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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-253129	TOSS-04-040880	SV-253129r825059_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
Tri-Lab Operating System Stack (TOSS) 4 Security Technical Implementation Guide	2022-08-29

Details

Check Text ( C-56582r825057_chk )
Verify TOSS does not 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-56532r825058_fix)
Configure TOSS 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 then add or update the following line in the appropriate file under "/etc/sysctl.d": net.ipv4.conf.all.send_redirects=0