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1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License.
18   *
19   */
20  package org.apache.mina.filter.ssl;
21  
22  import java.net.InetSocketAddress;
23  import java.util.ArrayList;
24  import java.util.List;
25  
26  import javax.net.ssl.SSLContext;
27  import javax.net.ssl.SSLEngine;
28  import javax.net.ssl.SSLException;
29  import javax.net.ssl.SSLHandshakeException;
30  import javax.net.ssl.SSLSession;
31  
32  import org.apache.mina.core.buffer.IoBuffer;
33  import org.apache.mina.core.filterchain.IoFilter;
34  import org.apache.mina.core.filterchain.IoFilterAdapter;
35  import org.apache.mina.core.filterchain.IoFilterChain;
36  import org.apache.mina.core.future.DefaultWriteFuture;
37  import org.apache.mina.core.future.IoFuture;
38  import org.apache.mina.core.future.IoFutureListener;
39  import org.apache.mina.core.future.WriteFuture;
40  import org.apache.mina.core.service.IoAcceptor;
41  import org.apache.mina.core.service.IoHandler;
42  import org.apache.mina.core.session.AttributeKey;
43  import org.apache.mina.core.session.IoSession;
44  import org.apache.mina.core.write.WriteRequest;
45  import org.apache.mina.core.write.WriteRequestWrapper;
46  import org.apache.mina.core.write.WriteToClosedSessionException;
47  import org.slf4j.Logger;
48  import org.slf4j.LoggerFactory;
49  
50  /**
51   * An SSL filter that encrypts and decrypts the data exchanged in the session.
52   * Adding this filter triggers SSL handshake procedure immediately by sending
53   * a SSL 'hello' message, so you don't need to call
54   * {@link #startSsl(IoSession)} manually unless you are implementing StartTLS
55   * (see below).  If you don't want the handshake procedure to start
56   * immediately, please specify {@code false} as {@code autoStart} parameter in
57   * the constructor.
58   * <p>
59   * This filter uses an {@link SSLEngine} which was introduced in Java 5, so
60   * Java version 5 or above is mandatory to use this filter. And please note that
61   * this filter only works for TCP/IP connections.
62   *
63   * <h2>Implementing StartTLS</h2>
64   * <p>
65   * You can use {@link #DISABLE_ENCRYPTION_ONCE} attribute to implement StartTLS:
66   * <pre>
67   * public void messageReceived(IoSession session, Object message) {
68   *    if (message instanceof MyStartTLSRequest) {
69   *        // Insert SSLFilter to get ready for handshaking
70   *        session.getFilterChain().addFirst(sslFilter);
71   *
72   *        // Disable encryption temporarilly.
73   *        // This attribute will be removed by SSLFilter
74   *        // inside the Session.write() call below.
75   *        session.setAttribute(SSLFilter.DISABLE_ENCRYPTION_ONCE, Boolean.TRUE);
76   *
77   *        // Write StartTLSResponse which won't be encrypted.
78   *        session.write(new MyStartTLSResponse(OK));
79   *
80   *        // Now DISABLE_ENCRYPTION_ONCE attribute is cleared.
81   *        assert session.getAttribute(SSLFilter.DISABLE_ENCRYPTION_ONCE) == null;
82   *    }
83   * }
84   * </pre>
85   *
86   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
87   * @org.apache.xbean.XBean
88   */
89  public class SslFilter extends IoFilterAdapter {
90      /** The logger */
91      private static final Logger LOGGER = LoggerFactory.getLogger(SslFilter.class);
92  
93      /**
94       * A session attribute key that stores underlying {@link SSLSession}
95       * for each session.
96       */
97      public static final AttributeKey SSL_SESSION = new AttributeKey(SslFilter.class, "session");
98  
99      /**
100      * A session attribute key that makes next one write request bypass
101      * this filter (not encrypting the data).  This is a marker attribute,
102      * which means that you can put whatever as its value. ({@link Boolean#TRUE}
103      * is preferred.)  The attribute is automatically removed from the session
104      * attribute map as soon as {@link IoSession#write(Object)} is invoked,
105      * and therefore should be put again if you want to make more messages
106      * bypass this filter.  This is especially useful when you implement
107      * StartTLS.
