[poppler] Bug in JBIG2Stream

[Albert Astals Cid]

A Dijous, 11 de juny de 2009, Albert Astals Cid va escriure:
> A Dimecres, 10 de juny de 2009, David Benjamin va escriure:
> > On further consideration, I believe getPos() is the wrong function to
> > call (and is implemented wrong anyway). I believe the newly attached
> > patch is more correct.
> >
> > (Although, it doesn't look like JBIG2Stream::getPos is ever called
> > anyway.)
> >
> > I'm not sure why it bothers to subclass FilterStream though.
>
> Seems okaish, let me pass it trough the regression testing (3 or 4 days not
> counting the weekend) to see if it fixes/breaks other pdf.
>
> Thanks for the contribution :-)

Commited.

Albert

>
> Albert
>
> > David Benjamin
> >
> > On 06/07/2009 08:46 PM, David Benjamin wrote:
> > > So, I've been tracking down a bug in JBIG2Stream. It fails to render
> > > PDFs at [1] (second column) by misdetecting segments of incorrect
> > > length (and then eats up useful bytes at line 1445). JBIG2Stream
> > > appears to bypass FilterStream::str and uses it's own curStr[2], so
> > > getPos() is wrong at the beginning.
> > >
> > > Attached is a (trivial) patch to fix this. I'm not entirely sure if
> > > this is the "correct" thing to do here; the current setup feels pretty
> > > iffy anyway, but I get the feeling getPos() should not suddenly jump in
> > > the middle of a stream? I don't really know poppler's code, so I'm not
> > > sure what guarantees are Stream/FilterStream supposed to provide to
> > > users or if they're exported API in the first place.
> > >
> > > (At least internally in JBIG2Stream the only non-error-reporting use of
> > > getPos is the segment-length-detection bit.)
> > >
> > > [1] http://www.adobe.com/products/acrcapture/agentpack/index.html
> > >
> > > [2] It seems to want to swap the stream out temporarily at reset()...
> > > I'm not sure why; I'm unfamiliar with JBIG2.
>
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