Firewalld

Zones

Pre-defined zones within firewalld are:

  • drop: The lowest level of trust. All incoming connections are dropped without reply and only outgoing connections are possible.
  • block: Similar to the above, but instead of simply dropping connections, incoming requests are rejected with an icmp-host-prohibited or icmp6-adm-prohibitedmessage.
  • public: Represents public, untrusted networks. You don't trust other computers but may allow selected incoming connections on a case-by-case basis.
  • external: External networks in the event that you are using the firewall as your gateway. It is configured for NAT masquerading so that your internal network remains private but reachable.
  • internal: The other side of the external zone, used for the internal portion of a gateway. The computers are fairly trustworthy and some additional services are available.
  • dmz: Used for computers located in a DMZ (isolated computers that will not have access to the rest of your network). Only certain incoming connections are allowed.
  • work: Used for work machines. Trust most of the computers in the network. A few more services might be allowed.
  • home: A home environment. It generally implies that you trust most of the other computers and that a few more services will be accepted.
  • trusted: Trust all of the machines in the network. The most open of the available options and should be used sparingly.

Verify what zone is used by default

firewall-cmd --get-default-zone

Verify what zones are active

firewall-cmd --get-active-zones

View all info for default zone

firewall-cmd --list-all

List pre-defined zones and custom zone names

firewall-cmd --get-zones

View all information for a specific zone

firewall-cmd --permanent --zone=home --list-all

Change default zone

firewall-cmd --set-default-zone=home

Adding a service to a zone

First it is recommended to not add --permanent and to test of the service is reachable, if it works add the --permanent

firewall-cmd --zone=public --permanent --add-service=http

Removing/Denying a service

firewall-cmd --zone=public --permanent --remove-service=http

List services

firewall-cmd --zone=public --permanent --list-services

Removing/Denying  a port

firewall-cmd --zone=public --permanent --remove-port=12345/tcp 

To add a custom port

firewall-cmd --zone=public --permanent --add-port=8096/tcp

Add a port range

firewall-cmd --zone=public --permanent --add-port=4990-4999/udp

Check if port is added

firewall-cmd --list-ports

Services are simply collections of ports with an associated name and description, the simplest way to add a port to a service would be to copy the xml file and change the definition/port number.

cp /usr/lib/firewalld/services/service.xml /etc/firewalld/services/example.xml

Then reload

firewall-cmd --reload && firewall-cmd --get-services

Creating Your Own Zones

firewall-cmd --permanent --new-zone=my_zone
firewall-cmd --reload
firewall-cmd --zone=my_zone --add-service=ssh
firewall-cmd --zone=my_zone --change-interface=eth0

Then add the zone to your /etc/sysconfig/network-scripts/ifcfg-eth0

ZONE=my_zone

systemctl restart network
systemctl restart firewalld

And check if it works

firewall-cmd --zone=my_zone --list-services

Port Forwarding

Forward traffic coming from 80 to 12345

firewall-cmd --zone="public" --add-forward-port=port=80:proto=tcp:toport=12345

To forward a port to a different server:

Forwards traffic from local port 80 to port 8080 on a remote server located at the IP address: 123.456.78.9.

firewall-cmd --zone=public --add-masquerade
firewall-cmd --zone="public" --add-forward-port=port=80:proto=tcp:toport=8080:toaddr=123.456.78.9

If you need to remove it

sudo firewall-cmd --zone=public --remove-masquerade

Rich Rules

Allow all IPv4 traffic from host 192.168.0.14.

firewall-cmd --zone=public --add-rich-rule 'rule family="ipv4" source address=192.168.0.14 accept'

Deny IPv4 traffic over TCP from host 192.168.1.10 to port 22.

firewall-cmd --zone=public --add-rich-rule 'rule family="ipv4" source address="192.168.1.10" port port=22 protocol=tcp reject' 

Allow IPv4 traffic over TCP from host 10.1.0.3 to port 80, and forward it locally to port 6532.

firewall-cmd --zone=public --add-rich-rule 'rule family=ipv4 source address=10.1.0.3 forward-port port=80 protocol=tcp to-port=6532'

Forward all IPv4 traffic on port 80 to port 8080 on host 172.31.4.2 (masquerade should be active on the zone).

firewall-cmd --zone=public --add-rich-rule 'rule family=ipv4 forward-port port=80 protocol=tcp to-port=8080 to-addr=172.31.4.2'

To list your current Rich Rules:

firewall-cmd --list-rich-rules