ruby on rails - New User gets a blank page by entering from Facebook canvas -

every time when new user (or test user) access app facebook (canvas) gets empty page.

if user navigate direct app works. user permission dialog facebook , have grant requested permissions. after user can use app facebook canvas or direct *www.my_app.com*.

what know problem:

1. it occurs new/test user did not grant permissions facebook app
2. it occurs on direct access facebook canvas.

i think permission dialog can't shown facebook don't know why.

my app developed ruby rails , uses omniauth 1.4.0 login.

the gem-file

gem 'omniauth' gem 'omniauth-facebook', '1.4.0' gem 'oauth2' gem 'koala' 

the routes.rb:

match '/canvas'                  => 'sessions#facebook_canvas' match '/auth/:provider/callback' => 'sessions#create',             :as => :create_session 

the omniauth.rb initializer:

rails.application.config.middleware.use omniauth::builder   openssl::ssl::verify_peer = openssl::ssl::verify_none   provider :facebook, app_id, app_secret,        {:scope   => 'email, user_groups, friends_groups, read_stream, read_friendlists, friends_likes, friends_status, offline_access',         :display => 'popup',         :client_options => {:ssl => {:ca_file => '/usr/lib/ssl/certs/ca-certificates.crt'}} } end 

the sessions_controller :

# modified sample code omniauth handle signed request def facebook_canvas    session[:canvas]         = true    session[:signed_request] = params[:signed_request]    # redirect /auth/facebook here parse    # signed_request fb sends us, asking auth if user has    # not granted access, or moving straight    # callback have granted access.    #    # pass state parameter can detect in our callback    # custom rendering/redirection canvas app page    redirect_to "/auth/facebook?signed_request=#{request.params['signed_request']}&state=canvas" end  # create session, when user  def create    auth = request.env["omniauth.auth"]    user = user.from_omniauth(env["omniauth.auth"])    if user         session[:fb_token] = auth["credentials"]["token"] if auth['provider'] == 'facebook'            redirect_to_target_or_default root_url #, :notice => "logged in successfully."       redirect_to confirm_abg_path(:user => user.id)    else       flash.now[:alert] = "invalid login or password."       redirect_to root_url    end end 

i hope can me.