/*

 * 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

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 */

package com.sun.security.sasl;

import javax.security.sasl.SaslException;

import javax.security.sasl.Sasl;

// For HMAC_MD5

import java.security.NoSuchAlgorithmException;

import java.security.MessageDigest;

import java.util.Arrays;

import java.util.logging.Logger;

/**

  * Base class for implementing CRAM-MD5 client and server mechanisms.

  *

  * @author Vincent Ryan

  * @author Rosanna Lee

  */

abstract class CramMD5Base {

    protected boolean completed = false;

    protected boolean aborted = false;

    protected byte[] pw;

    protected CramMD5Base() {

        initLogger();

    }

    /**

     * Retrieves this mechanism's name.

     *

     * @return  The string "CRAM-MD5".

     */

    public String getMechanismName() {

        return "CRAM-MD5";

    }

    /**

     * Determines whether this mechanism has completed.

     * CRAM-MD5 completes after processing one challenge from the server.

     *

     * @return true if has completed; false otherwise;

     */

    public boolean isComplete() {

        return completed;

    }

    /**

      * Unwraps the incoming buffer. CRAM-MD5 supports no security layer.

      *

      * @throws SaslException If attempt to use this method.

      */

    public byte[] unwrap(byte[] incoming, int offset, int len)

        throws SaslException {

        if (completed) {

            throw new IllegalStateException(

                "CRAM-MD5 supports neither integrity nor privacy");

        } else {

            throw new IllegalStateException(

                "CRAM-MD5 authentication not completed");

        }

    }

    /**

      * Wraps the outgoing buffer. CRAM-MD5 supports no security layer.

      *

      * @throws SaslException If attempt to use this method.

      */

    public byte[] wrap(byte[] outgoing, int offset, int len) throws SaslException {

        if (completed) {

            throw new IllegalStateException(

                "CRAM-MD5 supports neither integrity nor privacy");

        } else {

            throw new IllegalStateException(

                "CRAM-MD5 authentication not completed");

        }

    }

    /**

     * Retrieves the negotiated property.

     * This method can be called only after the authentication exchange has

     * completed (i.e., when {@code isComplete()} returns true); otherwise, a

     * {@code SaslException} is thrown.

     *

     * @return value of property; only QOP is applicable to CRAM-MD5.

     * @exception IllegalStateException if this authentication exchange has not completed

     */

    public Object getNegotiatedProperty(String propName) {

        if (completed) {

            if (propName.equals(Sasl.QOP)) {

                return "auth";

            } else {

                return null;

            }

        } else {

            throw new IllegalStateException(

                "CRAM-MD5 authentication not completed");

        }

    }

    public void dispose() throws SaslException {

        clearPassword();

    }

    protected void clearPassword() {

        if (pw != null) {

            // zero out password

            for (int i = 0; i < pw.length; i++) {

                pw[i] = (byte)0;

            }

            pw = null;

        }

    }

    protected void finalize() {

        clearPassword();

    }

    static private final int MD5_BLOCKSIZE = 64;

    /**

     * Hashes its input arguments according to HMAC-MD5 (RFC 2104)

     * and returns the resulting digest in its ASCII representation.

     *

     * HMAC-MD5 function is described as follows:

     *

     *       MD5(key XOR opad, MD5(key XOR ipad, text))

     *

     * where key  is an n byte key

     *       ipad is the byte 0x36 repeated 64 times

     *       opad is the byte 0x5c repeated 64 times

     *       text is the data to be protected

     */

    final static String HMAC_MD5(byte[] key, byte[] text)

        throws NoSuchAlgorithmException {

        MessageDigest md5 = MessageDigest.getInstance("MD5");

        /* digest the key if longer than 64 bytes */

        if (key.length > MD5_BLOCKSIZE) {

            key = md5.digest(key);

        }

        byte[] ipad = new byte[MD5_BLOCKSIZE];  /* inner padding */

        byte[] opad = new byte[MD5_BLOCKSIZE];  /* outer padding */

        byte[] digest;

        int i;

        /* store key in pads */

        for (i = 0; i < key.length; i++) {

            ipad[i] = key[i];

            opad[i] = key[i];

        }

        /* XOR key with pads */

        for (i = 0; i < MD5_BLOCKSIZE; i++) {

            ipad[i] ^= 0x36;

            opad[i] ^= 0x5c;

        }

        /* inner MD5 */

        md5.update(ipad);

        md5.update(text);

        digest = md5.digest();

        /* outer MD5 */

        md5.update(opad);

        md5.update(digest);

        digest = md5.digest();

        // Get character representation of digest

        StringBuilder digestString = new StringBuilder();

        for (i = 0; i < digest.length; i++) {

            if ((digest[i] & 0x000000ff) < 0x10) {

                digestString.append('0').append(Integer.toHexString(digest[i] & 0x000000ff));

            } else {

                digestString.append(

                    Integer.toHexString(digest[i] & 0x000000ff));

            }

        }

        Arrays.fill(ipad, (byte)0);

        Arrays.fill(opad, (byte)0);

        ipad = null;

        opad = null;

        return (digestString.toString());

    }

    /**

     * Sets logger field.

     */

    private static synchronized void initLogger() {

        if (logger == null) {

            logger = Logger.getLogger(SASL_LOGGER_NAME);

        }

    }

    /**

     * Logger for debug messages

     */

    private static final String SASL_LOGGER_NAME = "javax.security.sasl";

    protected static Logger logger;  // set in initLogger(); lazily loads logger

}