RHEL 9 must disable access to network bpf system call from nonprivileged processes.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-257810	RHEL-09-213075	SV-257810r942977_rule		Medium

Description
Loading and accessing the packet filters programs and maps using the bpf() system call has the potential of revealing sensitive information about the kernel state. Satisfies: SRG-OS-000132-GPOS-00067, SRG-OS-000480-GPOS-00227

STIG	Date
Red Hat Enterprise Linux 9 Security Technical Implementation Guide	2023-12-01

Details

Check Text ( C-61551r942976_chk )

Verify RHEL 9 prevents privilege escalation thru the kernel by disabling access to the bpf system call with the following commands: $ sudo sysctl kernel.unprivileged_bpf_disabled kernel.unprivileged_bpf_disabled = 1 If the returned line does not have a value of "1", or a line is not returned, this is a finding. Check that the configuration files are present to enable this kernel parameter. $ sudo /usr/lib/systemd/systemd-sysctl --cat-config | egrep -v '^(#|;)' | grep -F kernel.unprivileged_bpf_disabled | tail -1 kernel.unprivileged_bpf_disabled = 1 If the network parameter "ipv4.tcp_syncookies" is not equal to "1", or nothing is returned, this is a finding.

Fix Text (F-61475r925416_fix)
Configure RHEL 9 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 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