1 /* 2 * Common and shared functions used by multiple modules in the Mbed TLS 3 * library. 4 * 5 * Copyright The Mbed TLS Contributors 6 * SPDX-License-Identifier: Apache-2.0 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 21 /* 22 * Ensure gmtime_r is available even with -std=c99; must be defined before 23 * config.h, which pulls in glibc's features.h. Harmless on other platforms. 24 */ 25 #if !defined(_POSIX_C_SOURCE) 26 #define _POSIX_C_SOURCE 200112L 27 #endif 28 29 #include "common.h" 30 31 #include "mbedtls/platform_util.h" 32 #include "mbedtls/platform.h" 33 #include "mbedtls/threading.h" 34 35 #include <stddef.h> 36 #include <string.h> 37 38 #if !defined(MBEDTLS_PLATFORM_ZEROIZE_ALT) 39 /* 40 * This implementation should never be optimized out by the compiler 41 * 42 * This implementation for mbedtls_platform_zeroize() was inspired from Colin 43 * Percival's blog article at: 44 * 45 * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html 46 * 47 * It uses a volatile function pointer to the standard memset(). Because the 48 * pointer is volatile the compiler expects it to change at 49 * any time and will not optimize out the call that could potentially perform 50 * other operations on the input buffer instead of just setting it to 0. 51 * Nevertheless, as pointed out by davidtgoldblatt on Hacker News 52 * (refer to http://www.daemonology.net/blog/2014-09-05-erratum.html for 53 * details), optimizations of the following form are still possible: 54 * 55 * if( memset_func != memset ) 56 * memset_func( buf, 0, len ); 57 * 58 * Note that it is extremely difficult to guarantee that 59 * mbedtls_platform_zeroize() will not be optimized out by aggressive compilers 60 * in a portable way. For this reason, Mbed TLS also provides the configuration 61 * option MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure 62 * mbedtls_platform_zeroize() to use a suitable implementation for their 63 * platform and needs. 64 */ 65 static void * (* const volatile memset_func)( void *, int, size_t ) = memset; 66 67 void mbedtls_platform_zeroize( void *buf, size_t len ) 68 { 69 MBEDTLS_INTERNAL_VALIDATE( len == 0 || buf != NULL ); 70 71 if( len > 0 ) 72 memset_func( buf, 0, len ); 73 } 74 #endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */ 75 76 #if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT) 77 #include <time.h> 78 #if !defined(_WIN32) && (defined(unix) || \ 79 defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \ 80 defined(__MACH__))) 81 #include <unistd.h> 82 #endif /* !_WIN32 && (unix || __unix || __unix__ || 83 * (__APPLE__ && __MACH__)) */ 84 85 #if !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \ 86 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \ 87 _POSIX_THREAD_SAFE_FUNCTIONS >= 200112L ) ) 88 /* 89 * This is a convenience shorthand macro to avoid checking the long 90 * preprocessor conditions above. Ideally, we could expose this macro in 91 * platform_util.h and simply use it in platform_util.c, threading.c and 92 * threading.h. However, this macro is not part of the Mbed TLS public API, so 93 * we keep it private by only defining it in this file 94 */ 95 #if ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) 96 #define PLATFORM_UTIL_USE_GMTIME 97 #endif /* ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) */ 98 99 #endif /* !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \ 100 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \ 101 _POSIX_THREAD_SAFE_FUNCTIONS >= 200112L ) ) */ 102 103 struct tm *mbedtls_platform_gmtime_r( const mbedtls_time_t *tt, 104 struct tm *tm_buf ) 105 { 106 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) 107 return( ( gmtime_s( tm_buf, tt ) == 0 ) ? tm_buf : NULL ); 108 #elif !defined(PLATFORM_UTIL_USE_GMTIME) 109 return( gmtime_r( tt, tm_buf ) ); 110 #else 111 struct tm *lt; 112 113 #if defined(MBEDTLS_THREADING_C) 114 if( mbedtls_mutex_lock( &mbedtls_threading_gmtime_mutex ) != 0 ) 115 return( NULL ); 116 #endif /* MBEDTLS_THREADING_C */ 117 118 lt = gmtime( tt ); 119 120 if( lt != NULL ) 121 { 122 memcpy( tm_buf, lt, sizeof( struct tm ) ); 123 } 124 125 #if defined(MBEDTLS_THREADING_C) 126 if( mbedtls_mutex_unlock( &mbedtls_threading_gmtime_mutex ) != 0 ) 127 return( NULL ); 128 #endif /* MBEDTLS_THREADING_C */ 129 130 return( ( lt == NULL ) ? NULL : tm_buf ); 131 #endif /* _WIN32 && !EFIX64 && !EFI32 */ 132 } 133 #endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */ 134