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mbedtls/library/psa_crypto_slot_management.c
Ronald Cron e6e6b75ad3 psa: Remove MBEDTLS_PSA_CRYPTO_DRIVERS configuration option 
The support for the PSA crypto driver interface
is not optional anymore as the implementation of
the PSA cryptography interface has been restructured
around the PSA crypto driver interface (see
psa-crypto-implementation-structure.md). There is
thus no purpose for the configuration options
MBEDTLS_PSA_CRYPTO_DRIVERS anymore.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
2023-03-31 09:07:54 +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.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>
#include "mbedtls/platform.h"
#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;
}
} else {
/* Add implicit usage flags. */
psa_extend_key_usage_flags(&(*p_slot)->attr.policy.usage);
}
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. Assert with
* MBEDTLS_TEST_HOOK_TEST_ASSERT that the lock counter is strictly greater
* than zero: if the MBEDTLS_TEST_HOOKS configuration option is enabled and
* the function is called as part of the execution of a test suite, the
* execution of the test suite is stopped in error if the assertion fails.
*/
MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->lock_count > 0);
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 */
/* Key location for external keys gets checked by the wrapper */
return PSA_SUCCESS;
} 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)
if (PSA_KEY_LIFETIME_IS_READ_ONLY(lifetime)) {
return PSA_ERROR_INVALID_ARGUMENT;
} else {
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) || \
defined(MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS)
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 /* MBEDTLS_PSA_CRYPTO_STORAGE_C || MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
(void) key;
*handle = PSA_KEY_HANDLE_INIT;
return PSA_ERROR_NOT_SUPPORTED;
#endif /* MBEDTLS_PSA_CRYPTO_STORAGE_C || MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS */
}
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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