Trust associations


 

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Trust association enables the integration of WAS security and third-party security servers.

A reverse proxy server acts as an authentication server, passing authenticated user credentials to back to WAS, which applies its own authorization policy to the credentials.

 

Trust association model

WAS and the proxy server engage in a contract in which WAS gives its full trust to the proxy server and the proxy server applies its authentication policies on every Web request that is dispatched to WAS. This trust is validated by the interceptors residing in WAS environment for every request received. The method of validation is agreed upon by the proxy server and the interceptor.

Running in trust association mode does not prohibit WAS from accepting requests that did not pass through the proxy server. In this case, no interceptor is needed for validating trust. WAS supports the following TAI interfaces:

com.ibm.ws.security.web.TAMTrustAssociationInterceptorPlus

This TAI interceptor implementation that implements the new WAS interface supports WAS V5.1.1 and later. The interface supports WebSEAL V5.1, but does not support WebSEAL V4.1.

com.ibm.ws.security.spnego.TrustAssociationInterceptorImpl

This interceptor is new to this release. SPNEGO has replaced SPNEGO TAI as the Web authenticator for WAS.

 

IBM WAS: WebSEAL Integration

The integration of WebSEAL and WAS security is achieved by placing the WebSEAL server at the front-end as a reverse proxy server. From a WebSEAL management perspective, a junction is created with WebSEAL on one end, and WAS Web server on the other end. A junction is a logical connection that is created to establish a path from the WebSEAL server to another server.

In this setup, a request for Web resources that are stored in a protected domain of WAS is submitted to the WebSEAL server where it is authenticated against the WebSEAL security realm. If the requesting user has access to the junction, the request is transmitted to the WAS HTTP server through the junction, and then to the application server.

Meanwhile, WAS validates every request that comes through the junction to ensure that the source is a trusted party. This process is referenced as validating the trust and it is performed by a WebSEAL product-designated interceptor. If the validation is successful, WAS authorizes the request by checking whether the client user has the required permissions to access the Web resource. If so, the Web resource is delivered to the WebSEAL server through the Web server, which then gives the resource to the client user.

 

WebSEAL server

The policy director delegates all of the Web requests to its Web component, the WebSEAL server. One of the major functions of the server is to perform authentication of the requesting user. The WebSEAL server consults a LDAP directory. It can also map the original user ID to another user ID, such as when global single sign-on (GSO) is used.

For successful authentication, the server plays the role of a client to WAS when channeling the request. The server needs its own user ID and password to identify itself to WAS. This identity must be valid in the security realm of WAS. The WebSEAL server replaces the basic authentication information in the HTTP request with its own user ID and password. In addition, WAS must determine the credentials of the requesting client so that the appserver has an identity to use as a basis for its authorization decisions. This information is transmitted through the HTTP request by creating a header called iv-creds, with the TAM user credentials as its value.

 

HTTP server

The junction that is created in the WebSEAL server must get to the HTTP server that serves as the product front end. However, the HTTP server is shielded from knowing that trust association is used. As far as it is concerned, the WebSEAL product is just another HTTP client, and as part of its normal routines, it sends the HTTP request to WAS ND. The only requirement on the HTTP server is a SSL configuration using server authentication only. This requirement protects the requests that flow within the junction.

 

Web collaborator

When trust association is enabled, the Web collaborator manages the interceptors that are configured in the system. The Web collaborator loads and initializes these interceptors when you restart the servers. When a request is passed to WAS by the Web server, the Web collaborator eventually receives the request for a security check. Two actions must take place:

  1. The request must be authenticated.
  2. The request must be authorized.

The Web authenticator is called to authenticate the request by passing the HTTP request. If successful, a good credential record is returned by the authenticator, which the Web collaborator uses to base its authorization for the requested resource. If the authorization succeeds, the Web collaborator indicates to WAS that the security check has succeeded and that the requested resource can be served.

 

Web authenticator

The Web authenticator is asked by the Web collaborator to authenticate a given HTTP request. Knowing that trust association is enabled, the task of the Web authenticator is to find the appropriate trust association interceptor to direct the request for processing. The Web authenticator queries every available interceptor. If no target interceptor is found, the Web authenticator processes the request as though trust association is not enabled.

WAS V4 through WAS V6.x support the interface...

com.ibm.websphere.security.TrustAssociationInterceptor.java

WAS V7.0.x and later supports the interface...

com.ibm.ws.security.spnego.TrustAssociationInterceptorImpl

 

Trust association interceptor interface

The intent of the trust association interceptor interface is to have reverse proxy security servers (RPSS) exist as the exposed entry points to perform authentication and coarse-grained authorization, while WAS enforces further fine-grained access control. Trust associations improve security by reducing the scope and risk of exposure.

In a typical e-business infrastructure, the distributed environment of a company consists of...

Such reverse proxy servers, front-end security servers, or security plug-ins registered within Web servers, guard the HTTP access requests to the Web servers and the Web appservers. While protecting access to the URIs, these RPSS perform authentication, coarse-grained authorization, and request routing to the target application server.


 

Related tasks

Select an authentication mechanism
Integrating third-party HTTP reverse proxy servers