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
mbedtls_platform_zeroize(void * buf,size_t len)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
mbedtls_platform_gmtime_r(const mbedtls_time_t * tt,struct tm * tm_buf)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
