firewall Cookbook

Provides a set of primitives for managing firewalls and associated rules.

PLEASE NOTE - The resource/providers in this cookbook are under heavy development. An attempt is being made to keep the resource simple/stupid by starting with less sophisticated firewall implementations first and refactor/vet the resource definition with each successive provider.

Maintainers

This cookbook is maintained by the Sous Chefs. The Sous Chefs are a community of Chef cookbook maintainers working together to maintain important cookbooks. If you’d like to know more please visit sous-chefs.org or come chat with us on the Chef Community Slack in #sous-chefs.

Requirements

• Chef Infra Client 15.5+

depends 'firewall'

Supported firewalls and platforms

• UFW (Uncomplicated Firewall)
• Firewalld
• IPTables
• Windows Firewall
• nftables

The default firewall solution used on Linux is based on the platform family:

Platform Family	Default Firewall Solution
amazon	firewalld
debian	ufw
fedora	firewalld
rhel	firewalld
suse	firewalld
ubuntu	ufw
windows	windows
Other	iptables

If you'd like to use a firewall solution other than the platform's default, set the default['firewall']['solution'] attribute to the desired firewall:

# firewalld
default['firewall']['solution'] = 'firewalld'

# iptables
default['firewall']['solution'] = 'iptables'

# ufw
default['firewall']['solution'] = 'ufw'

nftables

In order to use nftables, just use the resource nftables and nftables_rule. These resources are written in more modern design styles and are not configurable by node attributes.

Supported operating systems

See the kitchen.yml for the full matrix of platforms this cookbook is tested on.

Quickstart

To simply open a port in the system's default firewall:

include_recipe 'firewall'

firewall_rule 'ssh' do
  port 22
end

How it works

The most basic use involves two resources, firewall and firewall_rule. The typical usage scenario is as follows:

• include the 'firewall::default' recipe or run the :install action on the firewall resource named 'default', which installs appropriate packages and configures services to start on boot and starts them.
• run the :create action on every firewall_rule resource, which adds to the list of rules that should be configured on the firewall. How the rules are implemented depends on the firewall platform:
  • firewalld: firewall_rule implements the rules under the hood as firewalld rich rules in the system's default zone.
  • iptables, ufw, windows: firewall_rule automatically sends a delayed notification to the firewall['default'] resource to run the :restart action.
    • when the delayed :restart notification on the firewall resource fires, if any rules are different than the last run, the provider will update the current state of the firewall rules to match the expected rules.

There is a fundamental mismatch between the idea of a Chef action and the action that should be taken on a firewall rule. For this reason, the Chef action for a firewall_rule may be :create (the rule should be present in the firewall) but the action taken on a packet in a firewall (DROP, ACCEPT, etc) is denoted as a command property on the firewall_rule resource.

The same points hold for the nftables- and nftables_rule-resources.

iptables considerations

If you need to use a table other than *filter, the best way to do so is like so:

node.default['firewall']['iptables']['defaults'][:ruleset] = {
  '*filter' => 1,
  ':INPUT DROP' => 2,
  ':FORWARD DROP' => 3,
  ':OUTPUT ACCEPT_FILTER' => 4,
  'COMMIT_FILTER' => 100,
  '*nat' => 101,
  ':PREROUTING DROP' => 102,
  ':POSTROUTING DROP' => 103,
  ':OUTPUT ACCEPT_NAT' => 104,
  'COMMIT_NAT' => 200
}

Note -- in order to support multiple hash keys containing the same rule, anything found after the underscore will be stripped for: :OUTPUT :INPUT :POSTROUTING :PREROUTING COMMIT. This allows an example like the above to be reduced to just repeated lines of COMMIT and :OUTPUT ACCEPT while still avoiding duplication of other things.

Then it's trivial to add additional rules to the *nat table using the raw parameter:

firewall_rule "postroute" do
  raw "-A POSTROUTING -o eth1 -p tcp -d 172.28.128.21 -j SNAT --to-source 172.28.128.6"
  position 150
end

Note that any line starting with COMMIT will become just COMMIT, as hash keys must be unique but we need multiple commit lines.

nftables

Please read the documentation for the nftables resource and the nftables_rule resource

firewalld

For most rules it's sufficient to simply use the firewall_rule resource which is a platform-agnostic way to add firewall rules. On firewalld systems it adds rules to the default zone as firewalld rich rules. See the firewall_rule section for examples.

