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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
View file

@ -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)

20
tests/suites/test_suite_psa_crypto_slot_management.data
View file

@ -186,3 +186,23 @@ invalid_handle:INVALID_HANDLE_HUGE:PSA_ERROR_INVALID_HANDLE:PSA_ERROR_INVALID_HA
Open many transient keys
many_transient_keys:42
# Eviction from a key slot to be able to import a new permanent key.
Key slot eviction to import a new permanent key
key_slot_eviction_to_import_new_key:PSA_KEY_LIFETIME_PERSISTENT
# Eviction from a key slot to be able to import a new volatile key.
Key slot eviction to import a new volatile key
key_slot_eviction_to_import_new_key:PSA_KEY_LIFETIME_VOLATILE
# Check that non reusable key slots are not deleted/overwritten in case of key
# slot starvation:
# . An attempt to access a permanent key while all RAM key slots are occupied
# by volatile keys fails and does not lead to volatile key data to be
# spoiled.
# . With all key slot in use with one containing a permanent key, an attempt
# to copy the permanent key fails (the permanent key slot cannot be reclaimed
# as it is accessed by the copy process) without the permament key data and
# volatile key data being spoiled.
Non reusable key slots integrity in case of key slot starvation
non_reusable_key_slots_integrity_in_case_of_key_slot_starvation

