AuthenticatesUsers.php

<?php

    protected function attemptLogin(Request $request)
    {
        $guards = array_keys(config('auth.guards'));
        $attempts = [];

        foreach ($guards as $guard) {
            $guardInstance = Auth::guard($guard);

            if ($guardInstance instanceof TokenGuard) {
                // No "API" authentication with this method
                continue;
            }

            $credentials = $this->credentials($request);
            // $attempts[$guard] = $guardInstance->attempt($credentials, $request->filled('remember'));

            if ($guard == 'ldap') {
                $ldap = app()->make(AdldapInterface::class);
                $provider = $ldap->getDefaultProvider();

                $attempts[$guard] = $provider->auth()->attempt(
                    $credentials[$this->username()],
                    $credentials['password'],
                    true
                );
            } else {
                $attempts[$guard] = $guardInstance->attempt($credentials, $request->filled('remember'));
            }
        }

        return (bool)array_search(true, $attempts);
    }