See the firewalld resources documentation for advanced firewalld configuration.

Recipes

firewall::default

The default recipe creates a firewall resource with action install.

firewall::disable_firewall

Used to disable platform specific firewall. Many clouds have their own firewall configured outside of the OS instance such as AWS Security Groups.

Attributes

• default['firewall']['solution'] = <firewalld|iptables|ufw>, sets the firewall solution to use on Linux platforms. Defaults to the default firewall solution used by the platform family. See Supported firewalls and platforms for more info.
• default['firewall']['allow_ssh'] = false, set true to open port 22 for SSH when the default recipe runs
• default['firewall']['allow_mosh'] = false, set to true to open UDP ports 60000 - 61000 for Mosh when the default recipe runs
• default['firewall']['allow_winrm'] = false, set true to open port 5989 for WinRM when the default recipe runs
• default['firewall']['allow_loopback'] = false, set to true to allow all traffic on the loopback interface
• default['firewall']['allow_icmp'] = false, set true to allow icmp protocol on supported OSes (note: ufw and windows implementations don't support this)
• default['firewall']['ufw']['defaults'] hash for template /etc/default/ufw
• default['firewall']['iptables']['defaults'] hash for default policies for 'filter' table's chains`
• default['firewall']['windows']['defaults'] hash to define inbound / outbound firewall policy on Windows platform
• default['firewall']['allow_established'] = true, set to false if you don't want a related/established default rule on iptables
• default['firewall']['ipv6_enabled'] = true, set to false if you don't want IPv6 related/established default rule on iptables (this enables ICMPv6, which is required for much of IPv6 communication)

Resources

firewall

It's not recommended to use this resource directly. Instead simply include_recipe 'firewall' and then add your desired firewall_rule resources. See the firewall_rule section for examples.

NB: The name 'default' of this resource is important as it is used for firewall_rule providers to locate the firewall resource. If you change it, you must also supply the same value to any firewall_rule resources using the firewall_name parameter.

Actions

• :install (default action): Install and Enable the firewall. This will ensure the appropriate packages are installed and that any services have been started.
• :reload: firewalld only. Reloads the runtime state to match the permanent configuration. All runtime-only rules are flushed out.
• :disable: Disable the firewall. Drop any rules and put the node in an unprotected state. Flush all current rules. Also erase any internal state used to detect when rules should be applied.
• :flush: Except firewalld. Flush all current rules. Also erase any internal state used to detect when rules should be applied.

Properties

• enabled (default to true): If set to false, all actions will no-op on this resource. This is a way to prevent included cookbooks from configuring a firewall.
• ipv6_enabled (default to true): Iptables only. If set to false, firewall will not perform any ipv6 related work.
• log_level: UFW only. Level of verbosity the firewall should log at. valid values are: :low, :medium, :high, :full, :off. default is :low.
• package_options: Pass additional options to the package manager when installing the firewall.

# all defaults
firewall 'default'

# enable platform default firewall
firewall 'default' do
  action :install
end

# increase logging past default of 'low'
firewall 'default' do
  log_level :high
  action    :install
end

firewall_rule

Actions

• :create: Create the firewall rule and notify the firewall to reload after the rule has been saved. On firewalld systems, the rules are added to the default zone as firewalld rich rules.

Properties

firewall_rule 'name' do
  firewall_name   String            # Default: 'default'
  command         Symbol            # Default: :allow
  protocol        Integer, Symbol   # Default: :tcp
  source          String
  source_port     Integer, Array, Range
  port            Integer, Array, Range
  dest_port       Integer, Array, Range
  destination     String
  position        Integer           # Default: 50
  description     String            # Default: 'name' unless specified

  # Firewall-specific properties
  zone            String            # Firewall: firewalld
  logging         Symbol            # Firewall: ufw
  redirect_port   Integer           # Firewall: iptables, firewalld
  dest_interface  String            # Firewall: iptables, windows
  interface       String            # Firewall: iptables, ufw, windows
  include_comment true, false       # Firewall: iptables, ufw. Default: true
  stateful        Symbol, Array     # Firewall: iptables, ufw
  raw             String            # Firewall: iptables, ufw
  direction       Symbol            # Firewall: iptables, ufw, windows. Default: :in
  notify_firewall true, false       # Firewall: iptables, ufw, windows. Default: true
  program         String            # Firewall: windows
  service         String            # Firewall: windows
end

