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The Red Hat Enterprise Linux operating system must not forward Internet Protocol version 4 (IPv4) source-routed packets by default.


Overview

Finding ID Version Rule ID IA Controls Severity
V-204612 RHEL-07-040620 SV-204612r603261_rule Medium
Description
Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.
STIG Date
Red Hat Enterprise Linux 7 Security Technical Implementation Guide 2021-03-01

Details

Check Text ( C-4736r89028_chk )
Verify the system does not accept IPv4 source-routed packets by default.

# grep net.ipv4.conf.default.accept_source_route /etc/sysctl.conf /etc/sysctl.d/*
net.ipv4.conf.default.accept_source_route = 0

If " net.ipv4.conf.default.accept_source_route " is not configured in the /etc/sysctl.conf file or in the /etc/sysctl.d/ directory, is commented out, or does not have a value of "0", this is a finding.

Check that the operating system implements the accept source route variable with the following command:

# /sbin/sysctl -a | grep net.ipv4.conf.default.accept_source_route
net.ipv4.conf.default.accept_source_route = 0

If the returned line does not have a value of "0", this is a finding.
Fix Text (F-4736r89029_fix)
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.default.accept_source_route = 0

Issue the following command to make the changes take effect:

# sysctl --system