Example: Customize a server-side JAAS authentication and login configuration

WAS supports plugging in a custom JAAS login module before or after the WAS system login module. However, WAS does not support the replacement of the WAS system login modules, which are used to create WSCredential and WSPrincipal in the Subject. By using a custom login module, you can either make additional authentication decisions or add information to the Subject to make additional, potentially finer-grained, authorization decisions inside a J2EE application.

WAS enables you to propagate information downstream that is added to the Subject by a custom login module. To determine which login configuration to use for plugging in your custom login modules, see the descriptions of the login configurations located in the System login configuration entry settings for JAAS article.

Note: Information added to the Subject from the custom login module is not propagated downstream in the current implementation.

Only the identity gets propagated. Using a custom login module, the identity can be used to generate similar data downstream.

WAS server-side authentication mechanism, LTPA, is implemented as the JAAS LoginModule. The LTPA login configuration is defined in the WebSphere Configuration API model within the cell-level security.xml XML file and within the wsjaas.conf properties file. There are two sets of JAAS login configuration defined in the WebSphere Configuration API model: the application login configuration and the system login configuration. LTPA is defined in the system login configuration.

WAS V5.1 enables you to customize the LTPA system configuration. A new LTPA_WEB login configuration exists in the WebSphere Configuration API model, which is used exclusively by the Web container. The LTPA login configuration is used by the EJB container. The LTPA_WEB login configuration contains the com.ibm.ws.security.web.AuthenLoginModule module and the LTPA login configuration contains the com.ibm.ws.security.server.lm.ltpaLoginModule module. The new AuthenLoginModule is an enhanced ltpaLoginModule that can process the HttpServletRequest object, the HttpServletResponse object, and the Web application name that are passed in using the CallbackHandler.

WAS V5.1 exposes the server-side login configuration so that you may customize the LTPA authentication process. Both the LTPA login configuration and the LTPA_WEB login configuration enable you to add a custom LoginModule both before and after the ltpaLoginModule and the AuthenLoginModule. For example, one might add a LoginModule to perform principal or credential mapping function either before or after the authentication. In the Web configuration, a custom LoginModule might perform principal mapping using a combination of authenticated user name, application name, and URL patterns. WAS does not allow you to rename nor remove the LTPA and LTPA_WEB login configurations.

WAS V5.1 and all prior version 5.0.x releases do not expose the system login configuration in the administration console. The WAS version 5.0.x releases do not support the modification of the system login configuration. In WAS V5.1, the system login configuration is not exposed in the administrative console. However, you can modify the system login configuration using the wsadmin scripting utility.

WAS supports the modification of the system login configuration through the administrative console and by using the wsadmin scripting utility. To configure the system login configuration using the administrative console, click...

Security | JAAS Configuration | System logins

Refer to the following code sample to configure a system login configuration using the wsadmin tool. The following sample JACL script adds a customLoginModule into the LTPA Web system login configuration:

Note: Lines 32, 33, and 34 in the following code sample were split onto two lines because of the width of the printed page.

1.	#########################################
2.	#
3.	# Open security.xml  
4.	#
5.	#########################################
6.	
7.	
8.	set sec [$AdminConfig getid /Cell:hillside/Security:/]
9.	
10.	
11.	#########################################
12.	#
13.	# Locate systemLoginConfig 
14.	#
15.	#########################################
16.	
17.	
18.	set slc [$AdminConfig showAttribute $sec systemLoginConfig]
19.	
20.	set entries [lindex [$AdminConfig showAttribute $slc entries] 0]
21.	
22.	
23.	#########################################
24.	#
25.	# Append a new LoginModule to LTPA_WEB 
26.	#
27.	#########################################
28.	
29.	foreach entry $entries {
30.	   set alias [$AdminConfig showAttribute $entry alias]
31.	   if {$alias == "LTPA_WEB"} {
32.	      set newJAASLoginModuleId [$AdminConfig create JAASLoginModule 
           $entry {{moduleClassName 
           "com.ibm.ws.security.common.auth.module.proxy.WSLoginModuleProxy"}}]
33.	      set newPropertyId [$AdminConfig create Property 
           $newJAASLoginModuleId {{name delegate}{value 
           "com.ABC.security.auth.CustomLoginModule"}}]
34.	      $AdminConfig modify $newJAASLoginModuleId 
           {{authenticationStrategy REQUIRED}}
35.	      break
36.	   }
37.	}
38.	
39.	
40.	#########################################
41.	#
42.	# save the change
43.	#
44.	#########################################
45.	
46.	$AdminConfig save
47.	

