/* * PSA crypto support for secure element drivers */ /* Copyright (C) 2019, ARM Limited, All Rights Reserved * 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. * * This file is part of Mbed TLS (https://tls.mbed.org) */ #if !defined(MBEDTLS_CONFIG_FILE) #include "mbedtls/config.h" #else #include MBEDTLS_CONFIG_FILE #endif #if defined(MBEDTLS_PSA_CRYPTO_SE_C) #include #include #include #include "psa/crypto_se_driver.h" #include "psa_crypto_se.h" #if defined(MBEDTLS_PSA_ITS_FILE_C) #include "psa_crypto_its.h" #else /* Native ITS implementation */ #include "psa/error.h" #include "psa/internal_trusted_storage.h" #endif #include "mbedtls/platform.h" #if !defined(MBEDTLS_PLATFORM_C) #define mbedtls_calloc calloc #define mbedtls_free free #endif /****************************************************************/ /* Driver lookup */ /****************************************************************/ /* This structure is identical to psa_drv_se_context_t declared in * `crypto_se_driver.h`, except that some parts are writable here * (non-const, or pointer to non-const). */ typedef struct { void *persistent_data; size_t persistent_data_size; uintptr_t transient_data; } psa_drv_se_internal_context_t; typedef struct psa_se_drv_table_entry_s { psa_key_lifetime_t lifetime; const psa_drv_se_t *methods; union { psa_drv_se_internal_context_t internal; psa_drv_se_context_t context; }; } psa_se_drv_table_entry_t; static psa_se_drv_table_entry_t driver_table[PSA_MAX_SE_DRIVERS]; psa_se_drv_table_entry_t *psa_get_se_driver_entry( psa_key_lifetime_t lifetime ) { size_t i; /* In the driver table, lifetime=0 means an entry that isn't used. * No driver has a lifetime of 0 because it's a reserved value * (which designates volatile keys). Make sure we never return * a driver entry for lifetime 0. */ if( lifetime == 0 ) return( NULL ); for( i = 0; i < PSA_MAX_SE_DRIVERS; i++ ) { if( driver_table[i].lifetime == lifetime ) return( &driver_table[i] ); } return( NULL ); } const psa_drv_se_t *psa_get_se_driver_methods( const psa_se_drv_table_entry_t *driver ) { return( driver->methods ); } psa_drv_se_context_t *psa_get_se_driver_context( psa_se_drv_table_entry_t *driver ) { return( &driver->context ); } int psa_get_se_driver( psa_key_lifetime_t lifetime, const psa_drv_se_t **p_methods, psa_drv_se_context_t **p_drv_context) { psa_se_drv_table_entry_t *driver = psa_get_se_driver_entry( lifetime ); if( p_methods != NULL ) *p_methods = ( driver ? driver->methods : NULL ); if( p_drv_context != NULL ) *p_drv_context = ( driver ? &driver->context : NULL ); return( driver != NULL ); } /****************************************************************/ /* Persistent data management */ /****************************************************************/ static psa_status_t psa_get_se_driver_its_file_uid( const psa_se_drv_table_entry_t *driver, psa_storage_uid_t *uid ) { if( driver->lifetime > PSA_MAX_SE_LIFETIME ) return( PSA_ERROR_NOT_SUPPORTED ); #if SIZE_MAX > UINT32_MAX /* ITS file sizes are limited to 32 bits. */ if( driver->internal.persistent_data_size > UINT32_MAX ) return( PSA_ERROR_NOT_SUPPORTED ); #endif /* See the documentation of PSA_CRYPTO_SE_DRIVER_ITS_UID_BASE. */ *uid = PSA_CRYPTO_SE_DRIVER_ITS_UID_BASE + driver->lifetime; return( PSA_SUCCESS ); } psa_status_t psa_load_se_persistent_data( const psa_se_drv_table_entry_t *driver ) { psa_status_t status; psa_storage_uid_t uid; size_t length; status = psa_get_se_driver_its_file_uid( driver, &uid ); if( status != PSA_SUCCESS ) return( status ); /* Read the amount of persistent data that the driver requests. * If the data in storage is larger, it is truncated. If the data * in storage is smaller, silently keep what is already at the end * of the output buffer. */ /* psa_get_se_driver_its_file_uid ensures that the size_t * persistent_data_size is in range, but compilers don't know that, * so cast to reassure them. */ return( psa_its_get( uid, 0, (uint32_t) driver->internal.persistent_data_size, driver->internal.persistent_data, &length ) ); } psa_status_t psa_save_se_persistent_data( const psa_se_drv_table_entry_t *driver ) { psa_status_t status; psa_storage_uid_t uid; status = psa_get_se_driver_its_file_uid( driver, &uid ); if( status != PSA_SUCCESS ) return( status ); /* psa_get_se_driver_its_file_uid ensures that the size_t * persistent_data_size is in range, but compilers don't know that, * so cast to reassure them. */ return( psa_its_set( uid, (uint32_t) driver->internal.persistent_data_size, driver->internal.persistent_data, 0 ) ); } psa_status_t psa_destroy_se_persistent_data( psa_key_lifetime_t lifetime ) { psa_storage_uid_t uid; if( lifetime > PSA_MAX_SE_LIFETIME ) return( PSA_ERROR_NOT_SUPPORTED ); uid = PSA_CRYPTO_SE_DRIVER_ITS_UID_BASE + lifetime; return( psa_its_remove( uid ) ); } psa_status_t psa_find_se_slot_for_key( const psa_key_attributes_t *attributes, psa_key_creation_method_t