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mbedtls/library/psa_crypto_slot_management.c
Gilles Peskine 7934b3f9f9 Fix mbedtls_psa_get_stats for keys with fancy lifetimes 
mbedtls_psa_get_stats() was written back before lifetimes were
structured as persistence and location. Fix its classification of
volatile external keys and internal keys with a non-default
persistence.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
2021-05-27 21:10:09 +02:00

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/*
* PSA crypto layer on top of Mbed TLS crypto
*/
/*
* Copyright The Mbed TLS Contributors
* 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.
*/
#include "common.h"
#if defined(MBEDTLS_PSA_CRYPTO_C)
#include "psa_crypto_service_integration.h"
#include "psa/crypto.h"
#include "psa_crypto_core.h"
#include "psa_crypto_driver_wrappers.h"
#include "psa_crypto_slot_management.h"
#include "psa_crypto_storage.h"
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
#include "psa_crypto_se.h"
#endif
#include <stdlib.h>
#include <string.h>
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#define mbedtls_calloc calloc
#define mbedtls_free free
#endif
#define ARRAY_LENGTH( array ) ( sizeof( array ) / sizeof( *( array ) ) )
typedef struct
{
psa_key_slot_t key_slots[MBEDTLS_PSA_KEY_SLOT_COUNT];
unsigned key_slots_initialized : 1;
} psa_global_data_t;
static psa_global_data_t global_data;
int psa_is_valid_key_id( mbedtls_svc_key_id_t key, int vendor_ok )
{
psa_key_id_t key_id = MBEDTLS_SVC_KEY_ID_GET_KEY_ID( key );
if( ( PSA_KEY_ID_USER_MIN <= key_id ) &&
( key_id <= PSA_KEY_ID_USER_MAX ) )
return( 1 );
if( vendor_ok &&
( PSA_KEY_ID_VENDOR_MIN <= key_id ) &&
( key_id <= PSA_KEY_ID_VENDOR_MAX ) )
return( 1 );
return( 0 );
}
/** Get the description in memory of a key given its identifier and lock it.
*
* The descriptions of volatile keys and loaded persistent keys are
* stored in key slots. This function returns a pointer to the key slot
* containing the description of a key given its identifier.
*
* The function searches the key slots containing the description of the key
* with \p key identifier. The function does only read accesses to the key
* slots. The function does not load any persistent key thus does not access
* any storage.
*
* For volatile key identifiers, only one key slot is queried as a volatile
* key with identifier key_id can only be stored in slot of index
* ( key_id - #PSA_KEY_ID_VOLATILE_MIN ).
*
* On success, the function locks the key slot. It is the responsibility of
* the caller to unlock the key slot when it does not access it anymore.
*
* \param key Key identifier to query.
* \param[out] p_slot On success, `*p_slot` contains a pointer to the
* key slot containing the description of the key
* identified by \p key.
*
* \retval #PSA_SUCCESS
* The pointer to the key slot containing the description of the key
* identified by \p key was returned.
* \retval #PSA_ERROR_INVALID_HANDLE
* \p key is not a valid key identifier.
* \retval #PSA_ERROR_DOES_NOT_EXIST
* There is no key with key identifier \p key in the key slots.
*/
static psa_status_t psa_get_and_lock_key_slot_in_memory(
mbedtls_svc_key_id_t key, psa_key_slot_t **p_slot )
{
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_id_t key_id = MBEDTLS_SVC_KEY_ID_GET_KEY_ID( key );
size_t slot_idx;
psa_key_slot_t *slot = NULL;
if( psa_key_id_is_volatile( key_id ) )
{
slot = &global_data.key_slots[ key_id - PSA_KEY_ID_VOLATILE_MIN ];
/*
* Check if both the PSA key identifier key_id and the owner
* identifier of key match those of the key slot.
*
* Note that, if the key slot is not occupied, its PSA key identifier
* is equal to zero. This is an invalid value for a PSA key identifier
* and thus cannot be equal to the valid PSA key identifier key_id.
*/
status = mbedtls_svc_key_id_equal( key, slot->attr.id ) ?
PSA_SUCCESS : PSA_ERROR_DOES_NOT_EXIST;
}
else
{
if ( !psa_is_valid_key_id( key, 1 ) )
return( PSA_ERROR_INVALID_HANDLE );
for( slot_idx = 0; slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT; slot_idx++ )
{
slot = &global_data.key_slots[ slot_idx ];
if( mbedtls_svc_key_id_equal( key, slot->attr.id ) )
break;
}
status = ( slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT ) ?
