Using Firewalls
4.5.1. Introduction to firewalld
The dynamic firewall daemon
firewalld provides a dynamically managed firewall with support for network “zones” to assign a level of trust to a network and its associated connections and interfaces. It has support for IPv4 and IPv6 firewall settings. It supports Ethernet bridges and has a separation of runtime and permanent configuration options. It also has an interface for services or applications to add firewall rules directly. 4.5.2. Understanding firewalld
A graphical configuration tool, firewall-config, is used to configure
firewalld, which in turn uses iptables tool to communicate with Netfilter in the kernel which implements packet filtering.
To use the graphical firewall-config tool, press the Super key to enter the Activities Overview, type
firewall and then press Enter. The firewall-config tool appears. You will be prompted for an administrator password.
The firewall-config tool has a drop-down selection menu labeled Configuration. This enables selecting between and mode. Notice that if you select , an additional row of icons will appear in the left hand corner. These icons only appear in permanent configuration mode because a service's parameters cannot be changed in run time mode.
The firewall service provided by
firewalld is dynamic rather than static because changes to the configuration can be made at anytime and are immediately implemented, there is no need to save or apply the changes. No unintended disruption of existing network connections occurs as no part of the firewall has to be reloaded.
A command line client, firewall-cmd, is provided. It can be used to make permanent and non-permanent run-time changes as explained in
man firewall-cmd(1). Permanent changes need to be made as explained in the firewalld(1) man page. Note that the firewall-cmd command can be run by the root user and also by an administrative user, in other words, a member of the wheel group. In the latter case the command will be authorized via the polkit mechanism.
The configuration for
firewalld is stored in various XML files in /usr/lib/firewalld/ and /etc/firewalld/. This allows a great deal of flexibility as the files can be edited, written to, backed up, used as templates for other installations and so on.
Other applications can communicate with
firewalld using D-bus. 4.5.3. Comparison of firewalld to system-config-firewall and iptables
The essential differences between
Both use iptables tool to talk to the kernel packet filter.
firewalld and the iptables service are: - The iptables service stores configuration in
/etc/sysconfig/iptableswhilefirewalldstores it in various XML files in/usr/lib/firewalld/and/etc/firewalld/. Note that the/etc/sysconfig/iptablesfile does not exist asfirewalldis installed by default on Red Hat Enterprise Linux. - With the iptables service, every single change means flushing all the old rules and reading all the new rules from
/etc/sysconfig/iptableswhile withfirewalldthere is no re-creating of all the rules; only the differences are applied. Consequently,firewalldcan change the settings during run time without existing connections being lost.
4.5.4. Understanding Network Zones
Firewalls can be used to separate networks into different zones based on the level of trust the user has decided to place on the devices and traffic within that network. NetworkManager informs
firewalld to which zone an interface belongs. An interface's assigned zone can be changed by NetworkManager or via the firewall-config tool which can open the relevant NetworkManager window for you.
The zone settings in
/etc/firewalld/ are a range of preset settings which can be quickly applied to a network interface. They are listed here with a brief explanation: drop- Any incoming network packets are dropped, there is no reply. Only outgoing network connections are possible.
block- Any incoming network connections are rejected with an icmp-host-prohibited message for
IPv4and icmp6-adm-prohibited forIPv6. Only network connections initiated from within the system are possible. public- For use in public areas. You do not trust the other computers on the network to not harm your computer. Only selected incoming connections are accepted.
external- For use on external networks with masquerading enabled especially for routers. You do not trust the other computers on the network to not harm your computer. Only selected incoming connections are accepted.
dmz- For computers in your demilitarized zone that are publicly-accessible with limited access to your internal network. Only selected incoming connections are accepted.
work- For use in work areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.
home- For use in home areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.
internal- For use on internal networks. You mostly trust the other computers on the networks to not harm your computer. Only selected incoming connections are accepted.
trusted- All network connections are accepted.
It is possible to designate one of these zones to be the default zone. When interface connections are added to NetworkManager, they are assigned to the default zone. On installation, the default zone in
firewalld is set to be the public zone. 4.5.5. Choosing a Network Zone
The network zone names have been chosen to be self-explanatory and to allow users to quickly make a reasonable decision. However, a review of the default configuration settings should be made and unnecessary services disabled according to your needs and risk assessments.
4.5.6. Understanding Predefined Services
A service can be a list of local ports and destinations as well as a list of firewall helper modules automatically loaded if a service is enabled. The use of predefined services makes it easier for the user to enable and disable access to a service. Using the predefined services, or custom defined services, as opposed to opening ports or ranges or ports may make administration easier. Service configuration options and generic file information are described in the
firewalld.service(5) man page. The services are specified by means of individual XML configuration files which are named in the following format: service-name.xml.
To view the list of services using the graphical firewall-config tool, press the Super key to enter the Activities Overview, type
firewall and then press Enter. The firewall-config tool appears. You will be prompted for an administrator password. You can now view the list of services under the Services tab.
To list the default predefined services available using the command line, issue the following command as
root: ~]# ls /usr/lib/firewalld/services/
Files in /usr/lib/firewalld/services/ must not be edited. Only the files in /etc/firewalld/services/ should be edited.
