Terraform AWS Bastion

A Terraform module for deploying a supervised bastion into a base network in AWS.

The bastion requires:

An existing base network
One or more existing load balancers

The bastion consists of:

An autoscaling group and launch configuration for bastion instances configured with the supplied SSH key updating the supplied load balancers.
A security group allowing access to the bastion from the load balancers.
A security group open to the bastion for use on protected instances.

Usage

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

module "bastion" {
  source  = "infrablocks/bastion/aws"
  version = "0.1.2"
  
  region = "eu-west-2"
  vpc_id = "vpc-fb7dc365"
  subnet_ids = "subnet-ae4533c4,subnet-443e6b12"
  
  component = "important-component"
  deployment_identifier = "production"
  
  ami = "ami-bb373ddf"
  instance_type = "t2.micro"
  
  ssh_public_key_path = "~/.ssh/id_rsa.pub"
  
  allowed_cidrs = "100.10.10.0/24,200.20.0.0/16"
  egress_cidrs = "10.0.0.0/16"
  
  load_balancer_names = ["lb-12345678"]
  
  minimum_instances = 1
  maximum_instances = 3
  desired_instances = 2
}

As mentioned above, the bastion deploys into an existing base network. Whilst the base network can be created using any mechanism you like, the AWS Base Networking module will create everything you need. See the docs for usage instructions.

Similarly, the bastion is reachable through one or more load balancers. Whilst the load balancers can be created using any mechanism you like, the AWS Classic Load Balancer module will create everything you need. See the docs for usage instructions.

Inputs

Name	Description	Default	Required
region	The region into which to deploy the bastion	-	yes
vpc_id	The ID of the VPC the bastion should be deployed into	-	yes
subnet_ids	The IDs of the subnets the bastion should deploy into	-	yes
component	The name of this component	-	yes
deployment_identifier	An identifier for this instantiation	-	yes
ami	The ID of the AMI for the bastion instances	-	yes
instance_type	The instance type of the bastion instances	t2.nano	yes
ssh_public_key_path	The absolute path of the SSH public key to use for bastion access	-	yes
allowed_cidrs	The CIDRs that are allowed to access the bastion	-	yes
egress_cidrs	The CIDRs that are reachable from the bastion	-	yes
load_balancer_names	The names of the load balancers to update on autoscaling events	-	yes
minimum_instances	The minimum number of bastion instances	-	yes
maximum_instances	The maximum number of bastion instances	-	yes
desired_instances	The desired number of bastion instances	yes	yes

Outputs

Name	Description
launch_configuration_name	The name of the launch configuration for bastion instances
bastion_security_group_id	The ID of the bastion's security group
open_to_bastion_security_group_id	The ID of the security group allowing access from the bastion

Development

Machine Requirements

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

Ruby (2.3.1)
Bundler
git
git-crypt
gnupg
direnv

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 2.3.1
rbenv rehash
rbenv local 2.3.1
gem install bundler

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

# 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

To provision module infrastructure, run tests and then destroy that infrastructure, execute:

./go

To provision the module prerequisites:

./go deployment:prerequisites:provision[<deployment_identifier>]

To provision the module contents:

./go deployment:harness:provision[<deployment_identifier>]

To destroy the module contents:

./go deployment:harness:destroy[<deployment_identifier>]

To destroy the module prerequisites:

./go deployment:prerequisites:destroy[<deployment_identifier>]

Common Tasks

To generate an SSH key pair:

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

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/tobyclemson/terraform-aws-bastion. 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.

ckaushik/terraform-aws-bastion