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/*
 * Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * questions.
 */

package javax.security.auth.login;

import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Map;
import java.util.HashMap;
import java.text.MessageFormat;
import javax.security.auth.Subject;
import javax.security.auth.AuthPermission;
import javax.security.auth.callback.*;
import javax.security.auth.spi.LoginModule;
import java.security.AccessControlContext;
import java.util.ServiceLoader;

import sun.security.util.PendingException;
import sun.security.util.ResourcesMgr;


 The LoginContext class describes the basic methods used to authenticate Subjects and provides a way to develop an application independent of the underlying authentication technology. A Configuration specifies the authentication technology, or LoginModule, to be used with a particular application. Different LoginModules can be plugged in under an application without requiring any modifications to the application itself. 
 In addition to supporting pluggable authentication, this class
also supports the notion of stacked authentication.
Applications may be configured to use more than one
LoginModule.  For example, one could
configure both a Kerberos LoginModule and a smart card
LoginModule under an application.

 A typical caller instantiates a LoginContext with
a name and a CallbackHandler. LoginContext uses the name as the index into a Configuration to determine which LoginModules should be used, and which ones must succeed in order for the overall authentication to succeed. The CallbackHandler is passed to the underlying LoginModules so they may communicate and interact with users (prompting for a username and password via a graphical user interface, for example). 
 Once the caller has instantiated a LoginContext, it invokes the login method to authenticate a Subject. The login method invokes the configured modules to perform their respective types of authentication (username/password, smart card pin verification, etc.). Note that the LoginModules will not attempt authentication retries nor introduce delays if the authentication fails. Such tasks belong to the LoginContext caller. 
 If the login method returns without throwing an exception, then the overall authentication succeeded. The caller can then retrieve the newly authenticated Subject by invoking the getSubject method. Principals and Credentials associated with the Subject may be retrieved by invoking the Subject's respective getPrincipals, getPublicCredentials, and getPrivateCredentials methods. 
 To logout the Subject, the caller calls the logout method. As with the login method, this logout method invokes the logout method for the configured modules. 
 A LoginContext should not be used to authenticate
more than one Subject.  A separate LoginContext
should be used to authenticate each different Subject.

 The following documentation applies to all LoginContext constructors:

    

  1.  Subject 
      

    •  If the constructor has a Subject
input parameter, the LoginContext uses the caller-specified
Subject object.

    •  If the caller specifies a null Subject and a null value is permitted, the LoginContext instantiates a new Subject. 
    •  If the constructor does not have a Subject
input parameter, the LoginContext instantiates a new Subject.

    

  2.  Configuration 
      

    •  If the constructor has a Configuration
input parameter and the caller specifies a non-null Configuration,
the LoginContext uses the caller-specified Configuration.

      
If the constructor does not have a Configuration input parameter, or if the caller specifies a null Configuration object, the constructor uses the following call to get the installed Configuration: 
           config = Configuration.getConfiguration();

      
For both cases,
the name argument given to the constructor is passed to the Configuration.getAppConfigurationEntry method. If the Configuration has no entries for the specified name, then the LoginContext calls getAppConfigurationEntry with the name, "other"
(the default entry name).  If there is no entry for "other", then a LoginException is thrown. 
    •  When LoginContext uses the installed Configuration, the caller
requires the createLoginContext.name and possibly createLoginContext.other AuthPermissions. Furthermore, the LoginContext will invoke configured modules from within an AccessController.doPrivileged call so that modules that perform security-sensitive tasks (such as connecting to remote hosts, and updating the Subject) will require the respective permissions, but the callers of the LoginContext will not require those permissions. 
    •  When LoginContext uses a caller-specified Configuration, the caller does not require any createLoginContext AuthPermission. The LoginContext saves the AccessControlContext for the caller, and invokes the configured modules from within an AccessController.doPrivileged call constrained by that context. This means the caller context (stored when the LoginContext was created) must have sufficient permissions to perform any security-sensitive tasks that the modules may perform. 
    

  3.  CallbackHandler 
      

    •  If the constructor has a CallbackHandler
input parameter, the LoginContext uses the caller-specified
CallbackHandler object.

    •  If the constructor does not have a CallbackHandler input parameter, or if the caller specifies a null CallbackHandler object (and a null value is permitted), the LoginContext queries the auth.login.defaultCallbackHandler security property for the fully qualified class name of a default handler implementation. If the security property is not set, then the underlying modules will not have a CallbackHandler for use in communicating with users. The caller thus assumes that the configured modules have alternative means for authenticating the user. 
    •  When the LoginContext uses the installed Configuration (instead of a caller-specified Configuration, see above), then this LoginContext must wrap any caller-specified or default CallbackHandler implementation in a new CallbackHandler implementation whose handle method implementation invokes the specified CallbackHandler's handle method in a java.security.AccessController.doPrivileged call constrained by the caller's current AccessControlContext. 
    



