e88c2c1338
Pass the key creation method (import/generate/derive/copy) to the driver methods to allocate or validate a slot number. This allows drivers to enforce policies such as "this key slot can only be used for keys generated inside the secure element".
356 lines
12 KiB
C
356 lines
12 KiB
C
/*
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* PSA crypto support for secure element drivers
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*/
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/* Copyright (C) 2019, ARM Limited, All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of Mbed TLS (https://tls.mbed.org)
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*/
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#if !defined(MBEDTLS_CONFIG_FILE)
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#include "mbedtls/config.h"
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#else
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#include MBEDTLS_CONFIG_FILE
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#endif
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#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
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#include <assert.h>
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#include <stdint.h>
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#include <string.h>
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#include "psa/crypto_se_driver.h"
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#include "psa_crypto_se.h"
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#if defined(MBEDTLS_PSA_ITS_FILE_C)
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#include "psa_crypto_its.h"
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#else /* Native ITS implementation */
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#include "psa/error.h"
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#include "psa/internal_trusted_storage.h"
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#endif
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#include "mbedtls/platform.h"
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#if !defined(MBEDTLS_PLATFORM_C)
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#define mbedtls_calloc calloc
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#define mbedtls_free free
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#endif
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/****************************************************************/
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/* Driver lookup */
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/****************************************************************/
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/* This structure is identical to psa_drv_se_context_t declared in
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* `crypto_se_driver.h`, except that some parts are writable here
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* (non-const, or pointer to non-const). */
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typedef struct
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{
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void *persistent_data;
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size_t persistent_data_size;
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uintptr_t transient_data;
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} psa_drv_se_internal_context_t;
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typedef struct psa_se_drv_table_entry_s
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{
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psa_key_lifetime_t lifetime;
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const psa_drv_se_t *methods;
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union
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{
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psa_drv_se_internal_context_t internal;
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psa_drv_se_context_t context;
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};
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} psa_se_drv_table_entry_t;
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static psa_se_drv_table_entry_t driver_table[PSA_MAX_SE_DRIVERS];
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psa_se_drv_table_entry_t *psa_get_se_driver_entry(
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psa_key_lifetime_t lifetime )
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{
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size_t i;
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/* In the driver table, lifetime=0 means an entry that isn't used.
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* No driver has a lifetime of 0 because it's a reserved value
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* (which designates volatile keys). Make sure we never return
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* a driver entry for lifetime 0. */
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if( lifetime == 0 )
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return( NULL );
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for( i = 0; i < PSA_MAX_SE_DRIVERS; i++ )
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{
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if( driver_table[i].lifetime == lifetime )
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return( &driver_table[i] );
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}
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return( NULL );
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}
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const psa_drv_se_t *psa_get_se_driver_methods(
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const psa_se_drv_table_entry_t *driver )
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{
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return( driver->methods );
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}
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psa_drv_se_context_t *psa_get_se_driver_context(
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psa_se_drv_table_entry_t *driver )
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{
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return( &driver->context );
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}
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int psa_get_se_driver( psa_key_lifetime_t lifetime,
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const psa_drv_se_t **p_methods,
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psa_drv_se_context_t **p_drv_context)
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{
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psa_se_drv_table_entry_t *driver = psa_get_se_driver_entry( lifetime );
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if( p_methods != NULL )
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*p_methods = ( driver ? driver->methods : NULL );
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if( p_drv_context != NULL )
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*p_drv_context = ( driver ? &driver->context : NULL );
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return( driver != NULL );
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}
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/****************************************************************/
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/* Persistent data management */
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/****************************************************************/
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static psa_status_t psa_get_se_driver_its_file_uid(
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const psa_se_drv_table_entry_t *driver,
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psa_storage_uid_t *uid )
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{
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if( driver->lifetime > PSA_MAX_SE_LIFETIME )
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return( PSA_ERROR_NOT_SUPPORTED );
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#if SIZE_MAX > UINT32_MAX
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/* ITS file sizes are limited to 32 bits. */
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if( driver->internal.persistent_data_size > UINT32_MAX )
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return( PSA_ERROR_NOT_SUPPORTED );
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#endif
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/* See the documentation of PSA_CRYPTO_SE_DRIVER_ITS_UID_BASE. */
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*uid = PSA_CRYPTO_SE_DRIVER_ITS_UID_BASE + driver->lifetime;
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return( PSA_SUCCESS );
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}
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psa_status_t psa_load_se_persistent_data(
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const psa_se_drv_table_entry_t *driver )
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{
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psa_status_t status;
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psa_storage_uid_t uid;
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size_t length;
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status = psa_get_se_driver_its_file_uid( driver, &uid );
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if( status != PSA_SUCCESS )
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return( status );
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/* Read the amount of persistent data that the driver requests.
