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Java example source code file (GssKrb5Client.java)

This example Java source code file (GssKrb5Client.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

byte, empty, failure, gsscredential, gssexception, gsskrb5client, integer, krb5_oid, krb5clnt08\:selected, log, logging, messageprop, my_class_name, object, saslexception, string, util

The GssKrb5Client.java Java example source code

/*
 * Copyright (c) 2000, 2013, 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.gsskerb;

import java.io.IOException;
import java.util.Map;
import java.util.logging.Level;
import javax.security.sasl.*;

// JAAS
import javax.security.auth.callback.CallbackHandler;

// JGSS
import org.ietf.jgss.*;

/**
  * Implements the GSSAPI SASL client mechanism for Kerberos V5.
  * (<A HREF="http://www.ietf.org/rfc/rfc2222.txt">RFC 2222,
  * <a HREF="http://www.ietf.org/internet-drafts/draft-ietf-cat-sasl-gssapi-04.txt">draft-ietf-cat-sasl-gssapi-04.txt).
  * It uses the Java Bindings for GSSAPI
  * (<A HREF="http://www.ietf.org/rfc/rfc2853.txt">RFC 2853)
  * for getting GSSAPI/Kerberos V5 support.
  *
  * The client/server interactions are:
  * C0: bind (GSSAPI, initial response)
  * S0: sasl-bind-in-progress, challenge 1 (output of accept_sec_context or [])
  * C1: bind (GSSAPI, response 1 (output of init_sec_context or []))
  * S1: sasl-bind-in-progress challenge 2 (security layer, server max recv size)
  * C2: bind (GSSAPI, response 2 (security layer, client max recv size, authzid))
  * S2: bind success response
  *
  * Expects the client's credentials to be supplied from the
  * javax.security.sasl.credentials property or from the thread's Subject.
  * Otherwise the underlying KRB5 mech will attempt to acquire Kerberos creds
  * by logging into Kerberos (via default TextCallbackHandler).
  * These creds will be used for exchange with server.
  *
  * Required callbacks: none.
  *
  * Environment properties that affect behavior of implementation:
  *
  * javax.security.sasl.qop
  * - quality of protection; list of auth, auth-int, auth-conf; default is "auth"
  * javax.security.sasl.maxbuf
  * - max receive buffer size; default is 65536
  * javax.security.sasl.sendmaxbuffer
  * - max send buffer size; default is 65536; (min with server max recv size)
  *
  * javax.security.sasl.server.authentication
  * - "true" means require mutual authentication; default is "false"
  *
  * javax.security.sasl.credentials
  * - an {@link org.ietf.jgss.GSSCredential} used for delegated authentication.
  *
  * @author Rosanna Lee
  */

final class GssKrb5Client extends GssKrb5Base implements SaslClient {
    // ---------------- Constants -----------------
    private static final String MY_CLASS_NAME = GssKrb5Client.class.getName();

    private boolean finalHandshake = false;
    private boolean mutual = false;       // default false
    private byte[] authzID;

    /**
     * Creates a SASL mechanism with client credentials that it needs
     * to participate in GSS-API/Kerberos v5 authentication exchange
     * with the server.
     */
    GssKrb5Client(String authzID, String protocol, String serverName,
        Map<String, ?> props, CallbackHandler cbh) throws SaslException {

        super(props, MY_CLASS_NAME);

        String service = protocol + "@" + serverName;
        logger.log(Level.FINE, "KRB5CLNT01:Requesting service name: {0}",
            service);

        try {
            GSSManager mgr = GSSManager.getInstance();

            // Create the name for the requested service entity for Krb5 mech
            GSSName acceptorName = mgr.createName(service,
                GSSName.NT_HOSTBASED_SERVICE, KRB5_OID);

            // Parse properties to check for supplied credentials
            GSSCredential credentials = null;
            if (props != null) {
                Object prop = props.get(Sasl.CREDENTIALS);
                if (prop != null && prop instanceof GSSCredential) {
                    credentials = (GSSCredential) prop;
                    logger.log(Level.FINE,
                        "KRB5CLNT01:Using the credentials supplied in " +
                        "javax.security.sasl.credentials");
                }
            }

            // Create a context using credentials for Krb5 mech
            secCtx = mgr.createContext(acceptorName,
                KRB5_OID,   /* mechanism */
                credentials, /* credentials */
                GSSContext.INDEFINITE_LIFETIME);

            // Request credential delegation when credentials have been supplied
            if (credentials != null) {
                secCtx.requestCredDeleg(true);
            }

            // Parse properties  to set desired context options
            if (props != null) {
                // Mutual authentication
                String prop = (String)props.get(Sasl.SERVER_AUTH);
                if (prop != null) {
                    mutual = "true".equalsIgnoreCase(prop);
                }
            }
            secCtx.requestMutualAuth(mutual);

            // Always specify potential need for integrity and confidentiality
            // Decision will be made during final handshake
            secCtx.requestConf(true);
            secCtx.requestInteg(true);

        } catch (GSSException e) {
            throw new SaslException("Failure to initialize security context", e);
        }

        if (authzID != null && authzID.length() > 0) {
            try {
                this.authzID = authzID.getBytes("UTF8");
            } catch (IOException e) {
                throw new SaslException("Cannot encode authorization ID", e);
            }
        }
    }

    public boolean hasInitialResponse() {
        return true;
    }

    /**
     * Processes the challenge data.
     *
     * The server sends a challenge data using which the client must
     * process using GSS_Init_sec_context.
     * As per RFC 2222, when GSS_S_COMPLETE is returned, we do
     * an extra handshake to determine the negotiated security protection
     * and buffer sizes.
     *
     * @param challengeData A non-null byte array containing the
     * challenge data from the server.
     * @return A non-null byte array containing the response to be
     * sent to the server.
     */
    public byte[] evaluateChallenge(byte[] challengeData) throws SaslException {
        if (completed) {
            throw new IllegalStateException(
                "GSSAPI authentication already complete");
        }

        if (finalHandshake) {
            return doFinalHandshake(challengeData);
        } else {

