How do I implement CSRF protection with Slim 4 and slim/csrf?

Question

Slim 4 is already here and I am trying to move to Slim 4. Everything is great, but CSRF returns an error when i try to implement it. I tried the simplest setup, but I get this error:

Message: Argument 2 passed to Slim\Csrf\Guard::__invoke() must be an instance of Psr\Http\Message\ResponseInterface, instance of Slim\Routing\RouteRunner given, called in /Volumes/Web/slim/vendor/slim/slim/Slim/MiddlewareDispatcher.php on line 180

File: /Volumes/Web/slim/vendor/slim/csrf/src/Guard.php

Here is my code:

<?php
use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
use Slim\Factory\AppFactory;
use Slim\Csrf\Guard;

require __DIR__ . '/../vendor/autoload.php';

/**
 * Instantiate App
 *
 * In order for the factory to work you need to ensure you have installed
 * a supported PSR-7 implementation of your choice e.g.: Slim PSR-7 and a supported
 * ServerRequest creator (included with Slim PSR-7)
 */
$app = AppFactory::create();

$app->add(Guard::class);

// Add Routing Middleware
$app->addRoutingMiddleware();

/*
 * Add Error Handling Middleware
 *
 * @param bool $displayErrorDetails -> Should be set to false in production
 * @param bool $logErrors -> Parameter is passed to the default ErrorHandler
 * @param bool $logErrorDetails -> Display error details in error log
 * which can be replaced by a callable of your choice.

 * Note: This middleware should be added last. It will not handle any exceptions/errors
 * for middleware added after it.
 */
$errorMiddleware = $app->addErrorMiddleware(true, true, true);

// Define app routes
$app->get('/', function (Request $request, Response $response, $args) {
    $response->getBody()->write('Hello');
    return $response;
});

// Run app
$app->run();

Any help is greatly appreciated! Thanks!

looks like you're trying to implement a [CSRF Token](https://stackoverflow.com/a/33829607/1067003) rather than execute a [CSRF attack](https://en.wikipedia.org/wiki/Cross-site_request_forgery), but your question title implies that you're trying to execute a csrf attack rather than implement a token — hanshenrik, Aug 27 '19 at 18:32

Gideon Visbeen · Accepted Answer · 2019-08-30T19:52:46.797

The package is not compatible with Slim4. I wrote a wrapper so you can use it.

`

<?php

declare(strict_types=1);

namespace App\Application\Middleware;

use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
use Psr\Http\Server\MiddlewareInterface as Middleware;
use Psr\Http\Server\RequestHandlerInterface as RequestHandler;
use Slim\Csrf\Guard as Guard;

class CsrfMiddleware extends Guard implements Middleware
{

    /**
     * Process middleware
     *
     * @param  ServerRequestInterface  $request  request object
     * @param  RequestHandlerInterface $handler handler object
     *
     * @return ResponseInterface response object
     */
    public function process(Request $request, RequestHandler $handler): Response
    {
        $this->validateStorage();
        // Validate POST, PUT, DELETE, PATCH requests
        if (in_array($request->getMethod(), ['POST', 'PUT', 'DELETE', 'PATCH'])) {
            $body = $request->getParsedBody();
            $body = $body ? (array) $body : [];
            $name = isset($body[$this->prefix . '_name']) ? $body[$this->prefix . '_name'] : false;
            $value = isset($body[$this->prefix . '_value']) ? $body[$this->prefix . '_value'] : false;
            if (!$name || !$value || !$this->validateToken($name, $value)) {
                // Need to regenerate a new token, as the validateToken removed the current one.
                $request = $this->generateNewToken($request);

                $failureCallable = $this->getFailureCallable();
                return $failureCallable($request, $handler);
            }
        }
        // Generate new CSRF token if persistentTokenMode is false, or if a valid keyPair has not yet been stored
        if (!$this->persistentTokenMode || !$this->loadLastKeyPair()) {
            $request = $this->generateNewToken($request);
        } elseif ($this->persistentTokenMode) {
            $pair = $this->loadLastKeyPair() ? $this->keyPair : $this->generateToken();
            $request = $this->attachRequestAttributes($request, $pair);
        }
        // Enforce the storage limit
        $this->enforceStorageLimit();

        return $handler->handle($request);
    }

    /**
     * Getter for failureCallable
     *
     * @return callable|\Closure
     */
    public function getFailureCallable()
    {
        if (is_null($this->failureCallable)) {
            $this->failureCallable = function (Request $request, RequestHandler $handler): Response {
                $response = $handler->handle($request);
                $stream = $response->getBody();
                $stream->write('CSRF fail');
                return $response->withStatus(400);
            };
        }
        return $this->failureCallable;
    }
}

`

Álvaro González · Answer 2 · 2019-08-29T14:48:21.693

The relevant bit is:

$app->add(Guard::class);

The signature of middleware callbacks has changed. In Slim/3 it used to be like this:

public function __invoke(
    ServerRequestInterface $request,
    ResponseInterface $response,
    callable $next
): ResponseInterface

... and then the method had to call $next like $next($request, $response).

In Slim/4 it's like this:

public function __invoke(
    ServerRequestInterface $request,
    RequestHandlerInterface $handler
): ResponseInterface

.. and the internal call to $handler is $handler->handle($request).

The library does not seem to have been updated for Slim/4. It declares Slim/3 as dev (?) dependency in composer.json and mentions in README.md. Perhaps it isn't very difficult to either fix the library or write a compatible wrapper on top of it but if you aren't familiar with the overall ecosystem it's probably easier to install a replacement.

Thanks for the reply @Alvaro Gonzalez! I am using Composer to install all packages. Should that make it compatible with Slim 4? — AlexBet, Aug 28 '19 at 18:20
Sorry, I overlooked that `slim/slim` is being declared as **development** dependency. Nothing prevents you from installing it in an incompatible Slim version. BTW, check [user3294859's answer](https://stackoverflow.com/a/57709892/13508), he just wrote a wrapper! — Álvaro González, Aug 29 '19 at 14:44

How do I implement CSRF protection with Slim 4 and slim/csrf?

2 Answers2