Firewall-agnostic properties that can be used with firewall_rule on any firewall system:

• firewall_name: the matching firewall resource that this rule applies to. Default value: default
• description (default: same as rule name): Used to provide a comment that will be included when adding the firewall rule.
• command: What action to take on a particular packet
  • :allow (default action): the rule should allow matching packets
  • :deny: the rule should deny (drop) matching packets
  • :reject: the rule should reject matching packets
  • :masquerade: Masquerade the matching packets
  • :redirect: Redirect the matching packets
  • :log: Configure logging
• protocol: :tcp (default), :udp, :icmp, :none, or protocol number. Using protocol numbers is not supported using the ufw provider (default for debian/ubuntu systems).
• source (Default is 0.0.0.0/0 or Anywhere): source ip address or subnet to filter.
• source_port (Default is nil): source port for filtering packets.
• port or dest_port: target port number (ie. 22 to allow inbound SSH), an array of incoming port numbers (ie. [80,443] to allow inbound HTTP & HTTPS), or a range of incoming ports (12000..12100).
• destination: ip address or subnet to filter on packet destination, must be a valid IP
• position (default: 50): relative position to insert rule at. Position may be any integer between 0 < n < 100 (exclusive), and more than one rule may specify the same position.

Additional properties for advanced firewall rules that tied to specific firewall solutions. Note: These properties are not firewall-agnostic, so you must ensure they are used only on the appropriate firewall solutions:

• zone: (firewalld), a string, such as public that the rule will be applied. Defaults to the system's configured default zone.
• logging (ufw): may be added to enable logging for a particular rule. valid values are: :connections, :packets. In the ufw provider, :connections logs new connections while :packets logs all packets.
• redirect_port (iptables, firewalld): redirected port for rules with command :redirect.
• dest_interface (iptables, windows): interface where packets may be destined to go.
• interface (iptables, ufw, windows): (source) interface to apply rule (ie. eth0).
• include_comment (iptables, ufw): Used to optionally exclude the comment in the rule. Default: true.
• stateful (iptables, ufw): a symbol or array of symbols, such as ``[:related, :established]` that will be passed to the state module in iptables or firewalld.
• raw (iptables, ufw): Used to pass an entire rule as a string, omitting all other parameters. This line will be directly loaded by iptables-restore/fed directly into ufw on the command line.
• direction (iptables, ufw, windows): Direction of the rule. Valid values are: :in (default), :out, :pre, :post.
• notify_firewall (iptables, ufw, windows): Notify the firewall to recalculate (and potentially reapply) the firewall_rule(s) it finds. Default: true

Examples

include_recipe 'firewall'

# open standard ssh port
firewall_rule 'ssh' do
  port     22
  command  :allow
end

# open standard http port to tcp traffic only; insert as first rule
firewall_rule 'http' do
  port     80
  protocol :tcp
  position 1
  command   :allow
end

# open UDP ports 60000..61000 for mobile shell (mosh.org), note
# that the protocol attribute is required when using port_range
firewall_rule 'mosh' do
  protocol    :udp
  port        60000..61000
  command     :allow
end

# open multiple ports for http/https, note that the protocol
# attribute is required when using ports
firewall_rule 'http/https' do
  protocol :tcp
  port     [80, 443]
  command   :allow
end

# firewalld example of opening port 22 on public zone
firewall_rule 'ssh' do
  port    22
  zone    "public"
  command :allow
end

Troubleshooting

To figure out what the position values are for current rules, print the hash that contains the weights:

require pp
default_firewall = resources(:firewall, 'default')
pp default_firewall.rules

Development

This section details "quick development" steps. For a detailed explanation, see [[Contributing.md]].

1. Clone this repository from GitHub:

$ git clone [email protected]:chef-cookbooks/firewall.git

1. Create a git branch

$ git checkout -b my_bug_fix

1. Install dependencies:

$ bundle install

1. Make your changes/patches/fixes, committing appropiately
2. Write tests
3. Run the tests:

• bundle exec foodcritic -f any .
• bundle exec rspec
• bundle exec rubocop
• bundle exec kitchen test

In detail:

• Foodcritic will catch any Chef-specific style errors
• RSpec will run the unit tests
• Rubocop will check for Ruby-specific style errors
• Test Kitchen will run and converge the recipes

Contributors

This project exists thanks to all the people who contribute.

Backers

Thank you to all our backers!

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