****************************************************************************** ------ ----- ----- --- ----- | ----- ---- | | | | | |--- | | | | | | | | | |-- | | | | |-- | | | | | | | | \ | | ----- ---- ----- ----- | \ ----- A D V I S O R Y FA-98.11 ****************************************************************************** Topic: Microsoft Windows-based Web Servers unauthorized access - long file names Source: CERT/CC Creation Date: February 06, 1998 Last Updated: February 11, 1998 Advisory name change Updates to Solution Section III.B Added Acknowledgment A complete revision history is at the end of this file. To aid in the wide distribution of essential security information, FedCIRC is forwarding the following information from CERT/CC Advisory CA-98.04. FedCIRC urges you to act on this information as soon as possible. If you have any questions, please contact FedCIRC: Telephone: +1 888 282 0870 Email: fedcirc@fedcirc.gov =======================FORWARDED TEXT STARTS HERE============================ -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= CERT* Advisory CA-98.04 Original issue date: Feb. 06, 1998 Last revised: February 11, 1998 Advisory name change Updates to Solution Section III.B Added Acknowledgment A complete revision history is at the end of this file. Topic: Microsoft Windows-based Web Servers unauthorized access - long file names - ----------------------------------------------------------------------------- An exploitation involving long file names on Microsoft Windows-based web servers has recently been described on public mailing lists. When files on the web server have names longer than 8.3 (8 characters plus a 3-character extension), users can gain unauthorized access to files protected solely by the web server. The CERT/CC team recommends installing patches from your vendor (see Section III.A and the appendix). Until you are able to do so, we urge you to use the workaround described in Section III.B. We will update this advisory as we receive additional information. Please check our advisory files regularly for updates that relate to your site. - ----------------------------------------------------------------------------- I. Description All 32-bit Microsoft Windows operating systems (commonly known as Win32) can associate two different file names with a stored file, a short name and a long name. The short version, known as 8.3-compliant, is restricted to a length of 8 characters and an extension of 3 characters. This version is required for backward compatibility with DOS. The long version of the file name is not restricted to the 8.3-compliant format but is restricted to a total length of 255 characters. When Win32 stores a file with a short name (i.e., 8.3-compliant), it associates only that short file name with the file. However, when Win32 stores a file with a long name (i.e., greater than 8 characters), it associates two versions of the file name with the file--the original, long file name and an 8.3-compliant short file name that is derived from the long name in a predictable manner. Example: The 8.3-compliant short file name "Abcdefgh.xyz" is represented (1) as is: "Abcdefgh.xyz". However, the long file name "Abcdefghijk.xyz" is represented: (1) as is: "Abcdefghijk.xyz" and (2) as 8.3-compliant: "Abcdef~1.xyz". Some Win32-based web servers have not compensated for the two file name versions when restricting access to files that have long names. The web servers attempt to restrict access by building an internal list of restricted file names. However, for files with long names, only the long, and not the short, file name is added to this internal list. This leaves the file unprotected by the web server because the file is still accessible via the short file name. For example, "Abcdefgh.xyz" (short) would be protected by the web server, but "Abcdefghijk.xyz" (long) would not be completely protected by the web server. II. Impact Users are able to gain unauthorized access to files protected solely by the web server. III. Solution CERT/CC urges you to immediately apply vendor patches if they are available. Until you are able to do so, we urge you to use the workaround described in Section B. A. Obtain and install a patch for this problem. Appendix A contains input from vendors who have provided information for this advisory. We will update the appendix as we receive more information. If you do not see your vendor's name, the CERT/CC did not hear from that vendor. Please contact your vendor directly. B. Until you are able to install the appropriate patch, we recommend the following workaround. (1) Use only 8.3-compliant short file names for the files that you want to have protected solely by the web server. On FAT file systems (16-bit) this can be enforced by enabling (setting to 1) the "Win31FileSystem" registry key (registry path: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\FileSystem\). (2) On NTFS (32-bit), you can disable the creation of the 8.3-compliant short file name for files with long file names by enabling (setting to 1) the "NtfsDisable8dot3NameCreation" registry key (registry path: HKEY_LOCAL_MACHINE\System\ CurrentControlSet\Control\FileSystem\). However, this step may cause compatibility problems with 16-bit applications. (3) Use NTFS-based ACLs (directory or file level access control lists) to augment or replace web server-based security. