Inline Policies Vs Managed Policies

Types of IAM Policies

Inline policies and managed policies are two different types of IAM policies in AWS. They differ in how they are created, associated with IAM entities, and their management capabilities.
 

Inline Policies

• Definition: An inline policy is an IAM policy that is embedded within a single IAM identity.
   
• Association: It follows a strict one-to-one relationship, meaning each inline policy has only one IAM entity.
   
• Lifecycle: When you delete the IAM entity to which the inline policy is attached, the policy is deleted.
   
• Creation and Editing: Inline policies are created and managed directly in the context of the IAM entity. It is done using the AWS Management Console, CLI, or SDKs.
   
• Use Cases: Inline policies are helpful when you need to apply a policy that is specific to one IAM entity. It provides a way to tightly couple the policy with the entity. It ensures that permissions are not granted to other entities.

Managed Policies

• Definition: A managed policy is an IAM policy created and maintained singly by IAM entities.
   
• Association: Managed policies can be attached to multiple IAM identities within the same or across different accounts.
   
• Lifecycle: Managed policies exist freely to the IAM entities they are attached to. If you delete an IAM entity, the managed policy remains intact.
   
• Creation and Editing: Managed policies are created and handled separately through the AWS Management Console, CLI, or SDKs. AWS maintains and updates these policies, providing predefined permissions for common use cases.
   
• Use Cases: Managed policies are ideal for the central management of permissions. They allow you to apply consistent permissions across multiple IAM entities. They simplify policy updates as AWS maintains and updates them.
   

Inline Policies

Inline policies are policies that are embedded within a single IAM identity. Unlike managed policies, they are associated with one IAM identity. They are deleted when the identity is removed.
 

Here are the key characteristics of inline policies:

One-to-One Relationship: Each inline policy is linked with only one IAM identity. It follows a strict one-to-one relationship. It means that the policy is directly related to a single entity.

Deleted with the Entity: If you delete the IAM identity to which an inline policy is attached, the policy is deleted. This tight coupling makes inline policies suitable to ensure needed permissions. They are only applicable to a specific identity.

Customization: You create and manage inline policies directly within the IAM entity's form. This gives you the flexibility to tailor permissions precisely to the needs of that specific identity.

Simplified Scope: Since inline policies are scoped to a single entity, they are easier to manage.

Use Cases: Inline policies are useful when you want to enforce strict access control. They are suitable when you need to grant specific permissions to an individual IAM identity. Those permissions are removed when the identity is deleted.
 

It's essential to consider the advantages and disadvantages of using inline policies.

Advantages

Clear Scope: The policy's scope is limited to the entity to which it is attached. It reduces the risk of accidentally granting excessive permissions to other users, groups, or roles.

Self-Contained: All the permissions for an IAM entity are defined in one place, making it easier to manage and audit.

Disadvantages

Less Reusability: Inline policies cannot be shared across multiple IAM identities. It reduces reusability compared to managed policies.

Policy Management: Managing many IAM identities with their inline policies can become cumbersome and challenging.

Best Practices

In general, AWS recommends using managed policies over inline policies when possible. Managed policies are more reusable and easier to maintain. Reserve inline policies for scenarios where you need precise, entity-bound permissions. While inline policies offer granular control over permissions for IAM entities, we prefer managed policies. Inline policies may be helpful in certain use cases, but careful attention is needed. We need to strike a balance between custom permissions and policy manageability.

Managed Policies

Managed policies, in the context of AWS IAM, are pre-built policies provided and maintained by AWS. These policies are designed to cover common use cases for various AWS services. Managed policies make it easier to assign permissions to IAM identities without writing them yourself.
 

Here are some critical points about managed policies:
 

AWS-Provided: Managed policies are created and managed by AWS, so you do not need to define the permissions manually. AWS regularly updates these policies to incorporate new API actions, ensuring you stay up-to-date.

Reusability: Managed policies are highly reusable. You can attach the same managed policy to multiple IAM identities within your AWS account.

ARN: Each managed policy has its own Amazon Resource Name (ARN) that uniquely identifies it. The ARN for a managed policy looks like: arn:aws:iam::aws:policy/PolicyName. For example, "arn:aws:iam::aws:policy/AmazonS3ReadOnlyAccess".

Job Function Policies: AWS provides a set of managed policies tailored to specific job functions. These policies align with commonly used job roles in the IT industry. For example- administrators, developers, or power users. AWS maintains and updates these policies as new services and API operations are introduced.

Permissions Update: Since we create managed policies by AWS, any updates to the permissions are applied to all IAM identities of that policy.

Immutable: You cannot modify the permissions defined in a managed policy. You can create a customer-managed policy if you need to customize permissions to suit your specific requirements.

Policy Access Control: Managed policies define permissions at a coarse level. They grant access to multiple actions for a specific AWS service. While simplifying permission management, they might provide more permissions than needed for particular use cases.

Examples of some commonly used AWS-managed policies include:

• AmazonS3ReadOnlyAccess: Provides read-only access to Amazon S3 buckets and objects.
   
• AmazonEC2FullAccess: Grants full access to Amazon EC2 resources.
   
• AWSLambdaFullAccess: Provides full access to AWS Lambda functions and related resources.
   
• AmazonDynamoDBFullAccess: Grants full access to Amazon DynamoDB tables.
   

When assigning permissions to IAM identities, it's good to use managed policies whenever possible. It is so because they are regularly updated. They help ensure that your AWS environment remains secure and compliant with the principle of least privilege. If a managed policy does not meet your specific needs, you can create a policy to tailor the permissions.

Advantages

Reusability: Managed policies are designed for reuse across multiple IAM identities. They can be within the same or different accounts. This reusability reduces the effort required to define and manage permissions. You can attach the same managed policy to multiple entities.

Central Management: Managed policies are created and managed by AWS. AWS maintains and updates these policies. It ensures that they are kept up-to-date with new AWS services and API operations. This saves you from writing and maintaining complex policies yourself.

Disadvantages

Limited Customization: While AWS provides a broad selection of managed policies, they may not perfectly align with your needs. In such cases, you might need to combine multiple managed policies.

Large Policy Sets: As the number of managed policies increases in your AWS account, it might become challenging to manage them. Proper organisation and naming conventions can help mitigate this challenge.

Key Differences

The choice between inline and managed policies depends on the level of policy customization required.

Frequently Asked Questions

Can inline policies be shared among multiple IAM entities?

No, inline policies are specific to one IAM entity. They cannot be shared with others. Each IAM entity requires its own copy of the inline policy.

How are managed policies useful for reusability and central management?

Managed policies can be attached to multiple IAM entities, making them reusable. When you update a managed policy, all entities using that policy will inherit the changes. It will facilitate centralised policy management.

Which one is easier to manage in larger AWS environments with complex permission requirements?

Managed policies are easier to manage in larger AWS environments with complex permission requirements since they offer centralised control and easier policy management across multiple IAM entities.

Conclusion

In this article, we learnt about Inline Policies vs Managed Policies. We got to know about these policies by Amazon Web Services and their key differences. Now that you have learnt about it, you can also refer to other similar articles.

• Policies in Chef Infra
• Security Policy
• Azure Policy
   

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