[AWS] IDF, Cognito, and SSO

IDF (Identity Federation) is an architecture where the identities of an external identity provider (IDP) are recognized.

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Types of IDF

• Cross-account roles: A remote account is allowed to assume a role and access your account’s resources,
• SAML 2.0 IDF: It allows users of SAMAL compatible system such as Active Directory (AD) to log in to the AWS services.
• Web Identity Federation: External web-based IDPs (Google, Facebook) are allowed to assume roles.

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When to use IDF

• Enterprise Access to AWS
  • Enterprise users with existing identities such as Active Directory.
  • Users can access to AWS using SSO (Single Sign-On).
  • With a lot of potential users that IAM cannot easily handle.
• Web & Mobile Users
  • Users can use existing web identities.
  • You do not need to store user credentials within the application.
  • There might be a lot of users (millions or more).

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Cognito and STS

Cognito and STS (Secure Token Service) are used for IDF in AWS.

• When a federated identity is verified by an external IDP, the identity is swapped with the temporary AWS credentials by assuming a proper role.

• AWS Cognito is a superset of the functionality of web identity federation (sign-in directly or through 3rd parties).
  • Sign-up and sign-in, Guest access, and Synchronize user data
  • Recommended for mobile applications

User Pool

• acts as an Identity Provider (IdP) and authenticates a user (user id, password)
  • It supports the IdP standards, such as Oauth 2, SAML 2, and OpenID Connect.
  • You can use social media IdPs such as Google or Amazon.
• issues three JWTs(JSON Web Tokens) that can be used for authorizations
  • Identity Token
    • authorizes API calls
    • contains claims of the user (name or email)
    • signed but not encrypted
  • Access Token
    • specifies access-protected resources
    • signed but not encrypted
    • 5 minutes ~ 24 hours
  • Refresh Token
    • contains the information necessary to obtain a new ID or Access token
    • encrypted
    • 1 hour ~ 10 years

Identity Pool

https://docs.aws.amazon.com/cognito/latest/developerguide/authentication-flow.html

• creates unique identity as an authentication
• issues a temporary AWS credentials and grant permissions to AWS resources (authorization)

Scenarios

You can use the User Pool and the Identity Pool to common authentication/authorization scenarios. Check the following documentation.

Common Amazon Cognito scenarios – Amazon Cognito

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User Pool with Lambda Triggers

You can customize user pool workflows with Lambda triggers.

• Pre sign-up
• Post confirmation
• Pre authentication
• Post authentication
• Migrate user

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Amazon Cognito Sync

Amazon Cognito Sync is an AWS service and client library that enable cross-device syncing of application-related user data.

• You can use it to synchronize user profile data across mobile devices and web applications.

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Use Case: Allow temporary access to S3 for AD users

You can use STS to generate a temporary token and allow users to access with IAM roles.

1. A user makes request to IDP (Identity Provider)
2. IDP authenticates a user
3. IDP sends a user SAML assertion
4. A user calls “assumeRole” with SAML
5. STS returns temporary security tokens
6. A user uses tokens to access AWS resources such as S3

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Tracking Devices

You can track and remember user devices using Cognito.

• You can see the remembered devices and associated metadata through the console.
• You can build custom functionality such as limiting the number of devices from a single end-user.

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AWS IAM Identity Center

AWS AM Identity Center is where the credentials of an external identity are used to allow access to a local system (e.g., AWS).

• formerly known as AWS Single Sign-On (SSO)
• IAM identity Center offers pre-configured SAML 2.0 (Security Assertion Markup Language) integration to many business applications (Salesforce, Office365) and On-premise Microsoft Active Directory through AD trust.