108      */
109     public static final AttributeKey DISABLE_ENCRYPTION_ONCE = new AttributeKey(SslFilter.class, "disableOnce");
110 
111     /**
112      * A session attribute key that makes this filter to emit a
113      * {@link IoHandler#messageReceived(IoSession, Object)} event with a
114      * special message ({@link #SESSION_SECURED} or {@link #SESSION_UNSECURED}).
115      * This is a marker attribute, which means that you can put whatever as its
116      * value. ({@link Boolean#TRUE} is preferred.)  By default, this filter
117      * doesn't emit any events related with SSL session flow control.
118      */
119     public static final AttributeKey USE_NOTIFICATION = new AttributeKey(SslFilter.class, "useNotification");
120 
121     /**
122      * A session attribute key that should be set to an {@link InetSocketAddress}.
123      * Setting this attribute causes
124      * {@link SSLContext#createSSLEngine(String, int)} to be called passing the
125      * hostname and port of the {@link InetSocketAddress} to get an
126      * {@link SSLEngine} instance. If not set {@link SSLContext#createSSLEngine()}
127      * will be called.
128      * <br>
129      * Using this feature {@link SSLSession} objects may be cached and reused
130      * when in client mode.
131      *
132      * @see SSLContext#createSSLEngine(String, int)
133      */
134     public static final AttributeKey PEER_ADDRESS = new AttributeKey(SslFilter.class, "peerAddress");
135 
136     /**
137      * A special message object which is emitted with a {@link IoHandler#messageReceived(IoSession, Object)}
138      * event when the session is secured and its {@link #USE_NOTIFICATION}
139      * attribute is set.
140      */
141     public static final SslFilterMessage SESSION_SECURED = new SslFilterMessage("SESSION_SECURED");
142 
143     /**
144      * A special message object which is emitted with a {@link IoHandler#messageReceived(IoSession, Object)}
145      * event when the session is not secure anymore and its {@link #USE_NOTIFICATION}
146      * attribute is set.
147      */
148     public static final SslFilterMessage SESSION_UNSECURED = new SslFilterMessage("SESSION_UNSECURED");
149 
150     private static final AttributeKey NEXT_FILTER = new AttributeKey(SslFilter.class, "nextFilter");
151 
152     private static final AttributeKey SSL_HANDLER = new AttributeKey(SslFilter.class, "handler");
153 
154     /** The SslContext used */
155     /* No qualifier */final SSLContext sslContext;
156 
157     /** A flag used to tell the filter to start the handshake immediately */
158     private final boolean autoStart;
159 
160     /** A flag used to determinate if the handshake should start immediately */
161     private static final boolean START_HANDSHAKE = true;
162 
163     private boolean client;
164 
165     private boolean needClientAuth;
166 
167     private boolean wantClientAuth;
168 
169     private String[] enabledCipherSuites;
170 
171     private String[] enabledProtocols;
172 
173     /**
174      * Creates a new SSL filter using the specified {@link SSLContext}.
175      * The handshake will start immediately.
176      * 
177      * @param sslContext The SSLContext to use
178      */
179     public SslFilter(SSLContext sslContext) {
180         this(sslContext, START_HANDSHAKE);
181     }
182 
183     /**
184      * Creates a new SSL filter using the specified {@link SSLContext}.
185      * If the <tt>autostart</tt> flag is set to <tt>true</tt>, the
186      * handshake will start immediately.
187      * 
188      * @param sslContext The SSLContext to use
189      * @param autoStart The flag used to tell the filter to start the handshake immediately
190      */
191     public SslFilter(SSLContext sslContext, boolean autoStart) {
192         if (sslContext == null) {
193             throw new IllegalArgumentException("sslContext");
194         }
195 
196         this.sslContext = sslContext;
197         this.autoStart = autoStart;
198     }
199 
200     /**
201      * Returns the underlying {@link SSLSession} for the specified session.
202      *
203      * @param session The current session 
204      * @return <tt>null</tt> if no {@link SSLSession} is initialized yet.
205      */
206     public SSLSession getSslSession(IoSession session) {
207         return (SSLSession) session.getAttribute(SSL_SESSION);
208     }
209 
210     /**
211      * (Re)starts SSL session for the specified <tt>session</tt> if not started yet.
212      * Please note that SSL session is automatically started by default, and therefore
213      * you don't need to call this method unless you've used TLS closure.