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Appendix A - Vendor Information Below is a list of the vendors who have provided information for this advisory. We will update this appendix as we receive additional information. If you do not see your vendor's name, the CERT/CC did not hear from that vendor. Please contact the vendor directly. Apache ====== None of the beta releases of Apache for Win32 are vulnerable to this particular problem. Microsoft ========= Microsoft IIS 4.0 and PWS 4.0 with the appropriate patch are not vulnerable. IIS 4.0 and PWS 4.0 maintain certain configuration information about directories and files in a database called the metabase. The metabase does not contain file permissions, but rather Web server-specific information such as requiring SSL encryption, proxy cache setting, and PICS ratings. Actual file and directory permissions are enforced by NTFS and are not affected by this problem. Earlier version of IIS and PWS are not vulnerable to this issue. Microsoft has made available a market bulletin for this issue that is available on "Advisories and Solutions" section of the Microsoft Security Advisor web site, http://www.microsoft.com/security. Please consult this bulletin for information on obtaining the patch. National Center for Supercomputing Applications (NCSA) ====================================================== The NCSA HTTPd web server does not run on Windows NT. Note that HTTPd is now an unsupported software product of the National Center for Supercomputing Applications. - ----------------------------------------------------------------------------- The CERT Coordination Center thanks David LeBlanc for his workaround suggestion. - ----------------------------------------------------------------------------- If you believe that your system has been compromised, contact the CERT Coordination Center or your representative in the Forum of Incident Response and Security Teams (see http://www.first.org/team-info/). CERT/CC Contact Information - ---------------------------- Email cert@cert.org Phone +1 412-268-7090 (24-hour hotline) CERT personnel answer 8:30-5:00 p.m. EST(GMT-5) / EDT(GMT-4) and are on call for emergencies during other hours. Fax +1 412-268-6989 Postal address CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh PA 15213-3890 USA Using encryption We strongly urge you to encrypt sensitive information sent by email. We can support a shared DES key or PGP. Contact the CERT/CC for more information. Location of CERT PGP key ftp://ftp.cert.org/pub/CERT_PGP.key Getting security information CERT publications and other security information are available from http://www.cert.org/ ftp://ftp.cert.org/pub/ CERT advisories and bulletins are also posted on the USENET newsgroup comp.security.announce To be added to our mailing list for advisories and bulletins, send email to cert-advisory-request@cert.org In the subject line, type SUBSCRIBE your-email-address - --------------------------------------------------------------------------- Copyright 1998 Carnegie Mellon University. Conditions for use, disclaimers, and sponsorship information can be found in http://www.cert.org/legal_stuff.html and ftp://ftp.cert.org/pub/legal_stuff . If you do not have FTP or web access, send mail to cert@cert.org with "copyright" in the subject line. *CERT is registered in the U.S. Patent and Trademark Office. - --------------------------------------------------------------------------- This file: ftp://ftp.cert.org/pub/cert_advisories/CA-98.04.Win32.WebServers http://www.cert.org/pub/alerts.html ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Revision history Feb. 11, 1998 Advisory name change Updates to Solution Section III.B Added Acknowledgment -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBNOHMeHVP+x0t4w7BAQEE0QP/Ym6fI4HPsSJs6hMuZJVM+Gi7yO5uhuDL X4ZrwlPizkyqIysb4oaWMJpsmbCYHD6tTYIOYwfDSJfwI0tUGXsIRy3BYA8lRoMj kNqFJFaLUqmKxy+vsxBv9dG5OFE3xzolm/QMR5YppQLpqYil6aIFW3LeRWRJs/E9 0fbKCqaJIyw= =k7GD -----END PGP SIGNATURE----- ========================FORWARDED TEXT ENDS HERE============================= The National Institute of Standards and Technology (NIST) has established a Federal Computer Incident response Capability (FedCIRC) to assist federal civilians agencies in their incident handling efforts by providing proactive and reactive computer security related services. FedCIRC is a partnership among NIST, the Computer Incident Advisory Capability (CIAC), and the CERT* Coordination Center (CERT/CC). If you believe that your system has been compromised, please contact FedCIRC: Telephone: +1 888 282 0870 Email: fedcirc@fedcirc.gov Web Server: http://www.fedcirc.gov/ * Registered in U.S. Patent and Trademark Office The CERT Coordination Center is part of the Software Engineering Institute. The Software Engineering Institute is sponsored by the U.S. Department of Defense. 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. 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.