Rails – Simple Google Login

admin_controller.rb

class AdminController < ApplicationController
  before_filter :set_user, :authorized?
  layout "admin"

  private

  def set_user
    @current_user = User.find(session[:current_user_id]) if admin?
  end

  def current_user
    set_user unless @current_user
    @current_user
  end

  def authorized?
    #unless current_user.has_role? :admin
    unless admin?
      flash[:error] = "You are not authorized to view this page."
      redirect_to admin_login_path
    end
  end

  def admin?
    session[:current_user_id]
  end
end

create_users.rb

class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users do |t|
      t.string :name
      t.string :uid
      t.string :email
      t.string :domain
      t.string :image_url

      t.timestamps
    end
  end
end

Gemfile

gem "omniauth"
gem "omniauth-google-oauth2"

omniauth.rb

# config/initializers/omniauth.rb
Rails.application.config.middleware.use OmniAuth::Builder do
  provider :google_oauth2, ENV["GOOGLE_CLIENT_ID"], ENV["GOOGLE_CLIENT_SECRET"]

  OmniAuth.config.logger = Rails.logger
end

routes.rb

get '/auth/:provider/callback', to: 'sessions#create'

sessions_controller.rb

class SessionsController < ApplicationController
  skip_before_action :validate_user, only: :create
 
  def create
    user = User.find_or_create_by(email: google_params[:info][:email]) do |user|
      user.name = google_params[:info][:name],
      user.domain = google_params[:extra][:raw_info][:hd],
      user.uid = google_params[:uid],
      user.avatar_url = google_params[:info][:image] 
    end
 
    if user.valid_user?
      session[:current_user_id] = user.id
      redirect_to :admin_root
    else
      flash[:notice] = "Error logging in.<br>Please request access."
      redirect_to :admin_login
    end
  end
 
  private
 
  def google_params
    @google_params ||= request.env['omniauth.auth']
  end
end

User.rb

class User < ActiveRecord::Base
  validates :name,   presence: true
  validates :email,  presence: true, uniqueness: true
  validates :uid,    presence: true, uniqueness: true
  validates :domain, presence: true, inclusion: {
    in: ["mycompany.com"]
  }

  def valid_user?
    valid? && has_access?
  end

  def has_access?
    User.admin_emails.include?(email)
  end

  def can_post?
    User.super_admin_emails.include?(email)
  end

  private

  def self.super_admin_emails
    [
      "[email protected]",
      "[email protected]"
    ] + admin_super_env_emails
  end

  def self.admin_emails
    [
      "[email protected]",
      "[email protected]"
    ] + admin_env_emails + super_admin_emails
  end

  def self.admin_env_emails
    ENV["HAS_ADMIN_ACCESS"].to_s.split(",").map(&:strip)
  end

  def self.admin_super_env_emails
    ENV["HAS_SUPER_ACCESS"].to_s.split(",").map(&:strip)
  end
end