/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project licenses this file to you under the Apache License,
    * version 2.0 (the "License"); you may not use this file except in compliance
    * with the License. You may obtain a copy of the License at:
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
    *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   */
  package org.jboss.netty.handler.ssl;
  
  import org.jboss.netty.buffer.ChannelBuffer;
  import org.jboss.netty.buffer.ChannelBuffers;
  import org.jboss.netty.channel.Channel;
  import org.jboss.netty.channel.ChannelDownstreamHandler;
  import org.jboss.netty.channel.ChannelEvent;
  import org.jboss.netty.channel.ChannelFuture;
  import org.jboss.netty.channel.ChannelFutureListener;
  import org.jboss.netty.channel.ChannelHandlerContext;
  import org.jboss.netty.channel.ChannelPipeline;
  import org.jboss.netty.channel.ChannelStateEvent;
  import org.jboss.netty.channel.Channels;
  import org.jboss.netty.channel.DefaultChannelFuture;
  import org.jboss.netty.channel.DownstreamMessageEvent;
  import org.jboss.netty.channel.ExceptionEvent;
  import org.jboss.netty.channel.MessageEvent;
  import org.jboss.netty.handler.codec.frame.FrameDecoder;
  import org.jboss.netty.logging.InternalLogger;
  import org.jboss.netty.logging.InternalLoggerFactory;
  import org.jboss.netty.util.internal.DetectionUtil;
  import org.jboss.netty.util.internal.NonReentrantLock;
  
  import javax.net.ssl.SSLEngine;
  import javax.net.ssl.SSLEngineResult;
  import javax.net.ssl.SSLEngineResult.HandshakeStatus;
  import javax.net.ssl.SSLEngineResult.Status;
  import javax.net.ssl.SSLException;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.ClosedChannelException;
  import java.nio.channels.DatagramChannel;
  import java.nio.channels.SocketChannel;
  import java.util.LinkedList;
  import java.util.Queue;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.Executor;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.regex.Pattern;
  
  import static org.jboss.netty.channel.Channels.*;
  
  /**
   * Adds <a href="http://en.wikipedia.org/wiki/Transport_Layer_Security">SSL
   * &middot; TLS</a> and StartTLS support to a {@link Channel}.  Please refer
   * to the <strong>"SecureChat"</strong> example in the distribution or the web
   * site for the detailed usage.
   *
   * <h3>Beginning the handshake</h3>
   * <p>
   * You must make sure not to write a message while the
   * {@linkplain #handshake() handshake} is in progress unless you are
   * renegotiating.  You will be notified by the {@link ChannelFuture} which is
   * returned by the {@link #handshake()} method when the handshake
   * process succeeds or fails.
   *
   * <h3>Handshake</h3>
   * <p>
   * If {@link #isIssueHandshake()} is {@code false}
   * (default) you will need to take care of calling {@link #handshake()} by your own. In most
   * situations were {@link SslHandler} is used in 'client mode' you want to issue a handshake once
   * the connection was established. if {@link #setIssueHandshake(boolean)} is set to <code>true</code>
   * you don't need to worry about this as the {@link SslHandler} will take care of it.
   * <p>
   *
   * <h3>Renegotiation</h3>
   * <p>
   * If {@link #isEnableRenegotiation() enableRenegotiation} is {@code true}
   * (default) and the initial handshake has been done successfully, you can call
   * {@link #handshake()} to trigger the renegotiation.
   * <p>
   * If {@link #isEnableRenegotiation() enableRenegotiation} is {@code false},
   * an attempt to trigger renegotiation will result in the connection closure.
   * <p>
   * Please note that TLS renegotiation had a security issue before.  If your
   * runtime environment did not fix it, please make sure to disable TLS
   * renegotiation by calling {@link #setEnableRenegotiation(boolean)} with
   * {@code false}.  For more information, please refer to the following documents:
   * <ul>
   *   <li><a href="http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2009-3555">CVE-2009-3555</a></li>
   *   <li><a href="http://www.ietf.org/rfc/rfc5746.txt">RFC5746</a></li>
   *   <li><a href="http://www.oracle.com/technetwork/java/javase/documentation/tlsreadme2-176330.html">Phased
   *       Approach to Fixing the TLS Renegotiation Issue</a></li>
   * </ul>
  *
  * <h3>Closing the session</h3>
  * <p>
  * To close the SSL session, the {@link #close()} method should be
  * called to send the {@code close_notify} message to the remote peer.  One
  * exception is when you close the {@link Channel} - {@link SslHandler}
  * intercepts the close request and send the {@code close_notify} message
  * before the channel closure automatically.  Once the SSL session is closed,
  * it is not reusable, and consequently you should create a new
  * {@link SslHandler} with a new {@link SSLEngine} as explained in the
  * following section.
  *
  * <h3>Restarting the session</h3>
  * <p>
  * To restart the SSL session, you must remove the existing closed
  * {@link SslHandler} from the {@link ChannelPipeline}, insert a new
  * {@link SslHandler} with a new {@link SSLEngine} into the pipeline,
  * and start the handshake process as described in the first section.
  *
  * <h3>Implementing StartTLS</h3>
  * <p>
  * <a href="http://en.wikipedia.org/wiki/STARTTLS">StartTLS</a> is the
  * communication pattern that secures the wire in the middle of the plaintext
  * connection.  Please note that it is different from SSL &middot; TLS, that
  * secures the wire from the beginning of the connection.  Typically, StartTLS
  * is composed of three steps:
  * <ol>
  * <li>Client sends a StartTLS request to server.</li>
  * <li>Server sends a StartTLS response to client.</li>
  * <li>Client begins SSL handshake.</li>
  * </ol>
  * If you implement a server, you need to:
  * <ol>
  * <li>create a new {@link SslHandler} instance with {@code startTls} flag set
  *     to {@code true},</li>
  * <li>insert the {@link SslHandler} to the {@link ChannelPipeline}, and</li>
  * <li>write a StartTLS response.</li>
  * </ol>
  * Please note that you must insert {@link SslHandler} <em>before</em> sending
  * the StartTLS response.  Otherwise the client can send begin SSL handshake
  * before {@link SslHandler} is inserted to the {@link ChannelPipeline}, causing
  * data corruption.
  * <p>
  * The client-side implementation is much simpler.
  * <ol>
  * <li>Write a StartTLS request,</li>
  * <li>wait for the StartTLS response,</li>
  * <li>create a new {@link SslHandler} instance with {@code startTls} flag set
  *     to {@code false},</li>
  * <li>insert the {@link SslHandler} to the {@link ChannelPipeline}, and</li>
  * <li>Initiate SSL handshake by calling {@link SslHandler#handshake()}.</li>
  * </ol>
  *
  * @apiviz.landmark
  * @apiviz.uses org.jboss.netty.handler.ssl.SslBufferPool
  */
 public class SslHandler extends FrameDecoder
                         implements ChannelDownstreamHandler {
 
