Managing IAM policies
IAM policies play a pivotal role in defining permissions within AWS. They dictate who can do what and where. As AWS environments grow in complexity, the need for fine-grained control and understanding of IAM policies becomes paramount. Misconfigured policies can introduce significant security risks, emphasizing the importance of getting them right. In this section, we will delve deep into the intricacies of IAM policies, their types, how they are evaluated, and best practices for creating and managing them.
Understanding IAM policies
Understanding the nuances of IAM policies becomes indispensable. This subsection explores the different types of policies and delves into how AWS IAM evaluates them.
Identity-based versus resource-based policies
IAM policies can be broadly classified into two categories – identity-based and resource-based:
- Identity-based policies are attached directly to an identity, such as an IAM user, group, or role. These policies define the permissions for the identity, specifying what actions they can perform, on which resources, and under what conditions. For example, an identity-based policy might grant an IAM user permission to launch specific EC2 instances or read objects from a designated S3 bucket.
- Resource-based policies, conversely, are attached directly to resources. A classic example of this is an S3 bucket policy or an SQS queue policy. These policies dictate which identities can or cannot perform actions on that particular resource. For instance, a resource-based policy on an S3 bucket might allow an IAM role from a different AWS account to read objects.
Customer-managed versus AWS-managed policies
AWS provides two distinct types of managed policies – customer-managed and AWS-managed:
- Customer-managed policies are those crafted and maintained by AWS users. They offer the flexibility to be tailored to specific organizational needs, allowing for more granular control over permissions. For instance, an organization might have a customer-managed policy that restricts access to a specific S3 bucket, allowing only designated departments or teams to upload or download content.
- AWS-managed policies, on the other hand, are predefined by AWS. They are designed to provide permissions for common use cases, ensuring that users don’t have to start from scratch. For example, AWS offers a managed policy named AWSLambda_ReadOnlyAccess that grants read-only access to AWS Lambda functions. It is important to bear in mind that AWS-managed policies can be automatically updated by AWS to reflect new services or features. While this ensures policies are up-to-date, administrators need to stay informed about these changes to avoid unexpected permission alterations.