[poppler] Poppler and MOAB-06-01-2007

[Albert Astals Cid]

A Dijous 11 Gener 2007 16:33, Kristian Høgsberg va escriure:
> On 1/11/07, Jeff Muizelaar <jeff at infidigm.net> wrote:
> > On Thu, Jan 11, 2007 at 08:45:48AM -0500, Kristian Høgsberg wrote:
>
> ...
>
> > > And the problem in this case is how to prevent looping when we have
> > > circular references in the page tree.  To prevent this we can do two
> > > things: the one idea that Albert doesn't like is to just limit the
> > > depth of the page tree.  We can either choose a fixed limit or use the
> > > total number of references as a limit.  If there is a page tree chain
> > > longer than, say, 1000, the document is most certainly malicious.  On
> > > the other hand, we can easily handle a recusion level of 1000, so we
> > > can detect it and bail out safely in that case.
> > >
> > > The other idea is to just put a 'visited' bit in each node of the page
> > > tree.  If wee see a page that already has the 'visited' bit set we
> > > know something is wrong and we can bail out right away.
> >
> > I looked at this idea first. However, I didn't see how it could fit
> > easily with the exisiting code structure. The solution I came with is to
> > have a bitmap of size XRef->size(), then for each object we visit mark
> > the bit corresponding to that object. If the bit is already set we know
> > that we have a loop in the tree.
>
> But why not just limit the recursion depth to XRef->size() calls?

I agree with Jeff, that sounds like a non crapy and easy solution.

Albert

>
> Kristian