[FFmpeg-devel] [PATCH] avcodec/rscc: Avoid returning frames that have nearly no undamaged pixels in them

[Derek Buitenhuis]

On 17/01/2019 23:33, Michael Niedermayer wrote:
> Would you be ok with rejecting RSCC files without a keyframe ?
> or more precissely all frames before a keyframe and thus if there is
> no keyframe the whole file
> (that would be a superset of what this patch rejects)

This, to me, soundsp preferable, if hidden under ER being disable or something.

> 
> I suggested that arbitrary check above as it would allow decoding more data
> in case of a damaged or lost keyframe

[...]

> The gain these changes have is they increase the cost for an
> attacker in a DOS attack. (they also improve the efficiency of the fuzzer but
> thats secondary)

By this logic, every single optimization is an anti-DoS measure and can
be argued ad nauseam in favor of every such changed, regardless of cost.

> As is you can have a file with huge resolution where each frame only encodes
> 1 pixel in about a dozen bytes per frame. That transforms a very low cost of
> network bandwidth from an attacker to a rather large computational cost on
> anything processing such file.

You don't need to explain what a DoS is to us...

> Requiring more than 1 valid pixels in a billion or Requiring a valid keyframe
> would increase the cost for an attacker.

This is not codec specific, either.

> Also do you see a cleaner way to achive this as the author of this
> decoder ?

People are disagreeing with the premise, not the implementation.

- Derek