firewall

This role configures the firewall on machines that are using firewalld. If firewalld is not in use, the role will install (if not already installed), unmask, and enable firewalld.

The role can also attempt to disable known conflicting services.

For the configuration the role uses the firewalld client interface which is available in RHEL-7 and later.

Supported Distributions

• RHEL-7+, CentOS-7+
• Fedora

Limitations

Configuration over Network

The configuration of the firewall could limit access to the machine over the network. Therefore it is needed to make sure that the SSH port is still accessible for the ansible server.

The Error Case

WARNING: If the configuration failed or if the firewall configuration limits access to the machine in a bad way, it is most likely be needed to get physical access to the machine to fix the issue.

Ansible Facts

Gathering firewall ansible facts

To gather the firewall system role's ansible facts, call the system role with no arguments e.g.

vars:
  firewall:

Another option is to gather a more detailed version of the ansible facts by using the detailed argument e.g.

vars:
  firewall:
    detailed: true

WARNING: `firewall_config` uses considerably more memory (+ ~165KB) when `detailed=True`.
For reference, by default, `firewall_config` takes ~3KB when converted to a string.

Available ansible facts

firewall_config

This ansible fact shows the permanent configuration of of firewalld on the managed node in dictionary format. The top level of the fact is made up of three keys:

• default
• custom
• default_zone

Each dictionaries custom and default have the keys:

• zones
• services
• icmptypes
• helpers
• ipsets
• policies (if supported by remote host's firewalld installation)

Each of the keys contains a list of elements present in permanent configuration for each respective option.

custom will have a list of subdictionaries for each key, providing a more detailed description.

default will have only the names of each setting, unless the detailed option is supplied, in which case it will be structured in the same manner as custom.

default_zone contains the configured default zone for the managed node's firewalld installation. It is a string value.

JSON representation of the structure of firewall_config fact:

{
  "default": {...},
  "custom": {...},
  "default_zone": "public",
}

default

The default subdictionary of firewall_config contains the default configuration for the managed node's firewalld configuration. This subdictionary only changes with changes to the managed node's firewalld installation.

default without detailed parameter set to true

"default": {
  "zones": ["public",...],
  "services": ["amanda_client",...],
  "icmptypes": [...],
  "helpers": [...],
  "ipsets": [...],
  "policies": [...],
}

default when parameter set to true

"default": {
  "zones": {
    "public": {
      ...
    },
    ...
  },
  "services": {
    "amanda_client":{
      ...
    },
    ...
  },
  "icmptypes": {
    ...
  },
  "helpers": {
    ...
  },
  "ipsets": {
    ...
  },
  "policies": {
    ...
  },
}

custom

The custom subdictionary contains any differences from the default firewalld configuration. This includes a repeat for a default element if that element has been modified in any way, and any new elements introduced in addition to the defaults.

This subdictionary will be modified by any changes to the firewalld installation done locally or remotely via the firewall system role.

If the managed nodes firewalld settings are not different from the defaults, the custom key and subdictionary will not be present in firewall_config. Additionally, if any of firewalld's settings have not changed from the default, there will not be a key-value pair for that setting in custom.

Below is the state of the custom subdictionary where at least one permanent change was made to each setting:

"custom": {
  "zones": {
    "custom_zone": {
      ...
    },
    ...
  },
  "services": {
    "custom_service": {
      ...
    },
    ...
  },
  "icmptypes": {
    "custom": {
      ...
    },
    ...
  },
  "helpers": {
    ...
  },
  "ipsets": {
    ...
  },
  "policies": {
    ...
  },
}

Variables

firewall_disable_conflicting_services

By default, the firewall role does not attempt to disable conflicting services due to the overhead associated with enumerating the services when disabling services is potentially unecessary. To enable this feature, set the variable firewall_disable_conflicting_services to true:

- name: Enable firewalld, disable conflicting services
  include_role: linux-system-roles.firewall
  vars:
    firewall_disable_conflicting_services: true

List of known conflicting services:

• iptables
• nftables
• ufw

Please submit a GitHub issue at the linux-system-roles/firewall there are services missing or add it locally to vars/main.yml.

firewall

The firewall role uses the variable firewall to specify the parameters. This variable is a list of dict values. Each dict value is comprised of one or more keys listed below. These are the variables that can be passed to the role:

firewalld_conf

firewalld_conf can be used to modify directives in firewalld's configuration file (/etc/firewalld/conf by default) if support for their modification has been implemented.

permanent: true must always be set to run this option without error

firewall:
  - firewalld_conf:
      allow_zone_drifting: false
    permanent: true

Supported Directives

allow_zone_drifting

Changes the AllowZoneDrifting directive.

