How should access be granted?
Create an IAM role in the production account and allow EC2 instance in the development account to assume that role using the trust policy. Provide read access for the required S3 bucket to this role.
Use a custom identity broker to allow Developer IAM users to temporarily access the S3 bucket.
Create a temporary IAM user for the application to use in the production account.
Create a temporary IAM user in the production account and provide read access to Amazon S3. Generate the temporary IAM user’s access key and secret key and store these keys on the EC2 instance used by the application in the development account.
Explanations:
Creating an IAM role in the production account allows the EC2 instance in the development account to assume this role, enabling it to access the S3 bucket securely without hardcoding credentials. The trust policy will ensure only the specified EC2 instance can assume the role, following best practices for cross-account access.
A custom identity broker adds unnecessary complexity and does not directly provide the required access. While it can facilitate access to resources, it’s more suited for managing complex access scenarios and does not leverage AWS’s built-in cross-account IAM capabilities effectively.
Creating a temporary IAM user in the production account is not a recommended practice, as it requires managing long-term credentials. This approach poses security risks, especially if credentials are hardcoded or not managed securely. Additionally, IAM roles are the preferred method for cross-account access.
Similar to option C, creating a temporary IAM user and managing its access keys on the EC2 instance introduces security risks and does not follow AWS best practices. Temporary credentials should be obtained through roles rather than static access keys.
I design that the answer is:
Create an IAM role in the production account and allow EC2 instance in the development account to assume that role using the trust policy. Provide read access for the required S3 bucket to this role.