RHEL7: How to get started with Firewalld. |
Note: This is an RHCSA 7 exam objective and an RHCE 7 exam objective. PresentationFirewalld is the new userland interface in RHEL 7. It replaces the iptables interface and connects to the netfilter kernel code. It mainly improves the security rules management by allowing configuration changes without stopping the current connections. To know if Firewalld is running, type: # systemctl status firewalld firewalld.service - firewalld - dynamic firewall daemon Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled) Active: active (running) since Tue 2014-06-17 11:14:49 CEST; 5 days ago ... or alternatively: # firewall-cmd --state running Note: If Firewalld is not running, the command displays not running. If you’ve got several network interfaces in IPv4, you will have to activate ip forwarding. net.ipv4.ip_forward=1 Then, activate the configuration: # sysctl -p Note: If you interested in kernel parameter configuration, there is a tutorial about the sysctl command. Although Firewalld is the RHEL 7 way to deal with firewalls and provides many improvements, iptables can still be used (but both shouldn’t run at the same time). You can also look at the iptables rules created by Firewalld with the iptables-save command. Zone ManagementAlso, a new concept of zone appears: all network interfaces can be located in the same default zone or divided into different ones according to the levels of trust defined. In the latter case, this allows to restrict traffic based on origin zone (read this article from lwn.net for more details). To get the default zone, type: # firewall-cmd --get-default-zone public To get the list of zones where you’ve got network interfaces or sources assigned to, type: # firewall-cmd --get-active-zones public interfaces: eth0 Note: You can have more than one active zone at a time. To get the list of all the available zones, type: # firewall-cmd --get-zones block dmz drop external home internal public trusted work To change the default zone to home permanently, type: # firewall-cmd --set-default-zone=home success Note: This information is stored in the /etc/firewalld/firewalld.conf file. Network interfaces can be assigned to a zone in a permanent way. # firewall-cmd --permanent --zone=internal --change-interface=eth0 success # nmcli con show | grep eth0 System eth0 4de55c95-2368-429b-be65-8f7b1a357e3f 802-3-ethernet eth0 # nmcli con mod "System eth0" connection.zone internal # nmcli con up "System eth0" Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/1) Note1: This operation can also be done by editing the /etc/sysconfig/network-scripts/ifcfg-eth0 file and add ZONE=internal followed by # nmcli con reload . It seems that with RHEL 7.5, the use of ZONE in ifcfg-* files no longer works (source). To know which zone is associated with the eth0 interface, type: # firewall-cmd --get-zone-of-interface=eth0 internal To get the permanent configuration of the public zone, type: # firewall-cmd --permanent --zone=public --list-all public (default, active) interfaces: eth0 sources: services: dhcpv6-client ssh ports: masquerade: no forward-ports: icmp-blocks: rich rules: It is also possible to create new zones. To create a new zone (here test), type: # firewall-cmd --permanent --new-zone=test success # firewall-cmd --reload success Note: Only permanent zones can be created. Source ManagementA zone can be bound to a network interface (see above) and/or to a network addressing (called here a source). This way, multiple zones can be defined even on a server with only one network interface! Caution: To get this feature, Firewalld relies on NetworkManager (see reference). This means that if you plan to stop NetworkManager for any reason (for example when building a KVM host), you will have to stop Firewalld and use Iptables instead! To add a source (here 192.168.2.0/24) to a zone (here trusted) permanently, type: # firewall-cmd --permanent --zone=trusted --add-source=192.168.2.0/24 success # firewall-cmd --reload success Note1: Use the –remove-source option to delete a previous assigned source. With the RHEL 7.3 release, you can add a source based on a MAC address (here 00:11:22:33:44:55) to a zone (here trusted) permanently: # firewall-cmd --permanent --zone=trusted --add-source=00:11:22:33:44:55 success # firewall-cmd --reload success With the RHEL 7.3 release, you can create an ipset (a set of IP addresses or networks, see below) and add a source based on it: # firewall-cmd --permanent --new-ipset=iplist --type=hash:ip success # firewall-cmd --reload success # firewall-cmd --ipset=iplist --add-entry=192.168.1.11 success # firewall-cmd --ipset=iplist --add-entry=192.168.1.12 success # firewall-cmd --permanent--zone=trusted --add-source=ipset:iplist success # firewall-cmd --reload success To get the list of the sources currently bound to a zone (here trusted), type: # firewall-cmd --permanent --zone=trusted --list-sources 192.168.2.0/24 00:11:22:33:44:55 ipset:iplist Note: Remove the –permanent option if you only want to display temporary settings. To keep track of your configuration (active zones are zones that have a binding to an interface or source), type: # firewall-cmd --get-active-zones public interfaces: eth0 trusted sources: 192.168.2.0/24 As an exemple of source management, let’s assume you want to only allow