Sharing Security Context between web app and RESTful service using Spring Security - rest

Question

We are designing security for a green field project with a UI web module (Spring MVC) - the client, and a RESTful services web module (CXF) - the server, to be deployed as separate war files in the same Websphere app server. The system should be secured with Spring Security, authenticating against LDAP and authorizing against a database. We have been looking for the best solution to share the security context between the 2 apps, so a user can authenticate in the web UI and invoke its AJAX calls to the secured RESTful services. Options found:
OAuth: seems overkill for our requirements, introduces a fairly complex authentication process, and reportedly some enterprise integration issues
CAS: would amount to setting up an enterprise SSO solution, something beyond the scope of our engagement
Container-based (Websphere) security, although not recommended by Spring Security, and we're not clear if this could provide a solution to our specific needs
We're looking for a simpler solution. How can we propagate the Security Context between the 2 apps? Should we implement authentication in the UI web app, then persist sessions in the DB, for the RESTful services to lookup? Can CXF provide a solution? We read many threads about generating a 'security token' that can be passed around, but how can this be done exactly with Spring Security, and is it safe enough?
Looking forward to any thoughts or advice.

Answer 1

You want to be able to perform the REST web services on the server on behalf the user authenticated in UI web module.
The requirements you described called SingleSignOn.
The simplest way to do it is passing the HTTP header with the user name during REST WS calls.
(I hope your REST client allows to do it).
To do it in secure way use one of the following:
Encrypt the user name in REST client and decrypt it in REST server
Ensure that the header is sent from the local host (since your application deployed on the same container)
Therefore, protect both application using SpringSecurity authenticate against LDAP.
In the first application (Rest Client) use regular Form Authentication
In the second application (Rest Server) add the your own PreAuthenticatedProcessingFilter:
http://static.springsource.org/spring-security/site/docs/3.1.x/reference/springsecurity-single.html#d0e6167
Edited
The “Authentication” is the process of verifying of a principal’s identity.
In our case both REST Client (Spring MVC application) and REST server (CXF application) verify an identity against LDAP. LDAP “says” OK or Not. LDAP is a user repository. It stateless and does not remember the previous states. It should be kept in applications.
According to my understanding, a user will not access directly to REST server – the user always access REST Client. Therefore, when the user access REST Client he/ she provides a user name and a password and REST Client authenticate against LDAP. So, if REST Client access REST server the user is authenticated and REST Client knows his name.
So, if request come to REST server with a user header name - REST server for sure knows that the user was authenticated and it should not authenticate it again against LDAP.
(The header should be passed in the secured way as described above).
Rest Server should take the user name, to access to LDAP and to collect related user information without providing of the user password (since the user already authenticated).