Implements support for rack-cors for API JavaScript access in end-user browser

Gemfile

@@ -127,6 +127,8 @@ gem 'rack-mini-profiler', require: false  # require: false #, git: 'git://github
 gem 'redis-rack-cache', require: false
 gem 'rack-cache', require: false
 
+gem 'rack-cors', require: false
+
 # perftools only works on 1.9 atm
 group :profile do
   # travis refuses to install this, instead of fuffing, just avoid it for now

Gemfile.lock

@@ -331,6 +331,8 @@ GEM
     rack (1.4.5)
     rack-cache (1.2)
       rack (>= 0.4)
+    rack-cors (0.2.7)
+      rack
     rack-mini-profiler (0.1.26)
       rack (>= 1.1.3)
     rack-openid (1.3.1)
@@ -526,6 +528,7 @@ DEPENDENCIES
   pg
   pry-rails
   rack-cache
+  rack-cors
   rack-mini-profiler
   rails
   rails_multisite!

config/environments/production.sample.rb

@@ -55,6 +55,13 @@ Discourse::Application.configure do
   # allows admins to use mini profiler
   config.enable_mini_profiler = true
 
+  # allows Cross-origin resource sharing (CORS) for API access in JavaScript (default to false for security).
+  # See the initializer and https://github.com/cyu/rack-cors for configuration documentation.
+  #
+  # config.enable_rack_cors = false
+  # config.rack_cors_origins = ['*']
+  # config.rack_cors_resource = ['*', { :headers => :any, :methods => [:get, :post, :options] }]
+
   # Discourse strongly recommend you use a CDN.
   # For origin pull cdns all you need to do is register an account and configure
   # config.action_controller.asset_host = "http://YOUR_CDN_HERE"

config/initializers/08-rack-cors.rb

@@ -0,0 +1,13 @@
+if Rails.configuration.respond_to?(:enable_rack_cors) && Rails.configuration.enable_rack_cors
+  require 'rack/cors'
+
+  cors_origins  = Rails.configuration.respond_to?(:rack_cors_origins) ? Rails.configuration.rack_cors_origins : ['*']
+  cors_resource = Rails.configuration.respond_to?(:rack_cors_resource) ? Rails.configuration.rack_cors_resource : ['*', { headers: :any, methods: [:get, :post, :options] }]
+
+  Rails.configuration.middleware.use Rack::Cors do
+    allow do
+      origins *cors_origins
+      resource *cors_resource
+    end
+  end
+end