/*

 * Copyright (c) 2003, 2011, 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.jgss.krb5;

import javax.security.auth.kerberos.KerberosTicket;

import javax.security.auth.kerberos.KerberosKey;

import javax.security.auth.kerberos.KerberosPrincipal;

import javax.security.auth.kerberos.KeyTab;

import javax.security.auth.Subject;

import javax.security.auth.login.LoginException;

import java.security.AccessControlContext;

import sun.security.jgss.GSSUtil;

import sun.security.jgss.GSSCaller;

import sun.security.krb5.Credentials;

import sun.security.krb5.EncryptionKey;

import sun.security.krb5.KrbException;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import sun.security.krb5.KerberosSecrets;

import sun.security.krb5.PrincipalName;

/**

 * Utilities for obtaining and converting Kerberos tickets.

 *

 */

public class Krb5Util {

    static final boolean DEBUG =

        java.security.AccessController.doPrivileged(

            new sun.security.action.GetBooleanAction

            ("sun.security.krb5.debug")).booleanValue();

    /**

     * Default constructor

     */

    private Krb5Util() {  // Cannot create one of these

    }

    /**

     * Retrieve the service ticket for serverPrincipal from caller's Subject

     * or from Subject obtained by logging in, or if not found, via the

     * Ticket Granting Service using the TGT obtained from the Subject.

     *

     * Caller must have permission to:

     *    - access and update Subject's private credentials

     *    - create LoginContext

     *    - read the auth.login.defaultCallbackHandler security property

     *

     * NOTE: This method is used by JSSE Kerberos Cipher Suites

     */

    public static KerberosTicket getTicketFromSubjectAndTgs(GSSCaller caller,

        String clientPrincipal, String serverPrincipal, String tgsPrincipal,

        AccessControlContext acc)

        throws LoginException, KrbException, IOException {

        // 1. Try to find service ticket in acc subject

        Subject accSubj = Subject.getSubject(acc);

        KerberosTicket ticket = SubjectComber.find(accSubj,

            serverPrincipal, clientPrincipal, KerberosTicket.class);

        if (ticket != null) {

            return ticket;  // found it

        }

        Subject loginSubj = null;

        if (!GSSUtil.useSubjectCredsOnly(caller)) {

            // 2. Try to get ticket from login

            try {

                loginSubj = GSSUtil.login(caller, GSSUtil.GSS_KRB5_MECH_OID);

                ticket = SubjectComber.find(loginSubj,

                    serverPrincipal, clientPrincipal, KerberosTicket.class);

                if (ticket != null) {

                    return ticket; // found it

                }

            } catch (LoginException e) {

                // No login entry to use

                // ignore and continue

            }

        }

        // Service ticket not found in subject or login

        // Try to get TGT to acquire service ticket

        // 3. Try to get TGT from acc subject

        KerberosTicket tgt = SubjectComber.find(accSubj,

            tgsPrincipal, clientPrincipal, KerberosTicket.class);

        boolean fromAcc;

        if (tgt == null && loginSubj != null) {

            // 4. Try to get TGT from login subject

            tgt = SubjectComber.find(loginSubj,

                tgsPrincipal, clientPrincipal, KerberosTicket.class);

            fromAcc = false;

        } else {

            fromAcc = true;

        }

        // 5. Try to get service ticket using TGT

        if (tgt != null) {

            Credentials tgtCreds = ticketToCreds(tgt);

            Credentials serviceCreds = Credentials.acquireServiceCreds(

                        serverPrincipal, tgtCreds);

            if (serviceCreds != null) {

                ticket = credsToTicket(serviceCreds);

                // Store service ticket in acc's Subject

                if (fromAcc && accSubj != null && !accSubj.isReadOnly()) {

                    accSubj.getPrivateCredentials().add(ticket);

                }

            }

        }

        return ticket;

    }

    /**

     * Retrieves the ticket corresponding to the client/server principal

     * pair from the Subject in the specified AccessControlContext.

     * If the ticket can not be found in the Subject, and if

     * useSubjectCredsOnly is false, then obtain ticket from

     * a LoginContext.

