Which additional steps should the solutions architect take to meet these requirements?
Assign an endpoint policy to the endpoint that restricts access to a specific S3 bucket. Attach a bucket policy to the S3 bucket that grants access to the VPC endpoint. Add the gateway prefix list to a NACL of the instances to limit access to the application EC2 instances only.
Attach a bucket policy to the S3 bucket that grants access to application EC2 instances only using the aws:SourceIp condition. Update the VPC route table so only the application EC2 instances can access the VPC endpoint.
Assign an endpoint policy to the VPC endpoint that restricts access to a specific S3 bucket. Attach a bucket policy to the S3 bucket that grants access to the VPC endpoint. Assign an IAM role to the application EC2 instances and only allow access to this role in the S3 bucket’s policy.
Assign an endpoint policy to the VPC endpoint that restricts access to S3 in the current Region. Attach a bucket policy to the S3 bucket that grants access to the VPC private subnets only. Add the gateway prefix list to a NACL to limit access to the application EC2 instances only.
Explanations:
While assigning an endpoint policy and attaching a bucket policy is necessary, adding a gateway prefix list to a Network ACL (NACL) is not sufficient to limit access exclusively to application EC2 instances. NACLs operate at the subnet level and do not directly control IAM permissions or restrict S3 access effectively.
This option incorrectly uses theaws:SourceIpcondition to restrict access to the S3 bucket based on the IP address of EC2 instances. Since the instances access S3 through a VPC endpoint, their public IPs are not relevant, and a route table update does not effectively restrict access.
This option correctly implements the necessary restrictions by assigning an endpoint policy that limits access to a specific S3 bucket and attaching a bucket policy that allows access only through the VPC endpoint. The use of an IAM role for EC2 instances further tightens security by ensuring that only instances with the correct role can access the S3 bucket.
Although it mentions assigning an endpoint policy and a bucket policy, restricting access to private subnets in a bucket policy is not appropriate since S3 bucket policies do not recognize subnets directly. Instead, policies should focus on IAM roles and VPC endpoint restrictions. Additionally, using a NACL to limit access is not effective for controlling S3 permissions.
I would say the answer is:
Assign an endpoint policy to the VPC endpoint that restricts access to a specific S3 bucket. Attach a bucket policy to the S3 bucket that grants access to the VPC endpoint. Assign an IAM role to the application EC2 instances and only allow access to this role in the S3 bucket’s policy.