The system must not send Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirects.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-72293	RHEL-07-040660	SV-86917r2_rule		Medium

Description
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table, possibly revealing portions of the network topology.

STIG	Date
Red Hat Enterprise Linux 7 Security Technical Implementation Guide	2017-12-14

Details

Check Text ( C-72527r2_chk )
Verify the system does not send IPv4 ICMP redirect messages. Check the value of the "all send_redirects" variables with the following command: # grep 'net.ipv4.conf.all.send_redirects' /etc/sysctl.conf net.ipv4.conf.all.send_redirects=0 If the returned line does not have a value of "0", or a line is not returned, this is a finding.

Fix Text (F-78647r2_fix)
Configure the system to not allow interfaces to perform IPv4 ICMP redirects. Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" (or modify the line to have the required value): net.ipv4.conf.all.send_redirects=0