audiofile: heap-based buffer overflow in MSADPCM::decodeBlock (MSADPCM.cpp)

Description:
audiofile is a C-based library for reading and writing audio files in many common formats.

A fuzz on it discovered an heap overflow.

The complete ASan output:

# sfconvert @@ out.mp3 format aiff
==2512==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x62d00001c45a at pc 0x7fe7476f387d bp 0x7ffc3b0e3bf0 sp 0x7ffc3b0e3be8
WRITE of size 2 at 0x62d00001c45a thread T0
    #0 0x7fe7476f387c in MSADPCM::decodeBlock(unsigned char const*, short*) /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/MSADPCM.cpp:222:14
    #1 0x7fe7476c1ac9 in BlockCodec::runPull() /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/BlockCodec.cpp:55:3
    #2 0x7fe7476fac20 in RebufferModule::runPull() /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/RebufferModule.cpp:122:3
    #3 0x7fe7476ab05a in afReadFrames /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/data.cpp:222:14
    #4 0x50bbeb in copyaudiodata /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:340:29
    #5 0x50b050 in main /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:248:17
    #6 0x7fe74678078f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
    #7 0x419f48 in _init (/usr/bin/sfconvert+0x419f48)

0x62d00001c45a is located 0 bytes to the right of 32858-byte region [0x62d000014400,0x62d00001c45a)
allocated by thread T0 here:
    #0 0x4d2d08 in malloc /tmp/portage/sys-devel/llvm-3.9.1-r1/work/llvm-3.9.1.src/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:64
    #1 0x7fe746419687 in operator new(unsigned long) (/usr/lib/gcc/x86_64-pc-linux-gnu/6.3.0/libstdc++.so.6+0xb2687)
    #2 0x7fe7476af43c in afGetFrameCount /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/format.cpp:205:41
    #3 0x50bb5c in copyaudiodata /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:329:29
    #4 0x50b050 in main /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:248:17
    #5 0x7fe74678078f 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-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/MSADPCM.cpp:222:14 in MSADPCM::decodeBlock(unsigned char const*, short*)
Shadow bytes around the buggy address:
  0x0c5a7fffb830: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c5a7fffb840: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c5a7fffb850: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c5a7fffb860: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c5a7fffb870: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c5a7fffb880: 00 00 00 00 00 00 00 00 00 00 00[02]fa fa fa fa
  0x0c5a7fffb890: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5a7fffb8a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5a7fffb8b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5a7fffb8c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c5a7fffb8d0: 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
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==2512==ABORTING

Affected version:
0.3.6

Fixed version:
N/A

Commit fix:
N/A

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

CVE:
CVE-2017-6832

Reproducer:
https://github.com/asarubbo/poc/blob/master/00186-audiofile-heapoverflow-MSADPCM-decodeBlock

Timeline:
2017-02-20: bug discovered and reported to upstream
2017-02-20: blog post about the issue
2017-03-12: CVE assigned

Note:
This bug was found with American Fuzzy Lop.

Permalink:

audiofile: heap-based buffer overflow in MSADPCM::decodeBlock (MSADPCM.cpp)