How to protect an application running on Apache Tomcat app server with OAM 11gR2

Question

Gurus,
We have an Apache Tomcat based application named "ABCD" here at client site that we want OAM 11gR2 PS1 to integrate with for SSO purposes. I have successfully configured OHS to reverse proxy requests to Apache Tomcat server whenever somebody tries to access the application URL but still, I am getting the application login page once I have successfully authenticated on OAM SSO login page. The Tomcat based application is authenticating users against a "UserDatabase realm".
I know in terms of weblogic application, there is an OAM identity asserter provider which then populates the User Principal for the java environment with the authenticated OAM user. But there is no such OAM identity provider for Tomcat.
So my question is, is there an provider (or Tomcat equivalent) which will entrust authentication to a header, that could be used to populate the Java User Principal from the OAM_REMOTE_USER header? Is the weblogic equivalent of authentication providers present in tomcat as well? Are those called valves?
Please advise to the earliest.
Thanks !!

Answer 1

Aakash,
I did follow the 4 steps that you mentioned to me. Out of the 4 that you had mentioned, I already had the webgate in place on OHS server and I was already passing the remote_user http header in oam policy as action.
As part of Step #2: Install mod_jk plugin on OHS server that you mentioned
1.) I downloaded the tomcat connector - tomcat-connectors-1.2.37-src
2.) I had to run ./configure,make, make install on my OHS server which runs on RHEL 6. It created the mod_jk.so file. I pasted it in the needed folder.
3.) I then created the httpd.conf file and workers.properties file as said in the connector docs.
4.) Restarted OHS.
As part of Step #3: Configure tomcat's ajp connector that you mentioned and I went through all the links pasted below but didn't find actually what needs to be in place to configure tomcat's ajp connector. I do see in the server.xml of tomcat app server that the ajp 1.3 protocol is supported:
http://tomcat.apache.org/tomcat-4.0-doc/config/ajp.html
http://tomcat.apache.org/tomcat-3.3-doc/mod_jk-howto.html#s8
http://tomcat.apache.org/tomcat-7.0-doc/config/ajp.html
http://www.mulesoft.com/understanding-tomcat-connectors
<!-- A "Connector" represents an endpoint by which requests are received
         and responses are returned. Documentation at :
         Java HTTP Connector: /docs/config/http.html (blocking & non-blocking)
         Java AJP  Connector: /docs/config/ajp.html
         APR (HTTP/AJP) Connector: /docs/apr.html
         Define a non-SSL HTTP/1.1 Connector on port 8080
    -->
    <Connector port="8080" protocol="HTTP/1.1"
               connectionTimeout="20000"
               redirectPort="8443" />
<!-- Define an AJP 1.3 Connector on port 8009 -->
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
Do we need to disable the HTTP protocol in Tomcat and keep only AJP connector enabled? If yes, how to do that?
I am trying to connect to the application from OHS server like so I am using the http protocal right? How should I use the ajp protocol to connect to tomcat application? 
http://ohs-host:ohs-port/abcd
Thanks !!!!!