Merge pull request #3996 from stevew817/feature/allow_reading_external_keys

Allow loading external wrapped keys

library/psa_crypto.c

@@ -2358,6 +2358,15 @@ psa_status_t psa_import_key( const psa_key_attributes_t *attributes,
     }
     else
 #endif /* MBEDTLS_PSA_CRYPTO_SE_C */
+    if( psa_key_lifetime_is_external( psa_get_key_lifetime( attributes ) ) )
+    {
+        /* Importing a key with external lifetime through the driver wrapper
+         * interface is not yet supported. Return as if this was an invalid
+         * lifetime. */
+        status = PSA_ERROR_INVALID_ARGUMENT;
+        goto exit;
+    }
+    else
     {
         status = psa_import_key_into_slot( slot, data, data_length );
         if( status != PSA_SUCCESS )

library/psa_crypto_slot_management.c

@@ -248,7 +248,11 @@ static psa_status_t psa_load_persistent_key_into_slot( psa_key_slot_t *slot )
         goto exit;
 
 #if defined(MBEDTLS_PSA_CRYPTO_SE_C)
-    if( psa_key_lifetime_is_external( slot->attr.lifetime ) )
+    /* 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 ) )
@@ -259,14 +263,13 @@ static psa_status_t psa_load_persistent_key_into_slot( psa_key_slot_t *slot )
         data = (psa_se_key_data_storage_t *) key_data;
         memcpy( &slot->data.se.slot_number, &data->slot_number,
                 sizeof( slot->data.se.slot_number ) );
-    }
-    else
-#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
-    {
-        status = psa_copy_key_material_into_slot( slot, key_data, key_data_length );
-        if( status != PSA_SUCCESS )
+
+        status = PSA_SUCCESS;
         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 );
@@ -343,19 +346,26 @@ psa_status_t psa_validate_key_location( psa_key_lifetime_t lifetime,
     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 )
-            return( PSA_ERROR_INVALID_ARGUMENT );
-        else
+        if( driver != NULL )
         {
             if (p_drv != NULL)
                 *p_drv = driver;
             return( PSA_SUCCESS );
         }
-#else
+#else /* MBEDTLS_PSA_CRYPTO_SE_C */
         (void) p_drv;
-        return( PSA_ERROR_INVALID_ARGUMENT );
 #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 */

library/psa_crypto_storage.c

@@ -374,8 +374,12 @@ psa_status_t psa_save_persistent_key( const psa_core_key_attributes_t *attr,
     uint8_t *storage_data;
     psa_status_t status;
 
+    /* All keys saved to persistent storage always have a key context */
+    if( data == NULL || data_length == 0 )
+        return( PSA_ERROR_INVALID_ARGUMENT );
+
     if( data_length > PSA_CRYPTO_MAX_STORAGE_SIZE )
-        return PSA_ERROR_INSUFFICIENT_STORAGE;
+        return( PSA_ERROR_INSUFFICIENT_STORAGE );
     storage_data_length = data_length + sizeof( psa_persistent_key_storage_format );
 
     storage_data = mbedtls_calloc( 1, storage_data_length );
@@ -426,6 +430,11 @@ psa_status_t psa_load_persistent_key( psa_core_key_attributes_t *attr,
     status = psa_parse_key_data_from_storage( loaded_data, storage_data_length,
                                               data, data_length, attr );
 
+    /* All keys saved to persistent storage always have a key context */
+    if( status == PSA_SUCCESS &&
+        ( *data == NULL || *data_length == 0 ) )
+        status = PSA_ERROR_STORAGE_FAILURE;
+
 exit:
     mbedtls_free( loaded_data );
     return( status );

library/psa_crypto_storage.h

@@ -86,6 +86,9 @@ int psa_is_key_present_in_storage( const mbedtls_svc_key_id_t key );
  * already occupied non-persistent key, as well as ensuring the key data is
  * validated.
  *
+ * Note: This function will only succeed for key buffers which are not
+ * empty. If passed a NULL pointer or zero-length, the function will fail
+ * with #PSA_ERROR_INVALID_ARGUMENT.
  *
  * \param[in] attr          The attributes of the key to save.
  *                          The key identifier field in the attributes
@@ -94,6 +97,7 @@ int psa_is_key_present_in_storage( const mbedtls_svc_key_id_t key );
  * \param data_length       The number of bytes that make up the key data.
  *
  * \retval #PSA_SUCCESS
+ * \retval #PSA_ERROR_INVALID_ARGUMENT
  * \retval #PSA_ERROR_INSUFFICIENT_MEMORY
  * \retval #PSA_ERROR_INSUFFICIENT_STORAGE
  * \retval #PSA_ERROR_STORAGE_FAILURE
@@ -111,9 +115,10 @@ psa_status_t psa_save_persistent_key( const psa_core_key_attributes_t *attr,
  * 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.
+ * the data parameter. On successful return, the pointer is guaranteed to be
+ * valid and the buffer contains at least one byte of data.
+ * psa_free_persistent_key_data() must be called on the data buffer
+ * afterwards to zeroize and free this buffer.
  *
  * \param[in,out] attr      On input, the key identifier field identifies
  *                          the key to load. Other fields are ignored.

tests/suites/test_suite_psa_crypto_slot_management.data

@@ -107,10 +107,15 @@ Open failure: non-existent identifier
 depends_on:MBEDTLS_PSA_CRYPTO_STORAGE_C
 open_fail:1:PSA_ERROR_DOES_NOT_EXIST
 
-Create failure: invalid lifetime
-create_fail:0x7fffffff:0:PSA_ERROR_INVALID_ARGUMENT
+Create failure: invalid lifetime for a persistent key
+depends_on:MBEDTLS_PSA_CRYPTO_STORAGE_C
+create_fail:0x7fffffff:1:PSA_ERROR_INVALID_ARGUMENT
 
-Create failure: invalid key id (0)
+Create failure: invalid lifetime for a volatile key
+depends_on:MBEDTLS_PSA_CRYPTO_STORAGE_C
+create_fail:0x7fffff00:0:PSA_ERROR_INVALID_ARGUMENT
+
+Create failure: invalid key id (0) for a persistent key
 depends_on:MBEDTLS_PSA_CRYPTO_STORAGE_C
 create_fail:PSA_KEY_LIFETIME_PERSISTENT:0:PSA_ERROR_INVALID_HANDLE