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 * @author Daniel F. Savarese
085 * @see org.apache.commons.net.SocketClient
086 * @see RExecClient
087 * @see RLoginClient
088 ***/
089
090 public class RCommandClient extends RExecClient
091 {
092 /***
093 * The default rshell port. Set to 514 in BSD Unix.
094 ***/
095 public static final int DEFAULT_PORT = 514;
096
097 /***
098 * The smallest port number an rcmd client may use. By BSD convention
099 * this number is 512.
100 ***/
101 public static final int MIN_CLIENT_PORT = 512;
102
103 /***
104 * The largest port number an rcmd client may use. By BSD convention
105 * this number is 1023.
106 ***/
107 public static final int MAX_CLIENT_PORT = 1023;
108
109 // Overrides method in RExecClient in order to implement proper
110 // port number limitations.
111 @Override
112 InputStream _createErrorStream() throws IOException
113 {
114 int localPort;
115 ServerSocket server;
116 Socket socket;
117
118 localPort = MAX_CLIENT_PORT;
119 server = null; // Keep compiler from barfing
120
121 for (localPort = MAX_CLIENT_PORT; localPort >= MIN_CLIENT_PORT; --localPort)
122 {
123 try
124 {
125 server = _serverSocketFactory_.createServerSocket(localPort, 1,
126 getLocalAddress());
127 break; // got a socket
128 }
129 catch (SocketException e)
130 {
131 continue;
132 }
133 }
134
135 if (server == null) {
136 throw new BindException("All ports in use.");
137 }
138
139 _output_.write(Integer.toString(server.getLocalPort()).getBytes());
140 _output_.write('\0');
141 _output_.flush();
142
143 socket = server.accept();
144 server.close();
145
146 if (isRemoteVerificationEnabled() && !verifyRemote(socket))
147 {
148 socket.close();
149 throw new IOException(
150 "Security violation: unexpected connection attempt by " +
151 socket.getInetAddress().getHostAddress());
152 }
153
154 return (new SocketInputStream(socket, socket.getInputStream()));
155 }
156
157 /***
158 * The default RCommandClient constructor. Initializes the
159 * default port to <code> DEFAULT_PORT </code>.
160 ***/
161 public RCommandClient()
162 {
163 setDefaultPort(DEFAULT_PORT);
164 }
165
166
167 /***
168 * Opens a Socket connected to a remote host at the specified port and
169 * originating from the specified local address using a port in a range
170 * acceptable to the BSD rshell daemon.
171 * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_ _connectAction_() }
172 * is called to perform connection initialization actions.
173 * <p>
174 * @param host The remote host.
175 * @param port The port to connect to on the remote host.
176 * @param localAddr The local address to use.
177 * @exception SocketException If the socket timeout could not be set.
178 * @exception BindException If all acceptable rshell ports are in use.
179 * @exception IOException If the socket could not be opened. In most
180 * cases you will only want to catch IOException since SocketException is
181 * derived from it.
182 ***/
183 public void connect(InetAddress host, int port, InetAddress localAddr)
184 throws SocketException, BindException, IOException
185 {
186 int localPort;
187
188 localPort = MAX_CLIENT_PORT;
189
190 for (localPort = MAX_CLIENT_PORT; localPort >= MIN_CLIENT_PORT; --localPort)
191 {
192 try
193 {
194 _socket_ =
195 _socketFactory_.createSocket(host, port, localAddr, localPort);
196 }
197 catch (BindException be) {
198 continue;
199 }
200 catch (SocketException e)
201 {
202 continue;
203 }
204 break;
205 }
206
207 if (localPort < MIN_CLIENT_PORT)
208 throw new BindException("All ports in use or insufficient permssion.");
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 super.connect(host, port, localAddr, localPort);
313 }
314
315
316 /***
317 * Opens a Socket connected to a remote host at the specified port and
318 * originating from the specified local address and port. The
319 * local port must lie between <code> MIN_CLIENT_PORT </code> and
320 * <code> MAX_CLIENT_PORT </code> or an IllegalArgumentException will
321 * be thrown.
322 * Before returning, {@link org.apache.commons.net.SocketClient#_connectAction_ _connectAction_() }
323 * is called to perform connection initialization actions.
324 * <p>
325 * @param hostname The name of the remote host.
326 * @param port The port to connect to on the remote host.
327 * @param localAddr The local address to use.
328 * @param localPort The local port to use.
329 * @exception SocketException If the socket timeout could not be set.
330 * @exception IOException If the socket could not be opened. In most
331 * cases you will only want to catch IOException since SocketException is
332 * derived from it.
333 * @exception UnknownHostException If the hostname cannot be resolved.
334 * @exception IllegalArgumentException If an invalid local port number
335 * is specified.
336 ***/
337 @Override
338 public void connect(String hostname, int port,
339 InetAddress localAddr, int localPort)
340 throws SocketException, IOException, IllegalArgumentException, UnknownHostException
341 {
342 if (localPort < MIN_CLIENT_PORT || localPort > MAX_CLIENT_PORT)
343 throw new IllegalArgumentException("Invalid port number " + localPort);
344 super.connect(hostname, port, localAddr, localPort);
345 }
346
347
348 /***
349 * Remotely executes a command through the rshd daemon on the server
350 * to which the RCommandClient is connected. After calling this method,
351 * you may interact with the remote process through its standard input,
352 * output, and error streams. You will typically be able to detect
353 * the termination of the remote process after reaching end of file
354 * on its standard output (accessible through
355 * {@link #getInputStream getInputStream() }. Disconnecting
356 * from the server or closing the process streams before reaching
357 * end of file will not necessarily terminate the remote process.
358 * <p>
359 * If a separate error stream is requested, the remote server will
360 * connect to a local socket opened by RCommandClient, providing an
361 * independent stream through which standard error will be transmitted.
362 * The local socket must originate from a secure port (512 - 1023),
363 * and rcommand() ensures that this will be so.
364 * RCommandClient will also do a simple security check when it accepts a
365 * connection for this error stream. If the connection does not originate
366 * from the remote server, an IOException will be thrown. This serves as
367 * a simple protection against possible hijacking of the error stream by
368 * an attacker monitoring the rexec() negotiation. You may disable this
369 * behavior with
370 * {@link org.apache.commons.net.bsd.RExecClient#setRemoteVerificationEnabled setRemoteVerificationEnabled()}
371 * .
372 * <p>
373 * @param localUsername The user account on the local machine that is
374 * requesting the command execution.
375 * @param remoteUsername The account name on the server through which to
376 * execute the command.
377 * @param command The command, including any arguments, to execute.
378 * @param separateErrorStream True if you would like the standard error
379 * to be transmitted through a different stream than standard output.
380 * False if not.
381 * @exception IOException If the rcommand() attempt fails. The exception
382 * will contain a message indicating the nature of the failure.
383 ***/
384 public void rcommand(String localUsername, String remoteUsername,
385 String command, boolean separateErrorStream)
386 throws IOException
387 {
388 rexec(localUsername, remoteUsername, command, separateErrorStream);
389 }
390
391
392 /***
393 * Same as
394 * <code> rcommand(localUsername, remoteUsername, command, false); </code>
395 ***/
396 public void rcommand(String localUsername, String remoteUsername,
397 String command)
398 throws IOException
399 {
400 rcommand(localUsername, remoteUsername, command, false);
401 }
402
403 }
404