Mbed OS Reference | psa_crypto_storage.h Source File

Go to the documentation of this file.
 /**
  * \file psa_crypto_storage.h
  *
  * \brief PSA cryptography module: Mbed TLS key storage
  */
 /*
  *  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.
  */
 
 #ifndef PSA_CRYPTO_STORAGE_H
 #define PSA_CRYPTO_STORAGE_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #include "psa/crypto.h"
 #include "psa/crypto_se_driver.h"
 
 #include <stdint.h>
 #include <string.h>
 
 /* Limit the maximum key size in storage. This should have no effect
  * since the key size is limited in memory. */
 #define PSA_CRYPTO_MAX_STORAGE_SIZE ( PSA_BITS_TO_BYTES( PSA_MAX_KEY_BITS ) )
 /* Sanity check: a file size must fit in 32 bits. Allow a generous
  * 64kB of metadata. */
 #if PSA_CRYPTO_MAX_STORAGE_SIZE > 0xffff0000
 #error PSA_CRYPTO_MAX_STORAGE_SIZE > 0xffff0000
 #endif
 
 /** The maximum permitted persistent slot number.
  *
  * In Mbed Crypto 0.1.0b:
  * - Using the file backend, all key ids are ok except 0.
  * - Using the ITS backend, all key ids are ok except 0xFFFFFF52
  *   (#PSA_CRYPTO_ITS_RANDOM_SEED_UID) for which the file contains the
  *   device's random seed (if this feature is enabled).
  * - Only key ids from 1 to #PSA_KEY_SLOT_COUNT are actually used.
  *
  * Since we need to preserve the random seed, avoid using that key slot.
  * Reserve a whole range of key slots just in case something else comes up.
  *
  * This limitation will probably become moot when we implement client
  * separation for key storage.
  */
 #define PSA_MAX_PERSISTENT_KEY_IDENTIFIER PSA_KEY_ID_VENDOR_MAX
 
 /**
  * \brief Checks if persistent data is stored for the given key slot number
  *
  * This function checks if any key data or metadata exists for the key slot in
  * the persistent storage.
  *
  * \param key           Persistent identifier to check.
  *
  * \retval 0
  *         No persistent data present for slot number
  * \retval 1
  *         Persistent data present for slot number
  */
 int psa_is_key_present_in_storage( const psa_key_file_id_t key );
 
 /**
  * \brief Format key data and metadata and save to a location for given key
  *        slot.
  *
  * This function formats the key data and metadata and saves it to a
  * persistent storage backend. The storage location corresponding to the
  * key slot must be empty, otherwise this function will fail. This function
  * should be called after psa_import_key_into_slot() to ensure the
  * persistent key is not saved into a storage location corresponding to an
  * already occupied non-persistent key, as well as validating the key data.
  *
  *
  * \param[in] attr          The attributes of the key to save.
  *                          The key identifier field in the attributes
  *                          determines the key's location.
  * \param[in] data          Buffer containing the key data.
  * \param data_length       The number of bytes that make up the key data.
  *
  * \retval PSA_SUCCESS
  * \retval PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval PSA_ERROR_INSUFFICIENT_STORAGE
  * \retval PSA_ERROR_STORAGE_FAILURE
  * \retval PSA_ERROR_ALREADY_EXISTS
  */
 psa_status_t psa_save_persistent_key( const psa_core_key_attributes_t *attr,
                                       const uint8_t *data,
                                       const size_t data_length );
 
 /**
  * \brief Parses key data and metadata and load persistent key for given
  * key slot number.
  *
  * This function reads from a storage backend, parses the key data and
  * metadata and writes them to the appropriate output parameters.
  *
  * Note: This function allocates a buffer and returns a pointer to it through
  * the data parameter. psa_free_persistent_key_data() must be called after
  * this function to zeroize and free this buffer, regardless of whether this
  * function succeeds or fails.
  *
  * \param[in,out] attr      On input, the key identifier field identifies
  *                          the key to load. Other fields are ignored.
  *                          On success, the attribute structure contains
  *                          the key metadata that was loaded from storage.
  * \param[out] data         Pointer to an allocated key data buffer on return.
  * \param[out] data_length  The number of bytes that make up the key data.
  *
  * \retval PSA_SUCCESS
  * \retval PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval PSA_ERROR_STORAGE_FAILURE
  * \retval PSA_ERROR_DOES_NOT_EXIST
  */
 psa_status_t psa_load_persistent_key( psa_core_key_attributes_t *attr,
                                       uint8_t **data,
                                       size_t *data_length );
 
 /**
  * \brief Remove persistent data for the given key slot number.
  *
  * \param key           Persistent identifier of the key to remove
  *                      from persistent storage.
  *
  * \retval PSA_SUCCESS
  *         The key was successfully removed,
  *         or the key did not exist.
  * \retval PSA_ERROR_STORAGE_FAILURE
  */
 psa_status_t psa_destroy_persistent_key( const psa_key_file_id_t key );
 