This parameter will do nothing if AllowZoneDrifting has been deprecated and no longer exists.

firewall:
  firewalld_conf:
    allow_zone_drifting: true
  permanent: true

set_default_zone

The default zone is the zone that is used for everything that is not explicitly bound/assigned to another zone.

That means that if there is no zone assigned to a connection, interface or source, only the default zone is used. The zone should exist before setting it as the default zone.

firewall:
  - zone: mycustomzone  # ensure custom zone exists first
    state: present
  - set_default_zone: mycustomzone  # set custom as default
    state: enabled

zone

Name of the zone that should be modified. If it is not set, the default zone will be used. It will have an effect on these variables: service, port, source_port, forward_port, masquerade, rich_rule, source, interface, icmp_block, icmp_block_inversion, and target.

You can also use this to add/remove user-created zones. Specify the zone variable with no other variables, and use state: present to add the zone, or state: absent to remove it.

zone: public

service

Name of a service or service list to add or remove inbound access to.

service: ftp
service: [ftp,tftp]

If a specified service does not exist in firewalld, the module will fail in diff mode, and when run in check mode will always report no changes and warn the user of the potential for failure.

User defined services

You can use service with state: present to add a service, along with any of the options short, description, port, source_port, protocol, helper_module, or destination to initialize and add options to the service e.g.

firewall:
  # Adds custom service named customservice,
  # defines the new services short to be "Custom Service",
  # sets its description to "Custom service for example purposes,
  # and adds the port 8080/tcp
  - service: customservice
    short: Custom Service
    description: Custom service for example purposes
    port: 8080/tcp
    state: present
    permanent: true

Existing services can be modified in the same way as you would create a service. short, description, and destination can be reassigned this way, while port, source port, protocol, and helper_module will add the specified options if they did not exist previously without removing any previous elements. e.g.

firewall:
  # changes ftp's description, and adds the port 9090/tcp if it was not previously present
  - service: ftp
    description: I am modifying the builtin service ftp's description as an example
    port: 9090/tcp
    state: present
    permanent: true

You can remove a service or specific port, source_port, protocol, helper_module elements (or destination attributes) by using service with state: absent with any of the removable attributes listed. e.g.

firewall:
  # Removes the port 8080/tcp from customservice if it exists.
  # DOES NOT REMOVE CUSTOM SERVICE
  - service: customservice
    port: 8080/tcp
    state: absent
    permanent: true
  # Removes the service named customservice if it exists
  - service: customservice
    state: absent
    permanent: true

NOTE: permanent: true needs to be specified in order to define, modify, or remove a service. This is so anyone using service with state: present/absent acknowledges that this will affect permanent firewall configuration. Additionally, defining services for runtime configuration is not supported by firewalld

For more information about custom services, see https://firewalld.org/documentation/man-pages/firewalld.service.html

port

Port or port range or a list of them to add or remove inbound access to. It needs to be in the format <port>[-<port>]/<protocol>.

port: '443/tcp'
port: ['443/tcp','443/udp']

source_port

Port or port range or a list of them to add or remove source port access to. It needs to be in the format <port>[-<port>]/<protocol>.

source_port: '443/tcp'
source_port: ['443/tcp','443/udp']

forward_port

Add or remove port forwarding for ports or port ranges for a zone. It takes two different formats:

• string or a list of strings in the format like firewall-cmd --add-forward-port e.g. <port>[-<port>]/<protocol>;[<to-port>];[<to-addr>]
• dict or list of dicts in the format like ansible.posix.firewalld:

forward_port:
  port: <port>
  proto: <protocol>
  [toport: <to-port>]
  [toaddr: <to-addr>]

examples

forward_port: '447/tcp;;1.2.3.4'
forward_port: ['447/tcp;;1.2.3.4','448/tcp;;1.2.3.5']
forward_port:
  - 447/tcp;;1.2.3.4
  - 448/tcp;;1.2.3.5
forward_port:
  - port: 447
    proto: tcp
    toaddr: 1.2.3.4
  - port: 448
    proto: tcp
    toaddr: 1.2.3.5

port_forward is an alias for forward_port. Its use is deprecated and will be removed in an upcoming release.

