/*

 * Copyright (c) 2010, 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.krb5;

import java.io.IOException;

import java.util.Arrays;

import javax.security.auth.kerberos.KeyTab;

import sun.security.jgss.krb5.Krb5Util;

import sun.security.krb5.internal.HostAddresses;

import sun.security.krb5.internal.KDCOptions;

import sun.security.krb5.internal.KRBError;

import sun.security.krb5.internal.KerberosTime;

import sun.security.krb5.internal.Krb5;

import sun.security.krb5.internal.PAData;

import sun.security.krb5.internal.crypto.EType;

/**

 * A manager class for AS-REQ communications.

 *

 * This class does:

 * 1. Gather information to create AS-REQ

 * 2. Create and send AS-REQ

 * 3. Receive AS-REP and KRB-ERROR (-KRB_ERR_RESPONSE_TOO_BIG) and parse them

 * 4. Emit credentials and secret keys (for JAAS storeKey=true with password)

 *

 * This class does not:

 * 1. Deal with real communications (KdcComm does it, and TGS-REQ)

 *    a. Name of KDCs for a realm

 *    b. Server availability, timeout, UDP or TCP

 *    d. KRB_ERR_RESPONSE_TOO_BIG

 * 2. Stores its own copy of password, this means:

 *    a. Do not change/wipe it before Builder finish

 *    b. Builder will not wipe it for you

 *

 * With this class:

 * 1. KrbAsReq has only one constructor

 * 2. Krb5LoginModule and Kinit call a single builder

 * 3. Better handling of sensitive info

 *

 * @since 1.7

 */

public final class KrbAsReqBuilder {

    // Common data for AS-REQ fields

    private KDCOptions options;

    private PrincipalName cname;

    private PrincipalName sname;

    private KerberosTime from;

    private KerberosTime till;

    private KerberosTime rtime;

    private HostAddresses addresses;

    // Secret source: can't be changed once assigned, only one (of the two

    // sources) can be set to non-null

    private final char[] password;

    private final KeyTab ktab;

    // Used to create a ENC-TIMESTAMP in the 2nd AS-REQ

    private PAData[] paList;        // PA-DATA from both KRB-ERROR and AS-REP.

                                    // Used by getKeys() only.

                                    // Only AS-REP should be enough per RFC,

                                    // combined in case etypes are different.

    // The generated and received:

    private KrbAsReq req;

    private KrbAsRep rep;

    private static enum State {

        INIT,       // Initialized, can still add more initialization info

        REQ_OK,     // AS-REQ performed

        DESTROYED,  // Destroyed, not usable anymore

    }

    private State state;

    // Called by other constructors

    private void init(PrincipalName cname)

            throws KrbException {

        if (cname.getRealm() == null) {

            cname.setRealm(Config.getInstance().getDefaultRealm());

        }

        this.cname = cname;

        state = State.INIT;

    }

    /**

     * Creates a builder to be used by {@code cname} with existing keys.

     *

     * @param cname the client of the AS-REQ. Must not be null. Might have no

     * realm, where default realm will be used. This realm will be the target

     * realm for AS-REQ. I believe a client should only get initial TGT from

     * its own realm.

     * @param keys must not be null. if empty, might be quite useless.

     * This argument will neither be modified nor stored by the method.

     * @throws KrbException

     */

    public KrbAsReqBuilder(PrincipalName cname, KeyTab ktab)

            throws KrbException {

        init(cname);

        this.ktab = ktab;

        this.password = null;

    }

    /**

     * Creates a builder to be used by {@code cname} with a known password.

     *

     * @param cname the client of the AS-REQ. Must not be null. Might have no

     * realm, where default realm will be used. This realm will be the target

     * realm for AS-REQ. I believe a client should only get initial TGT from

     * its own realm.

     * @param pass must not be null. This argument will neither be modified

     * nor stored by the method.

     * @throws KrbException

     */

    public KrbAsReqBuilder(PrincipalName cname, char[] pass)

            throws KrbException {

        init(cname);

        this.password = pass.clone();

        this.ktab = null;

    }

    /**

     * Retrieves an array of secret keys for the client. This is used when

     * the client supplies password but need keys to act as an acceptor

     * (in JAAS words, isInitiator=true and storeKey=true)

     * @return generated keys from password. PA-DATA from server might be used.

     * All "default_tkt_enctypes" keys will be generated, Never null.

     * @throws IllegalStateException if not constructed from a password

     * @throws KrbException

     */

    public EncryptionKey[] getKeys() throws KrbException {

        checkState(State.REQ_OK, "Cannot get keys");

        if (password != null) {

            int[] eTypes = EType.getDefaults("default_tkt_enctypes");

            EncryptionKey[] result = new EncryptionKey[eTypes.length];

            /*

             * Returns an array of keys. Before KrbAsReqBuilder, all etypes

             * use the same salt which is either the default one or a new salt

             * coming from PA-DATA. After KrbAsReqBuilder, each etype uses its

             * own new salt from PA-DATA. For an etype with no PA-DATA new salt

             * at all, what salt should it use?

             *

             * Commonly, the stored keys are only to be used by an acceptor to

             * decrypt service ticket in AP-REQ. Most impls only allow keys

             * from a keytab on acceptor, but unfortunately (?) Java supports

             * acceptor using password. In this case, if the service ticket is

             * encrypted using an etype which we don't have PA-DATA new salt,

             * user name). Instead, we would use the new salt of another etype.

