Laravel: How to authenticate users without DB

In short, is it possible to authenticate without DB (instead, using User Provider)?

I've seen posts about how to authenticate without password, but would it be ever possible to authenticate without DB?

Here is what I've been trying to achieve...

Ask the user to submit a PIN

Compare the PIN with a value within .env

If the PIN is correct, authenticate the user

It seems to be possible to do authenticate without a traditional RDBMS by introducing a user provider.

However, the doc doesn't seem to describe how the user provider should look like.

Here are snippets of my code (well, I simply mimicked the doc)...

class AuthServiceProvider extends ServiceProvider {

    public function boot()
    {
        $this->registerPolicies();

        Auth::provider('myUser', function ($app, array $config) {
            // Return an instance of Illuminate\Contracts\Auth\UserProvider...

            return new MyUserProvider($app->make('myUser'));
        });
    }
}

In auth.php...

'providers' => [
    'users' => [
        'driver' => 'myUser',
    ],
],

Now, I have no clue as to how to proceed.

So, I'd like to know...

1. How the user provider should look like

2. if it's possible to authenticate users with env() in the first place

Any advice will be appreciated.

via Chebli Mohamed