214      *
215      * @param session The session that will be switched to SSL mode
216      * @return <tt>true</tt> if the SSL session has been started, <tt>false</tt> if already started.
217      * @throws SSLException if failed to start the SSL session
218      */
219     public boolean startSsl(IoSession session) throws SSLException {
220         SslHandler sslHandler = getSslSessionHandler(session);
221         boolean started;
222 
223         try {
224             synchronized (sslHandler) {
225                 if (sslHandler.isOutboundDone()) {
226                     NextFilter nextFilter = (NextFilter) session.getAttribute(NEXT_FILTER);
227                     sslHandler.destroy();
228                     sslHandler.init();
229                     sslHandler.handshake(nextFilter);
230                     started = true;
231                 } else {
232                     started = false;
233                 }
234             }
235 
236             sslHandler.flushScheduledEvents();
237         } catch (SSLException se) {
238             sslHandler.release();
239             throw se;
240         }
241 
242         return started;
243     }
244 
245     /**
246      * An extended toString() method for sessions. If the SSL handshake
247      * is not yet completed, we will print (ssl) in small caps. Once it's
248      * completed, we will use SSL capitalized.
249      */
250     /* no qualifier */String getSessionInfo(IoSession session) {
251         StringBuilder sb = new StringBuilder();
252 
253         if (session.getService() instanceof IoAcceptor) {
254             sb.append("Session Server");
255 
256         } else {
257             sb.append("Session Client");
258         }
259 
260         sb.append('[').append(session.getId()).append(']');
261 
262         SslHandler sslHandler = (SslHandler) session.getAttribute(SSL_HANDLER);
263 
264         if (sslHandler == null) {
265             sb.append("(no sslEngine)");
266         } else if (isSslStarted(session)) {
267             if (sslHandler.isHandshakeComplete()) {
268                 sb.append("(SSL)");
269             } else {
270                 sb.append("(ssl...)");
271             }
272         }
273 
274         return sb.toString();
275     }
276 
277     /**
278      * @return <tt>true</tt> if and only if the specified <tt>session</tt> is
279      * encrypted/decrypted over SSL/TLS currently. This method will start
280      * to return <tt>false</tt> after TLS <tt>close_notify</tt> message
281      * is sent and any messages written after then is not going to get encrypted.
282      * 
283      * @param session the session we want to check
284      */
285     public boolean isSslStarted(IoSession session) {
286         SslHandler sslHandler = (SslHandler) session.getAttribute(SSL_HANDLER);
287 
288         if (sslHandler == null) {
289             return false;
290         }
291 
292         synchronized (sslHandler) {
293             return !sslHandler.isOutboundDone();
294         }
295     }
296 
297     /**
298      * Stops the SSL session by sending TLS <tt>close_notify</tt> message to
299      * initiate TLS closure.
300      *
301      * @param session the {@link IoSession} to initiate TLS closure
302      * @return The Future for the initiated closure
303      * @throws SSLException if failed to initiate TLS closure
304      */
305     public WriteFuture stopSsl(IoSession session) throws SSLException {
306         SslHandler sslHandler = getSslSessionHandler(session);
307         NextFilter nextFilter = (NextFilter) session.getAttribute(NEXT_FILTER);
308         WriteFuture future;
309 
310         try {
311             synchronized (sslHandler) {
312                 future = initiateClosure(nextFilter, session);
313             }
314 
315             sslHandler.flushScheduledEvents();
316         } catch (SSLException se) {
317             sslHandler.release();
318             throw se;
319         }
320 
321         return future;
322     }
323 
324     /**
325      * @return <tt>true</tt> if the engine is set to use client mode
326      * when handshaking.
327      */
328     public boolean isUseClientMode() {
329         return client;
330     }
331 
332     /**
333      * Configures the engine to use client (or server) mode when handshaking.
334      * 
335      * @param clientMode <tt>true</tt> when we are in client mode, <tt>false</tt> when in server mode
336      */
337     public void setUseClientMode(boolean clientMode) {
338         this.client = clientMode;
339     }
340 
341     /**
342      * @return <tt>true</tt> if the engine will <em>require</em> client authentication.
343      * This option is only useful to engines in the server mode.
344      */
345     public boolean isNeedClientAuth() {
346         return needClientAuth;
347     }
348 
349     /**
350      * Configures the engine to <em>require</em> client authentication.
