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 OR GPL-2.0-or-later
7 */
8
9 /*
10 * Ensure gmtime_r is available even with -std=c99; must be defined before
11 * config.h, which pulls in glibc's features.h. Harmless on other platforms.
12 */
13 #if !defined(_POSIX_C_SOURCE)
14 #define _POSIX_C_SOURCE 200112L
15 #endif
16
17 #include "common.h"
18
19 #include "mbedtls/platform_util.h"
20 #include "mbedtls/platform.h"
21 #include "mbedtls/threading.h"
22
23 #include <stddef.h>
24 #include <string.h>
25
26 #if !defined(MBEDTLS_PLATFORM_ZEROIZE_ALT)
27 /*
28 * This implementation should never be optimized out by the compiler
29 *
30 * This implementation for mbedtls_platform_zeroize() was inspired from Colin
31 * Percival's blog article at:
32 *
33 * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html
34 *
35 * It uses a volatile function pointer to the standard memset(). Because the
36 * pointer is volatile the compiler expects it to change at
37 * any time and will not optimize out the call that could potentially perform
38 * other operations on the input buffer instead of just setting it to 0.
39 * Nevertheless, as pointed out by davidtgoldblatt on Hacker News
40 * (refer to http://www.daemonology.net/blog/2014-09-05-erratum.html for
41 * details), optimizations of the following form are still possible:
42 *
43 * if( memset_func != memset )
44 * memset_func( buf, 0, len );
45 *
46 * Note that it is extremely difficult to guarantee that
47 * mbedtls_platform_zeroize() will not be optimized out by aggressive compilers
48 * in a portable way. For this reason, Mbed TLS also provides the configuration
49 * option MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure
50 * mbedtls_platform_zeroize() to use a suitable implementation for their
51 * platform and needs.
52 */
53 static void *(*const volatile memset_func)(void *, int, size_t) = memset;
54
mbedtls_platform_zeroize(void * buf,size_t len)55 void mbedtls_platform_zeroize(void *buf, size_t len)
56 {
57 MBEDTLS_INTERNAL_VALIDATE(len == 0 || buf != NULL);
58
59 if (len > 0) {
60 memset_func(buf, 0, len);
61 }
62 }
63 #endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */
64
65 #if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)
66 #include <time.h>
67 #if !defined(_WIN32) && (defined(unix) || \
68 defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
69 defined(__MACH__)))
70 #include <unistd.h>
71 #endif /* !_WIN32 && (unix || __unix || __unix__ ||
72 * (__APPLE__ && __MACH__)) */
73
74 #if !((defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L) || \
75 (defined(_POSIX_THREAD_SAFE_FUNCTIONS) && \
76 _POSIX_THREAD_SAFE_FUNCTIONS >= 200112L))
77 /*
78 * This is a convenience shorthand macro to avoid checking the long
79 * preprocessor conditions above. Ideally, we could expose this macro in
80 * platform_util.h and simply use it in platform_util.c, threading.c and
81 * threading.h. However, this macro is not part of the Mbed TLS public API, so
82 * we keep it private by only defining it in this file
83 */
84 #if !(defined(_WIN32) && !defined(EFIX64) && !defined(EFI32))
85 #define PLATFORM_UTIL_USE_GMTIME
86 #endif /* ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) */
87
88 #endif /* !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \
89 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \
90 _POSIX_THREAD_SAFE_FUNCTIONS >= 200112L ) ) */
91
mbedtls_platform_gmtime_r(const mbedtls_time_t * tt,struct tm * tm_buf)92 struct tm *mbedtls_platform_gmtime_r(const mbedtls_time_t *tt,
93 struct tm *tm_buf)
94 {
95 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
96 return (gmtime_s(tm_buf, tt) == 0) ? tm_buf : NULL;
97 #elif !defined(PLATFORM_UTIL_USE_GMTIME)
98 return gmtime_r(tt, tm_buf);
99 #else
100 struct tm *lt;
101
102 #if defined(MBEDTLS_THREADING_C)
103 if (mbedtls_mutex_lock(&mbedtls_threading_gmtime_mutex) != 0) {
104 return NULL;
105 }
106 #endif /* MBEDTLS_THREADING_C */
107
108 lt = gmtime(tt);
109
110 if (lt != NULL) {
111 memcpy(tm_buf, lt, sizeof(struct tm));
112 }
113
114 #if defined(MBEDTLS_THREADING_C)
115 if (mbedtls_mutex_unlock(&mbedtls_threading_gmtime_mutex) != 0) {
116 return NULL;
117 }
118 #endif /* MBEDTLS_THREADING_C */
119
120 return (lt == NULL) ? NULL : tm_buf;
121 #endif /* _WIN32 && !EFIX64 && !EFI32 */
122 }
123 #endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */
124