    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.net.bsd;
    019
    020import java.io.IOException;
    021import java.io.InputStream;
    022import java.net.BindException;
    023import java.net.InetAddress;
    024import java.net.ServerSocket;
    025import java.net.Socket;
    026import java.net.SocketException;
    027import java.net.UnknownHostException;
    028
    029import org.apache.commons.net.io.SocketInputStream;
    030
    031/***
    032 * RCommandClient is very similar to
    033 * {@link org.apache.commons.net.bsd.RExecClient},
    034 * from which it is derived, and implements the rcmd() facility that
    035 * first appeared in 4.2BSD Unix.  rcmd() is the facility used by the rsh
    036 * (rshell) and other commands to execute a command on another machine
    037 * from a trusted host without issuing a password.  The trust relationship
    038 * between two machines is established by the contents of a machine's
    039 * /etc/hosts.equiv file and a user's .rhosts file.  These files specify
    040 * from which hosts and accounts on those hosts rcmd() requests will be
    041 * accepted.  The only additional measure for establishing trust is that
    042 * all client connections must originate from a port between 512 and 1023.
    043 * Consequently, there is an upper limit to the number of rcmd connections
    044 * that can be running simultaneously.   The required ports are reserved
    045 * ports on Unix systems, and can only be bound by a
    046 * process running with root permissions (to accomplish this rsh, rlogin,
    047 * and related commands usualy have the suid bit set).  Therefore, on a
    048 * Unix system, you will only be able to successfully use the RCommandClient
    049 * class if the process runs as root.  However, there is no such restriction
    050 * on Windows95 and some other systems.  The security risks are obvious.
    051 * However, when carefully used, rcmd() can be very useful when used behind
    052 * a firewall.
    053 * <p>
    054 * As with virtually all of the client classes in org.apache.commons.net, this
    055 * class derives from SocketClient.  But it overrides most of its connection
    056 * methods so that the local Socket will originate from an acceptable
    057 * rshell port.  The way to use RCommandClient is to first connect
    058 * to the server, call the {@link #rcommand  rcommand() } method,
    059 * and then
    060 * fetch the connection's input, output, and optionally error streams.
    061 * Interaction with the remote command is controlled entirely through the
    062 * I/O streams.  Once you have finished processing the streams, you should
    063 * invoke {@link org.apache.commons.net.bsd.RExecClient#disconnect disconnect() }
    064 *  to clean up properly.
    065 * <p>
    066 * By default the standard output and standard error streams of the
    067 * remote process are transmitted over the same connection, readable
    068 * from the input stream returned by
    069 * {@link org.apache.commons.net.bsd.RExecClient#getInputStream getInputStream() }
    070 * .  However, it is
    071 * possible to tell the rshd daemon to return the standard error
    072 * stream over a separate connection, readable from the input stream
    073 * returned by {@link org.apache.commons.net.bsd.RExecClient#getErrorStream getErrorStream() }
    074 * .  You
    075 * can specify that a separate connection should be created for standard
    076 * error by setting the boolean <code> separateErrorStream </code>
    077 * parameter of {@link #rcommand  rcommand() } to <code> true </code>.
    078 * The standard input of the remote process can be written to through
    079 * the output stream returned by
    080 * {@link org.apache.commons.net.bsd.RExecClient#getOutputStream getOutputStream() }
    081 * .
    082 * <p>
    083 * <p>
    084 * @see org.apache.commons.net.SocketClient
    085 * @see RExecClient
    086 * @see RLoginClient
    087 ***/
    088
    089public class RCommandClient extends RExecClient
    090{
    091    /***
    092     * The default rshell port.  Set to 514 in BSD Unix.
    093     ***/
    094    public static final int DEFAULT_PORT = 514;
    095
    096    /***
    097     * The smallest port number an rcmd client may use.  By BSD convention
    098     * this number is 512.
    099     ***/
    100    public static final int MIN_CLIENT_PORT = 512;
    101
    102    /***
    103     * The largest port number an rcmd client may use.  By BSD convention
    104     * this number is 1023.
    105     ***/
    106    public static final int MAX_CLIENT_PORT = 1023;
    107
    108    // Overrides method in RExecClient in order to implement proper
    109    // port number limitations.
    110    @Override
    111    InputStream _createErrorStream() throws IOException
    112    {
    113        int localPort;
    114        ServerSocket server;
    115        Socket socket;
    116
    117        localPort = MAX_CLIENT_PORT;
    118        server = null; // Keep compiler from barfing
    119
    120        for (localPort = MAX_CLIENT_PORT; localPort >= MIN_CLIENT_PORT; --localPort)
    121        {
    122            try
    123            {
    124                server = _serverSocketFactory_.createServerSocket(localPort, 1,
    125                         getLocalAddress());
    126                break; // got a socket
    127            }
    128            catch (SocketException e)
    129            {
    130                continue;
    131            }
    132        }
    133
    134        if (server == null) {
    135            throw new BindException("All ports in use.");
    136        }
    137
    138        _output_.write(Integer.toString(server.getLocalPort()).getBytes("UTF-8")); // $NON-NLS
    139        _output_.write(NULL_CHAR);
    140        _output_.flush();
    141
    142        socket = server.accept();
    143        server.close();
    144
    145        if (isRemoteVerificationEnabled() && !verifyRemote(socket))
    146        {
    147            socket.close();
    148            throw new IOException(
    149                "Security violation: unexpected connection attempt by " +
    150                socket.getInetAddress().getHostAddress());
    151        }
    152
    153        return (new SocketInputStream(socket, socket.getInputStream()));
    154    }
    155
    156    /***
    157     * The default RCommandClient constructor.  Initializes the
    158     * default port to <code> DEFAULT_PORT </code>.
