google.md

Google Authentication

How it works

The user entity has to be linked with Google Authenticator first. This is done by generating a secret code and storing it in the user entity. Users can add that code to the Google Authenticator app on their mobile. The app will generate a 6-digit numeric code from it that changes every 30 seconds.

On successful authentication the bundle checks if there is a secret stored in the user entity. If that's the case it will ask for the authentication code. The user must enter the code currently shown in the Google Authenticator app to gain access.

For more information see the Google Authenticator website.

Basic Configuration

To enable this authentication method add this to your configuration:

# config/packages/scheb_two_factor.yaml
scheb_two_factor:
    google:
        enabled: true

Your user entity has to implement Scheb\TwoFactorBundle\Model\Google\TwoFactorInterface. To activate Google Authenticator for a user, generate a secret code and persist it with the user entity.

namespace Acme\DemoBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Scheb\TwoFactorBundle\Model\Google\TwoFactorInterface;

class User implements TwoFactorInterface
{
    /**
     * @ORM\Column(name="googleAuthenticatorSecret", type="string", nullable=true)
     */
    private $googleAuthenticatorSecret;

    // [...]
    
    public function isGoogleAuthenticatorEnabled(): bool
    {
        return $this->googleAuthenticatorSecret ? true : false;
    }

    public function getGoogleAuthenticatorUsername(): string
    {
        return $this->username;
    }

    public function getGoogleAuthenticatorSecret(): string
    {
        return $this->googleAuthenticatorSecret;
    }

    public function setGoogleAuthenticatorSecret(?string $googleAuthenticatorSecret): void
    {
        $this->googleAuthenticatorSecret = $googleAuthenticatorSecret;
    }
}

Custom Authentication Form Template

The bundle uses Resources/views/Authentication/form.html.twig to render the authentication form. If you want to use a different template you can simply register it in configuration:

# config/packages/scheb_two_factor.yaml
scheb_two_factor:
    google:
        template: security/2fa_form.html.twig

Generating a Secret Code

The service scheb_two_factor.security.google_authenticator provides a method to generate new secret for Google Authenticator.

$secret = $container->get("scheb_two_factor.security.google_authenticator")->generateSecret();

With Symfony 4 you use the dependency injection to get the services:

use Scheb\TwoFactorBundle\Security\TwoFactor\Provider\Google\GoogleAuthenticatorInterface;

public function index(GoogleAuthenticatorInterface $twoFactor)
{
    // ...
    $secret = $twoFactor->generateSecret();
}

QR Codes

Warning To generate the QR-code an external service from Google is used. That means the user's personal secure code is transmitted to that service. This is considered a bad security practice. If you don't like this solution, you should generate the QR-code locally, for example with endroid/qr-code-bundle.

If a user entity has a secret code stored, you can generate a nice-looking QR code from it, which can be scanned by the Google Authenticator app.

$url = $container->get("scheb_two_factor.security.google_authenticator")->getUrl($user);
echo '<img src="'.$url.'" />';

If you can't or don't want to use Google charts to render the QR code you can also get the contents which need to be encoded in the QR code:

$qrContent = $container->get("scheb_two_factor.security.google_authenticator")->getQRContent($user);

You can then encode $qrContent in a QR code the way you like (e.g. by using one of the many js-libraries).

use Scheb\TwoFactorBundle\Security\TwoFactor\Provider\Google\GoogleAuthenticatorInterface;

public function index(GoogleAuthenticatorInterface $twoFactor)
{
    // ...
    $url = $twoFactor->getUrl();
    $qrContent = $twoFactor->getQRContent()
}