IDF (Identity Federation) is an architecture where the identities of an external identity provider (IDP) are recognized.
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.
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).
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 authenticates a user (user id, password) and gets tokens.
- Identity Pool exchanges tokens for temporary AWS credentials. (authorization)
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.
- A user makes request to IDP (Identity Provider)
- IDP authenticates a user
- IDP sends a user SAML assertion
- A user calls “assumeRole” with SAML
- STS returns temporary security tokens
- A user uses tokens to access AWS resources such as S3
Single Sign-On (SSO)
AWS SSO is where the credentials of an external identity are used to allow access to a local system (e.g., AWS).
- AWS SSO 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.
