audiofile: heap-based buffer overflow in Expand3To4Module::run (SimpleModule.h)

["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 an heap overflow.

The complete ASan output:

# sfconvert @@ out.mp3 format aiff
==1731==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7fd325141800 at pc 0x7fd324dab3e7 bp 0x7fff5fd78e20 
sp 0x7fff5fd78e18                                                                                                       
                                
WRITE of size 4 at 0x7fd325141800 thread T0                                                                             
                                                                                                                        
                               
    #0 0x7fd324dab3e6 in void Expand3To4Module::run(unsigned char const*, int*, int) 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/SimpleModule.h:268:14              
                                                             
    #1 0x7fd324dab3e6 in Expand3To4Module::run(Chunk&, Chunk&) 
/tmp/portage/media-libs/audiofile-0.3.6-r1/work/audiofile-0.3.6/libaudiofile/modules/SimpleModule.h:241                 
                                                                                        
    #2 0x7fd324d8105a 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 0x7fd323e5678f 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)                                                                  
                                                                                                                        
                               
                                                                                                                        
                                                                                                                        
                               
0x7fd325141800 is located 0 bytes to the right of 524288-byte region [0x7fd3250c1800,0x7fd325141800)                    
                                                                                                                        
                               
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 0x7fd323e5678f 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/SimpleModule.h:268:14 in void 
Expand3To4Module::run(unsigned char const*, int*, int)                                                 
Shadow bytes around the buggy address:                                                                                  
                                                                                                                        
                               
  0x0ffae4a202b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                       
                                                                                                                        
                               
  0x0ffae4a202c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                       
                                                                                                                        
                               
  0x0ffae4a202d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                       
                                                                                                                        
                               
  0x0ffae4a202e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                       
                                                                                                                        
                               
  0x0ffae4a202f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00                                                       
                                                                                                                        
                               
=>0x0ffae4a20300:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                       
                                                                                                                        
                               
  0x0ffae4a20310: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                       
                                                                                                                        
                               
  0x0ffae4a20320: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                       
                                                                                                                        
                               
  0x0ffae4a20330: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                       
                                                                                                                        
                               
  0x0ffae4a20340: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa                                                       
                                                                                                                        
                               
  0x0ffae4a20350: 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
==1731==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/00190-audiofile-heapoverflow-Expand3To4Module-run

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-heap-based-buffer-overflow-in-expand3to4modulerun-simplemodule-h

--
Agostino Sarubbo
Gentoo Linux Developer