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Remove special handling for zero-length keys

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Zero-length keys are rejected at creation time, so we don't need any
special handling internally.

When exporting a key, we do need to take care of the case where the
output buffer is empty, but this is easy: an empty output buffer is
never valid.
This commit is contained in:
Gilles Peskine 2019-09-12 19:20:29 +02:00
parent 043b281714
commit f916894ef3
1 changed files with 14 additions and 23 deletions
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25
library/psa_crypto.c
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@ -451,13 +451,6 @@ static psa_status_t prepare_raw_data_slot( psa_key_type_t type,
switch( type ) switch( type )
{ {
case PSA_KEY_TYPE_RAW_DATA: case PSA_KEY_TYPE_RAW_DATA:
if( bits == 0 )
{
raw->bytes = 0;
raw->data = NULL;
return( PSA_SUCCESS );
}
break;
#if defined(MBEDTLS_MD_C) #if defined(MBEDTLS_MD_C)
case PSA_KEY_TYPE_HMAC: case PSA_KEY_TYPE_HMAC:
#endif #endif
@ -1281,6 +1274,12 @@ static psa_status_t psa_internal_export_key( const psa_key_slot_t *slot,
if( export_public_key && ! PSA_KEY_TYPE_IS_ASYMMETRIC( slot->attr.type ) ) if( export_public_key && ! PSA_KEY_TYPE_IS_ASYMMETRIC( slot->attr.type ) )
return( PSA_ERROR_INVALID_ARGUMENT ); return( PSA_ERROR_INVALID_ARGUMENT );
/* Reject a zero-length output buffer now, since this can never be a
* valid key representation. This way we know that data must be a valid
* pointer and we can do things like memset(data, ..., data_size). */
if( data_size == 0 )
return( PSA_ERROR_BUFFER_TOO_SMALL );
#if defined(MBEDTLS_PSA_CRYPTO_SE_C) #if defined(MBEDTLS_PSA_CRYPTO_SE_C)
if( psa_get_se_driver( slot->attr.lifetime, &drv, &drv_context ) ) if( psa_get_se_driver( slot->attr.lifetime, &drv, &drv_context ) )
{ {
@ -1302,12 +1301,9 @@ static psa_status_t psa_internal_export_key( const psa_key_slot_t *slot,
{ {
if( slot->data.raw.bytes > data_size ) if( slot->data.raw.bytes > data_size )
return( PSA_ERROR_BUFFER_TOO_SMALL ); return( PSA_ERROR_BUFFER_TOO_SMALL );
if( data_size != 0 )
{
memcpy( data, slot->data.raw.data, slot->data.raw.bytes ); memcpy( data, slot->data.raw.data, slot->data.raw.bytes );
memset( data + slot->data.raw.bytes, 0, memset( data + slot->data.raw.bytes, 0,
data_size - slot->data.raw.bytes ); data_size - slot->data.raw.bytes );
}
*data_length = slot->data.raw.bytes; *data_length = slot->data.raw.bytes;
return( PSA_SUCCESS ); return( PSA_SUCCESS );
} }
@ -1366,9 +1362,6 @@ static psa_status_t psa_internal_export_key( const psa_key_slot_t *slot,
} }
if( ret < 0 ) if( ret < 0 )
{ {
/* If data_size is 0 then data may be NULL and then the
* call to memset would have undefined behavior. */
if( data_size != 0 )
memset( data, 0, data_size ); memset( data, 0, data_size );
return( mbedtls_to_psa_error( ret ) ); return( mbedtls_to_psa_error( ret ) );
} }
@ -1676,7 +1669,7 @@ static psa_status_t psa_finish_key_creation(
slot->attr.bits ); slot->attr.bits );
uint8_t *buffer = mbedtls_calloc( 1, buffer_size ); uint8_t *buffer = mbedtls_calloc( 1, buffer_size );
size_t length = 0; size_t length = 0;
if( buffer == NULL && buffer_size != 0 ) if( buffer == NULL )
return( PSA_ERROR_INSUFFICIENT_MEMORY ); return( PSA_ERROR_INSUFFICIENT_MEMORY );
status = psa_internal_export_key( slot, status = psa_internal_export_key( slot,
buffer, buffer_size, &length, buffer, buffer_size, &length,
@ -1685,7 +1678,6 @@ static psa_status_t psa_finish_key_creation(
status = psa_save_persistent_key( &slot->attr, status = psa_save_persistent_key( &slot->attr,
buffer, length ); buffer, length );
if( buffer_size != 0 )
mbedtls_platform_zeroize( buffer, buffer_size ); mbedtls_platform_zeroize( buffer, buffer_size );
mbedtls_free( buffer ); mbedtls_free( buffer );
} }
@ -1963,7 +1955,7 @@ static psa_status_t psa_copy_key_material( const psa_key_slot_t *source,
buffer_size = PSA_KEY_EXPORT_MAX_SIZE( source->attr.type, buffer_size = PSA_KEY_EXPORT_MAX_SIZE( source->attr.type,
psa_get_key_slot_bits( source ) ); psa_get_key_slot_bits( source ) );
buffer = mbedtls_calloc( 1, buffer_size ); buffer = mbedtls_calloc( 1, buffer_size );
if( buffer == NULL && buffer_size != 0 ) if( buffer == NULL )
return( PSA_ERROR_INSUFFICIENT_MEMORY ); return( PSA_ERROR_INSUFFICIENT_MEMORY );
status = psa_internal_export_key( source, buffer, buffer_size, &length, 0 ); status = psa_internal_export_key( source, buffer, buffer_size, &length, 0 );
if( status != PSA_SUCCESS ) if( status != PSA_SUCCESS )
@ -1972,7 +1964,6 @@ static psa_status_t psa_copy_key_material( const psa_key_slot_t *source,
status = psa_import_key_into_slot( target, buffer, length ); status = psa_import_key_into_slot( target, buffer, length );
exit: exit:
if( buffer_size != 0 )
mbedtls_platform_zeroize( buffer, buffer_size ); mbedtls_platform_zeroize( buffer, buffer_size );
mbedtls_free( buffer ); mbedtls_free( buffer );
return( status ); return( status );