186
tests/suites/test_suite_psa_crypto_slot_management.function
View file

@ -877,3 +877,189 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_PSA_CRYPTO_STORAGE_C */
void key_slot_eviction_to_import_new_key( int lifetime_arg )
{
psa_key_lifetime_t lifetime = (psa_key_lifetime_t)lifetime_arg;
size_t i;
psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
uint8_t exported[sizeof( size_t )];
size_t exported_length;
mbedtls_svc_key_id_t key, returned_key_id;
PSA_ASSERT( psa_crypto_init( ) );
psa_set_key_usage_flags( &attributes, PSA_KEY_USAGE_EXPORT );
psa_set_key_algorithm( &attributes, 0 );
psa_set_key_type( &attributes, PSA_KEY_TYPE_RAW_DATA );
/*
* Create PSA_KEY_SLOT_COUNT persistent keys.
*/
for( i = 0; i < PSA_KEY_SLOT_COUNT; i++ )
{
key = mbedtls_svc_key_id_make( i, i + 1 );
psa_set_key_id( &attributes, key );
PSA_ASSERT( psa_import_key( &attributes,
(uint8_t *) &i, sizeof( i ),
&returned_key_id ) );
TEST_ASSERT( mbedtls_svc_key_id_equal( returned_key_id, key ) );
}
/*
* Create a new persistent or volatile key. When creating the key,
* one of the description of the previously created persistent key
* is removed from the RAM key slots. This makes room to store its
* description in RAM.
*/
i = PSA_KEY_SLOT_COUNT;
key = mbedtls_svc_key_id_make( i, i + 1 );
psa_set_key_id( &attributes, key );
if( lifetime == PSA_KEY_LIFETIME_VOLATILE )
psa_set_key_lifetime( &attributes, PSA_KEY_LIFETIME_VOLATILE );
PSA_ASSERT( psa_import_key( &attributes,
(uint8_t *) &i, sizeof( i ),
&returned_key_id ) );
if( lifetime != PSA_KEY_LIFETIME_VOLATILE )
TEST_ASSERT( mbedtls_svc_key_id_equal( returned_key_id, key ) );
/*
* Check that we can export all ( PSA_KEY_SLOT_COUNT + 1 ) keys,
* that they have the expected value and destroy them. In that process,
* the description of the persistent key that was evicted from the RAM
* slots when creating the last key is restored in a RAM slot to export
* its value.
*/
for( i = 0; i <= PSA_KEY_SLOT_COUNT; i++ )
{
if( i < PSA_KEY_SLOT_COUNT )
key = mbedtls_svc_key_id_make( i, i + 1 );
else
key = returned_key_id;
PSA_ASSERT( psa_export_key( key,
exported, sizeof( exported ),
&exported_length ) );
ASSERT_COMPARE( exported, exported_length,
(uint8_t *) &i, sizeof( i ) );
PSA_ASSERT( psa_destroy_key( key ) );
}
exit:
PSA_DONE( );
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_PSA_CRYPTO_STORAGE_C */
void non_reusable_key_slots_integrity_in_case_of_key_slot_starvation( )
{
psa_status_t status;
size_t i;
psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
uint8_t exported[sizeof( size_t )];
size_t exported_length;
mbedtls_svc_key_id_t permanent_key = MBEDTLS_SVC_KEY_ID_INIT;
mbedtls_svc_key_id_t permanent_key2 = MBEDTLS_SVC_KEY_ID_INIT;
mbedtls_svc_key_id_t returned_key_id = MBEDTLS_SVC_KEY_ID_INIT;
mbedtls_svc_key_id_t *keys = NULL;
TEST_ASSERT( PSA_KEY_SLOT_COUNT >= 1 );
ASSERT_ALLOC( keys, PSA_KEY_SLOT_COUNT );
PSA_ASSERT( psa_crypto_init( ) );
psa_set_key_usage_flags( &attributes,
PSA_KEY_USAGE_EXPORT | PSA_KEY_USAGE_COPY );
psa_set_key_algorithm( &attributes, 0 );
psa_set_key_type( &attributes, PSA_KEY_TYPE_RAW_DATA );
/*
* Create a permanent key
*/
permanent_key = mbedtls_svc_key_id_make( 0x100, 0x205 );
psa_set_key_id( &attributes, permanent_key );
PSA_ASSERT( psa_import_key( &attributes,
(uint8_t *) &permanent_key,
sizeof( permanent_key ),
&returned_key_id ) );
TEST_ASSERT( mbedtls_svc_key_id_equal( returned_key_id, permanent_key ) );
/*
* Create PSA_KEY_SLOT_COUNT volatile keys
*/
psa_set_key_lifetime( &attributes, PSA_KEY_LIFETIME_VOLATILE );
for( i = 0; i < PSA_KEY_SLOT_COUNT; i++ )
{
PSA_ASSERT( psa_import_key( &attributes,
(uint8_t *) &i, sizeof( i ),
&keys[i]) );
}
psa_reset_key_attributes( &attributes );
/*
* Check that we cannot access the persistent key as all slots are
* occupied by volatile keys and the implementation needs to load the
* persistent key description in a slot to be able to access it.
*/
status = psa_get_key_attributes( permanent_key, &attributes );
TEST_EQUAL( status, PSA_ERROR_INSUFFICIENT_MEMORY );
/*
* Check we can export the volatile key created last and that it has the
* expected value. Then, destroy it.
*/
PSA_ASSERT( psa_export_key( keys[PSA_KEY_SLOT_COUNT - 1],
exported, sizeof( exported ),
&exported_length ) );
i = PSA_KEY_SLOT_COUNT - 1;
ASSERT_COMPARE( exported, exported_length, (uint8_t *) &i, sizeof( i ) );
PSA_ASSERT( psa_destroy_key( keys[PSA_KEY_SLOT_COUNT - 1] ) );
/*
* Check that we can now access the persistent key again.
*/
PSA_ASSERT( psa_get_key_attributes( permanent_key, &attributes ) );
TEST_ASSERT( mbedtls_svc_key_id_equal( attributes.core.id,
permanent_key ) );
/*
* Check that we cannot copy the persistent key as all slots are occupied
* by the permanent key and the volatile keys and the slot containing the
* permanent key cannot be reclaimed as it contains the key to copy.
*/
permanent_key2 = mbedtls_svc_key_id_make( 0x100, 0x204 );
psa_set_key_id( &attributes, permanent_key2 );
status = psa_copy_key( permanent_key, &attributes, &returned_key_id );
TEST_EQUAL( status, PSA_ERROR_INSUFFICIENT_MEMORY );
/*
* Check we can export the remaining volatile keys and that they have the
* expected values.
*/
for( i = 0; i < ( PSA_KEY_SLOT_COUNT - 1 ); i++ )
{
PSA_ASSERT( psa_export_key( keys[i],
exported, sizeof( exported ),
&exported_length ) );
ASSERT_COMPARE( exported, exported_length,
(uint8_t *) &i, sizeof( i ) );
PSA_ASSERT( psa_destroy_key( keys[i] ) );
}
/*
* Check we can export the persistent key and that it have the expected
* value.
*/
PSA_ASSERT( psa_export_key( permanent_key, exported, sizeof( exported ),
&exported_length ) );
ASSERT_COMPARE( exported, exported_length,
(uint8_t *) &permanent_key, sizeof( permanent_key ) );
exit:
psa_destroy_key( permanent_key );
PSA_DONE( );
mbedtls_free( keys );
}
/* END_CASE */