To list the system or user created services, issue the following command as
root: ~]# ls /etc/firewalld/services/
Services can be added and removed using the graphical firewall-config tool and by editing the XML files in
/etc/firewalld/services/. If a service has not been added or changed by the user, then no corresponding XML file will be found in /etc/firewalld/services/. The files /usr/lib/firewalld/services/ can be used as templates if you wish to add or change a service. As root, issue a command in the following format: ~]# cp /usr/lib/firewalld/services/[service].xml /etc/firewalld/services/[service].xml
You may then edit the newly created file. firewalld will prefer files in /etc/firewalld/services/ but will fall back to /usr/lib/firewalld/services/ should a file be deleted, but only after a reload. 4.5.7. Understanding the Direct Interface
firewalld has a so called “direct interface”, which enables directly passing rules to iptables, ip6tables and ebtables. It is intended for use by applications and not users. It is dangerous to use the direct interface if you are not very familiar with iptables as you could inadvertently cause a breach in the firewall. firewalld still tracks what has been added, so it is still possible to query firewalld and see the changes made by an application using the direct interface mode. The direct interface is used by adding the --direct option to the firewall-cmd command.
The direct interface mode is intended for services or applications to add specific firewall rules during run time. The rules are not permanent and need to be applied every time after receiving the start, restart or reload message from
firewalld using D-BUS. 4.5.8. Checking if firewalld is Installed
In Red Hat Enterprise Linux 7
firewalld and the graphical user interface configuration tool firewall-config are installed by default. This can be checked by running the following command as root: ~]# yum install firewalld firewall-config
4.5.9. Disabling firewalld
To disable
firewalld, run the following commands as root: ~]#systemctl disable firewalld#systemctl stop firewalld
4.5.10. Using the iptables Service
To use the
iptables and ip6tables services instead of firewalld, first disable firewalld by running the following command as root: ~]#systemctl disable firewalld#systemctl stop firewalld
Then install the iptables-services package by entering the following command as
root: ~]# yum install iptables-services
The iptables-services package contains the iptables service and the ip6tables service.
Then, to start the
iptables and ip6tables services, run the following commands as root: # systemctl start iptables# systemctl start ip6tables# systemctl enable iptables# systemctl enable ip6tables
4.5.11. Start firewalld
To start
firewalld, enter the following command as root: ~]# systemctl start firewalld
4.5.12. Checking if firewalld is Running
To check if
firewalld is running, enter the following command: ~]$ systemctl status firewalld
firewalld.service - firewalld - dynamic firewall daemon
Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
Active: active (running) since Sat 2013-04-06 22:56:59 CEST; 2 days ago
Main PID: 688 (firewalld)
CGroup: name=systemd:/system/firewalld.service
In addition, check if firewall-cmd can connect to the daemon by entering the following command:
~]$ firewall-cmd --state
running
4.5.13. Installing firewalld
To install firewalld, run the following command as
root: ~]# yum install firewalld
To install the graphical user interface tool firewall-config, run the following command as root: ~]# yum install firewall-config
4.5.14. Configuring the Firewall
The firewall can be configured using the graphical user interface tool firewall-config, using the command line interface tool firewall-cmd and by editing XML configuration files. These methods will be described in order.
4.5.14.1. Configuring The Firewall Using The Graphical User Interface
4.5.14.1.1. Start The graphical firewall configuration tool
To start the graphical firewall-config tool, press the Super key to enter the Activities Overview, type
firewall and then press Enter. The firewall-config tool appears. You will be prompted for an administrator password.
To start the graphical firewall configuration tool using the command line, enter the following command as
root user: ~]# firewall-config
The Firewall Configuration window opens. Note, this command can be run as normal user but you will then be prompted for an administrator password from time to time. 
Look for the word “Connected” in the lower left corner. This indicates that the firewall-config tool is connected to the user space daemon,
firewalld. Note that the ICMP Types, Direct Configuration, and Lockdown Whitlist tabs are only visible after being selected from the View drop-down menu. 4.5.14.1.2. Changing the Firewall Settings
To immediately change the current firewall settings, ensure the current view is set to Runtime. Alternatively, to edit the settings to be applied at the next system start, or firewall reload, select Permanent from the drop-down list.
Note
When making changes to the firewall settings in Runtime mode, your selection takes immediate effect when you set or clear the check box associated with the service. You should keep this in mind when working on a system that may be in use by other users.
When making changes to the firewall settings in Permanent mode, your selection will only take effect when you reload the firewall or the system restarts. You can use the reload icon below the File menu, or click the Options menu and select Reload Firewall.
You can select zones in the left hand side column. You will notice the zones have some services enabled, you may need to resize the window or scroll to see the full list. You can customize the settings by selecting and deselecting a service.
4.5.14.1.3. Add an Interface to a Zone
To add or reassign an interface of a connection to a zone, start firewall-config, select Options from the menu bar, select Change Zones of Connections from the drop-down menu, the Connections list is displayed. Select the connection to be reassigned. The Select Zone for Connection window appears. Select the new firewall zone from the drop-down menu and click OK.