            // Security context not established yet; continue with init

            try {
                byte[] gssOutToken = secCtx.initSecContext(challengeData,
                    0, challengeData.length);
                if (logger.isLoggable(Level.FINER)) {
                    traceOutput(MY_CLASS_NAME, "evaluteChallenge",
                        "KRB5CLNT02:Challenge: [raw]", challengeData);
                    traceOutput(MY_CLASS_NAME, "evaluateChallenge",
                        "KRB5CLNT03:Response: [after initSecCtx]", gssOutToken);
                }

                if (secCtx.isEstablished()) {
                    finalHandshake = true;
                    if (gssOutToken == null) {
                        // RFC 2222 7.2.1:  Client responds with no data
                        return EMPTY;
                    }
                }

                return gssOutToken;
            } catch (GSSException e) {
                throw new SaslException("GSS initiate failed", e);
            }
        }
    }

    private byte[] doFinalHandshake(byte[] challengeData) throws SaslException {
        try {
            // Security context already established. challengeData
            // should contain security layers and server's maximum buffer size

            if (logger.isLoggable(Level.FINER)) {
                traceOutput(MY_CLASS_NAME, "doFinalHandshake",
                    "KRB5CLNT04:Challenge [raw]:", challengeData);
            }

            if (challengeData.length == 0) {
                // Received S0, should return []
                return EMPTY;
            }

            // Received S1 (security layer, server max recv size)

            byte[] gssOutToken = secCtx.unwrap(challengeData, 0,
                challengeData.length, new MessageProp(0, false));

            // First octet is a bit-mask specifying the protections
            // supported by the server
            if (logger.isLoggable(Level.FINE)) {
                if (logger.isLoggable(Level.FINER)) {
                    traceOutput(MY_CLASS_NAME, "doFinalHandshake",
                        "KRB5CLNT05:Challenge [unwrapped]:", gssOutToken);
                }
                logger.log(Level.FINE, "KRB5CLNT06:Server protections: {0}",
                    new Byte(gssOutToken[0]));
            }

            // Client selects preferred protection
            // qop is ordered list of qop values
            byte selectedQop = findPreferredMask(gssOutToken[0], qop);
            if (selectedQop == 0) {
                throw new SaslException(
                    "No common protection layer between client and server");
            }

            if ((selectedQop&PRIVACY_PROTECTION) != 0) {
                privacy = true;
                integrity = true;
            } else if ((selectedQop&INTEGRITY_ONLY_PROTECTION) != 0) {
                integrity = true;
            }

            // 2nd-4th octets specifies maximum buffer size expected by
            // server (in network byte order)
            int srvMaxBufSize = networkByteOrderToInt(gssOutToken, 1, 3);

            // Determine the max send buffer size based on what the
            // server is able to receive and our specified max
            sendMaxBufSize = (sendMaxBufSize == 0) ? srvMaxBufSize :
                Math.min(sendMaxBufSize, srvMaxBufSize);

            // Update context to limit size of returned buffer
            rawSendSize = secCtx.getWrapSizeLimit(JGSS_QOP, privacy,
                sendMaxBufSize);

            if (logger.isLoggable(Level.FINE)) {
                logger.log(Level.FINE,
"KRB5CLNT07:Client max recv size: {0}; server max recv size: {1}; rawSendSize: {2}",
                    new Object[] {new Integer(recvMaxBufSize),
                                  new Integer(srvMaxBufSize),
                                  new Integer(rawSendSize)});
            }

            // Construct negotiated security layers and client's max
            // receive buffer size and authzID
            int len = 4;
            if (authzID != null) {
                len += authzID.length;
            }

            byte[] gssInToken = new byte[len];
            gssInToken[0] = selectedQop;

            if (logger.isLoggable(Level.FINE)) {
                logger.log(Level.FINE,
            "KRB5CLNT08:Selected protection: {0}; privacy: {1}; integrity: {2}",
                    new Object[]{new Byte(selectedQop),
                                 Boolean.valueOf(privacy),
                                 Boolean.valueOf(integrity)});
            }

            intToNetworkByteOrder(recvMaxBufSize, gssInToken, 1, 3);
            if (authzID != null) {
                // copy authorization id
                System.arraycopy(authzID, 0, gssInToken, 4, authzID.length);
                logger.log(Level.FINE, "KRB5CLNT09:Authzid: {0}", authzID);
            }

            if (logger.isLoggable(Level.FINER)) {
                traceOutput(MY_CLASS_NAME, "doFinalHandshake",
                    "KRB5CLNT10:Response [raw]", gssInToken);
            }

            gssOutToken = secCtx.wrap(gssInToken,
                0, gssInToken.length,
                new MessageProp(0 /* qop */, false /* privacy */));

            if (logger.isLoggable(Level.FINER)) {
                traceOutput(MY_CLASS_NAME, "doFinalHandshake",
                    "KRB5CLNT11:Response [after wrap]", gssOutToken);
            }

            completed = true;  // server authenticated

            return gssOutToken;
        } catch (GSSException e) {
            throw new SaslException("Final handshake failed", e);
        }
    }
}

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