Configure a custom System Authorization Facility (SAF) mapping module for federated repositories

(zos)

Configure a custom System Authorization Facility (SAF) mapping module for federated repositories

We can configure the System Authorization Facility (SAF) mapping module to use federated repositories with the SAF user registry adapter for SAF authorization. The SAF mapping module maps the identity in the federated repository to a SAF identity.

As federated repositories can have a chain of user registries, such as, SAF, LDAP, or a file-based repository, the mapping module clearly distinguishes the SAF identity that must be used with SAF authorization. To enable SAF authorization for operating system registries or other registries, for example LDAP through federated repository, SAF identity mapping is required. This identity mapping sets the additional credential information needed for SAF.

We can customize Java Authentication and Authorization (JAAS) login configurations by writing a customized login mapping module. The WebSphere Application Server ltpaLoginModule module and the AuthenLoginModule module use the shared state variables provided in the mapping module to set the appropriate identity for SAF Authorization.

Avoid trouble:

We must compile SampleVMMSAFMappingModule if use this mapping module.
You do not need to configure a mapping module if you are using the SAF distributed identity mapping feature.

gotcha

In the following code example, the reliance is made on the availability of a Java EE identity to control the mapping to a SAF identity. This code uses the Constants.WSPRINCIPAL_KEY value in the shared state. The value is placed in the code by a WAS login module. We can insert a custom login module after the ltpaLoginModule module, and just before the MapPlatformSubject module. If we add a custom login module, use a callback array or other shared state values to obtain a value used to control the mapping to the z/OS user ID.

//This program may be used, run, copied, modified and //distributed without royalty for the purpose of developing, //using, marketing, or distributing.

package com.ibm.websphere.wim;

import com.ibm.websphere.security.auth.WSPrincipal;
import com.ibm.websphere.security.cred.WSCredential;
import com.ibm.websphere.wim.util.PrincipalUtil;
import com.ibm.websphere.wim.exception.WIMException;
import com.ibm.websphere.wim.ras.WIMLogger;
import com.ibm.wsspi.security.auth.callback.Constants;
import com.ibm.wsspi.security.token.AttributeNameConstants;

import java.lang.reflect.Array;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.security.auth.Subject;
import javax.security.auth.callback.CallbackHandler;

import javax.security.auth.login.LoginException;
import javax.security.auth.spi.LoginModule;

/**
 *
 * SampleVMMSAFMappingModule demonstrates a custom login module  * that maps the existing WSPrincipal from the shared state to a z/OS
 * user id for a Federated Repository.
 *
 *
 *
 * The following values will be set into the shared state if authentication  * succeeds.  If authentication fails, this login module will still indicate  * success, but no values are set into the shared state.
 *
 *   AttributeNameConstants.ZOS_USERID
 *   AttributeNameConstants.ZOS_AUDIT_STRING
 *   AttributeNameConstants.CALLER_PRINCIPAL_CLASS
 *
 * This login module does not use any callbacks, nor does it modify the Subject
 * in any way.
 *
 * @author IBM Corporation
 * @version 1.0
 * @since 1.0
 */
public class SampleVMMSAFMappingModule implements LoginModule
{
    public final static String CLASSNAME = SampleVMMSAFMappingModule.class.getName();
    private static final Logger trcLogger = WIMLogger.getTraceLogger(CLASSNAME);
    boolean logEnabled = trcLogger.isLoggable(Level.FINER);

    /*
     * Constant that represents the name of this mapping module.  Whenever this sample
     * code is used to create a class with a different name, this value should be changed.
     *
     * By default, this value is used as part of the sample audit token, and for debugging
     * purposes.
     */
    private final static String MAPPING_MODULE_NAME = "com.ibm.websphere.wim.SampleVMMSAFMappingModule";

    /*
     * Constant that represents the maximum length of the ZOS_USERID.  Current MVS naming
     * restrictions limit this to eight characters.
     *
     * When the option to useWSPrincipalName is chosen, the name from the WSPrincipal is     * shortened to this many characters.
     */
    private final static int MAXIMUM_NAME_LENGTH = 7;