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* If the data in storage is larger, it is truncated. If the data
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* in storage is smaller, silently keep what is already at the end
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* of the output buffer. */
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/* psa_get_se_driver_its_file_uid ensures that the size_t
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* persistent_data_size is in range, but compilers don't know that,
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* so cast to reassure them. */
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return( psa_its_get( uid, 0,
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(uint32_t) driver->internal.persistent_data_size,
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driver->internal.persistent_data,
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&length ) );
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}
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psa_status_t psa_save_se_persistent_data(
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const psa_se_drv_table_entry_t *driver )
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{
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psa_status_t status;
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psa_storage_uid_t uid;
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status = psa_get_se_driver_its_file_uid( driver, &uid );
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if( status != PSA_SUCCESS )
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return( status );
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/* psa_get_se_driver_its_file_uid ensures that the size_t
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* persistent_data_size is in range, but compilers don't know that,
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* so cast to reassure them. */
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return( psa_its_set( uid,
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(uint32_t) driver->internal.persistent_data_size,
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driver->internal.persistent_data,
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0 ) );
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}
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psa_status_t psa_destroy_se_persistent_data( psa_key_lifetime_t lifetime )
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{
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psa_storage_uid_t uid;
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if( lifetime > PSA_MAX_SE_LIFETIME )
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return( PSA_ERROR_NOT_SUPPORTED );
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uid = PSA_CRYPTO_SE_DRIVER_ITS_UID_BASE + lifetime;
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return( psa_its_remove( uid ) );
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}
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psa_status_t psa_find_se_slot_for_key(
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const psa_key_attributes_t *attributes,
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psa_key_creation_method_t method,
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psa_se_drv_table_entry_t *driver,
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psa_key_slot_number_t *slot_number )
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{
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psa_status_t status;
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/* If the lifetime is wrong, it's a bug in the library. */
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if( driver->lifetime != psa_get_key_lifetime( attributes ) )
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return( PSA_ERROR_CORRUPTION_DETECTED );
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/* If the driver doesn't support key creation in any way, give up now. */
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if( driver->methods->key_management == NULL )
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return( PSA_ERROR_NOT_SUPPORTED );
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if( psa_get_key_slot_number( attributes, slot_number ) == PSA_SUCCESS )
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{
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/* The application wants to use a specific slot. Allow it if
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* the driver supports it. On a system with isolation,
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* the crypto service must check that the application is
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* permitted to request this slot. */
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psa_drv_se_validate_slot_number_t p_validate_slot_number =
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driver->methods->key_management->p_validate_slot_number;
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if( p_validate_slot_number == NULL )
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return( PSA_ERROR_NOT_SUPPORTED );
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status = p_validate_slot_number( &driver->context,
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attributes, method,
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*slot_number );
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}
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else
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{
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/* The application didn't tell us which slot to use. Let the driver
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* choose. This is the normal case. */
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psa_drv_se_allocate_key_t p_allocate =
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driver->methods->key_management->p_allocate;
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if( p_allocate == NULL )
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return( PSA_ERROR_NOT_SUPPORTED );
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status = p_allocate( &driver->context,
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driver->internal.persistent_data,
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attributes, method,
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slot_number );
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}
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return( status );
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}
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psa_status_t psa_destroy_se_key( psa_se_drv_table_entry_t *driver,
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psa_key_slot_number_t slot_number )
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{
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psa_status_t status;
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psa_status_t storage_status;
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/* Normally a missing method would mean that the action is not
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* supported. But psa_destroy_key() is not supposed to return
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* PSA_ERROR_NOT_SUPPORTED: if you can create a key, you should
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* be able to destroy it. The only use case for a driver that
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* does not have a way to destroy keys at all is if the keys are
