Hmac.php

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<?php
namespace Elgg\Security;
 
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, $this->key, true);
        return strtr(rtrim(base64_encode($bytes), '='), '+/', '-_');
    }
 
    public function matchesToken($token) {
        $expected_token = $this->getToken();
        return call_user_func($this->comparator, $expected_token, $token);
    }
}