/*
 * @(#)ChannelIOSecure.java	1.5 10/01/12
 * 
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 * 
 * -Redistribution in binary form must reproduce the above copyright notice, 
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may 
 * be used to endorse or promote products derived from this software without 
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL 
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST 
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, 
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY 
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, 
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 * 
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */

import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import javax.net.ssl.*;
import javax.net.ssl.SSLEngineResult.*;

/**
 * A helper class which performs I/O using the SSLEngine API.
 * <P>
 * Each connection has a SocketChannel and a SSLEngine that is
 * used through the lifetime of the Channel.  We allocate byte buffers
 * for use as the outbound and inbound network buffers.
 *
 * <PRE>
 *               Application Data
 *               src      requestBB
 *                |           ^
 *                |     |     |
 *                v     |     |
 *           +----+-----|-----+----+
 *           |          |          |
 *           |       SSL|Engine    |
 *   wrap()  |          |          |  unwrap()
 *           | OUTBOUND | INBOUND  |
 *           |          |          |
 *           +----+-----|-----+----+
 *                |     |     ^
 *                |     |     |
 *                v           |
 *            outNetBB     inNetBB
 *                   Net data
 * </PRE>
 *
 * These buffers handle all of the intermediary data for the SSL
 * connection.  To make things easy, we'll require outNetBB be
 * completely flushed before trying to wrap any more data, but we
 * could certainly remove that restriction by using larger buffers.
 * <P>
 * There are many, many ways to handle compute and I/O strategies.
 * What follows is a relatively simple one.  The reader is encouraged
 * to develop the strategy that best fits the application.
 * <P>
 * In most of the non-blocking operations in this class, we let the
 * Selector tell us when we're ready to attempt an I/O operation (by the
 * application repeatedly calling our methods).  Another option would be
 * to attempt the operation and return from the method when no forward
 * progress can be made.
 * <P>
 * There's lots of room for enhancements and improvement in this example.
 * <P>
 * We're checking for SSL/TLS end-of-stream truncation attacks via
 * sslEngine.closeInbound().  When you reach the end of a input stream
 * via a read() returning -1 or an IOException, we call
 * sslEngine.closeInbound() to signal to the sslEngine that no more
 * input will be available.  If the peer's close_notify message has not
 * yet been received, this could indicate a trucation attack, in which
 * an attacker is trying to prematurely close the connection.   The
 * closeInbound() will throw an exception if this condition were
 * present.
 *
 * @author Brad R. Wetmore
 * @author Mark Reinhold
 * @version 1.5, 10/01/12
 */
class ChannelIOSecure extends ChannelIO {

    private SSLEngine sslEngine = null;

    private int appBBSize;
    private int netBBSize;

    /*
     * All I/O goes through these buffers.
     * <P>
     * It might be nice to use a cache of ByteBuffers so we're
     * not alloc/dealloc'ing ByteBuffer's for each new SSLEngine.
     * <P>
     * We use our superclass' requestBB for our application input buffer.
     * Outbound application data is supplied to us by our callers.
     */
    private ByteBuffer inNetBB;
    private ByteBuffer outNetBB;

    /*
     * An empty ByteBuffer for use when one isn't available, say
     * as a source buffer during initial handshake wraps or for close
     * operations.
     */
    private static ByteBuffer hsBB = ByteBuffer.allocate(0);

    /*
     * The FileChannel we're currently transferTo'ing (reading).
     */
    private ByteBuffer fileChannelBB = null;

    /*
     * During our initial handshake, keep track of the next
     * SSLEngine operation that needs to occur:
     *
     *     NEED_WRAP/NEED_UNWRAP
     *
     * Once the initial handshake has completed, we can short circuit
     * handshake checks with initialHSComplete.
     */
    private HandshakeStatus initialHSStatus;
    private boolean initialHSComplete;

    /*
     * We have received the shutdown request by our caller, and have
     * closed our outbound side.
     */
    private boolean shutdown = false;

    /*
     * Constructor for a secure ChannelIO variant.
     */
    protected ChannelIOSecure(SocketChannel sc, boolean blocking,
	    SSLContext sslc) throws IOException {
	super(sc, blocking);

	/*
	 * We're a server, so no need to use host/port variant.
	 *
	 * The first call for a server is a NEED_UNWRAP.
	 */
	sslEngine = sslc.createSSLEngine();
	sslEngine.setUseClientMode(false);
	initialHSStatus = HandshakeStatus.NEED_UNWRAP;
	initialHSComplete = false;