4.5.14.1.4. Set the Default Zone
To set the default zone that new interfaces will be assigned to, start firewall-config, select Options from the menu bar, select Change Default Zone from the drop-down menu. The Default Zone window appears. Select the zone form the list that you want to be used as the default zone and click OK.
4.5.14.1.5. Configuring Services
To enable or disable a predefined or custom service, start the firewall-config tool and select the network zone whose services are to be configured. Select the Services tab and select the check box for each type of service you want to trust. Clear the check box to block a service.
To edit a service, start the firewall-config tool and then select mode from the drop-down selection menu labeled Configuration. Additional icons and menu buttons appear at the bottom of the window. Select the service you wish to configure.
The Ports and Protocols tab enables adding, changing, and removing of ports and protocols for the selected service. The modules tab is for configuring Netfilter helper modules. The Destination tab enables limiting traffic to a particular destination address and Internet Protocol (
IPv4 or IPv6). 4.5.14.1.6. Open Ports in the Firewall
To permit traffic through the firewall to a certain port, start the firewall-config tool and select the network zone whose settings you want to change. Select the Ports tab and the click the button on the right hand side. The Port and Protocol window opens.
Enter the port number or range of ports to permit. Select tcp or udp from the drop-down list.
4.5.14.1.7. Enable IP Address Masquerading
To translate
IPv4 addresses to a single external address, start the firewall-config tool and select the network zone whose addresses are to be translated. Select the Masquerading tab and select the check box to enable the translation of IPv4 addresses to a single address. 4.5.14.1.8. Configure Port Forwarding
To forward inbound network traffic, or “packets”, for a specific port to an internal address or alternative port, first enable IP address masquerading, then select the Port Forwarding tab.
Select the protocol of the incoming traffic and the port or range of ports on the upper section of the window. The lower section is for setting details about the destination.
To forward traffic to a local port, that is to say to a port on the same system, select the Local forwarding check box. Enter the local port or range of ports for the traffic to be sent to.
To forward traffic to another
IPv4 address, select the Forward to another port check box. Enter the destination IP address and port or port range. The default is to send to the same port if the port field is left empty. Click OK to apply the changes. 4.5.14.1.9. Configuring the ICMP Filter
To enable or disable an
ICMP filter, start the firewall-config tool and select the network zone whose messages are to be filtered. Select the ICMP Filter tab and select the check box for each type of ICMP message you want to filter. Clear the check box to disable a filter. This setting is per direction and the default allows everything.
To edit an
ICMP type, start the firewall-config tool and then select mode from the drop-down selection menu labeled Configuration. Additional icons appear at the bottom of the window. 4.5.14.2. Configuring the Firewall Using the Command Line Tool, firewall-cmd
The command line tool firewall-cmd is part of the
firewalld application which is installed by default. You can verify that it is installed by checking the version or displaying the help output. Enter the following command to check the version: ~]$ firewall-cmd --version
Enter the following command to view the help output: ~]$ firewall-cmd --help
We list a selection of commands below, for a full list please see the man page,
man firewall-cmd(1).
Note
In order to make a command permanent or persistent, add the
--permanent option to all commands apart from the --direct commands (which are by their nature temporary). Note that this not only means the change will be permanent but that the change will only take effect after firewall reload, service restart, or after system reboot. Settings made with firewall-cmd without the --permanent option take effect immediately, but are only valid till next firewall reload, system boot, or firewalld service restart. Reloading the firewall does not in itself break connections, but be aware you are discarding temporary changes by doing so. 4.5.14.3. View the Firewall Settings Using the Command Line Interface (CLI)
To get a text display of the state of
firewalld, enter the following command: ~]$ firewall-cmd --state
To view the list of active zones, with a list of the interfaces currently assigned to them, enter the following command:
~]$ firewall-cmd --get-active-zones
public: em1 wlan0
To find out the zone that an interface, for example em1, is currently assigned to, enter the following command:
~]$ firewall-cmd --get-zone-of-interface=em1
public
To find out all the interfaces assigned to a zone, for example the public zone, enter the following command as
root: ~]# firewall-cmd --zone=public --list-interfaces
em1 wlan0
This information is obtained from NetworkManager and only shows interfaces not connections.
To find out all the settings of a zone, for example the public zone, enter the following command as
root: ~]# firewall-cmd --zone=public --list-all
public
interfaces:
services: mdns dhcpv6-client ssh
ports:
forward-ports:
icmp-blocks: source-quench
To view the network zones currently active, enter the following command as
root: ~]# firewall-cmd --get-service
cluster-suite pop3s bacula-client smtp ipp radius bacula ftp mdns samba dhcpv6-client dns openvpn imaps samba-client http https ntp vnc-server telnet libvirt ssh ipsec ipp-client amanda-client tftp-client nfs tftp libvirt-tls
This will list the names of the services in /usr/lib/firewalld/services/. Note that the configuration files themselves are named service-name.xml.
To view the network zones that will be active after the next firewall reload, enter the following command as
root: ~]# firewall-cmd --get-service --permanent
4.5.14.4. Change the Firewall Settings Using the Command Line Interface (CLI)
4.5.14.4.1. Drop All Packets (Panic Mode)
To start dropping all incoming and outgoing packets, enter the following command as
root: ~]# firewall-cmd --panic-on
All incoming and outgoing packets will be dropped. Active connections will be terminated after a period of inactivity; the time taken depends on the individual session time out values.