    /*
     * Whether or not to use this module's default mapping behavior, which is     * to use the WSPrincipal name to generate the ZOS_USERID.  This depends on the    * value of the "useWSPrincipalName" option passed in from the LoginContext.
     */
    private boolean useWSPrincipalName = true;

    /*
     * Whether debugging is enabled for this Login Module.  This depends on the    * value of the "debug" option passed in from the LoginContext.
     */
    private boolean debugEnabled = false;

    /*
     * Stores the Subject passed from the LoginContext.
     */
    private Subject subject;

    /*
     * Stores the CallbackHandler passed from the LoginContext.
     */
    private CallbackHandler callbackHandler;

    /*
     * Stores the shared state Map passed from the LoginContext.
     */
    private Map sharedState;

    javax.security.auth.Subject runas_subject, caller_subject;
    /*
     * Stores the options Map passed from the LoginContext.
     */
    private Map options;

    /*
     * This value is used to store the success or failure of the login() method so      * that commit() and abort() can act differently in the two cases if so desired.
     */
    private boolean succeeded = false;


    /**
     * Construct an uninitialized mapping module object.
     */
    public SampleVMMSAFMappingModule()
    {
    }

    /**
     * Initialize this login module.
     *
     * This is called by the LoginContext after this login module is     * instantiated. The relevant information is passed from the LoginContext
     * to this login module. If the login module does not understand any of the data      * stored in the sharedState and options parameters, * they can be ignored.
     *
     * @param subject      *                The subject that this LoginContext is authenticating
     * @param callbackHandler
     *                A CallbackHandler for communicating with the end user      *                to gather login information (e.g., username and password).
     * @param sharedState
     *                The state shared with other configured login modules.
     * @param options      *                The options specified in the login configuration for this particular login module.
     */
    public void initialize(Subject newSubject, CallbackHandler newCallbackHandler, Map newSharedState, Map newOptions)
    {
        // obtain the value for debug before anything else so that tracing can be used within         // this method         if (newOptions.containsKey("debug"))
        {
            String debugEnabledString = (String) newOptions.get("debug");
            if (debugEnabledString != null && debugEnabledString.toLowerCase().equals("true"))
            {
                debugEnabled = true;
            }
        }

        if (debugEnabled)
        {
            debug("initialize() entry");
        }

        // this login module is not going to use any of these objects except for the sharedState, // but for consistency with most login modules, we will save a reference to all of them
        this.subject = newSubject;
        this.callbackHandler = newCallbackHandler;
        this.sharedState = newSharedState;
        this.options = newOptions;

        if (options.containsKey("useWSPrincipalName"))
        {
            String useWSPrincipalNameString = (String) options.get("useWSPrincipalName");
            if (useWSPrincipalNameString != null && useWSPrincipalNameString.toLowerCase().equals("false"))
            {
                useWSPrincipalName = false;
            }
        }

        if (debugEnabled)
        {
            debug(new Object[] { "initialize() exit", subject, callbackHandler, sharedState, options });
        }
    }

    /**
     * Method to map the WSPrincipal to a ZOS_USERID
     *
     * This method derives a ZOS_USERID and stores it into the Shared State for use by a later
     * Login Module.
     *
     * @return true if the authentication succeeded, or false      *         if this Login Module should be ignored
     * @exception LoginException
     *         if the authentication fails, which is impossible for this Login Module
     */
    public boolean login() throws LoginException
    {
        if (debugEnabled)
        {
            debug("login() entry");
        }

        if (sharedState.containsKey(AttributeNameConstants.ZOS_USERID))
        {
            // we don't want to override this value if, for whatever reason, another Login Module
            // has already placed it into the shared state, but we still consider this a success
            // because the exit criteria for this module has been met
            if (debugEnabled)
            {
                debug("ZOS_USERID already exists:  so no additional work is needed");
            }
            succeeded = true;
        }
        else if (!sharedState.containsKey(Constants.WSPRINCIPAL_KEY) ||
                !sharedState.containsKey(Constants.WSCREDENTIAL_KEY))
        {
            // if there isn't a Principal or Credential in the shared state, we can't do             // anything so we'll return false to inform the LoginContext to ignore this module             if (debugEnabled)
            {
                debug("Principal or Credential is unavailable:  skipping this Login Module");
            }
            succeeded = false;
        }
        else
        {
            if (debugEnabled)
            {
                debug("Principal and Credential are available:  continue with login");
            }

