SSL介绍与Java实例

有关SSL的原理和介绍在网上已经有不少，对于Java下使用keytool生成证书，配置SSL通信的教程也非常多。但如果我们不能够亲自动手做一个SSL Sever和SSL Client，可能就永远也不能深入地理解Java环境下，SSL的通信是如何实现的。对SSL中的各种概念的认识也可能会仅限于可以使用的程度。本文通过构造一个简单的SSL Server和SSL Client来讲解Java环境下SSL的通信原理。 


首先我们先回顾一下常规的Java Socket编程。在Java下写一个Socket服务器和客户端的例子还是比较简单的。以下是服务端的代码： 

package org.bluedash.tryssl;    import java.io.BufferedReader;  import java.io.IOException;  import java.io.InputStreamReader;  import java.io.PrintWriter;  import java.net.ServerSocket;  import java.net.Socket;    public class Server extends Thread {      private Socket socket;        public Server(Socket socket) {          this.socket = socket;      }        public void run() {          try {              BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));              PrintWriter writer = new PrintWriter(socket.getOutputStream());                String data = reader.readLine();              writer.println(data);              writer.close();              socket.close();          } catch (IOException e) {            }      }            public static void main(String[] args) throws Exception {          while (true) {              new Server((new ServerSocket(8080)).accept()).start();          }      }  }  

服务端很简单：侦听8080端口，并把客户端发来的字符串返回去。

下面是客户端的代码： 

package org.bluedash.tryssl;    import java.io.BufferedReader;  import java.io.InputStreamReader;  import java.io.PrintWriter;  import java.net.Socket;    public class Client {        public static void main(String[] args) throws Exception {            Socket s = new Socket("localhost", 8080);            PrintWriter writer = new PrintWriter(s.getOutputStream());          BufferedReader reader = new BufferedReader(new InputStreamReader(s.getInputStream()));          writer.println("hello");          writer.flush();          System.out.println(reader.readLine());          s.close();      }    }  

客户端也非常简单：向服务端发起请求，发送一个"hello"字串，然后获得服务端的返回。把服务端运行起来后，执行客户端，我们将得到"hello"的返回。 

就是这样一套简单的网络通信的代码，我们来把它改造成使用SSL通信。在SSL通信协议中，我们都知道首先服务端必须有一个数字证书，当客户端连接到服务端时，会得到这个证书，然后客户端会判断这个证书是否是可信的，如果是，则交换信道加密密钥，进行通信。如果不信任这个证书，则连接失败。

改造后的服务端代码：

package org.bluedash.tryssl;import java.io.BufferedReader;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.ServerSocket;import java.net.Socket;import java.security.KeyStore;import javax.net.ServerSocketFactory;import javax.net.ssl.KeyManagerFactory;import javax.net.ssl.SSLContext;import javax.net.ssl.SSLServerSocket;public class SSLServer extends Thread {private Socket socket;public SSLServer(Socket socket) {this.socket = socket;}public void run() {try {BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));PrintWriter writer = new PrintWriter(socket.getOutputStream());String data = reader.readLine();writer.println(data);writer.close();socket.close();} catch (IOException e) {}}private static String SERVER_KEY_STORE = "/Users/liweinan/projs/ssl/src/main/resources/META-INF/server_ks";private static String SERVER_KEY_STORE_PASSWORD = "123123";public static void main(String[] args) throws Exception {System.setProperty("javax.net.ssl.trustStore", SERVER_KEY_STORE);SSLContext context = SSLContext.getInstance("TLS");KeyStore ks = KeyStore.getInstance("jceks");ks.load(new FileInputStream(SERVER_KEY_STORE), null);KeyManagerFactory kf = KeyManagerFactory.getInstance("SunX509");kf.init(ks, SERVER_KEY_STORE_PASSWORD.toCharArray());context.init(kf.getKeyManagers(), null, null);ServerSocketFactory factory = context.getServerSocketFactory();ServerSocket _socket = factory.createServerSocket(8443);((SSLServerSocket) _socket).setNeedClientAuth(false);while (true) {new SSLServer(_socket.accept()).start();}}}

改造后的客户端代码（单向认证，客户端信任服务端）：

package org.bluedash.tryssl;import java.io.BufferedReader;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.Socket;import javax.net.SocketFactory;import javax.net.ssl.SSLSocketFactory;public class SSLClient {private static String CLIENT_KEY_STORE = "/Users/liweinan/projs/ssl/src/main/resources/META-INF/client_ks";public static void main(String[] args) throws Exception {// Set the key store to use for validating the server cert.System.setProperty("javax.net.ssl.trustStore", CLIENT_KEY_STORE);System.setProperty("javax.net.debug", "ssl,handshake");SSLClient client = new SSLClient();Socket s = client.clientWithoutCert();PrintWriter writer = new PrintWriter(s.getOutputStream());BufferedReader reader = new BufferedReader(new InputStreamReader(s.getInputStream()));writer.println("hello");writer.flush();System.out.println(reader.readLine());s.close();}private Socket clientWithoutCert() throws Exception {SocketFactory sf = SSLSocketFactory.getDefault();Socket s = sf.createSocket("localhost", 8443);return s;}}

双向认证的服务端代码：

很简单，只要在单向认证的服务端代码中改动这一句即可

  ((SSLServerSocket) _socket).setNeedClientAuth(true);  

双向认证的客户端代码：

package org.bluedash.tryssl;import java.io.BufferedReader;import java.io.FileInputStream;import java.io.InputStreamReader;import java.io.PrintWriter;import java.net.Socket;import java.security.KeyStore;import javax.net.SocketFactory;import javax.net.ssl.KeyManagerFactory;import javax.net.ssl.SSLContext;import javax.net.ssl.SSLSocketFactory;public class SSLClient {private static String CLIENT_KEY_STORE = "/Users/liweinan/projs/ssl/src/main/resources/META-INF/client_ks";private static String CLIENT_KEY_STORE_PASSWORD = "456456";public static void main(String[] args) throws Exception {// Set the key store to use for validating the server cert.System.setProperty("javax.net.ssl.trustStore", CLIENT_KEY_STORE);System.setProperty("javax.net.debug", "ssl,handshake");SSLClient client = new SSLClient();Socket s = client.clientWithCert();PrintWriter writer = new PrintWriter(s.getOutputStream());BufferedReader reader = new BufferedReader(new InputStreamReader(s.getInputStream()));writer.println("hello");writer.flush();System.out.println(reader.readLine());s.close();}private Socket clientWithCert() throws Exception {SSLContext context = SSLContext.getInstance("TLS");KeyStore ks = KeyStore.getInstance("jceks");ks.load(new FileInputStream(CLIENT_KEY_STORE), null);KeyManagerFactory kf = KeyManagerFactory.getInstance("SunX509");kf.init(ks, CLIENT_KEY_STORE_PASSWORD.toCharArray());context.init(kf.getKeyManagers(), null, null);SocketFactory factory = context.getSocketFactory();Socket s = factory.createSocket("localhost", 8443);return s;}}

本文转自：

http://www.iteye.com/topic/1125183