Hello,

Topic: Special devices access in multiple archivers
Author: 3APA3A <3APA3Asecurity.nnov.ru>
Platform: Windows
Affected Software: WinZIP Computing's WinZIP 8.0, PKWare PkZip
                          4.0, RARSoft WinRar 2.80
Risk: average
Released: July, 5, 2001
SECURITY.NNOV advisories: http://www.security.nnov.ru/advisories

Background:

Archive extraction is usually treated by users as safe operation.
There are a lot of problem with files extraction though.

Problem(s):

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 (if not
combined with path globing or directory traversal), because in Windows
some devices are not located in specific place, but coexist 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. This kind of access can lead to system compromise. Same API
functions are used to access special devices and ordinary files.
That's why unchecked 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.

Detailed info:

 WinZip 8.0:

 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 helpwinzip.com
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 helpwinzip.com--

--quote from second message helpwinzip.com
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
write.
--quote from second message helpwinzip.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
 overwriting. If pkzip configured to overwrite files without prompt
 file will be extracted silently. Vendor contacted, but no feedback
 were given on this issue.

 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
 uses stat() to check type of file and limitation of DOS API doesn't
 allow to access most dangerous devices).
 

Exploitation:

 You can find archives with demonstration of PRN access on
 http://www.security.nnov.ru/advisories/archdos.asp

Workaround:

 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.

Solution:

 Wait for vendor's patch or use safe archivers.

-- 
http://www.security.nnov.ru
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