What is the MOST secure solution that will meet these requirements?
Update the IAM policy that is attached to the EC2 instance’s IAM role to allow the dynamodb:Query permission on the DynamoDB table in Account B. Add a policy in Account A to allow the DynamoDB service principal to use the PassRole action to pass the role to Account B.
In Account B, create an IAM role that has permission to query the DynamoDB table. Add the EC2 instance’s IAM role to the trust policy on the newly created IAM role in Account Update the IAM policy that is attached to the EC2 instance’s IAM role to allow the sts:AssumeRole permission on the newly created IAM role in Account B.
Update the IAM policy that is attached to the EC2 instance’s IAM role to allow the dynamodb:Query permission on the DynamoDB table in Account B. Update the DynamoDB table’s resource policy to allow the query action from the EC2 instance’s IAM role.
In Account B, create a static IAM key that has the appropriate permissions to query the DynamoDB table. Embed these credentials into the credentials file on the EC2 instance. Reference the credentials every time the application needs to query the table.
Explanations:
This option suggests using thePassRoleaction, which is unnecessary and not relevant for providing cross-account access to DynamoDB. Additionally, it does not properly address cross-account IAM permissions for DynamoDB.
This option is the most secure. It uses IAM roles and assumes role functionality, ensuring the EC2 instance in Account A can securely assume a role in Account B that grants access to DynamoDB. This adheres to AWS best practices for cross-account access.
Although it provides direct access via IAM policies, using DynamoDB resource policies for cross-account access is not the recommended approach in this scenario. It is less secure than assuming a role, and the EC2 instance would still need permission to query DynamoDB in Account B.
This is a poor solution as it requires embedding static credentials into the EC2 instance, which is insecure and violates best practices. It exposes the credentials to potential leakage and is less manageable compared to role-based access.
I sort that the answer is:
In Account B, create an IAM role that has permission to query the DynamoDB table. Add the EC2 instance’s IAM role to the trust policy on the newly created IAM role in Account Update the IAM policy that is attached to the EC2 instance’s IAM role to allow the sts:AssumeRole permission on the newly created IAM role in Account B.