AWS IAM Identity Policy - "Resource" discussion

https://chatgpt.com/share/a15d63d2-a124-4e5d-8195-830e27fb395d

Whether targeting a role or specific AWS resources is more common or advised depends on the context and the desired security model. Both approaches serve different purposes in AWS Identity and Access Management (IAM), and each has its own use cases:

1. Targeting an IAM Role (More common for users/roles):

• Use Case: When you want to define a set of permissions for who can perform actions.

• Common: This is a common practice for controlling permissions at a higher level. You assign policies to roles, and these roles are then assumed by users or services.

• Advised: This approach is recommended when managing multiple users or services because you can easily modify or revoke permissions in one place (the role) without touching individual resources.

• Example:

  
  "Resource": "arn:aws:iam::123456789012:role/MyRole"
  

Advantages:

• Easier Management: You can centrally manage access by assigning or removing permissions from the role without having to modify each resource.

• Scalability: If multiple users or services need the same set of permissions, it's easier to manage by assigning roles rather than specific resource-level permissions.

When to Use:

• For multi-user or multi-service environments where permissions are broadly defined.

• For complex environments where you want to delegate access to external entities (cross-account access, etc.).

• When you need to limit actions based on who or what is trying to perform the action.

2. Targeting Specific AWS Resources (More common for resources):

• Use Case: When you want to limit what resources can be accessed or acted upon.

• Common: Resource-based policies are used when you need fine-grained control over specific AWS resources. This ensures that only designated users, roles, or services can access or modify those resources.

• Advised: Targeting specific resources is more advisable for high-security environments, or where sensitive data and actions need strict control.

• Example:

  
  "Resource": "arn:aws:s3:::my-bucket/my-object.txt"
  

Advantages:

• Granular Control: You can enforce permissions on specific resources, ensuring tighter security.

• Increased Security: You can prevent access to anything outside the explicitly defined resource, reducing the attack surface.

When to Use:

• When you need to apply specific permissions to individual resources, like a particular S3 bucket, EC2 instance, or Lambda function.

• When fine-grained permissions are necessary to ensure only specific actions are allowed on specific resources.

• In cases where resources belong to sensitive environments or need to be tightly controlled.

Which is More Common?

• IAM roles are generally more common in large-scale deployments and multi-service environments because they offer flexibility and ease of management.

• Resource-based targeting is frequently used for controlling access to specific, high-security or sensitive resources.

Which is More Advised?

• Targeting Roles is recommended when you want to manage permissions for who can perform actions (identity-based access control).

• Targeting Specific Resources is more advisable when securing specific resources in high-security contexts (resource-based access control).

Best Practice:

In many cases, it's beneficial to combine both:

• Use roles to manage who can access resources.

• Use resource-level permissions to restrict what those roles (or identities) can do on specific resources.

For example, an S3 bucket might have a policy that allows only a specific IAM role to perform actions, and that role has a policy that allows specific users to assume it.