Furgas / sodium_compat

Pure PHP polyfill for ext/sodium

Sodium Compat

Sodium Compat is a pure PHP polyfill for the Sodium cryptography library (libsodium), otherwise available in PECL.

This library tentativeley supports PHP 5.2.4 - 7.x (latest), but officially only supports non-EOL'd versions of PHP.

If you have the PHP extension installed, Sodium Compat will opportunistically and transparently use the PHP extension instead of our implementation.

IMPORTANT!

This is an experimental cryptography library. It has not been formally audited by an independent third party that specializes in cryptography or cryptanalysis.

Until it has received a clean bill of health from independent computer security experts, use this library at your own risk.

Installing Sodium Compat

If you're using Composer:

composer require paragonie/sodium_compat

If you're not using Composer, download a release tarball (which should be signed with our GnuPG public key), extract its contents, then include our autoload.php script in your project.

<?php
require_once "/path/to/sodium_compat/autoload.php";

Using Sodium Compat

True Polyfill

If you're using PHP 5.3.0 or newer and do not have the PECL extension installed, you can just use the standard ext/sodium API features as-is and the polyfill will work its magic.

<?php
require_once "/path/to/sodium_compat/autoload.php";

$alice_kp = \Sodium\crypto_sign_keypair();
$alice_sk = \Sodium\crypto_sign_secretkey($alice_kp);
$alice_pk = \Sodium\crypto_sign_publickey($alice_kp);

$message = 'This is a test message.';
$signature = \Sodium\crypto_sign_detached($message, $alice_sk);
if (\Sodium\crypto_sign_verify_detached($signature, $message, $alice_pk)) {
    echo 'OK', PHP_EOL;
} else {
    throw new Exception('Invalid signature');
}

The polyfill does not expose this API on PHP < 5.3, or if you have the PHP extension installed already.

General-Use Polyfill

If your users are on PHP < 5.3, or you want to write code that will work whether or not the PECL extension is available, you'll want to use the ParagonIE_Sodium_Compat class for most of your libsodium needs.

The above example, written for general use:

<?php
require_once "/path/to/sodium_compat/autoload.php";

$alice_kp = ParagonIE_Sodium_Compat::crypto_sign_keypair();
$alice_sk = ParagonIE_Sodium_Compat::crypto_sign_secretkey($alice_kp);
$alice_pk = ParagonIE_Sodium_Compat::crypto_sign_publickey($alice_kp);

$message = 'This is a test message.';
$signature = ParagonIE_Sodium_Compat::crypto_sign_detached($message, $alice_sk);
if (ParagonIE_Sodium_Compat::crypto_sign_verify_detached($signature, $message, $alice_pk)) {
    echo 'OK', PHP_EOL;
} else {
    throw new Exception('Invalid signature');
}

Generally: If you replace \Sodium\ with ParagonIE_Sodium_Compat::, any code already written for the libsodium PHP extension should work with our polyfill without additional code changes.

To learn how to use Libsodium, read Using Libsodium in PHP Projects.

API Coverage

• Mainline NaCl Features
  • crypto_auth()
  • crypto_auth_verify()
  • crypto_box()
  • crypto_box_open()
  • crypto_scalarmult()
  • crypto_secretbox()
  • crypto_secretbox_open()
  • crypto_sign()
  • crypto_sign_open()
• PECL Libsodium Features
  • crypto_box_seal()
  • crypto_box_seal_open()
  • crypto_generichash()
  • crypto_generichash_init()
  • crypto_generichash_update()
  • crypto_generichash_final()
  • crypto_kx()
  • crypto_shorthash()
  • crypto_sign_detached()
  • crypto_sign_verify_detached()
  • For advanced users only:
    • crypto_stream()
    • crypto_stream_xor()
  • Other utilities (e.g. crypto_*_keypair())

Features Excluded from this Polyfill

• \Sodium\memzero() - Although we expose this API endpoint, it's a NOP. We can't reliably zero buffers from PHP.

• \Sodium\crypto_pwhash() - It's not feasible to polyfill scrypt or Argon2 into PHP and get reasonable performance. Users would feel motivated to select parameters that downgrade security to avoid denial of service (DoS) attacks.

  The only winning move is not to play.