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June 2008

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2008.06.19 21:34 "Scalability problem in tif_dirread.c - detecting loops in IFD offsets", by Steve Eddins
2008.06.19 22:04 "Re: Scalability problem in tif_dirread.c - detecting loops in IFD offsets", by Frank Warmerdam
2008.06.20 12:02 "Re: Scalability problem in tif_dirread.c - detecting loops in IFD offsets", by Steve Eddins
2008.06.20 13:38 "Re: Scalability problem in tif_dirread.c - detecting loops in IFD offsets", by Bob Friesenhahn
2008.06.20 17:19 "Re: Scalability problem in tif_dirread.c - detecting loops in IFD offsets", by Andrey Kiselev
2008.06.20 18:19 "Re: Scalability problem in tif_dirread.c - detecting loops in IFD offsets", by Edward Lam
2008.06.22 17:15 "Re: Scalability problem in tif_dirread.c - detecting loops in IFD offsets", by Steve Eddins

2008.06.20 17:19 "Re: 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


-- 
Andrey V. Kiselev
ICQ# 26871517