Terraform AWS Base Networking

A Terraform module for building a base network in AWS.

The network consists of:

• Public and private subnets for each supplied availability zone
• A NAT gateway for each supplied availability zone for outbound Internet connectivity
• Routes from the public subnets to the Internet gateway
• Routes from the private subnets to the NAT
• Standard tags for all resources

Usage

To use the module, include something like the following in your Terraform configuration:

module "base-network" {
  source  = "infrablocks/base-networking/aws"
  version = "4.0.0"

  vpc_cidr           = "10.0.0.0/16"
  region             = "eu-west-2"
  availability_zones = ["eu-west-2a", "eu-west-2b"]

  component             = "important-component"
  deployment_identifier = "production"

  private_zone_id = "Z3CVA9QD5NHSW3"
}

See the Terraform registry entry for more details.

Inputs

Name	Description	Default	Required
vpc_cidr	The CIDR to use for the VPC.	-	Yes
region	The region into which to deploy the VPC.	-	Yes
availability_zones	The availability zones for which to add subnets.	-	Yes
public_subnets_offset	The number of /24s to offset the public subnets in the VPC CIDR.	0	No
private_subnets_offset	The number of /24s to offset the private subnets in the VPC CIDR.	0	No
component	The component this network will contain.	-	Yes
deployment_identifier	An identifier for this instantiation.	-	Yes
dependencies	A comma separated list of components depended on my this component.	[]	No
include_route53_zone_association	Whether or not to associate VPC with the private Route 53 zone ("yes" or "no").	"yes"	No
private_zone_id	The ID of the private Route 53 zone`	-	If include_route53_zone_association is "yes"
include_nat_gateways	Whether or not to deploy NAT gateways for outbound Internet connectivity ("yes" or "no").	"yes"	No

Outputs

Name	Description
vpc_id	The ID of the created VPC.
vpc_cidr	The CIDR of the created VPC.
availability_zones	The availability zones in which subnets were created.
number_of_availability_zones	The number of populated availability zones available.
public_subnet_ids	The IDs of the public subnets.
public_subnet_cidrs	The CIDRs of the public subnets.
public_route_table_ids	The IDs of the public route tables.
private_subnet_ids	The IDs of the private subnets.
private_subnet_cidrs	The CIDRs of the private subnets.
private_route_table_ids	The IDs of the private route tables.
nat_public_ips	The EIPs attached to the NAT gateways.
internet_gateway_id	The ID of the created IGW.

Compatibility

This module is compatible with Terraform versions greater than or equal to Terraform 1.0 and Terraform AWS provider versions greater than or equal to 3.27.

Required Permissions

• ec2:DescribeVpcs
• ec2:DescribeAddresses
• ec2:DescribeVpcAttribute
• ec2:DescribeVpcClassicLink
• ec2:DescribeVpcClassicLinkDnsSupport
• ec2:DescribeRouteTables
• ec2:DescribeSecurityGroups
• ec2:DescribeNetworkAcls
• ec2:DescribeSubnets
• ec2:DescribeInternetGateways
• ec2:DescribeNatGateways
• ec2:ModifyVpcAttribute
• ec2:AllocateAddress
• ec2:ReleaseAddress
• ec2:AssociateRouteTable
• ec2:DisassociateRouteTable
• ec2:AttachInternetGateway
• ec2:DetachInternetGateway
• ec2:DeleteInternetGateway
• ec2:CreateRoute
• ec2:CreateNatGateway
• ec2:CreateVpc
• ec2:CreateTags
• ec2:CreateSubnet
• ec2:CreateRouteTable
• ec2:CreateInternetGateway
• ec2:DeleteRoute
• ec2:DeleteRouteTable
• ec2:DeleteSubnet
• ec2:DeleteNatGateway
• ec2:DeleteVpc
• s3:ListBucket
• s3:GetObject
• s3:GetObjectTagging
• s3:DeleteObject
• route53:AssociateVPCWithHostedZone
• route53:DisassociateVPCFromHostedZone
• route53:GetChange
• route53:GetHostedZone

Development

Machine Requirements

In order for the build to run correctly, a few tools will need to be installed on your development machine:

• Ruby (3.1)
• Bundler
• git
• git-crypt
• gnupg
• direnv
• aws-vault

Mac OS X Setup

Installing the required tools is best managed by homebrew.

To install homebrew:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Then, to install the required tools:

# ruby
brew install rbenv
brew install ruby-build
echo 'eval "$(rbenv init - bash)"' >> ~/.bash_profile
echo 'eval "$(rbenv init - zsh)"' >> ~/.zshrc
eval "$(rbenv init -)"
rbenv install 3.1.1
rbenv rehash
rbenv local 3.1.1
gem install bundler

# git, git-crypt, gnupg
brew install git
brew install git-crypt
brew install gnupg

# aws-vault
brew cask install

# direnv
brew install direnv
echo "$(direnv hook bash)" >> ~/.bash_profile
echo "$(direnv hook zsh)" >> ~/.zshrc
eval "$(direnv hook $SHELL)"

direnv allow <repository-directory>

Running the build

Running the build requires an AWS account and AWS credentials. You are free to configure credentials however you like as long as an access key ID and secret access key are available. These instructions utilise aws-vault which makes credential management easy and secure.

To run the full build, including unit and integration tests, execute:

aws-vault exec <profile> -- ./go

To run the unit tests, execute:

aws-vault exec <profile> -- ./go test:unit

To run the integration tests, execute:

aws-vault exec <profile> -- ./go test:integration

To provision the module prerequisites:

aws-vault exec <profile> -- ./go deployment:prerequisites:provision[<deployment_identifier>]

To provision the module contents:

aws-vault exec <profile> -- ./go deployment:root:provision[<deployment_identifier>]

To destroy the module contents:

aws-vault exec <profile> -- ./go deployment:root:destroy[<deployment_identifier>]

To destroy the module prerequisites:

aws-vault exec <profile> -- ./go deployment:prerequisites:destroy[<deployment_identifier>]

Configuration parameters can be overridden via environment variables. For example, to run the unit tests with a seed of "testing", execute:

SEED=testing aws-vault exec <profile> -- ./go test:unit

When a seed is provided via an environment variable, infrastructure will not be destroyed at the end of test execution. This can be useful during development to avoid lengthy provision and destroy cycles.

To subsequently destroy unit test infrastructure for a given seed:

FORCE_DESTROY=yes SEED=testing aws-vault exec <profile> -- ./go test:unit

Common Tasks

Generating an SSH key pair

To generate an SSH key pair:

ssh-keygen -m PEM -t rsa -b 4096 -C integration-test@example.com -N '' -f config/secrets/keys/bastion/ssh

Generating a self-signed certificate

To generate a self signed certificate:

openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365

To decrypt the resulting key:

openssl rsa -in key.pem -out ssl.key

Managing CircleCI keys

To encrypt a GPG key for use by CircleCI:

openssl aes-256-cbc \
  -e \
  -md sha1 \
  -in ./config/secrets/ci/gpg.private \
  -out ./.circleci/gpg.private.enc \
  -k "<passphrase>"

To check decryption is working correctly:

openssl aes-256-cbc \
  -d \
  -md sha1 \
  -in ./.circleci/gpg.private.enc \
  -k "<passphrase>"

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/infrablocks/terraform-aws-base-networking. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The library is available as open source under the terms of the MIT License.