            String name = null;
            String audit = null;
            String principalClass = null;

            // extract the WSPrincipal and WSCredential from the shared state
            WSPrincipal principal = (WSPrincipal) sharedState.get(Constants.WSPRINCIPAL_KEY);
            WSCredential credential = (WSCredential) sharedState.get(Constants.WSCREDENTIAL_KEY);

            if (useWSPrincipalName)
            {
                // this sample mapping module provides a method to obtain the ZOS_USERID from the uniqueID obtained
                // from the WSPrincipal name if the property "useWSPrincipalName" is set to true
                if (debugEnabled)
                {
                    debug("Using name from WSPrincipal to obtain ZOS_USERID");
                }

                final String principalName=stripRealm(principal.getName());
                String realm = getRealm(credential);

                // for this example, a sample audit token will be created that combines the ZOS_USERID, // the realm, and the name of this mapping module                 //
                // a custom audit token can be created using any available data rather than using                 // this sample token 
                // A Subject may contain more than one Principal.  Specifies the               // class of the Principal to be returned when the Subject is asked for the               // Caller Principal.  If a custom Principal class has been placed into the               // Subject, that class name can be specified here.
                //
                // Two predefined values for the Caller Principal Class are provided:
                //
                // - AttributeNameConstants.ZOS_CALLER_PRINCIPAL_CLASS
                //   the z/OS Principal class                 //
                // - AttributeNameConstants.DEFAULT_CALLER_PRINCIPAL_CLASS
                //   the default Principal class                 principalClass = AttributeNameConstants.DEFAULT_CALLER_PRINCIPAL_CLASS;

                //name=doMapUser(principalName);
                name=doCustomMapUser(principalName);

                succeeded = true;
                audit = realm + "/" + name + " MappingModule:" + MAPPING_MODULE_NAME;
                }

                else
                {
                    if (debugEnabled)
                    {
                        debug("Using Custom logic to obtain ZOS_USERID");
                    }
                    // if the behavior provided by this mapping module to obtain the ZOS_USERID from the                   // WSPrincipal name is not enough, custom mapping logic can be provided here
                    //
                    // to use this custom mapping logic, the property "useWSPrincipalName" must be set                     // to false 
                    // name = ...custom logic                     // audit = ...custom logic                     // principalClass = ...custom logic 
                    // by default, no custom mapping is provided, so the success of this code path                     // is false; if custom mapping is provided, the following variable should be                     // modified to represent the success or failure of the custom mapping                     succeeded = false;
                }

                if (succeeded)
                {
                    // now that we have values for name, audit, and principalClass, we just need to set                     // them into the shared state
                    sharedState.put(AttributeNameConstants.ZOS_USERID, name);
                    sharedState.put(AttributeNameConstants.ZOS_AUDIT_STRING, audit);
                    sharedState.put(AttributeNameConstants.CALLER_PRINCIPAL_CLASS, principalClass);
                    if (debugEnabled)
                    {
                        debug(new Object[] { "Values have been stored into the shared state", name, audit, principalClass });
                    }
                }
            }

            if (debugEnabled)
            {
                debug("login() exit");
            }
            return succeeded;
        }

        /**
         * Method to commit the authentication result.
         *
         * This Login Module does not need to commit any data, so we will simply return.
         *
         * @return true if the original login succeeded, or false          *         if the original login failed
         * @exception LoginException
         *         if the commit fails, which cannot happen in this Login Module
         */
        public boolean commit() throws LoginException
        {
            if (debugEnabled)
            {
                debug("commit() entry");
            }

            // the return value of commit() is the same as the success of the original login             boolean returnVal = succeeded;

            cleanup();

            if (debugEnabled)
            {
                debug("commit() exit");
            }
            return returnVal;
        }

        /**
         * Method to abort the authentication process (Phase 2).
         *
         * No matter whether our original login succeeded or failed, this method cleans up
         * our state and returns.
         *
         * @return true if the original login succeeded, or false          *         if the original login failed
         * @exception LoginException
         *         if the abort fails, which cannot happen in this Login Module
         */
        public boolean abort() throws LoginException
        {
            if (debugEnabled)
            {
                debug("abort() entry");
            }

