audiofile: global buffer overflow in decodeSample (IMA.cpp)

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

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

A fuzz on it discovered a global overflow.

The complete ASan output:

# sfconvert @@ out.mp3 format aiff                                                                                      
                                                                                                                        
                                 
==1779==ERROR: AddressSanitizer: global-buffer-overflow on address 0x7f0add7e6a7a at pc 0x7f0add77c221 bp 
0x7ffe13caabf0 sp 0x7ffe13caabe8
READ of size 2 at 0x7f0add7e6a7a thread T0
    #0 0x7f0add77c220 in decodeSample(adpcmState&, unsigned char) 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/IMA.cpp:144:13
    #1 0x7f0add77c220 in IMA::decodeBlockWAVE(unsigned char const*, short*) 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/IMA.cpp:186
    #2 0x7f0add77b671 in IMA::decodeBlock(unsigned char const*, short*) 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/IMA.cpp:110:10
    #3 0x7f0add777ac9 in BlockCodec::runPull() 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/BlockCodec.cpp:55:3
    #4 0x7f0add7b0c20 in RebufferModule::runPull() 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/RebufferModule.cpp:122:3
    #5 0x7f0add76105a in afReadFrames 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/data.cpp:222:14
    #6 0x50bbeb in copyaudiodata 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:340:29
    #7 0x50b050 in main /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/sfcommands/sfconvert.c:248:17
    #8 0x7f0adc83678f in __libc_start_main 
/tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
    #9 0x419f48 in _init (/usr/bin/sfconvert+0x419f48)

0x7f0add7e6a7a is located 6 bytes to the left of global variable 'indexTable' defined in 
'/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/IMA.cpp:116:21' (0x7f0add7e6a80) 
of size 16
0x7f0add7e6a7a is located 40 bytes to the right of global variable 'stepTable' defined in 
'/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/IMA.cpp:122:22' (0x7f0add7e69a0) 
of size 178
SUMMARY: AddressSanitizer: global-buffer-overflow 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/IMA.cpp:144:13 in 
decodeSample(adpcmState&, 
unsigned char)
Shadow bytes around the buggy address:
  0x0fe1dbaf4cf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fe1dbaf4d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 07 f9 f9
  0x0fe1dbaf4d10: f9 f9 f9 f9 00 00 00 00 00 00 00 04 f9 f9 f9 f9
  0x0fe1dbaf4d20: 00 00 00 00 00 00 01 f9 f9 f9 f9 f9 00 00 01 f9
  0x0fe1dbaf4d30: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0fe1dbaf4d40: 00 00 00 00 00 00 00 00 00 00 02 f9 f9 f9 f9[f9]
  0x0fe1dbaf4d50: 00 00 f9 f9 f9 f9 f9 f9 00 00 03 f9 f9 f9 f9 f9
  0x0fe1dbaf4d60: 00 00 05 f9 f9 f9 f9 f9 00 00 00 00 00 00 00 00
  0x0fe1dbaf4d70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0fe1dbaf4d80: 00 00 00 00 01 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
  0x0fe1dbaf4d90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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
==1779==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:
N/A

Reproducer:
https://github.com/asarubbo/poc/blob/master/00183-audiofile-globaloverflow-decodeSample

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

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/02/20/audiofile-global-buffer-overflow-in-decodesample-ima-cpp

--
Agostino Sarubbo
Gentoo Linux Developer