How Do I Build an AWS S3 Bucket Policy?

Introduction

Amazon S3 bucket policies are crucial for managing access to your S3 resources. A bucket policy is a resource-based policy that allows you to specify who has access to your S3 bucket and what actions they can perform. This allows for fine-grained control over your data, ensuring security and compliance with your organizational policies.

Step-by-Step Guide to Create an S3 Bucket Policy

To create an AWS S3 Bucket Policy, you need to first define the S3 bucket and then associate a bucket policy with it. This policy will specify what actions are allowed or denied for that bucket. Below is an example demonstrating how to create an S3 bucket along with a bucket policy that grants public read access to the objects within the bucket.

import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

// Create an S3 bucket
const example = new aws.s3.BucketV2("example", {bucket: "example-bucket"});
// S3 bucket policy allowing public read access
const exampleBucketPolicy = new aws.s3.BucketPolicy("example", {
    bucket: example.id,
    policy: pulumi.jsonStringify({
        Version: "2012-10-17",
        Statement: [{
            Effect: "Allow",
            Principal: "*",
            Action: "s3:GetObject",
            Resource: [pulumi.interpolate`${example.arn}/*`],
        }],
    }),
});
export const bucketName = example.bucket;
export const bucketPolicyId = exampleBucketPolicy.id;

Explanation

1. Create the S3 Bucket: An S3 bucket named example-bucket is created using the aws.s3.BucketV2 resource.
2. Define the Bucket Policy: A bucket policy is created using the aws.s3.BucketPolicy resource. This policy allows public read access (s3:GetObject) to all objects within the bucket.
3. Export Values: Two output values, bucketName and bucketPolicyId, are exported for further use.

Key Points

• Resource-Based Policy: S3 bucket policies are resource-based, allowing you to define permissions directly on the bucket.
• Public Read Access: The example policy grants public read access, which is useful for hosting publicly accessible content.
• JSON Policy Format: The policy is defined in JSON format, which is standard for AWS policies.

Conclusion

Creating an S3 bucket policy involves defining the bucket and specifying access permissions through a policy. This example demonstrates how to allow public read access to your bucket’s contents, but policies can be tailored to meet various security and access requirements. Understanding and implementing bucket policies is essential for managing access to your S3 resources effectively.