AWS IAM Federation

1. Introduction

AWS Identity and Access Management (IAM) Federation allows users to authenticate to AWS using external identity providers. This capability enables organizations to manage user identities and permissions in a centralized manner, allowing for seamless integration with other systems and reducing the overhead of managing multiple user accounts.

2. Key Concepts

**Federated Users**: Users that authenticate using an external identity provider (IdP) rather than IAM users.
**Identity Provider (IdP)**: A service that manages user identities and provides authentication, such as Google, Facebook, or a corporate directory.
**SAML**: Security Assertion Markup Language, a standard for exchanging authentication and authorization data between parties, especially between an IdP and a service provider like AWS.
**Web Identity Federation**: Allows users to log in to AWS using credentials from web identity providers (e.g., Amazon, Facebook, Google).

3. Step-by-Step Process

3.1 Setting Up IAM Federation with SAML

Create a SAML Identity Provider in AWS

aws iam create-saml-provider --name MySAMLProvider --saml-metadata-document file://my-saml-metadata.xml

Create a Role for the Federated Users

aws iam create-role --role-name MyFederatedRole --assume-role-policy-document file://trust-policy.json

Attach Policies to the Role

aws iam attach-role-policy --role-name MyFederatedRole --policy-arn arn:aws:iam::aws:policy/AmazonS3ReadOnlyAccess

Configure Your IdP to Trust AWS
Ensure that your IdP is set up to trust AWS and that it sends the required attributes (like Role ARN) in the SAML assertion.
Test the Federation
Use a SAML assertion from your IdP to assume the role in AWS and access resources.

Note: Ensure that your SAML assertion includes the required attributes, such as Role and Principal.

4. Best Practices

Regularly review and audit roles and policies associated with federated access.
Implement strong security measures for your IdP, including multi-factor authentication (MFA).
Limit permissions granted to federated users to the minimum necessary for their tasks.
Use temporary security credentials whenever possible to enhance security.

5. FAQ

What is the benefit of IAM Federation?

IAM Federation allows centralized management of user identities and permissions, reducing the complexity of managing multiple AWS accounts and improving security through the use of external identity providers.

Can I use IAM Federation with non-SAML IdPs?

Yes, AWS also supports Web Identity Federation, which allows users to authenticate using providers like Google and Facebook.

What is a SAML assertion?

A SAML assertion is a package of information that contains the authentication and authorization information about a user, allowing for secure SSO (Single Sign-On) across different applications.