PSA_SUCCESS : PSA_ERROR_DOES_NOT_EXIST;
}
if( status == PSA_SUCCESS )
{
status = psa_lock_key_slot( slot );
if( status == PSA_SUCCESS )
*p_slot = slot;
}
return( status );
}
psa_status_t psa_initialize_key_slots( void )
{
/* Nothing to do: program startup and psa_wipe_all_key_slots() both
* guarantee that the key slots are initialized to all-zero, which
* means that all the key slots are in a valid, empty state. */
global_data.key_slots_initialized = 1;
return( PSA_SUCCESS );
}
void psa_wipe_all_key_slots( void )
{
size_t slot_idx;
for( slot_idx = 0; slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT; slot_idx++ )
{
psa_key_slot_t *slot = &global_data.key_slots[ slot_idx ];
slot->lock_count = 1;
(void) psa_wipe_key_slot( slot );
}
global_data.key_slots_initialized = 0;
}
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, *unlocked_persistent_key_slot;
if( ! global_data.key_slots_initialized )
{
status = PSA_ERROR_BAD_STATE;
goto error;
}
selected_slot = unlocked_persistent_key_slot = NULL;
for( slot_idx = 0; slot_idx < MBEDTLS_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( ( unlocked_persistent_key_slot == NULL ) &&
( ! PSA_KEY_LIFETIME_IS_VOLATILE( slot->attr.lifetime ) ) &&
( ! psa_is_key_slot_locked( slot ) ) )
unlocked_persistent_key_slot = slot;
}
/*
* If there is no unused key slot and there is at least one unlocked key
* slot containing the description of a persistent key, recycle the first
* such key slot we encountered. If we later need to operate on the
* persistent key we are evicting now, we will reload its description from
* storage.
*/
if( ( selected_slot == NULL ) &&
( unlocked_persistent_key_slot != NULL ) )
{
selected_slot = unlocked_persistent_key_slot;
selected_slot->lock_count = 1;
psa_wipe_key_slot( selected_slot );
}
if( selected_slot != NULL )
{
status = psa_lock_key_slot( selected_slot );
if( status != PSA_SUCCESS )
goto error;
*volatile_key_id = PSA_KEY_ID_VOLATILE_MIN +
( (psa_key_id_t)( selected_slot - global_data.key_slots ) );
*p_slot = selected_slot;
return( PSA_SUCCESS );
}
status = PSA_ERROR_INSUFFICIENT_MEMORY;
error:
*p_slot = NULL;
*volatile_key_id = 0;
return( status );
}
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
static psa_status_t psa_load_persistent_key_into_slot( psa_key_slot_t *slot )
{
psa_status_t status = PSA_SUCCESS;
uint8_t *key_data = NULL;
size_t key_data_length = 0;
status = psa_load_persistent_key( &slot->attr,
&key_data, &key_data_length );
if( status != PSA_SUCCESS )
goto exit;
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
/* Special handling is required for loading keys associated with a
* dynamically registered SE interface. */
const psa_drv_se_t *drv;
psa_drv_se_context_t *drv_context;
if( psa_get_se_driver( slot->attr.lifetime, &drv, &drv_context ) )
{
psa_se_key_data_storage_t *data;
if( key_data_length != sizeof( *data ) )
{
status = PSA_ERROR_DATA_INVALID;
goto exit;
}
data = (psa_se_key_data_storage_t *) key_data;
status = psa_copy_key_material_into_slot(
slot, data->slot_number, sizeof( data->slot_number ) );
goto exit;
}
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
status = psa_copy_key_material_into_slot( slot, key_data, key_data_length );
exit:
psa_free_persistent_key_data( key_data, key_data_length );
return( status );
}
#endif /* MBEDTLS_PSA_CRYPTO_STORAGE_C */
#if defined(MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS)
static psa_status_t psa_load_builtin_key_into_slot( psa_key_slot_t *slot )
{
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
psa_key_lifetime_t lifetime = PSA_KEY_LIFETIME_VOLATILE;
psa_drv_slot_number_t slot_number = 0;
size_t key_buffer_size = 0;
size_t key_buffer_length = 0;
if( ! psa_key_id_is_builtin(
MBEDTLS_SVC_KEY_ID_GET_KEY_ID( slot->attr.id ) ) )
{
return( PSA_ERROR_DOES_NOT_EXIST );
}
/* Check the platform function to see whether this key actually exists */
