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mbedtls/library/entropy.c

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/*
* Entropy accumulator implementation
*
* 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(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_ENTROPY_C)
#if defined(MBEDTLS_TEST_NULL_ENTROPY)
#warning "**** WARNING! MBEDTLS_TEST_NULL_ENTROPY defined! "
#warning "**** THIS BUILD HAS NO DEFINED ENTROPY SOURCES "
#warning "**** THIS BUILD IS *NOT* SUITABLE FOR PRODUCTION USE "
#endif
#include "mbedtls/entropy.h"
#include "mbedtls/entropy_poll.h"
#include <string.h>
#if defined(MBEDTLS_FS_IO)
#include <stdio.h>
#endif
#if defined(MBEDTLS_ENTROPY_NV_SEED)
#include "mbedtls/platform.h"
#endif
#if defined(MBEDTLS_SELF_TEST)
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#define mbedtls_printf printf
#endif /* MBEDTLS_PLATFORM_C */
#endif /* MBEDTLS_SELF_TEST */
#if defined(MBEDTLS_HAVEGE_C)
#include "mbedtls/havege.h"
#endif
/* Implementation that should never be optimized out by the compiler */
static void mbedtls_zeroize( void *v, size_t n ) {
volatile unsigned char *p = v; while( n-- ) *p++ = 0;
}
#define ENTROPY_MAX_LOOP 256 /**< Maximum amount to loop before error */
void mbedtls_entropy_init( mbedtls_entropy_context *ctx )
{
memset( ctx, 0, sizeof(mbedtls_entropy_context) );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
mbedtls_sha512_starts( &ctx->accumulator, 0 );
#else
mbedtls_sha256_starts( &ctx->accumulator, 0 );
#endif
#if defined(MBEDTLS_HAVEGE_C)
mbedtls_havege_init( &ctx->havege_data );
#endif
#if defined(MBEDTLS_TEST_NULL_ENTROPY)
mbedtls_entropy_add_source( ctx, mbedtls_null_entropy_poll, NULL,
1, MBEDTLS_ENTROPY_SOURCE_STRONG );
#endif
#if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
mbedtls_entropy_add_source( ctx, mbedtls_platform_entropy_poll, NULL,
MBEDTLS_ENTROPY_MIN_PLATFORM,
MBEDTLS_ENTROPY_SOURCE_STRONG );
#endif
#if defined(MBEDTLS_TIMING_C)
mbedtls_entropy_add_source( ctx, mbedtls_hardclock_poll, NULL,
MBEDTLS_ENTROPY_MIN_HARDCLOCK,
MBEDTLS_ENTROPY_SOURCE_WEAK );
#endif
#if defined(MBEDTLS_HAVEGE_C)
mbedtls_entropy_add_source( ctx, mbedtls_havege_poll, &ctx->havege_data,
MBEDTLS_ENTROPY_MIN_HAVEGE,
MBEDTLS_ENTROPY_SOURCE_STRONG );
#endif
#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
mbedtls_entropy_add_source( ctx, mbedtls_hardware_poll, NULL,
MBEDTLS_ENTROPY_MIN_HARDWARE,
MBEDTLS_ENTROPY_SOURCE_STRONG );
#endif
#if defined(MBEDTLS_ENTROPY_NV_SEED)
mbedtls_entropy_add_source( ctx, mbedtls_nv_seed_poll, NULL,
MBEDTLS_ENTROPY_BLOCK_SIZE,
MBEDTLS_ENTROPY_SOURCE_STRONG );
#endif
#endif /* MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES */
}
void mbedtls_entropy_free( mbedtls_entropy_context *ctx )
{
#if defined(MBEDTLS_HAVEGE_C)
mbedtls_havege_free( &ctx->havege_data );
#endif
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_free( &ctx->mutex );
#endif
mbedtls_zeroize( ctx, sizeof( mbedtls_entropy_context ) );
}
int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
mbedtls_entropy_f_source_ptr f_source, void *p_source,
size_t threshold, int strong )
{
int index, ret = 0;
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
index = ctx->source_count;
if( index >= MBEDTLS_ENTROPY_MAX_SOURCES )
{
ret = MBEDTLS_ERR_ENTROPY_MAX_SOURCES;
goto exit;
}
ctx->source[index].f_source = f_source;
ctx->source[index].p_source = p_source;
ctx->source[index].threshold = threshold;
ctx->source[index].strong = strong;
ctx->source_count++;
exit:
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
/*
* Entropy accumulator update
*/
static int entropy_update( mbedtls_entropy_context *ctx, unsigned char source_id,
const unsigned char *data, size_t len )
{
unsigned char header[2];
unsigned char tmp[MBEDTLS_ENTROPY_BLOCK_SIZE];
size_t use_len = len;
const unsigned char *p = data;
if( use_len > MBEDTLS_ENTROPY_BLOCK_SIZE )
{
