Ello伙伴们！我正在创建一个AES加密的聊天程序，但遇到了一个问题;每当一条消息超过47个字符时，它会显示“javax.crypto.IllegalBlockSizeException：当使用填充密码解密时，输入长度必须是16的倍数”。我理解错误消息，但我似乎无法弄清楚如何解决它。这是我的完整代码： ChatClient.java 包Chat.Application;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.text.*;
import java.security.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.*;
import javax.crypto.spec.SecretKeySpec;
import sun.misc.*;
import java.net.InetAddress;
/*
* Known Bugs:
* Message size is limited to 47 characters
*/
public class ChatClient {
BufferedReader in;
PrintWriter out;
JFrame frame = new JFrame("ELECTRON Chatroom");
JTextField textField = new JTextField(32);
JTextArea messageArea = new JTextArea(8, 40);
byte[] keyValue = new byte[]{'5', '7', '3', '4', '5', '6', '3', '4', '9', '8', '5', '6', 'l', '9', '3', '4'};
final String ALGO = "AES";
String name;
String myName;
InetAddress ip = null;
String errorType;
/*
* Constructs the client by laying out the GUI and registering a listener
* with the textfield so that pressing Return in the listener sends the
* textfield contents to the server. Note however that the textfield is
* initially NOT editable, and only becomes editable AFTER the client
* receives the NAMEACCEPTED message from the server.
*/
public class JTextFieldLimit extends PlainDocument {
private int limit;
// optional uppercase conversion
private boolean toUppercase = false;
JTextFieldLimit(int limit) {
super();
this.limit = limit;
}
JTextFieldLimit(int limit, boolean upper) {
super();
this.limit = limit;
toUppercase = upper;
}
public void insertString
(int offset, String str, AttributeSet attr)
throws BadLocationException {
if (str == null) return;
if ((getLength() + str.length()) <= limit) {
if (toUppercase) str = str.toUpperCase();
super.insertString(offset, str, attr);
}
}
}
public ChatClient() {
// Layout GUI
textField.setEditable(false);
messageArea.setEditable(false);
messageArea.setWrapStyleWord(true);
messageArea.setLineWrap(true);
frame.getContentPane().add(textField, "North");
frame.getContentPane().add(new JScrollPane(messageArea), "Center");
frame.pack();
// Add Listeners
textField.addActionListener(new ActionListener() {
/**
* Responds to pressing the enter key in the textfield by sending
* the contents of the text field to the server. Then clear the text
* area in preparation for the next message.
*/
@Override
public void actionPerformed(ActionEvent e) {
try {
if ((textField.getText()).startsWith("/")) {
if ("Electron".equals(myName)) {
String command = (textField.getText());
out.println(command);
textField.setText("");
}
} else {
//ENCRYPTION
String encrypt = textField.getText();
Key key = generateKey();
Cipher c = Cipher.getInstance(ALGO);
c.init(Cipher.ENCRYPT_MODE, key);
byte[] encVal = c.doFinal(encrypt.getBytes());
String input = new BASE64Encoder().encode(encVal);
out.println(input);
textField.setText("");
}
} catch (Exception ex) {
Logger.getLogger(ChatClient.class.getName()).log(Level.SEVERE, null, ex);
}
}
});
}
/**
* Prompt for and return the address of the server.
*/
private String getServerAddress() {
return JOptionPane.showInputDialog(
frame,
"Enter IP Address of the Server:",
"ELECTRON Chatroom",
JOptionPane.QUESTION_MESSAGE);
}
/**
* Prompt for and return the desired screen name.
*/
private String getName() {
return JOptionPane.showInputDialog(
frame,
"Choose a screen name:",
"Screen name selection",
JOptionPane.PLAIN_MESSAGE);
}
/**
* Connects to the server then enters the processing loop.
*/
private void run() throws IOException {
// Make connection and initialize streams
String serverAddress = getServerAddress();
Socket socket = new Socket(serverAddress, 9001);
in = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(), true);
// Process all messages from server, according to the protocol.
