Ah, the world of computers. Thanks to the wonderful world of bits and bytes, we can experiment with any application, file, driver, or even the core operating system. Rip them apart, change things, put them together, and if it doesn’t work, just try again. At worst, you’ll have to wipe your hard drive and start over. If you somehow manage to destroy a computer purely through bad software, that’s considered a design problem and a true feat to pull off. Just think about it: what other profession or hobby lets you experiment as much as you want and make as many mistakes as you want without having to spend a cent if you do something wrong?
Unfortunately, things have changed. Ever since the advent of embedded devices with upgradable firmware, people have been trying to modify and hack them. These devices are usually a lot less resilient than their bigger, older siblings. Many of the new shiny gadgets that we use every day are internally fragile and a slight software mishap can render them non-functional, a “brick”.
This is a guide for developers and hackers who work on system firmware for embedded devices.
He outlines several key points that are worth thinking about. Among them:
- Care About Your Users:
The first step towards safe hacking is to develop a deep appreciation towards your users and, especially, their hardware. Most users are clueless and entirely dependent on you to guide them towards a safe result.
- Understand the System
Before you start working on software that makes permanent changes to a device, you should have a deep enough understanding of its operation. Reverse engineer the boot process. Understand what parts of the firmware depend on what. Know what components are vital for boot, and what recovery modes are available, if any.
- Fail Intelligently
If a critical operation fails, the worst possible thing you can do is panic the application or otherwise halt! Then you’re guaranteed to brick the device. Instead, drop the user into some kind of failsafe mode, shell, or launcher, and direct them to keep the device powered on and seek immediate attention (e.g. on an IRC channel).
- Protect Users from Themselves
Users will do completely stupid things. It’s not just that they will click on things without understanding what the outcome will be; if you include a big red button that says “Brick Me!”, someone will click it too. That’s why you should at least make it hard for users to destroy their system.
Ideally, you’ve put enough effort into making sure your application is safe. However, the unexpected can and does happen, and sometimes you will not have the resources to perform a comprehensive enough test. So gather up a few people that you can trust and who are willing to risk it, and perform a closed test. Do not release a public beta! People are way too impatient, and public betas are essentially synonymous with a release; people will ignore any warnings attached.
Excellent advice from a guy who knows what’s up.