	// Create a buffer using the normal expected packet size we'll
	// be getting.  This may change, depending on the peer's
	// SSL implementation. 
	netBBSize = sslEngine.getSession().getPacketBufferSize();
	inNetBB = ByteBuffer.allocate(netBBSize);
	outNetBB = ByteBuffer.allocate(netBBSize);
	outNetBB.position(0);
	outNetBB.limit(0);
    }

    /*
     * Static factory method for creating a secure ChannelIO object.
     * <P>
     * We need to allocate different sized application data buffers
     * based on whether we're secure or not.  We can't determine
     * this until our sslEngine is created.
     */
    static ChannelIOSecure getInstance(SocketChannel sc, boolean blocking,
	    SSLContext sslc) throws IOException {

	ChannelIOSecure cio = new ChannelIOSecure(sc, blocking, sslc);

	// Create a buffer using the normal expected application size we'll
	// be getting.  This may change, depending on the peer's
	// SSL implementation. 
	cio.appBBSize = cio.sslEngine.getSession().getApplicationBufferSize();
	cio.requestBB = ByteBuffer.allocate(cio.appBBSize);

	return cio;
    }

    /*
     * Calls up to the superclass to adjust the buffer size
     * by an appropriate increment.
     */
    protected void resizeRequestBB() {
	resizeRequestBB(appBBSize);
    }

    /*
     * Adjust the inbount network buffer to an appropriate size.
     */
    private void resizeResponseBB() {
	ByteBuffer bb = ByteBuffer.allocate(netBBSize);
	inNetBB.flip();
	bb.put(inNetBB);
	inNetBB = bb;
    }

    /*
     * Writes bb to the SocketChannel.
     * <P>
     * Returns true when the ByteBuffer has no remaining data.
     */
    private boolean tryFlush(ByteBuffer bb) throws IOException {
	super.write(bb);
	return !bb.hasRemaining();
    }

    /*
     * Perform any handshaking processing.
     * <P>
     * This variant is for Servers without SelectionKeys (e.g.
     * blocking).
     */
    boolean doHandshake() throws IOException {
	return doHandshake(null);
    }

    /*
     * Perform any handshaking processing.
     * <P>
     * If a SelectionKey is passed, register for selectable
     * operations.
     * <P>
     * In the blocking case, our caller will keep calling us until
     * we finish the handshake.  Our reads/writes will block as expected.
     * <P>
     * In the non-blocking case, we just received the selection notification
     * that this channel is ready for whatever the operation is, so give
     * it a try.
     * <P>
     * return:
     *		true when handshake is done.
     *		false while handshake is in progress
     */
    boolean doHandshake(SelectionKey sk) throws IOException {

	SSLEngineResult result;

	if (initialHSComplete) {
	    return initialHSComplete;
	}

	/*
	 * Flush out the outgoing buffer, if there's anything left in
	 * it.
	 */
	if (outNetBB.hasRemaining()) {

	    if (!tryFlush(outNetBB)) {
		return false;
	    }

	    // See if we need to switch from write to read mode.

	    switch (initialHSStatus) {

	    /*
	     * Is this the last buffer?
	     */
	    case FINISHED:
		initialHSComplete = true;
		// Fall-through to reregister need for a Read.

	    case NEED_UNWRAP:
		if (sk != null) {
		    sk.interestOps(SelectionKey.OP_READ);
		}
		break;
	    }

	    return initialHSComplete;
	}


	switch (initialHSStatus) {

	case NEED_UNWRAP:
	    if (sc.read(inNetBB) == -1) {
		sslEngine.closeInbound();
		return initialHSComplete;
	    }

needIO:
	    while (initialHSStatus == HandshakeStatus.NEED_UNWRAP) {
		resizeRequestBB();    // expected room for unwrap
		inNetBB.flip();
		result = sslEngine.unwrap(inNetBB, requestBB);
		inNetBB.compact();

		initialHSStatus = result.getHandshakeStatus();

		switch (result.getStatus()) {

		case OK:
		    switch (initialHSStatus) {
		    case NOT_HANDSHAKING:
			throw new IOException(
			    "Not handshaking during initial handshake");

		    case NEED_TASK:
			initialHSStatus = doTasks();
			break;

		    case FINISHED:
			initialHSComplete = true;
			break needIO;
		    }

		    break;

		case BUFFER_UNDERFLOW:
		    // Resize buffer if needed.
		    netBBSize = sslEngine.getSession().getPacketBufferSize();
		    if (netBBSize > inNetBB.capacity()) {
			resizeResponseBB();
		    }

