1 /*
2 * junixsocket
3 *
4 * Copyright 2009-2024 Christian Kohlschütter
5 *
6 * Licensed under the Apache License, Version 2.0 (the "License");
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18 package org.newsclub.net.unix.demo.rmi.fd;
19
20 import java.io.IOException;
21 import java.rmi.AlreadyBoundException;
22
23 import org.newsclub.net.unix.rmi.AFUNIXNaming;
24
25 /**
26 * Demonstrates how to read/write files via FileDescriptors that are exchanged via RMI.
27 *
28 * This allows reading/writing from and to files that are otherwise not even accessible by the user.
29 * For example, starting the {@link StreamServer} as root and the {@link StreamClient} as a
30 * non-privileged user will allow the non-privileged user to read files only accessible to root.
31 *
32 * NOTE: For obvious security reasons, running this server without modification is not advised for
33 * anything other than demo purposes.
34 *
35 * @author Christian Kohlschütter
36 * @see StreamClient
37 */
38 public final class StreamServer {
39 private StreamServer() {
40 throw new IllegalStateException("No instances");
41 }
42
43 /**
44 * {@link StreamServer} command-line tool.
45 *
46 * @param args Command-line arguments.
47 * @throws IOException on error.
48 * @throws AlreadyBoundException if there was already a server running.
49 */
50 public static void main(String[] args) throws IOException, AlreadyBoundException {
51 AFUNIXNaming naming = AFUNIXNaming.getInstance();
52 System.out.println("Socket directory: " + naming.getSocketFactory().getSocketDir());
53
54 try (StreamServiceImpl service = new StreamServiceImpl(naming.getSocketFactory())) {
55 naming.exportAndBind("streamService", service);
56
57 System.out.println("StreamServer ready; user.name=" + System.getProperty("user.name"));
58 }
59 }
60 }