cabextract 1.3 fixes several bugs in cabextract 1.2, including fixing two security bugs.
The two security bugs are as follows:
Bug 1: Infinite loop in MS-ZIP decoder
The MS-ZIP and Quantum decoders read bits in roughly the same way as the LZX decoder, however they don't have "inject two fake bytes" code.
In the situation where read() provides zero bytes, e.g. at the end of file or end of a CAB block, the LZX decoder handles this by injecting two fake bytes, then returns an error on subsequent calls. MS-ZIP and Quantum instead return zero bytes without error. However, all three decoders are written to presume they will get at least one byte. So this could lead to an infinite loop in MS-ZIP and Quantum. An infinite loop has definitely been seen in MS-ZIP - there is a while loop in inflate() of an uncompressed block (block type 0) which won't end until enough input is provided.
Partial solution: change "if (read < 0)" to "if (read <= 0)" in mszipd.c and qtmd.c.
However, this breaks compatibility with a number of MS-ZIP/Quantum encoded files. A full solution would be to implement the same bit-reading system as LZX. I've done this now, merging all the bit-reading and huffman-reading code into two new files; readbits.h and readhuff.h
There are several further changes made to integrate readbits.h and readhuff.h, I recommend you look at the latest version in the source repository.
Bug 2: Segmentation fault in "cabextract -t"
This bug may not affect you, depending on your implementation of mspack_system->write(). It does cause a segfault in cabextract's cabx_write() in "-t" (test archive) mode.
In the Quantum decoder, when the window wrap is reached, all currently unwritten data is flushed to disk. Sometimes, less data is needed than is flushed, which makes the variable out_bytes negative.
When the main decoding loop finishes, a final call to write() is made if out_bytes is not zero. In that situation, it calls mspack_system->write() with a negative byte count, e.g. -129 bytes. You should reject this. In cabextract's "-t" mode, this is not caught, but instead converted to an unsigned integer and passed to md5_process_bytes(), which tries to read e.g. 4294967167 bytes, causing it to read beyond the end of valid process space and thus segfault.
- Break out to the end of the decoding loop immediately if the flush would be more than needed.
- Add checking of the "bytes" argument in mspack_system read() / write() implementations, just to be sure.
New version bumped. Arch teams, please, test it and stabilize.
"enhancement" is not an appropriate priority for a security bug (it was previously a request to bump). Resetting to "normal".
Stable for HPPA PPC.
The MS-ZIP decompressor in cabextract before 1.3 allows remote
attackers to cause a denial of service (infinite loop) via a
malformed MSZIP archive in a .cab file during a (1) test or (2)
extract action, related to the libmspack library.
Integer signedness error in the Quantum decompressor in cabextract
before 1.3, when archive test mode is used, allows user-assisted
remote attackers to cause a denial of service (application crash) or
possibly execute arbitrary code via a crafted Quantum archive in a
.cab file, related to the libmspack library.
GLSA request filed.
This issue was resolved and addressed in
GLSA 201312-09 at http://security.gentoo.org/glsa/glsa-201312-09.xml
by GLSA coordinator Chris Reffett (creffett).