Java tutorial
/* * Copyright 2001-2005 The Apache Software Foundation * * Licensed 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.eredlab.g4.ccl.net.bsd; import java.io.IOException; import java.io.InputStream; import java.net.BindException; import java.net.InetAddress; import java.net.ServerSocket; import java.net.Socket; import java.net.SocketException; import java.net.UnknownHostException; import org.eredlab.g4.ccl.net.io.SocketInputStream; /*** * RCommandClient is very similar to * {@link org.apache.commons.net.bsd.RExecClient}, * from which it is derived, and implements the rcmd() facility that * first appeared in 4.2BSD Unix. rcmd() is the facility used by the rsh * (rshell) and other commands to execute a command on another machine * from a trusted host without issuing a password. The trust relationship * between two machines is established by the contents of a machine's * /etc/hosts.equiv file and a user's .rhosts file. These files specify * from which hosts and accounts on those hosts rcmd() requests will be * accepted. The only additional measure for establishing trust is that * all client connections must originate from a port between 512 and 1023. * Consequently, there is an upper limit to the number of rcmd connections * that can be running simultaneously. The required ports are reserved * ports on Unix systems, and can only be bound by a * process running with root permissions (to accomplish this rsh, rlogin, * and related commands usualy have the suid bit set). Therefore, on a * Unix system, you will only be able to successfully use the RCommandClient * class if the process runs as root. However, there is no such restriction * on Windows95 and some other systems. The security risks are obvious. * However, when carefully used, rcmd() can be very useful when used behind * a firewall. * <p> * As with virtually all of the client classes in org.apache.commons.net, this * class derives from SocketClient. But it overrides most of its connection * methods so that the local Socket will originate from an acceptable * rshell port. The way to use RCommandClient is to first connect * to the server, call the {@link #rcommand rcommand() } method, * and then * fetch the connection's input, output, and optionally error streams. * Interaction with the remote command is controlled entirely through the * I/O streams. Once you have finished processing the streams, you should * invoke {@link org.apache.commons.net.bsd.RExecClient#disconnect disconnect() } * to clean up properly. * <p> * By default the standard output and standard error streams of the * remote process are transmitted over the same connection, readable * from the input stream returned by * {@link org.apache.commons.net.bsd.RExecClient#getInputStream getInputStream() } * . However, it is * possible to tell the rshd daemon to return the standard error * stream over a separate connection, readable from the input stream * returned by {@link org.apache.commons.net.bsd.RExecClient#getErrorStream getErrorStream() } * . You * can specify that a separate connection should be created for standard * error by setting the boolean <code> separateErrorStream </code> * parameter of {@link #rcommand rcommand() } to <code> true </code>. * The standard input of the remote process can be written to through * the output stream returned by * {@link org.apache.commons.net.bsd.RExecClient#getOutputStream getOutputStream() } * . * <p> * <p> * @author Daniel F. Savarese * @see org.apache.commons.net.SocketClient * @see RExecClient * @see RLoginClient ***/ public class RCommandClient extends RExecClient { /*** * The default rshell port. Set to 514 in BSD Unix. ***/ public static final int DEFAULT_PORT = 514; /*** * The smallest port number an rcmd client may use. By BSD convention * this number is 512. ***/ public static final int MIN_CLIENT_PORT = 512; /*** * The largest port number an rcmd client may use. By BSD convention * this number is 1023. ***/ public static final int MAX_CLIENT_PORT = 1023; // Overrides method in RExecClient in order to implement proper // port number limitations. InputStream _createErrorStream() throws IOException { int localPort; ServerSocket server; Socket socket; localPort = MAX_CLIENT_PORT; server = null; // Keep compiler from barfing for (localPort = MAX_CLIENT_PORT; localPort >= MIN_CLIENT_PORT; --localPort) { try { server = _socketFactory_.createServerSocket(localPort, 1, getLocalAddress()); } catch (SocketException e) { continue; } break; } if (localPort < MIN_CLIENT_PORT) throw new BindException("All ports in use."); _output_.write(Integer.toString(server.getLocalPort()).getBytes()); _output_.write('\0'); _output_.flush(); socket = server.accept(); server.close(); if (isRemoteVerificationEnabled() && !verifyRemote(socket)) { socket.close(); throw new IOException("Security violation: unexpected connection attempt by " + socket.getInetAddress().getHostAddress()); } return (new SocketInputStream(socket, socket.getInputStream())); } /*** * The default RCommandClient constructor. Initializes the * default port to <code> DEFAULT_PORT </code>. ***/ public RCommandClient() { setDefaultPort(DEFAULT_PORT); } /*** * Opens a Socket connected to a remote host at the specified port and * originating from the specified local address using a port in a range * acceptable to the BSD rshell daemon. * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_ _connectAction_() } * is called to perform connection initialization actions. * <p> * @param host The remote host. * @param port The port to connect to on the remote host. * @param localAddr The local address to use. * @exception SocketException If the socket timeout could not be set. * @exception BindException If all acceptable rshell ports are in use. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. ***/ public void connect(InetAddress host, int port, InetAddress localAddr) throws SocketException, BindException, IOException { int localPort; localPort = MAX_CLIENT_PORT; for (localPort = MAX_CLIENT_PORT; localPort >= MIN_CLIENT_PORT; --localPort) { try { _socket_ = _socketFactory_.createSocket(host, port, localAddr, localPort); } catch (SocketException e) { continue; } break; } if (localPort < MIN_CLIENT_PORT) throw new BindException("All ports in use or insufficient permssion."); _connectAction_(); } /*** * Opens a Socket connected to a remote host at the specified port and * originating from the current host at a port in a range acceptable * to the BSD rshell daemon. * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_ _connectAction_() } * is called to perform connection initialization actions. * <p> * @param host The remote host. * @param port The port to connect to on the remote host. * @exception SocketException If the socket timeout could not be set. * @exception BindException If all acceptable rshell ports are in use. