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Message flooding

Need​

Mitigation of message flooding attacks

Context​

  • Usage of PHP 7.0 for server-side scripting and web development
  • Usage of Request for making HTTP requests in Node.js
  • Usage of Mail for sending emails
  • Usage of MessageMail for sending emails and managing email templates

Description​

Non compliant code​

public function sendMessage(Request $request)
{
    $email = $request->input('email');
    $phoneNumber = $request->input('phoneNumber');
    $message = $request->input('message');

    Mail::to($email)->send(new MessageMail($message));
    $this->sendSMS($phoneNumber, $message);
}

In this Laravel controller function, the application receives an HTTP request with an email address, phone number, and a message. The application then uses Laravel's built-in Mail facade to send an email to the provided email address and a custom sendSMS method to send an SMS message to the provided phone number.

The vulnerability in this code lies in the fact that there are no checks or restrictions on the number of messages that can be sent to a particular email address or phone number. This means that an attacker could potentially send a large number of HTTP requests with the same email address and phone number, causing a flood of messages to be sent to the victim. This could lead to the saturation of the victim's email inbox and SMS messages, consuming their resources and potentially causing a denial of service.

Steps​

  • Implement rate limiting to control the number of messages a user can send within a certain time period.
  • Add a CAPTCHA to the message sending process to prevent automated scripts from sending mass messages.
  • Validate the email and phone number inputs to ensure they are not being used to send mass messages.
  • Implement a user authentication system to ensure only registered users can send messages.
  • Monitor for suspicious activity such as a sudden spike in the number of messages being sent.

Compliant code​

use Illuminate\\Support\\Facades\\RateLimiter;

public function sendMessage(Request $request)
{
    $email = $request->input('email');
    $phoneNumber = $request->input('phoneNumber');
    $message = $request->input('message');

    // Validate the email and phone number
    $request->validate([
        'email' => 'required|email',
        'phoneNumber' => 'required|numeric',
        'message' => 'required'
    ]);

    // Implement rate limiting
    $tooManyAttempts = RateLimiter::tooManyAttempts('sendMessage', 5, 1); // 5 attempts per minute

    if ($tooManyAttempts) {
        return response()->json(['message' => 'Too many attempts. Please try again later.'], 429);
    }

    // If not too many attempts, send the message and increment the rate limiter
    Mail::to($email)->send(new MessageMail($message));
    $this->sendSMS($phoneNumber, $message);

    RateLimiter::hit('sendMessage', 60); // Increment the rate limiter
}

The updated code includes several security measures to prevent message flooding:

  1. Input Validation: The validate method is used to ensure that the email and phone number inputs are in the correct format. This prevents invalid or malicious inputs from being processed.

  2. Rate Limiting: The RateLimiter facade is used to limit the number of messages a user can send within a certain time period. In this case, a user can only send 5 messages per minute. If a user exceeds this limit, a 429 (Too Many Requests) response is returned.

  3. User Authentication: Although not shown in the code, it is recommended to implement a user authentication system to ensure only registered users can send messages. This can be done using Laravel's built-in authentication system.

  4. Monitoring: Although not shown in the code, it is recommended to monitor for suspicious activity such as a sudden spike in the number of messages being sent. This can be done using various monitoring tools and services.

  5. CAPTCHA: Although not shown in the code, it is recommended to add a CAPTCHA to the message sending process to prevent automated scripts from sending mass messages. This can be done using various CAPTCHA services.

References​

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