A heap-based-buffer-over-read flaw was found in ImageMagick's GetPixelAlpha() function of 'pixel-accessor.h'. This vulnerability is triggered when an attacker passes a specially crafted Tagged Image File Format (TIFF) image to convert it into a PICON file format. This issue can potentially lead to a denial of service and information disclosure.
### ImageMagick version

7.1.0-20

### Operating system

Linux

### Operating system, version and so on

Linux ubuntu 5.4.0-73-generic #82~18.04.1-Ubuntu SMP Fri Apr 16 15:10:02 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

### Description

Hi, ImageMagick security team
This is ZhangJiaxing (@r0fm1a) from Codesafe Team of Legendsec at Qi'anxin Group.
I've found a Heap Buffer Overflow vulnerability in ImageMagick 7.1.0-20.(github commit  ID f54aa4e7ba8a8fb82d200844dc59804f5f6c8cbf in Tue Jan 18 20:00:38 2022 -0500).When someone uses magick to convert a tiff-format image into a picon-format file, the bug will be traggered on.
Please feel free to contact me.
Regards,
ZhangJiaxing

### Steps to Reproduce

1. git clone ImageMagick
2. ./configure CC=gcc CFLAGS="-g -fsanitize=address" && make
3. cd utilities &&./magick convert /path/to/poc.tiff output.picon
4. The Asan logs are as follows:
==46632==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x62a00000b540 at pc 0x7f7e88ca3257 bp 0x7fffdb9f7370 sp 0x7fffdb9f7360
READ of size 4 at 0x62a00000b540 thread T0
    #0 0x7f7e88ca3256 in GetPixelAlpha MagickCore/pixel-accessor.h:59
    #1 0x7f7e88ca763e in WritePICONImage coders/xpm.c:807
    #2 0x7f7e885f73ef in WriteImage MagickCore/constitute.c:1221
    #3 0x7f7e885f84a0 in WriteImages MagickCore/constitute.c:1442
    #4 0x7f7e87e5239f in ConvertImageCommand MagickWand/convert.c:3332
    #5 0x7f7e87f604cf in MagickCommandGenesis MagickWand/mogrify.c:188
    #6 0x55a7a3ebefcf in MagickMain utilities/magick.c:150
    #7 0x55a7a3ebf25a in main utilities/magick.c:182
    #8 0x7f7e876c2bf6 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)
    #9 0x55a7a3ebe9e9 in _start (/home/r0fm1a/ImageMagick/utilities/.libs/magick+0x19e9)

0x62a00000b540 is located 0 bytes to the right of 21312-byte region [0x62a000006200,0x62a00000b540)
allocated by thread T0 here:
    #0 0x7f7e893e3790 in posix_memalign (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xdf790)
    #1 0x7f7e887d1c99 in AcquireAlignedMemory_POSIX MagickCore/memory.c:299
    #2 0x7f7e887d1ea8 in AcquireAlignedMemory MagickCore/memory.c:377
    #3 0x7f7e88582e0e in OpenPixelCache MagickCore/cache.c:3746
    #4 0x7f7e8857b296 in GetImagePixelCache MagickCore/cache.c:1776
    #5 0x7f7e8858b2de in SyncImagePixelCache MagickCore/cache.c:5516
    #6 0x7f7e88798568 in SetImageStorageClass MagickCore/image.c:2626
    #7 0x7f7e885ab718 in AcquireImageColormap MagickCore/colormap.c:152
    #8 0x7f7e888731cd in SetGrayscaleImage MagickCore/quantize.c:3772
    #9 0x7f7e888714e7 in QuantizeImage MagickCore/quantize.c:3118
    #10 0x7f7e88866f5d in CompressImageColormap MagickCore/quantize.c:1204
    #11 0x7f7e88ca6f6a in WritePICONImage coders/xpm.c:755
    #12 0x7f7e885f73ef in WriteImage MagickCore/constitute.c:1221
    #13 0x7f7e885f84a0 in WriteImages MagickCore/constitute.c:1442
    #14 0x7f7e87e5239f in ConvertImageCommand MagickWand/convert.c:3332
    #15 0x7f7e87f604cf in MagickCommandGenesis MagickWand/mogrify.c:188
    #16 0x55a7a3ebefcf in MagickMain utilities/magick.c:150
    #17 0x55a7a3ebf25a in main utilities/magick.c:182
    #18 0x7f7e876c2bf6 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)

SUMMARY: AddressSanitizer: heap-buffer-overflow MagickCore/pixel-accessor.h:59 in GetPixelAlpha
Shadow bytes around the buggy address:
  0x0c547fff9650: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c547fff9660: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c547fff9670: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c547fff9680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c547fff9690: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c547fff96a0: 00 00 00 00 00 00 00 00[fa]fa fa fa fa fa fa fa
  0x0c547fff96b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c547fff96c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c547fff96d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c547fff96e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c547fff96f0: 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
==46632==ABORTING


### Images

[magick_heap_bof.zip](https://github.com/ImageMagick/ImageMagick/files/7894812/magick_heap_bof.zip)

Heap Buffer Overflow 
This is a GitHub Issue
repo:ImageMagick
owner:ImageMagick
Title : Heap Buffer Overflow 
Issue date:

