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Date: Wed, 15 Jun 2016 02:37:11 +0000
From: 张开翔 <zhangkaixiang@....cn>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Subject: CVE-2016-5323: libtiff 4.0.6 tiffcrop _TIFFFax3fillruns(): divide
 by zero

Details
=======

Product: libtiff
Affected Versions: <= 4.0.6
Vulnerability Type: divide by zero
Vendor URL: http://www.remotesensing.org/libtiff/
Credit: Kaixiang Zhang of the Cloud Security Team, Qihoo 360
CVE ID: CVE-2016-5323
Tested system version:
       fedora23 32bit
       fedora23 64bit
       CentOS Linux release 7.1.1503 64bit

Introduction
=======

t was always corrupted when I use tiffcrop command followed by a crafted TIFF image in function _TIFFFax3fillruns () without checking the value of divisor, it causes a divide by zero flaw. Attackers cound exploit this issue to cause denial-of-service.

Here is the stack info:
gdb –args ./tiffcrop _TIFFFax3fillruns.tif tmpout.tif
--- ---
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7ad97f0 in _TIFFFax3fillruns (buf=0x0, runs=0x673500, erun=<optimized out>, lastx=64) at tif_fax3.c:407
407                              ZERO(n, cp);
(gdb) bt
#0  0x00007ffff7ad97f0 in _TIFFFax3fillruns (buf=0x0, runs=0x673500, erun=<optimized out>, lastx=64) at tif_fax3.c:407
#1  0x00007ffff7ae087c in Fax3DecodeRLE (tif=0x662010, buf=0x0, occ=8192, s=<optimized out>) at tif_fax3.c:1527
#2  0x00007ffff7ba3739 in TIFFReadEncodedTile (tif=tif@...ry=0x662010, tile=8, buf=0x0, size=8192, size@...ry=-1) at tif_read.c:668
#3  0x00007ffff7ba3a01 in TIFFReadTile (tif=tif@...ry=0x662010, buf=<optimized out>, x=x@...ry=0, y=y@...ry=0, z=z@...ry=0, s=s@...ry=8) at tif_read.c:641
#4  0x0000000000443e41 in readSeparateTilesIntoBuffer (bps=1, spp=129, tl=1024, tw=64, imagewidth=32, imagelength=32, obuf=0x7ffff7ee5010 "", in=0x662010) at tiffcrop.c:994
#5  loadImage (in=in@...ry=0x662010, image=image@...ry=0x7fffffff7960, dump=dump@...ry=0x7fffffffc270, read_ptr=read_ptr@...ry=0x7fffffff7920) at tiffcrop.c:6079
#6  0x0000000000403209 in main (argc=<optimized out>, argv=<optimized out>) at tiffcrop.c:2278
(gdb) p cp
$2 = (unsigned char *) 0x0


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