Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF 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.apache.sshd.server.x11; import java.io.IOException; import java.net.BindException; import java.net.InetSocketAddress; import java.util.EnumSet; import org.apache.mina.core.buffer.IoBuffer; import org.apache.mina.core.service.IoAcceptor; import org.apache.mina.core.service.IoHandlerAdapter; import org.apache.mina.core.session.IoEventType; import org.apache.mina.core.session.IoSession; import org.apache.mina.filter.executor.ExecutorFilter; import org.apache.mina.transport.socket.nio.NioSocketAcceptor; import org.apache.sshd.client.channel.AbstractClientChannel; import org.apache.sshd.client.future.DefaultOpenFuture; import org.apache.sshd.client.future.OpenFuture; import org.apache.sshd.common.SshConstants; import org.apache.sshd.common.SshException; import org.apache.sshd.common.channel.ChannelOutputStream; import org.apache.sshd.common.util.Buffer; import org.apache.sshd.common.util.LogUtils; import org.apache.sshd.server.session.ServerSession; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a> */ public class X11ForwardSupport extends IoHandlerAdapter { private static String xauthCommand = System.getProperty("sshd.xauthCommand", "xauth"); public static final int X11_DISPLAY_OFFSET = 10; public static final int MAX_DISPLAYS = 1000; /** * Key for the user DISPLAY variable */ public static final String ENV_DISPLAY = "DISPLAY"; protected final Log log = LogFactory.getLog(getClass()); private final ServerSession session; private IoAcceptor acceptor; public X11ForwardSupport(ServerSession session) { super(); this.session = session; } public synchronized void initialize() { if (this.acceptor == null) { NioSocketAcceptor acceptor = new NioSocketAcceptor(); acceptor.setHandler(this); acceptor.setReuseAddress(true); acceptor.getFilterChain().addLast("executor", new ExecutorFilter( EnumSet.complementOf(EnumSet.of(IoEventType.SESSION_CREATED)).toArray(new IoEventType[0]))); this.acceptor = acceptor; } } public synchronized void close() { if (acceptor != null) { acceptor.dispose(); acceptor = null; } } public synchronized String createDisplay(boolean singleConnection, String authenticationProtocol, String authenticationCookie, int screen) throws IOException { initialize(); int displayNumber, port; InetSocketAddress addr = null; for (displayNumber = X11_DISPLAY_OFFSET; displayNumber < MAX_DISPLAYS; displayNumber++) { port = 6000 + displayNumber; try { addr = new InetSocketAddress("127.0.0.1", port); acceptor.bind(addr); break; } catch (BindException bindErr) { // try until bind succesful or max is reached } } if (displayNumber >= MAX_DISPLAYS) { log.error("Failed to allocate internet-domain X11 display socket."); if (acceptor.getLocalAddresses().isEmpty()) { close(); } return null; } // only support non windows systems String os = System.getProperty("os.name").toLowerCase(); if (os.indexOf("windows") < 0) { try { String authDisplay = "unix:" + displayNumber + "." + screen; Process p = new ProcessBuilder(xauthCommand, "remove", authDisplay).start(); int result = p.waitFor(); if (result == 0) { p = new ProcessBuilder(xauthCommand, "add", authDisplay, authenticationProtocol, authenticationCookie).start(); result = p.waitFor(); } } catch (Exception e) { log.error("Could not run xauth", e); return null; } return "localhost:" + displayNumber + "." + screen; } else { return null; } } @Override public void sessionCreated(IoSession session) throws Exception { ChannelForwardedX11 channel = new ChannelForwardedX11(session); session.setAttribute(ChannelForwardedX11.class, channel); this.session.registerChannel(channel); OpenFuture future = channel.open().await(); Throwable t = future.getException(); if (t instanceof Exception) { throw (Exception) t; } else if (t != null) { throw new Exception(t); } } @Override public void sessionClosed(IoSession session) throws Exception { ChannelForwardedX11 channel = (ChannelForwardedX11) session.getAttribute(ChannelForwardedX11.class); channel.close(false); } @Override public void messageReceived(IoSession session, Object message) throws Exception { ChannelForwardedX11 channel = (ChannelForwardedX11) session.getAttribute(ChannelForwardedX11.class); IoBuffer ioBuffer = (IoBuffer) message; int r = ioBuffer.remaining(); byte[] b = new byte[r]; ioBuffer.get(b, 0, r); channel.getOut().write(b, 0, r); channel.getOut().flush(); } @Override public void exceptionCaught(IoSession session, Throwable cause) throws Exception { cause.printStackTrace(); session.close(false); } public static class ChannelForwardedX11 extends AbstractClientChannel { private final IoSession serverSession; public ChannelForwardedX11(IoSession serverSession) { super("x11"); this.serverSession = serverSession; } public synchronized OpenFuture open() throws Exception { InetSocketAddress remote = (InetSocketAddress) serverSession.getRemoteAddress(); if (closeFuture.isClosed()) { throw new SshException("Session has been closed"); } openFuture = new DefaultOpenFuture(lock); LogUtils.info(log, "Send SSH_MSG_CHANNEL_OPEN on channel {0}", id); Buffer buffer = session.createBuffer(SshConstants.Message.SSH_MSG_CHANNEL_OPEN, 0); buffer.putString(type); buffer.putInt(id); buffer.putInt(localWindow.getSize()); buffer.putInt(localWindow.getPacketSize()); buffer.putString(remote.getHostName()); buffer.putInt(remote.getPort()); session.writePacket(buffer); return openFuture; } @Override protected synchronized void doOpen() throws Exception { out = new ChannelOutputStream(this, remoteWindow, log, SshConstants.Message.SSH_MSG_CHANNEL_DATA); } @Override protected synchronized void doClose() { serverSession.close(false); super.doClose(); } protected synchronized void doWriteData(byte[] data, int off, int len) throws IOException { IoBuffer buf = IoBuffer.allocate(len); buf.put(data, off, len); buf.flip(); localWindow.consumeAndCheck(len); serverSession.write(buf); } @Override public void handleEof() throws IOException { super.handleEof(); serverSession.close(false); } } }