imageworsener: heap-based buffer overflow in iw_process_cols_to_intermediate (imagew-main.c)

["Agostino Sarubbo" <ago () gentoo org>]

Description:
imageworsener is a utility for image scaling and processing.

The complete ASan output of the issue:

# imagew $FILE /tmp/out -outfmt bmp
==20314==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7fe233b99af8 at pc 0x7fea7f55da64 bp 0x7ffdb4737840 
sp 0x7ffdb4737838
WRITE of size 4 at 0x7fe233b99af8 thread T0  
    #0 0x7fea7f55da63 in iw_process_cols_to_intermediate 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-main.c:903:75 
    #1 0x7fea7f55da63 in iw_process_one_channel 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-main.c:1144  
    #2 0x7fea7f54ca71 in iw_process_internal 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-main.c:1405:7   
    #3 0x7fea7f520095 in iw_process_image 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-main.c:2248:8 
    #4 0x528de1 in iwcmd_run /tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-cmd.c:1400:6
    #5 0x515326 in iwcmd_main 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-cmd.c:3018:7    
    #6 0x515326 in main /tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-cmd.c:3067  
    #7 0x7fea7e5e878f in __libc_start_main 
/tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289   
    #8 0x41b028 in _init (/usr/bin/imagew+0x41b028)    

0x7fe233b99af8 is located 4 bytes to the right of 8003134196-byte region [0x7fe056b37800,0x7fe233b99af4) 
allocated by thread T0 here:  
    #0 0x4da6f8 in malloc 
/tmp/portage/sys-libs/compiler-rt-sanitizers-4.0.0/work/compiler-rt-4.0.0.src/lib/asan/asan_malloc_linux.cc:66    
    #1 0x551fc0 in my_mallocfn 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-cmd.c:794:9    
    #2 0x7fea7f6a39ae in iw_malloc_ex 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-util.c:48:8  
    #3 0x7fea7f6a3dec in iw_malloc_large 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-util.c:77:9    
    #4 0x7fea7f54c5a0 in iw_process_internal 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-main.c:1396:44  
    #5 0x7fea7f520095 in iw_process_image 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-main.c:2248:8 
    #6 0x528de1 in iwcmd_run /tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-cmd.c:1400:6
    #7 0x515326 in iwcmd_main 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-cmd.c:3018:7    
    #8 0x515326 in main /tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-cmd.c:3067  
    #9 0x7fea7e5e878f in __libc_start_main 
/tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289

SUMMARY: AddressSanitizer: heap-buffer-overflow 
/tmp/portage/media-gfx/imageworsener-1.3.0/work/imageworsener-1.3.0/src/imagew-main.c:903:75 in 
iw_process_cols_to_intermediate
Shadow bytes around the buggy address:
  0x0ffcc676b300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffcc676b310: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffcc676b320: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffcc676b330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0ffcc676b340: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0ffcc676b350: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 04[fa]
  0x0ffcc676b360: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ffcc676b370: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ffcc676b380: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ffcc676b390: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ffcc676b3a0: 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
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  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
==20314==ABORTING

Affected version:
1.3.0

Fixed version:
1.3.1

Commit fix:
https://github.com/jsummers/imageworsener/commit/86564051db45b466e5f667111ce00b5eeedc8fb6

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

CVE:
CVE-2017-8325

Reproducer:
https://github.com/asarubbo/poc/blob/master/00269-imageworsener-heapoverflow-iw_process_cols_to_intermediate

Timeline:
2017-04-12: bug discovered and reported to upstream
2017-04-12: upstream released a patch
2017-04-27: blog post about the issue
2017-04-29: CVE assigned

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/04/27/imageworsener-heap-based-buffer-overflow-in-iw_process_cols_to_intermediate-imagew-main-c/

--
Agostino Sarubbo
Gentoo Linux Developer