Title

IBM z/OS HFS objects for the z/OS UNIX Telnet Server must be properly protected. (Cat II impact)

Discussion

To mitigate the risk of unauthorized access to sensitive information by entities that have been issued certificates by DoD-approved PKIs, all DoD systems (e.g., web servers and web portals) must be properly configured to incorporate access control methods that do not rely solely on the possession of a certificate for access. Successful authentication must not automatically give an entity access to an asset or security boundary. Authorization procedures and controls must be implemented to ensure each authenticated entity also has a validated and current authorization. Authorization is the process of determining whether an entity, once authenticated, is permitted to access a specific asset. Information systems use access control policies and enforcement mechanisms to implement this requirement. Access control policies include: identity-based policies, role-based policies, and attribute-based policies. Access enforcement mechanisms include: access control lists, access control matrices, and cryptography. These policies and mechanisms must be employed by the application to control access between users (or processes acting on behalf of users) and objects (e.g., devices, files, records, processes, programs, and domains) in the information system. Satisfies: SRG-OS-000080-GPOS-00048, SRG-OS-000259-GPOS-00100

Check Content

From the ISPF Command shell enter: omvs At the input line enter: cd /usr enter ls -alW If the following File permission and user Audit Bits are true, this is not a finding. /usr/sbin/otelnetd 1740 fff cd /etc ls -alW If the following file permission and user Audit Bits are true this is not a finding. /etc/banner 0744 faf The following represents a hierarchy for permission bits from least restrictive to most restrictive: 7 rwx (least restrictive) 6 rw- 3 -wx 2 -w- 5 r-x 4 r-- 1 --x 0 --- (most restrictive) The possible audit bits settings are as follows: f log for failed access attempts a log for failed and successful access - no auditing

Fix Text

With the assistance of a systems programmer with UID(0) and/or SUPERUSER access, will review the UNIX permission bits and user audit bits on the HFS directories and files for the z/OS UNIX Telnet Server. Ensure they conform to the specifications below: z/OS UNIX TELNET Server HFS Object Security Settings File Permission Bits User Audit Bits /usr/sbin/otelnetd 1740 fff /etc/banner 0744 faf NOTE: The /usr/sbin/otelnetd object is a symbolic link to /usr/lpp/tcpip/sbin/otelnetd. The permission and user audit bits on the target of the symbolic link must have the required settings. The following represents a hierarchy for permission bits from least restrictive to most restrictive: 7 rwx (least restrictive) 6 rw- 3 -wx 2 -w- 5 r-x 4 r-- 1 --x 0 --- (most restrictive) The possible audit bits settings are as follows: f log for failed access attempts a log for failed and successful access - no auditing The following commands can be used (from a user account with an effective UID(0)) to update the permission bits and audit bits: chmod 1740 /usr/lpp/tcpip/sbin/otelnetd chaudit rwx=f /usr/lpp/tcpip/sbin/otelnetd chmod 0744 /etc/banner chaudit w=sf,rx+f /etc/banner

Additional Identifiers

Rule ID: SV-223640r958472_rule

Vulnerability ID: V-223640

Group Title: SRG-OS-000080-GPOS-00048

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.