1 /** 2 * \file platform_util.h 3 * 4 * \brief Common and shared functions used by multiple modules in the Mbed TLS 5 * library. 6 */ 7 /* 8 * Copyright The Mbed TLS Contributors 9 * SPDX-License-Identifier: Apache-2.0 10 * 11 * Licensed under the Apache License, Version 2.0 (the "License"); you may 12 * not use this file except in compliance with the License. 13 * You may obtain a copy of the License at 14 * 15 * http://www.apache.org/licenses/LICENSE-2.0 16 * 17 * Unless required by applicable law or agreed to in writing, software 18 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 19 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 20 * See the License for the specific language governing permissions and 21 * limitations under the License. 22 */ 23 #ifndef MBEDTLS_PLATFORM_UTIL_H 24 #define MBEDTLS_PLATFORM_UTIL_H 25 26 #include "mbedtls/build_info.h" 27 28 #include <stddef.h> 29 #if defined(MBEDTLS_HAVE_TIME_DATE) 30 #include "mbedtls/platform_time.h" 31 #include <time.h> 32 #endif /* MBEDTLS_HAVE_TIME_DATE */ 33 34 #ifdef __cplusplus 35 extern "C" { 36 #endif 37 38 /* Internal macros meant to be called only from within the library. */ 39 #define MBEDTLS_INTERNAL_VALIDATE_RET(cond, ret) do { } while (0) 40 #define MBEDTLS_INTERNAL_VALIDATE(cond) do { } while (0) 41 42 /* Internal helper macros for deprecating API constants. */ 43 #if !defined(MBEDTLS_DEPRECATED_REMOVED) 44 #if defined(MBEDTLS_DEPRECATED_WARNING) 45 #define MBEDTLS_DEPRECATED __attribute__((deprecated)) 46 MBEDTLS_DEPRECATED typedef char const *mbedtls_deprecated_string_constant_t; 47 #define MBEDTLS_DEPRECATED_STRING_CONSTANT(VAL) \ 48 ((mbedtls_deprecated_string_constant_t) (VAL)) 49 MBEDTLS_DEPRECATED typedef int mbedtls_deprecated_numeric_constant_t; 50 #define MBEDTLS_DEPRECATED_NUMERIC_CONSTANT(VAL) \ 51 ((mbedtls_deprecated_numeric_constant_t) (VAL)) 52 #else /* MBEDTLS_DEPRECATED_WARNING */ 53 #define MBEDTLS_DEPRECATED 54 #define MBEDTLS_DEPRECATED_STRING_CONSTANT(VAL) VAL 55 #define MBEDTLS_DEPRECATED_NUMERIC_CONSTANT(VAL) VAL 56 #endif /* MBEDTLS_DEPRECATED_WARNING */ 57 #endif /* MBEDTLS_DEPRECATED_REMOVED */ 58 59 /* Implementation of the check-return facility. 60 * See the user documentation in mbedtls_config.h. 61 * 62 * Do not use this macro directly to annotate function: instead, 63 * use one of MBEDTLS_CHECK_RETURN_CRITICAL or MBEDTLS_CHECK_RETURN_TYPICAL 64 * depending on how important it is to check the return value. 65 */ 66 #if !defined(MBEDTLS_CHECK_RETURN) 67 #if defined(__GNUC__) 68 #define MBEDTLS_CHECK_RETURN __attribute__((__warn_unused_result__)) 69 #elif defined(_MSC_VER) && _MSC_VER >= 1700 70 #include <sal.h> 71 #define MBEDTLS_CHECK_RETURN _Check_return_ 72 #else 73 #define MBEDTLS_CHECK_RETURN 74 #endif 75 #endif 76 77 /** Critical-failure function 78 * 79 * This macro appearing at the beginning of the declaration of a function 80 * indicates that its return value should be checked in all applications. 81 * Omitting the check is very likely to indicate a bug in the application 82 * and will result in a compile-time warning if #MBEDTLS_CHECK_RETURN 83 * is implemented for the compiler in use. 84 * 85 * \note The use of this macro is a work in progress. 86 * This macro may be added to more functions in the future. 87 * Such an extension is not considered an API break, provided that 88 * there are near-unavoidable circumstances under which the function 89 * can fail. For example, signature/MAC/AEAD verification functions, 90 * and functions that require a random generator, are considered 91 * return-check-critical. 92 */ 93 #define MBEDTLS_CHECK_RETURN_CRITICAL MBEDTLS_CHECK_RETURN 94 95 /** Ordinary-failure function 96 * 97 * This macro appearing at the beginning of the declaration of a function 98 * indicates that its return value should be generally be checked in portable 99 * applications. Omitting the check will result in a compile-time warning if 100 * #MBEDTLS_CHECK_RETURN is implemented for the compiler in use and 101 * #MBEDTLS_CHECK_RETURN_WARNING is enabled in the compile-time configuration. 102 * 103 * You can use #MBEDTLS_IGNORE_RETURN to explicitly ignore the return value 104 * of a function that is annotated with #MBEDTLS_CHECK_RETURN. 