See Also:
Since:1.4
/**
 * <p> The {@code LoginContext} class describes the basic methods used
 * to authenticate Subjects and provides a way to develop an
 * application independent of the underlying authentication technology.
 * A {@code Configuration} specifies the authentication technology, or
 * {@code LoginModule}, to be used with a particular application.
 * Different LoginModules can be plugged in under an application
 * without requiring any modifications to the application itself.
 *
 * <p> In addition to supporting <i>pluggable</i> authentication, this class
 * also supports the notion of <i>stacked</i> authentication.
 * Applications may be configured to use more than one
 * LoginModule.  For example, one could
 * configure both a Kerberos LoginModule and a smart card
 * LoginModule under an application.
 *
 * <p> A typical caller instantiates a LoginContext with
 * a <i>name</i> and a {@code CallbackHandler}.
 * LoginContext uses the <i>name</i> as the index into a
 * Configuration to determine which LoginModules should be used,
 * and which ones must succeed in order for the overall authentication to
 * succeed.  The {@code CallbackHandler} is passed to the underlying
 * LoginModules so they may communicate and interact with users
 * (prompting for a username and password via a graphical user interface,
 * for example).
 *
 * <p> Once the caller has instantiated a LoginContext,
 * it invokes the {@code login} method to authenticate
 * a {@code Subject}.  The {@code login} method invokes
 * the configured modules to perform their respective types of authentication
 * (username/password, smart card pin verification, etc.).
 * Note that the LoginModules will not attempt authentication retries nor
 * introduce delays if the authentication fails.
 * Such tasks belong to the LoginContext caller.
 *
 * <p> If the {@code login} method returns without
 * throwing an exception, then the overall authentication succeeded.
 * The caller can then retrieve
 * the newly authenticated Subject by invoking the
 * {@code getSubject} method.  Principals and Credentials associated
 * with the Subject may be retrieved by invoking the Subject's
 * respective {@code getPrincipals}, {@code getPublicCredentials},
 * and {@code getPrivateCredentials} methods.
 *
 * <p> To logout the Subject, the caller calls
 * the {@code logout} method.  As with the {@code login}
 * method, this {@code logout} method invokes the {@code logout}
 * method for the configured modules.
 *
 * <p> A LoginContext should not be used to authenticate
 * more than one Subject.  A separate LoginContext
 * should be used to authenticate each different Subject.
 *
 * <p> The following documentation applies to all LoginContext constructors:
 * <ol>
 *
 * <li> {@code Subject}
 * <ul>
 * <li> If the constructor has a Subject
 * input parameter, the LoginContext uses the caller-specified
 * Subject object.
 *
 * <li> If the caller specifies a {@code null} Subject
 * and a {@code null} value is permitted,
 * the LoginContext instantiates a new Subject.
 *
 * <li> If the constructor does <b>not</b> have a Subject
 * input parameter, the LoginContext instantiates a new Subject.
 * </ul>
 *
 * <li> {@code Configuration}
 * <ul>
 * <li> If the constructor has a Configuration
 * input parameter and the caller specifies a non-null Configuration,
 * the LoginContext uses the caller-specified Configuration.
 * <p>
 * If the constructor does <b>not</b> have a Configuration
 * input parameter, or if the caller specifies a {@code null}
 * Configuration object, the constructor uses the following call to
 * get the installed Configuration:
 * <pre>
 *      config = Configuration.getConfiguration();
 * </pre>
 * For both cases,
 * the <i>name</i> argument given to the constructor is passed to the
 * {@code Configuration.getAppConfigurationEntry} method.
 * If the Configuration has no entries for the specified <i>name</i>,
 * then the {@code LoginContext} calls
 * {@code getAppConfigurationEntry} with the name, "<i>other</i>"
 * (the default entry name).  If there is no entry for "<i>other</i>",
 * then a {@code LoginException} is thrown.
 *
 * <li> When LoginContext uses the installed Configuration, the caller
 * requires the createLoginContext.<em>name</em> and possibly
 * createLoginContext.other AuthPermissions. Furthermore, the
 * LoginContext will invoke configured modules from within an
 * {@code AccessController.doPrivileged} call so that modules that
 * perform security-sensitive tasks (such as connecting to remote hosts,
 * and updating the Subject) will require the respective permissions, but
 * the callers of the LoginContext will not require those permissions.
 *
 * <li> When LoginContext uses a caller-specified Configuration, the caller
 * does not require any createLoginContext AuthPermission.  The LoginContext
 * saves the {@code AccessControlContext} for the caller,
 * and invokes the configured modules from within an
 * {@code AccessController.doPrivileged} call constrained by that context.
 * This means the caller context (stored when the LoginContext was created)
 * must have sufficient permissions to perform any security-sensitive tasks
 * that the modules may perform.
 * </ul>
 *
 * <li> {@code CallbackHandler}
 * <ul>
 * <li> If the constructor has a CallbackHandler
 * input parameter, the LoginContext uses the caller-specified
 * CallbackHandler object.
 *
 * <li> If the constructor does <b>not</b> have a CallbackHandler
 * input parameter, or if the caller specifies a {@code null}
 * CallbackHandler object (and a {@code null} value is permitted),
 * the LoginContext queries the
 * {@code auth.login.defaultCallbackHandler} security property for the
 * fully qualified class name of a default handler
 * implementation. If the security property is not set,
 * then the underlying modules will not have a
 * CallbackHandler for use in communicating
 * with users.  The caller thus assumes that the configured
 * modules have alternative means for authenticating the user.
 *
 *
 * <li> When the LoginContext uses the installed Configuration (instead of
 * a caller-specified Configuration, see above),
 * then this LoginContext must wrap any
 * caller-specified or default CallbackHandler implementation
 * in a new CallbackHandler implementation
 * whose {@code handle} method implementation invokes the
 * specified CallbackHandler's {@code handle} method in a
 * {@code java.security.AccessController.doPrivileged} call
 * constrained by the caller's current {@code AccessControlContext}.
 * </ul>
 * </ol>
 *
 * @since 1.4
 * @see java.security.Security
 * @see javax.security.auth.AuthPermission
 * @see javax.security.auth.Subject
 * @see javax.security.auth.callback.CallbackHandler
 * @see javax.security.auth.login.Configuration
 * @see javax.security.auth.spi.LoginModule
 * @see java.security.Security security properties
 */
public class LoginContext {

