An interop demo between Apache CXF Fediz and Google OpenID Connect

The previous post introduced some of the new features in Apache CXF Fediz 1.3.0. One of the new enhancements is that the Fediz IdP can now delegate WS-Federation (and SAML SSO) authentication requests to a third party IdP via OpenID Connect. An article published in February showed how it is possible to interoperate between Fediz and the Keycloak OpenID Connect provider. In this post, we will show how to configure the Fediz IdP to interoperate with the Google OpenID Connect provider.

1) Create a new client in the Google developer console

The first step is to create a new client in the Google developer console to represent the Apache CXF Fediz IdP. Login to the Google developer console and create a new project. Click on "Enable and Manage APIs" and then select "Credentials". Click on "Create Credentials" and select "OAuth client id". Configure the OAuth consent screen and select "web application" as the application type. Specify "https://localhost:8443/fediz-idp/federation" as the authorized redirect URI. After creating the client, a pop-up window will specify the newly created client id and secret. Save both values locally. The Google documentation is available here.

2) Testing the newly created Client

It's possible to see the Google OpenId Connect configuration by navigating to:

• https://accounts.google.com/.well-known/openid-configuration

This tells us what the authorization and token endpoints are, both of which we will need to configure the Fediz IdP. To test that everything is working correctly, open a web browser and navigate to, substituting the client id saved in step "1" above:

• https://accounts.google.com/o/oauth2/v2/auth?response_type=code&client_id=<client-id>&redirect_uri=https://localhost:8443/fediz-idp/federation&scope=openid

Login using your google credentials and grant permission on the OAuth consent screen. The browser will then attempt a redirect to the given redirect_uri. Copy the URL + extract the "code" query String. Open a terminal and invoke the following command, substituting in the secret and code extracted above:

• curl -u <client-id>:<secret> --data "client_id=<client-id>&grant_type=authorization_code&code=<code>&redirect_uri=https://localhost:8443/fediz-idp/federation" https://www.googleapis.com/oauth2/v4/token

You should see a succesful response containing (amongst other things) the OAuth 2.0 Access Token and the OpenId Connect IdToken, containing the user identity.

3) Install and configure the Apache CXF Fediz IdP and sample Webapp

Follow a previous tutorial to deploy the latest Fediz IdP + STS to Apache Tomcat, as well as the "simpleWebapp". Note that you will need to use Fediz 1.3.0 here for OpenId Connect support. Test that the "simpleWebapp" is working correctly by navigating to the following URL (selecting "realm A" at the IdP, and authenticating as "alice/ecila"):

• https://localhost:8443/fedizhelloworld/secure/fedservlet 

3.1) Configure the Fediz IdP to communicate with the Google IdP

Now we will configure the Fediz IdP to authenticate the user in "realm B" by using the OpenID Connect protocol. Edit 'webapps/fediz-idp/WEB-INF/classes/entities-realma.xml'. In the 'idp-realmA' bean:

• Change the port in "idpUrl" to "8443". 

In the 'trusted-idp-realmB' bean:

• Change the "url" value to "https://accounts.google.com/o/oauth2/v2/auth".
• Change the "protocol" value to "openid-connect-1.0".
• Delete the "certificate" and "trustType" properties.
• Add the following parameters Map, filling in a value for the client secret extracted above: <property name="parameters">
              <util:map>
                  <entry key="client.id" value="<client-id>" />
                  <entry key="client.secret" value="<secret>" />
                  <entry key="token.endpoint" value="https://accounts.google.com/o/oauth2/token" />
                  <entry key="scope" value="openid profile email"/>
                  <entry key="jwks.uri" value="https://www.googleapis.com/oauth2/v3/certs" />
                  <entry key="subject.claim" value="email"/>
              </util:map>
          </property>

There are a few additional properties configured here compared to the previous tutorial. It is possible to specify custom scopes via the "scope" parameter. In this case we are requesting the "profile" and "email" scopes. The default value for this parameter is "openid". In addition, rather than validating the signed IdToken using a local certificate, here we are specifying a value for "jwks.uri", which is the location of the signing key. The "subject.claim" property specifies the claim name from which to obtain the Subject name, which is inserted into a SAML Token that is sent to the STS.

3.2) Update the TLS configuration

By default, the Fediz IdP is configured with a truststore required to access the Fediz STS. However, this would mean that the requests to the Google IdP over TLS will not be trusted. to change this, edit 'webapps/fediz-idp/WEB-INF/classes/cxf-tls.xml', and change the HTTP conduit name from "*.http-conduit" to "https://localhost.*". This means that this configuration will only get picked up when communicating with the STS (deployed on "localhost"), and the default JDK truststore will get used when communicating with the Google IdP.

3.3) Update Fediz STS claim mapping

The STS will receive a SAML Token created by the IdP representing the authenticated user. The Subject name will be the email address of the user as configured above. Therefore, we need to add a claims mapping in the STS to map the principal received to some claims. Edit 'webapps/fediz-idp-sts/WEB-INF/userClaims.xml' and just copy the entry for "alice" in "userClaimsREALMA", changing "alice" to your Google email address.

Finally, restart Fediz to pick up the changes (you may need to remove the persistent storage first).

4) Testing the service

To test the service navigate to:

• https://localhost:8443/fedizhelloworld/secure/fedservlet

Select "realm B". You should be redirected to the Google authentication page. Enter the user credentials you have created. You will be redirected to Fediz, where it converts the received JWT token to a token in the realm of Fediz (realm A) and redirects to the web application.