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Message-ID: <20120321073659.GA24538@vermeer.pre-sense.de>
Date: Wed, 21 Mar 2012 08:37:00 +0100
From: Timo Warns <Warns@...-Sense.DE>
To: oss-security@...ts.openwall.com
Subject: CVE-2012-1162 / -1163: Incorrect loop construct and numeric
overflow in libzip
The following two issues in libzip have been handled via
distros@...openwall.org. Distros and the libzip developers were informed on
2012-03-12. An update of libzip has become available on 2012-03-20, the
appointed coordinated release date. The PHP and zipruby developers have been
informed before 2012-03-16, but have not released updates yet.
libzip (version <= 0.10) has two vulnerabilities that may lead to a heap
overflow or an information leak via corrupted zip files. PHP (versions
5.4.0 and <= 5.3.10) and the Ruby binding zipruby (version <= 0.3.6) are
also affected as they include copies of affected libzip versions.
* CVE-2012-1162
libzip (version <= 0.10) uses an incorrect loop construct, which can
result in a heap overflow on corrupted zip files.
On opening a zip file with zip_open, libzip reads in the number of
directory entries in the function _zip_readcdir in zip_open.c:
(192) /* number of cdir-entries */
(193) nentry = _zip_read2(&cdp);
Subsequently, memory for directory entries is allocated via
_zip_cdir_new (in zip_dirent.c) based on the number of directory
entries:
(104) if ((cd->entry=(struct zip_dirent *)malloc(sizeof(*(cd->entry))*nentry))
If the number of directories in the zip file is set to 0, 0 bytes of
memory are allocated.
_zip_readcdir finishes with reading in the directory entries in
a posttest do-while loop:
(260) do {
(261) if ((_zip_dirent_read(cd->entry+i, fp, bufp, &left, 0, error)) < 0) {
...
(277) } while (i<cd->nentry && left > 0);
If cd->entry points to 0 bytes of allocated memory, _zip_dirent
writes beyond the allocated memory.
* CVE-2012-1163
libzip (version <= 0.10) has a numeric overflow condition, which,
for example, results in improper restrictions of operations within
the bounds of a memory buffer (e.g., allowing information leaks).
On opening a zip file with zip_open, libzip reads in the size and the
offset of the central directory structure in the function _zip_readcdir
in zip_open.c:
(198) cd->size = _zip_read4(&cdp);
(199) cd->offset = _zip_read4(&cdp);
libzip performs a consistency check on these values, but does not
anticipate an integer overflow:
(203) if (cd->offset+cd->size > buf_offset + (eocd-buf)) {
On an integer overflow, libzip continues to handle the zip file, which,
for example, can result in improper restriction of operations within the
bounds of a memory buffer.
Cheers, Timo
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