zziplib: NULL pointer dereference in main (unzzipcat.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 a NULL pointer access.

The complete ASan output:

# unzzipcat $FILE
==22686==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 
0x7f6de98b259a bp 0x7ffddc25a080 sp 0x7ffddc259f98 T0)
==22686==The signal is caused by a READ memory access.
==22686==Hint: address points to the zero page.
    #0 0x7f6de98b2599 in strlen /var/tmp/portage/sys-libs/glibc-2.22-
r4/work/glibc-2.22/string/../sysdeps/x86_64/strlen.S:76
    #1 0x7f6de989b7ab in _IO_puts /var/tmp/portage/sys-libs/glibc-2.22-
r4/work/glibc-2.22/libio/ioputs.c:36
    #2 0x509d73 in main /tmp/portage/dev-libs/zziplib-0.13.62-
r1/work/zziplib-0.13.62/bins/unzzipcat.c:94:6
    #3 0x7f6de985161f in __libc_start_main /var/tmp/portage/sys-
libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289
    #4 0x419848 in _init (/usr/bin/unzzipcat+0x419848)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /var/tmp/portage/sys-libs/glibc-2.22-
r4/work/glibc-2.22/string/../sysdeps/x86_64/strlen.S:76 in strlen
==22686==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/00158-zziplib-nullptr-main

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-null-pointer-dereference-in-main-unzzipcat-c

-- 
Agostino Sarubbo
Gentoo Linux Developer