status = mbedtls_psa_platform_get_builtin_key(
slot->attr.id, &lifetime, &slot_number );
if( status != PSA_SUCCESS )
return( status );
/* Set required key attributes to ensure get_builtin_key can retrieve the
* full attributes. */
psa_set_key_id( &attributes, slot->attr.id );
psa_set_key_lifetime( &attributes, lifetime );
/* Get the full key attributes from the driver in order to be able to
* calculate the required buffer size. */
status = psa_driver_wrapper_get_builtin_key(
slot_number, &attributes,
NULL, 0, NULL );
if( status != PSA_ERROR_BUFFER_TOO_SMALL )
{
/* Builtin keys cannot be defined by the attributes alone */
if( status == PSA_SUCCESS )
status = PSA_ERROR_CORRUPTION_DETECTED;
return( status );
}
/* If the key should exist according to the platform, then ask the driver
* what its expected size is. */
status = psa_driver_wrapper_get_key_buffer_size( &attributes,
&key_buffer_size );
if( status != PSA_SUCCESS )
return( status );
/* Allocate a buffer of the required size and load the builtin key directly
* into the (now properly sized) slot buffer. */
status = psa_allocate_buffer_to_slot( slot, key_buffer_size );
if( status != PSA_SUCCESS )
return( status );
status = psa_driver_wrapper_get_builtin_key(
slot_number, &attributes,
slot->key.data, slot->key.bytes, &key_buffer_length );
if( status != PSA_SUCCESS )
goto exit;
/* Copy actual key length and core attributes into the slot on success */
slot->key.bytes = key_buffer_length;
slot->attr = attributes.core;
exit:
if( status != PSA_SUCCESS )
psa_remove_key_data_from_memory( slot );
return( status );
}
#endif /* MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
psa_status_t psa_get_and_lock_key_slot( mbedtls_svc_key_id_t key,
psa_key_slot_t **p_slot )
{
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
*p_slot = NULL;
if( ! global_data.key_slots_initialized )
return( PSA_ERROR_BAD_STATE );
/*
* On success, the pointer to the slot is passed directly to the caller
* thus no need to unlock the key slot here.
*/
status = psa_get_and_lock_key_slot_in_memory( key, p_slot );
if( status != PSA_ERROR_DOES_NOT_EXIST )
return( status );
/* Loading keys from storage requires support for such a mechanism */
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) || \
defined(MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS)
psa_key_id_t volatile_key_id;
status = psa_get_empty_key_slot( &volatile_key_id, p_slot );
if( status != PSA_SUCCESS )
return( status );
(*p_slot)->attr.id = key;
(*p_slot)->attr.lifetime = PSA_KEY_LIFETIME_PERSISTENT;
status = PSA_ERROR_DOES_NOT_EXIST;
#if defined(MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS)
/* Load keys in the 'builtin' range through their own interface */
status = psa_load_builtin_key_into_slot( *p_slot );
#endif /* MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
if( status == PSA_ERROR_DOES_NOT_EXIST )
status = psa_load_persistent_key_into_slot( *p_slot );
#endif /* defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */
if( status != PSA_SUCCESS )
{
psa_wipe_key_slot( *p_slot );
if( status == PSA_ERROR_DOES_NOT_EXIST )
status = PSA_ERROR_INVALID_HANDLE;
}
return( status );
#else /* MBEDTLS_PSA_CRYPTO_STORAGE_C || MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
return( PSA_ERROR_INVALID_HANDLE );
#endif /* MBEDTLS_PSA_CRYPTO_STORAGE_C || MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
}
psa_status_t psa_unlock_key_slot( psa_key_slot_t *slot )
{
if( slot == NULL )
return( PSA_SUCCESS );
if( slot->lock_count > 0 )
{
slot->lock_count--;
return( PSA_SUCCESS );
}
/*
* As the return error code may not be handled in case of multiple errors,
* do our best to report if the lock counter is equal to zero: if
* available call MBEDTLS_PARAM_FAILED that may terminate execution (if
* called as part of the execution of a unit test suite this will stop the
* test suite execution).
