Which solution will meet these requirements in the MOST secure manner?
Apply an S3 bucket policy that grants read access to the S3 bucket.
Apply an IAM role to the Lambda function. Apply an IAM policy to the role to grant read access to the S3 bucket.
Embed an access key and a secret key in the Lambda function’s code to grant the required IAM permissions for read access to the S3 bucket.
Apply an IAM role to the Lambda function. Apply an IAM policy to the role to grant read access to all S3 buckets in the account.
Explanations:
While an S3 bucket policy can grant read access to the bucket, it does not provide the granularity of permissions management offered by IAM roles and policies. It could also lead to overly permissive access if not carefully defined.
Applying an IAM role to the Lambda function with an IAM policy that grants read access to the specific S3 bucket ensures that permissions are managed securely. This approach adheres to the principle of least privilege and avoids hardcoding sensitive credentials.
Embedding an access key and secret key in the Lambda function’s code poses a significant security risk, as these credentials can be exposed or compromised. This practice is not recommended and violates security best practices.
While applying an IAM role with an IAM policy can provide access, granting read access to all S3 buckets in the account is not a secure approach. This violates the principle of least privilege by providing broader access than necessary for the function’s operation.
In my experience, the answer is:
Apply an IAM role to the Lambda function. Apply an IAM policy to the role to grant read access to the S3 bucket.