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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-204609	RHEL-07-040610	SV-204609r880797_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	2022-12-06

Details

Check Text ( C-4733r880795_chk )
Verify the system does not accept IPv4 source-routed packets. # grep -r net.ipv4.conf.all.accept_source_route /run/sysctl.d/* /etc/sysctl.d/* /usr/local/lib/sysctl.d/* /usr/lib/sysctl.d/* /lib/sysctl.d/* /etc/sysctl.conf 2> /dev/null net.ipv4.conf.all.accept_source_route = 0 If "net.ipv4.conf.all.accept_source_route" 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 accept source route variable with the following command: # /sbin/sysctl -a \| grep net.ipv4.conf.all.accept_source_route net.ipv4.conf.all.accept_source_route = 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.

Check Text ( C-4733r880795_chk )

Verify the system does not accept IPv4 source-routed packets.

# grep -r net.ipv4.conf.all.accept_source_route /run/sysctl.d/* /etc/sysctl.d/* /usr/local/lib/sysctl.d/* /usr/lib/sysctl.d/* /lib/sysctl.d/* /etc/sysctl.conf 2> /dev/null
net.ipv4.conf.all.accept_source_route = 0

If "net.ipv4.conf.all.accept_source_route" 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 accept source route variable with the following command:

# /sbin/sysctl -a | grep net.ipv4.conf.all.accept_source_route
net.ipv4.conf.all.accept_source_route = 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-4733r880796_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.all.accept_source_route = 0 Issue the following command to make the changes take effect: # sysctl -system