Show how to create an AWS S3 bucket public access block with Terraform.

Alright, let's begin! The program I'll be providing today will help you set up a public access block for an Amazon Simple Storage Service (S3) bucket using Terraform.

The Amazon S3 public access block aims to provide a layer of protection to all of your Amazon S3 resources to ensure that they aren't accidentally made public. Public access blocks override bucket policies and access control lists (ACLs) that allow public access, providing an additional safety net against inadvertent public disclosures.

With the concept now clear, let's get to the programming part!

Below is the step-by-step code explaining how to create an AWS S3 bucket public access block with Terraform, and also a new S3 bucket.

provider "aws" {
  region = "us-west-2"
}

resource "aws_s3_bucket" "bucket" {
  bucket = "my-bucket"
  acl    = "private"
}

resource "aws_s3_bucket_public_access_block" "access_block" {
  bucket = aws_s3_bucket.bucket.id

  block_public_acls   = true
  block_public_policy = true
  ignore_public_acls  = true
  restrict_public_buckets = true
}

Let's break down what this code does.

First, the provider block sets up the AWS provider for Terraform. The region parameter is where we specify our resources will live. In this case, we are choosing the us-west-2 region.

Then, a new S3 bucket is created by the aws_s3_bucket resource. bucket is the name of the bucket and acl is the access control list policy, which is set to private in this case.

Next, we create a public access block for the bucket by using the aws_s3_bucket_public_access_block resource block. The bucket parameter specifies the S3 bucket to associate this public access block with, referring to the id of the bucket resource we created.

The following boolean flags in aws_s3_bucket_public_access_block enforce different aspects of public access restrictions:

• block_public_acls: Blocks new public ACLs and uploading public objects.
• block_public_policy: Blocks new public bucket policies.
• ignore_public_acls: Ignore all public ACLs on a bucket and any objects that it contains.
• restrict_public_buckets: Restrict public bucket policies for this bucket.

All the flags are set to true which means we are strictly prohibiting any form of public access to this bucket.

Remember to replace "my-bucket" with your desired bucket name and you're ready to go! This should get you an S3 bucket with the public access block configuration!