            // the return value of abort() is the same as the success of the original login             boolean returnVal = succeeded;

            cleanup();

            if (debugEnabled)
            {
                debug("abort() exit");
            }
            return returnVal;
        }

        /**
         * Method which logs out a Subject.
         *
         * Since our commit method did not modify the Subject, we don't have anything to          * logout or clean up and can just return true.
         *
         * @return true if the logout succeeded
         * @exception LoginException
         *         if the logout fails, which cannot happen in the Login Module
         */
        public boolean logout() throws LoginException
        {
            if (debugEnabled)
            {
                debug("logout() entry");
            }

            // our local variables were cleanup up during the commit, so no further cleanup is needed 
            if (debugEnabled)
            {
                debug("logout() exit");
            }

            // since there is nothing to logout, we always succeed
            return true;
        }

        /*
         * Cleans up our local variables; the only cleanup  required for          * this Login Module is to set our success variable back to false.
         */
        private void cleanup()
        {
            if (debugEnabled)
            {
                debug("cleanup() entry");
            }

            // there's nothing to cleanup, really, so just reset our success variable
            succeeded = false;

            if (debugEnabled)
            {
                debug("cleanup() exit");
            }
        }

        /*
         * Private method to print trace information.  This implementation uses System.out
         * to print trace information to standard output, but a custom tracing system can          * be implemented here as well.
         */
        private void debug(Object o)
        {
            System.out.println("Debug: " + MAPPING_MODULE_NAME);
            if (o != null)
            {
                if (o.getClass().isArray())
                {
                    int length = Array.getLength(o);
                    for (int i = 0; i < length; i++)
                    {
                        System.out.println("\t" + Array.get(o, i));
                    }
                }
                else
                {
                    System.out.println("\t" + o);
                }
            }
        }

        /*
         * Private method to obtain the realm name from the Credential and return it.  This         * keeps the exception handling involved with obtaining the realm name out of the main
         * login() logic.
         */
        private String getRealm(WSCredential credential)
        {
            if (debugEnabled)
            {
                debug("getRealm() entry");
            }

            String realm = null;

            try
            {
                realm = credential.getRealmName();

                if (debugEnabled)
                {
                    debug("Got realm='" + realm + "' from credential");
                }
            }
            catch (Exception e)
            {
                // getRealmName throws CredentialExpiredException and CredentialDestroyedException
                if (debugEnabled)
                {
                    //debug(new Object[] { "Caught exception in getRealm: ", e });
                }
                realm = "UNKNOWN_REALM";
            }

            if (debugEnabled)
            {
                debug("getRealm() exit");
            }
            return realm;
        }

        /*
         * Private method to generate the ZOS_USERID from the WSPrincipal name/uniqueName.
         */
        private String createSAFIdentityName(String name)
        {
            if (debugEnabled)
            {
                debug("createSAFIdentityName() entry "+ name);
            }

            name=stripRealm(name).toUpperCase();
            //Get the CN.if uniqueName of format "uid=test,o=com" strip to "test".
            if (name.indexOf("=") >= 0)
                name = name.substring((name.indexOf("=")+1),name.length());

            if (name.indexOf(",") > 0)
                name = name.substring(0,name.indexOf(","));

            //handle case where realm appended :<realmname>\\userid
            if(name.indexOf("\\")>0){
            name = name.substring((name.indexOf("\\")+1),name.length());
            }

            // shorten the name if its length exceeds the defined maximum             if (name.length() > MAXIMUM_NAME_LENGTH)
            {
                name = name.substring(0, MAXIMUM_NAME_LENGTH);

                if (debugEnabled)
                {
                    debug("WSPrincipal/uniqueName shortened to " + name);
                }
            }

            if (debugEnabled)
            {
                debug("createSAFIdentityName() exit");
            }
            return name; //return a SAF Idenity Name
        }
        /*
         * Private Helper method to Strip realm information if any.
         */
        private String stripRealm(String name){
            int index = name.indexOf("/") + 1; // index of the first character after the first /
            if (index >= name.length())
            {
                // this block handles the case where the first / is the last character in the String, // it really shouldn't happen, but if it does we can just strip it off
                name = name.substring(0, index - 1);

                if (debugEnabled)
                {
                    debug("Stripping trailing / from WSPrincipal name");
                }
            }
            else
            {
                name = name.substring(index);
            }

            return name;

