iptables-ng Cookbook

This cookbook maintains and installs iptables and ip6tables rules, trying to keep as close to the way the used distribution maintains their rules.

Contrary to other iptables cookbooks, this cookbook installs iptables and maintains rules using the distributions default configuration files and services (for Debian and Ubuntu, iptables-persistent is used). If the distribution has no service for iptables, it falls back to iptables-restore.

It provides LWRPs as well as recipes which can handle iptables rules set in the nodes attributes.

It uses the directory /etc/iptables.d to store and maintain its rules. I'm trying to be as compatible as much as possible to all distributions out there.

This cookbook is supposed to be able to:

• Configure iptables rules in a consistent and nice way for all distributions
• Be configured by using LWRPs only
• Be configured by using node attributes only
• Respect the way the currently used distribution stores their rules
• Provide a good-to-read and good-to-maintain way of deploying complex iptables rulesets
• Provide a way of specifying the order of the iptables rules, in case needed
• Only run iptables-restore once during a chef run, and only if something was actually changed
• Support both, ipv6 as well as ipv4
• Be able to assemble iptables rules from different recipes (and even cookbooks), so you can set your iptables rule where you actually configure the service

I also wrote a blog post providing further insights.

Requirements

The following distribution are best supported, but as this recipe falls back to a generic iptables restore script in case the system is unknown, it should work with every linux distribution supporting iptables.

• Ubuntu 16.04, 18.04
• Debian 8, 9
• RHEL 6, 7
• Gentoo
• Archlinux

No external dependencies. Just add this line to your metadata.rb and you're good to go!

depends 'iptables-ng'

Attributes

General configuration (services, paths)

While iptables-ng tries to automatically determine the correct settings and defaults for your distribution, it might be necessary to adapt them in certain cases. You can configure the behaviour of iptables-ng using the following attributes:

# The ip versions to manage iptables for
node['iptables-ng']['enabled_ip_versions'] = [4, 6]

# Which tables to manage:
# When using a containered setup (OpenVZ, Docker, LXC) it might be
# necessary to remove the "nat" and "raw" tables.
node['iptables-ng']['enabled_tables'] = %w(nat filter mangle raw)

# An array of packages to install.
# This should install iptables and ip6tables,
# as well as a system service that takes care of reloading the rules
# On Debian and Ubuntu, iptables-persistent is used by default.
node['iptables-ng']['packages'] = %w(iptables)

# The name of the service that will be used to restart iptables
# By default, the system service of your distribution is used, so don't worry about it unless you
# have special requirements. If iptables-ng can't figure out the default service to use or these
# attributes are set to nil, iptables-ng will fall back to "iptables-restore"
node['iptables-ng']['service_ipv4'] = 'iptables-persistent'
node['iptables-ng']['service_ipv6'] = 'iptables-persistent'

# The location were the iptables-restore script will be written to
node['iptables-ng']['script_ipv4'] = '/etc/iptables/rules.v4'
node['iptables-ng']['script_ipv6'] = '/etc/iptables/rules.v6'

Rule configuration

The use of the LWRPs is recommended, but iptables-ng can be configured using attributes only.

You can set the default policies of a chain like this

node['iptables-ng']['rules']['filter']['INPUT']['default'] = 'DROP [0:0]'

And also add rules for a chain (this example allows SSH)

node['iptables-ng']['rules']['filter']['INPUT']['ssh']['rule'] = '--protocol tcp --dport 22 --match state --state NEW --jump ACCEPT'

You can prioritize your rules, too. This example will make sure that the 'ssh' rule is created before the 'http' rule

node['iptables-ng']['rules']['filter']['INPUT']['10-ssh']['rule'] = 'this rule is first'
node['iptables-ng']['rules']['filter']['INPUT']['90-http']['rule'] = 'this rule is applied later'

Also, it's possible to only apply a rule for a certain ip version.

node['iptables-ng']['rules']['filter']['INPUT']['10-ssh']['rule'] = '--protocol tcp --source 1.2.3.4 --dport 22 --match state --state NEW --jump ACCEPT'
node['iptables-ng']['rules']['filter']['INPUT']['10-ssh']['ip_version'] = 4

Auto-pruning

In Chef, it is generally accepted that removing node attributes does not result in their corresponding resources being proactively scrubbed from the system. However, this could be seen as irritating or even a security risk when dealing with firewall attribute rules in this cookbook. To automatically prune rules for attributes that have been removed, set the following attribute to true. This will not affect rules defined with the LWRP.

node['iptables-ng']['auto_prune_attribute_rules'] = true

Recipes

default

The default recipe calls the install recipe, and then configures all rules and policies given in the nodes attribute.

