A Dijous 11 Gener 2007 16:33, Kristian Høgsberg va escriure: > On 1/11/07, Jeff Muizelaar <[EMAIL PROTECTED]> 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 _______________________________________________ poppler mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/poppler