method, psa_se_drv_table_entry_t *driver, psa_key_slot_number_t *slot_number ) { psa_status_t status; /* If the lifetime is wrong, it's a bug in the library. */ if( driver->lifetime != psa_get_key_lifetime( attributes ) ) return( PSA_ERROR_CORRUPTION_DETECTED ); /* If the driver doesn't support key creation in any way, give up now. */ if( driver->methods->key_management == NULL ) return( PSA_ERROR_NOT_SUPPORTED ); if( psa_get_key_slot_number( attributes, slot_number ) == PSA_SUCCESS ) { /* The application wants to use a specific slot. Allow it if * the driver supports it. On a system with isolation, * the crypto service must check that the application is * permitted to request this slot. */ psa_drv_se_validate_slot_number_t p_validate_slot_number = driver->methods->key_management->p_validate_slot_number; if( p_validate_slot_number == NULL ) return( PSA_ERROR_NOT_SUPPORTED ); status = p_validate_slot_number( &driver->context, attributes, method, *slot_number ); } else { /* The application didn't tell us which slot to use. Let the driver * choose. This is the normal case. */ psa_drv_se_allocate_key_t p_allocate = driver->methods->key_management->p_allocate; if( p_allocate == NULL ) return( PSA_ERROR_NOT_SUPPORTED ); status = p_allocate( &driver->context, driver->internal.persistent_data, attributes, method, slot_number ); } return( status ); } psa_status_t psa_destroy_se_key( psa_se_drv_table_entry_t *driver, psa_key_slot_number_t slot_number ) { psa_status_t status; psa_status_t storage_status; /* Normally a missing method would mean that the action is not * supported. But psa_destroy_key() is not supposed to return * PSA_ERROR_NOT_SUPPORTED: if you can create a key, you should * be able to destroy it. The only use case for a driver that * does not have a way to destroy keys at all is if the keys are * locked in a read-only state: we can use the keys but not * destroy them. Hence, if the driver doesn't support destroying * keys, it's really a lack of permission. */ if( driver->methods->key_management == NULL || driver->methods->key_management->p_destroy == NULL ) return( PSA_ERROR_NOT_PERMITTED ); status = driver->methods->key_management->p_destroy( &driver->context, driver->internal.persistent_data, slot_number ); storage_status = psa_save_se_persistent_data( driver ); return( status == PSA_SUCCESS ? storage_status : status ); } /****************************************************************/ /* Driver registration */ /****************************************************************/ psa_status_t psa_register_se_driver( psa_key_lifetime_t lifetime, const psa_drv_se_t *methods) { size_t i; psa_status_t status; if( methods->hal_version != PSA_DRV_SE_HAL_VERSION ) return( PSA_ERROR_NOT_SUPPORTED ); /* Driver table entries are 0-initialized. 0 is not a valid driver * lifetime because it means a volatile key. */ #if defined(static_assert) static_assert( PSA_KEY_LIFETIME_VOLATILE == 0, "Secure element support requires 0 to mean a volatile key" ); #endif if( lifetime == PSA_KEY_LIFETIME_VOLATILE || lifetime == PSA_KEY_LIFETIME_PERSISTENT ) { return( PSA_ERROR_INVALID_ARGUMENT ); } if( lifetime > PSA_MAX_SE_LIFETIME ) return( PSA_ERROR_NOT_SUPPORTED ); for( i = 0; i < PSA_MAX_SE_DRIVERS; i++ ) { if( driver_table[i].lifetime == 0 ) break; /* Check that lifetime isn't already in use up to the first free * entry. Since entries are created in order and never deleted, * there can't be a used entry after the first free entry. */ if( driver_table[i].lifetime == lifetime ) return( PSA_ERROR_ALREADY_EXISTS ); } if( i == PSA_MAX_SE_DRIVERS ) return( PSA_ERROR_INSUFFICIENT_MEMORY ); driver_table[i].lifetime = lifetime; driver_table[i].methods = methods; if( methods->persistent_data_size != 0 ) { driver_table[i].internal.persistent_data = mbedtls_calloc( 1, methods->persistent_data_size ); if( driver_table[i].internal.persistent_data == NULL ) { status = PSA_ERROR_INSUFFICIENT_MEMORY; goto error; } /* Load the driver's persistent data. On first use, the persistent * data does not exist in storage, and is initialized to * all-bits-zero by the calloc call just above. */ status = psa_load_se_persistent_data( &driver_table[i] ); if( status != PSA_SUCCESS && status != PSA_ERROR_DOES_NOT_EXIST ) goto error; } driver_table[i].internal.persistent_data_size = methods->persistent_data_size; return( PSA_SUCCESS ); error: memset( &driver_table[i], 0, sizeof( driver_table[i] ) ); return( status ); } void psa_unregister_all_se_drivers( void ) { size_t i; for( i = 0; i < PSA_MAX_SE_DRIVERS; i++ ) { if( driver_table[i].internal.persistent_data != NULL ) mbedtls_free( driver_table[i].internal.persistent_data ); } memset( driver_table, 0, sizeof( driver_table ) ); } /****************************************************************/ /* The end */ /****************************************************************/ #endif /* MBEDTLS_PSA_CRYPTO_SE_C */