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(MBEDTLS_CONFIG_FILE)
00023 #include "mbedtls/config.h"
00024 #else
00025 #include MBEDTLS_CONFIG_FILE
00026 #endif
00027 
00028 #if defined(MBEDTLS_ENTROPY_C)
00029 
00030 #include "mbedtls/entropy.h"
00031 #include "mbedtls/entropy_poll.h"
00032 
00033 #if defined(MBEDTLS_TIMING_C)
00034 #include <string.h>
00035 #include "mbedtls/timing.h"
00036 #endif
00037 #if defined(MBEDTLS_HAVEGE_C)
00038 #include "mbedtls/havege.h"
00039 #endif
00040 #if defined(MBEDTLS_ENTROPY_NV_SEED)
00041 #include "mbedtls/platform.h"
00042 #endif
00043 
00044 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
00045 
00046 #if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
00047     !defined(__APPLE__) && !defined(_WIN32)
00048 #error "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in config.h"
00049 #endif
00050 
00051 #if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
00052 
00053 #if !defined(_WIN32_WINNT)
00054 #define _WIN32_WINNT 0x0400
00055 #endif
00056 #include <windows.h>
00057 #include <wincrypt.h>
00058 
00059 int mbedtls_platform_entropy_poll( void *data, unsigned char *output, size_t len,
00060                            size_t *olen )
00061 {
00062     HCRYPTPROV provider;
00063     ((void) data);
00064     *olen = 0;
00065 
00066     if( CryptAcquireContext( &provider, NULL, NULL,
00067                               PROV_RSA_FULL, CRYPT_VERIFYCONTEXT ) == FALSE )
00068     {
00069         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00070     }
00071 
00072     if( CryptGenRandom( provider, (DWORD) len, output ) == FALSE )
00073     {
00074         CryptReleaseContext( provider, 0 );
00075         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00076     }
00077 
00078     CryptReleaseContext( provider, 0 );
00079     *olen = len;
00080 
00081     return( 0 );
00082 }
00083 #else /* _WIN32 && !EFIX64 && !EFI32 */
00084 
00085 /*
00086  * Test for Linux getrandom() support.
00087  * Since there is no wrapper in the libc yet, use the generic syscall wrapper
00088  * available in GNU libc and compatible libc's (eg uClibc).
00089  */
00090 #if defined(__linux__) && defined(__GLIBC__)
00091 #include <unistd.h>
00092 #include <sys/syscall.h>
00093 #if defined(SYS_getrandom)
00094 #define HAVE_GETRANDOM
00095 
00096 static int getrandom_wrapper( void *buf, size_t buflen, unsigned int flags )
00097 {
00098     /* MemSan cannot understand that the syscall writes to the buffer */
00099 #if defined(__has_feature)
00100 #if __has_feature(memory_sanitizer)
00101     memset( buf, 0, buflen );
00102 #endif
00103 #endif
00104 
00105     return( syscall( SYS_getrandom, buf, buflen, flags ) );
00106 }
00107 
00108 #include <sys/utsname.h>
00109 /* Check if version is at least 3.17.0 */
00110 static int check_version_3_17_plus( void )
00111 {
00112     int minor;
00113     struct utsname un;
00114     const char *ver;
00115 
00116     /* Get version information */
00117     uname(&un);
00118     ver = un.release;
00119 
00120     /* Check major version; assume a single digit */
00121     if( ver[0] < '3' || ver[0] > '9' || ver [1] != '.' )
00122         return( -1 );
00123 
00124     if( ver[0] - '0' > 3 )
00125         return( 0 );
00126 
00127     /* Ok, so now we know major == 3, check minor.