     private static final InternalLogger logger =
         InternalLoggerFactory.getInstance(SslHandler.class);
 
     private static final ByteBuffer EMPTY_BUFFER = ByteBuffer.allocate(0);
 
     private static final Pattern IGNORABLE_CLASS_IN_STACK = Pattern.compile(
             "^.*(Socket|DatagramChannel|SctpChannel).*$");
     private static final Pattern IGNORABLE_ERROR_MESSAGE = Pattern.compile(
             "^.*(?:connection.*reset|connection.*closed|broken.*pipe).*$",
             Pattern.CASE_INSENSITIVE);
 
     private static SslBufferPool defaultBufferPool;
 
     /**
      * Returns the default {@link SslBufferPool} used when no pool is
      * specified in the constructor.
      */
     public static synchronized SslBufferPool getDefaultBufferPool() {
         if (defaultBufferPool == null) {
             defaultBufferPool = new SslBufferPool();
         }
         return defaultBufferPool;
     }
 
     private volatile ChannelHandlerContext ctx;
     private final SSLEngine engine;
     private final SslBufferPool bufferPool;
     private final Executor delegatedTaskExecutor;
     private final boolean startTls;
 
     private volatile boolean enableRenegotiation = true;
 
     final Object handshakeLock = new Object();
     private boolean handshaking;
     private volatile boolean handshaken;
     private volatile ChannelFuture handshakeFuture;
 
     private final AtomicBoolean sentFirstMessage = new AtomicBoolean();
     private final AtomicBoolean sentCloseNotify = new AtomicBoolean();
     int ignoreClosedChannelException;
     final Object ignoreClosedChannelExceptionLock = new Object();
     private final Queue<PendingWrite> pendingUnencryptedWrites = new LinkedList<PendingWrite>();
     private final Queue<MessageEvent> pendingEncryptedWrites = new ConcurrentLinkedQueue<MessageEvent>();
     private final NonReentrantLock pendingEncryptedWritesLock = new NonReentrantLock();
 
     private volatile boolean issueHandshake;
 
     private final SSLEngineInboundCloseFuture sslEngineCloseFuture = new SSLEngineInboundCloseFuture();
 
     private boolean closeOnSSLException;
 
     private int packetLength = Integer.MIN_VALUE;
 
     /**
      * Creates a new instance.
      *
      * @param engine  the {@link SSLEngine} this handler will use
      */
     public SslHandler(SSLEngine engine) {
         this(engine, getDefaultBufferPool(), ImmediateExecutor.INSTANCE);
     }
 
     /**
      * Creates a new instance.
      *
      * @param engine      the {@link SSLEngine} this handler will use
      * @param bufferPool  the {@link SslBufferPool} where this handler will
      *                    acquire the buffers required by the {@link SSLEngine}
      */
     public SslHandler(SSLEngine engine, SslBufferPool bufferPool) {
         this(engine, bufferPool, ImmediateExecutor.INSTANCE);
     }
 
     /**
      * Creates a new instance.
      *
      * @param engine    the {@link SSLEngine} this handler will use
      * @param startTls  {@code true} if the first write request shouldn't be
      *                  encrypted by the {@link SSLEngine}
      */
     public SslHandler(SSLEngine engine, boolean startTls) {
         this(engine, getDefaultBufferPool(), startTls);
     }
 
     /**
      * Creates a new instance.
      *
      * @param engine      the {@link SSLEngine} this handler will use
      * @param bufferPool  the {@link SslBufferPool} where this handler will
      *                    acquire the buffers required by the {@link SSLEngine}
      * @param startTls    {@code true} if the first write request shouldn't be
      *                    encrypted by the {@link SSLEngine}
      */
     public SslHandler(SSLEngine engine, SslBufferPool bufferPool, boolean startTls) {
         this(engine, bufferPool, startTls, ImmediateExecutor.INSTANCE);
     }
 
     /**
      * Creates a new instance.
      *
      * @param engine
      *        the {@link SSLEngine} this handler will use
      * @param delegatedTaskExecutor
      *        the {@link Executor} which will execute the delegated task
      *        that {@link SSLEngine#getDelegatedTask()} will return
      */
     public SslHandler(SSLEngine engine, Executor delegatedTaskExecutor) {
         this(engine, getDefaultBufferPool(), delegatedTaskExecutor);
     }
 
     /**
      * Creates a new instance.
      *
      * @param engine
      *        the {@link SSLEngine} this handler will use
      * @param bufferPool
      *        the {@link SslBufferPool} where this handler will acquire
      *        the buffers required by the {@link SSLEngine}
      * @param delegatedTaskExecutor
      *        the {@link Executor} which will execute the delegated task
      *        that {@link SSLEngine#getDelegatedTask()} will return
      */
     public SslHandler(SSLEngine engine, SslBufferPool bufferPool, Executor delegatedTaskExecutor) {
         this(engine, bufferPool, false, delegatedTaskExecutor);
     }
 
     /**
      * Creates a new instance.
      *
      * @param engine
      *        the {@link SSLEngine} this handler will use
      * @param startTls
      *        {@code true} if the first write request shouldn't be encrypted
      *        by the {@link SSLEngine}
      * @param delegatedTaskExecutor
      *        the {@link Executor} which will execute the delegated task
      *        that {@link SSLEngine#getDelegatedTask()} will return
      */
     public SslHandler(SSLEngine engine, boolean startTls, Executor delegatedTaskExecutor) {
         this(engine, getDefaultBufferPool(), startTls, delegatedTaskExecutor);
     }
 
