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Demo : Authorization using AWS IAM Identity Center (SSO) at CloudFront with Lambda@Edge

This is a demonstration for authorization using AWS IAM Identity Center (SSO) at CloudFront with Lambda@Edge.

Add a SAML identity provider with IAM Identity Center (SSO) to the Cognito User Pool to authenticate users. The user pool will return an ID, access, and refresh tokens. The ID token is a standard OIDC token, and the access token is a standard OAuth 2.0 token. You are allowed access to the web app without re-authentication until the ID token expire.

This project is for demonstration purposes only, not for production environment.

For more information, see the following documents: https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-pools-saml-idp.html

Architecture Overview

Architecutre diagram

Following AWS resources are deployed by CDK:

  • Amazon Cognito
  • Amazon CloudFront
  • Lambda@Edge and IAM Role

... and you need to configure manually following AWS service:

  • IAM Identity Center (SSO)

Request Flow

Sequence diagram

Pre-Requirements & Limitations

  • IAM Identity Center (SSO) must be preconfigured
  • CDK must be installed and available
  • Docker must be available (for bundling Lambda@Edge)
  • In this demo, the origin is not accessed after authentication; Lambda@Edge returns html directly
  • In this demo, not support Sing Out
  • This project is for demonstration purposes only, not for production environment

How To Deploy

(Sorry, but the deployment steps are a bit complicated...)

1. Decide Cognito Domain

First determine the Cognito domain, which must be a unique in the Region. This demo does not support custom domain.

2. Configure SSO Application

2-1. Add Application

  1. Open IAM Identity Center (SSO) in AWS Management Console
  2. Choice Applications from left menu pane
  3. Add Application
  4. Select Add custom SAML 2.0 application and Next
  5. In Configure application section, configure Display Name and Description
  6. In IAM Identity Center metadata section, note the IAM Identity Center SAML metadata URL
  7. In Application metadata section, configure Application ACS URL and Application SAML audience
    • Application ACS URL : https://<Cognito Domain>.auth.<Cognito Region>.amazoncognito.com/saml2/idpresponse
    • Application SAML audience : urn:amazon:cognito:sp:<Cognito User Pool ID>
      • (The User Pool ID is not known at this time, so set a temporary value and change it later. For example: urn:amazon:cognito:sp:ABC)
  8. Submit

2-2. Edit Attribute Mappings

  1. Return to your application, then Edit attribute mappings in Actions
  2. Subject attribute maps to ${user:subject}, Format is unspecified
  3. Add new attribute mapping
  4. Input following values:
  5. Save changes

2-3. Assign User or Group

  1. Return to your application, then choice Assign Users
  2. Assing users or groups

3. Configure your context parameter

Configure cognitoNamePrefix, cognitoDomain, and cognitoSamlMetadataDocEndpoint in cdk.json like following:

  • cognitoNamePrefix : the name prefix for User Pool, ID Provider and App Client names
  • cognitoDomain : determined in the first step
  • cognitoSamlMetadataDocEndpoint : the URL noted as IAM Identity Center SAML metadata in the previous step 2-1-6

(cognitoCallbackUrl is going to be replaced after other step.)

{
  // :
  // (snip)
  // :
  "context": {
    // :
    // (snip)
    // :
    "cloudfront-lambdaedge-cognito-saml-auth": {
      "cognitoNamePrefix": "my-organization-sso",
      "cognitoDmain": "my-organization",
      "cognitoCallbackUrl": "https://TENTATIVE",
      "cognitoCallbackPath": "/auth",
      "cognitoSamlMetadataDocEndpoint": "https://portal.sso.us-east-1.amazonaws.com/saml/metadata/xxxxxxxxxx"
    }
  }
}

cognitoNamePrefix is the name prefix for User Pool, ID Provider and App Client names.

4. Deploy Cognito Stack

cdk deploy CognitoSamlAuthStack

After deployment complete, you cat get User Pool ID, App Client ID, and so on.

5. Update SSO Application SAML Audience

  1. Open IAM Identity Center (SSO) in AWS Management Console
  2. Choice Applications from left menu pane
  3. Choice your application (linked application name)
  4. Edit configuration in Actions
  5. In Application metadata section, update Application SAML audience with Cognito user pool ID
    • For example : urn:amazon:cognito:sp:us-east-1_ABCdefgh0
  6. Submit

6. Deploy CloudFront And Lambda@Edge Stack

cdk deploy CloudfrontLambdaEdgeStack

After deployment complete, you cat get CloudFront distribution domain name and so on.

7. Update Context Parameter

Configure cognitoCallbackUrl in cdk.json with CloudFront distribution domain which you got previous step like following:

{
  // :
  // (snip)
  // :
  "context": {
    // :
    // (snip)
    // :
    "cloudfront-lambdaedge-cognito-saml-auth": {
      // :
      // (snip)
      // :
      "cognitoCallbackUrl": "https://dXXXXXXXXXXXXX.cloudfront.net",
      // :
      // (snip)
      // :
    }
  }
}

8. Update Lambda@Edge Function Code

Configure Cognito related values in assets/lambda-edge/app.py. Lambda@Edge does not support environment variables, so edit the code directly.

CONTENT_DOMAIN = 'dXXXXXXXXXXXXX.cloudfront.net'

COGNITO_REGION = 'us-east-1'
COGNITO_USERPOOL_ID = 'us-east-1_ABCdefgh0'
COGNITO_APP_CLIENT_ID = 'xxxxxxxxxxxxxxxxxx'
COGNITO_IDENTITY_PROVIDER='my-organization-sso-idp'
COGNITO_DOMAIN = 'my-organization'

9. Re-deploy CDK Stacks

cdk deploy --all

Check Behavior

Access https://dXXXXXXXXXXXXX.cloudfront.net via your browser.
After authentication, Lambda@Edge does not forward the request to the origin for simplicity, but returns HTML directly.

How To Clean Up

You can clean up by following command:

cdk destroy --all

Lisence

MIT