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psa: mgmt: Add key slot reuse

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When looking for an empty key slot to store
the description of a key, if all key slots
are in use, reuse the first encountered
and unaccessed key slot containing the
description of a permanent key.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
This commit is contained in:
Ronald Cron
2020-10-21 09:04:34 +02:00
parent f291111007
commit a5b894f7e2
3 changed files with 255 additions and 14 deletions
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63
library/psa_crypto_slot_management.c
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@ -173,27 +173,62 @@ void psa_wipe_all_key_slots( void )
psa_status_t psa_get_empty_key_slot( psa_key_id_t *volatile_key_id,
psa_key_slot_t **p_slot )
{
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
size_t slot_idx;
psa_key_slot_t *selected_slot, *unaccessed_permanent_key_slot;
if( ! global_data.key_slots_initialized )
return( PSA_ERROR_BAD_STATE );
for( slot_idx = PSA_KEY_SLOT_COUNT; slot_idx > 0; slot_idx-- )
{
*p_slot = &global_data.key_slots[ slot_idx - 1 ];
if( ! psa_is_key_slot_occupied( *p_slot ) )
{
*volatile_key_id = PSA_KEY_ID_VOLATILE_MIN +
( (psa_key_id_t)slot_idx ) - 1;
psa_increment_key_slot_access_count( *p_slot );
return( PSA_SUCCESS );
}
status = PSA_ERROR_BAD_STATE;
goto error;
}
selected_slot = unaccessed_permanent_key_slot = NULL;
for( slot_idx = 0; slot_idx < PSA_KEY_SLOT_COUNT; slot_idx++ )
{
psa_key_slot_t *slot = &global_data.key_slots[ slot_idx ];
if( ! psa_is_key_slot_occupied( slot ) )
{
selected_slot = slot;
break;
}
if( ( unaccessed_permanent_key_slot == NULL ) &&
( ! PSA_KEY_LIFETIME_IS_VOLATILE( slot->attr.lifetime ) ) &&
( ! psa_is_key_slot_accessed( slot ) ) )
unaccessed_permanent_key_slot = slot;
}
/*
* If there is no unused key slot and there is at least one unaccessed key
* slot containing the description of a permament key, recycle the first
* such key slot we encountered. If we need later on to operate on the
* permanent key we evict now, we will reload its description from storage.
*/
if( ( selected_slot == NULL ) &&
( unaccessed_permanent_key_slot != NULL ) )
{
selected_slot = unaccessed_permanent_key_slot;
selected_slot->access_count = 1;
psa_wipe_key_slot( selected_slot );
}
if( selected_slot != NULL )
{
*volatile_key_id = PSA_KEY_ID_VOLATILE_MIN +
( (psa_key_id_t)( selected_slot - global_data.key_slots ) );
*p_slot = selected_slot;
psa_increment_key_slot_access_count( selected_slot );
return( PSA_SUCCESS );
}
status = PSA_ERROR_INSUFFICIENT_MEMORY;
error:
*p_slot = NULL;
return( PSA_ERROR_INSUFFICIENT_MEMORY );
*volatile_key_id = 0;
return( status );
}
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)