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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-239177	PHTN-67-000106	SV-239177r675339_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
VMware vSphere 6.7 Photon OS Security Technical Implementation Guide	2021-04-15

Details

Check Text ( C-42388r675337_chk )
At the command line, execute the following command: # /sbin/sysctl -a --pattern "net.ipv4.conf.(all\|default\|eth.*).accept_redirects" Expected result: net.ipv4.conf.all.accept_redirects = 0 net.ipv4.conf.default.accept_redirects = 0 net.ipv4.conf.eth0.accept_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".

Check Text ( C-42388r675337_chk )

At the command line, execute the following command:

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

Expected result:

net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.eth0.accept_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".

Fix Text (F-42347r675338_fix)
At the command line, execute the following command: # for SETTING in $(/sbin/sysctl -aN --pattern "net.ipv4.conf.(all\|default\|eth.*).accept_redirects"); do sed -i -e "/^${SETTING}/d" /etc/sysctl.conf;echo $SETTING=0>>/etc/sysctl.conf; done