/*

 * 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

 * particular file as subject to the "Classpath" exception as provided

 *

 * 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.

 *

 */

package sun.security.ssl.krb5;

import java.io.*;

import java.security.*;

import java.security.interfaces.*;

import javax.net.ssl.*;

import sun.security.krb5.EncryptionKey;

import sun.security.krb5.EncryptedData;

import sun.security.krb5.KrbException;

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

import sun.security.ssl.Debug;

import sun.security.ssl.HandshakeInStream;

import sun.security.ssl.HandshakeMessage;

import sun.security.ssl.ProtocolVersion;

/**

 * This is the Kerberos premaster secret in the Kerberos client key

 * exchange message (CLIENT --> SERVER); it holds the

 * Kerberos-encrypted pre-master secret. The secret is encrypted using the

 * Kerberos session key.  The padding and size of the resulting message

 * depends on the session key type, but the pre-master secret is

 * always exactly 48 bytes.

 *

 */

final class KerberosPreMasterSecret {

    private ProtocolVersion protocolVersion; // preMaster [0,1]

    private byte preMaster[];           // 48 bytes

    private byte encrypted[];

    /**

     * Constructor used by client to generate premaster secret.

     *

     * Client randomly creates a pre-master secret and encrypts it

     * using the Kerberos session key; only the server can decrypt

     * it, using the session key available in the service ticket.

     *

     * @param protocolVersion used to set preMaster[0,1]

     * @param generator random number generator for generating premaster secret

     * @param sessionKey Kerberos session key for encrypting premaster secret

     */

    KerberosPreMasterSecret(ProtocolVersion protocolVersion,

        SecureRandom generator, EncryptionKey sessionKey) throws IOException {

        if (sessionKey.getEType() ==

            EncryptedData.ETYPE_DES3_CBC_HMAC_SHA1_KD) {

            throw new IOException(

               "session keys with des3-cbc-hmac-sha1-kd encryption type " +

               "are not supported for TLS Kerberos cipher suites");

        }

        this.protocolVersion = protocolVersion;

        preMaster = generatePreMaster(generator, protocolVersion);

        // Encrypt premaster secret

        try {

            EncryptedData eData = new EncryptedData(sessionKey, preMaster,

                KeyUsage.KU_UNKNOWN);

            encrypted = eData.getBytes();  // not ASN.1 encoded.

        } catch (KrbException e) {

            throw (SSLKeyException)new SSLKeyException

                ("Kerberos premaster secret error").initCause(e);

        }

    }

    /*

     * Constructor used by server to decrypt encrypted premaster secret.

     * The protocol version in preMaster[0,1] must match either currentVersion

     * or clientVersion, otherwise, the premaster secret is set to

     * a random one to foil possible attack.

     *

     * @param currentVersion version of protocol being used

     * @param clientVersion version requested by client

     * @param generator random number generator used to generate

     *        bogus premaster secret if premaster secret verification fails

     * @param input input stream from which to read the encrypted

     *        premaster secret

     * @param sessionKey Kerberos session key to be used for decryption

     */

    KerberosPreMasterSecret(ProtocolVersion currentVersion,

        ProtocolVersion clientVersion,

        SecureRandom generator, HandshakeInStream input,

        EncryptionKey sessionKey) throws IOException {

         // Extract encrypted premaster secret from message

         encrypted = input.getBytes16();

         if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {

            if (encrypted != null) {

                Debug.println(System.out,

                     "encrypted premaster secret", encrypted);

            }

         }

        if (sessionKey.getEType() ==

            EncryptedData.ETYPE_DES3_CBC_HMAC_SHA1_KD) {

            throw new IOException(

               "session keys with des3-cbc-hmac-sha1-kd encryption type " +

               "are not supported for TLS Kerberos cipher suites");

        }

         // Decrypt premaster secret

         try {

            EncryptedData data = new EncryptedData(sessionKey.getEType(),

                        null /* optional kvno */, encrypted);

            byte[] temp = data.decrypt(sessionKey, KeyUsage.KU_UNKNOWN);

            if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {

                 if (encrypted != null) {

                     Debug.println(System.out,

                         "decrypted premaster secret", temp);

                 }

            }

            // Reset data stream after decryption, remove redundant bytes

            preMaster =  data.reset(temp, false);

            protocolVersion = ProtocolVersion.valueOf(preMaster[0],

                 preMaster[1]);

            if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {

                 System.out.println("Kerberos PreMasterSecret version: "

                        + protocolVersion);

            }

        } catch (Exception e) {

            // catch exception & process below

            preMaster = null;

            protocolVersion = currentVersion;

        }

        // check if the premaster secret version is ok

        // the specification says that it must be the maximum version supported

        // by the client from its ClientHello message. However, many

        // implementations send the negotiated version, so accept both

        // NOTE that we may be comparing two unsupported version numbers in

        // the second case, which is why we cannot use object references

        // equality in this special case

        boolean versionMismatch = (protocolVersion != currentVersion) &&

                                  (protocolVersion.v != clientVersion.v);

        /*

         * Bogus decrypted ClientKeyExchange? If so, conjure a

         * a random preMaster secret that will fail later during

         * Finished message processing. This is a countermeasure against

         * the "interactive RSA PKCS#1 encryption envelop attack" reported

         * in June 1998. Preserving the executation path will

         * mitigate timing attacks and force consistent error handling

         * that will prevent an attacking client from differentiating

         * different kinds of decrypted ClientKeyExchange bogosities.

         */

         if ((preMaster == null) || (preMaster.length != 48)

                || versionMismatch) {

            if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {

                System.out.println("Kerberos PreMasterSecret error, "

                                   + "generating random secret");

                if (preMaster != null) {

                    Debug.println(System.out, "Invalid secret", preMaster);

                }

            }

            preMaster = generatePreMaster(generator, currentVersion);

            protocolVersion = currentVersion;

        }

    }

    /*

     * Used by server to generate premaster secret in case of

     * problem decoding ticket.

     *

     * @param protocolVersion used for preMaster[0,1]

     * @param generator random number generator to use for generating secret.

     */

    KerberosPreMasterSecret(ProtocolVersion protocolVersion,

        SecureRandom generator) {

        this.protocolVersion = protocolVersion;

        preMaster = generatePreMaster(generator, protocolVersion);

    }

    private static byte[] generatePreMaster(SecureRandom rand,

        ProtocolVersion ver) {

        byte[] pm = new byte[48];

        rand.nextBytes(pm);

        pm[0] = ver.major;

        pm[1] = ver.minor;

        return pm;

    }

    // Clone not needed; internal use only

    byte[] getUnencrypted() {

        return preMaster;

    }

    // Clone not needed; internal use only

    byte[] getEncrypted() {

        return encrypted;

    }

}