heap-use-after-free exit in swf_DeleteTag() at lib/rfxswf.c:1193

[Diggingwei]

Summary

A heap-use-after-free caused when using swfc, which results in out-of-bounds write.

Version

$ ./swfc -V
swfc - part of swftools 0.9.2
$ git log --oneline -1
772e55a2 (HEAD, origin/master, origin/HEAD, master)

Platform

$ uname -a
Linux 1cc373898f58 5.4.0-150-generic #167~18.04.1-Ubuntu SMP Wed May 24 00:51:42 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
clang version : 12.0.0

Reproduce

PoC : poc.zip
Command Line : ./swfc poc

Debug Info

==585==ERROR: AddressSanitizer: heap-use-after-free on address 0x606000023860 at pc 0x000000641f43 bp 0x7fffffffe1b0 sp 0x7fffffffe1a8
WRITE of size 8 at 0x606000023860 thread T0
    #0 0x641f42 in swf_DeleteTag /src/project/swftools_project/swftools/lib/rfxswf.c:1193:30
    #1 0x50ce45 in removeFromTo /src/project/swftools_project/swftools/src/swfc.c:842:6
    #2 0x50ce45 in s_endSWF /src/project/swftools_project/swftools/src/swfc.c:1041:8    
    #3 0x50ce45 in s_end /src/project/swftools_project/swftools/src/swfc.c:2380:13
    #4 0x542aaf in c_end /src/project/swftools_project/swftools/src/swfc.c:3769:5
    #5 0x51b3ad in parseArgumentsForCommand /src/project/swftools_project/swftools/src/swfc.c:4475:5
    #6 0x51b3ad in main /src/project/swftools_project/swftools/src/swfc.c:4598:2
    #7 0x7ffff7c39082 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
    #8 0x41d61d in _start (/src/project/swftools_project/swftools/src/swfc+0x41d61d)
0x606000023860 is located 32 bytes inside of 56-byte region [0x606000023840,0x606000023878)
freed by thread T0 here:
    #0 0x498612 in free (/src/project/swftools_project/swftools/src/swfc+0x498612)
    #1 0x657993 in swf_FreeTags /src/project/swftools_project/swftools/lib/rfxswf.c:1933:5

previously allocated by thread T0 here:
    #0 0x4989f2 in calloc (/src/project/swftools_project/swftools/src/swfc+0x4989f2)    
    #1 0x9bce08 in rfx_calloc /src/project/swftools_project/swftools/lib/mem.c:69:9

SUMMARY: AddressSanitizer: heap-use-after-free /src/project/swftools_project/swftools/lib/rfxswf.c:1193:30 in swf_DeleteTag
Shadow bytes around the buggy address:
  0x0c0c7fffc6b0: fa fa fa fa fd fd fd fd fd fd fd fd fa fa fa fa
  0x0c0c7fffc6c0: fd fd fd fd fd fd fd fa fa fa fa fa fd fd fd fd
  0x0c0c7fffc6d0: fd fd fd fd fa fa fa fa fd fd fd fd fd fd fd fa
  0x0c0c7fffc6e0: fa fa fa fa fd fd fd fd fd fd fd fa fa fa fa fa
  0x0c0c7fffc6f0: fd fd fd fd fd fd fd fa fa fa fa fa fd fd fd fd
=>0x0c0c7fffc700: fd fd fd fa fa fa fa fa fd fd fd fd[fd]fd fd fa
  0x0c0c7fffc710: fa fa fa fa 00 00 00 00 00 00 00 fa fa fa fa fa
  0x0c0c7fffc720: 00 00 00 00 00 00 00 00 fa fa fa fa 00 00 00 00
  0x0c0c7fffc730: 00 00 00 00 fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c0c7fffc740: fa fa fa fa 00 00 00 00 00 00 00 00 fa fa fa fa
  0x0c0c7fffc750: 00 00 00 00 00 00 00 00 fa fa fa fa 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
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  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
  Shadow gap:              cc
==585==ABORTING