KeyRotationObjective.php

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<?php
 
declare(strict_types=1);
 
namespace ILIAS\FileDelivery\Setup;
 
use ILIAS\Setup\Artifact;
use ILIAS\Setup\Artifact\ArrayArtifact;
 
class KeyRotationObjective extends BuildStaticConfigStoredObjective
{
    private const int KEY_LENGTH = 32;
    private const int NUMBER_OF_KEYS = 5;
 
    public function getArtifactName(): string
    {
        return "key_rotation";
    }
 
    public function build(): Artifact
    {
        $current_keys = [];
        if (is_readable(self::PATH())) {
            $current_keys = require self::PATH();
        }
 
        $new_keys = [];
        // push one new key to the beginning, drop the oldest key until we have 5 keys
        for ($i = 0; $i < self::NUMBER_OF_KEYS - 1; $i++) {
            if ($i === 0) {
                $new_keys[] = $this->generateRandomString(self::KEY_LENGTH);
            }
            $new_keys[] = $current_keys[$i] ?? $this->generateRandomString(self::KEY_LENGTH);
        }
 
        return new ArrayArtifact($new_keys);
    }
 
    private function generateRandomString(int $length): string
    {
        $return = '';
        for ($i = 0; $i < $length; $i++) {
            $return .= chr(random_int(33, 125));
        }
        return $return;
    }
}