To start passing incoming and outgoing packets again, enter the following command as
root: ~]# firewall-cmd --panic-off
After disabling panic mode, established connections might work again if panic mode was enabled for a short period of time.
To find out if panic mode is enabled or disabled, enter the following command:
~]$ firewall-cmd --query-panic
Prints yes with exit status 0, if enabled, prints no with exit status 1 otherwise. 4.5.14.4.2. Reload the Firewall Using the Command Line Interface (CLI)
To reload the firewall with out interrupting user connections, that is to say, with out losing state information, enter the following command as
root: ~]# firewall-cmd --reload
To reload the firewall and interrupt user connections, that is to say, to discard state information, enter the following command as
root: ~]# firewall-cmd --complete-reload
This command should normally only be used in case of severe firewall problems. For example, if there are state information problems and no connection can be established but the firewall rules are correct. 4.5.14.4.3. Add an Interface to a Zone Using the Command Line Interface (CLI)
To add an interface to a zone, for example to add em1 to the public zone, enter the following command as
root: ~]# firewall-cmd --zone=public --add-interface=em1
To make this setting permanent, add the --permanent option and reload the firewall. 4.5.14.4.4. Add an Interface to a Zone by Editing the Interface Configuration File
To add an interface to a zone by editing the
ifcfg-em1 configuration file, for example to add em1 to the work zone, as root use an editor to add the following line to ifcfg-em1: ZONE=workNote that if you omit the
ZONE option, or use ZONE=, or ZONE='', then the default zone will be used.
NetworkManager will automatically reconnect and the zone will be set accordingly.
4.5.14.4.5. Configure the Default Zone by Editing the firewalld Configuration File
As
root, open /etc/firewalld/firewalld.conf and edit the file as follows: # default zone # The default zone used if an empty zone string is used. # Default: public DefaultZone=home
Reload the firewall, by entering the following command as
root: ~]# firewall-cmd --reload
This will reload the firewall without losing state information (TCP sessions will not be interrupted). 4.5.14.4.6. Set the Default Zone by Using the Command Line Interface (CLI)
To set the default zone, for example to public, enter the following command as
root: ~]# firewall-cmd --set-default-zone=public
This change will take immediate effect and in this case it is not necessary to reload the firewall. 4.5.14.4.7. Open Ports in the Firewall Using the Command Line Interface (CLI)
List all open ports for a zone, for example dmz, by entering the following command as
root: ~]# firewall-cmd --zone=dmz --list-ports
To add a port to a zone, for example to allow
TCP traffic to port 8080 to the dmz zone, enter the following command as root: ~]# firewall-cmd --zone=dmz --add-port=8080/tcp
To make this setting permanent, add the --permanent option and reload the firewall.
To add a range of ports to a zone, for example to allow the ports from 5060 to 5061 to the public zone, enter the following command as
root: ~]# firewall-cmd --zone=public --add-port=5060-5061/udp
To make this setting permanent, add the --permanent option and reload the firewall. 4.5.14.4.8. Add a Service to a Zone Using the Command Line Interface (CLI)
To add a service to a zone, for example to allow
SMTP to the work zone, enter the following command as root: ~]# firewall-cmd --zone=work --add-service=smtp
To make this setting permanent, add the --permanent option and reload the firewall. 4.5.14.4.9. Remove a Service from a Zone Using the Command Line Interface (CLI)
To remove a service from a zone, for example to remove
SMTP from the work zone, enter the following command as root: ~]# firewall-cmd --zone=work --remove-service=smtp
Add the --permanent option to make the change persist after system boot. If using this option and you wish to make the change immediate, reload the firewall, by entering the following command as root: ~]# firewall-cmd --reload
Note, this will not break established connections. If that is your intention, you could use the --complete-reload option but this will break all established connections not just for the service you have removed. 4.5.14.4.10. Add a Service to a Zone by Editing XML Files
To view the default zone files, enter the following command as
root: ~]# ls /usr/lib/firewalld/zones/
block.xml drop.xml home.xml public.xml work.xml
dmz.xml external.xml internal.xml trusted.xml
These files must not be edited. They are used by default if no equivalent file exists in the /etc/firewalld/zones/ directory.
To view the zone files that have been changed from the default, enter the following command as
root: ~]# ls /etc/firewalld/zones/
external.xml public.xml public.xml.old
In the example shown above, the work zone file does not exist. To add the work zone file, enter the following command as
root: ~]# cp /usr/lib/firewalld/zones/work.xml /etc/firewalld/zones/
You can now edit the file in the /etc/firewalld/zones/ directory. If you delete the file, firewalld will fall back to using the default file in /usr/lib/firewalld/zones/.
