Security

Security is a big deal when it comes to web applications. You want to make sure that your application is secure and that your users' data is safe. Flight provides a number of features to help you secure your web applications.

Headers

HTTP headers are one of the easiest ways to secure your web applications. You can use headers to prevent clickjacking, XSS, and other attacks. There are several ways that you can add these headers to your application.

Two great websites to check for the security of your headers are securityheaders.com and observatory.mozilla.org.

Add By Hand

You can manually add these headers by using the header method on the Flight\Response object.

// Set the X-Frame-Options header to prevent clickjacking
Flight::response()->header('X-Frame-Options', 'SAMEORIGIN');

// Set the Content-Security-Policy header to prevent XSS
// Note: this header can get very complex, so you'll want
//  to consult examples on the internet for your application
Flight::response()->header("Content-Security-Policy", "default-src 'self'");

// Set the X-XSS-Protection header to prevent XSS
Flight::response()->header('X-XSS-Protection', '1; mode=block');

// Set the X-Content-Type-Options header to prevent MIME sniffing
Flight::response()->header('X-Content-Type-Options', 'nosniff');

// Set the Referrer-Policy header to control how much referrer information is sent
Flight::response()->header('Referrer-Policy', 'no-referrer-when-downgrade');

// Set the Strict-Transport-Security header to force HTTPS
Flight::response()->header('Strict-Transport-Security', 'max-age=31536000; includeSubDomains; preload');

// Set the Permissions-Policy header to control what features and APIs can be used
Flight::response()->header('Permissions-Policy', 'geolocation=()');

These can be added at the top of your bootstrap.php or index.php files.

Add as a Filter

You can also add them in a filter/hook like the following:

// Add the headers in a filter
Flight::before('start', function() {
    Flight::response()->header('X-Frame-Options', 'SAMEORIGIN');
    Flight::response()->header("Content-Security-Policy", "default-src 'self'");
    Flight::response()->header('X-XSS-Protection', '1; mode=block');
    Flight::response()->header('X-Content-Type-Options', 'nosniff');
    Flight::response()->header('Referrer-Policy', 'no-referrer-when-downgrade');
    Flight::response()->header('Strict-Transport-Security', 'max-age=31536000; includeSubDomains; preload');
    Flight::response()->header('Permissions-Policy', 'geolocation=()');
});

Add as a Middleware

You can also add them as a middleware class. This is a good way to keep your code clean and organized.

// app/middleware/SecurityHeadersMiddleware.php

namespace app\middleware;

class SecurityHeadersMiddleware
{
    public function before(array $params): void
    {
        Flight::response()->header('X-Frame-Options', 'SAMEORIGIN');
        Flight::response()->header("Content-Security-Policy", "default-src 'self'");
        Flight::response()->header('X-XSS-Protection', '1; mode=block');
        Flight::response()->header('X-Content-Type-Options', 'nosniff');
        Flight::response()->header('Referrer-Policy', 'no-referrer-when-downgrade');
        Flight::response()->header('Strict-Transport-Security', 'max-age=31536000; includeSubDomains; preload');
        Flight::response()->header('Permissions-Policy', 'geolocation=()');
    }
}

// index.php or wherever you have your routes
// FYI, this empty string group acts as a global middleware for
// all routes. Of course you could do the same thing and just add
// this only to specific routes.
Flight::group('', function(Router $router) {
    $router->get('/users', [ 'UserController', 'getUsers' ]);
    // more routes
}, [ new SecurityHeadersMiddleware() ]);

Cross Site Request Forgery (CSRF)

Cross Site Request Forgery (CSRF) is a type of attack where a malicious website can make a user's browser send a request to your website. This can be used to perform actions on your website without the user's knowledge. Flight does not provide a built-in CSRF protection mechanism, but you can easily implement your own by using middleware.

Setup

First you need to generate a CSRF token and store it in the user's session. You can then use this token in your forms and check it when the form is submitted.

// Generate a CSRF token and store it in the user's session
// (assuming you've created a session object at attached it to Flight)
// You only need to generate a single token per session (so it works 
// across multiple tabs and requests for the same user)
if(Flight::session()->get('csrf_token') === null) {
    Flight::session()->set('csrf_token', bin2hex(random_bytes(32)) );
}

<!-- Use the CSRF token in your form -->
<form method="post">
    <input type="hidden" name="csrf_token" value="<?= Flight::session()->get('csrf_token') ?>">
    <!-- other form fields -->
</form>

Using Latte

You can also set a custom function to output the CSRF token in your Latte templates.

// Set a custom function to output the CSRF token
// Note: View has been configured with Latte as the view engine
Flight::view()->addFunction('csrf', function() {
    $csrfToken = Flight::session()->get('csrf_token');
    return new \Latte\Runtime\Html('<input type="hidden" name="csrf_token" value="' . $csrfToken . '">');
});

And now in your Latte templates you can use the csrf() function to output the CSRF token.

<form method="post">
    {csrf()}
    <!-- other form fields -->
</form>

Short and simple right?