105 * 106 * \note The use of this macro is a work in progress. 107 * This macro will be added to more functions in the future. 108 * Eventually this should appear before most functions returning 109 * an error code (as \c int in the \c mbedtls_xxx API or 110 * as ::psa_status_t in the \c psa_xxx API). 111 */ 112 #if defined(MBEDTLS_CHECK_RETURN_WARNING) 113 #define MBEDTLS_CHECK_RETURN_TYPICAL MBEDTLS_CHECK_RETURN 114 #else 115 #define MBEDTLS_CHECK_RETURN_TYPICAL 116 #endif 117 118 /** Benign-failure function 119 * 120 * This macro appearing at the beginning of the declaration of a function 121 * indicates that it is rarely useful to check its return value. 122 * 123 * This macro has an empty expansion. It exists for documentation purposes: 124 * a #MBEDTLS_CHECK_RETURN_OPTIONAL annotation indicates that the function 125 * has been analyzed for return-check usefulness, whereas the lack of 126 * an annotation indicates that the function has not been analyzed and its 127 * return-check usefulness is unknown. 128 */ 129 #define MBEDTLS_CHECK_RETURN_OPTIONAL 130 131 /** \def MBEDTLS_IGNORE_RETURN 132 * 133 * Call this macro with one argument, a function call, to suppress a warning 134 * from #MBEDTLS_CHECK_RETURN due to that function call. 135 */ 136 #if !defined(MBEDTLS_IGNORE_RETURN) 137 /* GCC doesn't silence the warning with just (void)(result). 138 * (void)!(result) is known to work up at least up to GCC 10, as well 139 * as with Clang and MSVC. 140 * 141 * https://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Non_002dbugs.html 142 * https://stackoverflow.com/questions/40576003/ignoring-warning-wunused-result 143 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425#c34 144 */ 145 #define MBEDTLS_IGNORE_RETURN(result) ((void) !(result)) 146 #endif 147 148 /** 149 * \brief Securely zeroize a buffer 150 * 151 * The function is meant to wipe the data contained in a buffer so 152 * that it can no longer be recovered even if the program memory 153 * is later compromised. Call this function on sensitive data 154 * stored on the stack before returning from a function, and on 155 * sensitive data stored on the heap before freeing the heap 156 * object. 157 * 158 * It is extremely difficult to guarantee that calls to 159 * mbedtls_platform_zeroize() are not removed by aggressive 160 * compiler optimizations in a portable way. For this reason, Mbed 161 * TLS provides the configuration option 162 * MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure 163 * mbedtls_platform_zeroize() to use a suitable implementation for 164 * their platform and needs 165 * 166 * \param buf Buffer to be zeroized 167 * \param len Length of the buffer in bytes 168 * 169 */ 170 void mbedtls_platform_zeroize(void *buf, size_t len); 171 172 #if defined(MBEDTLS_HAVE_TIME_DATE) 173 /** 174 * \brief Platform-specific implementation of gmtime_r() 175 * 176 * The function is a thread-safe abstraction that behaves 177 * similarly to the gmtime_r() function from Unix/POSIX. 178 * 179 * Mbed TLS will try to identify the underlying platform and 180 * make use of an appropriate underlying implementation (e.g. 181 * gmtime_r() for POSIX and gmtime_s() for Windows). If this is 182 * not possible, then gmtime() will be used. In this case, calls 183 * from the library to gmtime() will be guarded by the mutex 184 * mbedtls_threading_gmtime_mutex if MBEDTLS_THREADING_C is 185 * enabled. It is recommended that calls from outside the library 186 * are also guarded by this mutex. 187 * 188 * If MBEDTLS_PLATFORM_GMTIME_R_ALT is defined, then Mbed TLS will 189 * unconditionally use the alternative implementation for 190 * mbedtls_platform_gmtime_r() supplied by the user at compile time. 191 * 192 * \param tt Pointer to an object containing time (in seconds) since the 193 * epoch to be converted 194 * \param tm_buf Pointer to an object where the results will be stored 195 * 196 * \return Pointer to an object of type struct tm on success, otherwise 197 * NULL 198 */ 199 struct tm *mbedtls_platform_gmtime_r(const mbedtls_time_t *tt, 200 struct tm *tm_buf); 201 #endif /* MBEDTLS_HAVE_TIME_DATE */ 202 203 #ifdef __cplusplus 204 } 205 #endif 206 207 #endif /* MBEDTLS_PLATFORM_UTIL_H */ 208