Paragon Initiative Enterprises Blog

The latest information from the team that develops cryptographically secure PHP software.

The Quick Guide to Simple and Secure Automatic Updates

Should your software update itself automatically? YES!

If you aren't convinced, we've previously made the case for automatic software updates as a means of preventing yesterday's software vulnerabilities from being exploited today.

However, as our previous article on the subject notes, implementing automatic software updates requires a nontrivial amount of engineering effort in order to be secure.

Our company has been hard at work for the past few years to diminish the effort required to achieve secure automatic software updates in the PHP community. Most of our efforts are reproducible and/or relevant to any other programming stack, although PHP remains the first major programming language to decide to adopt modern cryptography in its standard library.

Let's explore how to use our existing work to build a secure automatic software update system, without having to do any of the heavy lifting.

Simple and Secure Automatic Software Updates

How to Implement Secure Automatic Updates, the Easy Way

First, make sure your deliverables are reproducible from the source code. If you're working with scripting languages that are never compiled into binary code, this merely requires your software be open source.

Second, use an update framework (i.e The Update Framework) that enforces code signing. This means that your update files must be signed by a private key controlled only by you, but can be verified by anyone with your public key.

If you don't understand what "private key" or "public key" means, this page is an approachable introduction to cryptography terms and concepts and will shed some light on the matter.

Finally, run a Chronicle instance. Every time you release an update, publish the new release information to your Chronicle. Make your code that interfaces with The Update Framework verify that the release you're seeing is also published in the Chronicle (or, especially for enterprise customers, their own replica of your Chronicle that resides on the corporate network).

That's it. The Update Framework (or a similar implementation relevant to your stack) and Chronicle are all you need (as far as tooling goes). Make your software open source, and your builds reproducible, and you'll drastically reduce your customer's attack surface in terms of both space and time.

Secure Automatic Software Updates in PHP

There isn't currently a PHP implementation of The Update Framework. If there's enough community interest, we may commit to building one in the future. However, that might not be necessary.

If you're developing modern PHP, you're almost certainly using Composer and Packagist. If not, it's highly recommended that you learn it ASAP.

Earlier this year, I opened a proposal to the Packagist team to run their own Chronicle instance, which would be used to publish information about software releases in real time. We're working on other proposals to enforce signature validation and solve the Public Key Infrastructure (PKI) problems.

In other words: If you're using Composer, then in the near future this may already be a solved problem for you.

If you cannot wait for our work to be accepted and deployed in Composer, you'll have to either roll your own implementation or hire Paragon Initiative Enterprises to build it for you. We've previously implemented secure automatic updates in two different products (one of them is Free Software). Refer to the implementation in CMS Airship if you need a starting point.

If your users won't have the Sodium extension available, look into sodium_compat. This probably won't be a problem once everyone is running PHP 7.2 and newer.

Secure Automatic Updates for Embedded Devices and the Internet of Things (IoT)

Embedded development faces unique challenges and there hasn't been a lot of guidance on implementing secure automatic update protocols, especially for so-called "smart devices". Due to low memory or power usage requirements, it's often not feasible to just staple cryptography onto your product design without using up your entire power or memory budget.

For extremely constrained devices, libhydrogen is an attractive option. It's very lightweight, and the current implementation uses only two primitives to provide a full-featured cryptography library: the Gimli permutation and Curve25519.

Commercial support for libhydrogen is available from Primulinus.

The protocol designs that went into The Update Framework and Chronicle can be easily re-implemented using libhydrogen, but the Hydrogen version will not be compatible with the Sodium version. If a Hydrogen variant of Chronicle is desired, get in touch with our team.

About the Author

Scott Arciszewski

Chief Development Officer

With 15 years of software development, application security, and system administration experience, Scott aspires to help others attain a happier work-life balance by solving difficult problems and automating trivial tasks. He is mostly known in the community for his open source software security research and strong progressive positions on providing tools and frameworks that are secure by default. @CiPHPerCoder

Need Technology Consultants?

Will tomorrow bring costly and embarrassing data breaches? Or will it bring growth, success, and peace of mind?

Our team of technology consultants have extensive knowledge and experience with application security and web/application development.

We specialize in cryptography and secure PHP development.

Let's Work Together Towards Success

Our Security Newsletters

Want the latest from Paragon Initiative Enterprises delivered straight to your inbox? We have two newsletters to choose from.

The first mails quarterly and often showcases our behind-the-scenes projects.

The other is unscheduled and gives you a direct feed into the findings of our open source security research initiatives.

Quarterly Newsletter   Security Announcements