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
mbedtls_sha512( data, len, tmp, 0 );
#else
mbedtls_sha256( data, len, tmp, 0 );
#endif
p = tmp;
use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
}
header[0] = source_id;
header[1] = use_len & 0xFF;
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
mbedtls_sha512_update( &ctx->accumulator, header, 2 );
mbedtls_sha512_update( &ctx->accumulator, p, use_len );
#else
mbedtls_sha256_update( &ctx->accumulator, header, 2 );
mbedtls_sha256_update( &ctx->accumulator, p, use_len );
#endif
return( 0 );
}
int mbedtls_entropy_update_manual( mbedtls_entropy_context *ctx,
const unsigned char *data, size_t len )
{
int ret;
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
ret = entropy_update( ctx, MBEDTLS_ENTROPY_SOURCE_MANUAL, data, len );
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
/*
* Run through the different sources to add entropy to our accumulator
*/
static int entropy_gather_internal( mbedtls_entropy_context *ctx )
{
int ret, i, have_one_strong = 0;
unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];
size_t olen;
if( ctx->source_count == 0 )
return( MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED );
/*
* Run through our entropy sources
*/
for( i = 0; i < ctx->source_count; i++ )
{
if( ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG )
have_one_strong = 1;
olen = 0;
if( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
buf, MBEDTLS_ENTROPY_MAX_GATHER, &olen ) ) != 0 )
{
return( ret );
}
/*
* Add if we actually gathered something
*/
if( olen > 0 )
{
entropy_update( ctx, (unsigned char) i, buf, olen );
ctx->source[i].size += olen;
}
}
if( have_one_strong == 0 )
return( MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE );
return( 0 );
}
/*
* Thread-safe wrapper for entropy_gather_internal()
*/
int mbedtls_entropy_gather( mbedtls_entropy_context *ctx )
{
int ret;
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
ret = entropy_gather_internal( ctx );
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
{
int ret, count = 0, i, done;
mbedtls_entropy_context *ctx = (mbedtls_entropy_context *) data;
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
if( len > MBEDTLS_ENTROPY_BLOCK_SIZE )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
#if defined(MBEDTLS_ENTROPY_NV_SEED)
/* Update the NV entropy seed before generating any entropy for outside
* use.
*/
if( ctx->initial_entropy_run == 0 )
{
ctx->initial_entropy_run = 1;
if( ( ret = mbedtls_entropy_update_nv_seed( ctx ) ) != 0 )
return( ret );
}
#endif
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
/*
* Always gather extra entropy before a call
*/
do
{
if( count++ > ENTROPY_MAX_LOOP )
{
ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
goto exit;
}
if( ( ret = entropy_gather_internal( ctx ) ) != 0 )
goto exit;
done = 1;
for( i = 0; i < ctx->source_count; i++ )
if( ctx->source[i].size < ctx->source[i].threshold )
done = 0;
}
while( ! done );
memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
mbedtls_sha512_finish( &ctx->accumulator, buf );
/*
* Reset accumulator and counters and recycle existing entropy
*/
memset( &ctx->accumulator, 0, sizeof( mbedtls_sha512_context ) );
mbedtls_sha512_starts( &ctx->accumulator, 0 );
mbedtls_sha512_update( &ctx->accumulator, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
/*
* Perform second SHA-512 on entropy
*/
mbedtls_sha512( buf, MBEDTLS_ENTROPY_BLOCK_SIZE, buf, 0 );
#else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
mbedtls_sha256_finish( &ctx->accumulator, buf );
/*
* Reset accumulator and counters and recycle existing entropy
*/
memset( &ctx->accumulator, 0, sizeof( mbedtls_sha256_context ) );
mbedtls_sha256_starts( &ctx->accumulator, 0 );
mbedtls_sha256_update( &ctx->accumulator, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
/*
* Perform second SHA-256 on entropy
*/