    159     ***/
    160    public RCommandClient()
    161    {
    162        setDefaultPort(DEFAULT_PORT);
    163    }
    164
    165
    166    /***
    167     * Opens a Socket connected to a remote host at the specified port and
    168     * originating from the specified local address using a port in a range
    169     * acceptable to the BSD rshell daemon.
    170     * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    171     * is called to perform connection initialization actions.
    172     * <p>
    173     * @param host  The remote host.
    174     * @param port  The port to connect to on the remote host.
    175     * @param localAddr  The local address to use.
    176     * @exception SocketException If the socket timeout could not be set.
    177     * @exception BindException If all acceptable rshell ports are in use.
    178     * @exception IOException If the socket could not be opened.  In most
    179     *  cases you will only want to catch IOException since SocketException is
    180     *  derived from it.
    181     ***/
    182    public void connect(InetAddress host, int port, InetAddress localAddr)
    183    throws SocketException, BindException, IOException
    184    {
    185        int localPort;
    186
    187        localPort = MAX_CLIENT_PORT;
    188
    189        for (localPort = MAX_CLIENT_PORT; localPort >= MIN_CLIENT_PORT; --localPort)
    190        {
    191            try
    192            {
    193                _socket_ =
    194                    _socketFactory_.createSocket(host, port, localAddr, localPort);
    195            }
    196            catch (BindException be) {
    197                continue;
    198            }
    199            catch (SocketException e)
    200            {
    201                continue;
    202            }
    203            break;
    204        }
    205
    206        if (localPort < MIN_CLIENT_PORT) {
    207            throw new BindException("All ports in use or insufficient permssion.");
    208        }
    209
    210        _connectAction_();
    211    }
    212
    213
    214
    215    /***
    216     * Opens a Socket connected to a remote host at the specified port and
    217     * originating from the current host at a port in a range acceptable
    218     * to the BSD rshell daemon.
    219     * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    220     * is called to perform connection initialization actions.
    221     * <p>
    222     * @param host  The remote host.
    223     * @param port  The port to connect to on the remote host.
    224     * @exception SocketException If the socket timeout could not be set.
    225     * @exception BindException If all acceptable rshell ports are in use.
    226     * @exception IOException If the socket could not be opened.  In most
    227     *  cases you will only want to catch IOException since SocketException is
    228     *  derived from it.
    229     ***/
    230    @Override
    231    public void connect(InetAddress host, int port)
    232    throws SocketException, IOException
    233    {
    234        connect(host, port, InetAddress.getLocalHost());
    235    }
    236
    237
    238    /***
    239     * Opens a Socket connected to a remote host at the specified port and
    240     * originating from the current host at a port in a range acceptable
    241     * to the BSD rshell daemon.
    242     * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    243     * is called to perform connection initialization actions.
    244     * <p>
    245     * @param hostname  The name of the remote host.
    246     * @param port  The port to connect to on the remote host.
    247     * @exception SocketException If the socket timeout could not be set.
    248     * @exception BindException If all acceptable rshell ports are in use.
    249     * @exception IOException If the socket could not be opened.  In most
    250     *  cases you will only want to catch IOException since SocketException is
    251     *  derived from it.
    252     * @exception UnknownHostException If the hostname cannot be resolved.
    253     ***/
    254    @Override
    255    public void connect(String hostname, int port)
    256    throws SocketException, IOException, UnknownHostException
    257    {
    258        connect(InetAddress.getByName(hostname), port, InetAddress.getLocalHost());
    259    }
    260
    261
    262    /***
    263     * Opens a Socket connected to a remote host at the specified port and
    264     * originating from the specified local address using a port in a range
    265     * acceptable to the BSD rshell daemon.
    266     * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    267     * is called to perform connection initialization actions.
    268     * <p>
    269     * @param hostname  The remote host.
    270     * @param port  The port to connect to on the remote host.
    271     * @param localAddr  The local address to use.
    272     * @exception SocketException If the socket timeout could not be set.
    273     * @exception BindException If all acceptable rshell ports are in use.
    274     * @exception IOException If the socket could not be opened.  In most
    275     *  cases you will only want to catch IOException since SocketException is
    276     *  derived from it.
    277     ***/
    278    public void connect(String hostname, int port, InetAddress localAddr)
    279    throws SocketException, IOException
    280    {
    281        connect(InetAddress.getByName(hostname), port, localAddr);
    282    }
    283
    284
    285    /***
    286     * Opens a Socket connected to a remote host at the specified port and
    287     * originating from the specified local address and port. The
    288     * local port must lie between <code> MIN_CLIENT_PORT </code> and
    289     * <code> MAX_CLIENT_PORT </code> or an IllegalArgumentException will
    290     * be thrown.
