373 lines
12 KiB
C
373 lines
12 KiB
C
/*
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* PSA crypto support for secure element drivers
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*/
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/*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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#include "common.h"
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#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
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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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/****************************************************************/
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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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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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struct psa_se_drv_table_entry_s {
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psa_key_location_t location;
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const psa_drv_se_t *methods;
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union {
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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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} u;
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};
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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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psa_key_location_t location = PSA_KEY_LIFETIME_GET_LOCATION(lifetime);
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/* In the driver table, location=0 means an entry that isn't used.
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* No driver has a location of 0 because it's a reserved value
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* (which designates transparent keys). Make sure we never return
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* a driver entry for location 0. */
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if (location == 0) {
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return NULL;
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}
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for (i = 0; i < PSA_MAX_SE_DRIVERS; i++) {
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if (driver_table[i].location == location) {
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return &driver_table[i];
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}
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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->u.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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}
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if (p_drv_context != NULL) {
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*p_drv_context = (driver ? &driver->u.context : NULL);
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}
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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->location > PSA_MAX_SE_LOCATION) {
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return PSA_ERROR_NOT_SUPPORTED;
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}
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/* ITS file sizes are limited to 32 bits. */
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if (driver->u.internal.persistent_data_size > UINT32_MAX) {
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return PSA_ERROR_NOT_SUPPORTED;
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}
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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->location;
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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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}
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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->u.internal.persistent_data_size,
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driver->u.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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}
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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->u.internal.persistent_data_size,
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driver->u.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_location_t location)
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{
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psa_storage_uid_t uid;
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if (location > PSA_MAX_SE_LOCATION) {
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return PSA_ERROR_NOT_SUPPORTED;
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}
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uid = PSA_CRYPTO_SE_DRIVER_ITS_UID_BASE + location;
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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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psa_key_location_t key_location =
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PSA_KEY_LIFETIME_GET_LOCATION(psa_get_key_lifetime(attributes));
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/* If the location is wrong, it's a bug in the library. */
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if (driver->location != key_location) {
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return PSA_ERROR_CORRUPTION_DETECTED;
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}
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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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}
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if (psa_get_key_slot_number(attributes, slot_number) == PSA_SUCCESS) {
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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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}
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status = p_validate_slot_number(&driver->u.context,
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driver->u.internal.persistent_data,
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attributes, method,
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*slot_number);
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} else if (method == PSA_KEY_CREATION_REGISTER) {
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/* The application didn't specify a slot number. This doesn't
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* make sense when registering a slot. */
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return PSA_ERROR_INVALID_ARGUMENT;
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} else {
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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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}
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status = p_allocate(&driver->u.context,
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driver->u.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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}
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status = driver->methods->key_management->p_destroy(
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&driver->u.context,
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driver->u.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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psa_status_t psa_init_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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psa_se_drv_table_entry_t *driver = &driver_table[i];
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if (driver->location == 0) {
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continue; /* skipping unused entry */
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}
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const psa_drv_se_t *methods = psa_get_se_driver_methods(driver);
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if (methods->p_init != NULL) {
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psa_status_t status = methods->p_init(
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&driver->u.context,
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driver->u.internal.persistent_data,
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driver->location);
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if (status != PSA_SUCCESS) {
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return status;
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}
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status = psa_save_se_persistent_data(driver);
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if (status != PSA_SUCCESS) {
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return status;
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}
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}
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}
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return PSA_SUCCESS;
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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_location_t location,
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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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}
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/* Driver table entries are 0-initialized. 0 is not a valid driver
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* location because it means a transparent key. */
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MBEDTLS_STATIC_ASSERT(PSA_KEY_LOCATION_LOCAL_STORAGE == 0,
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"Secure element support requires 0 to mean a local key");
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if (location == PSA_KEY_LOCATION_LOCAL_STORAGE) {
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return PSA_ERROR_INVALID_ARGUMENT;
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}
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if (location > PSA_MAX_SE_LOCATION) {
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return PSA_ERROR_NOT_SUPPORTED;
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}
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for (i = 0; i < PSA_MAX_SE_DRIVERS; i++) {
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if (driver_table[i].location == 0) {
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break;
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}
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/* Check that location 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].location == location) {
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return PSA_ERROR_ALREADY_EXISTS;
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}
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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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}
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driver_table[i].location = location;
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driver_table[i].methods = methods;
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driver_table[i].u.internal.persistent_data_size =
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methods->persistent_data_size;
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if (methods->persistent_data_size != 0) {
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driver_table[i].u.internal.persistent_data =
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mbedtls_calloc(1, methods->persistent_data_size);
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if (driver_table[i].u.internal.persistent_data == NULL) {
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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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}
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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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if (driver_table[i].u.internal.persistent_data != NULL) {
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mbedtls_free(driver_table[i].u.internal.persistent_data);
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}
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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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