Attributes of z/OS UNIX user accounts used for account modeling must be defined in accordance with security requirements.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-7050	ZUSS0048	SV-7941r5_rule		Medium

Description
Top Secret ACIDs that use z/OS UNIX facilities must be properly defined. If these attributes are not correctly defined, data access or command privilege controls could be compromised.

STIG	Date
z/OS TSS STIG	2018-04-04

Details

Check Text ( C-5462r4_chk )
If this is a classified system, this is not applicable. From a command line issue the following command: Note: One must have appropriate access to perform this command (have the site security officer issue the command) TSS MODIFY STATUS Examine the following option: UNIQUSER Alternately: Refer to the following report produced by the TSS Data Collection: - TSSCMDS.RPT(STATUS) - TSSCMDS.RPT(OMVSUSER) Note: This check applies to any user identifier (ACID) used to model OMVS access on the mainframe. This includes OMVSUSR; MODLUSER, and BPX.UNIQUE.USER. If MODLUSER is specified then UNIQUSER must be specified as “ON”. If user identifier (ACID) used to model OMVS user account is defined as follows, this is not finding. A non-writable HOME directory Shell program specified as “/bin/echo”, or “/bin/false” Note: The shell program must have one of the specified values. The HOME directory must have a value (i.e., not be allowed to default).

Check Text ( C-5462r4_chk )

If this is a classified system, this is not applicable.

From a command line issue the following command:

Note: One must have appropriate access to perform this command (have the site security officer issue the command)

TSS MODIFY STATUS

Examine the following option:
UNIQUSER

Alternately:
Refer to the following report produced by the TSS Data Collection:

- TSSCMDS.RPT(STATUS)
- TSSCMDS.RPT(OMVSUSER)

Note: This check applies to any user identifier (ACID) used to model OMVS access on the mainframe. This includes OMVSUSR; MODLUSER, and BPX.UNIQUE.USER.

If MODLUSER is specified then UNIQUSER must be specified as “ON”.

If user identifier (ACID) used to model OMVS user account is defined as follows, this is not finding.

A non-writable HOME directory
Shell program specified as “/bin/echo”, or “/bin/false”

Note: The shell program must have one of the specified values. The HOME directory must have a value (i.e., not be allowed to default).

Fix Text (F-75871r3_fix)
Use of the OMVS default UID will not be allowed on any classified system. Define the user identifier (ACID) used to model OMVS user account with a non-writable home directory, such as "\" root, and a non-executable, but existing, binary file, "/bin/false" or “/bin/echo.”