mbedtls/library/entropy_poll.c
2020-06-24 17:16:33 +01:00

283 lines
7.2 KiB
C

/*
* Platform-specific and custom entropy polling functions
*
* Copyright (C) 2006-2016, 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(__linux__)
/* Ensure that syscall() is available even when compiling with -std=c99 */
#define _GNU_SOURCE
#endif
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#include <string.h>
#if defined(MBEDTLS_ENTROPY_C)
#include "mbedtls/entropy.h"
#include "mbedtls/entropy_poll.h"
#include "mbedtls/error.h"
#if defined(MBEDTLS_TIMING_C)
#include "mbedtls/timing.h"
#endif
#if defined(MBEDTLS_HAVEGE_C)
#include "mbedtls/havege.h"
#endif
#if defined(MBEDTLS_ENTROPY_NV_SEED)
#include "mbedtls/platform.h"
#endif
#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
#if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
!defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \
!defined(__HAIKU__) && !defined(__midipix__)
#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 )
{
CryptReleaseContext( provider, 0 );
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__)) || defined(__midipix__))
#include <unistd.h>
#include <sys/syscall.h>
#if defined(SYS_getrandom)
#define HAVE_GETRANDOM
#include <errno.h>
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 ) );
}
#endif /* SYS_getrandom */
#endif /* __linux__ || __midipix__ */
/*
* Some BSD systems provide KERN_ARND.
* This is equivalent to reading from /dev/urandom, only it doesn't require an
* open file descriptor, and provides up to 256 bytes per call (basically the
* same as getentropy(), but with a longer history).
*
* Documentation: https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+7
*/
#if (defined(__FreeBSD__) || defined(__NetBSD__)) && !defined(HAVE_GETRANDOM)
#include <sys/param.h>
#include <sys/sysctl.h>
#if defined(KERN_ARND)
#define HAVE_SYSCTL_ARND
static int sysctl_arnd_wrapper( unsigned char *buf, size_t buflen )
{
int name[2];
size_t len;
name[0] = CTL_KERN;
name[1] = KERN_ARND;
while( buflen > 0 )
{
len = buflen > 256 ? 256 : buflen;
if( sysctl(name, 2, buf, &len, NULL, 0) == -1 )
return( -1 );
buflen -= len;
buf += len;
}
return( 0 );
}
#endif /* KERN_ARND */
#endif /* __FreeBSD__ || __NetBSD__ */
#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;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
((void) data);
#if defined(HAVE_GETRANDOM)
ret = getrandom_wrapper( output, len, 0 );
if( ret >= 0 )
{
*olen = ret;
return( 0 );
}
else if( errno != ENOSYS )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
/* Fall through if the system call isn't known. */
#else
((void) ret);
#endif /* HAVE_GETRANDOM */
#if defined(HAVE_SYSCTL_ARND)
((void) file);
((void) read_len);
if( sysctl_arnd_wrapper( output, len ) == -1 )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
*olen = len;
return( 0 );
#else
*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 /* HAVE_SYSCTL_ARND */
}
#endif /* _WIN32 && !EFIX64 && !EFI32 */
#endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */
#if defined(MBEDTLS_TEST_NULL_ENTROPY)
int mbedtls_null_entropy_poll( void *data,
unsigned char *output, size_t len, size_t *olen )
{
((void) data);
((void) output);
*olen = 0;
if( len < sizeof(unsigned char) )
return( 0 );
*olen = sizeof(unsigned char);
return( 0 );
}
#endif
#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 */
#if defined(MBEDTLS_ENTROPY_NV_SEED)
int mbedtls_nv_seed_poll( void *data,
unsigned char *output, size_t len, size_t *olen )
{
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
((void) data);
memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
if( mbedtls_nv_seed_read( buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) < 0 )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
if( len < use_len )
use_len = len;
memcpy( output, buf, use_len );
*olen = use_len;
return( 0 );
}
#endif /* MBEDTLS_ENTROPY_NV_SEED */
#endif /* MBEDTLS_ENTROPY_C */