CA-92:16 CERT Advisory September 22, 1992 VMS Monitor Vulnerability --------------------------------------------------------------------------- The CERT Coordination Center has received information concerning a potential vulnerability with Digital Equipment Corporation's VMS Monitor. This vulnerability is present in V5.0 through V5.4-2 but has been corrected in V5.4-3 through V5.5-1. The Software Security Response Team at Digital has provided the following information concerning this vulnerability. NOTE: Digital suggests that customers who are unable to upgrade their systems implement the workaround described below. For additional information, please contact your local Digital Equipment Corporation customer service representative. Beginning of Text provided by Digital Equipment Corporation ============================================================================== SSRT-0200 PROBLEM: Potential Security Vulnerability Identified in Monitor SOURCE: Digital Equipment Corporation AUTHOR: Software Security Response Team - U.S. Colorado Springs USA PRODUCT: VMS Symptoms Identified On: VMS, Versions 5.0, 5.0-1, 5.0-2, 5.1, 5.1-B, 5.1-1, 5.1-2, 5.2, 5.2-1, 5.3, 5.3-1, 5.3-2, 5.4, 5.4-1, 5.4-2 ******************************************************* SOLUTION: This problem is not present in VMS V5.4-3 (released in October 1991) through V5.5-1 (released in July, 1992.) ******************************************************* Copyright (c) Digital Equipment Corporation, 1992 All Rights Reserved. Published Rights Reserved Under The Copyright Laws Of The United States. ------------------------------------------------------------------------------- PROBLEM/IMPACT: ------------------------------------------------------------------------------- Unauthorized privileges may be expanded to authorized users of a system under certain conditions, via the Monitor utility. Should a system be compromised through unauthorized access, there is a risk of potential damage to a system environment. This problem will not permit unauthorized access entry, as individuals attempting to gain unauthorized access will continue to be denied through the standard VMS security mechanisms. ------------------------------------------------------------------------------- SOLUTION: ------------------------------------------------------------------------------- This potential vulnerability does not exist in VMS V5.4-3 (released in October 1991) and later versions of VMS through V5.5-1. Digital strongly recommends that you upgrade to a minimum of VMS V5.4-3, and further, to the latest release of VMS V5.5-1. (released in July, 1992) ------------------------------------------------------------------------------ INFORMATION: ------------------------------------------------------------------------------- If you cannot upgrade at this time Digital recommends that you implement a workaround (examples attached below) to avoid any potential vulnerability. As always, Digital recommends that you periodically review your system management and security procedures. Digital will continue to review and enhance the security features of its products and work with customers to maintain and improve the security and integrity of their systems. ------------------------------------------------------------------------------- WORKAROUND ------------------------------------------------------------------------------- A suggested workaround would be to remove the installed image SYS$SHARE:SPISHR.EXE via VMS INSTALL and/or restrict the use of the MONITOR utility to "privileged" system administrators. Below are the examples of doing both; [1] To disable the MONITOR utility the image SYS$SHARE:SPISHR.EXE should be deinstalled. From a privileged account; For cluster configurations; --------------------------- $ MC SYSMAN SYSMAN> SET ENVIRONMENT/CLUSTER SYSMAN> DO INSTALL REMOVE SYS$SHARE:SPISHR.EXE SYSMAN> DO RENAME SYS$SHARE:SPISHR.EXE SPISHR.HOLD SYSMAN> EXIT For non-VAXcluster configurations; --------------------------------- $INSTALL INSTALL>REMOVE SYS$SHARE:SPISHR.EXE INSTALL>EXIT $RENAME SYS$SHARE:SPISHR.EXE SPISHR.HOLD [2] If you wish to restrict access to the MONITOR command so that only a limited number of authorized (or privileged) persons are granted access to the utility, one method might be to issue the following example commands; From a privileged account; For cluster configurations; --------------------------- $ MC SYSMAN SYSMAN> SET ENVIRONMENT/CLUSTER SYSMAN> DO INSTALL REMOVE SYS$SHARE:SPISHR.EXE SYSMAN> DO SET FILE/ACL=(ID=*,ACCESS=NONE) SYS$SHARE:SPISHR.EXE SYSMAN> DO SET FILE/ACL=(ID=SYSTEM,ACCESS=READ+EXECUTE) SYS$SHARE:SPISHR.EXE SYSMAN> DO INSTALL ADD SYS$SHARE:SPISHR.EXE/OPEN/HEADER/SHARE/PROTECT SYSMAN> EXIT $ THIS WILL IMPACT the MONITOR UTILITY FOR REMOTE MONITORING. LOCAL MONITORING WILL CONTINUE TO WORK FOR PERSONS HOLDING THE ID's GRANTED ACL ACCESS. see additional note(s) below For non-VAXcluster configurations; ---------------------------------- $ INSTALL INSTALL>REMOVE SYS$SHARE:SPISHR.EXE INSTALL>EXIT $ SET FILE /ACL=(ID=*,ACCESS=NONE) SYS$SHARE:SPISHR.EXE $ SET FILE /ACL=(ID=SYSTEM,ACCESS=READ+EXECUTE) SYS$SHARE:SPISHR.EXE $ INSTALL INSTALL>ADD SYS$SHARE:SPISHR.EXE/OPEN/HEADER/SHARE/PROTECT INSTALL>EXIT $ IN THE ABOVE EXAMPLES, THE "SET FILE /ACL" LINE SHOULD BE REPEATED FOR ALL ACCOUNTS THAT ARE REQUIRED/ALLOWED TO USE THE DCL MONITOR COMMAND. NOTE: The ID -SYSTEM- is an example, and should be substituted as necessary with valid user ID's that are associated with accounts you wish to grant access to. =========================================================================== End of Text provided by Digital Equipment Corporation --------------------------------------------------------------------------- CERT wishes to thank Teun Nijssen of CERT-NL (the SURFnet CERT, in the Netherlands) for bringing this security vulnerability to our attention. We would also like to thank Digital Equipment Corporation's Software Security Response Team for providing information on this vulnerability. --------------------------------------------------------------------------- If you believe that your system has been compromised, contact CERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet E-mail: cert@cert.org Telephone: 412-268-7090 (24-hour hotline) CERT personnel answer 7:30 a.m.-6:00 p.m. EST(GMT-5)/EDT(GMT-4), on call for emergencies during other hours. CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh, PA 15213-3890 Past advisories, information about FIRST representatives, and other information related to computer security are available for anonymous ftp from cert.org (192.88.209.5).