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Date: Thu, 7 Apr 2016 07:39:43 +0000
From: 王梅 <wangmei@....cn>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Subject: CVE-2016-3621 libtiff: Out-of-bounds Read in the bmp2tiff tool

Details
=======

Product: libtiff
Affected Versions: <= 4.0.6
Vulnerability Type: Out-of-bounds Read
Vendor URL: http://www.libtiff.org/
CVE ID: CVE-2016-3621
Credit: Mei Wang of the Cloud Security Team, Qihoo 360

Introduction
============

LZWEncode function in tif_lzw.c in bmp2tiff allows attackers to cause a denial of service (Out-of-bounds Read) via a crafted bmp image with param -c lzw.


libtiff-master/libtiff/tif_lzw.c:915

910  */
911 PutNextCode(op, CODE_CLEAR);
912 ent = *bp++; cc--; incount++;
913 }
914 while (cc > 0) {
915 c = *bp++; cc--; incount++;
916 fcode = ((long)c << BITS_MAX) + ent;
917 h = (c << HSHIFT) ^ ent; /* xor hashing */


./bmp2tiff  -c lzw  ./sample/bmp2tiff_lzw.bmp 1.tif

=================================================================
==10455== ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7fbcd06d1c00 at pc 0x4827aa bp 0x7ffef81741d0 sp 0x7ffef81741c0
READ of size 1 at 0x7fbcd06d1c00 thread T0
    #0 0x4827a9 in LZWEncode /home/dazhuang/asan/libtiff-master/libtiff/tif_lzw.c:915
    #1 0x45665e in TIFFWriteScanline /home/dazhuang/asan/libtiff-master/libtiff/tif_write.c:173
    #2 0x40450f in main /home/dazhuang/asan/libtiff-master/tools/bmp2tiff.c:775
    #3 0x7fbcccc92af4 in __libc_start_main (/lib64/libc.so.6+0x21af4)
    #4 0x4019a8 in _start (/home/dazhuang/asan/libtiff-master/tools/bmp2tiff+0x4019a8)
0x7fbcd06d1c00 is located 0 bytes to the right of 1573888-byte region [0x7fbcd0551800,0x7fbcd06d1c00)
allocated by thread T0 here:
    #0 0x7fbccd563129 (/lib64/libasan.so.0+0x16129)
    #1 0x45b761 in _TIFFmalloc /home/dazhuang/asan/libtiff-master/libtiff/tif_unix.c:316
    #2 0x4037c3 in main /home/dazhuang/asan/libtiff-master/tools/bmp2tiff.c:678
    #3 0x7fbcccc92af4 in __libc_start_main (/lib64/libc.so.6+0x21af4)
SUMMARY: AddressSanitizer: heap-buffer-overflow /home/dazhuang/asan/libtiff-master/libtiff/tif_lzw.c:915 LZWEncode
Shadow bytes around the buggy address:
  0x0ff81a0d2330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff81a0d2340: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff81a0d2350: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff81a0d2360: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ff81a0d2370: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0ff81a0d2380:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff81a0d2390: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff81a0d23a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff81a0d23b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff81a0d23c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff81a0d23d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:     fa
  Heap righ redzone:     fb
  Freed Heap region:     fd
  Stack left redzone:    f1
  Stack mid redzone:     f2
  Stack right redzone:   f3
  Stack partial redzone: f4
  Stack after return:    f5
  Stack use after scope: f8
  Global redzone:        f9
  Global init order:     f6
  Poisoned by user:      f7
  ASan internal:         fe
==10455== ABORTING

References:
[1] http://www.remotesensing.org/libtiff/
[2] http://bugzilla.maptools.org/buglist.cgi?product=libtiff


Thank you!
Best Regards,


Mei

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