proxmark3/common/mbedtls/psa_crypto_slot_management.c

/*
 *  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_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;

psa_status_t psa_validate_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 (PSA_SUCCESS);

    if (vendor_ok &&
            (PSA_KEY_ID_VENDOR_MIN <= key_id) &&
            (key_id <= PSA_KEY_ID_VENDOR_MAX))
        return (PSA_SUCCESS);

    return (PSA_ERROR_INVALID_HANDLE);
}

/** 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 {
        status = psa_validate_key_id(key, 1);
        if (status != PSA_SUCCESS)
            return (status);

        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 */

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);

#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
    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.lifetime = PSA_KEY_LIFETIME_PERSISTENT;
    (*p_slot)->attr.id = key;

    status = psa_load_persistent_key_into_slot(*p_slot);
    if (status != PSA_SUCCESS)
        psa_wipe_key_slot(*p_slot);

    return (status);
#else
    return (PSA_ERROR_DOES_NOT_EXIST);
#endif /* defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */

}

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;
        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)
        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 (slot->attr.lifetime == PSA_KEY_LIFETIME_VOLATILE)
            ++stats->volatile_slots;
        else if (slot->attr.lifetime == PSA_KEY_LIFETIME_PERSISTENT) {
            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;
        } else {
            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 */