Note: The wsadmin scripting utility inserts a new object to the end of the list. To insert the custom LoginModule before the AuthenLoginModule, delete the AuthenLoginModule and then recreate it after inserting the custom LoginModule. Save the sample script into a file, sample.jacl, executing the sample script using the following command:

wsadmin -f sample.jacl

You can use the following sample JACL script to remove the current LTPA_WEB login configuration and all the LoginModules:

48.	#########################################
49.	#
50.	# Open security.xml  
51.	#
52.	#########################################
53.	
54.	
55.	set sec [$AdminConfig getid /Cell:hillside/Security:/]
56.	
57.	
58.	#########################################
59.	#
60.	# Locate systemLoginConfig 
61.	#
62.	#########################################
63.	
64.	
65.	set slc [$AdminConfig showAttribute $sec systemLoginConfig]
66.	
67.	set entries [lindex [$AdminConfig showAttribute $slc entries] 0]
68.	
69.	
70.	#########################################
71.	#
72.	# Remove the LTPA_WEB login configuration 
73.	#
74.	#########################################
75.	
76.	foreach entry $entries {
77.	   set alias [$AdminConfig showAttribute $entry alias]
78.	   if {$alias == "LTPA_WEB"} {
79.	      $AdminConfig remove $entry
80.	      break
81.	   }
82.	}
83.	
84.	
85.	#########################################
86.	#
87.	# save the change
88.	#
89.	#########################################
90.	
91.	$AdminConfig save

You can use the following sample JACL script to recover the original LTPA_WEB configuration:

Note: Lines 122, 124, and 126 in the following code sample were split onto two or more lines because of the width of the printed page. The two lines of code for line 122 are normally one continuous line. The three lines of code for line 124 are normally one continuous line. Also, the three lines of code for line 126 are normally one continuous line.

92.	#########################################
93.	#
94.	# Open security.xml  
95.	#
96.	#########################################
97.	
98.	
99.	set sec [$AdminConfig getid /Cell:hillside/Security:/]
100.	
101.	
102.	#########################################
103.	#
104.	# Locate systemLoginConfig 
105.	#
106.	#########################################
107.	
108.	
109.	set slc [$AdminConfig showAttribute $sec systemLoginConfig]
110.	
111.	set entries [lindex [$AdminConfig showAttribute $slc entries] 0]
112.	
113.	                                                              
114.	                                                                
115.	#########################################
116.	#
117.	# Recreate the LTPA_WEB login configuration 
118.	#
119.	#########################################
120.	
121.	
122.	set newJAASConfigurationEntryId [$AdminConfig create JAASConfigurationEntry 
     $slc {{alias LTPA_WEB}}]
123.	
124.	set newJAASLoginModuleId [$AdminConfig create JAASLoginModule 
     $newJAASConfigurationEntryId 
     {{moduleClassName 
     "com.ibm.ws.security.common.auth.module.proxy.WSLoginModuleProxy"}}]
125.	
126.	set newPropertyId [$AdminConfig create Property 
     $newJAASLoginModuleId {{name delegate}
     {value "com.ibm.ws.security.web.AuthenLoginModule"}}]
127.	
128.	$AdminConfig modify $newJAASLoginModuleId {{authenticationStrategy REQUIRED}}
129.	
130.	
131.	#########################################
132.	#
133.	# save the change
134.	#
135.	#########################################
136.	
137.	$AdminConfig save

The WAS V5.1 ltpaLoginModule and AuthenLoginModule use the shared state to save state information so that custom LoginModules can modify the information. The ltpaLoginModule initializes the callback array in the login() method using the following code. The callback array is created by ltpaLoginModule only if an array is not defined in the shared state area. In the following code sample, the error handling code was removed to make the sample concise. If you insert a custom LoginModule before the ltpaLoginModule, custom LoginModule might follow the same style to save the callback into the shared state.

Note: In the following code sample, several lines of code have been split onto two lines because of the width of the printed page. Each of these split lines are one continuous line.

138.	        Callback callbacks[] = null;
139.	        if (!sharedState.containsKey( 
                 com.ibm.wsspi.security.auth.callback.Constants.
                 CALLBACK_KEY)) {
140.	            callbacks = new Callback[3];
141.	            callbacks[0] = new NameCallback("Username: ");
142.	            callbacks[1] = new PasswordCallback("Password: ", false);
143.	            callbacks[2] = new com.ibm.websphere.security.auth.callback.
                 WSCredTokenCallbackImpl( "Credential Token: ");
144.	            try {
145.	                callbackHandler.handle(callbacks);
146.	            } catch (java.io.IOException e) {
147.	                . . .
148.	           } catch (UnsupportedCallbackException uce) {
149.	                . . .
150.	           }
151.	           sharedState.put( 
                com.ibm.wsspi.security.auth.callback.Constants.CALLBACK_KEY, 
                callbacks);
152.	        } else {
153.	            callbacks = (Callback []) 
                 sharedState.get( com.ibm.wsspi.security.auth.callback.
                 Constants.CALLBACK_KEY);
154.	        }