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. ***/ public void connect(InetAddress host, int port) throws SocketException, IOException { connect(host, port, InetAddress.getLocalHost()); } /*** * Opens a Socket connected to a remote host at the specified port and * originating from the current host at a port in a range acceptable * to the BSD rshell daemon. * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_ _connectAction_() } * is called to perform connection initialization actions. * <p> * @param hostname The name of the remote host. * @param port The port to connect to on the remote host. * @exception SocketException If the socket timeout could not be set. * @exception BindException If all acceptable rshell ports are in use. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. * @exception UnknownHostException If the hostname cannot be resolved. ***/ public void connect(String hostname, int port) throws SocketException, IOException { connect(InetAddress.getByName(hostname), port, InetAddress.getLocalHost()); } /*** * Opens a Socket connected to a remote host at the specified port and * originating from the specified local address using a port in a range * acceptable to the BSD rshell daemon. * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_ _connectAction_() } * is called to perform connection initialization actions. * <p> * @param hostname The remote host. * @param port The port to connect to on the remote host. * @param localAddr The local address to use. * @exception SocketException If the socket timeout could not be set. * @exception BindException If all acceptable rshell ports are in use. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. ***/ public void connect(String hostname, int port, InetAddress localAddr) throws SocketException, IOException { connect(InetAddress.getByName(hostname), port, localAddr); } /*** * Opens a Socket connected to a remote host at the specified port and * originating from the specified local address and port. The * local port must lie between <code> MIN_CLIENT_PORT </code> and * <code> MAX_CLIENT_PORT </code> or an IllegalArgumentException will * be thrown. * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_ _connectAction_() } * is called to perform connection initialization actions. * <p> * @param host The remote host. * @param port The port to connect to on the remote host. * @param localAddr The local address to use. * @param localPort The local port to use. * @exception SocketException If the socket timeout could not be set. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. * @exception IllegalArgumentException If an invalid local port number * is specified. ***/ public void connect(InetAddress host, int port, InetAddress localAddr, int localPort) throws SocketException, IOException, IllegalArgumentException { if (localPort < MIN_CLIENT_PORT || localPort > MAX_CLIENT_PORT) throw new IllegalArgumentException("Invalid port number " + localPort); super.connect(host, port, localAddr, localPort); } /*** * Opens a Socket connected to a remote host at the specified port and * originating from the specified local address and port. The * local port must lie between <code> MIN_CLIENT_PORT </code> and * <code> MAX_CLIENT_PORT </code> or an IllegalArgumentException will * be thrown. * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_ _connectAction_() } * is called to perform connection initialization actions. * <p> * @param hostname The name of the remote host. * @param port The port to connect to on the remote host. * @param localAddr The local address to use. * @param localPort The local port to use. * @exception SocketException If the socket timeout could not be set. * @exception IOException If the socket could not be opened. In most * cases you will only want to catch IOException since SocketException is * derived from it. * @exception UnknownHostException If the hostname cannot be resolved. * @exception IllegalArgumentException If an invalid local port number * is specified. ***/ public void connect(String hostname, int port, InetAddress localAddr, int localPort) throws SocketException, IOException, IllegalArgumentException { if (localPort < MIN_CLIENT_PORT || localPort > MAX_CLIENT_PORT) throw new IllegalArgumentException("Invalid port number " + localPort); super.connect(hostname, port, localAddr, localPort); } /*** * Remotely executes a command through the rshd daemon on the server * to which the RCommandClient is connected. After calling this method, * you may interact with the remote process through its standard input, * output, and error streams. You will typically be able to detect * the termination of the remote process after reaching end of file * on its standard output (accessible through * {@link #getInputStream getInputStream() }. Disconnecting * from the server or closing the process streams before reaching * end of file will not necessarily terminate the remote process. * <p> * If a separate error stream is requested, the remote server will * connect to a local socket opened by RCommandClient, providing an * independent stream through which standard error will be transmitted. * The local socket must originate from a secure port (512 - 1023), * and rcommand() ensures that this will be so. * RCommandClient will also do a simple security check when it accepts a * connection for this error stream. If the connection does not originate * from the remote server, an IOException will be thrown. This serves as * a simple protection against possible hijacking of the error stream by * an attacker monitoring the rexec() negotiation. You may disable this * behavior with * {@link org.apache.commons.net.bsd.RExecClient#setRemoteVerificationEnabled setRemoteVerificationEnabled()} * . * <p> * @param localUsername The user account on the local machine that is * requesting the command execution. * @param remoteUsername The account name on the server through which to * execute the command. * @param command The command, including any arguments, to execute. * @param separateErrorStream True if you would like the standard error * to be transmitted through a different stream than standard output. * False if not. * @exception IOException If the rcommand() attempt fails. The exception * will contain a message indicating the nature of the failure. ***/ public void rcommand(String localUsername, String remoteUsername, String command, boolean separateErrorStream) throws IOException { rexec(localUsername, remoteUsername, command, separateErrorStream); } /*** * Same as * <code> rcommand(localUsername, remoteUsername, command, false); </code> ***/ public void rcommand(String localUsername, String remoteUsername, String command) throws IOException { rcommand(localUsername, remoteUsername, command, false); } }