The purpose here is to write code in terraform that will provision an infrastructure as shown in the diagram below. It is made up of:

• A VPC that has one private and one public subnet
  • Only the public instance has access to internet. This instance acts as a jump box to the private instance
  • The private instance does not have access to internet. This instance connects to S3 via a VPC Endpoint
• VPC Endpoint provides private access to S3. Traffic between private instance and S3:
  • does not go through open internet
  • does not leave Amazon network

VPC Endpoint for S3 is a helpful feature that privately connects your VPC to S3. A private connection from your VPC to your AWS services is a much more secure way compared to giving internet access to your instances or using a NAT device.

VPC Endpoint for Amazon S3 blog explains how to create an Endpoint via AWS Management Console

• Terraform v0.12.3 (Code has been tested with this version)
• Create an RSA key (i.e. ~/.ssh/id_rsa) for granting access to servers that we will be provisioning in this repo. Use a third-party tool such as ssh-keygen for this purpose
• Ensure that AWS credentials are available at: "~/.aws/credentials" in the following format:

      [default]
      aws_access_key_id = <KEY>
      aws_secret_access_key = <SECRET_KEY>
      region = <REGION>

• Ensure that a unique S3 bucket as a backend type is created for saving terraform state file. See the docs here
• Edit values in main.tf as your need liike backend bucket name and region

      terraform {
        # It is expected that the bucket, globally unique, already exists
        backend "s3" {
          # you will need a globally unique bucket name
          bucket  = "<BUCKET_NAME>"
          key     = "<KEY>.tfstate"
          region  = "<REGION>"
          encrypt = true
        }
      }

• git clone https://github.com/shazChaudhry/terraform-aws-privateLink.git
• cd terraform-aws-privateLink
• eval $(ssh-agent)
• ssh-add -k ~/.ssh/id_rsa (See adding an identity key for granting access to servers)
• ssh-add -l (This command should show what keys have been added to the agent)
• export TF_INPUT=0 (See Environment Variables link on how to set system variables)
• export TF_VAR_producer_public_key=$(ssh-keygen -y -f ~/.ssh/id_rsa) (This will be required unless producer_public_key in variables.tf is already set)
• export TF_VAR_region=eu-west-2 (This value is for london. You may choose your own region instead)
• export TF_VAR_credentials=~/.aws/credentials
• export TF_VAR_producer_s3_bucket_name=privaelink-202907271837 (This must be globally unique bucket name)

• terraform init
• terraform apply -auto-approve

Once the command above has completed successfully, check aws management console in your selected region. Make a note of IPs public and private EC2 instances:

• ssh -A admin@<PRODUCER_PUBLIC_IP> (This is the bastion/jump server. You can not ssh to a server in private subnet. Also, ensure your key-pair key is added to ssh agent)
• ssh -A admin@<PRODUCER_PRIVATE_IP> (This will allow you to ssh to the instance in private subnet that has a route to S3 via privatelink)
• export TF_VAR_region=<REGION_SET_ABOVE>
• aws s3 ls s3://privaelink-202907271837 --region ${TF_VAR_region} (The bucket should be empty. From the producer private instance you should be able to get, put, list and delete s3 objects)
• touch file.txt (create a new blank file that is going to be uploaded to the bucket)
• aws s3 cp file.txt s3://privaelink-202907271837/ --region ${TF_VAR_region} (This command uploads the file created above)
• aws s3 ls s3://privaelink-202907271837 --region ${TF_VAR_region} (This command should list the file that was uploaded previously) See this reference for common commands: https://docs.aws.amazon.com/cli/latest/userguide/cli-services-s3-commands.html

• terraform destroy -force

These resources have helped me learn about AWS PrivateLinks:

• S3 encryption with KMS Managed Keys
• Import your Custom Key into KMS; Encrypt data with custom key
• AWS Key Management Service. Customer Master Key, Data Key, Envelope Encryption; KnowledgeIndia AWS Tutorials
• Overview of Managing Access
• Gateway VPC Endpoints; includes a good diagram
• Endpoints for Amazon S3
• IAM Policies and Bucket Policies and ACLs blog