Hmac.php

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<?php

namespace Elgg\Security;

use Elgg\Exceptions\InvalidArgumentException;

class Hmac {

    private $key;

    private $comparator;

    private $data;

    private $algo;

    public function __construct($key, callable $comparator, $data, $algo = 'sha256') {
        $this->key = $key;
        $this->comparator = $comparator;
        if (!$data) {
            throw new InvalidArgumentException('$data cannot be empty');
        }
        
        if (!is_string($data)) {
            $data = serialize($data);
        }
        
        $this->data = $data;
        $this->algo = $algo;
    }

    public function getToken() {
        $bytes = hash_hmac($this->algo, $this->data, $this->key, true);
        return Base64Url::encode($bytes);
    }

    public function matchesToken($token) {
        $expected_token = $this->getToken();
        return call_user_func($this->comparator, $expected_token, $token);
    }
}