--- start body ---
### ImageMagick version

7.1.0-20

### Operating system

Linux

### Operating system, version and so on

Linux ubuntu 5.4.0-73-generic #82~18.04.1-Ubuntu SMP Fri Apr 16 15:10:02 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

### Description

Hi, ImageMagick security team
This is ZhangJiaxing (@r0fm1a) from Codesafe Team of Legendsec at Qi'anxin Group.
I've found a Heap Buffer Overflow vulnerability in ImageMagick 7.1.0-20.(github commit  ID f54aa4e7ba8a8fb82d200844dc59804f5f6c8cbf in Tue Jan 18 20:00:38 2022 -0500).When someone uses magick to convert a tiff-format image into a picon-format file, the bug will be traggered on.
Please feel free to contact me.
Regards,
ZhangJiaxing

### Steps to Reproduce

1. git clone ImageMagick
2. ./configure CC=gcc CFLAGS="-g -fsanitize=address" && make
3. cd utilities &&./magick convert /path/to/poc.tiff output.picon
4. The Asan logs are as follows:
==46632==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x62a00000b540 at pc 0x7f7e88ca3257 bp 0x7fffdb9f7370 sp 0x7fffdb9f7360
READ of size 4 at 0x62a00000b540 thread T0
    #0 0x7f7e88ca3256 in GetPixelAlpha MagickCore/pixel-accessor.h:59
    #1 0x7f7e88ca763e in WritePICONImage coders/xpm.c:807
    #2 0x7f7e885f73ef in WriteImage MagickCore/constitute.c:1221
    #3 0x7f7e885f84a0 in WriteImages MagickCore/constitute.c:1442
    #4 0x7f7e87e5239f in ConvertImageCommand MagickWand/convert.c:3332
    #5 0x7f7e87f604cf in MagickCommandGenesis MagickWand/mogrify.c:188
    #6 0x55a7a3ebefcf in MagickMain utilities/magick.c:150
    #7 0x55a7a3ebf25a in main utilities/magick.c:182
    #8 0x7f7e876c2bf6 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)
    #9 0x55a7a3ebe9e9 in _start (/home/r0fm1a/ImageMagick/utilities/.libs/magick+0x19e9)

0x62a00000b540 is located 0 bytes to the right of 21312-byte region [0x62a000006200,0x62a00000b540)
allocated by thread T0 here:
    #0 0x7f7e893e3790 in posix_memalign (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xdf790)
    #1 0x7f7e887d1c99 in AcquireAlignedMemory_POSIX MagickCore/memory.c:299
    #2 0x7f7e887d1ea8 in AcquireAlignedMemory MagickCore/memory.c:377
    #3 0x7f7e88582e0e in OpenPixelCache MagickCore/cache.c:3746
    #4 0x7f7e8857b296 in GetImagePixelCache MagickCore/cache.c:1776
    #5 0x7f7e8858b2de in SyncImagePixelCache MagickCore/cache.c:5516
    #6 0x7f7e88798568 in SetImageStorageClass MagickCore/image.c:2626
    #7 0x7f7e885ab718 in AcquireImageColormap MagickCore/colormap.c:152
    #8 0x7f7e888731cd in SetGrayscaleImage MagickCore/quantize.c:3772
    #9 0x7f7e888714e7 in QuantizeImage MagickCore/quantize.c:3118
    #10 0x7f7e88866f5d in CompressImageColormap MagickCore/quantize.c:1204
    #11 0x7f7e88ca6f6a in WritePICONImage coders/xpm.c:755
    #12 0x7f7e885f73ef in WriteImage MagickCore/constitute.c:1221
    #13 0x7f7e885f84a0 in WriteImages MagickCore/constitute.c:1442
    #14 0x7f7e87e5239f in ConvertImageCommand MagickWand/convert.c:3332
    #15 0x7f7e87f604cf in MagickCommandGenesis MagickWand/mogrify.c:188
    #16 0x55a7a3ebefcf in MagickMain utilities/magick.c:150
    #17 0x55a7a3ebf25a in main utilities/magick.c:182
    #18 0x7f7e876c2bf6 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)

SUMMARY: AddressSanitizer: heap-buffer-overflow MagickCore/pixel-accessor.h:59 in GetPixelAlpha
Shadow bytes around the buggy address:
  0x0c547fff9650: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c547fff9660: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c547fff9670: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c547fff9680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c547fff9690: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c547fff96a0: 00 00 00 00 00 00 00 00[fa]fa fa fa fa fa fa fa
  0x0c547fff96b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c547fff96c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c547fff96d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c547fff96e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c547fff96f0: 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
==46632==ABORTING


### Images

[magick_heap_bof.zip](https://github.com/ImageMagick/ImageMagick/files/7894812/magick_heap_bof.zip)

--- end body ---

A Heap Buffer Overflow vulnerability in ImageMagick version 7.1.0-20 allows attackers to exploit the conversion of TIFF images to PICON format, potentially leading to arbitrary code execution or application crashes. The issue is triggered when the `magick` command is used to convert a specially crafted TIFF file, resulting in a segmentation fault due to improper memory access.