    private static final String LOGIN_METHOD            = "login";
    private static final String COMMIT_METHOD           = "commit";
    private static final String ABORT_METHOD            = "abort";
    private static final String LOGOUT_METHOD           = "logout";
    private static final String OTHER                   = "other";
    private static final String DEFAULT_HANDLER         =
                                "auth.login.defaultCallbackHandler";
    private Subject subject = null;
    private boolean subjectProvided = false;
    private boolean loginSucceeded = false;
    private CallbackHandler callbackHandler;
    private Map<String,?> state = new HashMap<String,Object>();

    private Configuration config;
    private AccessControlContext creatorAcc = null;  // customized config only
    private ModuleInfo[] moduleStack;
    private ClassLoader contextClassLoader = null;

    // state saved in the event a user-specified asynchronous exception
    // was specified and thrown

    private int moduleIndex = 0;
    private LoginException firstError = null;
    private LoginException firstRequiredError = null;
    private boolean success = false;

    private static final sun.security.util.Debug debug =
        sun.security.util.Debug.getInstance("logincontext", "\t[LoginContext]");

    private void init(String name) throws LoginException {

        SecurityManager sm = System.getSecurityManager();
        if (sm != null && creatorAcc == null) {
            sm.checkPermission(new AuthPermission
                                ("createLoginContext." + name));
        }

        if (name == null)
            throw new LoginException
                (ResourcesMgr.getString("Invalid.null.input.name"));

        // get the Configuration
        if (config == null) {
            config = java.security.AccessController.doPrivileged
                (new java.security.PrivilegedAction<Configuration>() {
                public Configuration run() {
                    return Configuration.getConfiguration();
                }
            });
        }

        // get the LoginModules configured for this application
        AppConfigurationEntry[] entries = config.getAppConfigurationEntry(name);
        if (entries == null) {

            if (sm != null && creatorAcc == null) {
                sm.checkPermission(new AuthPermission
                                ("createLoginContext." + OTHER));
            }

            entries = config.getAppConfigurationEntry(OTHER);
            if (entries == null) {
                MessageFormat form = new MessageFormat(ResourcesMgr.getString
                        ("No.LoginModules.configured.for.name"));
                Object[] source = {name};
                throw new LoginException(form.format(source));
            }
        }
        moduleStack = new ModuleInfo[entries.length];
        for (int i = 0; i < entries.length; i++) {
            // clone returned array
            moduleStack[i] = new ModuleInfo
                                (new AppConfigurationEntry
                                        (entries[i].getLoginModuleName(),
                                        entries[i].getControlFlag(),
                                        entries[i].getOptions()),
                                null);
        }

        contextClassLoader = java.security.AccessController.doPrivileged
                (new java.security.PrivilegedAction<ClassLoader>() {
                public ClassLoader run() {
                    ClassLoader loader =
                            Thread.currentThread().getContextClassLoader();
                    if (loader == null) {
                        // Don't use bootstrap class loader directly to ensure
                        // proper package access control!
                        loader = ClassLoader.getSystemClassLoader();
                    }

                    return loader;
                }
        });
    }

    private void loadDefaultCallbackHandler() throws LoginException {

        // get the default handler class
        try {

            final ClassLoader finalLoader = contextClassLoader;

            this.callbackHandler = java.security.AccessController.doPrivileged(
                new java.security.PrivilegedExceptionAction<CallbackHandler>() {
                public CallbackHandler run() throws Exception {
                    String defaultHandler = java.security.Security.getProperty
                        (DEFAULT_HANDLER);
                    if (defaultHandler == null || defaultHandler.length() == 0)
                        return null;
                    Class<? extends CallbackHandler> c = Class.forName(
                            defaultHandler, true,
                            finalLoader).asSubclass(CallbackHandler.class);
                    @SuppressWarnings("deprecation")
                    CallbackHandler result = c.newInstance();
                    return result;
                }
            });
        } catch (java.security.PrivilegedActionException pae) {
            throw new LoginException(pae.getException().toString());
        }

