Authentication/login in Laravel using LDAP with no admin connection?

I am trying to get Laravel 5.4 to authenticate users using LDAP instead of the traditional database method.

There is a library for that already, Adldap2/Adldap2-Laravel. The problem is that this library:

1. connects first the the LDAP server as an admin user
2. then searches for the user that wants to log into my app
3. checks that the password is correct
4. stores the data associated to that user in the "local" Laravel database
5. reconnects to the LDAP as the admin user

This doesn't work in my case, because there are no admins in the LDAP server that I ̶w̶a̶n̶t̶  have to connect to; only usernames allowed to use the app, with no roles.

As seen in an already existing issue, I modified the LoginController class with the follwoing code (for testing purposes I am trying to connect to the server provided in this web page: Online LDAP Test Server).

protected function attemptLogin(Request $request) {
    $conn_settings = config('adldap.connections')[config('adldap_auth.connection')]['connection_settings'];
    $credentials = $request->only(config('adldap_auth.usernames.eloquent'), 'password');

    $user_format = env('ADLDAP_USER_FORMAT', 'uid=%s,' . $conn_settings['base_dn']);
    $userdn = sprintf($user_format, $credentials[config('adldap_auth.usernames.eloquent')]);
    $pass = $credentials['password'];

    if(Adldap::auth()->attempt($userdn, $pass, $bindAsUser = true)) {
        return true;
    }

    return false;
}

The problem that I have now is that, once logged in with the correct credentials, I am sent back to the login form. When the credentials are wrong, I get the corresponding error message.

My configuration files, just in case:

.env:

ADLDAP_CONTROLLERS=ldap.forumsys.com 
ADLDAP_BASEDN=dc=example,dc=com
ADLDAP_USER_FORMAT=uid=%s,dc=example,dc=com

adldap_auth.php:

[
    'connection' => env('ADLDAP_CONNECTION', 'default'),
    'provider' => Adldap\Laravel\Auth\DatabaseUserProvider::class,
    'resolver' => Adldap\Laravel\Auth\Resolver::class,
    'importer' => Adldap\Laravel\Auth\Importer::class,
    'rules' => [
        Adldap\Laravel\Validation\Rules\DenyTrashed::class,
        // Adldap\Laravel\Validation\Rules\OnlyImported::class,
    ],
    'scopes' => [
        Adldap\Laravel\Scopes\UpnScope::class,
    ],
    'usernames' => [
        'ldap' => 'uid',
        'eloquent' => 'username',
    ],
    'login_fallback' => env('ADLDAP_LOGIN_FALLBACK', false),
    'password_sync' => env('ADLDAP_PASSWORD_SYNC', true),
    'windows_auth_attribute' => ['samaccountname' => 'AUTH_USER'],
    'sync_attributes' => [
        'username' => 'uid',
        'name' => 'cn',
    ],
];

adldap.php:

return [
    'connections' => [
        'default' => [
            'auto_connect' => false,
            'connection' => Adldap\Connections\Ldap::class,
            'schema' => Adldap\Schemas\ActiveDirectory::class,
            'connection_settings' => [
                'account_prefix' => env('ADLDAP_ACCOUNT_PREFIX', ''),
                'account_suffix' => env('ADLDAP_ACCOUNT_SUFFIX', ''),
                'domain_controllers' => explode(' ', env('ADLDAP_CONTROLLERS', 'corp-dc1.corp.acme.org corp-dc2.corp.acme.org')),
                'port' => env('ADLDAP_PORT', 389),
                'timeout' => env('ADLDAP_TIMEOUT', 5),
                'base_dn' => env('ADLDAP_BASEDN', 'dc=corp,dc=acme,dc=org'),
                'admin_account_suffix' => env('ADLDAP_ADMIN_ACCOUNT_SUFFIX', ''),
                'admin_username' => env('ADLDAP_ADMIN_USERNAME', ''),
                'admin_password' => env('ADLDAP_ADMIN_PASSWORD', ''),
                'follow_referrals' => true,
                'use_ssl' => false,
                'use_tls' => false,
            ],
        ],
    ],
]

via jotaelesalinas