mbedtls_sha256( buf, MBEDTLS_ENTROPY_BLOCK_SIZE, buf, 0 );
#endif /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
for( i = 0; i < ctx->source_count; i++ )
ctx->source[i].size = 0;
memcpy( output, buf, len );
ret = 0;
exit:
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
#if defined(MBEDTLS_ENTROPY_NV_SEED)
int mbedtls_entropy_update_nv_seed( mbedtls_entropy_context *ctx )
{
int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
unsigned char buf[ MBEDTLS_ENTROPY_MAX_SEED_SIZE ];
/* Read new seed and write it to NV */
if( ( ret = mbedtls_entropy_func( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
return( ret );
if( mbedtls_nv_seed_write( buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) < 0 )
return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
/* Manually update the remaining stream with a separator value to diverge */
memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
mbedtls_entropy_update_manual( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
return( 0 );
}
#endif /* MBEDTLS_ENTROPY_NV_SEED */
#if defined(MBEDTLS_FS_IO)
int mbedtls_entropy_write_seed_file( mbedtls_entropy_context *ctx, const char *path )
{
int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
FILE *f;
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
if( ( f = fopen( path, "wb" ) ) == NULL )
return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
if( ( ret = mbedtls_entropy_func( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
goto exit;
if( fwrite( buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f ) != MBEDTLS_ENTROPY_BLOCK_SIZE )
{
ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
goto exit;
}
ret = 0;
exit:
fclose( f );
return( ret );
}
int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *path )
{
FILE *f;
size_t n;
unsigned char buf[ MBEDTLS_ENTROPY_MAX_SEED_SIZE ];
if( ( f = fopen( path, "rb" ) ) == NULL )
return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
fseek( f, 0, SEEK_END );
n = (size_t) ftell( f );
fseek( f, 0, SEEK_SET );
if( n > MBEDTLS_ENTROPY_MAX_SEED_SIZE )
n = MBEDTLS_ENTROPY_MAX_SEED_SIZE;
if( fread( buf, 1, n, f ) != n )
{
fclose( f );
return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
}
fclose( f );
mbedtls_entropy_update_manual( ctx, buf, n );
return( mbedtls_entropy_write_seed_file( ctx, path ) );
}
#endif /* MBEDTLS_FS_IO */
#if defined(MBEDTLS_SELF_TEST)
#if !defined(MBEDTLS_TEST_NULL_ENTROPY)
/*
* Dummy source function
*/
static int entropy_dummy_source( void *data, unsigned char *output,
size_t len, size_t *olen )
{
((void) data);
memset( output, 0x2a, len );
*olen = len;
return( 0 );
}
#endif /* !MBEDTLS_TEST_NULL_ENTROPY */
#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
static int mbedtls_entropy_source_self_test_gather( unsigned char *buf, size_t buf_len )
{
int ret = 0;
size_t entropy_len = 0;
size_t olen = 0;
size_t attempts = buf_len;
while( attempts > 0 && entropy_len < buf_len )
{
if( ( ret = mbedtls_hardware_poll( NULL, buf + entropy_len,
buf_len - entropy_len, &olen ) ) != 0 )
return( ret );
entropy_len += olen;
attempts--;
}
if( entropy_len < buf_len )
{
ret = 1;
}
return( ret );
}
static int mbedtls_entropy_source_self_test_check_bits( const unsigned char *buf,
size_t buf_len )
{
unsigned char set= 0xFF;
unsigned char unset = 0x00;
size_t i;
for( i = 0; i < buf_len; i++ )
{
set &= buf[i];
unset |= buf[i];
}
return( set == 0xFF || unset == 0x00 );
}
/*
* A test to ensure hat the entropy sources are functioning correctly
* and there is no obvious failure. The test performs the following checks:
* - The entropy source is not providing only 0s (all bits unset) or 1s (all
* bits set).
* - The entropy source is not providing values in a pattern. Because the
* hardware could be providing data in an arbitrary length, this check polls
* the hardware entropy source twice and compares the result to ensure they
* are not equal.
