3.4.1.3. Permission Management Delegation by Using IAM Permissions Boundaries

First Principle: Operational autonomy is desirable, but central governance and guardrails must remain intact to prevent unintended privilege escalation and policy violations.

Delegating permission management in AWS without ceding full administrative control is challenging. IAM Permissions Boundaries address this by defining the maximum permissions an identity-based policy can grant to an IAM entity (user or role). Crucially, a permissions boundary does not grant permissions itself; rather, it acts as a filter or an upper limit. Any permissions specified in an identity-based policy are effective only if they are also allowed by the attached permissions boundary.

This mechanism enables secure delegation:

• Controlled Autonomy: Development teams can create and manage IAM users and roles within their scope, but their actions are constrained by the boundary.
• Enforced Guardrails: Prevents the creation of highly privileged identities, ensuring compliance with organizational security policies.
• Centralized Governance: Security teams maintain central control by defining and attaching the boundaries, offloading day-to-day permission management while enforcing a maximum permission set.

Key Aspects of IAM Permissions Boundaries:

• Purpose: Define maximum permissions for an IAM entity.
• Function: Acts as a filter/upper limit, does not grant permissions.
• Benefit: Enables secure delegation, enforces guardrails, centralizes governance.

Scenario: A central security team wants to delegate the creation of IAM roles and policies to development teams within their AWS accounts. However, they need to ensure that no developer can create a role that grants permissions beyond a predefined maximum, preventing accidental privilege escalation.

Reflection Question: How would you use IAM Permissions Boundaries to delegate permission management to development teams while maintaining central governance and preventing unintended privilege escalation, ensuring adherence to the principle of least privilege?

This allows for scalable permission management where teams can innovate within defined security parameters, preventing accidental or malicious over-provisioning of access.

💡 Tip: A permissions boundary sets the maximum permissions for an identity-based policy. It's distinct from a resource-based policy, which is attached directly to a resource (e.g., S3 bucket, SQS queue) and specifies who can access that specific resource.