To add a service to a zone, for example to allow
SMTP to the work zone, use an editor with root privileges to edit the /etc/firewalld/zones/work.xml file to include the following line: <service name="smtp"/>
4.5.14.4.11. Remove a Service from a Zone by Editing XML files
An editor running with
root privileges is required to edit the XML zone files. To view the files for previously configured zones, enter the following command as root: ~]# ls /etc/firewalld/zones/
external.xml public.xml work.xml
To remove a service from a zone, for example to remove
SMTP from the work zone, use an editor with root privileges to edit the /etc/firewalld/zones/work.xml file to remove the following line: <service name="smtp"/>If no other changes have been made to the
work.xml file, it can be removed and firewalld will use the default /usr/lib/firewalld/zones/work.xml configuration file after the next reload or system boot. 4.5.14.4.12. Configure IP Address Masquerading
To check if IP masquerading is enabled, for example for the external zone, enter the following command as
root: ~]# firewall-cmd --zone=external --query-masquerade
Prints yes with exit status 0, if enabled, prints no with exit status 1 otherwise. If zone is omitted, the default zone will be used.
To enable IP masquerading, enter the following command as
root: ~]# firewall-cmd --zone=external --add-masquerade
To make this setting permanent, add the --permanent option and reload the firewall.
To disable IP masquerading, enter the following command as
root: ~]# firewall-cmd --zone=external --remove-masquerade
To make this setting permanent, add the --permanent option and reload the firewall. 4.5.14.4.13. Configure Port Forwarding Using the Command Line Interface (CLI)
To forward inbound network packets from one port to an alternative port or address, first enable IP address masquerading for a zone, for example external, by entering the following command as
root: ~]# firewall-cmd --zone=external --add-masquerade
To forward packets to a local port, that is to say to a port on the same system, enter the following command as
root: ~]# firewall-cmd --zone=external --add-forward-port=port=22:proto=tcp:toport=3753
In this example, the packets intended for port 22 are now forwarded to port 3753. The original destination port is specified with the port option. This option can be a port, or port range, together with a protocol. The protocol, if specified, must be one of either tcp or udp. The new local port, the port or range of ports to which the traffic is being forwarded to, is specified with the toport option. To make this setting permanent, add the --permanent option and reload the firewall.
To forward packets to another
IPv4 address, usually an internal address, without changing the destination port, enter the following command as root: ~]# firewall-cmd --zone=external --add-forward-port=port=22:proto=tcp:toaddr=192.0.2.55
In this example, the packets intended for port 22 are now forwarded to the same port at the address given with the toaddr. The original destination port is specified with the port. This option can be a port, or port range, together with a protocol. The protocol, if specified, must be one of either tcp or udp. The new destination port, the port or range of ports to which the traffic is being forwarded to, is specified with the toport. To make this setting permanent, add the --permanent option and reload the firewall.
To forward packets to another port at another
IPv4 address, usually an internal address, enter the following command as root: ~]#In this example, the packets intended for port 22 are now forwarded to port 2055 at the address given with thefirewall-cmd --zone=external /--add-forward-port=port=22:proto=tcp:toport=2055:toaddr=192.0.2.55
toaddr option. The original destination port is specified with the port option. This option can be a port, or port range, together with a protocol. The protocol, if specified, must be one of either tcp or udp. The new destination port, the port or range of ports to which the traffic is being forwarded to, is specified with the toport. To make this setting permanent, add the --permanent option and reload the firewall. 4.5.14.5. Configuring the Firewall Using XML Files
The configuration settings for firewalld are stored in XML files in the
/etc/firewalld/ directory. Do not edit the files in the /usr/lib/firewalld/ directory, they are for the default settings. You will need root user permissions to view and edit the XML files. The XML files are explained in three man pages: firewalld.icmptype(5)man page — Describes XML configuration files forICMPfiltering.
firewalld.service(5)man page — Describes XML configuration files for firewalld service.
firewalld.zone(5)man page — Describes XML configuration files forfirewalldzone configuration.
The XML files can be created and edited directly or created indirectly using the graphical and command line tools. Organizations can distribute them in RPM files which can make management and version control easier. Tools such as Puppet can distribute such configuration files.
4.5.14.6. Using the Direct Interface
It is possible to add and remove chains during runtime by using the
--direct option with the firewall-cmd tool. A few examples are presented here, please see the firewall-cmd(1) man page for more information.
It is dangerous to use the direct interface if you are not very familiar with iptables as you could inadvertently cause a breach in the firewall.
The direct interface mode is intended for services or applications to add specific firewall rules during run time. The rules are not permanent and need to be applied every time after receiving the start, restart or reload message from
firewalld using D-BUS. 4.5.14.6.1. Adding a Custom Rule Using the Direct Interface
To add a custom rule to the chain “IN_public_allow”, issuing a command as
root in the following format: ~]#firewall-cmd --direct --add-rule ipv4 filter IN_public_allow \0 -m tcp -p tcp --dport 666 -j ACCEPT
4.5.14.6.2. Removing a Custom Rule Using the Direct Interface
To remove a custom rule from the chain “IN_public_allow”, issuing a command as
root in the following format: ~]#firewall-cmd --direct --remove-rule ipv4 filter IN_public_allow \0 -m tcp -p tcp --dport 666 -j ACCEPT
4.5.14.6.3. Listing Custom Rules Using the Direct Interface
To list the rules in the chain “IN_public_allow”, issuing a command as
root in the following format: ~]# firewall-cmd --direct --get-rules ipv4 filter IN_public_allow
4.5.15. Configuring Complex Firewall Rules with the "Rich Language" Syntax
With the “rich language” syntax, complex firewall rules can be created in a way that is easier to understand than the direct interface method. In addition, the settings can be made permanent. The language uses keywords with values and is an abstract representation of iptables rules. Zones can be configured using this language, the current configuration method will still be supported.