* - The error code returned by the entropy source is not an error.
*/
int mbedtls_entropy_source_self_test( int verbose )
{
int ret = 0;
unsigned char buf0[2 * sizeof( unsigned long long int )];
unsigned char buf1[2 * sizeof( unsigned long long int )];
if( verbose != 0 )
mbedtls_printf( " ENTROPY_BIAS test: " );
memset( buf0, 0x00, sizeof( buf0 ) );
memset( buf1, 0x00, sizeof( buf1 ) );
if( ( ret = mbedtls_entropy_source_self_test_gather( buf0, sizeof( buf0 ) ) ) != 0 )
goto cleanup;
if( ( ret = mbedtls_entropy_source_self_test_gather( buf1, sizeof( buf1 ) ) ) != 0 )
goto cleanup;
/* Make sure that the returned values are not all 0 or 1 */
if( ( ret = mbedtls_entropy_source_self_test_check_bits( buf0, sizeof( buf0 ) ) ) != 0 )
goto cleanup;
if( ( ret = mbedtls_entropy_source_self_test_check_bits( buf1, sizeof( buf1 ) ) ) != 0 )
goto cleanup;
/* Make sure that the entropy source is not returning values in a
* pattern */
ret = memcmp( buf0, buf1, sizeof( buf0 ) ) == 0;
cleanup:
if( verbose != 0 )
{
if( ret != 0 )
mbedtls_printf( "failed\n" );
else
mbedtls_printf( "passed\n" );
mbedtls_printf( "\n" );
}
return( ret != 0 );
}
#endif /* MBEDTLS_ENTROPY_HARDWARE_ALT */
/*
* The actual entropy quality is hard to test, but we can at least
* test that the functions don't cause errors and write the correct
* amount of data to buffers.
*/
int mbedtls_entropy_self_test( int verbose )
{
int ret = 1;
#if !defined(MBEDTLS_TEST_NULL_ENTROPY)
mbedtls_entropy_context ctx;
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
unsigned char acc[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
size_t i, j;
#endif /* !MBEDTLS_TEST_NULL_ENTROPY */
if( verbose != 0 )
mbedtls_printf( " ENTROPY test: " );
#if !defined(MBEDTLS_TEST_NULL_ENTROPY)
mbedtls_entropy_init( &ctx );
/* First do a gather to make sure we have default sources */
if( ( ret = mbedtls_entropy_gather( &ctx ) ) != 0 )
goto cleanup;
ret = mbedtls_entropy_add_source( &ctx, entropy_dummy_source, NULL, 16,
MBEDTLS_ENTROPY_SOURCE_WEAK );
if( ret != 0 )
goto cleanup;
if( ( ret = mbedtls_entropy_update_manual( &ctx, buf, sizeof buf ) ) != 0 )
goto cleanup;
/*
* To test that mbedtls_entropy_func writes correct number of bytes:
* - use the whole buffer and rely on ASan to detect overruns
* - collect entropy 8 times and OR the result in an accumulator:
* any byte should then be 0 with probably 2^(-64), so requiring
* each of the 32 or 64 bytes to be non-zero has a false failure rate
* of at most 2^(-58) which is acceptable.
*/
for( i = 0; i < 8; i++ )
{
if( ( ret = mbedtls_entropy_func( &ctx, buf, sizeof( buf ) ) ) != 0 )
goto cleanup;
for( j = 0; j < sizeof( buf ); j++ )
acc[j] |= buf[j];
}
for( j = 0; j < sizeof( buf ); j++ )
{
if( acc[j] == 0 )
{
ret = 1;
goto cleanup;
}
}
#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
if( ( ret = mbedtls_entropy_source_self_test( 0 ) ) != 0 )
goto cleanup;
#endif
cleanup:
mbedtls_entropy_free( &ctx );
#endif /* !MBEDTLS_TEST_NULL_ENTROPY */
if( verbose != 0 )
{
if( ret != 0 )
mbedtls_printf( "failed\n" );
else
mbedtls_printf( "passed\n" );
mbedtls_printf( "\n" );
}
return( ret != 0 );
}
#endif /* MBEDTLS_SELF_TEST */
#endif /* MBEDTLS_ENTROPY_C */
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