masquerade

Enable or disable masquerade on the given zone.

masquerade: false

rich_rule

String or list of rich rule strings. For the format see (Syntax for firewalld rich language rules)[https://firewalld.org/documentation/man-pages/firewalld.richlanguage.html]

rich_rule: rule service name="ftp" audit limit value="1/m" accept

source

List of source address or address range strings. A source address or address range is either an IP address or a network IP address with a mask for IPv4 or IPv6. For IPv4, the mask can be a network mask or a plain number. For IPv6 the mask is a plain number.

source: 192.0.2.0/24

interface

String or list of interface name strings.

interface: eth2

This role handles interface arguments similar to how firewalld's cli, firewall-cmd does, i.e. manages the interface through NetworkManager if possible, and handles the interface binding purely through firewalld otherwise.

WARNING: Neither firewalld nor this role throw any
errors if the interface name specified is not
tied to any existing network interface. This can cause confusion
when attempting to add an interface via PCI device ID,
for which you should use the parameter `interface_pci_id`
instead of the `interface` parameter.

Allow interface named '8086:15d7' in dmz zone

firewall:
  - zone: dmz
    interface: 8086:15d7
    state: enabled

The above will successfully add a nftables/iptables rule
for an interface named `8086:15d7`, but no traffic should/will
ever match to an interface with this name.

TLDR - When using this parameter, please stick only to using
logical interface names that you know exist on the device to 
avoid confusing behavior.

interface_pci_id

String or list of interface PCI device IDs. Accepts PCI IDs if the wildcard XXXX:YYYY applies where:

• XXXX: Hexadecimal, corresponds to Vendor ID
• YYYY: Hexadecimal, corresponds to Device ID

# PCI id for Intel Corporation Ethernet Connection
interface_pci_id: 8086:15d7

Only accepts PCI devices IDs that correspond to a named network interface, and converts all PCI device IDs to their respective logical interface names.

If a PCI id corresponds to more than one logical interface name, all interfaces with the PCI id specified will have the play applied.

A list of PCI devices with their IDs can be retrieved using lcpci -nn. For more information on PCI device IDs, see the linux man page at: https://man7.org/linux/man-pages/man5/pci.ids.5.html

icmp_block

String or list of ICMP type strings to block. The ICMP type names needs to be defined in firewalld configuration.

icmp_block: echo-request

icmp_block_inversion

ICMP block inversion bool setting. It enables or disables inversion of ICMP blocks for a zone in firewalld.

icmp_block_inversion: true

target

The firewalld zone target. If the state is set to absent,this will reset the target to default. Valid values are "default", "ACCEPT", "DROP", "%%REJECT%%".

target: ACCEPT

short

Short description, only usable when adding or modifying a service. See service for more usage information.

short: WWW (HTTP)

description

Description for a service, only usable when adding a new service or modifying an existing service. See service for more information

description: Your description goes here

destination

list of destination addresses, option only implemented for user defined services. Takes 0-2 addresses, allowing for one IPv4 address and one IPv6 address or address range.

• IPv4 format: x.x.x.x[/mask]
• IPv6 format: x:x:x:x:x:x:x:x[/mask] (x::x works when abbreviating one or more subsequent IPv6 segments where x = 0)

destination:
  - 1.1.1.0/24
  - AAAA::AAAA:AAAA

helper_module

Name of a connection tracking helper supported by firewalld.

# Both properly specify nf_conntrack_ftp
helper_module: ftp
helper_module: nf_conntrack_ftp

timeout

The amount of time in seconds a setting is in effect. The timeout is usable if

• state is set to enabled
• firewalld is running and runtime is set
• setting is used with services, ports, source ports, forward ports, masquerade, rich rules or icmp blocks

timeout: 60
state: enabled
service: https

state

Enable or disable the entry.

state: 'enabled' | 'disabled' | 'present' | 'absent'

NOTE: present and absent are only used for zone, target, and service operations, and cannot be used for any other operation.

