mbedtls/library/entropy_poll.c
Manuel Pégourié-Gonnard 325ce093f9 Give better error messages for semi-portable parts
Previously it was failing with errors about headers not found, which is
suboptimal in terms of clarity. Now give a clean error with pointer to the
documentation.

Do the checks in the .c files rather than check_config.h as it keeps them
closer to the platform-specific implementations.
2016-02-22 10:47:32 +01:00

223 lines
5.5 KiB
C

/*
* Platform-specific and custom entropy polling functions
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_ENTROPY_C)
#include "mbedtls/entropy.h"
#include "mbedtls/entropy_poll.h"
#if defined(MBEDTLS_TIMING_C)
#include <string.h>
#include "mbedtls/timing.h"
#endif
#if defined(MBEDTLS_HAVEGE_C)
#include "mbedtls/havege.h"
#endif
#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
#if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
!defined(__APPLE__) && !defined(_WIN32)
#error "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in config.h"
#endif
#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
#if !defined(_WIN32_WINNT)
#define _WIN32_WINNT 0x0400
#endif
#include <windows.h>
#include <wincrypt.h>
int mbedtls_platform_entropy_poll( void *data, unsigned char *output, size_t len,
size_t *olen )
{
HCRYPTPROV provider;
((void) data);
*olen = 0;
if( CryptAcquireContext( &provider, NULL, NULL,
PROV_RSA_FULL, CRYPT_VERIFYCONTEXT ) == FALSE )
{
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
}
if( CryptGenRandom( provider, (DWORD) len, output ) == FALSE )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
CryptReleaseContext( provider, 0 );
*olen = len;
return( 0 );
}
#else /* _WIN32 && !EFIX64 && !EFI32 */
/*
* Test for Linux getrandom() support.
* Since there is no wrapper in the libc yet, use the generic syscall wrapper
* available in GNU libc and compatible libc's (eg uClibc).
*/
#if defined(__linux__) && defined(__GLIBC__)
#include <unistd.h>
#include <sys/syscall.h>
#if defined(SYS_getrandom)
#define HAVE_GETRANDOM
static int getrandom_wrapper( void *buf, size_t buflen, unsigned int flags )
{
/* MemSan cannot understand that the syscall writes to the buffer */
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
memset( buf, 0, buflen );
#endif
#endif
return( syscall( SYS_getrandom, buf, buflen, flags ) );
}
#include <sys/utsname.h>
/* Check if version is at least 3.17.0 */
static int check_version_3_17_plus( void )
{
int minor;
struct utsname un;
const char *ver;
/* Get version information */
uname(&un);
ver = un.release;
/* Check major version; assume a single digit */
if( ver[0] < '3' || ver[0] > '9' || ver [1] != '.' )
return( -1 );
if( ver[0] - '0' > 3 )
return( 0 );
/* Ok, so now we know major == 3, check minor.
* Assume 1 or 2 digits. */
if( ver[2] < '0' || ver[2] > '9' )
return( -1 );
minor = ver[2] - '0';
if( ver[3] >= '0' && ver[3] <= '9' )
minor = 10 * minor + ver[3] - '0';
else if( ver [3] != '.' )
return( -1 );
if( minor < 17 )
return( -1 );
return( 0 );
}
static int has_getrandom = -1;
#endif /* SYS_getrandom */
#endif /* __linux__ */
#include <stdio.h>
int mbedtls_platform_entropy_poll( void *data,
unsigned char *output, size_t len, size_t *olen )
{
FILE *file;
size_t read_len;
((void) data);
#if defined(HAVE_GETRANDOM)
if( has_getrandom == -1 )
has_getrandom = ( check_version_3_17_plus() == 0 );
if( has_getrandom )
{
int ret;
if( ( ret = getrandom_wrapper( output, len, 0 ) ) < 0 )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
*olen = ret;
return( 0 );
}
#endif /* HAVE_GETRANDOM */
*olen = 0;
file = fopen( "/dev/urandom", "rb" );
if( file == NULL )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
read_len = fread( output, 1, len, file );
if( read_len != len )
{
fclose( file );
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
}
fclose( file );
*olen = len;
return( 0 );
}
#endif /* _WIN32 && !EFIX64 && !EFI32 */
#endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */
#if defined(MBEDTLS_TIMING_C)
int mbedtls_hardclock_poll( void *data,
unsigned char *output, size_t len, size_t *olen )
{
unsigned long timer = mbedtls_timing_hardclock();
((void) data);
*olen = 0;
if( len < sizeof(unsigned long) )
return( 0 );
memcpy( output, &timer, sizeof(unsigned long) );
*olen = sizeof(unsigned long);
return( 0 );
}
#endif /* MBEDTLS_TIMING_C */
#if defined(MBEDTLS_HAVEGE_C)
int mbedtls_havege_poll( void *data,
unsigned char *output, size_t len, size_t *olen )
{
mbedtls_havege_state *hs = (mbedtls_havege_state *) data;
*olen = 0;
if( mbedtls_havege_random( hs, output, len ) != 0 )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
*olen = len;
return( 0 );
}
#endif /* MBEDTLS_HAVEGE_C */
#endif /* MBEDTLS_ENTROPY_C */