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Excellent! This ought to be the top comment; have you submitted it separately? I was considering implemented the same thing, since there wasn't any reason for t

Excellent! This ought to be the top comment; have you submitted it separately? I was considering implemented the same thing, since there wasn't any reason for those limitations. The Google researchers purposely designed this collision to be highly reusable, probably to encourage everyone to generate lots of fun examples which will be spread widely and break systems everywhere :) I'm surprised that some PDF renderers have problems with JPEG streams that contain comments and restarts. Actually, glancing at the JPEG spec, I didn't even realise that restarts would be needed, I thought this was just done with comments. Is this really "bending" the spec, or is GhostScript buggy, or is the problem that it's assuming that restarts don't occur inside comments without escaping?

nneonneo 10y ago
I did submit it, but I don't think anyone saw it: https://news.ycombinator.com/item?id=13729920 https://news.ycombinator.com/item?id=13729920. I was trying to finish it in time to catch daytime folks but work got in the way :) Comments are limited to 65536 bytes, and the JPEG spec doesn't offer any way to break an image stream up except for progressive mode or restart intervals (otherwise, the image stream must be a single intact entity). The trouble is that it's probably not _technically_ legal to stick comments before restart interval markers (putting comments _after_ the markers just breaks all the readers since presumably they are expecting image data). So, GhostScript's JPEG reader gets confused when it fails to see a restart marker immediately following an image data chunk, and aborts decoding.