4.5.15.1. Format of the Rich Language Commands
All the commands in this section need to be run as
root. The format of the command to add a rule is as follows: firewall-cmd [--zone=zone] --add-rich-rule='rule' [--timeout=seconds]
To remove a rule:
firewall-cmd [--zone=zone] --remove-rich-rule='rule'
To check if a rule is present:
firewall-cmd [--zone=zone] --query-rich-rule='rule'yes with exit status 0, if enabled, prints no with exit status 1 otherwise. If the zone is omitted, the default zone will be used.
For information about the rich language representation used in the zone configuration files, see the
firewalld.zone(5) man page. 4.5.15.2. Understanding the Rich Rule Structure
The format or structure of the rich rule commands is as follows:
rule [family="<rule family>"]
[ source address="<address>" [invert="True"] ]
[ destination address="<address>" [invert="True"] ]
[ <element> ]
[ log [prefix="<prefix text>"] [level="<log level>"] [limit value="rate/duration"] ]
[ audit ]
[ accept|reject|drop ]
A rule is associated with a particular zone. A zone can have several rules. If some rules interact or contradict, the first rule that matches the packet applies. If the rule family is provided, it can be either
ipv4 or ipv6, it limits the rule to IPv4 or IPv6. If the rule family is not provided, the rule will be added for both IPv4 and IPv6. If source or destination addresses are used in a rule, then the rule family needs to be provided. This is also the case for port forwarding. 4.5.15.3. Understanding the Rich Rule Commands
source- By specifying the source address the origin of a connection attempt can be limited to the source address. A source address or address range is either an IP address or a network IP address with a mask for
IPv4orIPv6. The network family (IPv4orIPv6) will be automatically discovered. ForIPv4, the mask can be a network mask or a plain number. ForIPv6the mask is a plain number. The use of host names is not supported. It is possible to invert the sense of the source address command by addinginvert="true" orinvert="yes"; all but the supplied address will match. destination- By specifying the destination address the target can be limited to the destination address. The destination address uses the same syntax as the source address. The use of source and destination addresses is optional and the use of a destination addresses is not possible with all elements. This depends on the use of destination addresses, for example in service entries. The element can be exactly one of the element types:
service,port,protocol,masquerade,icmp-blockandforward-port. service- The service name is one of the firewalld provided services. To get a list of the supported services, issue the following command:
firewall-cmd --get-services. If a service provides a destination address, it will conflict with a destination address in the rule and will result in an error. The services using destination addresses internally are mostly services using multicast. The command takes the following form:
service name=service_name port- The port can either be a single port number or a port range, for example, 5060-5062. The protocol can either be specified as
tcporudp. The command takes the following form:
port port=number_or_range protocol=protocol protocol- The protocol value can be either a protocol ID number or a protocol name. For allowed protocol entries, see
/etc/protocols. The command takes the following form:
protocol value=protocol_name_or_ID icmp-block- Use this command to block one or more
ICMPtypes. TheICMPtype is one of theICMPtypes firewalld supports. To get a listing of supportedICMPtypes, issue the following command:
~]$
Specifying an action is not allowed here.firewall-cmd --get-icmptypesicmp-blockuses the actionrejectinternally. The command takes the following form:
icmp-block name=icmptype_name masquerade- Turns on IP masquerading in the rule. A source address can be provided to limit masquerading to this area, but not a destination address. Specifying an action is not allowed here.
forward-port- Forward packets from a local port with protocol specified as
tcporudpto either another port locally, to another machine, or to another port on another machine. Theportandto-portcan either be a single port number or a port range. The destination address is a simple IP address. Specifying an action is not allowed here. Theforward-portcommand uses the actionacceptinternally. The command takes the following form:
forward-port port=number_or_range protocol=protocol /to-port=number_or_range to-addr=address log- Log new connection attempts to the rule with kernel logging, for example in syslog. You can define a prefix text that will be added to the log message as a prefix. Log level can be one of
emerg,alert,crit,error,warning,notice,infoordebug. The use of log is optional. It is possible to limit logging as follows:
The rate is a natural positive number [1, ..], the duration oflog [prefix=prefix text] [level=log level] limit value=rate/durations,m,h,d.smeans seconds,mminutes,hhours andddays. The maximum limit value is1/dwhich means at maximum one log entry per day. audit- Audit provides an alternative way for logging using audit records sent to the service
auditd. The audit type can be one ofACCEPT,REJECTorDROPbut it is not specified after the commandauditas the audit type will be automatically gathered from the rule action. Audit does not have its own parameters, but limit can be added optionally. The use of audit is optional. accept|reject|drop- An action can be one of
accept,rejectordrop. The rule can only contain an element or a source. If the rule contains an element, then new connections matching the element will be handled with the action. If the rule contains a source, then everything from the source address will be handled with the action specified.
accept | reject [type=reject type] | drop
Withacceptall new connection attempts will be granted. Withrejectthey will be rejected and their source will get a reject message. The reject type can be set to use another value. Withdropall packets will be dropped immediately and no information is sent to the source.
