What is the MOST secure way to grant the Lambda function access to the S3 bucket and the DynamoDB table?
Attach the existing IAM policy to the Lambda function.
Create an IAM role for the Lambda function. Attach the existing IAM policy to the role. Attach the role to the Lambda function.
Create an IAM user with programmatic access. Attach the existing IAM policy to the user. Add the user access key ID and secret access key as environment variables in the Lambda function.
Add the AWS account root user access key ID and secret access key as encrypted environment variables in the Lambda function.
Explanations:
Attaching an IAM policy directly to the Lambda function is not recommended as it does not provide the best security practice for permissions management. It can lead to policies being inadvertently exposed or overly permissive.
Creating an IAM role for the Lambda function and attaching the existing IAM policy to that role is the most secure approach. This follows the principle of least privilege, allowing the Lambda function to assume the role and access only the necessary resources. It also helps in better management and auditing of permissions.
Creating an IAM user and using access keys in the Lambda function is not secure. Hardcoding access keys as environment variables exposes them to potential compromise. It is also not scalable and goes against best practices of using roles for AWS services.
Using the AWS account root user’s access keys is highly discouraged as it poses significant security risks. Root access should be limited, and using its credentials within the Lambda function can lead to over-permission and increased vulnerability.
If I’m correct, the answer is:
Create an IAM role for the Lambda function. Attach the existing IAM policy to the role. Attach the role to the Lambda function.