-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN File Access Issue With Internet Information Server July 9, 1998 15:00 GMT Number I-068 ______________________________________________________________________________ PROBLEM: A vulnerability has been identified that affects Microsoft Internet Information Server (IIS). PLATFORM: Microsoft Internet Information Server (IIS) versions 1.0, 2.0, 3.0, 4.0. Microsoft Peer Web Server version 2.0, 3.0. Microsoft Personal Web Server version 4.0 on Windows NT 4.0 workstation. DAMAGE: Web clients with "read access" have access to read any NTFS file in the IIS v-root directory (virtual root). SOLUTION: Upgrade or apply hotfixes. ______________________________________________________________________________ VULNERABILITY Microsoft urges you to act on this information as soon as ASSESSMENT: possible. ______________________________________________________________________________ [ Start Microsoft Advisory ] Microsoft Security Bulletin (MS98-003) File Access issue with Internet Information Server Last Revision: July 8, 1998 Summary ======= Recently Paul Ashton reported an issue on the NTBugtraq mailing list (http://www.ntbugtraq.com) that affects Microsoft Internet Information Server (IIS). Web clients that connect to IIS can read the contents of any NTFS file in an IIS v-root directory to which they have been granted "read access". They can read these files even if the file is marked for "applications mappings", such as used with Active Server Pages scripts. The purpose of this bulletin is to inform Microsoft customers of this issue, its applicability to Microsoft products, and the availability of countermeasures Microsoft has developed to further secure its customers. Issue ===== The native Microsoft(r) Windows NT(r) file system, NTFS, supports multiple data streams within a file. The main data stream, which stores the primary content has an attribute called $DATA. Accessing this NTFS stream via IIS from a browser may display the contents of a file that is normally set to be acted upon by an Application Mapping. For example, .ASP files are mapped such that they are executed by the Active Server Pages scripting agent on the server, rather than simply returning the contents of a file, as is done with standard .htm files. Normally direct contents of the these script-mapped files should not be returned to the user. However, by requesting the file using the its complete data stream name, a web browser could obtain the contents of the script file. In some cases, the file might contain sensitive information such as embedded passwords or other sensitive "business logic" information. This issue does not give the user, who was able to access the script file, the ability to alter the script on the server, or force the server to run any arbitrary code. The only exposure here is to the plain text contents of the script file. The issue is a result of how IIS parses filenames. The fix involves IIS supporting NTFS alternate data streams by asking Windows NT to canonicalize the filename. For the problem to occur: - The user must know the name of the file - The ACLs on the file must allow the user read access - The file must reside on an NTFS partition Affected Software Versions ========================== - Microsoft Internet Information Server versions 1.0, 2.0, 3.0, 4.0 - Microsoft Peer Web Server versions 2.0, 3.0 - Microsoft Personal Web Server version 4.0 on Windows NT 4.0 Workstation What Microsoft is Doing ======================= The Microsoft Product Security Response Team has produced a hotfix for Microsoft Internet Information Server versions 3.0 and 4.0. Additionally, some administrative workarounds are included below. What customers should do ======================== Microsoft strongly recommends that customers using IIS versions 3.0 and 4.0 should apply the hotfix. Customers running previous versions of IIS should upgrade to a more recent version (3.0 or 4.0). The following hotfixes are available from the Microsoft FTP download server under ftp://ftp.microsoft.com/bussys/IIS/iis-public/fixes/usa/security/ IIS 3.0 (Intel x86) hotfix /iis3-datafix/iis3fixi.exe IIS 3.0 (Alpha) hotfix /iis3-datafix/iis3fixa.exe IIS 4.0 (Intel x86) hotfix /iis4-datafix/iis4fixi.exe IIS 4.0 (Alpha) hotfix /iis4-datafix/iis4fixa.exe As localized versions of this hotfix are produced, they will appear in the respective language directories under ftp://ftp.microsoft.com/bussys/IIS/iis-public/fixes/(lang)/security Administrative workaround ========================= Customers who cannot apply the hot fix can use the following workaround to temporarily address this issue: Normally, web users do not need "read" access to script files, such as .ASP files. They simply need "execute" permissions. Removing "read" access to these files for non-administrative users will remove this exposure. For additional protection, the Application Maps can be modified in IIS 4.0 to take into account the existence of the alternate data streams. More details on this workaround are available in the Microsoft Knowledge Base article Q188806 (see the "More Information" section below for the URL). In addition, the following practices can help to further improve security for your IIS servers: - Periodically review the users and groups who have access to the web server: Review the users and groups and their permissions to ensure that only valid users have the appropriate permissions. - Use auditing to detect for suspicious activity: Apply auditing controls on sensitive files and review these logs periodically to detect suspicious or unauthorized behavior. - Set "read" and "execute" permissions appropriately: ASP and other script files do not need to be readable by users that access them through IIS, rather they need to be executable. Thus, it is advisable to remove "read" access from these files for normal users. More Information ================ Please see the following references for more information related to this issue. - Microsoft Security Bulletin 98-003, File Access issue with Internet Information Server (the web-posted version of this bulletin), http://www.microsoft.com/security/bulletins/ms98-003.htm - Microsoft Knowledge Base article Q188806, NTFS Alternate Data Stream Name of a File May Return Source, http://support.microsoft.com/support/kb/articles/q188/8/06.asp - Microsoft Knowledge Base article Q105763, HOWTO: Use NTFS Alternate Data Streams, http://support.microsoft.com/support/kb/articles/q105/7/63.asp Revisions ========= July 2, 1998: Bulletin Created July 6, 1998: Updated information on the availability of hotfix for IIS 4.0 and Alpha version as well. Added additional information on workaround, and more thorough issue description. July 8, 1998: Updated to include information about localized versions of the hotfix. Updated information about products affected. For additional information on security with Microsoft products, please visit http://www.microsoft.com/security ============================================================================== = THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. (c) 1998 Microsoft and/or its suppliers. All rights reserved. For Terms of Use see http://support.microsoft.com/support/misc/cpyright.asp. [ End Microsoft Advisory ] ______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft for the information contained in this bulletin. ______________________________________________________________________________ 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: +1 925-422-8193 FAX: +1 925-423-8002 STU-III: +1 925-423-2604 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 925-422-8193 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 (925) 423-4753 (28.8K baud) +1 (925) 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-058: SunOS rpc.nisd Vulnerability I-059: SUN ftpd Vulnerability I-060: SGI IRIX OSF/DCE Denial of Service Vulnerability I-061: SGI IRIX mediad(1M) Vulnerability I-062: SGI IRIX BIND DNS named(1M) Vulnerability I-063: RSI BSDI rlogind Vulnerability I-064: SGI IRIX mail(1), rmail(1M), sendmail(1M) Vulnerabilities I-065: SunOS ufsrestore Buller Overflow Vulnerability I-066: Vulnerability in Some Implementations of PKCS#1 I-067: AutoStart 9805 Macintosh Worm Virus -----BEGIN PGP SIGNATURE----- Version: 4.0 Business Edition iQCVAwUBNaUyV7nzJzdsy3QZAQGgqAP+NXL+oMKXYGH+F9ryLDk1sG0pSB9GJXcP BTJQpXLsY7yCFugaBTWmIMSbSSO+MW99BRO/fmDAseugjIE+P9G04TU6ddlon+4M 8vpczL9Bbfz2bE4WkYUFilb0gl6IJ88EDOmmr112AqKQc22cIk5aj7yy2kNLiRCc LM14eR8XSl8= =gcxE -----END PGP SIGNATURE-----