Which solution will meet these requirements?
Grant full S3 bucket access to all Lambda functions through a shared IAM role.
Configure the Lambda functions to run within a VPC. Configure a bucket policy to grant access based on the Lambda functions’ VPC endpoint IP addresses.
Create individual IAM roles for each Lambda function. Grant the IAM roles access to the S3 bucket. Assign each IAM role as the Lambda execution role for its corresponding Lambda function.
Configure a bucket policy granting access to the Lambda functions based on their function ARNs.
Explanations:
Granting full S3 bucket access to all Lambda functions through a shared IAM role violates the principle of least privilege. This approach allows all Lambda functions to access the S3 bucket, regardless of whether they need that access, which can lead to security risks.
While configuring Lambda functions to run within a VPC and using a bucket policy based on VPC endpoint IP addresses may provide some level of control, it does not enforce access at the Lambda function level. Additionally, IP addresses can change, making this method less secure and reliable.
Creating individual IAM roles for each Lambda function and granting only the necessary access to the S3 bucket for each role ensures that each function has the least privilege needed for its operation. This aligns with security best practices.
Configuring a bucket policy to grant access to the Lambda functions based on their function ARNs could work; however, it may not be as secure as assigning individual IAM roles. If multiple functions share a role, it could lead to over-permissioning and violate the principle of least privilege.
I chart that the answer is:
Create individual IAM roles for each Lambda function. Grant the IAM roles access to the S3 bucket. Assign each IAM role as the Lambda execution role for its corresponding Lambda function.