OL 8 must not send Internet Control Message Protocol (ICMP) redirects.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-248877	OL08-00-040220	SV-248877r780197_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. There are notable differences between Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6). There is only a directive to disable sending of IPv4 redirected packets. Refer to RFC4294 for an explanation of "IPv6 Node Requirements", which resulted in this difference between IPv4 and IPv6.

STIG	Date
Oracle Linux 8 Security Technical Implementation Guide	2021-07-21

Details

Check Text ( C-52311r780195_chk )
Verify OL 8 does not send IPv4 ICMP redirect messages. Note: If IPv4 is disabled on the system, this requirement is not applicable. Check the value of the "all send_redirects" variables with the following command: $ sudo sysctl net.ipv4.conf.all.send_redirects 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-52265r780196_fix)
Configure OL 8 to not allow interfaces to perform IPv4 ICMP redirects with the following command: $ sudo sysctl -w net.ipv4.conf.all.send_redirects=0 If "0" is not the system's default value, add or update the following line in "/etc/sysctl.conf" or in the appropriate file under "/etc/sysctl.d": net.ipv4.conf.all.send_redirects=0