/*

 * Copyright (c) 2000, 2012, 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.

 */

/*

 *

 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.

 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.

 */

package sun.security.krb5.internal.ktab;

import sun.security.krb5.internal.*;

import sun.security.krb5.PrincipalName;

import sun.security.krb5.Realm;

import sun.security.krb5.RealmException;

import sun.security.krb5.internal.util.KrbDataInputStream;

import java.io.IOException;

import java.io.InputStream;

/**

 * This class implements a buffered input stream. It is used for parsing key table

 * data to memory.

 *

 * @author Yanni Zhang

 *

 */

public class KeyTabInputStream extends KrbDataInputStream implements KeyTabConstants {

    boolean DEBUG = Krb5.DEBUG;

    int index;

    public KeyTabInputStream(InputStream is) {

        super(is);

    }

    /**

     * Reads the number of bytes this entry data occupy.

     */

    int readEntryLength() throws IOException {

        return read(4);

    }

    KeyTabEntry readEntry(int entryLen, int ktVersion) throws IOException, RealmException {

        index = entryLen;

        if (index == 0) {    //in native implementation, when the last entry is deleted, a byte 0 is left.

            return null;

        }

        if (index < 0) {    //in native implementation, when one of the entries is deleted, the entry length turns to be negative, and

            skip(Math.abs(index));                //the fields are left with 0 bytes

            return null;

        }

        int principalNum = read(2);     //the number of service names.

        index -= 2;

        if (ktVersion == KRB5_KT_VNO_1) {   //V1 includes realm in the count.

            principalNum -= 1;

        }

        Realm realm = new Realm(readName());

        String[] nameParts = new String[principalNum];

        for (int i = 0; i < principalNum; i++) {

            nameParts[i] = readName();

        }

        int nameType = read(4);

        index -= 4;

        PrincipalName service = new PrincipalName(nameType, nameParts, realm);

        KerberosTime timeStamp = readTimeStamp();

        int keyVersion = read() & 0xff;

        index -= 1;

        int keyType = read(2);

        index -= 2;

        int keyLength = read(2);

        index -= 2;

        byte[] keyblock = readKey(keyLength);

        index -= keyLength;

        // There might be a 32 bit kvno here.

        // If index is zero, assume that the 8 bit key version number was

        // right, otherwise trust the new nonzero value.

        if (index >= 4) {

            int extKvno = read(4);

            if (extKvno != 0) {

                keyVersion = extKvno;

            }

            index -= 4;

        }

        // if index is negative, the keytab format must be wrong.

        if (index < 0) {

            throw new RealmException("Keytab is corrupted");

        }

        // ignore the left bytes.

        skip(index);

        return new KeyTabEntry(service, realm, timeStamp, keyVersion, keyType, keyblock);

    }

    byte[] readKey(int length) throws IOException {

        byte[] bytes = new byte[length];

        read(bytes, 0, length);

        return bytes;

    }

    KerberosTime readTimeStamp() throws IOException {

        index -= 4;

        return new KerberosTime((long)read(4) * 1000);

    }

    String readName() throws IOException {

        String name;

        int length = read(2);   //length of the realm name or service name

        index -= 2;

        byte[] bytes = new byte[length];

        read(bytes, 0, length);

        index -= length;

        name = new String(bytes);

        if (DEBUG) {

            System.out.println(">>> KeyTabInputStream, readName(): " + name);

        }

        return name;

    }

}