/*

 * Copyright (c) 2009, 2010, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.security.ssl;

import java.security.AccessControlContext;

import java.security.AccessController;

import java.security.Permission;

import java.security.Principal;

import java.security.PrivilegedAction;

import javax.crypto.SecretKey;

import javax.security.auth.Subject;

import javax.security.auth.login.LoginException;

/**

 * A helper class for Kerberos APIs.

 */

public final class Krb5Helper {

    private Krb5Helper() { }

    // loads Krb5Proxy implementation class if available

    private static final String IMPL_CLASS =

        "sun.security.ssl.krb5.Krb5ProxyImpl";

    private static final Krb5Proxy proxy =

        AccessController.doPrivileged(new PrivilegedAction<Krb5Proxy>() {

            public Krb5Proxy run() {

                try {

                    Class<?> c = Class.forName(IMPL_CLASS, true, null);

                    return (Krb5Proxy)c.newInstance();

                } catch (ClassNotFoundException cnf) {

                    return null;

                } catch (InstantiationException e) {

                    throw new AssertionError(e);

                } catch (IllegalAccessException e) {

                    throw new AssertionError(e);

                }

            }});

    /**

     * Returns true if Kerberos is available.

     */

    public static boolean isAvailable() {

        return proxy != null;

    }

    private static void ensureAvailable() {

        if (proxy == null)

            throw new AssertionError("Kerberos should have been available");

    }

    /**

     * Returns the Subject associated with client-side of the SSL socket.

     */

    public static Subject getClientSubject(AccessControlContext acc)

            throws LoginException {

        ensureAvailable();

        return proxy.getClientSubject(acc);

    }

    /**

     * Returns the Subject associated with server-side of the SSL socket.

     */

    public static Subject getServerSubject(AccessControlContext acc)

            throws LoginException {

        ensureAvailable();

        return proxy.getServerSubject(acc);

    }

    /**

     * Returns the KerberosKeys for the default server-side principal.

     */

    public static SecretKey[] getServerKeys(AccessControlContext acc)

            throws LoginException {

        ensureAvailable();

        return proxy.getServerKeys(acc);

    }

    /**

     * Returns the server-side principal name associated with the KerberosKey.

     */

    public static String getServerPrincipalName(SecretKey kerberosKey) {

        ensureAvailable();

        return proxy.getServerPrincipalName(kerberosKey);

    }

    /**

     * Returns the hostname embedded in the principal name.

     */

    public static String getPrincipalHostName(Principal principal) {

        ensureAvailable();

        return proxy.getPrincipalHostName(principal);

    }

    /**

     * Returns a ServicePermission for the principal name and action.

     */

    public static Permission getServicePermission(String principalName,

            String action) {

        ensureAvailable();

        return proxy.getServicePermission(principalName, action);

    }

}