connections to your server from a specific IP address (here 1.2.3.4/32). # firewall-cmd --zone=internal --add-service=ssh --permanent success # firewall-cmd --zone=internal --add-source=1.2.3.4/32 --permanent success # firewall-cmd --zone=public --remove-service=ssh --permanent success # firewall-cmd --reload success Source: Serverfault website. With RHEL 7.3, a new option called –info-zone is available. # firewall-cmd --info-zone=public public (active) target: default icmp-block-inversion: no interfaces: eth0 sources: services: dhcpv6-client ssh ports: protocols: masquerade: no forward-ports: sourceports: icmp-blocks: rich rules: Note: You can also add the –permanent option. Service ManagementAfter assigning each network interface to a zone, it is now possible to add services to each zone. # firewall-cmd --permanent --zone=internal --add-service=http success # firewall-cmd --reload success Note1: Type –remove-service=http to deny the http service. If you want to temporary add several services (here http, https, and dns) at the same time in the internal zone, type: # firewall-cmd --zone=internal --add-service={http,https,dns} success To get the list of services in the default zone, type: # firewall-cmd --list-services dhcpv6-client ssh Note: To get the list of the services in a particular zone, add the –zone= option. With RHEL 7.3, a new option called –info-service is available. # firewall-cmd --info-service=ftp ftp ports: 21/tcp protocols: source-ports: modules: nf_conntrack_ftp destination: Note: You can also add the –permanent option. Firewall Services ConfigurationWith the Firewalld package, the firewall configuration of the main services (ftp, httpd, etc) comes in the /usr/lib/firewalld/services directory. But it is still possible to add new ones in the /etc/firewalld/services directory. Also, if files exist at both locations for the same service, the file in the /etc/firewalld/services directory takes precedence. For example, it is the case of the HAProxy service. There is no firewall configuration associated. <?xml version="1.0" encoding="utf-8"?> <service> <short>HAProxy</short> <description>HAProxy load-balancer</description> <port protocol="tcp" port="80"/> </service> Note: You can use the firewall-cmd –permanent –new-service=haproxy command to quickly create a configuration file skeleton. Assign the correct SELinux context and file permissions to the haproxy.xml file: # cd /etc/firewalld/services # restorecon haproxy.xml # chmod 640 haproxy.xml Add the HAProxy service to the default zone permanently and reload the firewall configuration: # firewall-cmd --permanent --add-service=haproxy success # firewall-cmd --reload success Note: According to Bert Van Vreckem, it is possible to go quicker by using the command history (see details here): # firewall-cmd --add-service=haproxy success # firewall-cmd --add-service=haproxy --permanent success In RHEL 7.0 (Firewalld v0.3.9.7), there were 47 firewall services configured: amanda-client, bacula, bacula-client, dhcp, dhcpv6, dhcpv6-client, dns, ftp, high-availability, http, https, imaps, ipp, ipp-client, ipsec, kerberos, kpasswd, ldap, ldaps, libvirt, libvirt-tls, mdns, mountd, ms-wbt, mysql, nfs, ntp, openvpn, pmcd, pmproxy, pmwebapi, pmwebapis, pop3s, postgresql, proxy-dhcp, radius, rpc-bind, samba, samba-client, smtp, ssh, telnet, tftp, tftp-client, transmission-client, vnc-server, wbem-https. Port ManagementPort management follows the same model as service management. To allow the 443/tcp port temporarily in the internal zone, type: # firewall-cmd --zone=internal --add-port=443/tcp success Note1: To make the configuration permanent, add the –permanent option and reload the firewall configuration. To get the list of ports currently open in the internal zone, type: # firewall-cmd --zone=internal --list-ports 443/tcp Note: To only get the list of ports permanently open, add the –permanent option. Here, you will not get anything. Rich RulesAs the syntax used by the rich rules are somehow difficult to remember, keep in mind the man firewalld.richlanguage command and the Example section at the end. Here is the format of a rich rule: # firewall-cmd --add-rich-rule 'rule ...' To allow all connections from 192.168.2.2, type: # firewall-cmd --add-rich-rule 'rule family="ipv4" source address="192.168.2.2" log accept' Note1: The log option writes coming packets into the /var/log/messages file. To list the rich rules set in the default zone, type: # firewall-cmd --list-all public (active) target: default icmp-block-inversion: no interfaces: eth0 sources: services: dhcpv6-client ssh ports: protocols: masquerade: no forward-ports: sourceports: icmp-blocks: rich rules: rule family="ipv4" source address="192.168.2.2" log accept Direct RulesIt is still possible to set specific rules by using the direct mode (here to open the tcp port 9000) that by-passes the Firewalld interface: # firewall-cmd --direct --add-rule ipv4 filter INPUT 0 -p tcp --dport 9000 -j ACCEPT success Note1: This example has been borrowed from Khosro Taraghi’s blog. To display all the direct rules added, type: # firewall-cmd --direct --get-all-rules Note1: For information, the configuration is written into the /etc/firewalld/direct.xml file. IP Set ManagementWith the RHEL 7.3 comes the ability to create ipsets. An ipset is a set of IP addresses or