351      * This option is only useful for engines in the server mode.
352      * 
353      * @param needClientAuth A flag set when we need to authenticate the client
354      */
355     public void setNeedClientAuth(boolean needClientAuth) {
356         this.needClientAuth = needClientAuth;
357     }
358 
359     /**
360      * @return <tt>true</tt> if the engine will <em>request</em> client authentication.
361      * This option is only useful to engines in the server mode.
362      */
363     public boolean isWantClientAuth() {
364         return wantClientAuth;
365     }
366 
367     /**
368      * Configures the engine to <em>request</em> client authentication.
369      * This option is only useful for engines in the server mode.
370      * 
371      * @param wantClientAuth A flag set when we want to check the client authentication
372      */
373     public void setWantClientAuth(boolean wantClientAuth) {
374         this.wantClientAuth = wantClientAuth;
375     }
376 
377     /**
378      * @return the list of cipher suites to be enabled when {@link SSLEngine}
379      * is initialized. <tt>null</tt> means 'use {@link SSLEngine}'s default.'
380      */
381     public String[] getEnabledCipherSuites() {
382         return enabledCipherSuites;
383     }
384 
385     /**
386      * Sets the list of cipher suites to be enabled when {@link SSLEngine}
387      * is initialized.
388      *
389      * @param cipherSuites <tt>null</tt> means 'use {@link SSLEngine}'s default.'
390      */
391     public void setEnabledCipherSuites(String[] cipherSuites) {
392         this.enabledCipherSuites = cipherSuites;
393     }
394 
395     /**
396      * @return the list of protocols to be enabled when {@link SSLEngine}
397      * is initialized. <tt>null</tt> means 'use {@link SSLEngine}'s default.'
398      */
399     public String[] getEnabledProtocols() {
400         return enabledProtocols;
401     }
402 
403     /**
404      * Sets the list of protocols to be enabled when {@link SSLEngine}
405      * is initialized.
406      *
407      * @param protocols <tt>null</tt> means 'use {@link SSLEngine}'s default.'
408      */
409     public void setEnabledProtocols(String[] protocols) {
410         this.enabledProtocols = protocols;
411     }
412 
413     /**
414      * Executed just before the filter is added into the chain, we do :
415      * <ul>
416      * <li>check that we don't have a SSL filter already present
417      * <li>we update the next filter
418      * <li>we create the SSL handler helper class
419      * <li>and we store it into the session's Attributes
420      * </ul>
421      */
422     @Override
423     public void onPreAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws SSLException {
424         // Check that we don't have a SSL filter already present in the chain
425         if (parent.contains(SslFilter.class)) {
426             String msg = "Only one SSL filter is permitted in a chain.";
427             LOGGER.error(msg);
428             throw new IllegalStateException(msg);
429         }
430 
431         LOGGER.debug("Adding the SSL Filter {} to the chain", name);
432 
433         IoSession session = parent.getSession();
434         session.setAttribute(NEXT_FILTER, nextFilter);
435 
436         // Create a SSL handler and start handshake.
437         SslHandler sslHandler = new SslHandler(this, session);
438         sslHandler.init();
439 
440         // Adding the supported ciphers in the SSLHandler
441         // In Java 6, we should call sslContext.getSupportedSSLParameters()
442         // instead
443         String[] ciphers = sslContext.getServerSocketFactory().getSupportedCipherSuites();
444         setEnabledCipherSuites(ciphers);
445         session.setAttribute(SSL_HANDLER, sslHandler);
446     }
447 
448     @Override
449     public void onPostAdd(IoFilterChain parent, String name, NextFilter nextFilter) throws SSLException {
450         if (autoStart == START_HANDSHAKE) {
451             initiateHandshake(nextFilter, parent.getSession());
452         }
453     }
454 
455     @Override
456     public void onPreRemove(IoFilterChain parent, String name, NextFilter nextFilter) throws SSLException {
457         IoSession session = parent.getSession();
458         stopSsl(session);
459         session.removeAttribute(NEXT_FILTER);
460         session.removeAttribute(SSL_HANDLER);
461     }
462 
463     // IoFilter impl.
