discourse/config/initializers/008-rack-cors.rb

# frozen_string_literal: true

class Discourse::Cors
  ORIGINS_ENV = "Discourse_Cors_Origins"

  def initialize(app, options = nil)
    @app = app
    if GlobalSetting.enable_cors && GlobalSetting.cors_origin.present?
      @global_origins = GlobalSetting.cors_origin.split(',').map { |x| x.strip.chomp('/') }
    end
  end

  def call(env)

    cors_origins = @global_origins || []
    cors_origins += SiteSetting.cors_origins.split('|') if SiteSetting.cors_origins.present?
    cors_origins = cors_origins.presence

    if env['REQUEST_METHOD'] == ('OPTIONS') && env['HTTP_ACCESS_CONTROL_REQUEST_METHOD']
      return [200, Discourse::Cors.apply_headers(cors_origins, env, {}), []]
    end

    env[Discourse::Cors::ORIGINS_ENV] = cors_origins if cors_origins

    status, headers, body = @app.call(env)
    headers ||= {}

    Discourse::Cors.apply_headers(cors_origins, env, headers)

    [status, headers, body]
  end

  def self.apply_headers(cors_origins, env, headers)
    request_method = env['REQUEST_METHOD']
    cdn_endpoints = ["/assets", "/javascripts"]

    if cdn_endpoints.include?(env['SCRIPT_NAME']) && Discourse.is_cdn_request?(env, request_method)
      Discourse.apply_cdn_headers(headers)
    elsif cors_origins
      origin = nil
      if origin = env['HTTP_ORIGIN']
        origin = nil unless cors_origins.include?(origin)
      end

      headers['Access-Control-Allow-Origin'] = origin || cors_origins[0]
      headers['Access-Control-Allow-Headers'] = 'Content-Type, Cache-Control, X-Requested-With, X-CSRF-Token, Discourse-Present, User-Api-Key, User-Api-Client-Id, Authorization'
      headers['Access-Control-Allow-Credentials'] = 'true'
      headers['Access-Control-Allow-Methods'] = 'POST, PUT, GET, OPTIONS, DELETE'
    end

    headers
  end
end

if GlobalSetting.enable_cors || GlobalSetting.cdn_url
  Rails.configuration.middleware.insert_before ActionDispatch::Flash, Discourse::Cors
end