     /**
      * Creates a new instance.
      *
      * @param engine
      *        the {@link SSLEngine} this handler will use
      * @param bufferPool
      *        the {@link SslBufferPool} where this handler will acquire
      *        the buffers required by the {@link SSLEngine}
      * @param startTls
      *        {@code true} if the first write request shouldn't be encrypted
      *        by the {@link SSLEngine}
      * @param delegatedTaskExecutor
      *        the {@link Executor} which will execute the delegated task
      *        that {@link SSLEngine#getDelegatedTask()} will return
      */
     public SslHandler(SSLEngine engine, SslBufferPool bufferPool, boolean startTls, Executor delegatedTaskExecutor) {
         if (engine == null) {
             throw new NullPointerException("engine");
         }
         if (bufferPool == null) {
             throw new NullPointerException("bufferPool");
         }
         if (delegatedTaskExecutor == null) {
             throw new NullPointerException("delegatedTaskExecutor");
         }
         this.engine = engine;
         this.bufferPool = bufferPool;
         this.delegatedTaskExecutor = delegatedTaskExecutor;
         this.startTls = startTls;
     }
 
     /**
      * Returns the {@link SSLEngine} which is used by this handler.
      */
     public SSLEngine getEngine() {
         return engine;
     }
 
     /**
      * Starts an SSL / TLS handshake for the specified channel.
      *
      * @return a {@link ChannelFuture} which is notified when the handshake
      *         succeeds or fails.
      */
     public ChannelFuture handshake() {
         if (handshaken && !isEnableRenegotiation()) {
             throw new IllegalStateException("renegotiation disabled");
         }
 
         ChannelHandlerContext ctx = this.ctx;
         Channel channel = ctx.getChannel();
         ChannelFuture handshakeFuture;
         Exception exception = null;
 
         synchronized (handshakeLock) {
             if (handshaking) {
                 return this.handshakeFuture;
             } else {
                 handshaking = true;
                 try {
                     engine.beginHandshake();
                     runDelegatedTasks();
                     handshakeFuture = this.handshakeFuture = future(channel);
                 } catch (Exception e) {
                     handshakeFuture = this.handshakeFuture = failedFuture(channel, e);
                     exception = e;
                 }
             }
         }
 
         if (exception == null) { // Began handshake successfully.
             try {
                 wrapNonAppData(ctx, channel);
             } catch (SSLException e) {
                 handshakeFuture.setFailure(e);
 
                 fireExceptionCaught(ctx, e);
                 if (closeOnSSLException) {
                     Channels.close(ctx, future(channel));
                 }
             }
         } else { // Failed to initiate handshake.
             fireExceptionCaught(ctx, exception);
             if (closeOnSSLException) {
                 Channels.close(ctx, future(channel));
             }
         }
 
         return handshakeFuture;
     }
 
     /**
      * @deprecated Use {@link #handshake()} instead.
      */
     @Deprecated
     public ChannelFuture handshake(@SuppressWarnings("unused") Channel channel) {
         return handshake();
     }
 
     /**
      * Sends an SSL {@code close_notify} message to the specified channel and
      * destroys the underlying {@link SSLEngine}.
      */
     public ChannelFuture close() {
         ChannelHandlerContext ctx = this.ctx;
         Channel channel = ctx.getChannel();
         try {
             engine.closeOutbound();
             return wrapNonAppData(ctx, channel);
         } catch (SSLException e) {
             fireExceptionCaught(ctx, e);
             if (closeOnSSLException) {
                 Channels.close(ctx, future(channel));
             }
             return failedFuture(channel, e);
         }
     }
 
     /**
      * @deprecated Use {@link #close()} instead.
      */
     @Deprecated
     public ChannelFuture close(@SuppressWarnings("unused") Channel channel) {
         return close();
     }
 
     /**
      * Returns {@code true} if and only if TLS renegotiation is enabled.
      */
     public boolean isEnableRenegotiation() {
         return enableRenegotiation;
     }
 
     /**
      * Enables or disables TLS renegotiation.
      */
     public void setEnableRenegotiation(boolean enableRenegotiation) {
         this.enableRenegotiation = enableRenegotiation;
     }
 
     /**
      * Enables or disables the automatic handshake once the {@link Channel} is
      * connected. The value will only have affect if its set before the
      * {@link Channel} is connected.
      */
     public void setIssueHandshake(boolean issueHandshake) {
         this.issueHandshake = issueHandshake;
     }
 
     /**
      * Returns <code>true</code> if the automatic handshake is enabled
      */
     public boolean isIssueHandshake() {
         return issueHandshake;
     }
 
     /**
      * Return the {@link ChannelFuture} that will get notified if the inbound of the {@link SSLEngine} will get closed.
      *
      * This method will return the same {@link ChannelFuture} all the time.
      *
      * For more informations see the apidocs of {@link SSLEngine}
      *
      */
     public ChannelFuture getSSLEngineInboundCloseFuture() {
         return sslEngineCloseFuture;
 
     }
 
     /**
      * If set to <code>true</code>, the {@link Channel} will automatically get closed
      * one a {@link SSLException} was caught. This is most times what you want, as after this
      * its almost impossible to recover.
      *
      * Anyway the default is <code>false</code> to not break compatibility with older releases. This
      * will be changed to <code>true</code> in the next major release.
      *
      */
     public void setCloseOnSSLException(boolean closeOnSslException) {
         if (ctx != null) {
             throw new IllegalStateException("Can only get changed before attached to ChannelPipeline");
         }
         closeOnSSLException = closeOnSslException;
     }
 
     public boolean getCloseOnSSLException() {
         return closeOnSSLException;
     }
 
     public void handleDownstream(
             final ChannelHandlerContext context, final ChannelEvent evt) throws Exception {
         if (evt instanceof ChannelStateEvent) {
             ChannelStateEvent e = (ChannelStateEvent) evt;
             switch (e.getState()) {
             case OPEN:
             case CONNECTED:
             case BOUND:
                 if (Boolean.FALSE.equals(e.getValue()) || e.getValue() == null) {
                     closeOutboundAndChannel(context, e);
                     return;
                 }
             }
         }
         if (!(evt instanceof MessageEvent)) {
             context.sendDownstream(evt);
             return;
         }
 