464     @Override
465     public void sessionClosed(NextFilter nextFilter, IoSession session) throws SSLException {
466         SslHandler sslHandler = getSslSessionHandler(session);
467 
468         try {
469             synchronized (sslHandler) {
470                 // release resources
471                 sslHandler.destroy();
472             }
473 
474             sslHandler.flushScheduledEvents();
475         } finally {
476             // notify closed session
477             nextFilter.sessionClosed(session);
478         }
479     }
480 
481     @Override
482     public void messageReceived(NextFilter nextFilter, IoSession session, Object message) throws SSLException {
483         if (LOGGER.isDebugEnabled()) {
484             LOGGER.debug("{}: Message received : {}", getSessionInfo(session), message);
485         }
486 
487         SslHandler sslHandler = getSslSessionHandler(session);
488 
489         synchronized (sslHandler) {
490             if (!isSslStarted(session) && sslHandler.isInboundDone()) {
491                 // The SSL session must be established first before we
492                 // can push data to the application. Store the incoming
493                 // data into a queue for a later processing
494                 sslHandler.scheduleMessageReceived(nextFilter, message);
495             } else {
496                 IoBuffer buf = (IoBuffer) message;
497 
498                 try {
499                     // forward read encrypted data to SSL handler
500                     sslHandler.messageReceived(nextFilter, buf.buf());
501 
502                     // Handle data to be forwarded to application or written to net
503                     handleSslData(nextFilter, sslHandler);
504 
505                     if (sslHandler.isInboundDone()) {
506                         if (sslHandler.isOutboundDone()) {
507                             sslHandler.destroy();
508                         } else {
509                             initiateClosure(nextFilter, session);
510                         }
511 
512                         if (buf.hasRemaining()) {
513                             // Forward the data received after closure.
514                             sslHandler.scheduleMessageReceived(nextFilter, buf);
515                         }
516                     }
517                 } catch (SSLException ssle) {
518                     if (!sslHandler.isHandshakeComplete()) {
519                         SSLException newSsle = new SSLHandshakeException("SSL handshake failed.");
520                         newSsle.initCause(ssle);
521                         ssle = newSsle;
522                     } else {
523                         // Free the SSL Handler buffers
524                         sslHandler.release();
525                     }
526 
527                     throw ssle;
528                 }
529             }
530         }
531 
532         sslHandler.flushScheduledEvents();
533     }
534 
535     @Override
536     public void messageSent(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) {
537         if (writeRequest instanceof EncryptedWriteRequest) {
538             EncryptedWriteRequest wrappedRequest = (EncryptedWriteRequest) writeRequest;
539             nextFilter.messageSent(session, wrappedRequest.getParentRequest());
540         } else {
541             // ignore extra buffers used for handshaking
542         }
543     }
544 
545     @Override
546     public void exceptionCaught(NextFilter nextFilter, IoSession session, Throwable cause) throws Exception {
547 
548         if (cause instanceof WriteToClosedSessionException) {
549             // Filter out SSL close notify, which is likely to fail to flush
550             // due to disconnection.
551             WriteToClosedSessionException e = (WriteToClosedSessionException) cause;
552             List<WriteRequest> failedRequests = e.getRequests();
553             boolean containsCloseNotify = false;
554 
555             for (WriteRequest r : failedRequests) {
556                 if (isCloseNotify(r.getMessage())) {
557                     containsCloseNotify = true;
558                     break;
559                 }
560             }
561 
562             if (containsCloseNotify) {
563                 if (failedRequests.size() == 1) {
564                     // close notify is the only failed request; bail out.
565                     return;
566                 }
567 
568                 List<WriteRequest> newFailedRequests = new ArrayList<WriteRequest>(failedRequests.size() - 1);
569 
570                 for (WriteRequest r : failedRequests) {
571                     if (!isCloseNotify(r.getMessage())) {
572                         newFailedRequests.add(r);
573                     }
574                 }
575 
576                 if (newFailedRequests.isEmpty()) {
577                     // the failedRequests were full with close notify; bail out.