 /**
  * \brief Free the temporary buffer allocated by psa_load_persistent_key().
  *
  * This function must be called at some point after psa_load_persistent_key()
  * to zeroize and free the memory allocated to the buffer in that function.
  *
  * \param key_data        Buffer for the key data.
  * \param key_data_length Size of the key data buffer.
  *
  */
 void psa_free_persistent_key_data( uint8_t *key_data, size_t key_data_length );
 
 /**
  * \brief Formats key data and metadata for persistent storage
  *
  * \param[in] data          Buffer containing the key data.
  * \param data_length       Length of the key data buffer.
  * \param[in] attr          The core attributes of the key.
  * \param[out] storage_data Output buffer for the formatted data.
  *
  */
 void psa_format_key_data_for_storage( const uint8_t *data,
                                       const size_t data_length,
                                       const psa_core_key_attributes_t *attr,
                                       uint8_t *storage_data );
 
 /**
  * \brief Parses persistent storage data into key data and metadata
  *
  * \param[in] storage_data     Buffer for the storage data.
  * \param storage_data_length  Length of the storage data buffer
  * \param[out] key_data        On output, pointer to a newly allocated buffer
  *                             containing the key data. This must be freed
  *                             using psa_free_persistent_key_data()
  * \param[out] key_data_length Length of the key data buffer
  * \param[out] attr            On success, the attribute structure is filled
  *                             with the loaded key metadata.
  *
  * \retval PSA_SUCCESS
  * \retval PSA_ERROR_INSUFFICIENT_STORAGE
  * \retval PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval PSA_ERROR_STORAGE_FAILURE
  */
 psa_status_t psa_parse_key_data_from_storage( const uint8_t *storage_data,
                                               size_t storage_data_length,
                                               uint8_t **key_data,
                                               size_t *key_data_length,
                                               psa_core_key_attributes_t *attr );
 
 #if defined(MBEDTLS_PSA_CRYPTO_SE_C)
 /** This symbol is defined if transaction support is required. */
 #define PSA_CRYPTO_STORAGE_HAS_TRANSACTIONS
 #endif
 
 #if defined(PSA_CRYPTO_STORAGE_HAS_TRANSACTIONS)
 
 /** The type of transaction that is in progress.
  */
 /* This is an integer type rather than an enum for two reasons: to support
  * unknown values when loading a transaction file, and to ensure that the
  * type has a known size.
  */
 typedef uint16_t psa_crypto_transaction_type_t;
 
 /** No transaction is in progress.
  *
  * This has the value 0, so zero-initialization sets a transaction's type to
  * this value.
  */
 #define PSA_CRYPTO_TRANSACTION_NONE             ( (psa_crypto_transaction_type_t) 0x0000 )
 
 /** A key creation transaction.
  *
  * This is only used for keys in an external cryptoprocessor (secure element).
  * Keys in RAM or in internal storage are created atomically in storage
  * (simple file creation), so they do not need a transaction mechanism.
  */
 #define PSA_CRYPTO_TRANSACTION_CREATE_KEY       ( (psa_crypto_transaction_type_t) 0x0001 )
 
 /** A key destruction transaction.
  *
  * This is only used for keys in an external cryptoprocessor (secure element).
  * Keys in RAM or in internal storage are destroyed atomically in storage
  * (simple file deletion), so they do not need a transaction mechanism.
  */
 #define PSA_CRYPTO_TRANSACTION_DESTROY_KEY      ( (psa_crypto_transaction_type_t) 0x0002 )
 
