Java SSLSocket的使用

绝地灬酷狼 2022-08-05 14:17 165阅读 0赞

# 1. 什么是SSLSocket #

JDK文档指出，SSLSocket扩展Socket并提供使用SSL或TLS协议的安全套接字。

这种套接字是正常的流套接字，但是它们在基础网络传输协议(如TCP)上添加了安全保护层。

具体安全方面的讨论见下一篇。本篇重点关注SSLSocket及相关几个类的使用。

# 2. SSLSocket和相关类 #

SSLSocket来自jsse(Java Secure Socket Extension)。

![b5e097a5-3ec4-358d-972d-18cc928daafd.jpg][]

(1)SSLContext: 此类的实例表示安全套接字协议的实现， 它是SSLSocketFactory、SSLServerSocketFactory和SSLEngine的工厂。

(2)SSLSocket: 扩展自Socket

(3)SSLServerSocket: 扩展自ServerSocket

(4)SSLSocketFactory: 抽象类，扩展自SocketFactory, SSLSocket的工厂

(5)SSLServerSocketFactory: 抽象类，扩展自ServerSocketFactory, SSLServerSocket的工厂

(6)KeyStore: 表示密钥和证书的存储设施

(7)KeyManager: 接口，JSSE密钥管理器

(8)TrustManager: 接口，信任管理器(?翻译得很拗口)

(9)X590TrustedManager: TrustManager的子接口，管理X509证书，验证远程安全套接字

# 3. SSLContext的使用 #

Java代码 [ ![复制代码][icon_copy.gif]][_icon_copy.gif]  ![收藏代码][icon_star.png]![spinner.gif][]

1.  public static  void main(String\[\] args) throws Exception \{
2.  X509TrustManager x509m = new X509TrustManager() \{
3.  
4.  @Override
5.  public X509Certificate\[\] getAcceptedIssuers() \{
6.  return null;
7.  \}
8.  
9.  @Override
10. public void checkServerTrusted(X509Certificate\[\] chain,
11. String authType) throws CertificateException \{
12. \}
13. 
14. @Override
15. public void checkClientTrusted(X509Certificate\[\] chain,
16. String authType) throws CertificateException \{
17. \}
18. \};
19. // 获取一个SSLContext实例
20. SSLContext s = SSLContext.getInstance("SSL");
21. // 初始化SSLContext实例
22. s.init(null, new TrustManager\[\] \{ x509m \},
23. new java.security.SecureRandom());
24. // 打印这个SSLContext实例使用的协议
25. System.out.println("缺省安全套接字使用的协议: " \+ s.getProtocol());
26. // 获取SSLContext实例相关的SSLEngine
27. SSLEngine e = s.createSSLEngine();
28. System.out
29. .println("支持的协议: " \+ Arrays.asList(e.getSupportedProtocols()));
30. System.out.println("启用的协议: " \+ Arrays.asList(e.getEnabledProtocols()));
31. System.out.println("支持的加密套件: "
32. \+ Arrays.asList(e.getSupportedCipherSuites()));
33. System.out.println("启用的加密套件: "
34. \+ Arrays.asList(e.getEnabledCipherSuites()));
35. \}

public static void main(String[] args) throws Exception {
    		X509TrustManager x509m = new X509TrustManager() {
    
    			@Override
    			public X509Certificate[] getAcceptedIssuers() {
    				return null;
    			}
    
    			@Override
    			public void checkServerTrusted(X509Certificate[] chain,
    					String authType) throws CertificateException {
    			}
    
    			@Override
    			public void checkClientTrusted(X509Certificate[] chain,
    					String authType) throws CertificateException {
    			}
    		};
    		// 获取一个SSLContext实例
    		SSLContext s = SSLContext.getInstance("SSL");
    		// 初始化SSLContext实例
    		s.init(null, new TrustManager[] { x509m },
    				new java.security.SecureRandom());
    		// 打印这个SSLContext实例使用的协议
    		System.out.println("缺省安全套接字使用的协议: " + s.getProtocol());
    		// 获取SSLContext实例相关的SSLEngine
    		SSLEngine e = s.createSSLEngine();
    		System.out
    				.println("支持的协议: " + Arrays.asList(e.getSupportedProtocols()));
    		System.out.println("启用的协议: " + Arrays.asList(e.getEnabledProtocols()));
    		System.out.println("支持的加密套件: "
    				+ Arrays.asList(e.getSupportedCipherSuites()));
    		System.out.println("启用的加密套件: "
    				+ Arrays.asList(e.getEnabledCipherSuites()));
    	}

运行结果如下:

![48852bc4-389c-3c9d-9053-77c39d2e0fef.png][]

SSLContext.getProtocol(): 返回当前SSLContext对象的协议名称

SSLContext.init(): 初始化当前SSLContext对象。 三个参数均可以为null。 详见JDK文档。

SSLEngine.getSupportedProtocols()等几个方法可以返回些 Engine上支持/已启用的协议、支持/已启用的加密套件

# 4. SSLSocket和SSLServerSocket的使用 #

这两个类的用法跟Socket/ServerSocket的用法比较类似。看下面的例子(主要为了验证SSLSocket的用法 ，I/O和多线程处理比较随意)

