Hashicorp Terraform

Get up and running with Terraform

What is Terraform?

• Terraform is an open-source, declarative Infrastructure as Code language from HashiCorp.

• Providers are used to define the resources to build. These abstract the underlying API calls made to build, modify, and destroy resources by wrapping this into HCL syntax. In other words, you just worry about writing Terraform code without having to understand and work with the underlying APIs.

Installation

# Installing via Homebrew on MacOS
brew tap hashicorp/tap
brew install hashicorp/tap/terraform
brew update
brew upgrade hashicorp/tap/terraformh

# Enabling tab completion
terraform -install-autocomplete

# Restarting shell
. ~/.zshrc    # bash is ~/.bashrc

Commands

• Initialize the directory where Terraform files are stored: terraform init

• Verify the Terraform syntax is correct: terraform validate

• View the resources the code would build if run: terraform plan

• Build the resources: terraform apply

• Destroy the resources created with Terraform: terraform destroy

Example

• Typically, Terraform code is defined in a main.tf file and variables found in that file can be declared in variables.tf

• Variables are not required and you could hard code everything into main.tf if desired.

• Here's an example of configuring an AWS S3 bucket in Terraform utilizing the AWS Provider.

main.tf

# Create the bucket
resource "aws_s3_bucket" "s3-bucket-1" {
  bucket = var.mybucketname
}

# Enable server-side encryption
resource "aws_s3_bucket_server_side_encryption_configuration" "s3-encryption-config" {
  bucket = aws_s3_bucket.s3-bucket-1.bucket # defines bucket name

  rule {
    apply_server_side_encryption_by_default {
      sse_algorithm = var.sse-algorithm # defines encryption type
    }
  }

  depends_on = [
    aws_s3_bucket.s3-bucket-1 # ensures bucket is created before trying to apply encryption
  ]
}

# Configure bucket policy, set to deny HTTP requests
resource "aws_s3_bucket_policy" "s3-bucket-policy" {
  bucket = aws_s3_bucket.s3-bucket-1.id

  # defines bucket policy below, SecureTransport false means it blocks HTTP access
  policy = <<POLICY
  {
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Deny",
            "Principal": "*",
            "Action": "s3:*",
            "Resource": "arn:aws:s3:::${var.mybucketname}/*",
            "Condition": {
                "Bool": {
                    "aws:SecureTransport": "false"
                }
            }
        }
    ]
}
POLICY
}

# Block public access to the bucket
resource "aws_s3_bucket_public_access_block" "s3-bucket-access-control" {
  bucket = aws_s3_bucket.s3-bucket-1.id

  block_public_acls       = var.s3-bucket-ac["block_public_acls"]
  block_public_policy     = var.s3-bucket-ac["block_public_policy"]
  ignore_public_acls      = var.s3-bucket-ac["ignore_public_acls"]
  restrict_public_buckets = var.s3-bucket-ac["restrict_public_buckets"]
}

variables.tf

variable "mybucketname" {
  description = "Set a unique bucket name"
  type        = string
}

variable "sse-algorithm" {
  description = "Specify the encryption type to use"
  type        = string
  default     = "AES256"
}

variable "s3-bucket-ac" {
  description = "Block public access"
  type        = map(any)
  default = {
    block_public_acls       = "true"
    block_public_policy     = "true"
    ignore_public_acls      = "true"
    restrict_public_buckets = "true"
  }
}