        // secure it with the caller's ACC
        if (this.callbackHandler != null && creatorAcc == null) {
            this.callbackHandler = new SecureCallbackHandler
                                (java.security.AccessController.getContext(),
                                this.callbackHandler);
        }
    }

    
Instantiate a new LoginContext object with a name. 
Params:
  • name – the name used as the index into the Configuration.
Throws:
  • LoginException – if the caller-specified name does not appear in the Configuration and there is no Configuration entry for "other", or if the auth.login.defaultCallbackHandler security property was set, but the implementation class could not be loaded.
  • SecurityException – if a SecurityManager is set and
         the caller does not have
         AuthPermission("createLoginContext.name"), or if a configuration entry for name does not exist and the caller does not additionally have AuthPermission("createLoginContext.other")
/**
     * Instantiate a new {@code LoginContext} object with a name.
     *
     * @param name the name used as the index into the
     *          {@code Configuration}.
     *
     * @exception LoginException if the caller-specified {@code name}
     *          does not appear in the {@code Configuration}
     *          and there is no {@code Configuration} entry
     *          for "{@code other}", or if the
     *          {@code auth.login.defaultCallbackHandler}
     *          security property was set, but the implementation
     *          class could not be loaded.
     *
     * @exception SecurityException if a SecurityManager is set and
     *          the caller does not have
     *          AuthPermission("createLoginContext.<i>name</i>"),
     *          or if a configuration entry for {@code name} does not exist and
     *          the caller does not additionally have
     *          AuthPermission("createLoginContext.other")
     */
    public LoginContext(String name) throws LoginException {
        init(name);
        loadDefaultCallbackHandler();
    }

    
Instantiate a new LoginContext object with a name and a Subject object. 
Params:
  • name – the name used as the index into the Configuration.
  • subject – the Subject to authenticate.
Throws:
  • LoginException – if the caller-specified name does not appear in the Configuration and there is no Configuration entry for "other", if the caller-specified subject is null, or if the auth.login.defaultCallbackHandler
         security property was set, but the implementation
         class could not be loaded.
  • SecurityException – if a SecurityManager is set and
         the caller does not have
         AuthPermission("createLoginContext.name"),
         or if a configuration entry for name does not exist and
         the caller does not additionally have
         AuthPermission("createLoginContext.other")
/**
     * Instantiate a new {@code LoginContext} object with a name
     * and a {@code Subject} object.
     *
     * @param name the name used as the index into the
     *          {@code Configuration}.
     *
     * @param subject the {@code Subject} to authenticate.
     *
     * @exception LoginException if the caller-specified {@code name}
     *          does not appear in the {@code Configuration}
     *          and there is no {@code Configuration} entry
     *          for "<i>other</i>", if the caller-specified {@code subject}
     *          is {@code null}, or if the
     *          <i>auth.login.defaultCallbackHandler</i>
     *          security property was set, but the implementation
     *          class could not be loaded.
     *
     * @exception SecurityException if a SecurityManager is set and
     *          the caller does not have
     *          AuthPermission("createLoginContext.<i>name</i>"),
     *          or if a configuration entry for <i>name</i> does not exist and
     *          the caller does not additionally have
     *          AuthPermission("createLoginContext.other")
     */
    public LoginContext(String name, Subject subject)
    throws LoginException {
        init(name);
        if (subject == null)
            throw new LoginException
                (ResourcesMgr.getString("invalid.null.Subject.provided"));
        this.subject = subject;
        subjectProvided = true;
        loadDefaultCallbackHandler();
    }

    
Instantiate a new LoginContext object with a name and a CallbackHandler object. 
Params:
  • name – the name used as the index into the Configuration.
  • callbackHandler – the CallbackHandler object used by LoginModules to communicate with the user.
Throws:
  • LoginException – if the caller-specified name does not appear in the Configuration and there is no Configuration entry for "other", or if the caller-specified callbackHandler is null.
  • SecurityException – if a SecurityManager is set and
         the caller does not have
         AuthPermission("createLoginContext.name"),
         or if a configuration entry for name does not exist and
         the caller does not additionally have
         AuthPermission("createLoginContext.other")
/**
     * Instantiate a new {@code LoginContext} object with a name
     * and a {@code CallbackHandler} object.
     *
     * @param name the name used as the index into the
     *          {@code Configuration}.
     *
     * @param callbackHandler the {@code CallbackHandler} object used by
     *          LoginModules to communicate with the user.
     *
     * @exception LoginException if the caller-specified {@code name}
     *          does not appear in the {@code Configuration}
     *          and there is no {@code Configuration} entry
     *          for "{@code other}", or if the caller-specified
     *          {@code callbackHandler} is {@code null}.
     *
     * @exception SecurityException if a SecurityManager is set and
     *          the caller does not have
     *          AuthPermission("createLoginContext.<i>name</i>"),
     *          or if a configuration entry for <i>name</i> does not exist and
     *          the caller does not additionally have
     *          AuthPermission("createLoginContext.other")
     */
    public LoginContext(String name, CallbackHandler callbackHandler)
    throws LoginException {
        init(name);
        if (callbackHandler == null)
            throw new LoginException(ResourcesMgr.getString
                                ("invalid.null.CallbackHandler.provided"));
        this.callbackHandler = new SecureCallbackHandler
                                (java.security.AccessController.getContext(),
                                callbackHandler);
    }