         MessageEvent e = (MessageEvent) evt;
         if (!(e.getMessage() instanceof ChannelBuffer)) {
             context.sendDownstream(evt);
             return;
         }
 
         // Do not encrypt the first write request if this handler is
         // created with startTLS flag turned on.
         if (startTls && sentFirstMessage.compareAndSet(false, true)) {
             context.sendDownstream(evt);
             return;
         }
 
         // Otherwise, all messages are encrypted.
         ChannelBuffer msg = (ChannelBuffer) e.getMessage();
         PendingWrite pendingWrite;
 
         if (msg.readable()) {
             pendingWrite = new PendingWrite(evt.getFuture(), msg.toByteBuffer(msg.readerIndex(), msg.readableBytes()));
         } else {
             pendingWrite = new PendingWrite(evt.getFuture(), null);
         }
         synchronized (pendingUnencryptedWrites) {
             boolean offered = pendingUnencryptedWrites.offer(pendingWrite);
             assert offered;
         }
 
         wrap(context, evt.getChannel());
     }
 
     @Override
     public void channelDisconnected(ChannelHandlerContext ctx,
             ChannelStateEvent e) throws Exception {
 
         // Make sure the handshake future is notified when a connection has
         // been closed during handshake.
         synchronized (handshakeLock) {
             if (handshaking) {
                 handshakeFuture.setFailure(new ClosedChannelException());
             }
         }
 
         try {
             super.channelDisconnected(ctx, e);
         } finally {
             unwrap(ctx, e.getChannel(), ChannelBuffers.EMPTY_BUFFER, 0, 0);
             engine.closeOutbound();
             if (!sentCloseNotify.get() && handshaken) {
                 try {
                     engine.closeInbound();
                 } catch (SSLException ex) {
                     if (logger.isDebugEnabled()) {
                         logger.debug("Failed to clean up SSLEngine.", ex);
                     }
                 }
             }
         }
     }
 
     @Override
     public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e)
             throws Exception {
 
         Throwable cause = e.getCause();
         if (cause instanceof IOException) {
             if (cause instanceof ClosedChannelException) {
                 synchronized (ignoreClosedChannelExceptionLock) {
                     if (ignoreClosedChannelException > 0) {
                         ignoreClosedChannelException --;
                         if (logger.isDebugEnabled()) {
                             logger.debug(
                                     "Swallowing an exception raised while " +
                                     "writing non-app data", cause);
                         }
 
                         return;
                     }
                 }
             } else {
                 if (ignoreException(cause)) {
                     return;
                 }
             }
         }
 
         ctx.sendUpstream(e);
     }
 
     /**
      * Checks if the given {@link Throwable} can be ignore and just "swallowed"
      *
      * When an ssl connection is closed a close_notify message is sent.
      * After that the peer also sends close_notify however, it's not mandatory to receive
      * the close_notify. The party who sent the initial close_notify can close the connection immediately
      * then the peer will get connection reset error.
      *
      */
     private boolean ignoreException(Throwable t) {
         if (!(t instanceof SSLException) && t instanceof IOException && engine.isOutboundDone()) {
             String message = String.valueOf(t.getMessage()).toLowerCase();
 
             // first try to match connection reset / broke peer based on the regex. This is the fastest way
             // but may fail on different jdk impls or OS's
             if (IGNORABLE_ERROR_MESSAGE.matcher(message).matches()) {
                 return true;
             }
 
             // Inspect the StackTraceElements to see if it was a connection reset / broken pipe or not
             StackTraceElement[] elements = t.getStackTrace();
             for (StackTraceElement element: elements) {
                 String classname = element.getClassName();
                 String methodname = element.getMethodName();
 
                 // skip all classes that belong to the io.netty package
                 if (classname.startsWith("org.jboss.netty.")) {
                     continue;
                 }
 
                 // check if the method name is read if not skip it
                 if (!methodname.equals("read")) {
                     continue;
                 }
 
                 // This will also match against SocketInputStream which is used by openjdk 7 and maybe
                 // also others
                 if (IGNORABLE_CLASS_IN_STACK.matcher(classname).matches()) {
                     return true;
                 }
 
                 try {
                     // No match by now.. Try to load the class via classloader and inspect it.
                     // This is mainly done as other JDK implementations may differ in name of
                     // the impl.
                     Class<?> clazz = getClass().getClassLoader().loadClass(classname);
 
                     if (SocketChannel.class.isAssignableFrom(clazz)
                             || DatagramChannel.class.isAssignableFrom(clazz)) {
                         return true;
                     }
 
                     // also match against SctpChannel via String matching as it may not present.
                     if (DetectionUtil.javaVersion() >= 7
                             && "com.sun.nio.sctp.SctpChannel".equals(clazz.getSuperclass().getName())) {
                         return true;
                     }
                 } catch (ClassNotFoundException e) {
                     // This should not happen just ignore
                 }
 
             }
         }
 
         return false;
     }
 
     /**
      * Returns <code>true</code> if the given {@link ChannelBuffer} is encrypted. Be aware that this method
      * will not increase the readerIndex of the given {@link ChannelBuffer}.
      *
      * @param   buffer
      *                  The {@link ChannelBuffer} to read from. Be aware that it must have at least 5 bytes to read,
      *                  otherwise it will throw an {@link IllegalArgumentException}.
      * @return  encrypted
      *                  <code>true</code> if the {@link ChannelBuffer} is encrypted, <code>false</code> otherwise.
      * @throws IllegalArgumentException
      *                  Is thrown if the given {@link ChannelBuffer} has not at least 5 bytes to read.
      */
     public static boolean isEncrypted(ChannelBuffer buffer) {
         return getEncryptedPacketLength(buffer) != -1;
     }
 
     /**
      * Return how much bytes can be read out of the encrypted data. Be aware that this method will not increase
      * the readerIndex of the given {@link ChannelBuffer}.
      *
      * @param   buffer
      *                  The {@link ChannelBuffer} to read from. Be aware that it must have at least 5 bytes to read,
      *                  otherwise it will throw an {@link IllegalArgumentException}.
      * @return  length
      *                  The length of the encrypted packet that is included in the buffer. This will
      *                  return <code>-1</code> if the given {@link ChannelBuffer} is not encrypted at all.
      * @throws IllegalArgumentException
      *                  Is thrown if the given {@link ChannelBuffer} has not at least 5 bytes to read.
      */
     private static int getEncryptedPacketLength(ChannelBuffer buffer) {
         if (buffer.readableBytes() < 5) {
             throw new IllegalArgumentException("buffer must have at least 5 readable bytes");
         }
 
         int packetLength = 0;
 
