Package: libmspack0 Version: 0.4-3 Usertags: aflThere's an off-by-one(?) buffer under-read in mspack/lzxd.c. To reproduce the bug, rebuild libmspack with -fsanitize=address and run:
$ test/cabd_md5 lzxd-under-read.cab *** lzxd-under-read.cab ERROR; file "test1.txt" cannot be extracted, cabinet set is incomplete. lzxd-under-read.cab: error extracting "test1.txt": error in data format ================================================================= ==8354==ERROR: AddressSanitizer: heap-buffer-overflow on address 0xf4a028ff at pc 0x80604a7 bp 0xffdf8028 sp 0xffdf801c READ of size 1 at 0xf4a028ff thread T0 #0 0x80604a6 in lzxd_decompress mspack/lzxd.c:516 #1 0x80568c7 in cabd_extract mspack/cabd.c:1067 #2 0x804a8e3 in main test/cabd_md5.c:145 #3 0xf707ca62 in __libc_start_main (/lib/i386-linux-gnu/i686/cmov/libc.so.6+0x19a62) #4 0x8048f10 (/home/jwilk/libmspack-0.4/test/cabd_md5+0x8048f10) 0xf4a028ff is located 1 bytes to the left of 4096-byte region [0xf4a02900,0xf4a03900) allocated by thread T0 here: #0 0xf725c6e4 in malloc (/usr/lib/i386-linux-gnu/libasan.so.1+0x4e6e4) #1 0x80497af in m_alloc test/md5_fh.h:111 #2 0x805c27b in lzxd_init mspack/lzxd.c:313 #3 0x8057264 in cabd_init_decomp mspack/cabd.c:1126 #4 0x805634f in cabd_extract mspack/cabd.c:1034 #5 0x804a8e3 in main test/cabd_md5.c:145 #6 0xf707ca62 in __libc_start_main (/lib/i386-linux-gnu/i686/cmov/libc.so.6+0x19a62) The relevant code is: /* read 1-16 (not 0-15) bits to align to bytes */ ENSURE_BITS(16); if (bits_left > 16) i_ptr -= 2; bits_left = 0; bit_buffer = 0; /* read 12 bytes of stored R0 / R1 / R2 values */ for (rundest = &buf[0], i = 0; i < 12; i++) { READ_IF_NEEDED; *rundest++ = *i_ptr++; }As I understand it, ENSURE_BITS can rewind i_ptr to the beginning of the buffer, and then "i_ptr -= 2" makes the pointer go one (or two?) bytes prior to the buffer.
-- 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 libmspack0 depends on: ii libc6 2.19-13 ii multiarch-support 2.19-13 -- Jakub Wilk
lzxd-under-read.cab
Description: application/cab