        }


        /**
         * Private helper method to deduce the z/OS ID to be mapped.
         * We can use this when to map RACF users & other repository users in specific ways.
         * This uses a Federated Repository util method, isRACFUser to identify if the user is from RACF registry.
         */
        private String  doCustomMapUser(String principalName){
            boolean isRACFUser=true;
            String  mapID=null;
            try{
            isRACFUser=PrincipalUtil.isRACFUser(principalName);
            }
            catch(WIMException we){
               debug("Exception happened while checking isRACFuser"+we);
               //Handle it as per need.
            }
            mapID=isRACFUser==true?createSAFIdentityName(principalName):doMapUser(principalName);

            return mapID;
        }

        /**
         * Private helper method to deduce the z/OS ID to be mapped.
         * We can use this directly to map z/OS ID irrespective of RACF/Non-RACF users.
         *
         */
        private String  doMapUser(String principalName){
            //If loginUser belongs to other registry like LDAP make sure an MVS user exists to match the derived name.
            //Or just map to any existing RACF user as in the commented line below.
            // name="USER237";
            //if user exists in RACF then Map that user.
            String uniqueName=null;
            String mapID=null;
            try {
                javax.naming.InitialContext ctx = new javax.naming.InitialContext();
                // Retrieves the local UserRegistry object.
                final com.ibm.websphere.security.UserRegistry reg = (com.ibm.websphere.security.UserRegistry) ctx.lookup("UserRegistry");
                // Retrieves the registry uniqueName based on the principalName
                uniqueName = reg.getUniqueUserId(principalName);
            } catch ( Exception e ) {
                debug("Exception thrown while getting uniqueID: "+e);
            }
            mapID=createSAFIdentityName(uniqueName);

            return mapID;
        }
    }

The sample mapping module creates a mapping between the identity of the user registry for the federated repository and the z/OS identity. The identity for the user registry is used as the z/OS user ID. If we require a different mapping, we can customize this module, which is shown in the else clause as part of the previous code sample, to perform the mapping.

A federated repositories utility method, which is called PrincipalUtil.isRACFUser, is used to identify whether the user is from RACF registry. This method returns true if the user is a RACF user. Use this method only if the current user registry is configured under federated repositories.

Compile the Java code.
1. Make sure the code is trusted and treated with the same care as an Authorized Program Facility (APF)-authorized module. The default Java Authorization and Authentication Service (JAAS) System login configuration is accessed from the z/OS controller.
2. Make sure the class path setting includes the correct JAR files: We can use one of the following set of JAR files:
  - WebSphere_Application_Client/plugins/org.eclipse.emf.commonj.sdo.jar, WebSphere_Application_Client/plugins/com.ibm.ws.emf.jar, and WebSphere_Application_Client/plugins/com.ibm.ws.runtime.client.jar
  - WAS_HOME/plugins/org.eclipse.emf.commonj.sdo.jar, WAS_HOME/plugins/com.ibm.ws.runtime.wim.base.jar, and WAS_HOME/plugins/com.ibm.ws.runtime.jar
Install the class into the classes directory of WAS and the deployment managers if specified a mapping class other than the default supplied by IBM .
Place the JAR file into the WAS_HOME/classes directory for each node in the cell including the deployment manager node in a WAS Network Deployment cell.
Restart WebSphere Application Server for the changes to take effect.
Enable logging for SampleSAFMappingModule by specifying a custom property for this module:
1. On the WAS console, click Security > Global Security > Authentication, expand Java Authentication and Authorization Service.
2. Click System logins.
3. Click login_module_name.
4. Under JAAS login modules, click com.ibm.websphere.wim.SampleVMMSAFMappingModule.
5. Under Custom properties, click New.
6. In the Name field, enter debug, and in the value field, enter true.
7. Click Apply, and then click Save.

Related concepts

Distributed identity mapping using SAF

Configure a custom System Authorization Facility (SAF) mapping module for federated repositories

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