audiofile: heap-based buffer overflow in alaw2linear_buf (G711.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
==2480==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7f5eb894d800 at pc 0x7f5eb85a699f bp 0x7ffe19064df0 sp 0x7ffe19064de8
WRITE of size 2 at 0x7f5eb894d800 thread T0
    #0 0x7f5eb85a699e in alaw2linear_buf(unsigned char const*, short*, int) /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/G711.cpp:54:13
    #1 0x7f5eb85a699e in G711::runPull() /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/G711.cpp:209
    #2 0x7f5eb858d05a in afReadFrames /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/data.cpp:222:14
    #3 0x50bbeb in copyaudiodata /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:340:29
    #4 0x50b050 in main /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:248:17
    #5 0x7f5eb766278f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
    #6 0x419f48 in _init (/usr/bin/sfconvert+0x419f48)

0x7f5eb894d800 is located 0 bytes to the right of 393216-byte region [0x7f5eb88ed800,0x7f5eb894d800)
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 0x50bb48 in copyaudiodata /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:327:17
    #2 0x50b050 in main /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:248:17
    #3 0x7f5eb766278f 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/G711.cpp:54:13 in alaw2linear_buf(unsigned char const*, short*, int)
Shadow bytes around the buggy address:
  0x0fec57121ab0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fec57121ac0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fec57121ad0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fec57121ae0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fec57121af0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0fec57121b00:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fec57121b10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fec57121b20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fec57121b30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fec57121b40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0fec57121b50: 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
==2480==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-2017-6830

Reproducer:
https://github.com/asarubbo/poc/blob/master/00184-audiofile-heapoverflow-alaw2linear_buf

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 alaw2linear_buf (G711.cpp)