.. _hardening:

Hardening Tool
##############

Before launching a product, it's crucial to ensure that your software is as secure as possible. This
process, known as "hardening", involves strengthening the security of a system to protect it from
potential threats and vulnerabilities.

At a high-level, hardening a Zephyr application can be seen as a two-fold process:

#. Disabling features and compilation flags that might lead to security vulnerabilities (ex. making
   sure that no "experimental" features are being used, disabling features typically used for
   debugging purposes such as assertions, shell, etc.).
#. Enabling optional features that can lead to improve security (ex. stack sentinel, hardware stack
   protection, etc.). Some of these features might be hardware-dependent.

To simplify this process, Zephyr offers a **hardening tool** designed to analyze an application's
configuration against a set of hardening preferences defined by the **Security Working Group**. The
tool looks at the KConfig options in the build target and provides tailored suggestions and
recommendations to adjust security-related options.

Usage
*****

.. zephyr-app-commands::
    :tool: all
    :app: samples/hello_world
    :board: reel_board
    :goals: hardenconfig

The output should be similar to the table below. For each configuration option set to a value that
could lead to a security vulnerability, the table will propose a recommended value that should be
used instead.

.. code-block:: console

                  name                       |   current   |  recommended   ||    check result
   ================================================================================================
   CONFIG_BOOT_BANNER                        |      y      |       n        ||       FAIL
   CONFIG_BUILD_OUTPUT_STRIPPED              |      n      |       y        ||       FAIL
   CONFIG_FAULT_DUMP                         |      2      |       0        ||       FAIL
   CONFIG_HW_STACK_PROTECTION                |      n      |       y        ||       FAIL
   CONFIG_MPU_STACK_GUARD                    |      n      |       y        ||       FAIL
   CONFIG_OVERRIDE_FRAME_POINTER_DEFAULT     |      n      |       y        ||       FAIL
   CONFIG_STACK_SENTINEL                     |      n      |       y        ||       FAIL
   CONFIG_EARLY_CONSOLE                      |      y      |       n        ||       FAIL
   CONFIG_PRINTK                             |      y      |       n        ||       FAIL