    
Instantiate a new LoginContext object with a name, a Subject to be authenticated, and a CallbackHandler object. 
Params:
  • name – the name used as the index into the Configuration.
  • subject – the Subject to authenticate.
  • callbackHandler – the CallbackHandler object used by LoginModules to communicate with the user.
Throws:
  • LoginException – if the caller-specified name does not appear in the Configuration and there is no Configuration entry for "other", or if the caller-specified subject is null, or if the caller-specified callbackHandler is null.
  • SecurityException – if a SecurityManager is set and
         the caller does not have
         AuthPermission("createLoginContext.name"),
         or if a configuration entry for name does not exist and
         the caller does not additionally have
         AuthPermission("createLoginContext.other")
/**
     * Instantiate a new {@code LoginContext} object with a name,
     * a {@code Subject} to be authenticated, and a
     * {@code CallbackHandler} object.
     *
     * @param name the name used as the index into the
     *          {@code Configuration}.
     *
     * @param subject the {@code Subject} to authenticate.
     *
     * @param callbackHandler the {@code CallbackHandler} object used by
     *          LoginModules to communicate with the user.
     *
     * @exception LoginException if the caller-specified {@code name}
     *          does not appear in the {@code Configuration}
     *          and there is no {@code Configuration} entry
     *          for "<i>other</i>", or if the caller-specified
     *          {@code subject} is {@code null},
     *          or if the caller-specified
     *          {@code callbackHandler} is {@code null}.
     *
     * @exception SecurityException if a SecurityManager is set and
     *          the caller does not have
     *          AuthPermission("createLoginContext.<i>name</i>"),
     *          or if a configuration entry for <i>name</i> does not exist and
     *          the caller does not additionally have
     *          AuthPermission("createLoginContext.other")
     */
    public LoginContext(String name, Subject subject,
                        CallbackHandler callbackHandler) throws LoginException {
        this(name, subject);
        if (callbackHandler == null)
            throw new LoginException(ResourcesMgr.getString
                                ("invalid.null.CallbackHandler.provided"));
        this.callbackHandler = new SecureCallbackHandler
                                (java.security.AccessController.getContext(),
                                callbackHandler);
    }

    
Instantiate a new LoginContext object with a name, a Subject to be authenticated, a CallbackHandler object, and a login Configuration. 
Params:
  • name – the name used as the index into the caller-specified Configuration.
  • subject – the Subject to authenticate, or null.
  • callbackHandler – the CallbackHandler object used by LoginModules to communicate with the user, or null.
  • config – the Configuration that lists the login modules to be called to perform the authentication, or null.
Throws:
  • LoginException – if the caller-specified name does not appear in the Configuration and there is no Configuration entry for "other".
  • SecurityException – if a SecurityManager is set,
         config is null, and either the caller does not have AuthPermission("createLoginContext.name"),
         or if a configuration entry for name does not exist and
         the caller does not additionally have
         AuthPermission("createLoginContext.other")
Since:1.5
/**
     * Instantiate a new {@code LoginContext} object with a name,
     * a {@code Subject} to be authenticated,
     * a {@code CallbackHandler} object, and a login {@code Configuration}.
     *
     * @param name the name used as the index into the caller-specified
     *          {@code Configuration}.
     *
     * @param subject the {@code Subject} to authenticate,
     *          or {@code null}.
     *
     * @param callbackHandler the {@code CallbackHandler} object used by
     *          LoginModules to communicate with the user, or {@code null}.
     *
     * @param config the {@code Configuration} that lists the
     *          login modules to be called to perform the authentication,
     *          or {@code null}.
     *
     * @exception LoginException if the caller-specified {@code name}
     *          does not appear in the {@code Configuration}
     *          and there is no {@code Configuration} entry
     *          for "<i>other</i>".
     *
     * @exception SecurityException if a SecurityManager is set,
     *          <i>config</i> is {@code null},
     *          and either the caller does not have
     *          AuthPermission("createLoginContext.<i>name</i>"),
     *          or if a configuration entry for <i>name</i> does not exist and
     *          the caller does not additionally have
     *          AuthPermission("createLoginContext.other")
     *
     * @since 1.5
     */
    public LoginContext(String name, Subject subject,
                        CallbackHandler callbackHandler,
                        Configuration config) throws LoginException {
        this.config = config;
        if (config != null) {
            creatorAcc = java.security.AccessController.getContext();
        }

        init(name);
        if (subject != null) {
            this.subject = subject;
            subjectProvided = true;
        }
        if (callbackHandler == null) {
            loadDefaultCallbackHandler();
        } else if (creatorAcc == null) {
            this.callbackHandler = new SecureCallbackHandler
                                (java.security.AccessController.getContext(),
                                callbackHandler);
        } else {
            this.callbackHandler = callbackHandler;
        }
    }

    
Perform the authentication.