     */

    static KerberosTicket getTicket(GSSCaller caller,

        String clientPrincipal, String serverPrincipal,

        AccessControlContext acc) throws LoginException {

        // Try to get ticket from acc's Subject

        Subject accSubj = Subject.getSubject(acc);

        KerberosTicket ticket =

            SubjectComber.find(accSubj, serverPrincipal, clientPrincipal,

                  KerberosTicket.class);

        // Try to get ticket from Subject obtained from GSSUtil

        if (ticket == null && !GSSUtil.useSubjectCredsOnly(caller)) {

            Subject subject = GSSUtil.login(caller, GSSUtil.GSS_KRB5_MECH_OID);

            ticket = SubjectComber.find(subject,

                serverPrincipal, clientPrincipal, KerberosTicket.class);

        }

        return ticket;

    }

    /**

     * Retrieves the caller's Subject, or Subject obtained by logging in

     * via the specified caller.

     *

     * Caller must have permission to:

     *    - access the Subject

     *    - create LoginContext

     *    - read the auth.login.defaultCallbackHandler security property

     *

     * NOTE: This method is used by JSSE Kerberos Cipher Suites

     */

    public static Subject getSubject(GSSCaller caller,

        AccessControlContext acc) throws LoginException {

        // Try to get the Subject from acc

        Subject subject = Subject.getSubject(acc);

        // Try to get Subject obtained from GSSUtil

        if (subject == null && !GSSUtil.useSubjectCredsOnly(caller)) {

            subject = GSSUtil.login(caller, GSSUtil.GSS_KRB5_MECH_OID);

        }

        return subject;

    }

    /**

     * Retrieves the ServiceCreds for the specified server principal from

     * the Subject in the specified AccessControlContext. If not found, and if

     * useSubjectCredsOnly is false, then obtain from a LoginContext.

     *

     * NOTE: This method is also used by JSSE Kerberos Cipher Suites

     */

    public static ServiceCreds getServiceCreds(GSSCaller caller,

        String serverPrincipal, AccessControlContext acc)

                throws LoginException {

        Subject accSubj = Subject.getSubject(acc);

        ServiceCreds sc = null;

        if (accSubj != null) {

            sc = ServiceCreds.getInstance(accSubj, serverPrincipal);

        }

        if (sc == null && !GSSUtil.useSubjectCredsOnly(caller)) {

            Subject subject = GSSUtil.login(caller, GSSUtil.GSS_KRB5_MECH_OID);

            sc = ServiceCreds.getInstance(subject, serverPrincipal);

        }

        return sc;

    }

    public static KerberosTicket credsToTicket(Credentials serviceCreds) {

        EncryptionKey sessionKey =  serviceCreds.getSessionKey();

        return new KerberosTicket(

            serviceCreds.getEncoded(),

            new KerberosPrincipal(serviceCreds.getClient().getName()),

            new KerberosPrincipal(serviceCreds.getServer().getName(),

                                KerberosPrincipal.KRB_NT_SRV_INST),

            sessionKey.getBytes(),

            sessionKey.getEType(),

            serviceCreds.getFlags(),

            serviceCreds.getAuthTime(),

            serviceCreds.getStartTime(),

            serviceCreds.getEndTime(),

            serviceCreds.getRenewTill(),

            serviceCreds.getClientAddresses());

    };

    public static Credentials ticketToCreds(KerberosTicket kerbTicket)

            throws KrbException, IOException {

        return new Credentials(

            kerbTicket.getEncoded(),

            kerbTicket.getClient().getName(),

            kerbTicket.getServer().getName(),

            kerbTicket.getSessionKey().getEncoded(),

            kerbTicket.getSessionKeyType(),

            kerbTicket.getFlags(),

            kerbTicket.getAuthTime(),

            kerbTicket.getStartTime(),

            kerbTicket.getEndTime(),

            kerbTicket.getRenewTill(),

            kerbTicket.getClientAddresses());

    }

    /**

     * A helper method to get EncryptionKeys from a javax..KeyTab

     * @param ktab the javax..KeyTab class

     * @param cname the PrincipalName

     * @return the EKeys, never null, might be empty

     */

    public static EncryptionKey[] keysFromJavaxKeyTab(

            KeyTab ktab, PrincipalName cname) {

        return KerberosSecrets.getJavaxSecurityAuthKerberosAccess().

                keyTabGetEncryptionKeys(ktab, cname);

    }

}