		    /*
		     * Need to go reread the Channel for more data.
		     */
		    if (sk != null) {
			sk.interestOps(SelectionKey.OP_READ);
		    }
		    break needIO;

		case BUFFER_OVERFLOW:
		    // Reset the application buffer size.
		    appBBSize = 
			sslEngine.getSession().getApplicationBufferSize();
		    break;

		default: //CLOSED:
		    throw new IOException("Received" + result.getStatus() +
			"during initial handshaking");
		}
	    }  // "needIO" block.

	    /*
	     * Just transitioned from read to write.
	     */
	    if (initialHSStatus != HandshakeStatus.NEED_WRAP) {
		break;
	    }

	    // Fall through and fill the write buffers.

	case NEED_WRAP:
	    /*
	     * The flush above guarantees the out buffer to be empty
	     */
	    outNetBB.clear();
	    result = sslEngine.wrap(hsBB, outNetBB);
	    outNetBB.flip();

	    initialHSStatus = result.getHandshakeStatus();

	    switch (result.getStatus()) {
	    case OK:

		if (initialHSStatus == HandshakeStatus.NEED_TASK) {
		    initialHSStatus = doTasks();
		}

		if (sk != null) {
		    sk.interestOps(SelectionKey.OP_WRITE);
		}

		break;

	    default: // BUFFER_OVERFLOW/BUFFER_UNDERFLOW/CLOSED:
		throw new IOException("Received" + result.getStatus() +
			"during initial handshaking");
	    }
	    break;

	default: // NOT_HANDSHAKING/NEED_TASK/FINISHED
	    throw new RuntimeException("Invalid Handshaking State" +
		    initialHSStatus);
	} // switch

	return initialHSComplete;
    }

    /*
     * Do all the outstanding handshake tasks in the current Thread.
     */
    private SSLEngineResult.HandshakeStatus doTasks() {

	Runnable runnable;

	/*
	 * We could run this in a separate thread, but
	 * do in the current for now.
	 */
	while ((runnable = sslEngine.getDelegatedTask()) != null) {
	    runnable.run();
	}
	return sslEngine.getHandshakeStatus();
    }

    /*
     * Read the channel for more information, then unwrap the
     * (hopefully application) data we get.
     * <P>
     * If we run out of data, we'll return to our caller (possibly using
     * a Selector) to get notification that more is available.
     * <P>
     * Each call to this method will perform at most one underlying read().
     */
    int read() throws IOException {
	SSLEngineResult result;

	if (!initialHSComplete) {
	    throw new IllegalStateException();
	}

	int pos = requestBB.position();

	if (sc.read(inNetBB) == -1) {
	    sslEngine.closeInbound();  // probably throws exception
	    return -1;
	}

	do {
	    resizeRequestBB();    // expected room for unwrap
	    inNetBB.flip();
	    result = sslEngine.unwrap(inNetBB, requestBB);
	    inNetBB.compact();

	    /*
	     * Could check here for a renegotation, but we're only
	     * doing a simple read/write, and won't have enough state
	     * transitions to do a complete handshake, so ignore that
	     * possibility.
	     */
	    switch (result.getStatus()) {

	    case BUFFER_OVERFLOW:
		// Reset the application buffer size.
		appBBSize = sslEngine.getSession().getApplicationBufferSize();
		break;
		
	    case BUFFER_UNDERFLOW:
		// Resize buffer if needed.
		netBBSize = sslEngine.getSession().getPacketBufferSize();
		if (netBBSize > inNetBB.capacity()) {
		    resizeResponseBB();

		    break; // break, next read will support larger buffer.
		}
	    case OK:
		if (result.getHandshakeStatus() == HandshakeStatus.NEED_TASK) {
		    doTasks();
		}
		break;

	    default:
		throw new IOException("sslEngine error during data read: " +
		    result.getStatus());
	    }
	} while ((inNetBB.position() != 0) &&
	    result.getStatus() != Status.BUFFER_UNDERFLOW);

	return (requestBB.position() - pos);
    }

    /*
     * Try to write out as much as possible from the src buffer.
     */
    int write(ByteBuffer src) throws IOException {

