How to use middleware to handle cross-site request forgery (CSRF) in the Slim framework

How to use middleware to handle cross-site request forgery (CSRF) in the Slim framework

Introduction:
Cross-Site Request Forgery (CSRF) is a common Network attack method, the attacker uses the user's authentication information when logged in to a website to force the user to perform malicious requests. To protect applications from CSRF attacks, we can use middleware in Slim framework to handle CSRF issues. This article will introduce how to use middleware in the Slim framework to prevent CSRF attacks, with corresponding code examples.

Step 1: Install the Slim framework
First, we need to install the Slim framework locally. By using Composer, you can easily install the Slim framework and its related dependencies. Execute the following command in the terminal to create a new Slim project:

composer create-project slim/slim my-app

Step 2: Create CSRF middleware
The Slim framework has a built-in middleware (Middleware) mechanism, we can create a middleware to handle CSRF. In the root directory of the project, create a new directory middlewares, and create a file named CsrfMiddleware.php in that directory. The code example is as follows:

<?php
namespace AppMiddlewares;

class CsrfMiddleware extends SlimMiddlewareAntiCsrf
{
    public function call()
    {
        $this->app->hook('slim.before', [$this, 'check']);
        $this->next->call();
    }

    public function validateStorage()
    {
        if (!$this->app->view()->getData('csrf_key') ||
            !$this->app->view()->getData('csrf_value')) {
            $this->app->getLog()->error('CSRF validation error: missing CSRF key and/or value');
            $this->app->pass();
        }
    }
}

Step 3: Register CSRF middleware
Register the created middleware in Slim's application settings. Open the index.php file in the root directory of the project and add the following code to the application settings:

$app = new SlimApp();
...
$app->add(new AppMiddlewaresCsrfMiddleware());
...
$app->run();

Step Four: Add the CSRF token to the form
In In the form that requires CSRF protection, we need to add a CSRF token. This can be achieved by adding a hidden field to the form. The following is a sample code:

<form action="/submit" method="post">
    <input type="hidden" name="csrf_key" value="{{ csrf_key }}">
    <input type="hidden" name="csrf_value" value="{{ csrf_value }}">
    <!-- 其他表单字段 -->
    <button type="submit">提交</button>
</form>

Step five: Check the validity of the CSRF token
On the server side, we need to verify whether the CSRF token in the submitted request is valid. The following is the code for an example route processor function:

$app->post('/submit', function ($request, $response) {
    $data = $request->getParsedBody(); // 获取请求参数

    // 检查CSRF令牌
    $csrf_key = $data['csrf_key'];
    $csrf_value = $data['csrf_value'];
    if (!$app->csrf->check($csrf_key, $csrf_value)) {
        // CSRF令牌验证失败
        $response->getBody()->write('CSRF validation failed');
        return $response->withStatus(403);
    }

    // 处理表单提交
    // ...

    $response->getBody()->write('Form submitted successfully');
    return $response;
});

Summary:
By using the middleware mechanism in the Slim framework, we can easily implement CSRF protection in our applications. Create a CSRF middleware to validate and handle CSRF tokens, then add the CSRF token to the form to secure user requests. The above is the method and code example for handling CSRF in the Slim framework. Hope this article helps you!

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