Check the CSRF Token

You can check the CSRF token using event filters:

// This middleware checks if the request is a POST request and if it is, it checks if the CSRF token is valid
Flight::before('start', function() {
    if(Flight::request()->method == 'POST') {

        // capture the csrf token from the form values
        $token = Flight::request()->data->csrf_token;
        if($token !== Flight::session()->get('csrf_token')) {
            Flight::halt(403, 'Invalid CSRF token');
        }
    }
});

Or you can use a middleware class:

// app/middleware/CsrfMiddleware.php

namespace app\middleware;

class CsrfMiddleware
{
    public function before(array $params): void
    {
        if(Flight::request()->method == 'POST') {
            $token = Flight::request()->data->csrf_token;
            if($token !== Flight::session()->get('csrf_token')) {
                Flight::halt(403, 'Invalid CSRF token');
            }
        }
    }
}

// index.php or wherever you have your routes
Flight::group('', function(Router $router) {
    $router->get('/users', [ 'UserController', 'getUsers' ]);
    // more routes
}, [ new CsrfMiddleware() ]);

Cross Site Scripting (XSS)

Cross Site Scripting (XSS) is a type of attack where a malicious website can inject code into your website. Most of these opportunities come from form values that your end users will fill out. You should never trust output from your users! Always assume all of them are the best hackers in the world. They can inject malicious JavaScript or HTML into your page. This code can be used to steal information from your users or perform actions on your website. Using Flight's view class, you can easily escape output to prevent XSS attacks.

// Let's assume the user is clever as tries to use this as their name
$name = '<script>alert("XSS")</script>';

// This will escape the output
Flight::view()->set('name', $name);
// This will output: &lt;script&gt;alert(&quot;XSS&quot;)&lt;/script&gt;

// If you use something like Latte registered as your view class, it will also auto escape this.
Flight::view()->render('template', ['name' => $name]);

SQL Injection

SQL Injection is a type of attack where a malicious user can inject SQL code into your database. This can be used to steal information from your database or perform actions on your database. Again you should never trust input from your users! Always assume they are out for blood. You can use prepared statements in your PDO objects will prevent SQL injection.

// Assuming you have Flight::db() registered as your PDO object
$statement = Flight::db()->prepare('SELECT * FROM users WHERE username = :username');
$statement->execute([':username' => $username]);
$users = $statement->fetchAll();

// If you use the PdoWrapper class, this can easily be done in one line
$users = Flight::db()->fetchAll('SELECT * FROM users WHERE username = :username', [ 'username' => $username ]);

// You can do the same thing with a PDO object with ? placeholders
$statement = Flight::db()->fetchAll('SELECT * FROM users WHERE username = ?', [ $username ]);

// Just promise you will never EVER do something like this...
$users = Flight::db()->fetchAll("SELECT * FROM users WHERE username = '{$username}' LIMIT 5");
// because what if $username = "' OR 1=1; -- "; 
// After the query is build it looks like this
// SELECT * FROM users WHERE username = '' OR 1=1; -- LIMIT 5
// It looks strange, but it's a valid query that will work. In fact,
// it's a very common SQL injection attack that will return all users.

CORS

Cross-Origin Resource Sharing (CORS) is a mechanism that allows many resources (e.g., fonts, JavaScript, etc.) on a web page to be requested from another domain outside the domain from which the resource originated. Flight does not have built in functionality but this can easily be handled with middleware of event filters similar to CSRF.

// app/middleware/CorsMiddleware.php

namespace app\middleware;

class CorsMiddleware
{
    public function before(array $params): void
    {
        $response = Flight::response();
        if (isset($_SERVER['HTTP_ORIGIN'])) {
            $this->allowOrigins();
            $response->header('Access-Control-Allow-Credentials', 'true');
            $response->header('Access-Control-Max-Age', '86400');
        }

        if ($_SERVER['REQUEST_METHOD'] == 'OPTIONS') {
            if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_METHOD'])) {
                $response->header(
                    'Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, PATCH, OPTIONS'
                );
            }
            if (isset($_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS'])) {
                $response->header(
                    "Access-Control-Allow-Headers",
                    $_SERVER['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']
                );
            }
            $response->send();
            exit(0);
        }
    }

    private function allowOrigins(): void
    {
        // customize your allowed hosts here.
        $allowed = [
            'capacitor://localhost',
            'ionic://localhost',
            'http://localhost',
            'http://localhost:4200',
            'http://localhost:8080',
            'http://localhost:8100',
        ];

        if (in_array($_SERVER['HTTP_ORIGIN'], $allowed)) {
            $response = Flight::response();
            $response->header("Access-Control-Allow-Origin", $_SERVER['HTTP_ORIGIN']);
        }
    }
}

// index.php or wherever you have your routes
Flight::route('/users', function() {
    $users = Flight::db()->fetchAll('SELECT * FROM users');
    Flight::json($users);
})->addMiddleware(new CorsMiddleware());

Conclusion

Security is a big deal and it's important to make sure your web applications are secure. Flight provides a number of features to help you secure your web applications, but it's important to always be vigilant and make sure you're doing everything you can to keep your users' data safe. Always assume the worst and never trust input from your users. Always escape output and use prepared statements to prevent SQL injection. Always use middleware to protect your routes from CSRF and CORS attacks. If you do all of these things, you'll be well on your way to building secure web applications.