578                     return;
579                 }
580 
581                 cause = new WriteToClosedSessionException(newFailedRequests, cause.getMessage(), cause.getCause());
582             }
583         }
584 
585         nextFilter.exceptionCaught(session, cause);
586     }
587 
588     private boolean isCloseNotify(Object message) {
589         if (!(message instanceof IoBuffer)) {
590             return false;
591         }
592 
593         IoBuffer buf = (IoBuffer) message;
594         int offset = buf.position();
595 
596         return (buf.get(offset + 0) == 0x15) /* Alert */
597                 && (buf.get(offset + 1) == 0x03) /* TLS/SSL */
598                 && ((buf.get(offset + 2) == 0x00) /* SSL 3.0 */
599                         || (buf.get(offset + 2) == 0x01) /* TLS 1.0 */
600                         || (buf.get(offset + 2) == 0x02) /* TLS 1.1 */
601                         || (buf.get(offset + 2) == 0x03)) /* TLS 1.2 */
602                         && (buf.get(offset + 3) == 0x00); /* close_notify */
603     }
604 
605     @Override
606     public void filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws SSLException {
607         if (LOGGER.isDebugEnabled()) {
608             LOGGER.debug("{}: Writing Message : {}", getSessionInfo(session), writeRequest);
609         }
610 
611         boolean needsFlush = true;
612         SslHandler sslHandler = getSslSessionHandler(session);
613 
614         try {
615             synchronized (sslHandler) {
616                 if (!isSslStarted(session)) {
617                     sslHandler.scheduleFilterWrite(nextFilter, writeRequest);
618                 }
619                 // Don't encrypt the data if encryption is disabled.
620                 else if (session.containsAttribute(DISABLE_ENCRYPTION_ONCE)) {
621                     // Remove the marker attribute because it is temporary.
622                     session.removeAttribute(DISABLE_ENCRYPTION_ONCE);
623                     sslHandler.scheduleFilterWrite(nextFilter, writeRequest);
624                 } else {
625                     // Otherwise, encrypt the buffer.
626                     IoBuffer buf = (IoBuffer) writeRequest.getMessage();
627 
628                     if (sslHandler.isWritingEncryptedData()) {
629                         // data already encrypted; simply return buffer
630                         sslHandler.scheduleFilterWrite(nextFilter, writeRequest);
631                     } else if (sslHandler.isHandshakeComplete()) {
632                         // SSL encrypt
633                         int pos = buf.position();
634                         sslHandler.encrypt(buf.buf());
635                         buf.position(pos);
636                         IoBuffer encryptedBuffer = sslHandler.fetchOutNetBuffer();
637                         sslHandler.scheduleFilterWrite(nextFilter, new EncryptedWriteRequest(writeRequest,
638                                 encryptedBuffer));
639                     } else {
640                         if (session.isConnected()) {
641                             // Handshake not complete yet.
642                             sslHandler.schedulePreHandshakeWriteRequest(nextFilter, writeRequest);
643                         }
644 
645                         needsFlush = false;
646                     }
647                 }
648             }
649 
650             if (needsFlush) {
651                 sslHandler.flushScheduledEvents();
652             }
653         } catch (SSLException se) {
654             sslHandler.release();
655             throw se;
656         }
657     }
658 
659     @Override
660     public void filterClose(final NextFilter nextFilter, final IoSession session) throws SSLException {
661         SslHandler sslHandler = (SslHandler) session.getAttribute(SSL_HANDLER);
662 
663         if (sslHandler == null) {
664             // The connection might already have closed, or
665             // SSL might have not started yet.
666             nextFilter.filterClose(session);
667             return;
668         }
669 
670         WriteFuture future = null;
671 
672         try {
673             synchronized (sslHandler) {
674                 if (isSslStarted(session)) {
675                     future = initiateClosure(nextFilter, session);
676                     future.addListener(new IoFutureListener<IoFuture>() {
677                         public void operationComplete(IoFuture future) {
678                             nextFilter.filterClose(session);
679                         }
680                     });
681                 }
682             }
683 
684             sslHandler.flushScheduledEvents();
685         } catch (SSLException se) {
686             sslHandler.release();
687             throw se;
688         } finally {
689             if (future == null) {
690                 nextFilter.filterClose(session);
691             }
692         }
693     }
694 
695     /**
696      * Initiate the SSL handshake. This can be invoked if you have set the 'autoStart' to
697      * false when creating the SslFilter instance.