ltpaLoginModule and AuthenLoginModule generate both a WSPrincipal and a WSCredential object to represent the authenticated user identity and security credentials. The WSPrincipal and WSCredential objects also are saved in the shared state. A JAAS login uses a two-phase commit protocol. First, the login methods in login modules, which are configured in the login configuration, are called. Then, their commit methods are called. A custom LoginModule, which is inserted after the ltpaLoginModule and the AuthenLoginModule, can modify the WSPrincipal and WSCredential objects before they are committed. The WSCredential and WSPrincipal objects must exist in the Subject after the login is completed. Without these objects in the Subject, WAS run-time code rejects the Subject when it is used to make any security decisions.

AuthenLoginModule uses the following code to initialize the callback array:

Note: In the following code sample, several lines of code have been split onto two lines because of the width of the printed page. Each of these split lines are one continuous line.

155.	        Callback callbacks[] = null;
156.	        if (!sharedState.containsKey( 
                 com.ibm.wsspi.security.auth.callback.Constants.
                 CALLBACK_KEY)) {
157.	            callbacks = new Callback[6];
158.	            callbacks[0] = new NameCallback("Username: ");
159.	            callbacks[1] = new PasswordCallback("Password: ", false);
160.	            callbacks[2] = 
                 new com.ibm.websphere.security.auth.callback.WSCredTokenCallbackImpl( 
                 "Credential Token: ");			
161.	            callbacks[3] = 
                 new com.ibm.wsspi.security.auth.callback.WSServletRequestCallback( 
                 "HttpServletRequest: ");
162.	            callbacks[4] = 
                 new com.ibm.wsspi.security.auth.callback.WSServletResponseCallback( 
                 "HttpServletResponse: ");
163.	            callbacks[5] = 
                 new com.ibm.wsspi.security.auth.callback.WSAppContextCallback( 
                 "ApplicationContextCallback: ");
164.	            try {
165.	                callbackHandler.handle(callbacks);
166.	            } catch (java.io.IOException e) {
167.	              . . .
168.	            } catch (UnsupportedCallbackException uce {
169.	              . . .
170.	            }
171.	            sharedState.put( com.ibm.wsspi.security.auth.callback.
                 Constants.CALLBACK_KEY, callbacks);
172.	        } else {
173.	            callbacks = (Callback []) sharedState.get( 
                 com.ibm.wsspi.security.auth.callback.
                 Constants.CALLBACK_KEY);
174.	        }
 

Three more objects, which contain callback information for the login, are passed from the Web container to the AuthenLoginModule: a java.util.Map, a HttpServletRequest, and a HttpServletResponse object. These objects represent the Web application context. The WAS V5.1 application context, java.util.Map object, contains the application name and the error page URL. You can obtain the application context, java.util.Map object, by calling the getContext() method on the WSAppContextCallback object. The java.util.Map object is created with the following deployment descriptor information.

Note: In the following code sample, several lines of code have been split onto two lines because of the width of the printed page. Each of these split lines are one continuous line.

175.	       HashMap appContext = new HashMap(2);
176.	       appContext.put( 
            com.ibm.wsspi.security.auth.callback.Constants.WEB_APP_NAME, 
            web_application_name);
177.	       appContext.put( 
            com.ibm.wsspi.security.auth.callback.Constants.REDIRECT_URL, 
            errorPage);

The application name and the HttpServletRequest object might be read by the custom LoginModule to perform mapping functions. The error page of the form-based login might be modified by a custom LoginModule. In addition to the JAAS framework, WAS supports the Trust Association Interface (TAI).

Other credential types and information can be added to the caller Subject during the authentication process using a custom LoginModule. The third-party credentials in the caller Subject are managed by WAS as part of the security context. The caller Subject is bound to the thread of execution during the request processing. When a Web or EJB module is configured to use the caller identity, the user identity is propagated to the downstream service in an EJB request. WSCredential and any third-party credentials in the caller Subject are not propagated downstream. Instead, some of the information can be regenerated at the target server based on the propagated identity. Add third-party credentials to the caller Subject at the authentication stage. The caller Subject, which is returned from the WSSubject.getCallerSubject() method, is read-only and thus cannot be modified. For more information on the WSSubject, see Example: Getting the Caller Subject from the Thread.

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Programmatic login
Security attribute propagation

Example: Getting the Caller Subject from the Thread
System login configuration entry settings for JAAS

 

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