 /** Transaction data.
  *
  * This type is designed to be serialized by writing the memory representation
  * and reading it back on the same device.
  *
  * \note The transaction mechanism is designed for a single active transaction
  *       at a time. The transaction object is #psa_crypto_transaction.
  *
  * \note If an API call starts a transaction, it must complete this transaction
  *       before returning to the application.
  *
  * The lifetime of a transaction is the following (note that only one
  * transaction may be active at a time):
  *
  * -# Call psa_crypto_prepare_transaction() to initialize the transaction
  *    object in memory and declare the type of transaction that is starting.
  * -# Fill in the type-specific fields of #psa_crypto_transaction.
  * -# Call psa_crypto_save_transaction() to start the transaction. This
  *    saves the transaction data to internal storage.
  * -# Perform the work of the transaction by modifying files, contacting
  *    external entities, or whatever needs doing. Note that the transaction
  *    may be interrupted by a power failure, so you need to have a way
  *    recover from interruptions either by undoing what has been done
  *    so far or by resuming where you left off.
  * -# If there are intermediate stages in the transaction, update
  *    the fields of #psa_crypto_transaction and call
  *    psa_crypto_save_transaction() again when each stage is reached.
  * -# When the transaction is over, call psa_crypto_stop_transaction() to
  *    remove the transaction data in storage and in memory.
  *
  * If the system crashes while a transaction is in progress, psa_crypto_init()
  * calls psa_crypto_load_transaction() and takes care of completing or
  * rewinding the transaction. This is done in psa_crypto_recover_transaction()
  * in psa_crypto.c. If you add a new type of transaction, be
  * sure to add code for it in psa_crypto_recover_transaction().
  */
 typedef union
 {
     /* Each element of this union must have the following properties
      * to facilitate serialization and deserialization:
      *
      * - The element is a struct.
      * - The first field of the struct is `psa_crypto_transaction_type_t type`.
      * - Elements of the struct are arranged such a way that there is
      *   no padding.
      */
     struct psa_crypto_transaction_unknown_s
     {
         psa_crypto_transaction_type_t type;
         uint16_t unused1;
         uint32_t unused2;
         uint64_t unused3;
         uint64_t unused4;
     } unknown;
     /* ::type is #PSA_CRYPTO_TRANSACTION_CREATE_KEY or
      * #PSA_CRYPTO_TRANSACTION_DESTROY_KEY. */
     struct psa_crypto_transaction_key_s
     {
         psa_crypto_transaction_type_t type;
         uint16_t unused1;
         psa_key_lifetime_t lifetime;
         psa_key_slot_number_t slot;
         psa_key_id_t id;
     } key;
 } psa_crypto_transaction_t;
 
 /** The single active transaction.
  */
 extern psa_crypto_transaction_t psa_crypto_transaction;
 
 /** Prepare for a transaction.
  *
  * There must not be an ongoing transaction.
  *
  * \param type          The type of transaction to start.
  */
 static inline void psa_crypto_prepare_transaction(
     psa_crypto_transaction_type_t type )
 {
     psa_crypto_transaction.unknown.type = type;
 }
 
 /** Save the transaction data to storage.
  *
  * You may call this function multiple times during a transaction to
  * atomically update the transaction state.
  *
  * \retval #PSA_SUCCESS
  * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
  * \retval #PSA_ERROR_STORAGE_FAILURE
  */
 psa_status_t psa_crypto_save_transaction( void );
 
 /** Load the transaction data from storage, if any.
  *
  * This function is meant to be called from psa_crypto_init() to recover
  * in case a transaction was interrupted by a system crash.
  *
  * \retval #PSA_SUCCESS
  *         The data about the ongoing transaction has been loaded to
  *         #psa_crypto_transaction.
  * \retval #PSA_ERROR_DOES_NOT_EXIST
  *         There is no ongoing transaction.
  * \retval #PSA_ERROR_STORAGE_FAILURE
  */
 psa_status_t psa_crypto_load_transaction( void );
 
 /** Indicate that the current transaction is finished.
  *
  * Call this function at the very end of transaction processing.
  * This function does not "commit" or "abort" the transaction: the storage
  * subsystem has no concept of "commit" and "abort", just saving and
  * removing the transaction information in storage.
  *
  * This function erases the transaction data in storage (if any) and
  * resets the transaction data in memory.
  *
  * \retval #PSA_SUCCESS
  *         There was transaction data in storage.
  * \retval #PSA_ERROR_DOES_NOT_EXIST
  *         There was no transaction data in storage.
  * \retval #PSA_ERROR_STORAGE_FAILURE
  *         It was impossible to determine whether there was transaction data
  *         in storage, or the transaction data could not be erased.
  */
 psa_status_t psa_crypto_stop_transaction( void );
 
 /** The ITS file identifier for the transaction data.
  *
  * 0xffffffNN = special file; 0x74 = 't' for transaction.
  */
 #define PSA_CRYPTO_ITS_TRANSACTION_UID ( (psa_key_id_t) 0xffffff74 )
 
 #endif /* PSA_CRYPTO_STORAGE_HAS_TRANSACTIONS */
 
 #if defined(MBEDTLS_PSA_INJECT_ENTROPY)
 /** Backend side of mbedtls_psa_inject_entropy().
  *
  * This function stores the supplied data into the entropy seed file.
  *
  * \retval #PSA_SUCCESS
  *         Success
  * \retval #PSA_ERROR_STORAGE_FAILURE
  * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
  * \retval #PSA_ERROR_NOT_PERMITTED
  *         The entropy seed file already exists.
  */
 psa_status_t mbedtls_psa_storage_inject_entropy( const unsigned char *seed,
                                                  size_t seed_size );
 #endif /* MBEDTLS_PSA_INJECT_ENTROPY */
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif /* PSA_CRYPTO_STORAGE_H */
Important Information for this Arm website
