discourse/lib/content_security_policy/extension.rb

# frozen_string_literal: true
class ContentSecurityPolicy
  module Extension
    extend self

    def site_setting_extension
      { script_src: SiteSetting.content_security_policy_script_src.split("|") }
    end

    def plugin_extensions
      [].tap do |extensions|
        Discourse.plugins.each do |plugin|
          extensions.concat(plugin.csp_extensions) if plugin.enabled?
        end
      end
    end

    THEME_SETTING = "extend_content_security_policy"

    def theme_extensions(theme_id)
      key = "theme_extensions_#{theme_id}"
      cache.defer_get_set(key) { find_theme_extensions(theme_id) }
    end

    def clear_theme_extensions_cache!
      cache.clear
    end

    private

    def cache
      @cache ||= DistributedCache.new("csp_extensions")
    end

    def find_theme_extensions(theme_id)
      extensions = []
      theme_ids = Theme.transform_ids(theme_id)

      Theme
        .where(id: theme_ids)
        .find_each do |theme|
          theme.cached_settings.each do |setting, value|
            extensions << build_theme_extension(value.split("|")) if setting.to_s == THEME_SETTING
          end
        end

      extensions << build_theme_extension(
        ThemeModifierHelper.new(theme_ids: theme_ids).csp_extensions,
      )

      html_fields =
        ThemeField.where(
          theme_id: theme_ids,
          target_id: ThemeField.basic_targets.map { |target| Theme.targets[target.to_sym] },
          name: ThemeField.html_fields,
        )

      auto_script_src_extension = { script_src: [] }
      html_fields.each(&:ensure_baked!)
      doc = html_fields.map(&:value_baked).join("\n")

      Nokogiri::HTML5
        .fragment(doc)
        .css("script[src]")
        .each do |node|
          src = node["src"]
          uri = URI(src)

          next if GlobalSetting.cdn_url && src.starts_with?(GlobalSetting.cdn_url) # Ignore CDN urls (theme-javascripts)
          next if uri.host.nil? # Ignore same-domain scripts (theme-javascripts)
          next if uri.path.nil? # Ignore raw hosts

          uri.query = nil # CSP should not include query part of url

          uri_string = uri.to_s.sub(%r{\A//}, "") # Protocol-less CSP should not have // at beginning of URL

          auto_script_src_extension[:script_src] << uri_string
        rescue URI::Error
          # Ignore invalid URI
        end

      extensions << auto_script_src_extension

      extensions
    end

    def build_theme_extension(entries)
      {}.tap do |extension|
        entries.each do |entry|
          directive, source = entry.split(":", 2).map(&:strip)

          extension[directive] ||= []
          extension[directive] << source
        end
      end
    end
  end
end