Ansible Role - NFTables

Role to provision NFTables firewall on linux servers.

Molecule Logs: Short, Full

Tested:

• Debian 11
• Debian 12

---

Install

# latest
ansible-galaxy role install git+https://github.com/ansibleguy/infra_nftables

# from galaxy
ansible-galaxy install ansibleguy.infra_nftables

# or to custom role-path
ansible-galaxy install ansibleguy.infra_nftables --roles-path ./roles

---

Documentation

• NFTables: Wiki
• Check out the Example!
• Practical Use-Cases (Docker, Proxmox, Network firewall)
  • Integration of Fail2Ban with NFTables
• Troubleshooting Guide

Troubleshoot

• Troubleshooting Guide

---

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---

Usage

Config

Define the config as needed:

nftables:
  # enable:  # features must be supported by kernel
  #   sets: true
  #   nat: true
  #   deb11_backport: false  # use debian11 backports repository to install newer version on debian 10
  #   bash_completion: false

  _defaults:  # defaults inherited by all tables and chains
    table:
      type: 'inet'
    
    chain:
      policy: 'drop'
      type: 'filter'
      priority: 0
      log:
        drop: true

    rules:
      _all: []  # rules added to all chains of all tables
      incoming: []  # rules added to 'incoming' chain of all tables

  tables:
    example:
      # type: 'inet'  # ipv4 + ipv6
      _defaults:
        rules:
          _all: []  # rules added to all chains of this table

      vars:
        dns_servers: ['1.1.1.1', '1.1.0.0', '8.8.8.8', '8.8.4.4']
        private_ranges: ['192.168.0.0/16', '172.16.0.0/12', '10.0.0.0/8']

      sets:
        blacklist:
          flags: ['dynamic', 'timeout']
          settings:
            timeout: '3m'

      counters:
        invalid_packages:
          comment: 'Invalid'

      chains:
        incoming:
          hook: 'input'
          rules:
            - sequence: 1
              raw: 'ct state invalid counter name invalid_packages log prefix "DROP invalid states" drop'
            - seq: 2
              raw: 'ct state {established, related} counter accept comment "Allow open sessions"'
            - s: 3
              raw: 'iifname "lo" accept comment "Allow loopback traffic"'
            - {proto: 'icmp', type: 'echo-request', limit: 'rate 10/second', comment: 'Allow icmp-ping'}
            - {proto: 'icmpv6', type: 'echo-request', limit: 'rate 10/second', comment: 'Allow icmp-ping'}
            - {proto: 'icmp', code: 30, limit: 'rate 10/second', comment: 'Allow icmp-traceroute'}
            - {proto: 'icmpv6', limit: 'rate 10/second', comment: 'Allow necessary icmpv6-types for ipv6 to work',
               type: ['nd-neighbor-solicit', 'nd-router-advert', 'nd-neighbor-advert']}
            - {proto: 'udp', port: 46251, counter: 'invalid_packages'}

        outgoing:
          hook: 'output'
          # policy: 'accept'
          rules:
            - {dest: '$dns_servers', proto: 'udp', port: 53}
            - {dest: '$dns_servers', proto: 'tcp', port: [53, 853]}
            - {proto: ['tcp', 'udp'], port: [80, 443]}
            - {proto: ['icmp', 'icmpv6'], comment: 'Allow outbound icmp'}

        route:
          hook: 'forward'

        translate:
          hook: 'postrouting'
          type: 'nat'
          policy: 'accept'
          rules:
            - {'src': '$private_ranges', oif: 'eno2', masquerade: true}  # dynamic outbound nat
            - {'src': '$private_ranges', oif: 'eno3', snat: '192.168.0.1'}  # static outbound nat

If you want to merge group- & host-rules you could do it like that:

# define the basic ruleset used by all hosts as: 'fw_rules_all'
# define service-specific rules as: 'fw_rules_group'
# define host-specific rules as: 'fw_rules_host'

- name: NFTables
  become: true
  hosts: all
  vars:
    nftables:
      tables:
        example:
          chains: "{{ fw_rules_all |
          combine(fw_rules_group|default({}), recursive=true, list_merge='append') |
          combine(fw_rules_host|default({}), recursive=true, list_merge='append') }}"

  pre_tasks:
    - debug:
        var: nftables

  roles:
    - ansibleguy.infra_nftables

Execution

Run the playbook:

ansible-playbook -K -D -i inventory/hosts.yml playbook.yml

There are also some useful tags available:

• config_table => only provision actual rulesets
• config
• purge

To debug errors - you can set the 'debug' variable at runtime:

ansible-playbook -K -D -i inventory/hosts.yml playbook.yml -e debug=yes

---

Functionality

• Package installation

  • Ansible dependencies (minimal)
  • NFTables

• Configuration

  • Possibility to define

    • variables on global level
    • variables, sets, counters and limits on table level
    • variables on chain level

