2008.06.20 17:19 "Re: [Tiff] Scalability problem in tif_dirread.c - detecting loops in IFD offsets", by Andrey Kiselev

On Fri, Jun 20, 2008 at 08:02:32AM -0400, Steve Eddins wrote:

Thanks very much for your helpful responses. Interesting that such files really exist.

You can easily create such a file yourself using you favorite binary editor. With that file you can make a DOS attack on any TIFF software that is not aware of IFD looping problem. These days we should always double check the input data and we can trust no one.

Turning to code I should say that I always wanted to rewrite it and make a single scan over the file when opening and use resulting table later. Current TIFFSetDirectory() and TIFFNumberOfDirectories() implementations are not efficient for heavily multi-paged TIFFs, the IFD offset table can be used here. But be aware of in-place TIFF modifications, that table should be properly updated too.

If you will decide to contribute a patch for this stuff, please, do it against the 4.0 branch. That is too much for 3.9 which is considered to be a stable branch.

Best regards,

Andrey

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Andrey V. Kiselev
ICQ# 26871517