## 4.1 SSLServerSocket ##

(1)新建一个SSLServerSocket，并开始监听来自客户端的连接

Java代码 [ ![复制代码][icon_copy.gif]][_icon_copy.gif]  ![收藏代码][icon_star.png]![spinner.gif][]

1.  // 抛出异常
2.  // javax.net.ssl.SSLException: No available certificate or key corresponds
3.  // to the SSL cipher suites which are enabled.
4.  public static  void notOk() throws IOException \{
5.  SSLServerSocketFactory factory = (SSLServerSocketFactory) SSLServerSocketFactory
6.  .getDefault();
7.  SSLServerSocket server = (SSLServerSocket) factory
8.  .createServerSocket(10000);
9.  System.out.println("ok");
10. server.accept();
11. \}

// 抛出异常
    	// javax.net.ssl.SSLException: No available certificate or key corresponds
    	// to the SSL cipher suites which are enabled.
    	public static void notOk() throws IOException {
    		SSLServerSocketFactory factory = (SSLServerSocketFactory) SSLServerSocketFactory
    				.getDefault();
    		SSLServerSocket server = (SSLServerSocket) factory
    				.createServerSocket(10000);
    		System.out.println("ok");
    		server.accept();
    	}

server.accept()处抛出异常， 提示缺少证书。与ServerSocket不同， SSLServerSocket需要证书来进行安全验证。

使用keytool工具生成一个证书。 步骤如下， 得到一个名为cmkey的证书文件

![a567e3e3-d970-32ef-9592-a9901fc0da2d.png][]

(2)重新完善上面的代码。 主要增加两个功能： 使用名为cmkey的证书初始化SSLContext, echo客户端的消息。 代码如下

Java代码 [ ![复制代码][icon_copy.gif]][_icon_copy.gif]  ![收藏代码][icon_star.png]![spinner.gif][]

1.  // 启动一个ssl server socket
2.  // 配置了证书, 所以不会抛出异常
3.  public static  void sslSocketServer() throws Exception \{
4.  
5.  // key store相关信息
6.  String keyName = "cmkey";
7.  char\[\] keyStorePwd = "123456".toCharArray();
8.  char\[\] keyPwd = "123456".toCharArray();
9.  KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
10. 
11. // 装载当前目录下的key store. 可用jdk中的keytool工具生成keystore
12. InputStream in = null;
13. keyStore.load(in = Test2.class.getClassLoader().getResourceAsStream(
14. keyName), keyPwd);
15. in.close();
16. 
17. // 初始化key manager factory
18. KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory
19. .getDefaultAlgorithm());
20. kmf.init(keyStore, keyPwd);
21. 
22. // 初始化ssl context
23. SSLContext context = SSLContext.getInstance("SSL");
24. context.init(kmf.getKeyManagers(),
25. new TrustManager\[\] \{ new MyX509TrustManager() \},
26. new SecureRandom());
27. 
28. // 监听和接收客户端连接
29. SSLServerSocketFactory factory = context.getServerSocketFactory();
30. SSLServerSocket server = (SSLServerSocket) factory
31. .createServerSocket(10002);
32. System.out.println("ok");
33. Socket client = server.accept();
34. System.out.println(client.getRemoteSocketAddress());
35. 
36. // 向客户端发送接收到的字节序列
37. OutputStream output = client.getOutputStream();
38. 
39. // 当一个普通 socket 连接上来, 这里会抛出异常
40. // Exception in thread "main" javax.net.ssl.SSLException: Unrecognized
41. // SSL message, plaintext connection?
42. InputStream input = client.getInputStream();
43. byte\[\] buf = new  byte\[1024\];
44. int len = input.read(buf);
45. System.out.println("received: " \+  new String(buf, 0, len));
46. output.write(buf, 0, len);
47. output.flush();
48. output.close();
49. input.close();
50. 
51. // 关闭socket连接
52. client.close();
53. server.close();
54. \}

// 启动一个ssl server socket
    	// 配置了证书, 所以不会抛出异常
    	public static void sslSocketServer() throws Exception {
    
    		// key store相关信息
    		String keyName = "cmkey";
    		char[] keyStorePwd = "123456".toCharArray();
    		char[] keyPwd = "123456".toCharArray();
    		KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
    
    		// 装载当前目录下的key store. 可用jdk中的keytool工具生成keystore
    		InputStream in = null;
    		keyStore.load(in = Test2.class.getClassLoader().getResourceAsStream(
    				keyName), keyPwd);
    		in.close();
    
    		// 初始化key manager factory
    		KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory
    				.getDefaultAlgorithm());
    		kmf.init(keyStore, keyPwd);
    
    		// 初始化ssl context
    		SSLContext context = SSLContext.getInstance("SSL");
    		context.init(kmf.getKeyManagers(),
    				new TrustManager[] { new MyX509TrustManager() },
    				new SecureRandom());
    
