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mbedtls/library/entropy.c
Andres Amaya Garcia a7559cb7ba Fix entropy module to work with hw accelerator 
This patch modifies the entropy.c module to ensure that the sha256 and
sha512 contexts are correctly initialised and freed instead of skipping
these calls or simply zeroizing with memset() or mbedtls_zeroize().
This is important as the sha contexts might otherwise leak memory or
other resources, and even more so in the context of hardware
accelerators where the configuration of the device might be done in the
init and free calls.
2017-06-29 16:27:15 +01:00

685 lines
19 KiB
C
Raw Blame History

/*
* 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 )
{
ctx->source_count = 0;
memset( ctx->source, 0, sizeof( ctx->source ) );
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
mbedtls_sha512_init( &ctx->accumulator );
mbedtls_sha512_starts_ext( &ctx->accumulator, 0 );
#else
mbedtls_sha256_init( &ctx->accumulator );
mbedtls_sha256_starts_ext( &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 );
ctx->initial_entropy_run = 0;
#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
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
mbedtls_sha512_free( &ctx->accumulator );
#else
mbedtls_sha256_free( &ctx->accumulator );
#endif
#if defined(MBEDTLS_ENTROPY_NV_SEED)
ctx->initial_entropy_run = 0;
#endif
ctx->source_count = 0;
mbedtls_zeroize( ctx->source, sizeof( ctx->source ) );
}
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;
int ret;
if( use_len > MBEDTLS_ENTROPY_BLOCK_SIZE )
{
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
if( ( ret = mbedtls_sha512_ext( data, len, tmp, 0 ) ) != 0 )
return( ret );
#else
if( ( ret = mbedtls_sha256_ext( data, len, tmp, 0 ) ) != 0 )
return( ret );
#endif
p = tmp;
use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
}
header[0] = source_id;
header[1] = use_len & 0xFF;
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
if( ( ret = mbedtls_sha512_update_ext( &ctx->accumulator, header, 2 ) ) != 0 )
return( ret );
return( mbedtls_sha512_update_ext( &ctx->accumulator, p, use_len ) );
#else
if( ( ret = mbedtls_sha256_update_ext( &ctx->accumulator, header, 2 ) ) != 0 )
return( ret );
return( mbedtls_sha256_update_ext( &ctx->accumulator, p, use_len ) );
#endif
}
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)
if( ( ret = mbedtls_sha512_finish_ext( &ctx->accumulator, buf ) ) != 0 )
goto exit;
/*
* Reset accumulator and counters and recycle existing entropy
*/
mbedtls_sha512_free( &ctx->accumulator );
mbedtls_sha512_init( &ctx->accumulator );
if( ( ret = mbedtls_sha512_starts_ext( &ctx->accumulator, 0 ) ) != 0 )
goto exit;
if( ( ret = mbedtls_sha512_update_ext( &ctx->accumulator, buf,
MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
goto exit;
/*
* Perform second SHA-512 on entropy
*/
if( ( ret = mbedtls_sha512_ext( buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
buf, 0 ) ) != 0 )
goto exit;
#else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
if( ( ret = mbedtls_sha256_finish_ext( &ctx->accumulator, buf ) ) != 0 )
goto exit;
/*
* Reset accumulator and counters and recycle existing entropy
*/
mbedtls_sha256_free( &ctx->accumulator );
mbedtls_sha256_init( &ctx->accumulator );
if( ( ret = mbedtls_sha256_starts_ext( &ctx->accumulator, 0 ) ) != 0 )
goto exit;
if( ( ret = mbedtls_sha256_update_ext( &ctx->accumulator, buf,
MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
goto exit;
/*
* Perform second SHA-256 on entropy
*/
if( ( ret = mbedtls_sha256_ext( buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
buf, 0 ) ) != 0 )
goto exit;
#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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