 This method invokes the login method for each LoginModule configured for the name specified to the LoginContext constructor, as determined by the login Configuration. Each LoginModule then performs its respective type of authentication (username/password, smart card pin verification, etc.). 
 This method completes a 2-phase authentication process by calling each configured LoginModule's commit method if the overall authentication succeeded (the relevant REQUIRED, REQUISITE, SUFFICIENT, and OPTIONAL LoginModules succeeded), or by calling each configured LoginModule's abort method if the overall authentication failed. If authentication succeeded, each successful LoginModule's commit method associates the relevant Principals and Credentials with the Subject. If authentication failed, each LoginModule's abort method removes/destroys any previously stored state. 
 If the commit phase of the authentication process fails, then the overall authentication fails and this method invokes the abort method for each configured LoginModule. 
 If the abort phase fails for any reason, then this method propagates the original exception thrown either during the login phase or the commit phase. In either case, the overall authentication fails. 
 In the case where multiple LoginModules fail, this method propagates the exception raised by the first LoginModule which failed. 
 Note that if this method enters the abort phase (either the login or commit phase failed), this method invokes all LoginModules configured for the application regardless of their respective Configuration flag parameters. Essentially this means that Requisite and Sufficient semantics are ignored during the abort phase. This guarantees that proper cleanup and state restoration can take place. 
Throws:
/**
     * Perform the authentication.
     *
     * <p> This method invokes the {@code login} method for each
     * LoginModule configured for the <i>name</i> specified to the
     * {@code LoginContext} constructor, as determined by the login
     * {@code Configuration}.  Each {@code LoginModule}
     * then performs its respective type of authentication
     * (username/password, smart card pin verification, etc.).
     *
     * <p> This method completes a 2-phase authentication process by
     * calling each configured LoginModule's {@code commit} method
     * if the overall authentication succeeded (the relevant REQUIRED,
     * REQUISITE, SUFFICIENT, and OPTIONAL LoginModules succeeded),
     * or by calling each configured LoginModule's {@code abort} method
     * if the overall authentication failed.  If authentication succeeded,
     * each successful LoginModule's {@code commit} method associates
     * the relevant Principals and Credentials with the {@code Subject}.
     * If authentication failed, each LoginModule's {@code abort} method
     * removes/destroys any previously stored state.
     *
     * <p> If the {@code commit} phase of the authentication process
     * fails, then the overall authentication fails and this method
     * invokes the {@code abort} method for each configured
     * {@code LoginModule}.
     *
     * <p> If the {@code abort} phase
     * fails for any reason, then this method propagates the
     * original exception thrown either during the {@code login} phase
     * or the {@code commit} phase.  In either case, the overall
     * authentication fails.
     *
     * <p> In the case where multiple LoginModules fail,
     * this method propagates the exception raised by the first
     * {@code LoginModule} which failed.
     *
     * <p> Note that if this method enters the {@code abort} phase
     * (either the {@code login} or {@code commit} phase failed),
     * this method invokes all LoginModules configured for the
     * application regardless of their respective {@code Configuration}
     * flag parameters.  Essentially this means that {@code Requisite}
     * and {@code Sufficient} semantics are ignored during the
     * {@code abort} phase.  This guarantees that proper cleanup
     * and state restoration can take place.
     *
     * @exception LoginException if the authentication fails.
     */
    public void login() throws LoginException {

        loginSucceeded = false;

        if (subject == null) {
            subject = new Subject();
        }

        try {
            // module invoked in doPrivileged
            invokePriv(LOGIN_METHOD);
            invokePriv(COMMIT_METHOD);
            loginSucceeded = true;
        } catch (LoginException le) {
            try {
                invokePriv(ABORT_METHOD);
            } catch (LoginException le2) {
                throw le;
            }
            throw le;
        }
    }

    
Logout the Subject. 
 This method invokes the logout method for each LoginModule configured for this LoginContext. Each LoginModule performs its respective logout procedure which may include removing/destroying Principal and Credential information from the Subject and state cleanup. 
 Note that this method invokes all LoginModules configured for the application regardless of their respective Configuration flag parameters. Essentially this means that Requisite and Sufficient semantics are ignored for this method. This guarantees that proper cleanup and state restoration can take place. 
Throws:
/**
     * Logout the {@code Subject}.
     *
     * <p> This method invokes the {@code logout} method for each
     * {@code LoginModule} configured for this {@code LoginContext}.
     * Each {@code LoginModule} performs its respective logout procedure
     * which may include removing/destroying
     * {@code Principal} and {@code Credential} information
     * from the {@code Subject} and state cleanup.
     *
     * <p> Note that this method invokes all LoginModules configured for the
     * application regardless of their respective
     * {@code Configuration} flag parameters.  Essentially this means
     * that {@code Requisite} and {@code Sufficient} semantics are
     * ignored for this method.  This guarantees that proper cleanup
     * and state restoration can take place.
     *
     * @exception LoginException if the logout fails.
     */
    public void logout() throws LoginException {
        if (subject == null) {
            throw new LoginException(ResourcesMgr.getString
                ("null.subject.logout.called.before.login"));
        }

        // module invoked in doPrivileged
        invokePriv(LOGOUT_METHOD);
    }

    
Return the authenticated Subject.

