Title

CA-TSS permission bits and user audit bits for HFS objects that are part of the FTP server component must be properly configured. (Cat II impact)

Discussion

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.

Check Content

From the ISPF Command Shell enter: omvs At the input line enter: cd /usr/sbin/ enter ls -alW If the following File permission and user Audit Bits are true, this is not a finding. /usr/sbin/ftpd 1740 fff /usr/sbin/ftpdns 1755 fff /usr/sbin/tftpd 0644 faf cd ls -alW If the following file permission and user Audit Bits are true, this is not a finding. /etc/ftp.data 0744 faf /etc/ftp.banner 0744 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 /usr/sbin/ftpd and /usr/sbin/ftpdns objects are symbolic links to /usr/lpp/tcpip/sbin/ftpd and /usr/lpp/tcpip/sbin/ftpdns respectively. The permission and user audit bits on the targets of the symbolic links must have the required settings. The /etc/ftp.data file may not be the configuration file the server uses. It is necessary to check the SYSFTPD DD statement in the FTP started task JCL to determine the actual file. The TFTP Server does not perform any user identification or authentication, allowing any client to connect to the TFTP Server. Due to this lack of security, the TFTP Server will not be used. The TFTP Client is not secured from use. The permission bits for /usr/sbin/tftpd should be set to 644. The /etc/ftp.banner file may not be the banner file the server uses. It is necessary to check the BANNER statement in the FTP Data configuration file to determine the actual file. Also, the permission bit setting for this file must be set as indicated in the table above. A more restrictive set of permissions is not permitted. 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

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: FTP Server HFS Object Security Settings File Permission Bits User Audit Bits /usr/sbin/ftpd 1740 fff /usr/sbin/ftpdns 1755 fff /usr/sbin/tftpd 0644 faf /etc/ftp.data 0744 faf /etc/ftp.banner 0744 faf The /usr/sbin/ftpd and /usr/sbin/ftpdns objects are symbolic links to /usr/lpp/tcpip/sbin/ftpd and /usr/lpp/tcpip/sbin/ftpdns respectively. The permission and user audit bits on the targets of the symbolic links must have the required settings. The TFTP Server does not perform any user identification or authentication, allowing any client to connect to the TFTP Server. Due to this lack of security, the TFTP Server will not be used. The TFTP Client is not secured from use. The /etc/ftp.data file may not be the configuration file the server uses. It is necessary to check the SYSFTPD DD statement in the FTP started task JCL to determine the actual file. The /etc/ftp.banner file may not be the banner file the server uses. It is necessary to check the BANNER statement in the FTP Data configuration file to determine the actual file. 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 Some of the files listed above (e.g., /etc/ftp.data) 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 files that do exist should have the specified permission and audit bit settings. The following commands can be used (from a user account with an effective UID(0)) to update the permission bits and audit bits: chmod 1740 /usr/lpp/tcpip/sbin/ftpd chaudit rwx=f /usr/lpp/tcpip/sbin/ftpd chmod 1755 /usr/lpp/tcpip/sbin/ftpdns chaudit rwx=f /usr/lpp/tcpip/sbin/ftpdns chmod 0744 /etc/ftp.data chaudit w=sf,rx+f /etc/ftp.data chmod 0744 /etc/ftp.banner chaudit w=sf,rx+f /etc/ftp.banner

Additional Identifiers

Rule ID: SV-223975r958472_rule

Vulnerability ID: V-223975

Group Title: SRG-OS-000080-GPOS-00048

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.