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The Photon operating system must use a reverse-path filter for IPv4 network traffic.


Overview

Finding ID Version Rule ID IA Controls Severity
V-239181 PHTN-67-000110 SV-239181r816668_rule Medium
Description
Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems that are routers for complicated networks but is helpful for end hosts and routers serving small networks.
STIG Date
VMware vSphere 6.7 Photon OS Security Technical Implementation Guide 2022-06-17

Details

Check Text ( C-42392r675349_chk )
At the command line, execute the following command:

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

Expected result:

net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.eth0.rp_filter = 1

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 "1".
Fix Text (F-42351r816667_fix)
Open /etc/sysctl.conf with a text editor.

Add or update the following lines:

net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.eth0.rp_filter = 1

Run the following command to load the new setting:

# /sbin/sysctl --load