Commit b34e42e6 authored by Andres AG's avatar Andres AG Committed by Simon Butcher

Add a new self test to entropy module

The self test is a quick way to check at startup whether the entropy
sources are functioning correctly. The self test only polls 8 bytes
from the default entropy source and performs the following checks:

- The bytes are not all 0x00 or 0xFF.
- The hardware does not return an error when polled.
- The entropy does not provide data in a patter. Only check pattern
  at byte, word and long word sizes.
parent 0e7d3873
......@@ -258,6 +258,15 @@ int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *
* \return 0 if successful, or 1 if a test failed
*/
int mbedtls_entropy_self_test( int verbose );
#if !defined(MBEDTLS_TEST_NULL_ENTROPY) && defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
/**
* \brief Checkup routine
*
* \return 0 if successful, or 1 if a test failed
*/
int mbedtls_entropy_self_test_bias( int verbose );
#endif /* !MBEDTLS_TEST_NULL_ENTROPY && MBEDTLS_ENTROPY_HARDWARE_ALT */
#endif /* MBEDTLS_SELF_TEST */
#ifdef __cplusplus
......
......@@ -470,6 +470,94 @@ static int entropy_dummy_source( void *data, unsigned char *output,
return( 0 );
}
#if !defined(MBEDTLS_TEST_NULL_ENTROPY) && defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
#define MBEDTLS_SELF_TEST_BIAS_PATTERN( buf_len, type ) \
{ \
size_t i; \
int has_pat = 1; \
for( i = 0; i < buf_len; i += sizeof( type ) ) \
{ \
has_pat &= memcmp( buf, buf + i, sizeof( type ) ) == 0; \
} \
if( ( ret = has_pat ) != 0 ) \
goto cleanup; \
} while( 0 ) \
/*
* A quick test to ensure hat the entropy sources are functioning correctly
* and there is no obvious bias. 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 is
* only perform for bytes, words and long words.
* - The error code returned by the entropy source is not an error.
*/
int mbedtls_entropy_self_test_bias( int verbose )
{
int ret = 0;
unsigned char buf[2 * sizeof( unsigned long long int )];
mbedtls_entropy_context ctx;
size_t entropy_len;
size_t olen;
size_t gather_tries;
if( verbose != 0 )
mbedtls_printf( " ENTROPY_BIAS test: " );
memset( buf, 0x00, sizeof( buf ) );
mbedtls_entropy_init( &ctx );
/* The hardware entropy source could return less than the amount of
* bytes we requested, so we poll the source as many times as there are
* bytes */
gather_tries = sizeof( buf );
entropy_len = 0;
while( gather_tries > 0 && entropy_len < sizeof( buf ) )
{
if( ( ret = mbedtls_hardware_poll( &ctx, buf + entropy_len,
sizeof( buf ) - entropy_len, &olen ) ) != 0 )
goto cleanup;
entropy_len += olen;
gather_tries--;
}
if( entropy_len < sizeof( buf ) )
{
/* We still do not have enough entropy: fail */
ret = 1;
goto cleanup;
}
/* Make sure that the entropy source is not returning values in a
* pattern */
/* Byte */
MBEDTLS_SELF_TEST_BIAS_PATTERN( 2 * sizeof( unsigned long long int ), unsigned char );
/* Word */
MBEDTLS_SELF_TEST_BIAS_PATTERN( 2 * sizeof( unsigned long long int ), unsigned long );
/* Long word */
MBEDTLS_SELF_TEST_BIAS_PATTERN( 2 * sizeof( unsigned long long int ), unsigned long long int );
cleanup:
mbedtls_entropy_free( &ctx );
if( verbose != 0 )
{
if( ret != 0 )
mbedtls_printf( "failed\n" );
else
mbedtls_printf( "passed\n" );
mbedtls_printf( "\n" );
}
return( ret != 0 );
}
#endif /* !MBEDTLS_TEST_NULL_ENTROPY && 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
......
......@@ -375,6 +375,12 @@ int main( int argc, char *argv[] )
{
suites_failed++;
}
#if !defined(MBEDTLS_TEST_NULL_ENTROPY) && defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
if( mbedtls_entropy_self_test_bias( v ) != 0)
{
suites_failed++;
}
#endif
suites_tested++;
#endif
......
......@@ -381,5 +381,8 @@ void entropy_nv_seed( char *read_seed_str )
void entropy_selftest( )
{
TEST_ASSERT( mbedtls_entropy_self_test( 0 ) == 0 );
#if !defined(MBEDTLS_TEST_NULL_ENTROPY) && defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
TEST_ASSERT( mbedtls_entropy_self_test_bias( 0 ) == 0 );
#endif
}
/* END_CASE */
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment