Re: Heapoverflow in giflib5.1.4

[Seth Arnold <seth.arnold () canonical com>]

On Tue, Sep 13, 2016 at 09:53:03PM +0200, Hanno Böck wrote:
> I can however easily generate another sample that causes the same bug.
> See attachment.

This attachment does indeed trigger ASAN here, too:

ubuntu@x1:~/giflib-code$ util/gif2rgb gif2rgb-oob-new.gif 
=================================================================
==5394==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000efdc at pc 0x000000402b8b bp 0x7ffdafbd60f0 
sp 0x7ffdafbd60e0
READ of size 1 at 0x60200000efdc thread T0
    #0 0x402b8a in DumpScreen2RGB /home/ubuntu/giflib-code/util/gif2rgb.c:294
    #1 0x4045a8 in GIF2RGB /home/ubuntu/giflib-code/util/gif2rgb.c:480
    #2 0x404af0 in main /home/ubuntu/giflib-code/util/gif2rgb.c:531
    #3 0x7f2a7693682f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #4 0x4015c8 in _start (/home/ubuntu/giflib-code/util/.libs/lt-gif2rgb+0x4015c8)

0x60200000efdc is located 0 bytes to the right of 12-byte region [0x60200000efd0,0x60200000efdc)
allocated by thread T0 here:
    #0 0x7f2a76f9179a in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x9879a)
    #1 0x7f2a76cf0e55 in GifMakeMapObject /home/ubuntu/giflib-code/lib/gifalloc.c:55
    #2 0x7f2a76ce3179 in DGifGetScreenDesc /home/ubuntu/giflib-code/lib/dgif_lib.c:268
    #3 0x7f2a76ce2412 in DGifOpenFileHandle /home/ubuntu/giflib-code/lib/dgif_lib.c:140
    #4 0x7f2a76ce1dde in DGifOpenFileName /home/ubuntu/giflib-code/lib/dgif_lib.c:61
    #5 0x4034f3 in GIF2RGB /home/ubuntu/giflib-code/util/gif2rgb.c:356
    #6 0x404af0 in main /home/ubuntu/giflib-code/util/gif2rgb.c:531
    #7 0x7f2a7693682f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/ubuntu/giflib-code/util/gif2rgb.c:294 DumpScreen2RGB
Shadow bytes around the buggy address:
  0x0c047fff9da0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9db0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9dc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9dd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9de0: fa fa fa fa fa fa fa fa fa fa 06 fa fa fa 02 fa
=>0x0c047fff9df0: fa fa 02 fa fa fa 00 00 fa fa 00[04]fa fa 03 fa
  0x0c047fff9e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9e10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9e20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9e30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff9e40: 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 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
==5394==ABORTING


Thanks Hanno

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