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IBM z/OS permission bits and user audit bits for HFS objects that are part of the Base TCP/IP component must be configured properly.


Overview

Finding ID Version Rule ID IA Controls Severity
V-223602 ACF2-TC-000040 SV-223602r533198_rule Medium
Description
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.
STIG Date
IBM z/OS ACF2 Security Technical Implementation Guide 2022-06-22

Details

Check Text ( C-25275r504770_chk )
From the ISPF Command shell enter:
omvs
At the input line enter:
cd /etc
enter
ls -alW

If the following File permission and user Audit Bits are true, this is not a finding.

/etc/hosts 0744 faf
/etc/protocol 0744 faf
/etc/resolv.conf 0744 faf
/etc/services 0740 faf

cd /usr
ls -alW

If the following file permission and user Audit Bits are true, this is not a finding.

/usr/lpp/tcpip/sbin 0755 faf
/usr/lpp/tcpip/bin 0755 faf

Notes: Some of the files listed above are not used in every configuration. The absence of a file is not considered a finding.

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 (F-25263r504771_fix)
With the assistance of a systems programmer with UID(0) and/or SUPERUSER access, configure the UNIX permission bits and user audit bits on the HFS directories and files for the FTP Server to conform to the specifications in the table below:

BASE TCP/IP HFS Object Security Settings
File Permission Bits User Audit Bits
/etc/hosts 0744 faf
/etc/protocol 0744 faf
/etc/resolv.conf 0744 faf
/etc/services 0740 faf
/usr/lpp/tcpip/sbin 0755 faf
/usr/lpp/tcpip/bin 0755 faf

Some of the files listed above (e.g., /etc/resolv.conf) are not used in every configuration. While the absence of a file is generally not a security issue, the existence of a file that has not been properly secured can often be an issue. Therefore, all directories and files that do exist will have the specified permission and audit bit 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 0744 /etc/hosts
chaudit w=sf,rx+f /etc/hosts
chmod 0744 /etc/protocol
chaudit w=sf,rx+f /etc/protocol
chmod 0744 /etc/resolv.conf
chaudit w=sf,rx+f /etc/resolv.conf
chmod 0740 /etc/services
chaudit w=sf,rx+f /etc/services
chmod 0755 /usr/lpp/tcpip/bin
chaudit w=sf,rx+f /usr/lpp/tcpip/bin
chmod 0755 /usr/lpp/tcpip/sbin
chaudit w=sf,rx+f /usr/lpp/tcpip/sbin