Returns:the authenticated Subject.  If the caller specified a
         Subject to this LoginContext's constructor,
         this method returns the caller-specified Subject.
         If a Subject was not specified and authentication succeeds,
         this method returns the Subject instantiated and used for
         authentication by this LoginContext.
         If a Subject was not specified, and authentication fails or
         has not been attempted, this method returns null.
/**
     * Return the authenticated Subject.
     *
     * @return the authenticated Subject.  If the caller specified a
     *          Subject to this LoginContext's constructor,
     *          this method returns the caller-specified Subject.
     *          If a Subject was not specified and authentication succeeds,
     *          this method returns the Subject instantiated and used for
     *          authentication by this LoginContext.
     *          If a Subject was not specified, and authentication fails or
     *          has not been attempted, this method returns null.
     */
    public Subject getSubject() {
        if (!loginSucceeded && !subjectProvided)
            return null;
        return subject;
    }

    private void clearState() {
        moduleIndex = 0;
        firstError = null;
        firstRequiredError = null;
        success = false;
    }

    private void throwException(LoginException originalError, LoginException le)
    throws LoginException {

        // first clear state
        clearState();

        // throw the exception
        LoginException error = (originalError != null) ? originalError : le;
        throw error;
    }

    
Invokes the login, commit, and logout methods
from a LoginModule inside a doPrivileged block restricted
by creatorAcc (may be null).
This version is called if the caller did not instantiate
the LoginContext with a Configuration object.

/**
     * Invokes the login, commit, and logout methods
     * from a LoginModule inside a doPrivileged block restricted
     * by creatorAcc (may be null).
     *
     * This version is called if the caller did not instantiate
     * the LoginContext with a Configuration object.
     */
    private void invokePriv(final String methodName) throws LoginException {
        try {
            java.security.AccessController.doPrivileged
                (new java.security.PrivilegedExceptionAction<Void>() {
                public Void run() throws LoginException {
                    invoke(methodName);
                    return null;
                }
            }, creatorAcc);
        } catch (java.security.PrivilegedActionException pae) {
            throw (LoginException)pae.getException();
        }
    }

    private void invoke(String methodName) throws LoginException {

        // start at moduleIndex
        // - this can only be non-zero if methodName is LOGIN_METHOD

        for (int i = moduleIndex; i < moduleStack.length; i++, moduleIndex++) {
            try {

                if (moduleStack[i].module == null) {

                    // locate and instantiate the LoginModule
                    //
                    String name = moduleStack[i].entry.getLoginModuleName();
                    ServiceLoader<LoginModule> sc = AccessController.doPrivileged(
                            (PrivilegedAction<ServiceLoader<LoginModule>>)
                                    () -> ServiceLoader.load(
                                        LoginModule.class, contextClassLoader));
                    for (LoginModule m: sc) {
                        if (m.getClass().getName().equals(name)) {
                            moduleStack[i].module = m;
                            if (debug != null) {
                                debug.println(name + " loaded as a service");
                            }
                            break;
                        }
                    }

                    if (moduleStack[i].module == null) {
                        try {
                            @SuppressWarnings("deprecation")
                            Object tmp = Class.forName(name, false, contextClassLoader).newInstance();
                            moduleStack[i].module = (LoginModule) tmp;
                            if (debug != null) {
                                debug.println(name + " loaded via reflection");
                            }
                        } catch (ClassNotFoundException e) {
                            throw new LoginException("No LoginModule found for "
                                    + name);
                        }
                    }

                    // invoke the LoginModule initialize method
                    moduleStack[i].module.initialize(subject,
                            callbackHandler,
                            state,
                            moduleStack[i].entry.getOptions());
                }

                // find the requested method in the LoginModule
                boolean status;
                switch (methodName) {
                    case LOGIN_METHOD:
                        status = moduleStack[i].module.login();
                        break;
                    case COMMIT_METHOD:
                        status = moduleStack[i].module.commit();
                        break;
                    case LOGOUT_METHOD:
                        status = moduleStack[i].module.logout();
                        break;
                    case ABORT_METHOD:
                        status = moduleStack[i].module.abort();
                        break;
                    default:
                        throw new AssertionError("Unknown method " + methodName);
                }

                if (status == true) {

                    // if SUFFICIENT, return if no prior REQUIRED errors
                    if (!methodName.equals(ABORT_METHOD) &&
                        !methodName.equals(LOGOUT_METHOD) &&
                        moduleStack[i].entry.getControlFlag() ==
                    AppConfigurationEntry.LoginModuleControlFlag.SUFFICIENT &&
                        firstRequiredError == null) {

                        // clear state
                        clearState();

