api/controllers/AuthController.js

  login: function (req, res) {
    var strategies = sails.config.passport
      , providers  = {};

    // Get a list of available providers for use in your templates.
    Object.keys(strategies).forEach(function (key) {
      if (key === 'local') return;

      providers[key] = {
        name : strategies[key].name
      , slug : key
      };
    });

    // Render the `auth/login.ext` view
    res.view({
      providers : providers
    , user: req.user
    , errors : req.flash('error')
    });
  },
  
  .....
  
  callback: function (req, res) {
    passport.callback(req, res, function (err, user) {
      req.login(user, function (err) {
        // If an error was thrown, redirect the user to the login which should
        // take care of rendering the error messages.
        if (err) {
          res.redirect(req.param('action') === 'register' ? '/register' : '/login');
        }
        // Upon successful login, send the user to the account page were req.user
        // will available.
        else {
          res.redirect('/account');
        }
      });
    });
  },

  /**
   * Create a homepage
   * @param {Object} req
   * @param {Object} res
   */
  index: function (req, res) {
    res.view({
      errors: req.flash('error')
    });
  }