RHEL 8 must use reverse path filtering on all IPv4 interfaces.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-230549	RHEL-08-040285	SV-230549r599732_rule		Medium

Description

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. Enabling reverse path filtering drops packets with source addresses that are not routable. There is not an equivalent filter for IPv6 traffic.

STIG	Date
Red Hat Enterprise Linux 8 Security Technical Implementation Guide	2020-11-25

Details

Check Text ( C-33218r568393_chk )
Verify RHEL 8 uses reverse path filtering on all IPv4 interfaces with the following commands: $ sudo sysctl net.ipv4.conf.all.rp_filter net.ipv4.conf.all.rp_filter = 1 If the returned line does not have a value of "1", or a line is not returned, this is a finding.

Fix Text (F-33193r568394_fix)
Configure RHEL 8 to use reverse path filtering on all IPv4 interfaces by adding the following line to a file in the "/etc/sysctl.d" directory: net.ipv4.conf.all.rp_filter = 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