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IBM z/OS VTAM session setup controls for the TN3270 Telnet Server must be properly specified.


Overview

Finding ID Version Rule ID IA Controls Severity
V-223613 ACF2-TN-000060 SV-223613r533198_rule Medium
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. Configuration settings are the set of parameters that can be changed in hardware, software, or firmware components of the system that affect the security posture and/or functionality of the system. Security-related parameters are those parameters impacting the security state of the system, including the parameters required to satisfy other security control requirements. Security-related parameters include, for example: registry settings; account, file, directory permission settings; and settings for functions, ports, protocols, services, and remote connections.
STIG Date
IBM z/OS ACF2 Security Technical Implementation Guide 2022-06-22

Details

Check Text ( C-25286r504800_chk )
Refer to the TN3270 Profile configuration file identified by the PROFILE DD into the TN3270 procedure.

NOTE: If the INCLUDE statement is coded in the TCP/IP Profile configuration file, the data set specified on this statement must be checked for the following items as well.

If all of the following are true, this is not a finding.

If any of the following is untrue, this is a finding

-Within each BEGINVTAM statement block, one BEGINVTAM USSTCP statement is coded that specifies only the table name operand. No client identifier, such as host name or IP address, is specified so the statement applies to all connections not otherwise controlled.
-The USS table specified on each “back stop” USSTCP statement mentioned in Item (1) above is coded to allow access only to session manager applications and NC PASS applications.
-Within each BEGINVTAM statement block, additional BEGINVTAM USSTCP statements that specify a USS table that allows access to other applications may be coded only if the statements include a client identifier operand that references only secure terminals.
-Any BEGINVTAM DEFAULTAPPL statement that does not specify a client identifier, or specifies any type of client identifier that would apply to unsecured terminals, specifies a session manager application or an NC PASS application as the application name.
-Any BEGINVTAM LUMAP statement, if used with the DEFAPPL operand and applied to unsecured terminals, specifies only a session manager application or an NC PASS application.

NOTE: The BEGINVTAM LINEMODEAPPL requirements will not be reviewed at this time. Further testing must be performed to determine how the CL/Supersession and NC-PASS applications work with line mode.
Fix Text (F-25274r504801_fix)
Review the BEGINVTAM configuration statements in the PROFILE.TCPIP file. Ensure they conform to the specifications below.

NOTE: If the INCLUDE statement is coded in the TN3270 Profile configuration file, the data set specified on this statement must be checked for the following items as well.

Within each BEGINVTAM statement block, one BEGINVTAM USSTCP statement is coded that specifies only the table name operand. No client identifier, such as host name or IP address, is specified so the statement applies to all connections not otherwise controlled.

The USS table specified on each “back stop” USSTCP statement mentioned above is coded to allow access only to session manager applications and NC PASS applications

Within each BEGINVTAM statement block, additional BEGINVTAM USSTCP statements that specify a USS table that allows access to other applications may be coded only if the statements include a client identifier operand that references only secure terminals.

Any BEGINVTAM DEFAULTAPPL statement that does not specify a client identifier, or specifies any type of client identifier that would apply to unsecured terminals, specifies a session manager application or an NC PASS application as the application name.