OL08-00-040284 - OL 8 must disable the use of user namespaces.

Information

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors.

User namespaces are used primarily for Linux containers. "Rootful" containers run with root privileges on the host system and may pose a security risk if compromised. "Rootless" containers run without root privileges and allow for better isolation from the host system. The value "0" disallows the use of user namespaces. When containers are not in use, namespaces should be disallowed. When privileged user namespaces or "rootful" containers are in use, user namespaces should be disallowed. When unprivileged user namespaces or "rootless" containers are deployed on a system, the value should be set to a large non-zero value. The default value depends on the amount of memory in the system, approximately the total memory in kilobytes divided by 256.

The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographic order, regardless of which of the directories they reside in. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored.
/etc/sysctl.d/*.conf
/run/sysctl.d/*.conf
/usr/local/lib/sysctl.d/*.conf
/usr/lib/sysctl.d/*.conf
/lib/sysctl.d/*.conf
/etc/sysctl.conf

Solution

Configure the system to disable the use of user namespaces by adding the following line to a file in the "/etc/sysctl.d" directory:

user.max_user_namespaces = 0

Remove any configurations that conflict with the above from the following locations:

/run/sysctl.d/*.conf
/usr/local/lib/sysctl.d/*.conf
/usr/lib/sysctl.d/*.conf
/lib/sysctl.d/*.conf
/etc/sysctl.conf
/etc/sysctl.d/*.conf

The system configuration files must be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

Item Details

Audit Name: DISA Oracle Linux 8 STIG v2r4

Category: CONFIGURATION MANAGEMENT

Plugin: Unix

Control ID: 35815f418faea86bd3b46724c848d47825604e94917a3e24f3c7b2e10c1ba49d

Detections

Analytics

OL08-00-040284 - OL 8 must disable the use of user namespaces.

Information

Solution

See Also

Item Details