	if (!initialHSComplete) {
	    throw new IllegalStateException();
	}

	return doWrite(src);
    }

    /*
     * Try to flush out any existing outbound data, then try to wrap
     * anything new contained in the src buffer.
     * <P>
     * Return the number of bytes actually consumed from the buffer,
     * but the data may actually be still sitting in the output buffer,
     * waiting to be flushed.
     */
    private int doWrite(ByteBuffer src) throws IOException {
	int retValue = 0;

	if (outNetBB.hasRemaining() && !tryFlush(outNetBB)) {
	    return retValue;
	}

	/*
	 * The data buffer is empty, we can reuse the entire buffer.
	 */
	outNetBB.clear();

	SSLEngineResult result = sslEngine.wrap(src, outNetBB);
	retValue = result.bytesConsumed();

	outNetBB.flip();

	switch (result.getStatus()) {

	case OK:
	    if (result.getHandshakeStatus() == HandshakeStatus.NEED_TASK) {
		doTasks();
	    }
	    break;

	default:
	    throw new IOException("sslEngine error during data write: " +
		result.getStatus());
	}

	/*
	 * Try to flush the data, regardless of whether or not
	 * it's been selected.  Odds of a write buffer being full
	 * is less than a read buffer being empty.
	 */
	if (outNetBB.hasRemaining()) {
	    tryFlush(outNetBB);
	}

	return retValue;
    }

    /*
     * Perform a FileChannel.TransferTo on the socket channel.
     * <P>
     * We have to copy the data into an intermediary app ByteBuffer
     * first, then send it through the SSLEngine.
     * <P>
     * We return the number of bytes actually read out of the
     * filechannel.  However, the data may actually be stuck
     * in the fileChannelBB or the outNetBB.  The caller
     * is responsible for making sure to call dataFlush()
     * before shutting down.
     */
    long transferTo(FileChannel fc, long pos, long len) throws IOException {

	if (!initialHSComplete) {
	    throw new IllegalStateException();
	}

	if (fileChannelBB == null) {
	    fileChannelBB = ByteBuffer.allocate(appBBSize);
	    fileChannelBB.limit(0);
	}

	fileChannelBB.compact();
	int fileRead = fc.read(fileChannelBB);
	fileChannelBB.flip();

	/*
	 * We ignore the return value here, we return the
	 * number of bytes actually consumed from the the file.
	 * We'll flush the output buffer before we start shutting down.
	 */
	doWrite(fileChannelBB);

	return fileRead;
    }

    /*
     * Flush any remaining data.
     * <P>
     * Return true when the fileChannelBB and outNetBB are empty.
     */
    boolean dataFlush() throws IOException {
	boolean fileFlushed = true;

	if ((fileChannelBB != null) && fileChannelBB.hasRemaining()) {
	    doWrite(fileChannelBB);
	    fileFlushed = !fileChannelBB.hasRemaining();
	} else if (outNetBB.hasRemaining()) {
	    tryFlush(outNetBB);
	}

	return (fileFlushed && !outNetBB.hasRemaining());
    }

    /*
     * Begin the shutdown process.
     * <P>
     * Close out the SSLEngine if not already done so, then
     * wrap our outgoing close_notify message and try to send it on.
     * <P>
     * Return true when we're done passing the shutdown messsages.
     */
    boolean shutdown() throws IOException {

	if (!shutdown) {
	    sslEngine.closeOutbound();
	    shutdown = true;
	}

	if (outNetBB.hasRemaining() && tryFlush(outNetBB)) {
	    return false;
	}

	/*
	 * By RFC 2616, we can "fire and forget" our close_notify
	 * message, so that's what we'll do here.
	 */
	outNetBB.clear();
	SSLEngineResult result = sslEngine.wrap(hsBB, outNetBB);
	if (result.getStatus() != Status.CLOSED) {
	    throw new SSLException("Improper close state");
	}
	outNetBB.flip();

	/*
	 * We won't wait for a select here, but if this doesn't work,
	 * we'll cycle back through on the next select.
	 */
	if (outNetBB.hasRemaining()) {
	    tryFlush(outNetBB);
	}

	return (!outNetBB.hasRemaining() &&
		(result.getHandshakeStatus() != HandshakeStatus.NEED_WRAP));
    }

    /*
     * close() is not overridden
     */
}
