/*

 * Copyright (c) 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

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package sun.security.krb5.internal;

import java.io.ByteArrayOutputStream;

import java.io.IOException;

import sun.security.krb5.*;

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

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

import sun.security.util.DerOutputStream;

import sun.security.util.DerValue;

/**

 * Implements the ASN.1 PA-FOR-USER type.

 *

 * <pre>{@code

 * padata-type  ::= PA-FOR-USER

 *                  -- value 129

 * padata-value ::= EncryptedData

 *                  -- PA-FOR-USER-ENC

 * PA-FOR-USER-ENC ::= SEQUENCE {

 *     userName[0] PrincipalName,

 *     userRealm[1] Realm,

 *     cksum[2] Checksum,

 *     auth-package[3] KerberosString

 * }

 * }</pre>

 *

 * <p>

 * This definition reflects MS-SFU.

 */

public class PAForUserEnc {

    final public PrincipalName name;

    final private EncryptionKey key;

    final public static String AUTH_PACKAGE = "Kerberos";

    public PAForUserEnc(PrincipalName name, EncryptionKey key) {

        this.name = name;

        this.key = key;

    }

    /**

     * Constructs a PA-FOR-USER object from a DER encoding.

     * @param encoding the input object

     * @param key the key to verify the checksum inside encoding

     * @throws KrbException if the verification fails.

     * Note: this method is now only used by test KDC, therefore

     * the verification is ignored (at the moment).

     */

    public PAForUserEnc(DerValue encoding, EncryptionKey key)

            throws Asn1Exception, KrbException, IOException {

        DerValue der = null;

        this.key = key;

        if (encoding.getTag() != DerValue.tag_Sequence) {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        }

        // Realm after name? Quite abnormal.

        PrincipalName tmpName = null;

        der = encoding.getData().getDerValue();

        if ((der.getTag() & 0x1F) == 0x00) {

            try {

                tmpName = new PrincipalName(der.getData().getDerValue(),

                    new Realm("PLACEHOLDER"));

            } catch (RealmException re) {

                // Impossible

            }

        } else {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        }

        der = encoding.getData().getDerValue();

        if ((der.getTag() & 0x1F) == 0x01) {

            try {

                Realm realm = new Realm(der.getData().getDerValue());

                name = new PrincipalName(

                        tmpName.getNameType(), tmpName.getNameStrings(), realm);

            } catch (RealmException re) {

                throw new IOException(re);

            }

        } else {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        }

        der = encoding.getData().getDerValue();

        if ((der.getTag() & 0x1F) == 0x02) {

            // Deal with the checksum

        } else {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        }

        der = encoding.getData().getDerValue();

        if ((der.getTag() & 0x1F) == 0x03) {

            String authPackage = new KerberosString(der.getData().getDerValue()).toString();

            if (!authPackage.equalsIgnoreCase(AUTH_PACKAGE)) {

                throw new IOException("Incorrect auth-package");

            }

        } else {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        }

        if (encoding.getData().available() > 0)

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

    }

    public byte[] asn1Encode() throws Asn1Exception, IOException {

        DerOutputStream bytes = new DerOutputStream();

        bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte)0x00), name.asn1Encode());

        bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte)0x01), name.getRealm().asn1Encode());

        try {

            Checksum cks = new Checksum(

                    Checksum.CKSUMTYPE_HMAC_MD5_ARCFOUR,

                    getS4UByteArray(),

                    key,

                    KeyUsage.KU_PA_FOR_USER_ENC_CKSUM);

            bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte)0x02), cks.asn1Encode());

        } catch (KrbException ke) {

            throw new IOException(ke);

        }

        DerOutputStream temp = new DerOutputStream();

        temp.putDerValue(new KerberosString(AUTH_PACKAGE).toDerValue());

        bytes.write(DerValue.createTag(DerValue.TAG_CONTEXT, true, (byte)0x03), temp);

        temp = new DerOutputStream();

        temp.write(DerValue.tag_Sequence, bytes);

        return temp.toByteArray();

    }

    /**

     * Returns S4UByteArray, the block to calculate checksum inside a

     * PA-FOR-USER-ENC data structure. It includes:

     * 1. userName.name-type encoded as a 4-byte integer in little endian

     *    byte order

     * 2. all string values in the sequence of strings contained in the

     *    userName.name-string field

     * 3. the string value of the userRealm field

     * 4. the string value of auth-package field

     */

    public byte[] getS4UByteArray() {

        try {

            ByteArrayOutputStream ba = new ByteArrayOutputStream();

            ba.write(new byte[4]);

            for (String s: name.getNameStrings()) {

                ba.write(s.getBytes("UTF-8"));

            }

            ba.write(name.getRealm().toString().getBytes("UTF-8"));

            ba.write(AUTH_PACKAGE.getBytes("UTF-8"));

            byte[] output = ba.toByteArray();

            int pnType = name.getNameType();

            output[0] = (byte)(pnType & 0xff);

            output[1] = (byte)((pnType>>8) & 0xff);

            output[2] = (byte)((pnType>>16) & 0xff);

            output[3] = (byte)((pnType>>24) & 0xff);

            return output;

        } catch (IOException ioe) {

            // not possible

            throw new AssertionError("Cannot write ByteArrayOutputStream", ioe);

        }

    }

    public String toString() {

        return "PA-FOR-USER: " + name;

    }

}