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 */
65static void *(*const volatile memset_func)(void *, int, size_t) = memset;
66
67void 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}
75#endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */
76
77#if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)
78#include <time.h>
79#if !defined(_WIN32) && (defined(unix) || \
80 defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
81 defined(__MACH__)))
82#include <unistd.h>
83#endif /* !_WIN32 && (unix || __unix || __unix__ ||
84 * (__APPLE__ && __MACH__)) */
85
86#if !((defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L) || \
87 (defined(_POSIX_THREAD_SAFE_FUNCTIONS) && \
88 _POSIX_THREAD_SAFE_FUNCTIONS >= 200112L))
89/*
90 * This is a convenience shorthand macro to avoid checking the long
91 * preprocessor conditions above. Ideally, we could expose this macro in
92 * platform_util.h and simply use it in platform_util.c, threading.c and
93 * threading.h. However, this macro is not part of the Mbed TLS public API, so
94 * we keep it private by only defining it in this file
95 */
96#if !(defined(_WIN32) && !defined(EFIX64) && !defined(EFI32))
97#define PLATFORM_UTIL_USE_GMTIME
98#endif /* ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) */
99
100#endif /* !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \
101 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \
102 _POSIX_THREAD_SAFE_FUNCTIONS >= 200112L ) ) */
103
104struct tm *mbedtls_platform_gmtime_r(const mbedtls_time_t *tt,
105 struct tm *tm_buf)
106{
107#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
108 return (gmtime_s(tm_buf, tt) == 0) ? tm_buf : NULL;
109#elif !defined(PLATFORM_UTIL_USE_GMTIME)
110 return gmtime_r(tt, tm_buf);
111#else
112 struct tm *lt;
113
114#if defined(MBEDTLS_THREADING_C)
115 if (mbedtls_mutex_lock(&mbedtls_threading_gmtime_mutex) != 0) {
116 return NULL;
117 }
118#endif /* MBEDTLS_THREADING_C */
119
120 lt = gmtime(tt);
121
122 if (lt != NULL) {
123 memcpy(tm_buf, lt, sizeof(struct tm));
124 }
125
126#if defined(MBEDTLS_THREADING_C)
127 if (mbedtls_mutex_unlock(&mbedtls_threading_gmtime_mutex) != 0) {
128 return NULL;
129 }
130#endif /* MBEDTLS_THREADING_C */
131
132 return (lt == NULL) ? NULL : tm_buf;
133#endif /* _WIN32 && !EFIX64 && !EFI32 */
134}
135#endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */
136