    291     * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    292     * is called to perform connection initialization actions.
    293     * <p>
    294     * @param host  The remote host.
    295     * @param port  The port to connect to on the remote host.
    296     * @param localAddr  The local address to use.
    297     * @param localPort  The local port to use.
    298     * @exception SocketException If the socket timeout could not be set.
    299     * @exception IOException If the socket could not be opened.  In most
    300     *  cases you will only want to catch IOException since SocketException is
    301     *  derived from it.
    302     * @exception IllegalArgumentException If an invalid local port number
    303     *            is specified.
    304     ***/
    305    @Override
    306    public void connect(InetAddress host, int port,
    307                        InetAddress localAddr, int localPort)
    308    throws SocketException, IOException, IllegalArgumentException
    309    {
    310        if (localPort < MIN_CLIENT_PORT || localPort > MAX_CLIENT_PORT) {
    311            throw new IllegalArgumentException("Invalid port number " + localPort);
    312        }
    313        super.connect(host, port, localAddr, localPort);
    314    }
    315
    316
    317    /***
    318     * Opens a Socket connected to a remote host at the specified port and
    319     * originating from the specified local address and port. The
    320     * local port must lie between <code> MIN_CLIENT_PORT </code> and
    321     * <code> MAX_CLIENT_PORT </code> or an IllegalArgumentException will
    322     * be thrown.
    323     * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    324     * is called to perform connection initialization actions.
    325     * <p>
    326     * @param hostname  The name of the remote host.
    327     * @param port  The port to connect to on the remote host.
    328     * @param localAddr  The local address to use.
    329     * @param localPort  The local port to use.
    330     * @exception SocketException If the socket timeout could not be set.
    331     * @exception IOException If the socket could not be opened.  In most
    332     *  cases you will only want to catch IOException since SocketException is
    333     *  derived from it.
    334     * @exception UnknownHostException If the hostname cannot be resolved.
    335     * @exception IllegalArgumentException If an invalid local port number
    336     *            is specified.
    337     ***/
    338    @Override
    339    public void connect(String hostname, int port,
    340                        InetAddress localAddr, int localPort)
    341    throws SocketException, IOException, IllegalArgumentException, UnknownHostException
    342    {
    343        if (localPort < MIN_CLIENT_PORT || localPort > MAX_CLIENT_PORT) {
    344            throw new IllegalArgumentException("Invalid port number " + localPort);
    345        }
    346        super.connect(hostname, port, localAddr, localPort);
    347    }
    348
    349
    350    /***
    351     * Remotely executes a command through the rshd daemon on the server
    352     * to which the RCommandClient is connected.  After calling this method,
    353     * you may interact with the remote process through its standard input,
    354     * output, and error streams.  You will typically be able to detect
    355     * the termination of the remote process after reaching end of file
    356     * on its standard output (accessible through
    357     * {@link #getInputStream  getInputStream() }.  Disconnecting
    358     * from the server or closing the process streams before reaching
    359     * end of file will not necessarily terminate the remote process.
    360     * <p>
    361     * If a separate error stream is requested, the remote server will
    362     * connect to a local socket opened by RCommandClient, providing an
    363     * independent stream through which standard error will be transmitted.
    364     * The local socket must originate from a secure port (512 - 1023),
    365     * and rcommand() ensures that this will be so.
    366     * RCommandClient will also do a simple security check when it accepts a
    367     * connection for this error stream.  If the connection does not originate
    368     * from the remote server, an IOException will be thrown.  This serves as
    369     * a simple protection against possible hijacking of the error stream by
    370     * an attacker monitoring the rexec() negotiation.  You may disable this
    371     * behavior with
    372     * {@link org.apache.commons.net.bsd.RExecClient#setRemoteVerificationEnabled setRemoteVerificationEnabled()}
    373     * .
    374     * <p>
    375     * @param localUsername  The user account on the local machine that is
    376     *        requesting the command execution.
    377     * @param remoteUsername  The account name on the server through which to
    378     *        execute the command.
    379     * @param command   The command, including any arguments, to execute.
    380     * @param separateErrorStream True if you would like the standard error
    381     *        to be transmitted through a different stream than standard output.
    382     *        False if not.
    383     * @exception IOException If the rcommand() attempt fails.  The exception
    384     *            will contain a message indicating the nature of the failure.
    385     ***/
    386    public void rcommand(String localUsername, String remoteUsername,
    387                         String command, boolean separateErrorStream)
    388    throws IOException
    389    {
    390        rexec(localUsername, remoteUsername, command, separateErrorStream);
    391    }
    392
    393
    394    /***
    395     * Same as
    396     * <code> rcommand(localUsername, remoteUsername, command, false); </code>
    397     ***/
    398    public void rcommand(String localUsername, String remoteUsername,
    399                         String command)
    400    throws IOException
    401    {
    402        rcommand(localUsername, remoteUsername, command, false);
    403    }
    404
    405}
    406