IBM z/OS UNIX security parameters in /etc/rc must be properly specified.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-223618	SRG-OS-000080-GPOS-00048	ACF2-US-000030	SV-223618r958472_rule	2025-03-11	9

Description
Configuring the operating system to implement organization-wide security implementation guides and security checklists ensures compliance with federal standards and establishes a common security baseline across DoD that reflects the most restrictive security posture consistent with operational requirements.

ℹ️ Check
From the ISPF COMMAND SHELL enter: ISHELL /etc/rc If all of the CHMOD commands in /etc/rc do not result in less restrictive access than what is specified in the tables below, this is not a finding. NOTE: The use of CHMOD commands in /etc/rc is required in most environments to comply with the required settings, especially for dynamic objects such as the /dev directory. 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) If all of the CHAUDIT commands in /etc/rc do not result in less auditing than what is specified in the tables below this is not a finding. NOTE: The use of CHAUDIT commands in /etc/rc may not be necessary. If none are found, there is not a finding. The possible audit bits settings are as follows: f log for failed access attempts a log for failed and successful access - no auditing Directory Permission Bits User Audit Bits Function / [root] 755 faf Root level of all file systems. Holds critical mount points. /bin 1755 fff Shell scripts and executables for basic functions /dev 1755 fff Character-special files used when logging into the OMVS shell and during C language program compilation. Files are created during system IPL and on a per-demand basis. /etc 1755 faf Configuration programs and files (usually with locally customized data) used by z/OS UNIX and other product initialization processes /lib 1755 fff System libraries including dynamic link libraries and files for static linking /samples 1755 fff Sample configuration and other files /tmp 1777 fff Temporary data used by daemons, servers, and users. Note: /tmp must have the sticky bit on to restrict file renames and deletions. /u 1755 fff Mount point for user home directories and optionally for third-party software and other local site files /usr 1755 fff Shell scripts, executables, help (man) files and other data. Contains sub-directories (e.g., lpp) and mount points used by program products that may be in separate file systems. /var 1775 fff Dynamic data used internally by products and by elements and features of z/OS UNIX.

ℹ️ Check

From the ISPF COMMAND SHELL enter: ISHELL /etc/rc If all of the CHMOD commands in /etc/rc do not result in less restrictive access than what is specified in the tables below, this is not a finding. NOTE: The use of CHMOD commands in /etc/rc is required in most environments to comply with the required settings, especially for dynamic objects such as the /dev directory. 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) If all of the CHAUDIT commands in /etc/rc do not result in less auditing than what is specified in the tables below this is not a finding. NOTE: The use of CHAUDIT commands in /etc/rc may not be necessary. If none are found, there is not a finding. The possible audit bits settings are as follows: f log for failed access attempts a log for failed and successful access - no auditing Directory Permission Bits User Audit Bits Function / [root] 755 faf Root level of all file systems. Holds critical mount points. /bin 1755 fff Shell scripts and executables for basic functions /dev 1755 fff Character-special files used when logging into the OMVS shell and during C language program compilation. Files are created during system IPL and on a per-demand basis. /etc 1755 faf Configuration programs and files (usually with locally customized data) used by z/OS UNIX and other product initialization processes /lib 1755 fff System libraries including dynamic link libraries and files for static linking /samples 1755 fff Sample configuration and other files /tmp 1777 fff Temporary data used by daemons, servers, and users. Note: /tmp must have the sticky bit on to restrict file renames and deletions. /u 1755 fff Mount point for user home directories and optionally for third-party software and other local site files /usr 1755 fff Shell scripts, executables, help (man) files and other data. Contains sub-directories (e.g., lpp) and mount points used by program products that may be in separate file systems. /var 1775 fff Dynamic data used internally by products and by elements and features of z/OS UNIX.

✔️ Fix
Review the settings in the /etc/rc. The /etc/rcfile is the system initialization shell script. When z/OS UNIX kernel services start, /etc/rc is executed to set file permissions and ownership for dynamic system files and to perform other system startup functions such as starting daemons. There can be many commands in /etc/rc. There are two specific guidelines that must be followed: -Verify that the CHMOD or CHAUDIT command does not result in less restrictive security than what is specified in the table below. -Immediately prior to each command that starts a daemon, the _BPX_JOBNAME variable must be set to match the daemon's name (e.g., inetd, syslogd). The use of _BPX_USERID is at the site's discretion, but is recommended. Directory Permission Bits User Audit Bits Function / [root] 755 faf Root level of all file systems. Holds critical mount points. /bin 1755 fff Shell scripts and executables for basic functions /dev 1755 fff Character-special files used when logging into the OMVS shell and during C language program compilation. Files are created during system IPL and on a per-demand basis. /etc 1755 faf Configuration programs and files (usually with locally customized data) used by z/OS UNIX and other product initialization processes /lib 1755 fff System libraries including dynamic link libraries and files for static linking /samples 1755 fff Sample configuration and other files /tmp 1777 fff Temporary data used by daemons, servers, and users. Note: /tmp must have the sticky bit on to restrict file renames and deletions. /u 1755 fff Mount point for user home directories and optionally for third-party software and other local site files /usr 1755 fff Shell scripts, executables, help (man) files and other data. Contains sub-directories (e.g., lpp) and mount points used by program products that may be in separate file systems. /var 1775 fff Dynamic data used internally by products and by elements and features of z/OS UNIX.

✔️ Fix

Review the settings in the /etc/rc. The /etc/rcfile is the system initialization shell script. When z/OS UNIX kernel services start, /etc/rc is executed to set file permissions and ownership for dynamic system files and to perform other system startup functions such as starting daemons. There can be many commands in /etc/rc. There are two specific guidelines that must be followed: -Verify that the CHMOD or CHAUDIT command does not result in less restrictive security than what is specified in the table below. -Immediately prior to each command that starts a daemon, the _BPX_JOBNAME variable must be set to match the daemon's name (e.g., inetd, syslogd). The use of _BPX_USERID is at the site's discretion, but is recommended. Directory Permission Bits User Audit Bits Function / [root] 755 faf Root level of all file systems. Holds critical mount points. /bin 1755 fff Shell scripts and executables for basic functions /dev 1755 fff Character-special files used when logging into the OMVS shell and during C language program compilation. Files are created during system IPL and on a per-demand basis. /etc 1755 faf Configuration programs and files (usually with locally customized data) used by z/OS UNIX and other product initialization processes /lib 1755 fff System libraries including dynamic link libraries and files for static linking /samples 1755 fff Sample configuration and other files /tmp 1777 fff Temporary data used by daemons, servers, and users. Note: /tmp must have the sticky bit on to restrict file renames and deletions. /u 1755 fff Mount point for user home directories and optionally for third-party software and other local site files /usr 1755 fff Shell scripts, executables, help (man) files and other data. Contains sub-directories (e.g., lpp) and mount points used by program products that may be in separate file systems. /var 1775 fff Dynamic data used internally by products and by elements and features of z/OS UNIX.