00128      * Assume 1 or 2 digits. */
00129     if( ver[2] < '0' || ver[2] > '9' )
00130         return( -1 );
00131 
00132     minor = ver[2] - '0';
00133 
00134     if( ver[3] >= '0' && ver[3] <= '9' )
00135         minor = 10 * minor + ver[3] - '0';
00136     else if( ver [3] != '.' )
00137         return( -1 );
00138 
00139     if( minor < 17 )
00140         return( -1 );
00141 
00142     return( 0 );
00143 }
00144 static int has_getrandom = -1;
00145 #endif /* SYS_getrandom */
00146 #endif /* __linux__ */
00147 
00148 #include <stdio.h>
00149 
00150 int mbedtls_platform_entropy_poll( void *data,
00151                            unsigned char *output, size_t len, size_t *olen )
00152 {
00153     FILE *file;
00154     size_t read_len;
00155     ((void) data);
00156 
00157 #if defined(HAVE_GETRANDOM)
00158     if( has_getrandom == -1 )
00159         has_getrandom = ( check_version_3_17_plus() == 0 );
00160 
00161     if( has_getrandom )
00162     {
00163         int ret;
00164 
00165         if( ( ret = getrandom_wrapper( output, len, 0 ) ) < 0 )
00166             return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00167 
00168         *olen = ret;
00169         return( 0 );
00170     }
00171 #endif /* HAVE_GETRANDOM */
00172 
00173     *olen = 0;
00174 
00175     file = fopen( "/dev/urandom", "rb" );
00176     if( file == NULL )
00177         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00178 
00179     read_len = fread( output, 1, len, file );
00180     if( read_len != len )
00181     {
00182         fclose( file );
00183         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00184     }
00185 
00186     fclose( file );
00187     *olen = len;
00188 
00189     return( 0 );
00190 }
00191 #endif /* _WIN32 && !EFIX64 && !EFI32 */
00192 #endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */
00193 
00194 #if defined(MBEDTLS_TEST_NULL_ENTROPY)
00195 int mbedtls_null_entropy_poll( void *data,
00196                     unsigned char *output, size_t len, size_t *olen )
00197 {
00198     ((void) data);
00199     ((void) output);
00200     *olen = 0;
00201 
00202     if( len < sizeof(unsigned char) )
00203         return( 0 );
00204 
00205     *olen = sizeof(unsigned char);
00206 
00207     return( 0 );
00208 }
00209 #endif
00210 
00211 #if defined(MBEDTLS_TIMING_C)
00212 int mbedtls_hardclock_poll( void *data,
00213                     unsigned char *output, size_t len, size_t *olen )
00214 {
00215     unsigned long timer = mbedtls_timing_hardclock();
00216     ((void) data);
00217     *olen = 0;
00218 
00219     if( len < sizeof(unsigned long) )
00220         return( 0 );
00221 
00222     memcpy( output, &timer, sizeof(unsigned long) );
00223     *olen = sizeof(unsigned long);
00224 
00225     return( 0 );
00226 }
00227 #endif /* MBEDTLS_TIMING_C */
00228 
00229 #if defined(MBEDTLS_HAVEGE_C)
00230 int mbedtls_havege_poll( void *data,
00231                  unsigned char *output, size_t len, size_t *olen )
00232 {
00233     mbedtls_havege_state *hs = (mbedtls_havege_state *) data;
00234     *olen = 0;
00235 
00236     if( mbedtls_havege_random( hs, output, len ) != 0 )
00237         return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00238 
00239     *olen = len;
00240 
00241     return( 0 );
00242 }
00243 #endif /* MBEDTLS_HAVEGE_C */
00244 
00245 #if defined(MBEDTLS_ENTROPY_NV_SEED)
00246 int mbedtls_nv_seed_poll( void *data,
00247                           unsigned char *output, size_t len, size_t *olen )
00248 {
00249     unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
00250     size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
00251     ((void) data);
00252 
00253     memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
00254 
00255     if( mbedtls_nv_seed_read( buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) < 0 )
00256       return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
00257 
00258     if( len < use_len )
00259       use_len = len;
00260 
00261     memcpy( output, buf, use_len );
00262     *olen = use_len;
00263 
00264     return( 0 );
00265 }
00266 #endif /* MBEDTLS_ENTROPY_NV_SEED */
00267 
00268 #endif /* MBEDTLS_ENTROPY_C */