From ciac@tholia.llnl.gov Sat Jan 31 13:19:33 1998 From: CIAC Mail User To: ciac-bulletin@tholia.llnl.gov Date: Fri, 30 Jan 1998 14:51:52 -0800 (PST) Subject: CIAC Bulletin I-025A: Windows NT based Web Servers File Access Vulnerability [ For Public Release ] -----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Windows NT based Web Servers File Access Vulnerability January 30, 1998 21:00 GMT Number I-025A ______________________________________________________________________________ PROBLEM: Some Windows NT based web servers allow access to 8.3 format filenames. This can allow unauthorized access to files via their 8.3 compatible name. PLATFORM: Microsoft Internet Information Server and Peer Web Server 4.0, Netscape FastTrack 2.x DAMAGE: By exploiting this vulnerability, remote users may gain unauthorized access to files accessed by the web server. SOLUTION: Apply the fixes listed in Section 3 of this advisory. ______________________________________________________________________________ VULNERABILITY Exploit information involving this vulnerability has been made ASSESSMENT: publicly available. ______________________________________________________________________________ Introduction ============ Windows NT file systems support filenames of up to 255 characters. For compatibility purposes, a short filename (the 8.3 filename) is usually created for each file, and can be used by older applications to access directories and files with long names. Web server file protection of directories and files in long filename (not 8.3) formats can often allow access to the short name (8.3) equivalent without restriction. Some Windows NT based Web servers base their access control check for permissions using the long filename only, and do not include the short name that may be used as an alias. For example, if there was a file named noteightdotthree.htm, and it was protected at the file level by the web server (NOT the NTFS file system itself), the access of the short name noteig~1.htm is possible. This also applies to directories. Note that NTFS level file restrictions are always applied correctly because they are not inherently tied to the long name, but to the name stored on disk, which the long name references. Some web servers allow you to set access permissions in places other than NTFS, however it is the implementation of these controls that are causing the vulnerability. The characteristics of this vulnerability also appear in IIS 3.0 and PWS 3.0, but only at the directory level. Using the long file name IIS or PWS 3.0 to protect an execute only directory inside a read-execute or read-only is not recommended. Microsoft has stated that they do not consider it a bug, but a 'bad' practice. This vulnerability may easily affect other Windows NT based WWW servers. CIAC recommends that you check with your vendor to ensure your WWW server does not exhibit this characteristic. Problem ======= This vulnerability permits attackers to gain unauthorized access to files on the Web server. It may be used to download the source code of server scripts in some configurations. If exploited it can give an intruder access to any file that the web server can access. Prevention ========== Microsoft IIS 4.0 and PWS 4.0 ============================== Microsoft has developed a hot-fix to correct the problem. CIAC has verified that the hot-fix corrects the problem described above, but has not done any regression testing. Instructions for installing it are available from Microsoft. Microsoft recommends that you update your Emergency Repair Disk before you apply the patch, as they have not regression tested the hot-fix. Microsoft's patch location: Windows NT 4.0 (CIAC recommends that Service Pack 3 is installed first): ftp://ftp.microsoft.com/bussys/IIS/iis-public/fixes/usa/security/sfn-fix/ Microsoft IIS 3.0 and PWS 3.0 ============================== Although Microsoft does not consider this a bug, CIAC recommends that you ensure directory access controls are not nested. Verify that WWW server protections are not being used to enforce protection for execute-only directories that reside in read-only or read-execute directories. Netscape FastTrack 2.x ======================= Netscape will be producing patches. _______________________________________________________________________ Thanks to: NtBugtraq Mailing List (NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM) David LeBlanc Michael Howard _______________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 510-422-8193 FAX: +1 510-423-8002 STU-III: +1 510-423-2604 E-mail: ciac@llnl.gov For emergencies and off-hour assistance, DOE, DOE contractor sites, and the NIH may contact CIAC 24-hours a day. During off hours (5PM - 8AM PST), call the CIAC voice number 510-422-8193 and leave a message, or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC duty person, and the secondary PIN number, 8550074 is for the CIAC Project Leader. Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ (or http://ciac.llnl.gov -- they're the same machine) Anonymous FTP: ftp.ciac.org (or ciac.llnl.gov -- they're the same machine) Modem access: +1 (510) 423-4753 (28.8K baud) +1 (510) 423-3331 (28.8K baud) CIAC has several self-subscribing mailing lists for electronic publications: 1. CIAC-BULLETIN for Advisories, highest priority - time critical information and Bulletins, important computer security information; 2. SPI-ANNOUNCE for official news about Security Profile Inspector (SPI) software updates, new features, distribution and availability; 3. SPI-NOTES, for discussion of problems and solutions regarding the use of SPI products. Our mailing lists are managed by a public domain software package called Majordomo, which ignores E-mail header subject lines. To subscribe (add yourself) to one of our mailing lists, send the following request as the E-mail message body, substituting ciac-bulletin, spi-announce OR spi-notes for list-name: E-mail to ciac-listproc@llnl.gov or majordomo@tholia.llnl.gov: subscribe list-name e.g., subscribe ciac-bulletin You will receive an acknowledgment email immediately with a confirmation that you will need to mail back to the addresses above, as per the instructions in the email. This is a partial protection to make sure you are really the one who asked to be signed up for the list in question. If you include the word 'help' in the body of an email to the above address, it will also send back an information file on how to subscribe/unsubscribe, get past issues of CIAC bulletins via email, etc. PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC) I-015: SGI IRIX Vulnerabilities (syserr and permissions programs) I-016: SCO /usr/bin/X11/scoterm Vulnerability I-017: statd Buffer Overrun Vulnerability I-018: FTP Bounce Vulnerability I-019: Tools Generating IP Denial-of-Service Attacks I-020: Cisco 7xx password buffer overflow - DOS I-021: "smurf" IP Denial-of-Service Attacks I-022: IBM AIX "routed" daemon Vulnerability I-023: Macro Virus Update I-024: CGI Security Hole in EWS1.1 Vulnerability -----BEGIN PGP SIGNATURE----- Version: 4.0 Business Edition iQCVAwUBNNJUkLnzJzdsy3QZAQGIiQQAkwZr21E0LTTeVwT+0BmzdnXSCDbZ4i5g XveNQ6lPPRTi1RK7gZQZgtWG0P2N6UAF5LyXzMZCh4XpiXwfghN0A7/1sI5GBAF0 cLWJVCmV8EEALij4pamSQYiFzAMCawcQxP1kANGQcI//0grBiQxQOiSTWobVZRwm tQwrHbbAEpo= =Q35R -----END PGP SIGNATURE-----