iptables

Use the iptables InSpec audit resource to test rules that are defined in iptables, which maintains tables of IP packet filtering rules. There may be more than one table. Each table contains one (or more) chains (both built-in and custom). A chain is a list of rules that match packets. When the rule matches, the rule defines what target to assign to the packet.


Syntax

A iptables resource block declares tests for rules in IP tables:

describe iptables(rule:'name', table:'name', chain: 'name') do
  it { should have_rule('RULE') }
end

where

  • iptables() may specify any combination of rule, table, or chain
  • rule:'name' is the name of a rule that matches a set of packets
  • table:'name' is the packet matching table against which the test is run
  • chain: 'name' is the name of a user-defined chain or one of ACCEPT, DROP, QUEUE, or RETURN
  • have_rule('RULE') tests that rule in the iptables list. This must match the entire line taken from iptables -S CHAIN.


Examples

The following examples show how to use this InSpec audit resource.

Test if the INPUT chain is in default ACCEPT mode

describe iptables do
  it { should have_rule('-P INPUT ACCEPT') }
end

Test if the INPUT chain from the mangle table is in ACCEPT mode

describe iptables(table:'mangle', chain: 'INPUT') do
  it { should have_rule('-P INPUT ACCEPT') }
end

Test if there is a rule allowing Postgres (5432/TCP) traffic

describe iptables do
  it { should have_rule('-A INPUT -p tcp -m tcp -m multiport --dports 5432 -m comment --comment "postgres" -j ACCEPT') }
end

Note that the rule specification must exactly match what’s in the output of iptables -S INPUT, which will depend on how you’ve built your rules.


Matchers

For a full list of available matchers, please visit our matchers page.

have_rule

The have_rule matcher tests the named rule against the information in the iptables file:

it { should have_rule('RULE') }