_____________________________________________________ The Computer Incident Advisory Capability ___ __ __ _ ___ / | / \ / \___ __|__ /___\ \___ _____________________________________________________ INFORMATION BULLETIN SCO Home Directory Vulnerability September 17, 1993 1115 PDT Number D-24 __________________________________________________________________________ PROBLEM: Home directories for "dos" and "asg" accounts insecure. PLATFORM: Systems using SCO Operating Systems (see list below). DAMAGE: Unauthorized system access, including privileged access. SOLUTION: Apply workaround described below. __________________________________________________________________________ Critical Information about SCO Home Directory Vulnerability CIAC has received information of a vulnerability in SCO Operating Systems that may permit unauthorized access to the "dos" and "asg" accounts. The following SCO products are affected by this vulnerability: SCO UNIX System V/386 Release 3.2 Operating System SCO UNIX System V/386 Release 3.2 Operating System Version 2.0 SCO UNIX System V/386 Release 3.2 Operating System version 4.x SCO UNIX System V/386 Release 3.2 Operating System Version 4.0 with Maintenance Supplement Version 4.1 and/or Version 4.2 SCO Network Bundle Release 4.x SCO Open Desktop Release 1.x SCO Open Desktop Release 2.0 SCO Open Desktop Lite Release 3.0 SCO Open Desktop Release 3.0 SCO Open Server Network System Release 3.0 SCO Open Server Enterprise System Release 3.0 The vulnerability results from the fact that the default home directories for the "dos" and "asg" accounts are /tmp and /usr/tmp respectively, both of which are writeable by all system users. This situation may allow unauthorized users to gain access to these accounts and the files that they own. The access may also be used to gain privileged access to the system. CIAC recommends that sites apply the following workaround to all affected systems: 1. Log onto the system as "root". 2. Choose the following sequence of menu selections from the System Administration Shell, which is invoked by typing "sysadmsh": a. Accounts-->User-->Examine--> [select the "dos" account]-->Identity -->Home directory-->Create-->Path--> [change it to /usr/dos instead of /tmp]-->confirm b. Accounts-->User-->Examine--> [select the "asg" account]-->Identity -->Home directory-->Create-->Path--> [change it to /usr/asg instead of /usr/tmp]-->confirm Sites should also take steps to verify that the "dos" and "asg" accounts have not been compromised. The following command will display recent logins to either of the accounts: last | egrep "dos|asg" Should any login sessions be displayed, it is likely that the system has been compromised. The modification times of the DOS binaries on the system should also be examined for evidence of recent modifications. If any evidence of compromise exists, CIAC strongly recommends that the DOS package of Operating System Extended Utilities be removed and re-installed using custom(ADM). If you have further questions regarding this vulnerability, you may contact SCO Support and ask for more information concerning the "Home Directory Security Vulnerability." SCO may be reached as follows: Electronic mail: support@sco.COM USA/Canada: 6am-5pm Pacific Daylight Time (PDT) ----------- 1-800-347-4381 (voice) 1-408-427-5443 (fax) Pacific Rim, Asia, and Latin American customers: 6am-5pm Pacific ------------------------------------------------ Daylight Time (PDT) 1-408-425-4726 (voice) 1-408-427-5443 (fax) Europe, Middle East, Africa: 9am-5:30pm British Standard Time (BST) ---------------------------- +44 (0)923 816344 (voice) +44 (0)923 817781 (fax) For additional information or assistance, please contact CIAC at (510) 422-8193 or send E-mail to ciac@llnl.gov. FAX messages to (510) 423-8002. Previous CIAC Bulletins and other information are available via anonymous FTP from irbis.llnl.gov (IP address 128.115.19.60). CIAC would like to acknowledge the efforts of both Christopher Durham of the Santa Cruz Operation and the CERT Coordination Center in the resolution of this issue. PLEASE NOTE: Many users outside of the DOE and ESnet 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 by sending email to docserver@first.org with an empty subject line and a message body containing the line: send first-contacts. This document was prepared as an account of work sponsored by an agency of the United States Government. 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