4.5.15.4. Using the Rich Rule Log Command
Logging can be done with the Netfilter log target and also with the audit target. A new chain is added to all zones with a name in the format “zone_log”, where zone is the zone name. This is processed before the
deny chain in order to have proper ordering. The rules or parts of them are placed in separate chains, according to the action of the rule, as follows: zone_log zone_deny zone_allow
All logging rules will be placed in the “zone_log” chain, which will be parsed first. All
reject and drop rules will be placed in the “zone_deny” chain, which will be parsed after the log chain. All accept rules will be placed in the “zone_allow” chain, which will be parsed after the deny chain. If a rule contains log and also deny or allow actions, the parts are placed in the matching chains. 4.5.15.4.1. Using the Rich Rule Log Command Example 1
Enable new
IPv4 and IPv6 connections for authentication header protocol AH: rule protocol value="ah" accept
4.5.15.4.2. Using the Rich Rule Log Command Example 2
Allow new
IPv4 and IPv6 connections for protocol FTP and log 1 per minute using audit: rule service name="ftp" log limit value="1/m" audit accept
4.5.15.4.3. Using the Rich Rule Log Command Example 3
Allow new
IPv4 connections from address 192.168.0.0/24 for protocol TFTP and log 1 per minute using syslog: rule family="ipv4" source address="192.168.0.0/24" service name="tftp" log prefix="tftp" level="info" limit value="1/m" accept
4.5.15.4.4. Using the Rich Rule Log Command Example 4
New
IPv6 connections from 1:2:3:4:6:: for protocol RADIUS are all rejected and logged at a rate of 3 per minute. New IPv6 connections from other sources are accepted: rule family="ipv6" source address="1:2:3:4:6::" service name="radius" log prefix="dns" level="info" limit value="3/m" reject rule family="ipv6" service name="radius" accept
4.5.15.4.5. Using the Rich Rule Log Command Example 5
Forward
IPv6 packets received from 1:2:3:4:6:: on port 4011 with protocol TCP to 1::2:3:4:7 on port 4012. rule family="ipv6" source address="1:2:3:4:6::" forward-port to-addr="1::2:3:4:7" to-port="4012" protocol="tcp" port="4011"
4.5.15.4.6. Using the Rich Rule Log Command Example 6
Whitelist a source address to allow all connections from this source.
rule family="ipv4" source address="192.168.2.2" accept
See the
firewalld.richlanguage(5) man page for more examples. 4.5.16. Firewall Lockdown
Local applications or services are able to change the firewall configuration if they are running as
root (for example, libvirt). With this feature, the administrator can lock the firewall configuration so that either no applications, or only applications that are added to the lockdown whitelist, are able to request firewall changes. The lockdown settings default to disabled. If enabled, the user can be sure that there are no unwanted configuration changes made to the firewall by local applications or services. 4.5.16.1. Configuring Firewall Lockdown
Using an editor running as
root, add the following line to the /etc/firewalld/firewalld.conf file as follows: Lockdown=yesReload the firewall using the following command as
root: ~]# firewall-cmd --reload
Try to enable the service imaps in the default zone using the following command as an administrative user, that is to say, a user in group wheel (usually the first user on system). You will be prompted for the user password: ~]$ firewall-cmd --add-service=imaps
Error: ACCESS_DENIED: lockdown is enabled
To enable the use of firewall-cmd, issue the following command as
root: ~]# firewall-cmd --add-lockdown-whitelist-command='/usr/bin/python -Es /usr/bin/firewall-cmd*'
Add the --permanent option if you want to make it persistent.
Reload the firewall as
root: ~]# firewall-cmd --reload
Try to enable the imaps service again in the default zone by entering the following command as an administrative user. You will be prompted for the user password: ~]$ firewall-cmd --add-service=imaps
This time the command succeeds. 4.5.16.2. Configure Lockdown with the Command Line Client
To query whether lockdown is enabled, enter the following command as
root: ~]# firewall-cmd --query-lockdown
Prints yes with exit status 0, if lockdown is enabled, prints no with exit status 1 otherwise.
To enable lockdown, enter the following command as
root: ~]# firewall-cmd --lockdown-on
To disable lockdown, enter the following command as
root: ~]# firewall-cmd --lockdown-off
4.5.16.3. Configure Lockdown Whitelist Options with the Command Line
The lockdown whitelist can contain commands, security contexts, users and user IDs. If a command entry on the whitelist ends with an asterisk “*”, then all command lines starting with that command will match. If the “*” is not there then the absolute command including arguments must match.
