A RHEL 9 firewall must employ a deny-all, allow-by-exception policy for allowing connections to other systems.
An XCCDF Rule
Description
<VulnDiscussion>Failure to restrict network connectivity only to authorized systems permits inbound connections from malicious systems. It also permits outbound connections that may facilitate exfiltration of DOD data. RHEL 9 incorporates the "firewalld" daemon, which allows for many different configurations. One of these configurations is zones. Zones can be utilized to a deny-all, allow-by-exception approach. The default "drop" zone will drop all incoming network packets unless it is explicitly allowed by the configuration file or is related to an outgoing network connection.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-257937r991589_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Configure the "firewalld" daemon to employ a deny-all, allow-by-exception with the following commands:
Start by adding the exceptions that are required for mission functionality to the "drop" zone. If SSH access on port 22 is needed, for example, run the following: "sudo firewall-cmd --permanent --add-service=ssh --zone=drop"
Reload the firewall rules to update the runtime configuration from the "--permanent" changes made above:
$ sudo firewall-cmd --reload