nftables resource

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

Availability

Install

Version

This resource first became available in v5.21.30 of InSpec.

Syntax

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

describe nftables(family:'name', table:'name', chain: 'name') do
  its('PROPERTY') { should eq 'value' }
  it { should have_rule('RULE') }
end

describe nftables(family:'name', table:'name', set: 'name') do
  its('PROPERTY') { should eq 'value' }
  it { should have_element('ELEMENT') }
end

where

• nftables() has to specify family and table. It also has to specify one of chain or set (exclusively).
• family:'name' is the name of the family the table belongs to, one of ip, ip6, inet, arp, bridge, netdev.
• table:'name' is the packet matching table against which the test is run.
• chain: 'name' is the name of a user-defined chain.
• set: 'name' is the name of a user-defined named set.
• have_rule('RULE') tests that the chain has a given rule in the nftables ruleset. This must match the entire line taken from nftables -nn list chain FAMILY TABLE CHAIN.
• have_element('ELEMENT') tests that element is a member of the nftables named set.

See the NFT man page and nftables wiki for more information about nftables.

Properties

Chain Properties

hook

The hook type. Possible values: ingress, prerouting, forward, input, output, postrouting, and egress.

prio

The numerical chain priority.

policy

The policy type. Possible values: accept, drop.

type

The chain type. Possible values: filter, nat, and route.

Set Properties

flags

The set flags. Possible values: constant, dynamic, interval, and timeout.

size

The maximum number of elements in the set.

type

The data type of set elements. Possible values: ipv4_addr, ipv6_addr, ether_addr, inet_proto, inet_service, and mark.

Examples

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

Test if the CHAIN_NAME chain from the TABLE_NAME table has the default accept policy

describe nftables(family: 'inet', table: 'TABLE_NAME', chain: 'CHAIN_NAME') do
  its('policy') { should eq 'accept' }
end

Test the attributes of the CHAIN_NAME chain from the TABLE_NAME table

describe nftables(family: 'inet', table: 'mangle', chain: 'INPUT') do
  its('type') { should eq 'filter' }
  its('hook') { should eq 'input' }
  its('prio') { should eq (-150) } # mangle
  its('policy') { should eq 'accept' }
end

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

describe nftables(family: 'inet', table: 'TABLE_NAME', chain: 'CHAIN_NAME') do
  it { should have_rule('tcp dport 5432 comment "postgres" accept') }
end

Note that the rule specification must exactly match what’s in the output of nftables -nn list chain inet TABLE_NAME CHAIN_NAME, which will depend on how you’ve built your rules.

Test if there is an element 1.1.1.1 in the SET_NAME named set

describe nftables(family: 'inet', table: 'TABLE_NAME', set: 'SET_NAME') do
  it { should have_element('1.1.1.1') }
end

Matchers

This resource has the following special matchers.

have_rule

The have_rule matcher tests the named rule against the information in the nftables ruleset:

it { should have_rule('RULE') }

have_element

The have_element matcher tests the named set against the information in the nftables ruleset:

it { should have_element('SET_ELEMENT') }