Need

Implementation of a robust and secure authentication mechanism

Context

• Usage of PHP 7.0 for server-side scripting and web development
• Usage of Request for making HTTP requests
• Usage of the User dependency for managing user-related functionality
• Usage of Hash for secure password hashing and data encryption

Description

Non compliant code

        public function login(Request $request)
{
    $username = $request->input('username');
    $password = $request->input('password');

    $user = User::where('username', $username)->first();

    if ($user && Hash::check($password, $user->password)) {
        // Authentication passed...
        return redirect()->intended('dashboard');
    } else {
        return redirect()->back();
    }
}
        
        

The above code is an example of a login function in a Laravel application that is vulnerable to Authentication mechanism absence or evasion
- Redirect.

Here's how the code works:

1. The login function receives a Request object as a parameter, which contains the data sent by the client. In this case, we're interested in the 'username' and 'password' fields.

2. The function retrieves the user from the database whose username matches the one provided by the client.

3. If such a user exists and the provided password matches the user's password, the function redirects the client to the 'dashboard' page.

4. If the authentication fails, the function redirects the client back to the previous page.

The vulnerability lies in the fact that the application does not check if the client is authenticated before redirecting them. An attacker can manipulate the redirect URL to bypass the login page and gain access to the application. For example, if they know a valid username, they can change the redirect URL to 'dashboard', which would allow them to access the dashboard page without having to provide a password.

Steps

• Implement a strong authentication mechanism that includes a second factor of authentication (2FA).
• Ensure that the redirect URL is validated and cannot be manipulated by the user.
• Use secure and encrypted sessions to maintain the user's state.
• Implement rate limiting to prevent brute force attacks.
• Use secure and encrypted cookies to store session information.
• Implement CSRF tokens to prevent cross-site request forgery attacks.
• Ensure that all user input is properly sanitized and validated to prevent SQL injection attacks.

Compliant code

        public function login(Request $request)
{
    $username = $request->input('username');
    $password = $request->input('password');

    $user = User::where('username', $username)->first();

    if ($user && Hash::check($password, $user->password)) {
        // Authentication passed...
        $request->session()->regenerate();
        return redirect()->secure('dashboard');
    } else {
        return redirect()->back()->with('error', 'Invalid credentials');
    }
}
        
        

The updated code includes several security enhancements to address the identified vulnerability.

1. Session Regeneration: After successful authentication, the user's session ID is regenerated using $request->session()->regenerate(). This is a security best practice that prevents session fixation attacks, where an attacker could predict or control the session ID.

2. Secure Redirects: The redirect()->secure('dashboard') method is used to ensure that the redirect URL is secure and cannot be manipulated by the user. This prevents open redirect vulnerabilities, where an attacker could trick a user into visiting a malicious site.

3. Error Messages: A generic error message is returned when authentication fails. This prevents user enumeration, where an attacker could determine if a username is valid based on the error message.

Additional security measures that should be implemented but are not shown in the code include:

- Two-Factor Authentication (2FA): This provides an additional layer of security by requiring users to provide two forms of identification.
- Rate Limiting: This prevents brute force attacks by limiting the number of login attempts a user can make in a certain period of time.
- CSRF Tokens: These tokens can be used to prevent cross-site request forgery attacks, where an attacker tricks a user into performing an action they did not intend to.
- Input Sanitization and Validation: All user input should be properly sanitized and validated to prevent SQL injection attacks.

References

• 298. Authentication mechanism absence or evasion - Redirect