CentOS 8.x firewalld rich rules

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Rich rule processing order

Once multiple rules are in place they will be processed in a certain order. Port forwarding and masquerading rules will be applied first, followed by any logging rules, then any allow rules, and finally any deny rules. A packet will use the first rule it applies to in this order, if it does not match a rule it will hit the default deny.

Basics of rich rules

• Allow httpd connection. The rule will be add to default zone

  firewall-cmd --add-rich-rule 'rule family="ipv4" source address="192.168.0.0/24" service name="http" accept'
  firewall-cmd --add-rich-rule 'rule family="ipv4" source address="192.168.0.0/24" service name="http" accept' --permanent

• Reject httpd connection.

  firewall-cmd --add-rich-rule 'rule family="ipv4" source address="192.168.0.0/24" service name="http" reject'

• Add rich rule to specific zone

  firewall-cmd --zone=home --add-rich-rule 'rule family="ipv4" source address="192.168.0.0/24" service name="http" accept'

• To list the rich rules

  firewall-cmd --permanent --zone=home --list-rich-rule

• Remove rich rule

  firewall-cmd --zone=home --remove-rich-rule 'rule family="ipv4" source address="192.168.0.0/24" service name="http" accept --permanent

• Rich rules can also be used to rate limit traffic, here we limit incoming SSH connections to 10 per minute.

  firewall-cmd --permanent --add-rich-rule='rule service name=ssh limit value=10/m accept'

Some examples for Rich Rule

• Allowing traffic from the range 10.0.0.0/24 into only 192.168.0.10/32 through TCP ports 8080 through to 8090.

  firewall-cmd --permanent --zone=testing --add-rich-rule='rule family=ipv4 source address=10.0.0.0/24 destination address=192.168.0.10/32 port port=8080-8090 protocol=tcp accept' success

• In this instance we can specify a specific source address within the test zone rather than the whole zone.

  firewall-cmd --permanent --zone=testing --add-rich-rule='rule family=ipv4 source address=192.168.1.0/24 forward-port port=22 protocol=tcp to-port=2222 to-addr=10.0.0.10'

Masquerading with Rich rules

• To check if IP masquerading is enabled

  firewall-cmd --zone=public --query-masquerade

• To enable IP masquerading

  firewall-cmd --zone=public --add-masquerade

• In this example any packet sent to addresses defined in the zone ‘testing’ will be masqueraded

  firewall-cmd --permanent --zone=home --add-rich-rule='rule family=ipv4 source address=192.168.1.0/24 masquerade'

Some test cases

• Allow Telnet connection only from 192.168.1.50/32. Limit this connection one per minute. Drop Telnet connection from remaining hosts

  firewall-cmd --add-rich-rule='rule family=ipv4 source address=192.168.1.50/32 service name=telnet limit value=1/m accept'

• Allow SSH connection from network 192.168.1.0/24. Log each access with "SSH Access" prefix"

  firewall-cmd --add-rich-rule='rule family=ipv4 source address=192.168.1.0/24 service name=ssh log prefix="SSH Access" level= "notice" accept'

• Allow FTP connection only from 192.168.1.2/24. Reject FTP connections from remaining systems

  firewall-cmd --add-rich-rule='rule family=ipv4 source address=192.168.1.2/32 port port=21 protocol=tcp  accept'

• Reject ping requests from all hosts with error message.

  firewall-cmd --add-rich-rule='rule protocol value=icmp reject'

Rich rules timeout option

• For testing and debugging purpose we can use --timeout option which will remove the rule automatically after the specified time. For examples Following rule will be automatically removed after 60 seconds

  firewall-cmd --add-rich-rule=’rule protocol value=”icmp” reject’ --timeout=60

Rich Rule Log Command

• Log httpd acess

  firewall-cmd --permanent --remove-rich-rule='rule family="ipv4" source address="192.168.1.50/32" service name="http" log prefix="httpd_" level="debug" accept'

  You can check logs in "/var/log/messages"

Refer:

• https://www.rootusers.com/how-to-use-firewalld-rich-rules-and-zones-for-filtering-and-nat/

Steps contributed by Pavan Ponamala

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