FirewallD is a firewall management tool available by default on CentOS 7 servers. Basically, it is a wrapper around iptables and it comes with graphical configuration tool firewall-config and command line tool firewall-cmd. With the iptables service, every change requires flushing of the old rules and reading the new rules from the `/etc/sysconfig/iptables` file, while with firewalld only differences are applied.
FirewallD zones
FirewallD uses services and zones instead of iptables rules and chains. By default the following zones are available:
- drop – Drop all incoming network packets with no reply, only outgoing network connections are available.
- block – Reject all incoming network packets with an icmp-host-prohibited message, only outgoing network connections are available.
- public – Only selected incoming connections are accepted, for use in public areas
- external For external networks with masquerading enabled, only selected incoming connections are accepted.
- dmz – DMZ demilitarized zone, publicly-accessible with limited access to the internal network, only selected incoming connections are accepted.
- work – For computers in your home area, only selected incoming connections are accepted.
- home – For computers in your home area, only selected incoming connections are accepted.
- internal -For computers in your internal network, only selected incoming connections are accepted.
- trusted – All network connections are accepted.
To list all available zones run:
# firewall-cmd --get-zones work drop internal external trusted home dmz public block
To list the default zone:
# firewall-cmd --get-default-zone public
To change the default zone:
# firewall-cmd --set-default-zone=dmz # firewall-cmd --get-default-zone dmz
FirewallD services
FirewallD services are xml configuration files, with information of a service entry for firewalld. TO list all available services run:
# firewall-cmd --get-services amanda-client amanda-k5-client bacula bacula-client ceph ceph-mon dhcp dhcpv6 dhcpv6-client dns docker-registry dropbox-lansync freeipa-ldap freeipa-ldaps freeipa-replication ftp high-availability http https imap imaps ipp ipp-client ipsec iscsi-target kadmin kerberos kpasswd ldap ldaps libvirt libvirt-tls mdns mosh mountd ms-wbt mysql nfs ntp openvpn pmcd pmproxy pmwebapi pmwebapis pop3 pop3s postgresql privoxy proxy-dhcp ptp pulseaudio puppetmaster radius rpc-bind rsyncd samba samba-client sane smtp smtps snmp snmptrap squid ssh synergy syslog syslog-tls telnet tftp tftp-client tinc tor-socks transmission-client vdsm vnc-server wbem-https xmpp-bosh xmpp-client xmpp-local xmpp-server
xml configuration files are stored in the /usr/lib/firewalld/services/ and /etc/firewalld/services/ directories.
Configuring your firewall with FirewallD
As an example, here is how you can configure your RoseHosting VPS firewall with FirewallD if you were running a web server, SSH on port 7022 and mail server.
First we will set the default zone to dmz.
# firewall-cmd --set-default-zone=dmz # firewall-cmd --get-default-zone dmz
To add permanent service rules for HTTP and HTTPS to the dmz zone, run:
# firewall-cmd --zone=dmz --add-service=http --permanent # firewall-cmd --zone=dmz --add-service=https --permanent
Open port 25 (SMTP) and port 465 (SMTPS) :
firewall-cmd --zone=dmz --add-service=smtp --permanent firewall-cmd --zone=dmz --add-service=smtps --permanent
Open, IMAP, IMAPS, POP3 and POP3S ports:
firewall-cmd --zone=dmz --add-service=imap --permanent firewall-cmd --zone=dmz --add-service=imaps --permanent firewall-cmd --zone=dmz --add-service=pop3 --permanent firewall-cmd --zone=dmz --add-service=pop3s --permanent
Since the SSH port is changed to 7022, we will remove the ssh service (port 22) and open port 7022
firewall-cmd --remove-service=ssh --permanent firewall-cmd --add-port=7022/tcp --permanent
To implement the changes we need to reload the firewall with:
firewall-cmd --reload
Finally, you can list the rules with:
# firewall-cmd –list-all
dmz
target: default
icmp-block-inversion: no
interfaces:
sources:
services: http https imap imaps pop3 pop3s smtp smtps
ports: 7022/tcp
protocols:
masquerade: no
forward-ports:
sourceports:
icmp-blocks:
rich rules:
