2.2.2.4. IAM Solutions for Multi-Account Structures (SCPs, Assuming Roles)

First Principle: Establishing granular control for a strong security posture and operational efficiency at scale ensures robust security boundaries and efficient, delegated access.

Managing multi-account AWS access and permissions is challenging, requiring robust solutions. This aligns with the principles of security and governance.

• Service Control Policies (SCPs): (A powerful AWS Organizations feature.) SCPs set maximum available permissions for all IAM users/roles in an OU or account. They act as guardrails, defining actions accounts cannot perform, regardless of attached IAM policies.
  • Practical Relevance: SCPs prevent unauthorized actions at a foundational level, ensuring compliance and preventing accidental or malicious over-privilege. They are crucial for enforcing enterprise-wide security standards.
• Cross-Account Role Assumption: (Enables a trusted entity (e.g., IAM user/role) to temporarily assume an IAM role in another account.) Granting permissions defined in the assumed role for the session's duration.
  • Practical Relevance: This mechanism facilitates secure, delegated access without sharing long-term credentials. It's vital for centralized security teams to audit resources, enabling cross-account automation, and allowing developers to access specific resources in other accounts with least privilege.

Key IAM Solutions for Multi-Account:

• Service Control Policies (SCPs): Preventative maximum permissions, organizational guardrails.
• Cross-Account Role Assumption: Secure, temporary, delegated access between accounts.

Scenario: A large enterprise needs to allow its central security team to audit resources in various development accounts without giving them persistent credentials in each account. Additionally, they must ensure no developer can accidentally create new IAM users with administrative access in any account.

Reflection Question: How would you implement cross-account role assumption for the security team and Service Control Policies (SCPs) for all member accounts to achieve secure, delegated access and enforce preventative permission boundaries in this multi-account structure?

Together, SCPs and cross-account role assumption provide a comprehensive strategy for enforcing the principle of least privilege and secure access in complex multi-account AWS environments.

💡 Tip: Consider how SCPs define what is allowed at the organizational boundary, while IAM permissions policies define what is allowed within an account.