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

From SLES 12 Security Technical Implementation Guide

Associated with: CCI-000366

SV-92189r3_rule The SUSE operating system must prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being accepted.

Vulnerability discussion

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.

Check content

Verify the SUSE operating system does not respond to IPv4 ICMP echoes sent to a broadcast address. Check the value of the "icmp_echo_ignore_broadcasts" variable with the following command: # sysctl net.ipv4.icmp_echo_ignore_broadcasts net.ipv4.icmp_echo_ignore_broadcasts=1 If the returned line does not have a value of "1" this is a finding.

Fix text

Configure the SUSE operating 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.icmp_echo_ignore_broadcasts=1 Run the following command to apply this value: # sysctl --system

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