From z/OS ACF2 STIG
Part of ITNT0020
Associated with IA controls: DCCS-1, DCCS-2
Associated with: CCI-000366
After a connection from a Telnet client to the TN3270 Telnet Server has been established, the process of session setup with a VTAM application occurs. A number of BEGINVTAM statements must be coded in a specific configuration to ensure adequate control to VTAM applications is maintained. Failure to code the appropriate statements could result in unauthorized access to the host and application resources. This exposure may impact data integrity or the availability of some system services.
a) Refer to the Profile configuration file specified on the PROFILE DD statement in the TCPIP started task JCL. Automated Analysis requires Additional Analysis Refer to the following report produced by the IBM Communications Server Data Collection: - PDI(ITNT0020) b) Ensure the following items are in effect for the configuration statements specified in the TCP/IP Profile configuration file: 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. 1) 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. 2) 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. 3) 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. 4) 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. 5) 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. c) If all of the above are true, there is NO FINDING. d) If any of the above is untrue, this is a FINDING.
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 TCP/IP 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 For z/OS systems, 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. Further explanation: After a connection from a Telnet client to the TN3270 Telnet Server has been established, the process of session setup with a VTAM application occurs. A number of BEGINVTAM statements will be coded in a specific configuration to ensure that adequate control over access to VTAM applications is maintained. Connections originate from secure terminals or unsecured terminals. The TN3270 Telnet Server should be configured to address these two types of connections. Terminals should meet two conditions to be considered secure. One condition involves the hardware and configuration. Secure terminals include devices that are directly attached to the host, such as 3270-type terminals coax connected to a 3174 Control Unit. They also include PCs running 3270 terminal emulation clients attached to a private LAN (i.e., a LAN without access to an external network such as the NIPRNet). The other condition involves the location of the terminals. Secure terminals are located in areas with physical access limited to authorized personnel. Examples of terminals that are not secure are those attached via the NIPRNet or via dial-in servers. The intent of this distinction is to allow additional connection options (e.g., bypassing session manager control) to authorized personnel working in controlled access areas. These connection options may be necessary for operational control or for system recovery procedures. The BEGINVTAM USSTCP statement can be used to specify a customized Unformatted System Services (USS) table for client connections. The USS table can provide a level of access control by restricting the commands that allow connections to VTAM applications. The USS table specified by the USSTCP statement can be the same as the one used by the SNA component of IBM Communications Server. The BEGINVTAM DEFAULTAPPL statement can be used to specify the VTAM application to which a client is automatically connected when a session is established using a protocol other than linemode protocol. The BEGINVTAM LUMAP statement can specify a default VTAM application using the DEFAPPL operand. This processing is similar to the DEFAULTAPPL and LINEMODEAPPL processing, except that a client identifier should be coded. When a client matches the LUMAP specification, the DEFAPPL specification overrides the DEFAULTAPPL or LINEMODEAPPL specifications.
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