The SUSE operating system must prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being accepted.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-235018	SLES-15-040330	SV-235018r622137_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 modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.

STIG	Date
SUSE Linux Enterprise Server 15 Security Technical Implementation Guide	2021-03-04

Details

Check Text ( C-38206r619323_chk )
Verify the SUSE operating system does not accept IPv4 ICMP redirect messages. Check the value of the IPv4 accept_redirects variable with the following command: > sudo sysctl net.ipv4.conf.all.accept_redirects net.ipv4.conf.all.accept_redirects =0 If the network parameter "ipv4.conf.all.accept_redirects" is not equal to "0" or nothing is returned, this is a finding.

Fix Text (F-38169r619324_fix)
Configure the SUSE operating system to not accept IPv4 ICMP redirect messages by running the following command as an administrator: > sudo sysctl -w net.ipv4.conf.all.accept_redirects=0 If "0" is not the system's default value, add or update the following line in "/etc/sysctl.d/99-stig.conf": > sudo sh -c 'echo "net.ipv4.conf.all.accept_redirects=0" >> /etc/sysctl.d/99-stig.conf' > sudo sysctl --system

Fix Text (F-38169r619324_fix)

Configure the SUSE operating system to not accept IPv4 ICMP redirect messages by running the following command as an administrator:

> sudo sysctl -w net.ipv4.conf.all.accept_redirects=0

If "0" is not the system's default value, add or update the following line in "/etc/sysctl.d/99-stig.conf":

> sudo sh -c 'echo "net.ipv4.conf.all.accept_redirects=0" >> /etc/sysctl.d/99-stig.conf'

> sudo sysctl --system