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 download(src)
      downloaded = nil

      begin
        retries ||= 3

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

      downloaded
    end

    def execute(args)
      post_id = args[:post_id]
      raise Discourse::InvalidParameters.new(:post_id) unless post_id.present?

      post = Post.find_by(id: post_id)
      return unless post.present?

      raw = post.raw.dup
      start_raw = raw.dup

      downloaded_urls = {}

      large_images = JSON.parse(post.custom_fields[Post::LARGE_IMAGES].presence || "[]")
      broken_images = JSON.parse(post.custom_fields[Post::BROKEN_IMAGES].presence || "[]")
      downloaded_images = JSON.parse(post.custom_fields[Post::DOWNLOADED_IMAGES].presence || "{}")

      has_new_large_image  = false
      has_new_broken_image = false
      has_downloaded_image = false

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

        if should_download_image?(src, post)
          begin
            # have we already downloaded that file?
            schemeless_src = normalize_src(original_src)

            unless downloaded_images.include?(schemeless_src) || large_images.include?(schemeless_src) || broken_images.include?(schemeless_src)

              # 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)

              if hotlinked = download(src)
                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(post.user_id)

                  if upload.persisted?
                    downloaded_urls[src] = upload.url
                    downloaded_images[normalize_src(src)] = upload.id
                    has_downloaded_image = true
                  else
                    log(:info, "Failed to pull hotlinked image for post: #{post_id}: #{src} - #{upload.errors.full_messages.join("\n")}")
                  end
                else
                  large_images << normalize_src(original_src)
                  has_new_large_image = true
                end
              else
                broken_images << normalize_src(original_src)
                has_new_broken_image = true
              end
            end

            # have we successfully downloaded that file?
            if downloaded_urls[src].present?
              escaped_src = Regexp.escape(original_src)

              replace_raw = ->(match, match_src, replacement, _index) {

                if normalize_src(src) == normalize_src(match_src)
                  replacement =
                    if replacement.include?(InlineUploads::PLACEHOLDER)
                      replacement.sub(InlineUploads::PLACEHOLDER, upload.short_url)
                    elsif replacement.include?(InlineUploads::PATH_PLACEHOLDER)
                      replacement.sub(InlineUploads::PATH_PLACEHOLDER, upload.short_path)
                    end

                  raw = raw.gsub(
                    match,
                    replacement
                  )
                end
              }

              # there are 6 ways to insert an image in a post
              # HTML tag - <img src="http://...">
              InlineUploads.match_img(raw, external_src: true, &replace_raw)

              # BBCode tag - [img]http://...[/img]
              InlineUploads.match_bbcode_img(raw, external_src: true, &replace_raw)

              # Markdown linked image - [![alt](http://...)](http://...)
              # Markdown inline - ![alt](http://...)
              # Markdown inline - ![](http://... "image title")
              # Markdown inline - ![alt](http://... "image title")
              InlineUploads.match_md_inline_img(raw, external_src: true, &replace_raw)

              # Direct link
              raw.gsub!(/^#{escaped_src}(\s?)$/) { "![](#{upload.short_url})#{$1}" }
            end
          rescue => e
            if Rails.env.test?
              raise e
            else
              log(:error, "Failed to pull hotlinked image (#{src}) post: #{post_id}\n" + e.message + "\n" + e.backtrace.join("\n"))
            end
          end
        end
      end

      large_images.uniq!
      broken_images.uniq!

      post.custom_fields[Post::LARGE_IMAGES]      = large_images.to_json      if large_images.present?
      post.custom_fields[Post::BROKEN_IMAGES]     = broken_images.to_json     if broken_images.present?
      post.custom_fields[Post::DOWNLOADED_IMAGES] = downloaded_images.to_json if downloaded_images.present?
      # only save custom fields if there are any
      post.save_custom_fields if large_images.present? || broken_images.present? || downloaded_images.present?

      post.reload

      if start_raw == post.raw && raw != post.raw
        changes = { raw: raw, edit_reason: I18n.t("upload.edit_reason") }
        post.revise(Discourse.system_user, changes, bypass_bump: true, skip_staff_log: true)
      elsif has_downloaded_image || has_new_large_image || has_new_broken_image
        post.trigger_post_process(
          bypass_bump: true,
          skip_pull_hotlinked_images: true # Avoid an infinite loop of job scheduling
        )
      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,
      ].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 blacklist
      SiteSetting.should_download_images?(src)
    end

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

    private

    def normalize_src(src)
      uri = Addressable::URI.heuristic_parse(src)
      uri.normalize!
      uri.scheme = nil
      uri.to_s
    rescue URI::Error, Addressable::URI::InvalidURIError
      src
    end
  end

end