NOTE: zone - use state: present to add a zone, and state: absent to remove a zone, when zone is the only variable e.g.

firewall:
  - zone: my-new-zone
    state: present

NOTE: target - you can also use state: present to add a target - state: absent will reset the target to the default.

NOTE: service - to see how to manage services, see the service section.

runtime

Enable changes in runtime configuration. If runtime parameter is not provided, the default will be set to True.

runtime: true

permanent

Enable changes in permanent configuration. If permanent parameter is not provided, the default will be set to True.

permanent: true

The permanent and runtime settings are independent, so you can set only the runtime, or only the permanent. You cannot set both permanent and runtime to false.

previous

If you want to completely wipe out all existing firewall configuration, add previous: replaced to the firewall list. This will cause all existing configuration to be removed and replaced with your given configuration. This is useful if you have existing machines that may have existing firewall configuration, and you want to make all of the firewall configuration the same across all of the machines.

WARNING: When using this option, there's a small time window when firewall is being reset and all new connections to the system are rejected. Existing connections will be unaffected. Applying changes with this option in production might cause temporary service failures with new connections during the operation.

Examples of Options

By default, any changes will be applied immediately, and to the permanent settings. If you want the changes to apply immediately but not permanently, use permanent: false. Conversely, use runtime: false.

Permit TCP traffic for port 80 in default zone, in addition to any existing configuration:

firewall:
  - port: 80/tcp
    state: enabled

Remove all existing firewall configuration, and permit TCP traffic for port 80 in default zone:

firewall:
  - previous: replaced
  - port: 80/tcp
    state: enabled

Do not permit TCP traffic for port 80 in default zone:

firewall:
  - port: 80/tcp
    state: disabled

Add masquerading to dmz zone:

firewall:
  - masquerade: true
    zone: dmz
    state: enabled

Remove masquerading to dmz zone:

firewall:
  - masquerade: false
    zone: dmz
    state: enabled

Allow interface eth2 in trusted zone:

firewall:
  - interface: eth2
    zone: trusted
    state: enabled

Don't allow interface eth2 in trusted zone:

firewall:
  - interface: eth2
    zone: trusted
    state: disabled

Permit traffic in default zone for https service:

firewall:
  - service: https
    state: enabled

Do not permit traffic in default zone for https service:

firewall:
  - service: https
    state: disabled

Allow interface with PCI device ID '8086:15d7' in dmz zone

firewall:
  - zone: dmz
    interface_pci_id: 8086:15d7
    state: enabled

Example Playbooks

Erase all existing configuration, and enable ssh service:

---
- name: Erase existing config and enable ssh service
  hosts: myhost

  vars:
    firewall:
      - previous: replaced
      - service: ssh
        state: enabled
  roles:
    - linux-system-roles.firewall

With this playbook you can make sure that the tftp service is disabled in the firewall:

---
- name: Make sure tftp service is disabled
  hosts: myhost

  vars:
    firewall:
      - service: tftp
        state: disabled
  roles:
    - linux-system-roles.firewall

It is also possible to combine several settings into blocks:

---
- name: Configure firewall
  hosts: myhost

  vars:
    firewall:
      - {service: [tftp,ftp],
         port: ['443/tcp','443/udp'],
         state: enabled}
      - {forward_port: [eth2;447/tcp;;1.2.3.4,
                        eth2;448/tcp;;1.2.3.5],
          state: enabled}
      - {zone: internal, service: tftp, state: enabled}
      - {service: tftp, state: enabled}
      - {port: '443/tcp', state: enabled}
      - {forward_port: 'eth0;445/tcp;;1.2.3.4', state: enabled}
         state: enabled}
  roles:
    - linux-system-roles.firewall

The block with several services, ports, etc. will be applied at once. If there is something wrong in the block it will fail as a whole.

---
- name: Configure external zone in firewall
  hosts: myhost

  vars:
    firewall:
      - {zone: external,
         service: [tftp,ftp],
         port: ['443/tcp','443/udp'],
         forward_port: ['447/tcp;;1.2.3.4',
                        '448/tcp;;1.2.3.5'],
         state: enabled}
  roles:
    - linux-system-roles.firewall

Authors

Thomas Woerner

License

GPLv2+