Topic: Special devices access in multiple archivers
Author: 3APA3A <3APA3A@security.nnov.ru>
Affected Software: WinZIP Computing's WinZIP 8.0, PKWare PkZip
4.0, RARSoft WinRar 2.80
Released: July, 5, 2001
SECURITY.NNOV advisories: http://security.nnov.ru/advisories
Archive extraction is usually treated by users as safe operation.
There are a lot of problem with files extraction though.
Among them: huge files with high compression ratio are able to fill
memory/disk (see "Antivirus scanner DoS with zip archives" thread on
Vuln-Dev), special device names and special characters in file names,
directory traversal (dot-dot bug). All this issues are not new and are
known to be exploited.
Special device access is mostly Windows-specific problem, because in
Windows some of devices are not located in some specific place, but
are placed in every directory (e.g. c:\temp\prn). Also file extension
is ignored (c:\temp\prn.txt also refers to special device). Kernel
mode drivers can create their own special devices. Special devices in
Windows also represent physical disks, tapes, UNC names, and a lot of
other devices. For example, user with administrator's privileges can
access physical disk (including MBR) via special device
\\.\PhysicalDrive# under Windows NT/2000. This access can lead to
system compromise. Same API functions are used to access special
devices and ordinary files. That's why special device access should be
treated as very serious and dangerous issue under Windows.
If during extraction archiver doesn't check a name and type of
destination file (e.g. using GetFileType() API) extracted file can be
redirected to special device on archive creator's choice.
WinZip is vulnerable to special device problems. If archived file
has name referring to special device it will be sent to this device
silently. Authors contacted, but in fact I don't see any attempt to
work this situation out:
-- quote firstname.lastname@example.org
WinZip will indeed have a problem with files which are named using what
windows considers 'reserved' words; The windows operating system itself
does not allow such words in filenames, although they may be considered
perfectly valid under other operating systems.
Please let me know if you have any questions.
-- quote email@example.com--
-- quote from second message firstname.lastname@example.org
We are of course quite concious of the ramifications of the situation,
and both the development staff and the QA personell are involved in
addressing and testing such issues. Thanks for your concern.
If you have any further questions or feedback, please don't hesitate to
-- quote from second message email@example.com--
It reminds me something from Mark Twain.
PKWare PKZip 4.00:
Is vulnerable. It doesn't detect special devices, but it detects
existence of the file and asks confirmation from user before writing.
If pkzip configured to overwrite files without prompt file will be
overwritten silently. Vendor contacted, but no feedback were given on
RARSoft WinRAR 2.80
WinRAR uses GetFileType() to determine type of target file, but fails
to check FILE_TYPE_PIPE case. It leaves possibility to access some
certain types of devices, including (but not limited to) prn, but
most dangerous devices are filtered. Overwrite confirmation also
required. According to Eugene Roshal problem will be completely fixed
in nearest version.
Archivers ported from Unix:
Info-Zip's UnZip, Cygwin's port of tar and probably different ported
archivers are vulnerable. DJGPP (GNU) DOS port of tar is safe (it
Given archives prntest.zip, prntest.rar, prntest.tar contain file
with PRN name. It should print one text page on device attached to
PRN on extraction (PRN refers by default to LPT1, you need printer
installed on LPT1 in order to test it. You needn't to connect
printing device - just install any driver). Try to extract it with
your favorite archiver.
Test content of the archives before extraction if archive was
obtained from untrusted source. Never automate extraction and never
use administrator's account to extract data.
Wait for vendor's patch.