Validate rs/oauth redirect_uri before storing return URL

app/controllers/rs/oauth_controller.rb

@@ -1,4 +1,5 @@
 class Rs::OauthController < ApplicationController
+  prepend_before_action :assert_redirect_uri, only: [:new, :create]
   before_action :require_signed_in_with_username, only: :new
   before_action :authenticate_user!, only: :create
 
@@ -16,8 +17,6 @@ class Rs::OauthController < ApplicationController
                         ["In 1 month", 1.month.from_now],
                         ["In 1 day", 1.day.from_now]]
 
-    http_status :bad_request and return unless @redirect_uri.present?
-
     unless current_user == @user
       sign_out :user
 
@@ -64,8 +63,6 @@ class Rs::OauthController < ApplicationController
     state        = params[:state].presence
     expire_at    = params[:expire_at].presence
 
-    http_status :bad_request and return unless redirect_uri.present?
-
     if permissions.empty?
       redirect_to(url_with_state("#{redirect_uri}#error=invalid_scope", state),
                   allow_other_host: true) and return
@@ -97,6 +94,10 @@ class Rs::OauthController < ApplicationController
 
   private
 
+  def assert_redirect_uri
+    http_status :bad_request unless params[:redirect_uri].present?
+  end
+
   def require_signed_in_with_username
     unless user_signed_in?
       session[:user_return_to] = request.url