Rake task for removing exif from uploads

Adds a rake task which can be used for removing EXIF
data from existing uploads.

1 files changed, 156 insertions, 0 deletions

diff --git a/lib/gitlab/sanitizers/exif.rb b/lib/gitlab/sanitizers/exif.rb
new file mode 100644
index 00000000000..0928ccdc324
--- /dev/null
+++ b/lib/gitlab/sanitizers/exif.rb
@@ -0,0 +1,156 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Sanitizers
+    class Exif
+      # these tags are not removed from the image
+      WHITELISTED_TAGS = %w(
+        ResolutionUnit
+        XResolution
+        YResolution
+        YCbCrSubSampling
+        YCbCrPositioning
+        BitsPerSample
+        ImageHeight
+        ImageWidth
+        ImageSize
+        Copyright
+        CopyrightNotice
+        Orientation
+      ).freeze
+
+      # these tags are common in exiftool output, these
+      # do not contain any sensitive information, but
+      # we don't need to preserve them when removing
+      # exif tags
+      IGNORED_TAGS = %w(
+        ColorComponents
+        EncodingProcess
+        ExifByteOrder
+        ExifToolVersion
+        JFIFVersion
+        Directory
+        FileAccessDate
+        FileInodeChangeDate
+        FileModifyDate
+        FileName
+        FilePermissions
+        FileSize
+        SourceFile
+        Megapixels
+        FileType
+        FileTypeExtension
+        MIMEType
+      ).freeze
+
+      ALLOWED_TAGS = WHITELISTED_TAGS + IGNORED_TAGS
+      EXCLUDE_PARAMS = WHITELISTED_TAGS.map { |tag| "-#{tag}" }
+
+      attr_reader :logger
+
+      def initialize(logger: Rails.logger)
+        @logger = logger
+      end
+
+      # rubocop: disable CodeReuse/ActiveRecord
+      def batch_clean(start_id: nil, stop_id: nil, dry_run: true, sleep_time: nil)
+        relation = Upload.where('lower(path) like ? or lower(path) like ? or lower(path) like ?',
+                                '%.jpg', '%.jpeg', '%.tiff')
+
+        logger.info "running in dry run mode, no images will be rewritten" if dry_run
+
+        find_params = {
+          start: start_id.present? ? start_id.to_i : nil,
+          finish: stop_id.present? ? stop_id.to_i : Upload.last&.id
+        }
+
+        relation.find_each(find_params) do |upload|
+          clean(upload.build_uploader, dry_run: dry_run)
+          sleep sleep_time if sleep_time
+        rescue => err
+          logger.error "failed to sanitize #{upload_ref(upload)}: #{err.message}"
+          logger.debug err.backtrace.join("\n ")
+        end
+      end
+      # rubocop: enable CodeReuse/ActiveRecord
+
+      def clean(uploader, dry_run: true)
+        Dir.mktmpdir('gitlab-exif') do |tmpdir|
+          src_path = fetch_upload_to_file(uploader, tmpdir)
+
+          to_remove = extra_tags(src_path)
+
+          if to_remove.empty?
+            logger.info "#{upload_ref(uploader.upload)}: only whitelisted tags present, skipping"
+            break
+          end
+
+          logger.info "#{upload_ref(uploader.upload)}: found exif tags to remove: #{to_remove}"
+
+          break if dry_run
+
+          remove_and_store(tmpdir, src_path, uploader)
+        end
+      end
+
+      def extra_tags(path)
+        exif_tags(path).keys - ALLOWED_TAGS
+      end
+
+      private
+
+      def remove_and_store(tmpdir, src_path, uploader)
+        exec_remove_exif!(src_path)
+        logger.info "#{upload_ref(uploader.upload)}: exif removed, storing"
+        File.open(src_path, 'r') { |f| uploader.store!(f) }
+      end
+
+      def exec_remove_exif!(path)
+        # IPTC and XMP-iptcExt groups may keep copyright information so
+        # we always preserve them
+        cmd = ["exiftool", "-all=", "-tagsFromFile", "@", *EXCLUDE_PARAMS, "--IPTC:all", "--XMP-iptcExt:all", path]
+        output, status = Gitlab::Popen.popen(cmd)
+
+        if status != 0
+          raise "exiftool return code is #{status}: #{output}"
+        end
+
+        if File.size(path) == 0
+          raise "size of file is 0"
+        end
+
+        # exiftool creates backup of the original file in filename_original
+        old_path = "#{path}_original"
+        if File.size(path) == File.size(old_path)
+          raise "size of sanitized file is same as original size"
+        end
+      end
+
+      def fetch_upload_to_file(uploader, dir)
+        # upload is stored into the file with the original name - this filename
+        # is used by carrierwave when storing the file back to the storage
+        filename = File.join(dir, uploader.filename)
+
+        File.open(filename, 'w') do |file|
+          file.binmode
+          file.write uploader.read
+        end
+
+        filename
+      end
+
+      def upload_ref(upload)
+        "#{upload.id}:#{upload.path}"
+      end
+
+      def exif_tags(path)
+        cmd = ["exiftool", "-all", "-j", "-sort", "--IPTC:all", "--XMP-iptcExt:all", path]
+        output, status = Gitlab::Popen.popen(cmd)
+
+        raise "failed to get exif tags: #{output}" if status != 0
+
+        JSON.parse(output).first
+      end
+    end
+  end
+end