/*

 * Copyright (c) 2003, 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.

 */

package com.sun.security.sasl;

import javax.security.sasl.*;

import javax.security.auth.callback.*;

import java.util.Random;

import java.util.Map;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.security.NoSuchAlgorithmException;

import java.util.logging.Level;

/**

  * Implements the CRAM-MD5 SASL server-side mechanism.

  * (<A HREF="http://www.ietf.org/rfc/rfc2195.txt">RFC 2195</A>).

  * CRAM-MD5 has no initial response.

  *

  * client <---- M={random, timestamp, server-fqdn} ------- server

  * client ----- {username HMAC_MD5(pw, M)} --------------> server

  *

  * CallbackHandler must be able to handle the following callbacks:

  * - NameCallback: default name is name of user for whom to get password

  * - PasswordCallback: must fill in password; if empty, no pw

  * - AuthorizeCallback: must setAuthorized() and canonicalized authorization id

  *      - auth id == authzid, but needed to get canonicalized authzid

  *

  * @author Rosanna Lee

  */

final class CramMD5Server extends CramMD5Base implements SaslServer {

    private String fqdn;

    private byte[] challengeData = null;

    private String authzid;

    private CallbackHandler cbh;

    /**

     * Creates a CRAM-MD5 SASL server.

     *

     * @param protocol ignored in CRAM-MD5

     * @param serverFqdn non-null, used in generating a challenge

     * @param props ignored in CRAM-MD5

     * @param cbh find password, authorize user

     */

    CramMD5Server(String protocol, String serverFqdn, Map<String, ?> props,

        CallbackHandler cbh) throws SaslException {

        if (serverFqdn == null) {

            throw new SaslException(

                "CRAM-MD5: fully qualified server name must be specified");

        }

        fqdn = serverFqdn;

        this.cbh = cbh;

    }

    /**

     * Generates challenge based on response sent by client.

     *

     * CRAM-MD5 has no initial response.

     * First call generates challenge.

     * Second call verifies client response. If authentication fails, throws

     * SaslException.

     *

     * @param responseData A non-null byte array containing the response

     *        data from the client.

     * @return A non-null byte array containing the challenge to be sent to

     *        the client for the first call; null when 2nd call is successful.

     * @throws SaslException If authentication fails.

     */

    public byte[] evaluateResponse(byte[] responseData)

        throws SaslException {

        // See if we've been here before

        if (completed) {

            throw new IllegalStateException(

                "CRAM-MD5 authentication already completed");

        }

        if (aborted) {

            throw new IllegalStateException(

                "CRAM-MD5 authentication previously aborted due to error");

        }

        try {

            if (challengeData == null) {

                if (responseData.length != 0) {

                    aborted = true;

                    throw new SaslException(

                        "CRAM-MD5 does not expect any initial response");

                }

                // Generate challenge {random, timestamp, fqdn}

                Random random = new Random();

                long rand = random.nextLong();

                long timestamp = System.currentTimeMillis();

                StringBuilder sb = new StringBuilder();

                sb.append('<');

                sb.append(rand);

                sb.append('.');

                sb.append(timestamp);

                sb.append('@');

                sb.append(fqdn);

                sb.append('>');

                String challengeStr = sb.toString();

                logger.log(Level.FINE,

                    "CRAMSRV01:Generated challenge: {0}", challengeStr);

                challengeData = challengeStr.getBytes("UTF8");

                return challengeData.clone();

            } else {

                // Examine response to see if correctly encrypted challengeData

                if(logger.isLoggable(Level.FINE)) {

                    logger.log(Level.FINE,

                        "CRAMSRV02:Received response: {0}",

                        new String(responseData, "UTF8"));

                }

                // Extract username from response

                int ulen = 0;

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

                    if (responseData[i] == ' ') {

                        ulen = i;

                        break;

                    }

                }

                if (ulen == 0) {

                    aborted = true;

                    throw new SaslException(

                        "CRAM-MD5: Invalid response; space missing");

                }

                String username = new String(responseData, 0, ulen, "UTF8");

                logger.log(Level.FINE,

                    "CRAMSRV03:Extracted username: {0}", username);

                // Get user's password

                NameCallback ncb =

                    new NameCallback("CRAM-MD5 authentication ID: ", username);

                PasswordCallback pcb =

                    new PasswordCallback("CRAM-MD5 password: ", false);

                cbh.handle(new Callback[]{ncb,pcb});

                char[] pwChars = pcb.getPassword();

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

                    // user has no password; OK to disclose to server

                    aborted = true;

                    throw new SaslException(

                        "CRAM-MD5: username not found: " + username);

                }

                pcb.clearPassword();

                String pwStr = new String(pwChars);

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

                    pwChars[i] = 0;

                }

                pw = pwStr.getBytes("UTF8");

                // Generate a keyed-MD5 digest from the user's password and

                // original challenge.

                String digest = HMAC_MD5(pw, challengeData);

                logger.log(Level.FINE,

                    "CRAMSRV04:Expecting digest: {0}", digest);

                // clear pw when we no longer need it

                clearPassword();

                // Check whether digest is as expected

                byte[] expectedDigest = digest.getBytes("UTF8");

                int digestLen = responseData.length - ulen - 1;

                if (expectedDigest.length != digestLen) {

                    aborted = true;

                    throw new SaslException("Invalid response");

                }

                int j = 0;

                for (int i = ulen + 1; i < responseData.length ; i++) {

                    if (expectedDigest[j++] != responseData[i]) {

                        aborted = true;

                        throw new SaslException("Invalid response");

                    }

                }

                // All checks out, use AuthorizeCallback to canonicalize name

                AuthorizeCallback acb = new AuthorizeCallback(username, username);

                cbh.handle(new Callback[]{acb});

                if (acb.isAuthorized()) {

                    authzid = acb.getAuthorizedID();

                } else {

                    // Not authorized

                    aborted = true;

                    throw new SaslException(

                        "CRAM-MD5: user not authorized: " + username);

                }

                logger.log(Level.FINE,

                    "CRAMSRV05:Authorization id: {0}", authzid);

                completed = true;

                return null;

            }

        } catch (UnsupportedEncodingException e) {

            aborted = true;

            throw new SaslException("UTF8 not available on platform", e);

        } catch (NoSuchAlgorithmException e) {

            aborted = true;

            throw new SaslException("MD5 algorithm not available on platform", e);

        } catch (UnsupportedCallbackException e) {

            aborted = true;

            throw new SaslException("CRAM-MD5 authentication failed", e);

        } catch (SaslException e) {

            throw e; // rethrow

        } catch (IOException e) {

            aborted = true;

            throw new SaslException("CRAM-MD5 authentication failed", e);

        }

    }

    public String getAuthorizationID() {

        if (completed) {

            return authzid;

        } else {

            throw new IllegalStateException(

                "CRAM-MD5 authentication not completed");

        }

    }

}