         // SSLv3 or TLS - Check ContentType
         boolean tls;
         switch (buffer.getUnsignedByte(buffer.readerIndex())) {
         case 20:  // change_cipher_spec
         case 21:  // alert
         case 22:  // handshake
         case 23:  // application_data
             tls = true;
             break;
         default:
             // SSLv2 or bad data
             tls = false;
         }
 
         if (tls) {
             // SSLv3 or TLS - Check ProtocolVersion
             int majorVersion = buffer.getUnsignedByte(buffer.readerIndex() + 1);
             if (majorVersion == 3) {
                 // SSLv3 or TLS
                 packetLength = (getShort(buffer, buffer.readerIndex() + 3) & 0xFFFF) + 5;
                 if (packetLength <= 5) {
                     // Neither SSLv3 or TLSv1 (i.e. SSLv2 or bad data)
                     tls = false;
                 }
             } else {
                 // Neither SSLv3 or TLSv1 (i.e. SSLv2 or bad data)
                 tls = false;
             }
         }
 
         if (!tls) {
             // SSLv2 or bad data - Check the version
             boolean sslv2 = true;
             int headerLength = (buffer.getUnsignedByte(
                     buffer.readerIndex()) & 0x80) != 0 ? 2 : 3;
             int majorVersion = buffer.getUnsignedByte(
                     buffer.readerIndex() + headerLength + 1);
             if (majorVersion == 2 || majorVersion == 3) {
                 // SSLv2
                 if (headerLength == 2) {
                     packetLength = (getShort(buffer, buffer.readerIndex()) & 0x7FFF) + 2;
                 } else {
                     packetLength = (getShort(buffer, buffer.readerIndex()) & 0x3FFF) + 3;
                 }
                 if (packetLength <= headerLength) {
                     sslv2 = false;
                 }
             } else {
                 sslv2 = false;
             }
 
             if (!sslv2) {
                 return -1;
             }
         }
         return packetLength;
     }
 
     @Override
     protected Object decode(
             final ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
 
         // Check if the packet length was parsed yet, if so we can skip the parsing
         if (packetLength == Integer.MIN_VALUE) {
             if (buffer.readableBytes() < 5) {
                 return null;
             }
             int packetLength = getEncryptedPacketLength(buffer);
 
             if (packetLength == -1) {
                 // Bad data - discard the buffer and raise an exception.
                 NotSslRecordException e = new NotSslRecordException(
                         "not an SSL/TLS record: " + ChannelBuffers.hexDump(buffer));
                 buffer.skipBytes(buffer.readableBytes());
 
                 if (closeOnSSLException) {
                     // first trigger the exception and then close the channel
                     fireExceptionCaught(ctx, e);
                     Channels.close(ctx, future(channel));
 
                     // just return null as we closed the channel before, that
                     // will take care of cleanup etc
                     return null;
                 } else {
                     throw e;
                 }
             }
 
             assert packetLength > 0;
             this.packetLength = packetLength;
         }
 
         if (buffer.readableBytes() < packetLength) {
             return null;
         }
 
         // We advance the buffer's readerIndex before calling unwrap() because
         // unwrap() can trigger FrameDecoder call decode(), this method, recursively.
         // The recursive call results in decoding the same packet twice if
         // the readerIndex is advanced *after* decode().
         //
         // Here's an example:
         // 1) An SSL packet is received from the wire.
         // 2) SslHandler.decode() deciphers the packet and calls the user code.
         // 3) The user closes the channel in the same thread.
         // 4) The same thread triggers a channelDisconnected() event.
         // 5) FrameDecoder.cleanup() is called, and it calls SslHandler.decode().
         // 6) SslHandler.decode() will feed the same packet with what was
         //    deciphered at the step 2 again if the readerIndex was not advanced
         //    before calling the user code.
         final int packetOffset = buffer.readerIndex();
         buffer.skipBytes(packetLength);
         try {
             return unwrap(ctx, channel, buffer, packetOffset, packetLength);
         } finally {
             // reset the packet length so it will be parsed again on the next call
             packetLength = Integer.MIN_VALUE;
         }
 
     }
 
     /**
      * Reads a big-endian short integer from the buffer.  Please note that we do not use
      * {@link ChannelBuffer#getShort(int)} because it might be a little-endian buffer.
      */
     private static short getShort(ChannelBuffer buf, int offset) {
         return (short) (buf.getByte(offset) << 8 | buf.getByte(offset + 1) & 0xFF);
     }
 
     private void wrap(ChannelHandlerContext context, Channel channel)
             throws SSLException {
 
         ChannelBuffer msg;
         ByteBuffer outNetBuf = bufferPool.acquireBuffer();
         boolean success = true;
         boolean offered = false;
         boolean needsUnwrap = false;
         PendingWrite pendingWrite = null;
 
         try {
             loop:
             for (;;) {
                 // Acquire a lock to make sure unencrypted data is polled
                 // in order and their encrypted counterpart is offered in
                 // order.
                 synchronized (pendingUnencryptedWrites) {
                     pendingWrite = pendingUnencryptedWrites.peek();
                     if (pendingWrite == null) {
                         break;
                     }
 
                     ByteBuffer outAppBuf = pendingWrite.outAppBuf;
                     if (outAppBuf == null) {
                         // A write request with an empty buffer
                         pendingUnencryptedWrites.remove();
                         offerEncryptedWriteRequest(
                                 new DownstreamMessageEvent(
                                         channel, pendingWrite.future,
                                         ChannelBuffers.EMPTY_BUFFER,
                                         channel.getRemoteAddress()));
                         offered = true;
                     } else {
                         SSLEngineResult result = null;
                         try {
                             synchronized (handshakeLock) {
                                 result = engine.wrap(outAppBuf, outNetBuf);
                             }
                         } finally {
                             if (!outAppBuf.hasRemaining()) {
                                 pendingUnencryptedWrites.remove();
                             }
                         }
 
