discourse/app/jobs/regular/pull_hotlinked_images.rb

# frozen_string_literal: true

module Jobs

  class PullHotlinkedImages < ::Jobs::Base
    sidekiq_options queue: 'low'

    def initialize
      @max_size = SiteSetting.max_image_size_kb.kilobytes
    end

    def execute(args)
      disable_if_low_on_disk_space

      @post_id = args[:post_id]
      raise Discourse::InvalidParameters.new(:post_id) if @post_id.blank?

      post = Post.find_by(id: @post_id)
      return if post.nil? || post.topic.nil?

      hotlinked_map = post.post_hotlinked_media.map { |r| [r.url, r] }.to_h

      changed_hotlink_records = false

      extract_images_from(post.cooked).each do |node|
        download_src = original_src = node['src'] || node['href']
        download_src = "#{SiteSetting.force_https ? "https" : "http"}:#{original_src}" if original_src.start_with?("//")
        normalized_src = normalize_src(download_src)

        next if !should_download_image?(download_src, post)

        hotlink_record = hotlinked_map[normalized_src]

        if hotlink_record.nil?
          hotlinked_map[normalized_src] = hotlink_record = PostHotlinkedMedia.new(
            post: post,
            url: normalized_src
          )
          begin
            hotlink_record.upload = attempt_download(download_src, post.user_id)
            hotlink_record.status = :downloaded
          rescue ImageTooLargeError
            hotlink_record.status = :too_large
          rescue ImageBrokenError
            hotlink_record.status = :download_failed
          rescue UploadCreateError
            hotlink_record.status = :upload_create_failed
          end
        end

        if hotlink_record.changed?
          changed_hotlink_records = true
          hotlink_record.save!
        end
      rescue => e
        raise e if Rails.env.test?
        log(:error, "Failed to pull hotlinked image (#{download_src}) post: #{@post_id}\n" + e.message + "\n" + e.backtrace.join("\n"))
      end

      if changed_hotlink_records
        post.trigger_post_process(
          bypass_bump: true,
          skip_pull_hotlinked_images: true # Avoid an infinite loop of job scheduling
        )
      end

      if hotlinked_map.size > 0
        Jobs.cancel_scheduled_job(:update_hotlinked_raw, post_id: post.id)
        update_raw_delay = SiteSetting.editing_grace_period + 1
        Jobs.enqueue_in(update_raw_delay, :update_hotlinked_raw, post_id: post.id)
      end
    end

    def download(src)
      downloaded = nil

      begin
        retries ||= 3

        if SiteSetting.verbose_upload_logging
          Rails.logger.warn("Verbose Upload Logging: Downloading hotlinked image from #{src}")
        end

        downloaded = FileHelper.download(
          src,
          max_file_size: @max_size,
          retain_on_max_file_size_exceeded: true,
          tmp_file_name: "discourse-hotlinked",
          follow_redirect: true
        )
      rescue => e
        if SiteSetting.verbose_upload_logging
          Rails.logger.warn("Verbose Upload Logging: Error '#{e.message}' while downloading #{src}")
        end

        if (retries -= 1) > 0 && !Rails.env.test?
          sleep 1
          retry
        end
      end

      downloaded
    end

    class ImageTooLargeError < StandardError; end
    class ImageBrokenError < StandardError; end
    class UploadCreateError < StandardError; end

    def attempt_download(src, user_id)
      # secure-media-uploads endpoint prevents anonymous downloads, so we
      # need the presigned S3 URL here
      src = Upload.signed_url_from_secure_media_url(src) if Upload.secure_media_url?(src)

      hotlinked = download(src)
      raise ImageBrokenError if !hotlinked
      raise ImageTooLargeError if File.size(hotlinked.path) > @max_size

      filename = File.basename(URI.parse(src).path)
      filename << File.extname(hotlinked.path) unless filename["."]
      upload = UploadCreator.new(hotlinked, filename, origin: src).create_for(user_id)

      if upload.persisted?
        upload
      else
        log(:info, "Failed to persist downloaded hotlinked image for post: #{@post_id}: #{src} - #{upload.errors.full_messages.join("\n")}")
        raise UploadCreateError
      end
    end

    def extract_images_from(html)
      doc = Nokogiri::HTML5::fragment(html)

      doc.css("img[src], a.lightbox[href]") -
        doc.css("img.avatar") -
        doc.css(".lightbox img[src]")
    end

    def should_download_image?(src, post = nil)
      # make sure we actually have a url
      return false unless src.present?

      local_bases = [
        Discourse.base_url,
        Discourse.asset_host,
        SiteSetting.external_emoji_url.presence
      ].compact.map { |s| normalize_src(s) }

      if Discourse.store.has_been_uploaded?(src) || normalize_src(src).start_with?(*local_bases) || src =~ /\A\/[^\/]/i
        return false if !(src =~ /\/uploads\// || Upload.secure_media_url?(src))

        # Someone could hotlink a file from a different site on the same CDN,
        # so check whether we have it in this database
        #
        # if the upload already exists and is attached to a different post,
        # or the original_sha1 is missing meaning it was created before secure
        # media was enabled, then we definitely want to redownload again otherwise
        # we end up reusing existing uploads which may be linked to many posts
        # already.
        upload = Upload.consider_for_reuse(Upload.get_from_url(src), post)

        return !upload.present?
      end

      # Don't download non-local images unless site setting enabled
      return false unless SiteSetting.download_remote_images_to_local?

      # parse the src
      begin
        uri = URI.parse(src)
      rescue URI::Error
        return false
      end

      hostname = uri.hostname
      return false unless hostname

      # check the domains blocklist
      SiteSetting.should_download_images?(src)
    end

    def log(log_level, message)
      Rails.logger.public_send(
        log_level,
        "#{RailsMultisite::ConnectionManagement.current_db}: #{message}"
      )
    end

    protected

    def normalize_src(src)
      PostHotlinkedMedia.normalize_src(src)
    end

    def disable_if_low_on_disk_space
      return if Discourse.store.external?
      return if !SiteSetting.download_remote_images_to_local
      return if available_disk_space >= SiteSetting.download_remote_images_threshold

      SiteSetting.download_remote_images_to_local = false

      # log the site setting change
      reason = I18n.t("disable_remote_images_download_reason")
      staff_action_logger = StaffActionLogger.new(Discourse.system_user)
      staff_action_logger.log_site_setting_change("download_remote_images_to_local", true, false, details: reason)

      # also send a private message to the site contact user notify_about_low_disk_space
      notify_about_low_disk_space
    end

    def notify_about_low_disk_space
      SystemMessage.create_from_system_user(Discourse.site_contact_user, :download_remote_images_disabled)
    end

    def available_disk_space
      100 - DiskSpace.percent_free("#{Rails.root}/public/uploads")
    end
  end

end