Example:

To allow only SSH for incoming connections, add this to your node configuration

{
  "name": "example.com",
  "chef_environment": "_default",
  "normal": {
    "iptables-ng": {
      "rules": {
        "filter": {
          "INPUT": {
            "default": "DROP [0:0]",
            "ssh": {
              "rule": "--protocol tcp --dport 22 --match state --state NEW --jump ACCEPT"
            }
          }
        }
      }
    }
  },
  "run_list": [
    "recipe[iptables-ng]"
  ]
}

In case you need a rule for one specific ip version, you can set the "ip_version" attribute.

"ssh": {
  "rule": "--protocol tcp --source 1.2.3.4 --dport 22 --match state --state NEW --jump ACCEPT",
  "ip_version": 4
}

You can also delete old rules by specifying a custom action.

"ssh": {
  "action": "delete"
}

install

The installs recipe installs iptables packages, makes sure that /etc/iptables.d is created and sets all default policies to "ACCEPT", unless they are already configured.

On Debian and Ubuntu systems, it also removes the "ufw" package, as it might interfere with this cookbook.

Note: This recipe needs to be run before the LWRPs are used!

include_recipe 'iptables-ng::install'

Providers

It's recommended to configure iptables-ng using LWRPs in your (wrapper) cookbook.

All providers take care that iptables is installed (they include the install recipe before running), so you can just use them without worrying whether everything is installed correctly.

iptables_ng_chain

This provider creates chains and adds their default policies.

Example: Set the default policy of the filter INPUT chain to ACCEPT:

iptables_ng_chain 'INPUT' do
  policy 'ACCEPT [0:0]'
end

Example: Create a custom chain:

iptables_ng_chain 'MYCHAIN'

The following additional attributes are supported:

iptables_ng_chain 'name' do
  chain  'INPUT'       # The chain to set the policy for (name_attribute)
  table  'filter'      # The table to use (defaults to 'filter')
  policy 'DROP [0:0]'  # The policy to use (defaults to 'ACCEPT [0:0]' for
                       # build-in chains, to '- [0:0]' for custom ones

  action :create       # Supported actions: :create, :create_if_missing, :delete
                       # Default action: :create
end

iptables_ng_rule

This provider adds iptables rules

Example: Allow SSH on the INPUT filter chain

iptables_ng_rule 'ssh' do
  rule '--protocol tcp --dport 22 --match state --state NEW --jump ACCEPT'
end

The following additional attributes are supported:

iptables_ng_rule 'custom' do
  name       'my-rule'    # Name of the rule. Use "xx-" to prioritize rules.
  chain      'INPUT'      # Chain to use. Defaults to 'INPUT' (custom chains need to be created using iptables_ng_chain first!)
  table      'filter'     # Table to use. Defaults to 'filter'
  ip_version 4            # Integer or Array of IP versions to create the rules for.
                          # Defaults to node['iptables-ng']['enabled_ip_versions']
  rule       '-j ACCEPT'  # String or Array containing the rule(s). (Required)

  action :create          # Supported actions: :create, :create_if_missing, :delete
                          # Default action: :create
end

Example: Allow HTTP and HTTPS for a specific IP range only

iptables_ng_rule 'ssh' do
  rule ['--source 192.168.1.0/24 --protocol tcp --dport 80 --match state --state NEW --jump ACCEPT',
        '--source 192.168.1.0/24 --protocol tcp --dport 443 --match state --state NEW --jump ACCEPT']

  # As the source specified above is ipv4, this rule cannot be applied to ip6tables.
  # Therefore, setting ip_version to 4
  ip_version 4
end

Example: Use the same rule for an array of IPs

ips = %w(10.10.10.1 123.123.123.123 192.168.1.0/24)

iptables_ng_rule 'multiple_source_addresses' do
  rule ips.map { |ip| "--source #{ip} --jump ACCEPT" }

  # As the source specified above is ipv4, this rule cannot be applied to ip6tables.
  # Therefore, setting ip_version to 4
  ip_version 4
end

Known issues

There are some issues with systemd support on Fedora systems. Also it might be required to install iptables-service on newer Fedora machines.
Due to this issues, the tests for Fedora were removed until they are resolved.
Furthermore, due to the lack of Opscode kitchen boxes, there are no tests for Archlinux.

Contributing

You fixed a bug, or added a new feature? Yippie!

1. Fork the repository on Github
2. Create a named feature branch (like add_component_x)
3. Write you change
4. Write tests for your change (if applicable)
5. Run the tests, ensuring they all pass
6. Submit a Pull Request using Github

Contributions of any sort are very welcome!

License and Authors

Authors: Chris Aumann

Contributors: Dan Fruehauf, Nathan Williams, Christian Graf, James Le Cuirot, Sten Spans, Cédric Félizard, Hans Rakers

Other licenses than GPLv3

In case you can't use the provided license for some reason, feel free to contact me.

Copyright (C) 2013-2018 Chris Aumann

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see http://www.gnu.org/licenses/.