The Photon operating system must not send IPv4 Internet Control Message Protocol (ICMP) redirects.

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.

At the command line, run the following command:

# /sbin/sysctl -a --pattern "net.ipv4.conf.(all|default|eth.*).send_redirects"

Expected result:

net.ipv4.conf.all.send_redirects = 0 net.ipv4.conf.default.send_redirects = 0 net.ipv4.conf.eth0.send_redirects = 0

If the output does not match the expected result, this is a finding.

Note: The number of "ethx" lines returned is dependent on the number of interfaces. Every "ethx" entry must be set to "0".

At the command line, run the following command:

# for SETTING in $(/sbin/sysctl -aN --pattern "net.ipv4.conf.(all|default|eth.*).send_redirects"); do sed -i -e "/^${SETTING}/d" /etc/sysctl.conf;echo $SETTING=0>>/etc/sysctl.conf; done
# /sbin/sysctl --load