SCPs and Permission Boundaries

Service Control Policies (SCPs)

Service Control Policies are a feature offered by AWS Organizations, which allows account administrators to manage permissions for all accounts within their organization or specific Organizational Units (OUs). SCPs do not grant permissions; rather, they act as guardrails or limitations on the actions that account entities can perform, overriding any other permission granted at the user or role level.

Key Uses:

• Limiting available AWS services or actions across all accounts in an organization.
• Enforcing compliance and governance by ensuring that certain actions cannot be performed, regardless of user or role permissions.

Permission Boundaries

Permission Boundaries are used within AWS Identity and Access Management (IAM) to set the maximum permissions that an IAM user or role can have. Unlike SCPs, permission boundaries are set directly on individual IAM entities and define the outermost limits of what actions they are allowed to perform, irrespective of their assigned IAM policies.

Key Uses:

• Restricting the maximum permissions for individual IAM roles or users to ensure they operate within a secure and predefined scope.
• Managing permissions granularly at a user or role level within a single AWS account.

Comparison of SCPs and Permission Boundaries

Here’s a closer look at how these two features compare:

Feature	Service Control Policies (SCPs)	Permission Boundaries
Scope	Apply to all accounts within an AWS Organization.	Apply to individual IAM users and roles.
Function	Act as a whitelist or blacklist for permissions.	Define the maximum permissions for IAM entities.
Permission Granting	Do not grant permissions, only restrict them.	Do not grant permissions, only restrict them.
Use Case	Ideal for managing broad policies across multiple accounts.	Useful for fine-grained control within a single account.
Management Level	Managed at the organization or OU level.	Managed directly on individual IAM entities.

Conclusion

Both SCPs and Permission Boundaries are powerful tools for managing permissions in AWS, but they serve different purposes. SCPs are best utilized for setting broad, organization-wide policies that help in maintaining compliance and governance standards across all accounts. On the other hand, permission boundaries are more suited for detailed access control within a single account, particularly useful in environments where users or roles need to be tightly controlled to perform only specific actions.

Understanding when and how to use each feature can significantly enhance your security posture in AWS, ensuring that permissions are appropriately managed and risks are minimized.