    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
    018    package org.apache.commons.net.bsd;
    019
    020    import java.io.IOException;
    021    import java.io.InputStream;
    022    import java.net.BindException;
    023    import java.net.InetAddress;
    024    import java.net.ServerSocket;
    025    import java.net.Socket;
    026    import java.net.SocketException;
    027    import java.net.UnknownHostException;
    028
    029    import 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
    089    public 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());
    139            _output_.write('\0');
    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            _connectAction_();
    210        }
    211
    212
    213
    214        /***
    215         * Opens a Socket connected to a remote host at the specified port and
    216         * originating from the current host at a port in a range acceptable
    217         * to the BSD rshell daemon.
    218         * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    219         * is called to perform connection initialization actions.
    220         * <p>
    221         * @param host  The remote host.
    222         * @param port  The port to connect to on the remote host.
    223         * @exception SocketException If the socket timeout could not be set.
    224         * @exception BindException If all acceptable rshell ports are in use.
    225         * @exception IOException If the socket could not be opened.  In most
    226         *  cases you will only want to catch IOException since SocketException is
    227         *  derived from it.
    228         ***/
    229        @Override
    230        public void connect(InetAddress host, int port)
    231        throws SocketException, IOException
    232        {
    233            connect(host, port, InetAddress.getLocalHost());
    234        }
    235
    236
    237        /***
    238         * Opens a Socket connected to a remote host at the specified port and
    239         * originating from the current host at a port in a range acceptable
    240         * to the BSD rshell daemon.
    241         * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    242         * is called to perform connection initialization actions.
    243         * <p>
    244         * @param hostname  The name of the remote host.
    245         * @param port  The port to connect to on the remote host.
    246         * @exception SocketException If the socket timeout could not be set.
    247         * @exception BindException If all acceptable rshell ports are in use.
    248         * @exception IOException If the socket could not be opened.  In most
    249         *  cases you will only want to catch IOException since SocketException is
    250         *  derived from it.
    251         * @exception UnknownHostException If the hostname cannot be resolved.
    252         ***/
    253        @Override
    254        public void connect(String hostname, int port)
    255        throws SocketException, IOException, UnknownHostException
    256        {
    257            connect(InetAddress.getByName(hostname), port, InetAddress.getLocalHost());
    258        }
    259
    260
    261        /***
    262         * Opens a Socket connected to a remote host at the specified port and
    263         * originating from the specified local address using a port in a range
    264         * acceptable to the BSD rshell daemon.
    265         * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    266         * is called to perform connection initialization actions.
    267         * <p>
    268         * @param hostname  The remote host.
    269         * @param port  The port to connect to on the remote host.
    270         * @param localAddr  The local address to use.
    271         * @exception SocketException If the socket timeout could not be set.
    272         * @exception BindException If all acceptable rshell ports are in use.
    273         * @exception IOException If the socket could not be opened.  In most
    274         *  cases you will only want to catch IOException since SocketException is
    275         *  derived from it.
    276         ***/
    277        public void connect(String hostname, int port, InetAddress localAddr)
    278        throws SocketException, IOException
    279        {
    280            connect(InetAddress.getByName(hostname), port, localAddr);
    281        }
    282
    283
    284        /***
    285         * Opens a Socket connected to a remote host at the specified port and
    286         * originating from the specified local address and port. The
    287         * local port must lie between <code> MIN_CLIENT_PORT </code> and
    288         * <code> MAX_CLIENT_PORT </code> or an IllegalArgumentException will
    289         * be thrown.
    290         * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    291         * is called to perform connection initialization actions.
    292         * <p>
    293         * @param host  The remote host.
    294         * @param port  The port to connect to on the remote host.
    295         * @param localAddr  The local address to use.
    296         * @param localPort  The local port to use.
    297         * @exception SocketException If the socket timeout could not be set.
    298         * @exception IOException If the socket could not be opened.  In most
    299         *  cases you will only want to catch IOException since SocketException is
    300         *  derived from it.
    301         * @exception IllegalArgumentException If an invalid local port number
    302         *            is specified.
