entropy_poll.c

00001 /*
00002  *  Platform-specific and custom entropy polling functions
00003  *
00004  *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
00005  *  SPDX-License-Identifier: Apache-2.0
00006  *
00007  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
00008  *  not use this file except in compliance with the License.
00009  *  You may obtain a copy of the License at
00010  *
00011  *  http://www.apache.org/licenses/LICENSE-2.0
00012  *
00013  *  Unless required by applicable law or agreed to in writing, software
00014  *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00015  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00016  *  See the License for the specific language governing permissions and
00017  *  limitations under the License.
00018  *
00019  *  This file is part of mbed TLS (https://tls.mbed.org)
00020  */
00021 
00022 #if defined(__linux__)
00023 /* Ensure that syscall() is available even when compiling with -std=c99 */
00024 #define _GNU_SOURCE
00025 #endif
00026 
00027 #if !defined(MBEDTLS_CONFIG_FILE)
00028 #include "mbedtls/config.h"
00029 #else
00030 #include MBEDTLS_CONFIG_FILE
00031 #endif
00032 
00033 #include <string.h>
00034 
00035 #if defined(MBEDTLS_ENTROPY_C)
00036 
00037 #include "mbedtls/entropy.h"
00038 #include "mbedtls/entropy_poll.h"
00039 
00040 #if defined(MBEDTLS_TIMING_C)
00041 #include "mbedtls/timing.h"
00042 #endif
00043 #if defined(MBEDTLS_HAVEGE_C)
00044 #include "mbedtls/havege.h"
00045 #endif
00046 #if defined(MBEDTLS_ENTROPY_NV_SEED)
00047 #include "mbedtls/platform.h"
00048 #endif
00049 
00050 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
00051 
00052 #if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
00053     !defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \
00054     !defined(__HAIKU__)
00055 #error "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in config.h"
00056 #endif
00057 
00058 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
00059 
00060 #if !defined(_WIN32_WINNT)
00061 #define _WIN32_WINNT 0x0400
00062 #endif
00063 #include <windows.h>
00064 #include <wincrypt.h>
00065 
00066 int mbedtls_platform_entropy_poll( void *data, unsigned char *output, size_t len,
00067                            size_t *olen )
00068 {
00069     HCRYPTPROV provider;
00070     ((void) data);
00071     *olen = 0;
00072 
00073     if( CryptAcquireContext( &provider, NULL, NULL,
00074                               PROV_RSA_FULL, CRYPT_VERIFYCONTEXT ) == FALSE )
00075     {
00076         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00077     }
00078 
00079     if( CryptGenRandom( provider, (DWORD) len, output ) == FALSE )
00080     {
00081         CryptReleaseContext( provider, 0 );
00082         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00083     }
00084 
00085     CryptReleaseContext( provider, 0 );
00086     *olen = len;
00087 
00088     return( 0 );
00089 }
00090 #else /* _WIN32 && !EFIX64 && !EFI32 */
00091 
00092 /*
00093  * Test for Linux getrandom() support.
00094  * Since there is no wrapper in the libc yet, use the generic syscall wrapper
00095  * available in GNU libc and compatible libc's (eg uClibc).
00096  */
00097 #if defined(__linux__) && defined(__GLIBC__)
00098 #include <unistd.h>
00099 #include <sys/syscall.h>
00100 #if defined(SYS_getrandom)
00101 #define HAVE_GETRANDOM
00102 
00103 static int getrandom_wrapper( void *buf, size_t buflen, unsigned int flags )
00104 {
00105     /* MemSan cannot understand that the syscall writes to the buffer */
00106 #if defined(__has_feature)
00107 #if __has_feature(memory_sanitizer)
00108     memset( buf, 0, buflen );
00109 #endif
00110 #endif
00111 
00112     return( syscall( SYS_getrandom, buf, buflen, flags ) );
00113 }
00114 
00115 #include <sys/utsname.h>
00116 /* Check if version is at least 3.17.0 */
00117 static int check_version_3_17_plus( void )
00118 {
00119     int minor;
00120     struct utsname un;
00121     const char *ver;
00122 
00123     /* Get version information */
00124     uname(&un);
00125     ver = un.release;
00126 
00127     /* Check major version; assume a single digit */
00128     if( ver[0] < '3' || ver[0] > '9' || ver [1] != '.' )
00129         return( -1 );
00130 
00131     if( ver[0] - '0' > 3 )
00132         return( 0 );
00133 
00134     /* Ok, so now we know major == 3, check minor.