networks. The different categories belong to hash:ip or hash:net. To create a permanent IPv4 ipset containing two IP addresses and drop packets coming from these addresses, type: # firewall-cmd --permanent --new-ipset=blacklist --type=hash:ip success # firewall-cmd --reload success # firewall-cmd --ipset=blacklist --add-entry=192.168.1.11 success # firewall-cmd --ipset=blacklist --add-entry=192.168.1.12 success # firewall-cmd --add-rich-rule='rule source ipset=blacklist drop' success Note: Add –option=family=inet6 to create an IPv6 ipset. To get the content of the blacklist ipset, type: # firewall-cmd --info-ipset=blacklist blacklist type: hash:ip options: entries: 192.168.1.11 192.168.1.12 To remove the 192.168.1.12 entry from the blacklist ipset, type: # firewall-cmd --ipset=blacklist --remove-entry=192.168.1.12 success # firewall-cmd --ipset=blacklist --get-entries 192.168.1.11 To create a permanent IPv4 ipset containing two networks, type: # firewall-cmd --permanent --new-ipset=netlist success # firewall-cmd --reload success # firewall-cmd --ipset=netlist --add-entry=192.168.1.0/24 success # firewall-cmd --ipset=netlist --add-entry=192.168.2.0/24 success # firewall-cmd --info-ipset=netlist netlist type: hash:net options: entries: 192.168.1.0/24 192.168.2.0/24 To remove the netlist ipset, type: # firewall-cmd --permanent --delete-ipset=netlist success # firewall-cmd --reload success # firewall-cmd --get-ipsets blacklist It is also possible to download the content of an ipset from a file (--add-entries-from-file=file option) or store it with the name ipset in the /etc/firewalld/ipsets/ipset.xml or /usr/lib/firewalld/ipsets/ipset.xml files according to the following format: <?xml version="1.0" encoding="utf-8"?> <ipset type="hash:ip"> <short>My Ipset</short> <description>description</description> <entry>192.168.1.11</entry> <entry>192.168.1.12</entry> </ipset> To load this ipset, type: # firewall-cmd --reload MasqueradingIf your firewall is your network gateway and you don’t want everybody to know your internal addresses, you can set up two zones, one called internal, the other external, and configure masquerading on the external zone. This way, all packets will get your firewall ip address as source address. To set up masquerading on the external zone in a temporary way, type: # firewall-cmd --zone=external --add-masquerade success Note1: To remove masquerading, use the –remove-masquerade option. Port ForwardingPort forwarding is a way to forward inbound network traffic for a specific port to another internal address or an alternative port. Caution: Port forwarding requires masquerading (source). This point is a classical mistake made during the RHCE exam. So, you need to enable masquerading before anything else: # firewall-cmd --zone=external --add-masquerade success If you want all packets intended for port 22 to be now forwarded to port tcp 3753 temporarily, type: # firewall-cmd --zone=external --add-forward-port=port=22:proto=tcp:toport=3753 success Note1: To remove port forwarding, use the –remove-forward-port option. Also, if you want to define the destination ip address, this time in a permanent way, type: # firewall-cmd --permanent --zone=external --add-forward-port=port=22:proto=tcp:toport=3753:toaddr=10.0.0.1 success # firewall-cmd --reload success Special ModulesSometimes it is required to download specific modules. Instead of using a rc.local file, it is better to notify Firewalld through the /etc/modules-load.d directory. # echo ip_nat_ftp > /etc/modules-load.d/firewall_ftp.conf # echo ip_conntrack_ftp >> /etc/modules-load.d/firewall_ftp.conf Source: StackExchange website. Offline ConfigurationIn some cases (installations through Anaconda or Kickstart for example), you need to set up firewall rules when Firewalld is not running. The firewall-offline-cmd command has just been created for this purpose. -A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT Instead, you can now execute the following command: # firewall-offline-cmd --direct --add-rule ipv4 filter INPUT 0 -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT Configuration BackupTo store the current configuration into files, type: # iptables -S > firewalld_rules_ipv4 # ip6tables -S > firewalld_rules_ipv6 Debugging TipsTo better understand how Firewalld works, assign the ‘–debug’ value to the FIREWALLD_ARGS variable in the /etc/sysconfig/firewalld file: # firewalld command line args # possile values: --debug FIREWALLD_ARGS='--debug' Restart the Firewalld daemon: # systemctl restart firewalld Note: Messages will be written into the /var/log/firewalld file. Also, with the RHEL 7.3 release comes the LogDenied directive in the /etc/firewalld/firewalld.conf file. Reload the Firewalld configuration: # firewall-cmd --reload Note: Messages will be written into the /var/log/messages file. If you also want messages to be written in a file called /var/log/custom.log, edit the /etc/rsyslog.conf file, add the line kern.warning /var/log/custom.log and restart the rsyslog configuration with # systemctl restart rsyslog Additional ResourcesIn addition, you can:
Sources: RHEL7 Security Guide, wiki Fedora project.
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Posted - Wed, May 22, 2019 10:30 AM. This article has been viewed 11576 times. |
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