Date: Wed, 26 Sep 2012 12:32:42 +0530 From: Huzaifa Sidhpurwala <huzaifas@...hat.com> To: Sebastian Krahmer <krahmer@...e.de> CC: oss-security@...ts.openwall.com, Tom Lane <tgl@...hat.com> Subject: Re: CVE Request: libtiff: Heap-buffer overflow when processing a TIFF image with PixarLog Compression On 09/26/2012 12:27 PM, Sebastian Krahmer wrote: > > This conclusion leaves me a bit puzzled. :) Even just "a few bytes" are > often enough to trigger code exec. In particular if you get a big bounty for it. > Sure :) > As well as the patch: > > > - sp->tbuf = (uint16 *) _TIFFmalloc(tbuf_size); > + sp->tbuf = (uint16 *) _TIFFmalloc(tbuf_size+sizeof(uint16)*sp->stride); > > If there were sizeof(uint16)*sp->stride bytes missing before, this is really > more than just a few bytes. I checked that the mult cannot overflow, > as sp->stride seems to be uint16. However, I think the add can actually wrap, > (at least on ILP32) as tbuf_size can be 0xffffffff or so. > I think the patch is broken and just shifts the hole. > It seems that sp->stride is at most td_samplesperpixel. Re-thinking about the patch, it does seem a bit broken now. Tom, Any inputs on this? > Plus, there are more occurences of _TIFFmalloc(tbuf_size) inside this file, > one in PixarLogSetupEncode() and one in PixarLogSetupDecode() (but it might be > that the Encode can never be triggered like so by attackers). > > Sebastian > -- Huzaifa Sidhpurwala / Red Hat Security Response Team
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