00135      * Assume 1 or 2 digits. */
00136     if( ver[2] < '0' || ver[2] > '9' )
00137         return( -1 );
00138 
00139     minor = ver[2] - '0';
00140 
00141     if( ver[3] >= '0' && ver[3] <= '9' )
00142         minor = 10 * minor + ver[3] - '0';
00143     else if( ver [3] != '.' )
00144         return( -1 );
00145 
00146     if( minor < 17 )
00147         return( -1 );
00148 
00149     return( 0 );
00150 }
00151 static int has_getrandom = -1;
00152 #endif /* SYS_getrandom */
00153 #endif /* __linux__ */
00154 
00155 #include <stdio.h>
00156 
00157 int mbedtls_platform_entropy_poll( void *data,
00158                            unsigned char *output, size_t len, size_t *olen )
00159 {
00160     FILE *file;
00161     size_t read_len;
00162     ((void) data);
00163 
00164 #if defined(HAVE_GETRANDOM)
00165     if( has_getrandom == -1 )
00166         has_getrandom = ( check_version_3_17_plus() == 0 );
00167 
00168     if( has_getrandom )
00169     {
00170         int ret;
00171 
00172         if( ( ret = getrandom_wrapper( output, len, 0 ) ) < 0 )
00173             return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00174 
00175         *olen = ret;
00176         return( 0 );
00177     }
00178 #endif /* HAVE_GETRANDOM */
00179 
00180     *olen = 0;
00181 
00182     file = fopen( "/dev/urandom", "rb" );
00183     if( file == NULL )
00184         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00185 
00186     read_len = fread( output, 1, len, file );
00187     if( read_len != len )
00188     {
00189         fclose( file );
00190         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00191     }
00192 
00193     fclose( file );
00194     *olen = len;
00195 
00196     return( 0 );
00197 }
00198 #endif /* _WIN32 && !EFIX64 && !EFI32 */
00199 #endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */
00200 
00201 #if defined(MBEDTLS_TEST_NULL_ENTROPY)
00202 int mbedtls_null_entropy_poll( void *data,
00203                     unsigned char *output, size_t len, size_t *olen )
00204 {
00205     ((void) data);
00206     ((void) output);
00207     *olen = 0;
00208 
00209     if( len < sizeof(unsigned char) )
00210         return( 0 );
00211 
00212     *olen = sizeof(unsigned char);
00213 
00214     return( 0 );
00215 }
00216 #endif
00217 
00218 #if defined(MBEDTLS_TIMING_C)
00219 int mbedtls_hardclock_poll( void *data,
00220                     unsigned char *output, size_t len, size_t *olen )
00221 {
00222     unsigned long timer = mbedtls_timing_hardclock();
00223     ((void) data);
00224     *olen = 0;
00225 
00226     if( len < sizeof(unsigned long) )
00227         return( 0 );
00228 
00229     memcpy( output, &timer, sizeof(unsigned long) );
00230     *olen = sizeof(unsigned long);
00231 
00232     return( 0 );
00233 }
00234 #endif /* MBEDTLS_TIMING_C */
00235 
00236 #if defined(MBEDTLS_HAVEGE_C)
00237 int mbedtls_havege_poll( void *data,
00238                  unsigned char *output, size_t len, size_t *olen )
00239 {
00240     mbedtls_havege_state *hs = (mbedtls_havege_state *) data;
00241     *olen = 0;
00242 
00243     if( mbedtls_havege_random( hs, output, len ) != 0 )
00244         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00245 
00246     *olen = len;
00247 
00248     return( 0 );
00249 }
00250 #endif /* MBEDTLS_HAVEGE_C */
00251 
00252 #if defined(MBEDTLS_ENTROPY_NV_SEED)
00253 int mbedtls_nv_seed_poll( void *data,
00254                           unsigned char *output, size_t len, size_t *olen )
00255 {
00256     unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
00257     size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
00258     ((void) data);
00259 
00260     memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
00261 
00262     if( mbedtls_nv_seed_read( buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) < 0 )
00263       return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00264 
00265     if( len < use_len )
00266       use_len = len;
00267 
00268     memcpy( output, buf, use_len );
00269     *olen = use_len;
00270 
00271     return( 0 );
00272 }
00273 #endif /* MBEDTLS_ENTROPY_NV_SEED */
00274 
00275 #endif /* MBEDTLS_ENTROPY_C */