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	/*
	* 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();

	StringBuffer buf = new StringBuffer();
	buf.append('<');
	buf.append(rand);
	buf.append('.');
	buf.append(timestamp);
	buf.append('@');
	buf.append(fqdn);
	buf.append('>');
	String challengeStr = buf.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");
	}
	}
	}

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