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Date: Sun, 01 Jan 2017 16:52:34 +0100
From: Agostino Sarubbo <ago@...too.org>
To: oss-security@...ts.openwall.com
Subject: libtiff: stack-based buffer overflow in _TIFFVGetField (tif_dir.c)

Description:
Libtiff is a software that provides support for the Tag Image File Format 
(TIFF), a widely used format for storing image data.

A crafted tiff file revealed a stack buffer overflow.

The complete ASan output:

# tiffsplit $FILE
TIFFReadDirectory: Warning, Unknown field with tag 317 (0x13d) encountered.
=================================================================
==10362==ERROR: AddressSanitizer: stack-buffer-overflow on address 
0x7f3824f00090 at pc 0x7f3829624fbb bp 0x7fffe0eb1da0 sp 0x7fffe0eb1d98
WRITE of size 4 at 0x7f3824f00090 thread T0
    #0 0x7f3829624fba in _TIFFVGetField /tmp/portage/media-
libs/tiff-4.0.7/work/tiff-4.0.7/libtiff/tif_dir.c:1077:29
    #1 0x7f382960f202 in TIFFVGetField /tmp/portage/media-
libs/tiff-4.0.7/work/tiff-4.0.7/libtiff/tif_dir.c:1198:6
    #2 0x7f382960f202 in TIFFGetField /tmp/portage/media-
libs/tiff-4.0.7/work/tiff-4.0.7/libtiff/tif_dir.c:1182
    #3 0x50a719 in tiffcp /tmp/portage/media-
libs/tiff-4.0.7/work/tiff-4.0.7/tools/tiffsplit.c:183:2
    #4 0x50a719 in main /tmp/portage/media-
libs/tiff-4.0.7/work/tiff-4.0.7/tools/tiffsplit.c:89
    #5 0x7f382871561f in __libc_start_main /var/tmp/portage/sys-
libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289
    #6 0x419a78 in _init (/usr/bin/tiffsplit+0x419a78)

Address 0x7f3824f00090 is located in stack of thread T0 at offset 144 in frame
    #0 0x5099cf in main /tmp/portage/media-
libs/tiff-4.0.7/work/tiff-4.0.7/tools/tiffsplit.c:59

  This frame has 18 object(s):
    [32, 40) 'bytecounts.i263.i'
    [64, 72) 'bytecounts.i.i'
    [96, 98) 'bitspersample.i'
    [112, 114) 'samplesperpixel.i'
    [128, 130) 'compression.i'
    [144, 146) 'shortv.i' 0x0fe7849d8010: 02 f2[02]f2 00 f2 f2 f2 04 f2 04 f2 
04 f2 00 f2
  0x0fe7849d8020: f2 f2 04 f2 04 f2 00 f2 f2 f2 00 f2 f2 f2 00 f2
  0x0fe7849d8030: f2 f2 00 f2 f2 f2 02 f3 00 00 00 00 00 00 00 00
  0x0fe7849d8040: f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5
  0x0fe7849d8050: f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5
  0x0fe7849d8060: f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5 f5
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 right 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
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==10362==ABORTING

Affected version:
4.0.7

Fixed version:
N/A

Commit fix:
N/A

Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.

CVE:
N/A

Reproducer:
https://github.com/asarubbo/poc/blob/master/00104-libtiff-stackoverflow-_TIFFVGetField

Timeline:
2016-12-04: bug discovered and reported to upstream
2017-01-01: blog post about the issue

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/01/01/libtiff-stack-based-buffer-overflow-in-_tiffvgetfield-tif_dir-c

-- 
Agostino Sarubbo
Gentoo Linux Developer

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