while (true) {
String line = in.readLine();
if (line.startsWith("SUBMITNAME")) {
if (line.length() == 18) {
line = line.substring(11);
System.out.println(line);
switch (line) {
case "ERROR 1":
errorType = "[ERROR: Name cannot be blank]";
JOptionPane.showMessageDialog(frame, errorType);
System.exit(0);
break;
case "ERROR 2":
errorType = "[ERROR: Your names 'Admin'? Seems legit...]";
JOptionPane.showMessageDialog(frame, errorType);
System.exit(0);
break;
case "ERROR 3":
errorType = "[ERROR: You have been banned]";
JOptionPane.showMessageDialog(frame, errorType);
System.exit(0);
break;
}
} else if (line.length() == 10) {
out.println(getName());
}
} else if (line.startsWith("NAMEACCEPTED")) {
myName = line.substring(13);
if (myName == "Admin") {
errorType = "[ERROR: Your names 'Admin'? Seems legit...]";
JOptionPane.showMessageDialog(frame, errorType);
System.exit(0);
} else if (myName == "ADMIN") {
errorType = "[ERROR: Your names 'Admin'? Seems legit...]";
JOptionPane.showMessageDialog(frame, errorType);
System.exit(0);
} else if (myName == "admin") {
errorType = "[ERROR: Your names 'Admin'? Seems legit...]";
JOptionPane.showMessageDialog(frame, errorType);
System.exit(0);
}
JOptionPane.showMessageDialog(frame, "Welcome " + myName + " (" + ip + ")");
ip = InetAddress.getLocalHost();
textField.setEditable(true);
//Limits message length to 47 characters (Disabled for debugging purposes)
//textField.setDocument(new JTextFieldLimit(47));
out.println(ip);
} else if (line.startsWith("SERVERMESSAGE")) {
line = line.substring(14);
messageArea.append(line + "\n");
messageArea.setCaretPosition(messageArea.getDocument().getLength());
} else if (line.startsWith("SERVERCOMMAND")) {
line = line.substring(14);
if (line.startsWith("kick " + ip)) {
System.exit(0);
}
} else if (line.startsWith("FINGERPRINT")) {
ip = InetAddress.getLocalHost();
out.println(ip);
} else if (line.startsWith("NAME")) {
name = line.substring(5);
} else if (line.startsWith("MESSAGE")) {
try {
//DECRYPTION
System.out.println(line);
line = line.substring(8);
String encryptedData = line;
System.out.println(line.length());
Key key = generateKey();
Cipher c = Cipher.getInstance(ALGO);
c.init(Cipher.DECRYPT_MODE, key);
byte[] decordedValue = new BASE64Decoder().decodeBuffer(encryptedData);
byte[] decValue = c.doFinal(decordedValue);
String decryptedValue = new String(decValue);
messageArea.append(name + ": " + decryptedValue + "\n");
messageArea.setCaretPosition(messageArea.getDocument().getLength());
} catch (Exception ex) {
Logger.getLogger(ChatClient.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
private Key generateKey() throws Exception {
Key key = new SecretKeySpec(keyValue, ALGO);
return key;
}
/**
* Runs the client as an application with a closeable frame.
*/
public static void main(String[] args) throws Exception {
ChatClient client = new ChatClient();
client.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
client.frame.setVisible(true);
client.run();
}
}
ChatServer.java
package Chat.Application;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashSet;
/**
* A multi-threaded chat room server. When a client connects the server requests
* a screen name by sending the client the text "SUBMITNAME", and keeps
* requesting a name until a unique one is received. After a client submits a
* unique name, the server acknowledges with "NAMEACCEPTED". Then all messages
* from that client will be broadcast to all other clients that have submitted a
* unique screen name. The broadcast messages are prefixed with "MESSAGE ".
*
* Because this is just a teaching example to illustrate a simple chat server,
* there are a few features that have been left out. Two are very useful and
* belong in production code:
*
* 1. The protocol should be enhanced so that the client can send clean
* disconnect messages to the server.
*
* 2. The server should do some logging.
*/
public class ChatServer {
/**
* The port that the server listens on.
*/
private static final int PORT = 9001;
/**
* The set of all names of clients in the chat room. Maintained so that we
* can check that new clients are not registering name already in use.
*/
private static HashSet<String> names = new HashSet<>();
/**
* The set of all the print writers for all the clients. This set is kept so
* we can easily broadcast messages.
*/
private static HashSet<PrintWriter> writers = new HashSet<>();
/**
* The set of all the print writers for all the clients. This set is kept so
* we can easily broadcast messages.
*/
private static HashSet<String> bans = new HashSet<>();
private static String[] Names = new String[50];
private static String[] Fingerprints = new String[50];
static int array = 0;
static int index;
/**
* The application main method, which just listens on a port and spawns
* handler threads.
*/
public static void main(String[] args) throws Exception {
System.out.println("Chat Server Activated");
ServerSocket listener = new ServerSocket(PORT);
try {
while (true) {
new Handler(listener.accept()).start();
}
} finally {
listener.close();
}
}
/**
* A handler thread class. Handlers are spawned from the listening loop and
* are responsible for a dealing with a single client and broadcasting its
* messages.
