Which solution will solve this problem?
Update the EC2 instance role policy to include s3:PutObject access to the target S3 bucket.
Update the EC2 security group to allow outbound traffic to 0.0.0.0/0 for port 80.
Update the EC2 subnet route table to include the S3 prefix list destination routes to the S3 gateway endpoint.
Update the S3 bucket policy to allow s3:PutObject access from the private subnet CIDR block.
Explanations:
While updating the EC2 instance role policy to includes3:PutObjectaccess may be necessary for the instance to upload files, it does not address the fundamental issue of connectivity to the S3 bucket through the gateway endpoint in a private subnet. The instance needs to be able to route requests to the S3 service through the gateway endpoint.
Updating the EC2 security group to allow outbound traffic to0.0.0.0/0for port 80 would not solve the problem, as the instance does not require internet access to communicate with S3 when using a gateway endpoint. Instead, it needs to use the VPC’s routing capabilities to access the S3 gateway endpoint.
Updating the EC2 subnet route table to include the S3 prefix list destination routes to the S3 gateway endpoint is the correct solution. This ensures that traffic to S3 is properly routed through the gateway endpoint, allowing the EC2 instance in the private subnet to communicate with the S3 bucket without needing internet access.
Updating the S3 bucket policy to allows3:PutObjectaccess from the private subnet CIDR block does not resolve the connectivity issue. While this might allow access if the instance could reach the S3 bucket, the problem lies in the routing, not in the permissions. The instance still needs the proper routing to send requests to the S3 gateway endpoint.
It appears that the answer is:
Update the EC2 subnet route table to include the S3 prefix list destination routes to the S3 gateway endpoint.