    303         ***/
    304        @Override
    305        public void connect(InetAddress host, int port,
    306                            InetAddress localAddr, int localPort)
    307        throws SocketException, IOException, IllegalArgumentException
    308        {
    309            if (localPort < MIN_CLIENT_PORT || localPort > MAX_CLIENT_PORT)
    310                throw new IllegalArgumentException("Invalid port number " + localPort);
    311            super.connect(host, port, localAddr, localPort);
    312        }
    313
    314
    315        /***
    316         * Opens a Socket connected to a remote host at the specified port and
    317         * originating from the specified local address and port. The
    318         * local port must lie between <code> MIN_CLIENT_PORT </code> and
    319         * <code> MAX_CLIENT_PORT </code> or an IllegalArgumentException will
    320         * be thrown.
    321         * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_  _connectAction_() }
    322         * is called to perform connection initialization actions.
    323         * <p>
    324         * @param hostname  The name of the remote host.
    325         * @param port  The port to connect to on the remote host.
    326         * @param localAddr  The local address to use.
    327         * @param localPort  The local port to use.
    328         * @exception SocketException If the socket timeout could not be set.
    329         * @exception IOException If the socket could not be opened.  In most
    330         *  cases you will only want to catch IOException since SocketException is
    331         *  derived from it.
    332         * @exception UnknownHostException If the hostname cannot be resolved.
    333         * @exception IllegalArgumentException If an invalid local port number
    334         *            is specified.
    335         ***/
    336        @Override
    337        public void connect(String hostname, int port,
    338                            InetAddress localAddr, int localPort)
    339        throws SocketException, IOException, IllegalArgumentException, UnknownHostException
    340        {
    341            if (localPort < MIN_CLIENT_PORT || localPort > MAX_CLIENT_PORT)
    342                throw new IllegalArgumentException("Invalid port number " + localPort);
    343            super.connect(hostname, port, localAddr, localPort);
    344        }
    345
    346
    347        /***
    348         * Remotely executes a command through the rshd daemon on the server
    349         * to which the RCommandClient is connected.  After calling this method,
    350         * you may interact with the remote process through its standard input,
    351         * output, and error streams.  You will typically be able to detect
    352         * the termination of the remote process after reaching end of file
    353         * on its standard output (accessible through
    354         * {@link #getInputStream  getInputStream() }.  Disconnecting
    355         * from the server or closing the process streams before reaching
    356         * end of file will not necessarily terminate the remote process.
    357         * <p>
    358         * If a separate error stream is requested, the remote server will
    359         * connect to a local socket opened by RCommandClient, providing an
    360         * independent stream through which standard error will be transmitted.
    361         * The local socket must originate from a secure port (512 - 1023),
    362         * and rcommand() ensures that this will be so.
    363         * RCommandClient will also do a simple security check when it accepts a
    364         * connection for this error stream.  If the connection does not originate
    365         * from the remote server, an IOException will be thrown.  This serves as
    366         * a simple protection against possible hijacking of the error stream by
    367         * an attacker monitoring the rexec() negotiation.  You may disable this
    368         * behavior with
    369         * {@link org.apache.commons.net.bsd.RExecClient#setRemoteVerificationEnabled setRemoteVerificationEnabled()}
    370         * .
    371         * <p>
    372         * @param localUsername  The user account on the local machine that is
    373         *        requesting the command execution.
    374         * @param remoteUsername  The account name on the server through which to
    375         *        execute the command.
    376         * @param command   The command, including any arguments, to execute.
    377         * @param separateErrorStream True if you would like the standard error
    378         *        to be transmitted through a different stream than standard output.
    379         *        False if not.
    380         * @exception IOException If the rcommand() attempt fails.  The exception
    381         *            will contain a message indicating the nature of the failure.
    382         ***/
    383        public void rcommand(String localUsername, String remoteUsername,
    384                             String command, boolean separateErrorStream)
    385        throws IOException
    386        {
    387            rexec(localUsername, remoteUsername, command, separateErrorStream);
    388        }
    389
    390
    391        /***
    392         * Same as
    393         * <code> rcommand(localUsername, remoteUsername, command, false); </code>
    394         ***/
    395        public void rcommand(String localUsername, String remoteUsername,
    396                             String command)
    397        throws IOException
    398        {
    399            rcommand(localUsername, remoteUsername, command, false);
    400        }
    401
    402    }
    403