698      * 
699      * @param session The session for which the SSL handshake should be done
700      * @throws SSLException If the handshake failed
701      */
702     public void initiateHandshake(IoSession session) throws SSLException {
703         IoFilterChain filterChain = session.getFilterChain();
704         
705         if (filterChain == null) {
706             throw new SSLException("No filter chain");
707         }
708         
709         IoFilter.NextFilter nextFilter = filterChain.getNextFilter(SslFilter.class);
710         
711         if (nextFilter == null) {
712             throw new SSLException("No SSL next filter in the chain");
713         }
714         
715         initiateHandshake(nextFilter, session);
716     }
717 
718     private void initiateHandshake(NextFilter nextFilter, IoSession session) throws SSLException {
719         LOGGER.debug("{} : Starting the first handshake", getSessionInfo(session));
720         SslHandler sslHandler = getSslSessionHandler(session);
721 
722         try {
723             synchronized (sslHandler) {
724                 sslHandler.handshake(nextFilter);
725             }
726 
727             sslHandler.flushScheduledEvents();
728         } catch (SSLException se) {
729             sslHandler.release();
730             throw se;
731         }
732     }
733 
734     private WriteFuture initiateClosure(NextFilter nextFilter, IoSession session) throws SSLException {
735         SslHandler sslHandler = getSslSessionHandler(session);
736         WriteFuture future = null;
737 
738         // if already shut down
739         try {
740             if (!sslHandler.closeOutbound()) {
741                 return DefaultWriteFuture.newNotWrittenFuture(session, new IllegalStateException(
742                         "SSL session is shut down already."));
743             }
744 
745             // there might be data to write out here?
746             future = sslHandler.writeNetBuffer(nextFilter);
747 
748             if (future == null) {
749                 future = DefaultWriteFuture.newWrittenFuture(session);
750             }
751 
752             if (sslHandler.isInboundDone()) {
753                 sslHandler.destroy();
754             }
755 
756             if (session.containsAttribute(USE_NOTIFICATION)) {
757                 sslHandler.scheduleMessageReceived(nextFilter, SESSION_UNSECURED);
758             }
759         } catch (SSLException se) {
760             sslHandler.release();
761             throw se;
762         }
763 
764         return future;
765     }
766 
767     // Utilities
768     private void handleSslData(NextFilter nextFilter, SslHandler sslHandler) throws SSLException {
769         if (LOGGER.isDebugEnabled()) {
770             LOGGER.debug("{}: Processing the SSL Data ", getSessionInfo(sslHandler.getSession()));
771         }
772 
773         // Flush any buffered write requests occurred before handshaking.
774         if (sslHandler.isHandshakeComplete()) {
775             sslHandler.flushPreHandshakeEvents();
776         }
777 
778         // Write encrypted data to be written (if any)
779         sslHandler.writeNetBuffer(nextFilter);
780 
781         // handle app. data read (if any)
782         handleAppDataRead(nextFilter, sslHandler);
783     }
784 
785     private void handleAppDataRead(NextFilter nextFilter, SslHandler sslHandler) {
786         // forward read app data
787         IoBuffer readBuffer = sslHandler.fetchAppBuffer();
788 
789         if (readBuffer.hasRemaining()) {
790             sslHandler.scheduleMessageReceived(nextFilter, readBuffer);
791         }
792     }
793 
794     private SslHandler getSslSessionHandler(IoSession session) {
795         SslHandler sslHandler = (SslHandler) session.getAttribute(SSL_HANDLER);
796 
797         if (sslHandler == null) {
798             throw new IllegalStateException();
799         }
800 
801         if (sslHandler.getSslFilter() != this) {
802             throw new IllegalArgumentException("Not managed by this filter.");
803         }
804 
805         return sslHandler;
806     }
807 
808     /**
809      * A message that is sent from {@link SslFilter} when the connection became
810      * secure or is not secure anymore.
811      *
812      * @author <a href="http://mina.apache.org">Apache MINA Project</a>
813      */
814     public static class SslFilterMessage {
815         private final String name;
816 
817         private SslFilterMessage(String name) {
818             this.name = name;
819         }
820 
821         @Override
822         public String toString() {
823             return name;
824         }
825     }
826 
827     private static class EncryptedWriteRequest extends WriteRequestWrapper {
828         private final IoBuffer encryptedMessage;
829 
830         private EncryptedWriteRequest(WriteRequest writeRequest, IoBuffer encryptedMessage) {
831             super(writeRequest);
832             this.encryptedMessage = encryptedMessage;
833         }
834 
835         @Override
836         public Object getMessage() {
837             return encryptedMessage;
838         }
839     }
840 }