Imager::Security(3) brief notes on security and image processing


# keep abreast of security updates
apt-get update && apt-get upgrade
yum upgrade
pkgin update && pkgin upgrade
# or local equivalent
# limit memory use
use Imager;
# only images that use up to 10MB
Imager->set_file_limits(bytes => 10_000_000);


There's two basic security considerations when dealing with images from an unknown source:
  • keeping your libraries up to date
  • limiting the amount of memory used to store images

Keeping libraries up to date

Image file format libraries such as "libpng" or "libtiff" have relatively frequent security updates, keeping your libraries up to date is basic security.

If you're using user supplied fonts, you will need to keep your font libraries up to date too.

Limiting memory used

With compression, and especially with pointer formats like TIFF, it's possible to store very large images in a relatively small file.

If you're receiving image data from an untrusted source you should limit the amount of memory that Imager can allocate for a read in image file using the "set_file_limits()" method.

  Imager->set_file_limits(bytes => 10_000_000);

You may also want to limit the maximum width and height of images read from files:

  Imager->set_file_limits(width => 10_000, height => 10_000,
                          bytes => 10_000_000);

This has no effect on images created without a file:

  # succeeds
  my $image = Imager->new(xsize => 10_001, ysize => 10_001);

You can reset to the defaults with:

  Imager->set_file_limits(reset => 1);


Tony Cook <[email protected]>