Which solution meets these requirements?
Set up S3 bucket policies to allow access from a VPC endpoint.
Set up an IAM policy to grant read-write access to the S3 bucket.
Set up a NAT gateway to access resources outside the private subnet.
Set up an access key ID and a secret access key to access the S3 bucket.
Explanations:
Setting up an S3 bucket policy to allow access from a VPC endpoint creates a secure and private connection between the EC2 instances and the S3 bucket, ensuring that data does not traverse the public internet. This is the best practice for accessing S3 from within a VPC.
While setting up an IAM policy to grant read-write access is necessary for permissions, it does not provide a secure private connection. The data can still be exposed to the public internet unless a VPC endpoint is used.
A NAT gateway is used for instances in a private subnet to access the internet or AWS services outside of the VPC. It does not establish a private connection to S3, which is a requirement for processing classified data securely.
Using an access key ID and a secret access key allows programmatic access to S3 but does not ensure a private connection. This method is less secure as it could expose credentials and does not address the need for a private connection.
I have a feeling that the answer is:
Set up S3 bucket policies to allow access from a VPC endpoint.