                         if (result.bytesProduced() > 0) {
                             outNetBuf.flip();
                             int remaining = outNetBuf.remaining();
                             msg = ctx.getChannel().getConfig().getBufferFactory().getBuffer(remaining);
 
                             // Transfer the bytes to the new ChannelBuffer using some safe method that will also
                             // work with "non" heap buffers
                             //
                             // See https://github.com/netty/netty/issues/329
                             msg.writeBytes(outNetBuf);
                             outNetBuf.clear();
 
                             ChannelFuture future;
                             if (pendingWrite.outAppBuf.hasRemaining()) {
                                 // pendingWrite's future shouldn't be notified if
                                 // only partial data is written.
                                 future = succeededFuture(channel);
                             } else {
                                 future = pendingWrite.future;
                             }
 
                             MessageEvent encryptedWrite = new DownstreamMessageEvent(
                                     channel, future, msg, channel.getRemoteAddress());
                             offerEncryptedWriteRequest(encryptedWrite);
                             offered = true;
                         } else if (result.getStatus() == Status.CLOSED) {
                             // SSLEngine has been closed already.
                             // Any further write attempts should be denied.
                             success = false;
                             break;
                         } else {
                             final HandshakeStatus handshakeStatus = result.getHandshakeStatus();
                             handleRenegotiation(handshakeStatus);
                             switch (handshakeStatus) {
                             case NEED_WRAP:
                                 if (outAppBuf.hasRemaining()) {
                                     break;
                                 } else {
                                     break loop;
                                 }
                             case NEED_UNWRAP:
                                 needsUnwrap = true;
                                 break loop;
                             case NEED_TASK:
                                 runDelegatedTasks();
                                 break;
                             case FINISHED:
                             case NOT_HANDSHAKING:
                                 if (handshakeStatus == HandshakeStatus.FINISHED) {
                                     setHandshakeSuccess(channel);
                                 }
                                 if (result.getStatus() == Status.CLOSED) {
                                     success = false;
                                 }
                                 break loop;
                             default:
                                 throw new IllegalStateException(
                                         "Unknown handshake status: " +
                                         handshakeStatus);
                             }
                         }
                     }
                 }
             }
         } catch (SSLException e) {
             success = false;
             setHandshakeFailure(channel, e);
             throw e;
         } finally {
             bufferPool.releaseBuffer(outNetBuf);
 
             if (offered) {
                 flushPendingEncryptedWrites(context);
             }
 
             if (!success) {
                 IllegalStateException cause =
                     new IllegalStateException("SSLEngine already closed");
 
                 // Check if we had a pendingWrite in process, if so we need to also notify as otherwise
                 // the ChannelFuture will never get notified
                 if (pendingWrite != null) {
                     pendingWrite.future.setFailure(cause);
                 }
 
                 // Mark all remaining pending writes as failure if anything
                 // wrong happened before the write requests are wrapped.
                 // Please note that we do not call setFailure while a lock is
                 // acquired, to avoid a potential dead lock.
                 for (;;) {
                     synchronized (pendingUnencryptedWrites) {
                         pendingWrite = pendingUnencryptedWrites.poll();
                         if (pendingWrite == null) {
                             break;
                         }
                     }
 
                     pendingWrite.future.setFailure(cause);
                 }
             }
         }
 
         if (needsUnwrap) {
             unwrap(context, channel, ChannelBuffers.EMPTY_BUFFER, 0, 0);
         }
     }
 
     private void offerEncryptedWriteRequest(MessageEvent encryptedWrite) {
         final boolean locked = pendingEncryptedWritesLock.tryLock();
         try {
             pendingEncryptedWrites.offer(encryptedWrite);
         } finally {
             if (locked) {
                 pendingEncryptedWritesLock.unlock();
             }
         }
     }
 
     private void flushPendingEncryptedWrites(ChannelHandlerContext ctx) {
         // Avoid possible dead lock and data integrity issue
         // which is caused by cross communication between more than one channel
         // in the same VM.
         if (!pendingEncryptedWritesLock.tryLock()) {
             return;
         }
 
         try {
             MessageEvent e;
             while ((e = pendingEncryptedWrites.poll()) != null) {
                 ctx.sendDownstream(e);
             }
         } finally {
             pendingEncryptedWritesLock.unlock();
         }
     }
 
     private ChannelFuture wrapNonAppData(ChannelHandlerContext ctx, Channel channel) throws SSLException {
         ChannelFuture future = null;
         ByteBuffer outNetBuf = bufferPool.acquireBuffer();
 
         SSLEngineResult result;
         try {
             for (;;) {
                 synchronized (handshakeLock) {
                     result = engine.wrap(EMPTY_BUFFER, outNetBuf);
                 }
 
                 if (result.bytesProduced() > 0) {
                     outNetBuf.flip();
                     ChannelBuffer msg =
                             ctx.getChannel().getConfig().getBufferFactory().getBuffer(outNetBuf.remaining());
 
 
                     // Transfer the bytes to the new ChannelBuffer using some safe method that will also
                     // work with "non" heap buffers
                     //
                     // See https://github.com/netty/netty/issues/329
                     msg.writeBytes(outNetBuf);
                     outNetBuf.clear();
 
                     future = future(channel);
                     future.addListener(new ChannelFutureListener() {
                         public void operationComplete(ChannelFuture future)
                                 throws Exception {
                             if (future.getCause() instanceof ClosedChannelException) {
                                 synchronized (ignoreClosedChannelExceptionLock) {
                                     ignoreClosedChannelException ++;
                                 }
                             }
                         }
                     });
 
                     write(ctx, future, msg);
                 }
 
                 final HandshakeStatus handshakeStatus = result.getHandshakeStatus();
                 handleRenegotiation(handshakeStatus);
                 switch (handshakeStatus) {
                 case FINISHED:
                     setHandshakeSuccess(channel);
                     runDelegatedTasks();
                     break;
                 case NEED_TASK:
                     runDelegatedTasks();
                     break;
                 case NEED_UNWRAP:
                     if (!Thread.holdsLock(handshakeLock)) {
                         // unwrap shouldn't be called when this method was
                         // called by unwrap - unwrap will keep running after
                         // this method returns.
                         unwrap(ctx, channel, ChannelBuffers.EMPTY_BUFFER, 0, 0);
                     }
                     break;
                 case NOT_HANDSHAKING:
                 case NEED_WRAP:
                     break;
                 default:
                     throw new IllegalStateException(
                             "Unexpected handshake status: " + handshakeStatus);
                 }
 
