Using a WebSphere Application Server API to achieve downstream web single sign-on with an LtpaToken2 cookie

You can programmatically perform downstream Single Sign On (SSO) web propagation of a Lightweight Third Party Authentication (LTPA) cookie without the need for an application to store and send user credentials.

WebSphere® Application Server provides API support to propagate an LtpaToken2 cookie to downstream web single sign-on applications.

Web applications running in mid-tier WebSphere servers might need to propagate LtpaToken2 cookies on downstream web invocations. In this release of WebSphere Application Server, a new Application Programming Interface (API) is provided for application developers to programmatically perform downstream SSO without the need for an application to store and send user credentials.

Figure 1. Use of the LTPA Cookie API for downstream authentication

This function is a public API in package com.ibm.websphere.security.WSSecurityHelper, and is defined as follows:

/**
   * Extracts an LTPA sso token from the subject of current
   * thread and builds a ltpa cookie out of it for use on
   * downstream web invocations. 
   * When the returned value is not null use Cookie methods
   * getName() and getValue() to set the Cookie header
   * on an http request with header value of
   * Cookie.getName()=Cookie.getValue()
   *
   * @return an object of type javax.servlet.http.Cookie. 
   * 
   */

The following is an example of how you can use the new WSSecurityHelper API:

import javax.servlet.http.Cookie;
import com.ibm.websphere.security.WSSecurityHelper;

Cookie ltpaCookie = WSSecurityHelper.getLTPACookieFromSSOToken()

Deprecated feature: The getLTPACookieFromSSOToken() method from the WSSecurityHelper class is deprecated. Use the functionality provided by the getSSOCookieFromSSOToken() method from the WebSecurityHelper class.

Subsequently, the LTPA cookie can be set on an HTTP request header. In this case, the value of the cookie header is the string:

ltpaCookie.getName()=ltpaCookie.getValue()

For example, if you use org.apache.commons.httpclient.HttpMethod to build your HTTP request, the LTPA cookie can be set as follows:

HttpMethod method = .;  // new your HttpMethod based on the
                        // target URL for the web application
if (ltpaCookie != null)
     method.setRequestHeader("Cookie", ltpaCookie.getName()+"="+ltpaCookie.getValue());

Note: You should only send LTPA cookies over SSL connections.

Note: You must check whether the LTPA cookie that is returned from calling WSSecurityHelper.getLTPACookieFromSSOToken() in the previous example is not null before you issue any getter methods. Also, to successfully retrieve a LTPA cookie object, and to ensure an SSO token on the thread of execution, make sure that the user has established a successful authentication with the mid-tier server.

Note: WebSphere Application Server does not ship supporting jars for HTTP programming, such as the Apache httpclient. You must provide your own supporting functions for HTTP programming.