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* locked in a read-only state: we can use the keys but not
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* destroy them. Hence, if the driver doesn't support destroying
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* keys, it's really a lack of permission. */
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if( driver->methods->key_management == NULL ||
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driver->methods->key_management->p_destroy == NULL )
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return( PSA_ERROR_NOT_PERMITTED );
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status = driver->methods->key_management->p_destroy(
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&driver->context,
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driver->internal.persistent_data,
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slot_number );
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storage_status = psa_save_se_persistent_data( driver );
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return( status == PSA_SUCCESS ? storage_status : status );
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}
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/****************************************************************/
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/* Driver registration */
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/****************************************************************/
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psa_status_t psa_register_se_driver(
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psa_key_lifetime_t lifetime,
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const psa_drv_se_t *methods)
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{
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size_t i;
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psa_status_t status;
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if( methods->hal_version != PSA_DRV_SE_HAL_VERSION )
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return( PSA_ERROR_NOT_SUPPORTED );
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/* Driver table entries are 0-initialized. 0 is not a valid driver
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* lifetime because it means a volatile key. */
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#if defined(static_assert)
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static_assert( PSA_KEY_LIFETIME_VOLATILE == 0,
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"Secure element support requires 0 to mean a volatile key" );
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#endif
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if( lifetime == PSA_KEY_LIFETIME_VOLATILE ||
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lifetime == PSA_KEY_LIFETIME_PERSISTENT )
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{
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return( PSA_ERROR_INVALID_ARGUMENT );
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}
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if( lifetime > PSA_MAX_SE_LIFETIME )
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return( PSA_ERROR_NOT_SUPPORTED );
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for( i = 0; i < PSA_MAX_SE_DRIVERS; i++ )
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{
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if( driver_table[i].lifetime == 0 )
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break;
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/* Check that lifetime isn't already in use up to the first free
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* entry. Since entries are created in order and never deleted,
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* there can't be a used entry after the first free entry. */
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if( driver_table[i].lifetime == lifetime )
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return( PSA_ERROR_ALREADY_EXISTS );
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}
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if( i == PSA_MAX_SE_DRIVERS )
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return( PSA_ERROR_INSUFFICIENT_MEMORY );
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driver_table[i].lifetime = lifetime;
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driver_table[i].methods = methods;
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if( methods->persistent_data_size != 0 )
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{
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driver_table[i].internal.persistent_data =
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mbedtls_calloc( 1, methods->persistent_data_size );
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if( driver_table[i].internal.persistent_data == NULL )
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{
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status = PSA_ERROR_INSUFFICIENT_MEMORY;
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goto error;
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}
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/* Load the driver's persistent data. On first use, the persistent
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* data does not exist in storage, and is initialized to
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* all-bits-zero by the calloc call just above. */
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status = psa_load_se_persistent_data( &driver_table[i] );
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if( status != PSA_SUCCESS && status != PSA_ERROR_DOES_NOT_EXIST )
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goto error;
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}
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driver_table[i].internal.persistent_data_size =
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methods->persistent_data_size;
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return( PSA_SUCCESS );
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error:
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memset( &driver_table[i], 0, sizeof( driver_table[i] ) );
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return( status );
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}
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void psa_unregister_all_se_drivers( void )
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{
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size_t i;
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for( i = 0; i < PSA_MAX_SE_DRIVERS; i++ )
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{
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if( driver_table[i].internal.persistent_data != NULL )
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mbedtls_free( driver_table[i].internal.persistent_data );
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}
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memset( driver_table, 0, sizeof( driver_table ) );
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}
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/****************************************************************/
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/* The end */
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/****************************************************************/
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#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
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