                 if (result.bytesProduced() == 0) {
                     break;
                 }
             }
         } catch (SSLException e) {
             setHandshakeFailure(channel, e);
             throw e;
         } finally {
             bufferPool.releaseBuffer(outNetBuf);
         }
 
         if (future == null) {
             future = succeededFuture(channel);
         }
 
         return future;
     }
 
     private ChannelBuffer unwrap(
             ChannelHandlerContext ctx, Channel channel,
             ChannelBuffer buffer, int offset, int length) throws SSLException {
         ByteBuffer inNetBuf = buffer.toByteBuffer(offset, length);
         ByteBuffer outAppBuf = bufferPool.acquireBuffer();
 
         try {
             boolean needsWrap = false;
             loop:
             for (;;) {
                 SSLEngineResult result;
                 boolean needsHandshake = false;
                 synchronized (handshakeLock) {
                     if (!handshaken && !handshaking &&
                         !engine.getUseClientMode() &&
                         !engine.isInboundDone() && !engine.isOutboundDone()) {
                         needsHandshake = true;
 
                     }
                 }
                 if (needsHandshake) {
                     handshake();
                 }
 
                 synchronized (handshakeLock) {
                     result = engine.unwrap(inNetBuf, outAppBuf);
                 }
 
                 // notify about the CLOSED state of the SSLEngine. See #137
                 if (result.getStatus() == Status.CLOSED) {
                     sslEngineCloseFuture.setClosed();
                 }
 
 
                 final HandshakeStatus handshakeStatus = result.getHandshakeStatus();
                 handleRenegotiation(handshakeStatus);
                 switch (handshakeStatus) {
                 case NEED_UNWRAP:
                     if (inNetBuf.hasRemaining() && !engine.isInboundDone()) {
                         break;
                     } else {
                         break loop;
                     }
                 case NEED_WRAP:
                     wrapNonAppData(ctx, channel);
                     break;
                 case NEED_TASK:
                     runDelegatedTasks();
                     break;
                 case FINISHED:
                     setHandshakeSuccess(channel);
                     needsWrap = true;
                     break loop;
                 case NOT_HANDSHAKING:
                     needsWrap = true;
                     break loop;
                 default:
                     throw new IllegalStateException(
                             "Unknown handshake status: " + handshakeStatus);
                 }
 
             }
 
             if (needsWrap) {
                 // wrap() acquires pendingUnencryptedWrites first and then
                 // handshakeLock.  If handshakeLock is already hold by the
                 // current thread, calling wrap() will lead to a dead lock
                 // i.e. pendingUnencryptedWrites -> handshakeLock vs.
                 //      handshakeLock -> pendingUnencryptedLock -> handshakeLock
                 //
                 // There is also a same issue between pendingEncryptedWrites
                 // and pendingUnencryptedWrites.
                 if (!Thread.holdsLock(handshakeLock) &&
                     !pendingEncryptedWritesLock.isHeldByCurrentThread()) {
                     wrap(ctx, channel);
                 }
             }
 
             outAppBuf.flip();
 
             if (outAppBuf.hasRemaining()) {
                 ChannelBuffer frame = ctx.getChannel().getConfig().getBufferFactory().getBuffer(outAppBuf.remaining());
                 // Transfer the bytes to the new ChannelBuffer using some safe method that will also
                 // work with "non" heap buffers
                 //
                 // See https://github.com/netty/netty/issues/329
                 frame.writeBytes(outAppBuf);
 
                 return frame;
             } else {
                 return null;
             }
         } catch (SSLException e) {
             setHandshakeFailure(channel, e);
             throw e;
         } finally {
             bufferPool.releaseBuffer(outAppBuf);
         }
     }
 
     private void handleRenegotiation(HandshakeStatus handshakeStatus) {
         if (handshakeStatus == HandshakeStatus.NOT_HANDSHAKING ||
             handshakeStatus == HandshakeStatus.FINISHED) {
             // Not handshaking
             return;
         }
 
         if (!handshaken) {
             // Not renegotiation
             return;
         }
 
         final boolean renegotiate;
         synchronized (handshakeLock) {
             if (handshaking) {
                 // Renegotiation in progress or failed already.
                 // i.e. Renegotiation check has been done already below.
                 return;
             }
 
             if (engine.isInboundDone() || engine.isOutboundDone()) {
                 // Not handshaking but closing.
                 return;
             }
 
             if (isEnableRenegotiation()) {
                 // Continue renegotiation.
                 renegotiate = true;
             } else {
                 // Do not renegotiate.
                 renegotiate = false;
                 // Prevent reentrance of this method.
                 handshaking = true;
             }
         }
 
         if (renegotiate) {
             // Renegotiate.
             handshake();
         } else {
             // Raise an exception.
             fireExceptionCaught(
                     ctx, new SSLException(
                             "renegotiation attempted by peer; " +
                             "closing the connection"));
 
             // Close the connection to stop renegotiation.
             Channels.close(ctx, succeededFuture(ctx.getChannel()));
         }
     }
 
     private void runDelegatedTasks() {
         for (;;) {
             final Runnable task;
             synchronized (handshakeLock) {
                 task = engine.getDelegatedTask();
             }
 
             if (task == null) {
                 break;
             }
 
             delegatedTaskExecutor.execute(new Runnable() {
                 public void run() {
                     synchronized (handshakeLock) {
                         task.run();
                     }
                 }
             });
         }
     }
 
     private void setHandshakeSuccess(Channel channel) {
         synchronized (handshakeLock) {
             handshaking = false;
             handshaken = true;
 
             if (handshakeFuture == null) {
                 handshakeFuture = future(channel);
             }
         }
 
         handshakeFuture.setSuccess();
     }
 
     private void setHandshakeFailure(Channel channel, SSLException cause) {
         synchronized (handshakeLock) {
             if (!handshaking) {
                 return;
             }
             handshaking = false;
             handshaken = false;
 
             if (handshakeFuture == null) {
                 handshakeFuture = future(channel);
             }
 
