Release: sodium_compat v2 and the Future of Our Polyfill Libraries
April 19, 2024 by P.I.E. Staff
Several years ago, we designed sodium_compat: a pure-PHP implementation of (most of) libsodium. It has since been installed over 60 million times, not counting WordPress.
Our goals with sodium_compat were as follows:
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Ensure ease-of-adoption for ext-sodium. By providing a permissively licensed open source PHP library that implements the same algorithms, other open source projects could move faster to libsodium proper, even if their users were on shared hosting environments where they couldn't install PHP extensions from PECL.
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Get adopted by software that supported old versions of PHP. Specifically, 5.2.4, which WordPress still supported at the time. Due to WordPress's enormous footprint on the Internet, this was not a lightly taken decision.
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Work even on 32-bit platforms. It turns out, PHP gives you signed 32-bit integers on 32-bit platforms (or on Windows before PHP 7), and if you reach a value out of the range of those integers, your numbers are "conveniently" converted to a float instead. This is a nightmare when you're implementing cryptography.
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Get out of your way. If you install ext-sodium, our APIs will defer all cryptography to the proper implementation. This was a core tenet of sodium_compat's design.
To repeat ourselves a bit, this was several years ago. The PHP community has evolved. WordPress now requires PHP 7.0 to function (although they do recommend 7.4). As of this writing, the oldest still-supported version of PHP is 8.2 (8.1 if you count "security fixes only"). We asked ourselves, and the /r/PHP subreddit, if anyone still even needs PHP 5 support in 2024.
The answer was a resounding, "No."
That's the background story, anyway. If you're a busy developer, the remainder of this post will be broken down into a Q&A format to explain what's changing, what's not changing, what you need to do, and whether you need to do anything.
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