Which solution will meet these requirements?

Explanations:

Creating a gateway VPC endpoint for S3 allows private connectivity from a VPC to S3 without using the public internet, but it does not grant CloudFormation access to a template stored in a private S3 bucket. CloudFormation would still need permissions to access the S3 bucket directly, which is not achieved simply by configuring the stack to use the S3 object URL.

Using an Amazon API Gateway to access the S3 bucket adds unnecessary complexity and does not follow best practices for accessing CloudFormation templates. The API Gateway does not inherently grant the necessary permissions for CloudFormation to access the S3 object, nor does it solve the public access issue.

A presigned URL allows temporary, secure access to an S3 object without changing the bucket’s permissions. By generating a presigned URL for the CloudFormation template, the company can grant access specifically for the duration needed, maintaining the security of the bucket by keeping it private and not allowing public access. This solution aligns with security best practices.

Allowing public access to the S3 object contradicts security best practices, as it exposes the template to anyone on the internet. Although the public access could be revoked later, this approach increases the risk of unauthorized access to the CloudFormation template during the test environment creation process.