Bug#776239: unshield: out-of-bounds read

[Jakub Wilk]

Package: unshield
Version: 1.0-1
Usertags: afl

Unshield crashes on this (slightly corrupted) archive:

$ unshield t data1.cab
Segmentation fault


GDB says it's an out-of-bounds read:

#0  0xf7fb565a in get_unaligned_le32 (p=0x5f40e4e8 <error: Cannot access memory at 
address 0x5f40e4e8>) at internal.h:138
#1  0xf7fb5732 in unshield_component_new (header=0x804dfd0, offset=1463549952) 
at component.c:30
#2  0xf7fb8eff in unshield_header_get_components (header=0x804dfd0) at 
libunshield.c:155
#3  0xf7fb942d in unshield_read_headers (unshield=0x804dfb0, version=-1) at 
libunshield.c:309
#4  0xf7fb95db in unshield_open_force_version (filename=0xffffda22 "data1.cab", 
version=-1) at libunshield.c:361
#5  0x08049db1 in main (argc=3, argv=0xffffd864) at unshield.c:574


This bug was found using American fuzzy lop:
https://packages.debian.org/experimental/afl



-- System Information:
Debian Release: 8.0
 APT prefers unstable
 APT policy: (990, 'unstable'), (500, 'experimental')
Architecture: i386 (x86_64)
Foreign Architectures: amd64

Kernel: Linux 3.2.0-4-amd64 (SMP w/2 CPU cores)
Locale: LANG=C, LC_CTYPE=pl_PL.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)

Versions of packages unshield depends on:
ii  libc6         2.19-13
ii  libunshield0  1.0-1
ii  zlib1g        1:1.2.8.dfsg-2+b1

--
Jakub Wilk

Disclaimer: I don't have spare CPU cycles, so I fuzzed only till the first crash (which took a few seconds). It's likely that extensive fuzzing would uncover more interesting crashers. I'd encourage Unshield maintainers to perform fuzzing with AFL on their own. :-)

data1.cab
Description: Binary data

data1.hdr
Description: Binary data