  • Config will be validated before being written

  • Default config:

    • Enabled features (must be supported by kernel)
      • Sets
      • NAT
    • No rules are added by default
    • tables
      • table-type = inet
    • chains
      • chain-type = filter
      • chain-policy = drop
      • priority = 0
      • add counter = yes
      • log implicit dropy = yes
    • sets
      • set-type = ipv4_addr
      • add counter = yes
    • rules
      • policy = accept (set it to 'none' if you want to explicitly remove it)
      • logging drops = yes

  • Default opt-ins:

    • Purging of unmanaged config-files stored in '/etc/nftables.d/'

  • Default opt-outs:

    • Installing NFTables from Debian 11 backports when running on Debian 10 (newer version)
    • Adding bash-completion script for the 'nft' command

---

Info

• Note: Most of the role's functionality can be opted in or out.

  For all available options - see the default-config located in the main defaults-file!

• Warning: Not every setting/variable you provide will be checked for validity. Bad config might break the role!

• Info: You can add DNS-Resolution and IP-Blocklist functionalities to NFTables using the ansibleguy.addons_nftables role!

• Warning: Some core functionalities (NAT/Sets) might not be supported by mainstream Distribution kernels.

  See: Troubleshooting Guide - 'Unsupported Operation'

• Info: Read the Hook documentation to know when and how to configure hooks and priorities!

• Info: Rules can be provided in dictionary format as seen in the examples.

  These are the available fields and aliases:

  Function	Keys	Note
  Rule sequence	s, id, seq, sequence	The sequence-id (integer) to sort the rules inside a chain. If none is provided one will be auto-generated beginning at 1000. If a duplicate sequence id is provided the role will fail its config-check!
  Input interface	if, iif, iifname	-
  Output interface	of, oif, oifname	-
  Protocol	proto, pr, protocol	-
  Protocol sub-type	t, type	-
  Protocol sub-code	co, code	-
  Destination Address/Network	d, dest, target, destination, 'ip daddr', d6, dest6, target6, 'ip6 daddr'	-
  Destination Port	dp, port, dport, dest_port	-
  Source Address/Network	s, src, source, 'ip saddr', s6, src6, source6, 'ip6 saddr'	-
  Source Port	sp, sport, sport, src_port	-
  Logging / Log message	l, log, 'log prefix'	If set to 'True' and a 'comment' is provided, it will be used as message. Else no message will be used
  Traffic counter	count, counter	If set to 'True' a rule-specific counter will be used. Else it will use the provided pre-defined counter
  Traffic Limit	lim, limit	A limit to set for the rule, see: Anonymous Limits and Pre-defined Limits
  Rule action	a, action	If no action is provided, it will default to 'accept'
  Source NAT masquerading	m, masque, masquerade	If NAT masquerading should be used
  Source NAT	snat, src_nat, source_nat, outbound_nat, 'snat to'	-
  Destination NAT	dnat, dest_nat, destination_nat, 'dnat to'	-
  Redirect	redir, redirect, 'redirect to'	By using redirect, packets will be forwarded to local machine
  Rule comment	c, cmt, comment	-
  User	user, uid	Match only traffic originating from specific user
  Group	group, gid	Match only traffic originating from specific group
  Firewall-Mark	mark	-
  Priority	prio, priority	-
  Packet length	len, length	-
  Timestamp	time, timestamp	Match timestamp of packet reception
  Weekday	day	Match day of week (0 = Sunday to 6 = Saturday or "Monday", "tuesday" also "fri", "Sat")
  Time	hour	Match 24-hour "HH:MM:SS", with seconds optional

  Only one of Action, Source-NAT, Masquerading or Destination-NAT can be set for one rule!

• Info: Special/complex rules cannot be configured using the rule-dictionary.

  You can use the 'raw' key to provide any custom rule that will be added to the ruleset directly.

• Info: You can define variables, sets, counters and limits on table-level.

  • Variables are key-value pairs.

    var-name: var-value
    var2-name: ['value1', 'value2']

  • Sets have this structure:

    set-name:
      flags: [list-of-flags]  # optional
      settings:
        setting: value  # optional

  • Counters have this structure:

    counter-name:
      comment: text  # optional

  • Limits have this structure:

    limit-name:
      rate: 'over 1024 bytes/second burst 512 bytes'
      comment: text  # optional

• Warning: If you want to add a 'count-only' rule you need to set 'action' explicitly to 'none' - else the default value 'accept' will be added!

• Info: If any unsupported field is supplied to the rule-translation it will throw an error as this might lead to unexpected results!

• Info: Docker might need IPTables as Package-Dependency.

  See: Use-Case Docker Host