AWS Cognito: Understanding User Pools vs. Identity Pools

AWS Cognito simplifies the authentication (identity verification) and authorization (access control) processes for web and mobile applications using two main components: Cognito User Pools and Cognito Identity Pools. Understanding the differences and how they work together is crucial for implementing secure and scalable user management and access control in AWS.

Cognito User Pools: Authentication

• Purpose: Cognito User Pools is a scalable and customizable user directory used primarily for user authentication.
• Features:
  • Federation: Supports social logins (e.g., Google, Facebook, Amazon) and corporate logins (via SAML and OIDC).
  • Customizable UI: Allows branding customization, including logos on the hosted UI.
  • Lambda Integration: Offers hooks for customizing the authentication workflow (pre- and post-authentication actions).
  • Adaptive Authentication: Adjusts the sign-in experience based on risk levels, employing Multi-Factor Authentication (MFA) as necessary.

Cognito Identity Pools: Authorization

• Purpose: Facilitates authorization by granting authenticated and guest users access to AWS resources.
• Functionality:
  • Temporary AWS Credentials: Provides IAM roles and policies for users accessing AWS services like DynamoDB and S3.
  • Token Exchange: Users can exchange identity tokens (from social logins or Cognito User Pools) for AWS access tokens.
  • Unauthenticated Access: Supports access for guest users, allowing for flexible user engagement scenarios.
  • IAM Role Mapping: Users are mapped to IAM roles based on identity, enabling fine-grained access control with policy variables.

Integration and Use Cases

• Scenario: A mobile application requires user authentication and authorization to access private AWS resources (e.g., S3 Bucket, DynamoDB Table) on a per-user basis.
• Best Practices:
  1. Authentication: To verify their identities, users log in via Cognito User Pools (using social, SAML, or OIDC logins).
  2. Authorization: The application exchanges the authentication token for temporary AWS credentials using Cognito Identity Pools.
  3. Access Control: STS (Security Token Service) manages temporary credentials to ensure users can only perform allowed actions as defined in IAM policies.

Summary

• Cognito User Pools are about authentication, acting as a user directory with extensive login and customization options.
• Cognito Identity Pools are about authorization, enabling access to AWS services with temporary credentials based on IAM roles and policies.
• Together, they offer a comprehensive solution for managing user identity and access within AWS, supporting authenticated and guest users with scalable and secure access control mechanisms.

Understanding the distinct roles and integration of Cognito User Pools and Identity Pools is fundamental for developers implementing AWS-based authentication and authorization in their applications.