, size_t ) = memset; 72 73 void mbedtls_platform_zeroize( void *buf, size_t len ) 74 { 75 memset_func( buf, 0, len ); 76 } 77 #endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */ 78 79 #if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT) 80 #include <time.h> 81 #if !defined(_WIN32) && (defined(unix) || \ 82 defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \ 83 defined(__MACH__))) 84 #include <unistd.h> 85 #endif /* !_WIN32 && (unix || __unix || __unix__ || 86 * (__APPLE__ && __MACH__)) */ 87 88 #if !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \ 89 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \ 90 _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) ) 91 /* 92 * This is a convenience shorthand macro to avoid checking the long 93 * preprocessor conditions above. Ideally, we could expose this macro in 94 * platform_util.h and simply use it in platform_util.c, threading.c and 95 * threading.h. However, this macro is not part of the Mbed TLS public API, so 96 * we keep it private by only defining it in this file 97 */ 98 #if ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) 99 #define PLATFORM_UTIL_USE_GMTIME 100 #endif /* ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) */ 101 102 #endif /* !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \ 103 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \ 104 _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) ) */ 105 106 struct tm *mbedtls_platform_gmtime_r( const mbedtls_time_t *tt, 107 struct tm *tm_buf ) 108 { 109 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) 110 return( ( gmtime_s( tm_buf, tt ) == 0 ) ? tm_buf : NULL ); 111 #elif !defined(PLATFORM_UTIL_USE_GMTIME) 112 return( gmtime_r( tt, tm_buf ) ); 113 #else 114 struct tm *lt; 115 116 #if defined(MBEDTLS_THREADING_C) 117 if( mbedtls_mutex_lock( &mbedtls_threading_gmtime_mutex ) != 0 ) 118 return( NULL ); 119 #endif /* MBEDTLS_THREADING_C */ 120 121 lt = gmtime( tt ); 122 123 if( lt != NULL ) 124 { 125 memcpy( tm_buf, lt, sizeof( struct tm ) ); 126 } 127 128 #if defined(MBEDTLS_THREADING_C) 129 if( mbedtls_mutex_unlock( &mbedtls_threading_gmtime_mutex ) != 0 ) 130 return( NULL ); 131 #endif /* MBEDTLS_THREADING_C */ 132 133 return( ( lt == NULL ) ? NULL : tm_buf ); 134 #endif /* _WIN32 && !EFIX64 && !EFI32 */ 135 } 136 #endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */ 137