This is an example of an External Auth module to be plugged into a Shibboleth Identity Provider.

It is a simple External Auth that does 2 things:

1. GET: Redirect the User to a custom JSP webpage with a form for a username
2. POST: Takes the username from the form and creates a Java Subject, setting the username as the Username Principal.

NOTE: Your custom webpage will need to match the file name that is in the GET method. Your form will also need to submit the correct parameter in the POST as well (userName in this instance).

I recommend IntelliJ for this.

1. Build Project
2. File > Project Structure > Project Settings > Artifacts
3. Hit the + > JAR > From project with dependencies > OK

(Next part is a bit tricky and something I don't know how to do yet via code/commands)

4. Move your jar into a folder and run jar xf <JAR NAME>.jar
5. Remove all files except for external/ExternalAuth.class and the META-INF/MANIFEST.MF. There is an example jar directory example-jar-directory. Instead of removing files you can also just add the necessary ones into a new folder.
6. Jar it back up with a name jar cvf <JAR NAME>.jar -C <FOLDER-NAME>/ .

Make sure authn/External bean is enabled in general-authn.xml and that the external-authn-config.xml is present.

Make sure your JSP webpage is in webapp/ directory.

In web.xml, add the following servlet:

<!-- Servlet for receiving a callback from an external Server and continues the IdP login flow -->
 <servlet>
    <servlet-name>ExternalAuth</servlet-name>
    <servlet-class>external.ExternalAuth</servlet-class>
    <load-on-startup>2</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>ExternalAuth</servlet-name>
    <url-pattern>/Authn/External/*</url-pattern>
</servlet-mapping>

Route some auth flows through the External Module