             */

            String salt = null;     // the saved new salt

                    PAData.SaltAndParams snp =

                            PAData.getSaltAndParams(eTypes[i], paList);

                }

            }

            return result;

        } else {

            throw new IllegalStateException("Required password not provided");

        }

    }

    /**

     * Sets or clears options. If cleared, default options will be used

     * at creation time.

     * @param options

     */

    public void setOptions(KDCOptions options) {

        checkState(State.INIT, "Cannot specify options");

        this.options = options;

    }

    /**

     * Sets or clears target. If cleared, KrbAsReq might choose krbtgt

     * for cname realm

     * @param sname

     */

    public void setTarget(PrincipalName sname) {

        checkState(State.INIT, "Cannot specify target");

        this.sname = sname;

    }

    /**

     * Adds or clears addresses. KrbAsReq might add some if empty

     * field not allowed

     * @param addresses

     */

    public void setAddresses(HostAddresses addresses) {

        checkState(State.INIT, "Cannot specify addresses");

        this.addresses = addresses;

    }

    /**

     * Build a KrbAsReq object from all info fed above. Normally this method

     * will be called twice: initial AS-REQ and second with pakey

     * @param key null (initial AS-REQ) or pakey (with preauth)

     * @return the KrbAsReq object

     * @throws KrbException

     * @throws IOException

     */

    private KrbAsReq build(EncryptionKey key) throws KrbException, IOException {

        int[] eTypes;

        if (password != null) {

            eTypes = EType.getDefaults("default_tkt_enctypes");

        } else {

            EncryptionKey[] ks = Krb5Util.keysFromJavaxKeyTab(ktab, cname);

            eTypes = EType.getDefaults("default_tkt_enctypes",

                    ks);

            for (EncryptionKey k: ks) k.destroy();

        }

        return new KrbAsReq(key,

            options,

            cname,

            sname,

            from,

            till,

            rtime,

            eTypes,

            addresses);

    }

    /**

     * Parses AS-REP, decrypts enc-part, retrieves ticket and session key

     * @throws KrbException

     * @throws Asn1Exception

     * @throws IOException

     */

    private KrbAsReqBuilder resolve()

            throws KrbException, Asn1Exception, IOException {

        if (ktab != null) {

            rep.decryptUsingKeyTab(ktab, req, cname);

        } else {

            rep.decryptUsingPassword(password, req, cname);

        }

        if (rep.getPA() != null) {

            if (paList == null || paList.length == 0) {

                paList = rep.getPA();

            } else {

                int extraLen = rep.getPA().length;

                if (extraLen > 0) {

                    int oldLen = paList.length;

                    paList = Arrays.copyOf(paList, paList.length + extraLen);

                    System.arraycopy(rep.getPA(), 0, paList, oldLen, extraLen);

                }

            }

        }

        return this;

    }

    /**

     * Communication until AS-REP or non preauth-related KRB-ERROR received

     * @throws KrbException

     * @throws IOException

     */

    private KrbAsReqBuilder send() throws KrbException, IOException {

        boolean preAuthFailedOnce = false;

        KdcComm comm = new KdcComm(cname.getRealmAsString());

        EncryptionKey pakey = null;

        while (true) {

            try {

                req = build(pakey);

                rep = new KrbAsRep(comm.send(req.encoding()));

                return this;

            } catch (KrbException ke) {

                if (!preAuthFailedOnce && (

                        ke.returnCode() == Krb5.KDC_ERR_PREAUTH_FAILED ||

                        ke.returnCode() == Krb5.KDC_ERR_PREAUTH_REQUIRED)) {

                    if (Krb5.DEBUG) {

                        System.out.println("KrbAsReqBuilder: " +

                                "PREAUTH FAILED/REQ, re-send AS-REQ");

                    }

                    preAuthFailedOnce = true;

                    KRBError kerr = ke.getError();

                    if (password == null) {

                        EncryptionKey[] ks = Krb5Util.keysFromJavaxKeyTab(ktab, cname);

                        if (pakey != null) pakey = (EncryptionKey)pakey.clone();

                        for (EncryptionKey k: ks) k.destroy();

                    } else {

                    }

                    paList = kerr.getPA();  // Update current paList

                } else {

                    throw ke;

                }

            }

        }

    }

    /**

     * Performs AS-REQ send and AS-REP receive.

     * Maybe a state is needed here, to divide prepare process and getCreds.

     * @throws KrbException

     * @throws Asn1Exception

     * @throws IOException

     */

    public KrbAsReqBuilder action()

            throws KrbException, Asn1Exception, IOException {

        checkState(State.INIT, "Cannot call action");

        state = State.REQ_OK;

        return send().resolve();

    }

    /**

     * Gets Credentials object after action

     */

    public Credentials getCreds() {

        checkState(State.REQ_OK, "Cannot retrieve creds");

        return rep.getCreds();

    }

    /**

     * Gets another type of Credentials after action

     */

    public sun.security.krb5.internal.ccache.Credentials getCCreds() {

        checkState(State.REQ_OK, "Cannot retrieve CCreds");

        return rep.getCCreds();

    }

    /**

     * Destroys the object and clears keys and password info.

     */

    public void destroy() {

        state = State.DESTROYED;

        if (password != null) {

            Arrays.fill(password, (char)0);

        }

    }

    /**

     * Checks if the current state is the specified one.

     * @param st the expected state

     * @param msg error message if state is not correct

     * @throws IllegalStateException if state is not correct

     */

    private void checkState(State st, String msg) {

        if (state != st) {

            throw new IllegalStateException(msg + " at " + st + " state");

        }

    }

}