aws_subnets Resource

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Use the aws_subnets InSpec audit resource to test properties of some or all subnets.

Subnets are networks within a VPC that can have their own block of IP address’s and ACL’s. VPCs span across all availability zones in AWS, while a subnet in a VPC can only span a single availability zone. Separating IP addresses allows for protection if there is a failure in one availability zone.

For additional information, including details on parameters and properties, see the AWS documentation on Subnets.

Installation

This resource is available in the Chef InSpec AWS resource pack.

See the Chef InSpec documentation on cloud platforms for information on configuring your AWS environment for InSpec and creating an InSpec profile that uses the InSpec AWS resource pack.

Syntax

An aws_subnets resource block uses an optional filter to select a group of subnets and then tests that group.

# Test all subnets within a single vpc

describe aws_subnets.where(vpc_id: 'vpc-12345678') do
  its('subnet_ids') { should include 'subnet-12345678' }
  its('subnet_ids') { should include 'subnet-98765432' }
end

Parameters

This resource does not require any parameters.

Properties

subnet_ids

The name of the auto scaling launch configuration associated with the auto scaling group.

vpc_ids

An integer indicating the maximum number of instances in the auto scaling group.

cidr_blocks

An integer indicating the minimum number of instances in the auto scaling group.

availability_zone

The availability zone this subnet is part of.

map_public_ip_on_launch

A boolean indicating if a public IP is automatically mapped to instances launched in this subnet.

states

An array of strings corresponding to the subnet IDs associated with the auto scaling group.

entries

Provides access to the raw results of the query, which can be treated as an array of hashes.

tags

Array of arrays of hashes with existing tags.

Examples

Look for all subnets within a vpc.

describe aws_subnets.where(vpc_id: 'vpc-12345678') do
  its('subnet_ids') { should include 'subnet-12345678' }
  its('subnet_ids') { should include 'subnet-98765432' }
end

Examine a specific subnet.

describe aws_subnets.where(subnet_id: 'subnet-12345678') do
  its('cidr_blocks') { should eq ['10.0.1.0/24'] }
end

Examine a specific vpcs Subnet IDs.

describe aws_subnets.where(vpc_id: 'vpc-12345678') do
  its('states') { should_not include 'pending' }
end

Examine a specific subnets VPC IDS.

describe aws_subnets.where(subnet_id: 'subnet-12345678') do
  its('vpc_ids') { should include 'vpc-12345678' }
end

Check existing tags.

describe aws_subnets.where(vpc_id: vpc_id) do
  its('tags') { should include([{key: 'Name', value: 'My favourite subnet'}]) }
end

Matchers

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

exist

The control will pass if the describe returns at least one result.

Use should_not to test the entity should not exist.

describe aws_subnets.where( <property>: <value>) do
  it { should exist }
end

describe aws_subnets.where( <property>: <value>) do
  it { should_not exist }
end

AWS Permissions

Your Principal will need the EC2:Client:DescribeSubnetsResult action with Effect set to Allow.

You can find detailed documentation at Actions, Resources, and Condition Keys for Amazon EC2.