AWS IAM vs OAuth2: What are the differences?

Introduction: In this article, we will discuss the key differences between AWS IAM (Identity and Access Management) and OAuth2 (Open Authorization). Both IAM and OAuth2 are used for authentication and authorization, but they have distinct differences in their usage and capabilities.

1. Scalability and Purpose: AWS IAM is specifically designed for managing access to AWS resources, allowing users to control who can use which services and resources within their AWS account. On the other hand, OAuth2 is an open standard for authorization that is not limited to a specific platform or service. It is commonly used for granting access to third-party applications or APIs.

2. User Management: With AWS IAM, user management and authentication are done within the AWS ecosystem. It provides centralized control and administration of users, groups, and permissions. In OAuth2, user management is typically handled by the application or service implementing it. It relies on external identity providers (such as social media platforms) for user authentication, rather than managing users internally.

3. Granularity of Permissions: IAM allows fine-grained control over permissions, allowing administrators to assign specific access policies to individual users or groups. It supports both predefined and custom policies, offering more control over access to AWS resources. In OAuth2, access tokens are used to grant access to specific resources, but the level of granularity is dependent on how the authorization server implements it. It generally provides broader authorization scopes for granting access.

4. Token-based Authentication vs Role-based Access: AWS IAM primarily uses role-based access control (RBAC) to manage access permissions within the AWS ecosystem. Users assume specific roles to access resources. OAuth2, on the other hand, relies on token-based authentication to grant access. It uses access tokens and refresh tokens to authenticate and authorize users, allowing them to access resources on behalf of the requesting application.

5. Centralized Access Control vs Decentralized Authorization: AWS IAM provides centralized access control, allowing administrators to manage permissions and access policies from a single location. It provides a unified view of IAM users, groups, roles, and policies. OAuth2, on the other hand, follows a decentralized authorization model, where the authorization server and resource server can be separate entities. The authorization server issues access tokens, but it is not responsible for enforcing access policies on the resource server.

6. Managed Service vs Standardized Protocol: AWS IAM is a managed service provided by Amazon Web Services and is tightly integrated with their platform. It offers a comprehensive set of features for managing access to AWS resources. On the other hand, OAuth2 is not a service but a standardized protocol. It can be implemented by any application or service, providing a consistent way to handle authorization and access control.

In summary, AWS IAM is a scalable and purpose-built service for managing access to AWS resources, offering granular permissions, centralized control, and role-based access. OAuth2, on the other hand, is a standardized protocol for authorization, allowing access to third-party applications or APIs, with a focus on token-based authentication and decentralized authorization.