Is it possible to retrieve LTPA token from a custom RM Widget(implemented using JavaScript)?

We are working on creating a custom RM Widget in CLM 5.0 which will perform the functionality of modifying RM artifacts . In order to achieve this, we are making use of a java web service that will perform the core functionality of accessing the RM Server and modifying the RM Artifacts. The RM Widget serves the sole purpose of gathering information required by the web service to perform RM Specific operations.

The issue we are facing is with regards to user authentication. Since the web service and not the actual user is accessing the server, we require the LTPA Token generated for the respective session. We are able to view the LTPA Token using HTTPFox as a cookie. But we are not able to fetch the cookie using the basic document.cookie command.

Also we noticed the the rm widget is located at path\rm(context root of the RDNG Application) and the LTPA token is generated at the path "\" (parent path).

Can anyone help with what exactly have we missed out on?