zziplib: heap-based buffer overflow in __zzip_get64 (fetch.c)

[Agostino Sarubbo <ago () gentoo org>]

Description:
zziplib is an intentionally lightweight library that offers the ability to 
easily extract data from files archived in a single zip file.

A fuzz on it discovered an heap overflow.

The complete ASan output:

# unzzipcat-mem $FILE
READ of size 1 at 0x60400000dff3 thread T0
    #0 0x7ff28ab675dc in __zzip_get64 /tmp/portage/dev-libs/zziplib-0.13.62-
r1/work/zziplib-0.13.62/zzip/fetch.c:59:10
    #1 0x7ff28ab64968 in zzip_mem_entry_new /tmp/portage/dev-
libs/zziplib-0.13.62-r1/work/zziplib-0.13.62/zzip/memdisk.c:221:30
    #2 0x7ff28ab64968 in zzip_mem_disk_load /tmp/portage/dev-
libs/zziplib-0.13.62-r1/work/zziplib-0.13.62/zzip/memdisk.c:137
    #3 0x7ff28ab638b7 in zzip_mem_disk_open /tmp/portage/dev-
libs/zziplib-0.13.62-r1/work/zziplib-0.13.62/zzip/memdisk.c:89:5
    #4 0x50982d in main /tmp/portage/dev-libs/zziplib-0.13.62-
r1/work/zziplib-0.13.62/bins/unzzipcat-mem.c:82:12
    #5 0x7ff289ca361f in __libc_start_main /var/tmp/portage/sys-
libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289
    #6 0x419748 in _init (/usr/bin/unzzipcat-mem+0x419748)

0x60400000dff3 is located 0 bytes to the right of 35-byte region 
[0x60400000dfd0,0x60400000dff3)
allocated by thread T0 here:
    #0 0x4d2508 in malloc /tmp/portage/sys-devel/llvm-3.9.0-
r1/work/llvm-3.9.0.src/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:64
    #1 0x7ff28ab64187 in zzip_mem_entry_new /tmp/portage/dev-
libs/zziplib-0.13.62-r1/work/zziplib-0.13.62/zzip/memdisk.c:200:25
    #2 0x7ff28ab64187 in zzip_mem_disk_load /tmp/portage/dev-
libs/zziplib-0.13.62-r1/work/zziplib-0.13.62/zzip/memdisk.c:137
    #3 0x7ff28ab638b7 in zzip_mem_disk_open /tmp/portage/dev-
libs/zziplib-0.13.62-r1/work/zziplib-0.13.62/zzip/memdisk.c:89:5
    #4 0x7ff289ca361f in __libc_start_main /var/tmp/portage/sys-
libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289

SUMMARY: AddressSanitizer: heap-buffer-overflow /tmp/portage/dev-
libs/zziplib-0.13.62-r1/work/zziplib-0.13.62/zzip/fetch.c:59:10 in 
__zzip_get64
Shadow bytes around the buggy address:
  0x0c087fff9ba0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c087fff9bb0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c087fff9bc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c087fff9bd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c087fff9be0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c087fff9bf0: fa fa fa fa fa fa fa fa fa fa 00 00 00 00[03]fa
  0x0c087fff9c00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c087fff9c10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c087fff9c20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c087fff9c30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c087fff9c40: 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
==7924==ABORTING

Affected version:
0.13.62

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/00151-zziplib-heapoverflow-__zzip_get64

Timeline:
2017-01-17: bug discovered and poked upstream
2017-02-09: blog post about the issue

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/02/09/zziplib-heap-based-buffer-overflow-in-__zzip_get64-fetch-c

-- 
Agostino Sarubbo
Gentoo Linux Developer