Re: [Tuxpaint-devel] [PATCH 2/2] Check for PNG valid image before reading metadata

[Albert C. <aca...@gm...>]

I don't think this is good. If we have to handle bad images,
then we have to handle bad images that happen to have a
fully normal 8-byte PNG signature. Thus, checking the
signature is extra code that we don't need.

If this is a code path that realistically could need to deal
with untrusted image data, then effort should be focused
on what happens when we actually try to process the image.
Otherwise, it's an error that won't happen.

Note that printing to stderr is not an appropriate way to
handle any error that a kid could realistically encounter.
Normal users will not see stderr at all, ever.