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The Red Hat Enterprise Linux operating 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-204617 RHEL-07-040660 SV-204617r880821_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 2022-12-06

Details

Check Text ( C-4741r880819_chk )
Verify the system does not send IPv4 ICMP redirect messages.

# grep -r net.ipv4.conf.all.send_redirects /run/sysctl.d/* /etc/sysctl.d/* /usr/local/lib/sysctl.d/* /usr/lib/sysctl.d/* /lib/sysctl.d/* /etc/sysctl.conf 2> /dev/null

If "net.ipv4.conf.all.send_redirects" is not configured in the /etc/sysctl.conf file or in any of the other sysctl.d directories, is commented out or does not have a value of "0", this is a finding.

Check that the operating system implements the "all send_redirects" variables with the following command:

# /sbin/sysctl -a | grep net.ipv4.conf.all.send_redirects
net.ipv4.conf.all.send_redirects = 0

If the returned line does not have a value of "0", this is a finding.

If conflicting results are returned, this is a finding.
Fix Text (F-4741r880820_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 a configuration file in the /etc/sysctl.d/ directory (or modify the line to have the required value):

net.ipv4.conf.all.send_redirects = 0

Issue the following command to make the changes take effect:

# sysctl --system