The context is the security (SELinux) context of a running application or service. To get the context of a running application use the following command:
~]$ ps -e --context
That command returns all running applications. Pipe the output through the grep tool to get the application of interest. For example: ~]$ ps -e --context | grep example_program
To list all command lines that are on the whitelist, enter the following command as
root: ~]# firewall-cmd --list-lockdown-whitelist-commands
To add a command command to the whitelist, enter the following command as
root: ~]# firewall-cmd --add-lockdown-whitelist-command='/usr/bin/python -Es /usr/bin/command'
To remove a command command from the whitelist, enter the following command as
root: ~]# firewall-cmd --remove-lockdown-whitelist-command='/usr/bin/python -Es /usr/bin/command'
To query whether the command command is on the whitelist, enter the following command as
root: ~]# firewall-cmd --query-lockdown-whitelist-command='/usr/bin/python -Es /usr/bin/command'
Prints yes with exit status 0, if true, prints no with exit status 1 otherwise.
To list all security contexts that are on the whitelist, enter the following command as
root: ~]# firewall-cmd --list-lockdown-whitelist-contexts
To add a context context to the whitelist, enter the following command as
root: ~]# firewall-cmd --add-lockdown-whitelist-context=context
Add the --permanent option to make it persistent.
To remove a context context from the whitelist, enter the following command as
root: ~]# firewall-cmd --remove-lockdown-whitelist-context=context
Add the --permanent option to make it persistent.
To query whether the context context is on the whitelist, enter the following command
root: ~]# firewall-cmd --query-lockdown-whitelist-context=context
Prints yes with exit status 0, if true, prints no with exit status 1 otherwise.
To list all user IDs that are on the whitelist, enter the following command as
root: ~]# firewall-cmd --list-lockdown-whitelist-uids
To add a user ID uid to the whitelist, enter the following command as
root: ~]# firewall-cmd --add-lockdown-whitelist-uid=uid
Add the --permanent option to make it persistent.
To remove a user ID uid from the whitelist, enter the following command as
root: ~]# firewall-cmd --remove-lockdown-whitelist-uid=uid
Add the --permanent option to make it persistent.
To query whether the user ID uid is on the whitelist, enter the following command:
~]$ firewall-cmd --query-lockdown-whitelist-uid=uid
Prints yes with exit status 0, if true, prints no with exit status 1 otherwise.
To list all user names that are on the whitelist, enter the following command as
root: ~]# firewall-cmd --list-lockdown-whitelist-users
To add a user name user to the whitelist, enter the following command as
root: ~]# firewall-cmd --add-lockdown-whitelist-user=user
Add the --permanent option to make it persistent.
To remove a user name user from the whitelist, enter the following command as
root: ~]# firewall-cmd --remove-lockdown-whitelist-user=user
Add the --permanent option to make it persistent.
To query whether the user name user is on the whitelist, enter the following command:
~]$ firewall-cmd --query-lockdown-whitelist-user=user
Prints yes with exit status 0, if true, prints no with exit status 1 otherwise. 4.5.16.4. Configure Lockdown Whitelist Options with Configuration Files
The default whitelist configuration file contains the NetworkManager context and the default context of libvirt. Also the user ID 0 is in the list.
<?xml version="1.0" encoding="utf-8"?> <whitelist> <selinux context="system_u:system_r:NetworkManager_t:s0"/> <selinux context="system_u:system_r:virtd_t:s0-s0:c0.c1023"/> <user id="0"/> </whitelist>
Here follows an example whitelist configuration file enabling all commands for the
firewall-cmd utility, for a user called user whose user ID is 815: <?xml version="1.0" encoding="utf-8"?> <whitelist> <command name="/usr/bin/python -Es /bin/firewall-cmd*"/> <selinux context="system_u:system_r:NetworkManager_t:s0"/> <user id="815"/> <user name="user"/> </whitelist>In this example we have shown both
user id and user name but only one is required. Python is the interpreter and therefore prepended to the command line. You can also use a very specific command, for example: /usr/bin/python /bin/firewall-cmd --lockdown-on--lockdown-on command will be allowed.
Note
In Red Hat Enterprise Linux 7, all utilities are now placed in
/usr/bin/ and the /bin/ directory is sym-linked to the /usr/bin/ directory. In other words, although the path for firewall-cmd when run as root might resolve to /bin/firewall-cmd, /usr/bin/firewall-cmd can now be used. All new scripts should use the new location but be aware that if scripts that run as root have been written to use the /bin/firewall-cmd path then that command path must be whitelisted in addition to the /usr/bin/firewall-cmd path traditionally used only for non-root users.
The “*” at the end of the name attribute of a command means that all commands that start with this string will match. If the “*” is not there then the absolute command including arguments must match.
4.5.17. Additional Resources
The following sources of information provide additional resources regarding
firewalld. 4.5.17.1. Installed Documentation
firewalld(1)man page — Describes command options forfirewalld.firewalld.conf(5)man page — Contains information to configurefirewalld.firewall-cmd(1)man page — Describes command options for thefirewalldcommand line client.firewalld.icmptype(5)man page — Describes XML configuration files forICMPfiltering.firewalld.service(5)man page — Describes XML configuration files for firewalld service.firewalld.zone(5)man page — Describes XML configuration files forfirewalldzone configuration.firewalld.direct(5)man page — Describes thefirewallddirect interface configuration file.firewalld.lockdown-whitelist(5)man page — Describes thefirewalldlockdown whitelist configuration file.firewall.richlanguage(5)man page — Describes thefirewalldrich language rule syntax.firewalld.zones(5)man page — General description of what zones are and how to configure them.
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