*/
private static class Handler extends Thread {
private String name;
private String ban;
private Socket socket;
private BufferedReader in;
private PrintWriter out;
private Integer length;
private String fingerprint;
/**
* Constructs a handler thread, squirreling away the socket. All the
* interesting work is done in the run method.
*/
public Handler(Socket socket) {
this.socket = socket;
}
/**
* Services this thread's client by repeatedly requesting a screen name
* until a unique one has been submitted, then acknowledges the name and
* registers the output stream for the client in a global set, then
* repeatedly gets inputs and broadcasts them.
*/
@Override
public void run() {
try {
// Create character streams for the socket.
in = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
out = new PrintWriter(socket.getOutputStream(), true);
// Request a name from this client. Keep requesting until
// a name is submitted that is not already used. Note that
// checking for the existence of a name and adding the name
// must be done while locking the set of names.
while (true) {
out.println("SUBMITNAME");
name = in.readLine();
length = name.length();
if (length == 0) {
out.println("SUBMITNAME ERROR 1");
return;
}
if (name == "null") {
out.println("SUBMITNAME ERROR 1");
return;
}
if (name == "Admin") {
out.println("SUBMITNAME ERROR 2");
return;
}
if (name == "admin") {
out.println("SUBMITNAME ERROR 2");
return;
}
if (name == "ADMIN") {
out.println("SUBMITNAME ERROR 2");
return;
}
synchronized (bans) {
out.println("FINGERPRINT");
fingerprint = in.readLine();
if (bans.contains(fingerprint)) {
out.println("SUBMITNAME ERROR 3");
return;
}
}
synchronized (names) {
if (!names.contains(name)) {
names.add(name);
break;
}
}
}
// Now that a successful name has been chosen, add the
// socket's print writer to the set of all writers so
// this client can receive broadcast messages.
out.println("NAMEACCEPTED " + name);
Names[array] = name;
System.out.println(Names[array]);
Fingerprints[array] = in.readLine();
System.out.println(Fingerprints[array]);
array = array + 1;
//Announces that user is Online
for (PrintWriter writer : writers) {
writer.println("SERVERMESSAGE " + name + " is now Online");
}
System.out.println(Names);
writers.add(out);
// Accept messages from this client and broadcast them.
// Ignore other clients that cannot be broadcasted to.
while (true) {
String input = in.readLine();
System.out.println(input);
if (input == null) {
return;
}
for (PrintWriter writer : writers) {
if (input.startsWith("/")) {
if ("Electron".equals(name)) {
//Tracks the hostname and IP address of the user
if (input.startsWith("/track")) {
input = input.substring(7);
index = java.util.Arrays.asList(Names).indexOf(input);
out.println("SERVERMESSAGE " + input + ": " + Fingerprints[index]);
//Bans the user from returning until Server is deactivated
} else if (input.startsWith("/ban")) {
input = input.substring(5);
index = java.util.Arrays.asList(Names).indexOf(input);
synchronized (bans) {
bans.add(Fingerprints[index]);
}
out.println("SERVERMESSAGE " + input + "(" + Fingerprints[index] + ")" + " is now banned");
} else if (input.startsWith("/kick")) {
input = input.substring(6);
index = java.util.Arrays.asList(Names).indexOf(input);
out.println("SERVERCOMMAND kick " + Fingerprints[index]);
} else if (input.startsWith("/deactivate")) {
writer.println("SERVERMESSAGE The server is now Offline");
System.exit(0);
}
}
} else {
writer.println("NAME " + name);
writer.println("MESSAGE " + input);
}
}
}
} catch (IOException e) {
System.out.println(e);
} finally {
// This client is going down! Remove its name and its print
// writer from the sets, and close its socket.
for (PrintWriter writer : writers) {
writer.println("SERVERMESSAGE " + name + " is now Offline");
}
if (name != null) {
names.remove(name);
}
if (out != null) {
writers.remove(out);
}
try {
socket.close();
} catch (IOException e) {
}
}
}
}
}
我尝试改变我发送的文本量，添加更多填充，甚至尝试从1 - 1000的每个输入，以查看是否有模式（没有....）。我在互联网上进行过研究，但无济于事。
感谢帮助Noob程序员完成他的第二个程序（真的。）！祝你有愉快的一周！
答案 0 :(得分：2)
这是事实。 AES是一个块密码，这意味着它一次只加密16个字节。
这意味着您必须将消息填充为16的倍数，并多次调用它，每个块一次。为了获得良好的加密效果，您还需要添加IV，并将其应用于所有块。这可能很难自己实现，所以你应该让你的库来做。 javax.crypto库已经可以做到。
解决方案是选择另一种算法，如the Javadocs中所示（或查阅完整列表here）。
尝试使用algo：AES/CBC/PKCS5Padding