Hello, Topic: Special devices access in multiple archivers Author: 3APA3A <3APA3Aat_private> 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 helpat_private 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 helpat_private-- --quote from second message helpat_private 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 helpat_private-- 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 /\_/\ { . . } |\ +--oQQo->{ ^ }<-----+ \ | 3APA3A U 3APA3A } +-------------o66o--+ / |/ You know my name - look up my number (The Beatles)
This archive was generated by hypermail 2b30 : Sun Jul 15 2001 - 20:38:23 PDT