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