1 /*
2 * Common and shared functions used by multiple modules in the Mbed TLS
3 * library.
4 *
5 * Copyright (C) 2018, Arm Limited, All Rights Reserved
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 * This file is part of Mbed TLS (https://tls.mbed.org)
21 */
22
23 /*
24 * Ensure gmtime_r is available even with -std=c99; must be defined before
25 * config.h, which pulls in glibc's features.h. Harmless on other platforms.
26 */
27 #if !defined(_POSIX_C_SOURCE)
28 #define _POSIX_C_SOURCE 200112L
29 #endif
30
31 #if !defined(MBEDTLS_CONFIG_FILE)
32 #include "mbedtls/config.h"
33 #else
34 #include MBEDTLS_CONFIG_FILE
35 #endif
36
37 #include "mbedtls/platform_util.h"
38 #include "mbedtls/platform.h"
39 #include "mbedtls/threading.h"
40
41 #include <stddef.h>
42 #include <string.h>
43
44 #if !defined(MBEDTLS_PLATFORM_ZEROIZE_ALT)
45 /*
46 * This implementation should never be optimized out by the compiler
47 *
48 * This implementation for mbedtls_platform_zeroize() was inspired from Colin
49 * Percival's blog article at:
50 *
51 * http://www.daemonology.net/blog/2014-09-04-how-to-zero-a-buffer.html
52 *
53 * It uses a volatile function pointer to the standard memset(). Because the
54 * pointer is volatile the compiler expects it to change at
55 * any time and will not optimize out the call that could potentially perform
56 * other operations on the input buffer instead of just setting it to 0.
57 * Nevertheless, as pointed out by davidtgoldblatt on Hacker News
58 * (refer to http://www.daemonology.net/blog/2014-09-05-erratum.html for
59 * details), optimizations of the following form are still possible:
60 *
61 * if( memset_func != memset )
62 * memset_func( buf, 0, len );
63 *
64 * Note that it is extremely difficult to guarantee that
65 * mbedtls_platform_zeroize() will not be optimized out by aggressive compilers
66 * in a portable way. For this reason, Mbed TLS also provides the configuration
67 * option MBEDTLS_PLATFORM_ZEROIZE_ALT, which allows users to configure
68 * mbedtls_platform_zeroize() to use a suitable implementation for their
69 * platform and needs.
70 */
71 static void * (* const volatile memset_func)( void *, int, size_t ) = (void * (* const volatile)( void *, int, size_t))memset;
72
mbedtls_platform_zeroize(void * buf,size_t len)73 void mbedtls_platform_zeroize( void *buf, size_t len )
74 {
75 memset_func( buf, 0, len );
76 }
77 #endif /* MBEDTLS_PLATFORM_ZEROIZE_ALT */
78
79 #if defined(MBEDTLS_HAVE_TIME_DATE) && !defined(MBEDTLS_PLATFORM_GMTIME_R_ALT)
80 #include <time.h>
81 #if !defined(_WIN32) && (defined(unix) || \
82 defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
83 defined(__MACH__)))
84 #include <unistd.h>
85 #endif /* !_WIN32 && (unix || __unix || __unix__ ||
86 * (__APPLE__ && __MACH__)) */
87
88 #if !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \
89 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \
90 _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) )
91 /*
92 * This is a convenience shorthand macro to avoid checking the long
93 * preprocessor conditions above. Ideally, we could expose this macro in
94 * platform_util.h and simply use it in platform_util.c, threading.c and
95 * threading.h. However, this macro is not part of the Mbed TLS public API, so
96 * we keep it private by only defining it in this file
97 */
98 #if ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) )
99 #define PLATFORM_UTIL_USE_GMTIME
100 #endif /* ! ( defined(_WIN32) && !defined(EFIX64) && !defined(EFI32) ) */
101
102 #endif /* !( ( defined(_POSIX_VERSION) && _POSIX_VERSION >= 200809L ) || \
103 ( defined(_POSIX_THREAD_SAFE_FUNCTIONS ) && \
104 _POSIX_THREAD_SAFE_FUNCTIONS >= 20112L ) ) */
105
mbedtls_platform_gmtime_r(const mbedtls_time_t * tt,struct tm * tm_buf)106 struct tm *mbedtls_platform_gmtime_r( const mbedtls_time_t *tt,
107 struct tm *tm_buf )
108 {
109 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
110 return( ( gmtime_s( tm_buf, tt ) == 0 ) ? tm_buf : NULL );
111 #elif !defined(PLATFORM_UTIL_USE_GMTIME)
112 return( gmtime_r( tt, tm_buf ) );
113 #else
114 struct tm *lt;
115
116 #if defined(MBEDTLS_THREADING_C)
117 if( mbedtls_mutex_lock( &mbedtls_threading_gmtime_mutex ) != 0 )
118 return( NULL );
119 #endif /* MBEDTLS_THREADING_C */
120
121 lt = gmtime( tt );
122
123 if( lt != NULL )
124 {
125 memcpy( tm_buf, lt, sizeof( struct tm ) );
126 }
127
128 #if defined(MBEDTLS_THREADING_C)
129 if( mbedtls_mutex_unlock( &mbedtls_threading_gmtime_mutex ) != 0 )
130 return( NULL );
131 #endif /* MBEDTLS_THREADING_C */
132
133 return( ( lt == NULL ) ? NULL : tm_buf );
134 #endif /* _WIN32 && !EFIX64 && !EFI32 */
135 }
136 #endif /* MBEDTLS_HAVE_TIME_DATE && MBEDTLS_PLATFORM_GMTIME_R_ALT */
137