*/
#ifdef MBEDTLS_CHECK_PARAMS
MBEDTLS_PARAM_FAILED( slot->lock_count > 0 );
#endif
return( PSA_ERROR_CORRUPTION_DETECTED );
}
psa_status_t psa_validate_key_location( psa_key_lifetime_t lifetime,
psa_se_drv_table_entry_t **p_drv )
{
if ( psa_key_lifetime_is_external( lifetime ) )
{
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
/* Check whether a driver is registered against this lifetime */
psa_se_drv_table_entry_t *driver = psa_get_se_driver_entry( lifetime );
if( driver != NULL )
{
if (p_drv != NULL)
*p_drv = driver;
return( PSA_SUCCESS );
}
#else /* MBEDTLS_PSA_CRYPTO_SE_C */
(void) p_drv;
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
#if defined(MBEDTLS_PSA_CRYPTO_DRIVERS)
/* Key location for external keys gets checked by the wrapper */
return( PSA_SUCCESS );
#else /* MBEDTLS_PSA_CRYPTO_DRIVERS */
/* No support for external lifetimes at all, or dynamic interface
* did not find driver for requested lifetime. */
return( PSA_ERROR_INVALID_ARGUMENT );
#endif /* MBEDTLS_PSA_CRYPTO_DRIVERS */
}
else
/* Local/internal keys are always valid */
return( PSA_SUCCESS );
}
psa_status_t psa_validate_key_persistence( psa_key_lifetime_t lifetime )
{
if ( PSA_KEY_LIFETIME_IS_VOLATILE( lifetime ) )
{
/* Volatile keys are always supported */
return( PSA_SUCCESS );
}
else
{
/* Persistent keys require storage support */
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
return( PSA_SUCCESS );
#else /* MBEDTLS_PSA_CRYPTO_STORAGE_C */
return( PSA_ERROR_NOT_SUPPORTED );
#endif /* !MBEDTLS_PSA_CRYPTO_STORAGE_C */
}
}
psa_status_t psa_open_key( mbedtls_svc_key_id_t key, psa_key_handle_t *handle )
{
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
psa_status_t status;
psa_key_slot_t *slot;
status = psa_get_and_lock_key_slot( key, &slot );
if( status != PSA_SUCCESS )
{
*handle = PSA_KEY_HANDLE_INIT;
if( status == PSA_ERROR_INVALID_HANDLE )
status = PSA_ERROR_DOES_NOT_EXIST;
return( status );
}
*handle = key;
return( psa_unlock_key_slot( slot ) );
#else /* defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */
(void) key;
*handle = PSA_KEY_HANDLE_INIT;
return( PSA_ERROR_NOT_SUPPORTED );
#endif /* !defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */
}
psa_status_t psa_close_key( psa_key_handle_t handle )
{
psa_status_t status;
psa_key_slot_t *slot;
if( psa_key_handle_is_null( handle ) )
return( PSA_SUCCESS );
status = psa_get_and_lock_key_slot_in_memory( handle, &slot );
if( status != PSA_SUCCESS )
{
if( status == PSA_ERROR_DOES_NOT_EXIST )
status = PSA_ERROR_INVALID_HANDLE;
return( status );
}
if( slot->lock_count <= 1 )
return( psa_wipe_key_slot( slot ) );
else
return( psa_unlock_key_slot( slot ) );
}
psa_status_t psa_purge_key( mbedtls_svc_key_id_t key )
{
psa_status_t status;
psa_key_slot_t *slot;
status = psa_get_and_lock_key_slot_in_memory( key, &slot );
if( status != PSA_SUCCESS )
return( status );
if( ( ! PSA_KEY_LIFETIME_IS_VOLATILE( slot->attr.lifetime ) ) &&
( slot->lock_count <= 1 ) )
return( psa_wipe_key_slot( slot ) );
else
return( psa_unlock_key_slot( slot ) );
}
void mbedtls_psa_get_stats( mbedtls_psa_stats_t *stats )
{
size_t slot_idx;
memset( stats, 0, sizeof( *stats ) );
for( slot_idx = 0; slot_idx < MBEDTLS_PSA_KEY_SLOT_COUNT; slot_idx++ )
{
const psa_key_slot_t *slot = &global_data.key_slots[ slot_idx ];
if( psa_is_key_slot_locked( slot ) )
{
++stats->locked_slots;
}
if( ! psa_is_key_slot_occupied( slot ) )
{
++stats->empty_slots;
continue;
}
if( PSA_KEY_LIFETIME_IS_VOLATILE( slot->attr.lifetime ) )
++stats->volatile_slots;
else
{
psa_key_id_t id = MBEDTLS_SVC_KEY_ID_GET_KEY_ID( slot->attr.id );
++stats->persistent_slots;
if( id > stats->max_open_internal_key_id )
stats->max_open_internal_key_id = id;
}
if( PSA_KEY_LIFETIME_GET_LOCATION( slot->attr.lifetime ) !=
PSA_KEY_LOCATION_LOCAL_STORAGE )
{
psa_key_id_t id = MBEDTLS_SVC_KEY_ID_GET_KEY_ID( slot->attr.id );
++stats->external_slots;
if( id > stats->max_open_external_key_id )
stats->max_open_external_key_id = id;
}
}
}
#endif /* MBEDTLS_PSA_CRYPTO_C */
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