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<?php
/**
* webtrees: online genealogy
* Copyright (C) 2026 webtrees development team
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
declare(strict_types=1);
namespace Fisharebest\Webtrees\Services;
use Fisharebest\Webtrees\Registry;
use Fisharebest\Webtrees\Session;
use Fisharebest\Webtrees\Validator;
use Psr\Http\Message\ServerRequestInterface;
use function assert;
use function is_float;
use function is_string;
use function view;
/**
* Completely Automated Public Turing test to tell Computers and Humans Apart.
*/
class CaptchaService
{
// If the form is completed faster than this, then suspect a robot.
private const float MINIMUM_FORM_TIME = 3.0;
/**
* Create the captcha
*
* @return string
*/
public function createCaptcha(): string
{
$x = Registry::idFactory()->uuid();
$y = Registry::idFactory()->uuid();
$z = Registry::idFactory()->uuid();
Session::put('captcha-t', Registry::timeFactory()->now());
Session::put('captcha-x', $x);
Session::put('captcha-y', $y);
Session::put('captcha-z', $z);
return view('captcha', [
'x' => $x,
'y' => $y,
'z' => $z,
]);
}
/**
* Check the user's response.
*
* @param ServerRequestInterface $request
*
* @return bool
*/
public function isRobot(ServerRequestInterface $request): bool
{
$t = Session::pull('captcha-t');
$x = Session::pull('captcha-x');
$y = Session::pull('captcha-y');
$z = Session::pull('captcha-z');
// No session variables? Maybe the visitor POSTed directly, without first visiting the paged.
if (!is_float($t) || !is_string($x) || !is_string($y) || !is_string($z)) {
return true;
}
$value_x = Validator::parsedBody($request)->string($x, '');
$value_y = Validator::parsedBody($request)->string($y, '');
// The captcha uses JavaScript to copy value z from field y to field x.
// Expect it in both fields.
if ($value_x !== $z || $value_y !== $z) {
return true;
}
// If the form was returned too quickly, then probably a robot.
return Registry::timeFactory()->now() < $t + self::MINIMUM_FORM_TIME;
}
}
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