             // Release all resources such as internal buffers that SSLEngine
             // is managing.
 
             engine.closeOutbound();
 
             try {
                 engine.closeInbound();
             } catch (SSLException e) {
                 if (logger.isDebugEnabled()) {
                     logger.debug(
                             "SSLEngine.closeInbound() raised an exception after " +
                             "a handshake failure.", e);
                 }
 
             }
         }
 
         handshakeFuture.setFailure(cause);
         if (closeOnSSLException) {
             Channels.close(ctx, future(channel));
         }
     }
 
     private void closeOutboundAndChannel(
             final ChannelHandlerContext context, final ChannelStateEvent e) {
         if (!e.getChannel().isConnected()) {
             context.sendDownstream(e);
             return;
         }
 
         boolean passthrough = true;
         try {
             try {
                 unwrap(context, e.getChannel(), ChannelBuffers.EMPTY_BUFFER, 0, 0);
             } catch (SSLException ex) {
                 if (logger.isDebugEnabled()) {
                     logger.debug("Failed to unwrap before sending a close_notify message", ex);
                 }
             }
 
             if (!engine.isOutboundDone()) {
                 if (sentCloseNotify.compareAndSet(false, true)) {
                     engine.closeOutbound();
                     try {
                         ChannelFuture closeNotifyFuture = wrapNonAppData(context, e.getChannel());
                         closeNotifyFuture.addListener(
                                 new ClosingChannelFutureListener(context, e));
                         passthrough = false;
                     } catch (SSLException ex) {
                         if (logger.isDebugEnabled()) {
                             logger.debug("Failed to encode a close_notify message", ex);
                         }
                     }
                 }
             }
         } finally {
             if (passthrough) {
                 context.sendDownstream(e);
             }
         }
     }
 
     private static final class PendingWrite {
         final ChannelFuture future;
         final ByteBuffer outAppBuf;
 
         PendingWrite(ChannelFuture future, ByteBuffer outAppBuf) {
             this.future = future;
             this.outAppBuf = outAppBuf;
         }
     }
 
     private static final class ClosingChannelFutureListener implements ChannelFutureListener {
 
         private final ChannelHandlerContext context;
         private final ChannelStateEvent e;
 
         ClosingChannelFutureListener(
                 ChannelHandlerContext context, ChannelStateEvent e) {
             this.context = context;
             this.e = e;
         }
 
         public void operationComplete(ChannelFuture closeNotifyFuture) throws Exception {
             if (!(closeNotifyFuture.getCause() instanceof ClosedChannelException)) {
                 Channels.close(context, e.getFuture());
             } else {
                 e.getFuture().setSuccess();
             }
         }
     }
 
     @Override
     public void beforeAdd(ChannelHandlerContext ctx) throws Exception {
         super.beforeAdd(ctx);
         this.ctx = ctx;
     }
 
     /**
      * Fail all pending writes which we were not able to flush out
      */
     @Override
     public void afterRemove(ChannelHandlerContext ctx) throws Exception {
 
         // there is no need for synchronization here as we do not receive downstream events anymore
         Throwable cause = null;
         for (;;) {
             PendingWrite pw = pendingUnencryptedWrites.poll();
             if (pw == null) {
                 break;
             }
             if (cause == null) {
                 cause = new IOException("Unable to write data");
             }
             pw.future.setFailure(cause);
 
         }
 
         for (;;) {
             MessageEvent ev = pendingEncryptedWrites.poll();
             if (ev == null) {
                 break;
             }
             if (cause == null) {
                 cause = new IOException("Unable to write data");
             }
             ev.getFuture().setFailure(cause);
 
         }
 
         if (cause != null) {
             fireExceptionCaughtLater(ctx, cause);
         }
     }
 
 
     /**
      * Calls {@link #handshake()} once the {@link Channel} is connected
      */
     @Override
     public void channelConnected(final ChannelHandlerContext ctx, final ChannelStateEvent e) throws Exception {
         if (issueHandshake) {
             // issue and handshake and add a listener to it which will fire an exception event if
             // an exception was thrown while doing the handshake
             handshake().addListener(new ChannelFutureListener() {
 
                 public void operationComplete(ChannelFuture future) throws Exception {
                     if (!future.isSuccess()) {
                         fireExceptionCaught(future.getChannel(), future.getCause());
                     } else {
                         // Send the event upstream after the handshake was completed without an error.
                         //
                         // See https://github.com/netty/netty/issues/358
                         ctx.sendUpstream(e);
                     }
 
                 }
             });
         } else {
             super.channelConnected(ctx, e);
         }
     }
 
     /**
      * Loop over all the pending writes and fail them.
      *
      * See <a href="https://github.com/netty/netty/issues/305">#305</a> for more details.
      */
     @Override
     public void channelClosed(ChannelHandlerContext ctx, ChannelStateEvent e) throws Exception {
         Throwable cause = null;
         synchronized (pendingUnencryptedWrites) {
             for (;;) {
                 PendingWrite pw = pendingUnencryptedWrites.poll();
                 if (pw == null) {
                     break;
                 }
                 if (cause == null) {
                     cause = new ClosedChannelException();
                 }
                 pw.future.setFailure(cause);
 
             }
 
 
             for (;;) {
                 MessageEvent ev = pendingEncryptedWrites.poll();
                 if (ev == null) {
                     break;
                 }
                 if (cause == null) {
                     cause = new ClosedChannelException();
                 }
                 ev.getFuture().setFailure(cause);
 
             }
         }
 
         if (cause != null) {
             fireExceptionCaught(ctx, cause);
         }
 
         super.channelClosed(ctx, e);
     }
 
     private final class SSLEngineInboundCloseFuture extends DefaultChannelFuture {
         public SSLEngineInboundCloseFuture() {
             super(null, true);
         }
 
         void setClosed() {
             super.setSuccess();
         }
 
         @Override
         public Channel getChannel() {
             if (ctx == null) {
                 // Maybe we should better throw an IllegalStateException() ?
                 return null;
             } else {
                 return ctx.getChannel();
             }
         }
 
         @Override
         public boolean setSuccess() {
             return false;
         }
 
         @Override
         public boolean setFailure(Throwable cause) {
             return false;
         }
     }
 }