                        if (debug != null)
                            debug.println(methodName + " SUFFICIENT success");
                        return;
                    }

                    if (debug != null)
                        debug.println(methodName + " success");
                    success = true;
                } else {
                    if (debug != null)
                        debug.println(methodName + " ignored");
                }
            } catch (Exception ite) {

                // failure cases
                LoginException le;

                if (ite instanceof PendingException &&
                    methodName.equals(LOGIN_METHOD)) {

                    // XXX
                    //
                    // if a module's LOGIN_METHOD threw a PendingException
                    // then immediately throw it.
                    //
                    // when LoginContext is called again,
                    // the module that threw the exception is invoked first
                    // (the module list is not invoked from the start).
                    // previously thrown exception state is still present.
                    //
                    // it is assumed that the module which threw
                    // the exception can have its
                    // LOGIN_METHOD invoked twice in a row
                    // without any commit/abort in between.
                    //
                    // in all cases when LoginContext returns
                    // (either via natural return or by throwing an exception)
                    // we need to call clearState before returning.
                    // the only time that is not true is in this case -
                    // do not call throwException here.

                    throw (PendingException)ite;

                } else if (ite instanceof LoginException) {

                    le = (LoginException)ite;

                } else if (ite instanceof SecurityException) {

                    // do not want privacy leak
                    // (e.g., sensitive file path in exception msg)

                    le = new LoginException("Security Exception");
                    le.initCause(new SecurityException());
                    if (debug != null) {
                        debug.println
                            ("original security exception with detail msg " +
                            "replaced by new exception with empty detail msg");
                        debug.println("original security exception: " +
                                ite.toString());
                    }
                } else {

                    // capture an unexpected LoginModule exception
                    java.io.StringWriter sw = new java.io.StringWriter();
                    ite.printStackTrace
                            (new java.io.PrintWriter(sw));
                    sw.flush();
                    le = new LoginException(sw.toString());
                }

                if (moduleStack[i].entry.getControlFlag() ==
                    AppConfigurationEntry.LoginModuleControlFlag.REQUISITE) {

                    if (debug != null)
                        debug.println(methodName + " REQUISITE failure");

                    // if REQUISITE, then immediately throw an exception
                    if (methodName.equals(ABORT_METHOD) ||
                        methodName.equals(LOGOUT_METHOD)) {
                        if (firstRequiredError == null)
                            firstRequiredError = le;
                    } else {
                        throwException(firstRequiredError, le);
                    }

                } else if (moduleStack[i].entry.getControlFlag() ==
                    AppConfigurationEntry.LoginModuleControlFlag.REQUIRED) {

                    if (debug != null)
                        debug.println(methodName + " REQUIRED failure");

                    // mark down that a REQUIRED module failed
                    if (firstRequiredError == null)
                        firstRequiredError = le;

                } else {

                    if (debug != null)
                        debug.println(methodName + " OPTIONAL failure");

                    // mark down that an OPTIONAL module failed
                    if (firstError == null)
                        firstError = le;
                }
            }
        }

        // we went thru all the LoginModules.
        if (firstRequiredError != null) {
            // a REQUIRED module failed -- return the error
            throwException(firstRequiredError, null);
        } else if (success == false && firstError != null) {
            // no module succeeded -- return the first error
            throwException(firstError, null);
        } else if (success == false) {
            // no module succeeded -- all modules were IGNORED
            throwException(new LoginException
                (ResourcesMgr.getString("Login.Failure.all.modules.ignored")),
                null);
        } else {
            // success

            clearState();
            return;
        }
    }

    
Wrap the caller-specified CallbackHandler in our own
and invoke it within a privileged block, constrained by
the caller's AccessControlContext.

/**
     * Wrap the caller-specified CallbackHandler in our own
     * and invoke it within a privileged block, constrained by
     * the caller's AccessControlContext.
     */
    private static class SecureCallbackHandler implements CallbackHandler {

        private final java.security.AccessControlContext acc;
        private final CallbackHandler ch;

        SecureCallbackHandler(java.security.AccessControlContext acc,
                        CallbackHandler ch) {
            this.acc = acc;
            this.ch = ch;
        }

        public void handle(final Callback[] callbacks)
                throws java.io.IOException, UnsupportedCallbackException {
            try {
                java.security.AccessController.doPrivileged
                    (new java.security.PrivilegedExceptionAction<Void>() {
                    public Void run() throws java.io.IOException,
                                        UnsupportedCallbackException {
                        ch.handle(callbacks);
                        return null;
                    }
                }, acc);
            } catch (java.security.PrivilegedActionException pae) {
                if (pae.getException() instanceof java.io.IOException) {
                    throw (java.io.IOException)pae.getException();
                } else {
                    throw (UnsupportedCallbackException)pae.getException();
                }
            }
        }
    }

    
LoginModule information -
         incapsulates Configuration info and actual module instances

/**
     * LoginModule information -
     *          incapsulates Configuration info and actual module instances
     */
    private static class ModuleInfo {
        AppConfigurationEntry entry;
        LoginModule module;

        ModuleInfo(AppConfigurationEntry newEntry, LoginModule newModule) {
            this.entry = newEntry;
            this.module = newModule;
        }
    }
}