RHEL-08-040281 - RHEL 8 must disable access to network bpf syscall from unprivileged processes.

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.

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 RHEL 8 to prevent privilege escalation thru the kernel by disabling access to the bpf syscall by adding the following line to a file, in the '/etc/sysctl.d' directory:

kernel.unprivileged_bpf_disabled = 1

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 need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_RHEL_8_V2R1_STIG.zip

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6b., CAT|II, CCI|CCI-000366, Rule-ID|SV-230545r1017307_rule, STIG-ID|RHEL-08-040281, Vuln-ID|V-230545

Plugin: Unix

Control ID: 63761c95e10b1dc11308813d8f5329fd1ee1c1fabb5bf186ae967dbb6e96b630