Different IAM policies (for example, managed policies, inline policies, identity-based policies, resource-based policies, session control policies)

Can you explain the difference between managed policies and inline policies in AWS IAM?

Managed policies are standalone IAM policies that you can attach to multiple users, groups, or roles within your AWS account. They are maintained by AWS (AWS Managed Policies) or by an account administrator (Customer Managed Policies). Inline policies, on the other hand, are policies that are embedded directly into a single user, group, or role. They cannot be shared and are strictly used to apply permissions to that specific entity. Managed policies are recommended for reusability and easier management, whereas inline policies are used for strict one-to-one relationships between policy and principal.

What is the primary benefit of using identity-based policies in AWS IAM?

The primary benefit of using identity-based policies is the ability to directly attach permissions to an IAM user, group, or role. These policies control what actions the identity can perform, on which resources, and under what conditions. Identity-based policies offer fine-grained access control and are used to enforce permissions at the user or role level in AWS.

What are resource-based policies in AWS, and how do they differ from identity-based policies?

Resource-based policies are attached to AWS resources themselves, not to IAM identities. They specify who has permissions to access that resource and the actions they can perform. Unlike identity-based policies, resource-based policies provide a way to specify access permissions directly on the resource and are used mainly for cross-account access or to set permissions on resources like S3 buckets or KMS keys.

How do session policies affect temporary security credentials in AWS IAM?

Session policies are advanced policies that you pass as parameters when you programmatically create a session for a federated user or when you assume an IAM role. They are used to further restrict the permissions for the session beyond what is granted by the user’s or role’s identity-based policies. Session policies help to provide granular, temporary permissions that are ideal for short-term access requirements.

Can you provide an example of when you would use a managed policy over an inline policy?

A managed policy would be preferable when you have a common set of permissions that need to be applied to multiple users, groups, or roles. For example, if several administrators need similar permissions to manage EC2 instances, you would create a Customer Managed Policy with the required permissions and attach it to each administrator role. This approach ensures consistent permission management and simplifies policy updates.

What is the significance of policy evaluation logic in IAM and how does it impact policy enforcement?

Policy evaluation logic is crucial as it determines the outcome of a permission decision when multiple policies apply. AWS evaluates all policies (identity-based, resource-based, session policies, SCPs) and grants permission only if every policy allows the action. If any policy explicitly denies an action, it supersedes any allow statements and the overall result is a denial, reflecting the “default deny” principle in IAM.

Why might you choose to use resource-based policies rather than identity-based policies for an S3 bucket?

Resource-based policies, specifically S3 bucket policies, are useful when you want to define permissions across multiple accounts or to the public. For example, if you need to grant read access to an S3 bucket for users in a different AWS account, using a bucket policy allows you to specify those permissions directly on the S3 bucket rather than managing cross-account roles or identity-based policies.

In what scenario would you find it necessary to use IAM session control policies?

Session control policies are particularly useful when you want to limit the permissions or conditions of a role session. They come into play, for instance, when providing access to a third-party contractor or using federated user sessions where you need to enforce restrictive permissions tailored to a specific job function or time period, ensuring the principle of least privilege is adhered to.

How can you leverage AWS managed policies to expedite the process of granting common permissions?

AWS managed policies are predefined by AWS and are designed to facilitate common use cases by providing a ready-made set of permissions. Administrators can quickly attach these policies to new users, groups, or roles to grant necessary permissions without manually creating policies, thus saving time and reducing the potential for errors in policy definition.

Describe a scenario where inline policies would be crucial despite the administrative convenience of managed policies.

Inline policies are crucial when you need to ensure that permissions are tightly bound to a specific IAM user, group, or role and when those permissions must not be inadvertently detached or reattached elsewhere. For example, when dealing with highly sensitive resources or actions, you would use an inline policy to control the exact permissions and reduce the risk of them being shared or modified outside of the intended scope.

How do permissions boundaries differ from standard IAM policies, and when would you use them?

Permissions boundaries are an advanced feature in IAM that allows you to create and enforce a maximum permission boundary for an IAM user or role. It effectively defines the maximum permissions that the entity can have, regardless of what permissions are actually assigned to that entity. You would use permissions boundaries when you want to delegate permission management to developers or other administrators but need to ensure they don’t grant excessive permissions beyond the scope of their authority.

Explain what conditions in IAM policies are and provide an example of a useful condition you could apply to a policy.

Conditions in IAM policies allow you to specify the circumstances under which a policy grants or denies permissions. They can include date/time, IP address, MFA authentication, and various AWS-specific keys. For example, you could add a condition to a policy that only allows actions if the request comes from a particular CIDR range (IP address range), or if Multi-Factor Authentication (MFA) is enabled, enhancing the security of your AWS environment.