audiofile: heap-based buffer overflow in ulaw2linear_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
WRITE of size 2 at 0x7fb583d33800 thread T0                                                                                                                                                                                                                                    
    #0 0x7fb58398c8b1 in ulaw2linear_buf(unsigned char const*, short*, int) /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/G711.cpp:42:13                                                                                                
    #1 0x7fb58398c8b1 in G711::runPull() /tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/G711.cpp:206                                                                                                                                     
    #2 0x7fb58397305a 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 0x7fb582a4878f 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)                                                                                                                                                                                                                         
                                                                                                                                                                                                                                                                               
0x7fb583d33800 is located 0 bytes to the right of 917504-byte region [0x7fb583c53800,0x7fb583d33800)                                                                                                                                                                           
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 0x7fb582a4878f 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:42:13 in ulaw2linear_buf(unsigned char const*, short*, int)                                                                      
Shadow bytes around the buggy address:                                                                                                                                                                                                                                         
  0x0ff73079e6b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                                                                                                                                                                              
  0x0ff73079e6c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                                                                                                                                                                              
  0x0ff73079e6d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                                                                                                                                                                              
  0x0ff73079e6e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                                                                                                                                                                              
  0x0ff73079e6f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                                                                                                                                                                              
=>0x0ff73079e700:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                                                                                                                                                                              
  0x0ff73079e710: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                                                                                                                                                                              
  0x0ff73079e720: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                                                                                                                                                                              
  0x0ff73079e730: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                                                                                                                                                                              
  0x0ff73079e740: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                                                                                                                                                                              
  0x0ff73079e750: 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
==2586==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-2017-6834

Reproducer:
https://github.com/asarubbo/poc/blob/master/00188-audiofile-heapoverflow-ulaw2linear_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 ulaw2linear_buf (G711.cpp)