Overview

Google Apps for Education (or any of the Google Apps) utilizes SAML 2.0 to provide an integration point for external authentication services.

Usage

The Google Apps for Education integration described here allows CAS to act as a miniaturized SAML2 identity provider, for deployments that may not be prepared to turn on and allow CAS to fully act as a SAML2 identity provider. This feature is deprecated and is scheduled to be removed in the future. It does not make much sense to turn on and use both features in CAS at the same time, as one outranks the other and it is likely that using both features in CAS simultaneously would interfere with the functionality of both. If you can, consider using the SAML2 identity provider functionality in CAS to handle this integration as you would any other SAML2 service provider.

Support is enabled by including the following dependency in the WAR overlay:

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<dependency>
  <groupId>org.apereo.cas</groupId>
  <artifactId>cas-server-support-saml-googleapps</artifactId>
  <version>${cas.version}</version>
</dependency>

Generate Public/Private Keys

The first step is to generate DSA/RSA public and private keys. These are used to sign and read the Assertions. After keys are created, the public key needs to be registered with Google.

The keys will also need to be available to the CAS application (but not publicly available over the Internet) via the classpath though any location accessible by the user running the web server instance and not served publicly to the Internet is acceptable. Thus, inside src/main/resources is nice because it is scoped to the web application but not normally served. /etc/cas/ is also fine as well and protects the key from being overwritten on deploy of a new CAS webapp version.

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openssl genrsa -out private.key 1024
openssl rsa -pubout -in private.key -out public.key -inform PEM -outform DER
openssl pkcs8 -topk8 -inform PER -outform DER -nocrypt -in private.key -out private.p8
openssl req -new -x509 -key private.key -out x509.pem -days 365

The x509.pem file should be uploaded into Google Apps under Security/SSO.

To see the relevant list of CAS properties, please review this guide.

Register Google Apps

Ensure that Google Apps is registered in your service registry.

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{
  "@class" : "org.apereo.cas.services.RegexRegisteredService",
  "serviceId" : "https://www.google.com/a/YourGoogleDomain/acs",
  "name" : "googleApps",
  "id" : 1000,
  "evaluationOrder" : 10
}

Configure Username Attribute

As an optional step, you can configure an alternate username to be send to Google in the SAML reply. This alternate user name can be specified in the CAS service registry via username attribute providers for the registered Google Apps service.

Configure Google

You’ll need to provide Google with the URL for your SAML-based SSO service, as well as the URL your users will be redirected to when they log out of a hosted Google application. Use the following URLs when you are configuring for Google Apps:

  • Sign-in page URL: https://sso.school.edu/cas/login
  • Sign-out page URL: https://sso.school.edu/cas/logout
  • Change password URL: https://mgmt.password.edu/

Test

Attempt to access a Google-hosted application, such as Google Calendar with the url: https://calendar.google.com/a/YourGoogleDomain