    		// 监听和接收客户端连接
    		SSLServerSocketFactory factory = context.getServerSocketFactory();
    		SSLServerSocket server = (SSLServerSocket) factory
    				.createServerSocket(10002);
    		System.out.println("ok");
    		Socket client = server.accept();
    		System.out.println(client.getRemoteSocketAddress());
    
    		// 向客户端发送接收到的字节序列
    		OutputStream output = client.getOutputStream();
    
    		// 当一个普通 socket 连接上来, 这里会抛出异常
    		// Exception in thread "main" javax.net.ssl.SSLException: Unrecognized
    		// SSL message, plaintext connection?
    		InputStream input = client.getInputStream();
    		byte[] buf = new byte[1024];
    		int len = input.read(buf);
    		System.out.println("received: " + new String(buf, 0, len));
    		output.write(buf, 0, len);
    		output.flush();
    		output.close();
    		input.close();
    
    		// 关闭socket连接
    		client.close();
    		server.close();
    	}

## 4.2 SSLSocket ##

(1)我们先使用一个普通的Socket尝试连接服务器端

Java代码 [ ![复制代码][icon_copy.gif]][_icon_copy.gif]  ![收藏代码][icon_star.png]![spinner.gif][]

1.  // 通过socket连接服务器
2.  public static  void socket() throws UnknownHostException, IOException \{
3.  Socket s = new Socket("localhost", 10002);
4.  System.out.println(s);
5.  System.out.println("ok");
6.  
7.  OutputStream output = s.getOutputStream();
8.  InputStream input = s.getInputStream();
9.  
10. output.write("alert".getBytes());
11. System.out.println("sent: alert");
12. output.flush();
13. 
14. byte\[\] buf = new  byte\[1024\];
15. int len = input.read(buf);
16. System.out.println("received:" \+  new String(buf, 0, len));
17. \}

// 通过socket连接服务器
    	public static void socket() throws UnknownHostException, IOException {
    		Socket s = new Socket("localhost", 10002);
    		System.out.println(s);
    		System.out.println("ok");
    
    		OutputStream output = s.getOutputStream();
    		InputStream input = s.getInputStream();
    
    		output.write("alert".getBytes());
    		System.out.println("sent: alert");
    		output.flush();
    
    		byte[] buf = new byte[1024];
    		int len = input.read(buf);
    		System.out.println("received:" + new String(buf, 0, len));
    	}

结果客户端和服务器端都出错。 客户端的错误是接收到乱码。

![b6b4a97b-65a3-37f1-9aa8-8208f9e71170.png][]

服务器则抛出异常

javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?

(2)改成SSLSocket， 但是不使用证书。客户端抛出sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

Java代码 [ ![复制代码][icon_copy.gif]][_icon_copy.gif]  ![收藏代码][icon_star.png]![spinner.gif][]

1.  // 不使用证书, 通过ssl socket连接服务器
2.  // 抛出异常, 提示找不到证书
3.  public static  void sslSocket() throws UnknownHostException, IOException \{
4.  SSLSocketFactory factory = (SSLSocketFactory) SSLSocketFactory
5.  .getDefault();
6.  SSLSocket s = (SSLSocket) factory.createSocket("localhost", 10002);
7.  System.out.println("ok");
8.  
9.  OutputStream output = s.getOutputStream();
10. InputStream input = s.getInputStream();
11. 
12. output.write("alert".getBytes());
13. System.out.println("sent: alert");
14. output.flush();
15. 
16. byte\[\] buf = new  byte\[1024\];
17. int len = input.read(buf);
18. System.out.println("received:" \+  new String(buf, 0, len));
19. \}

// 不使用证书, 通过ssl socket连接服务器
    	// 抛出异常, 提示找不到证书
    	public static void sslSocket() throws UnknownHostException, IOException {
    		SSLSocketFactory factory = (SSLSocketFactory) SSLSocketFactory
    				.getDefault();
    		SSLSocket s = (SSLSocket) factory.createSocket("localhost", 10002);
    		System.out.println("ok");
    
    		OutputStream output = s.getOutputStream();
    		InputStream input = s.getInputStream();
    
    		output.write("alert".getBytes());
    		System.out.println("sent: alert");
    		output.flush();
    
    		byte[] buf = new byte[1024];
    		int len = input.read(buf);
    		System.out.println("received:" + new String(buf, 0, len));
    	}

程序客户在不持有证书的情况下直接进行连接，服务器端会产生运行时异常javax.net.ssl.SSLHandshakeException: Received fatal alert: certificate\_unknown，不允许进行连接。 我们可以指定像下面这样执行客户端，服务器端可以成功echo客户端的发出的字符串"alert"

java \-Djavax.net.ssl.trustStore=cmkey Client

这里的cmkey即前面生成的证书文件。

(3)改成SSLSocket， 对SSLContext进行如下初始化。

Java代码 [ ![复制代码][icon_copy.gif]][_icon_copy.gif]  ![收藏代码][icon_star.png]![spinner.gif][]

1.  public static  void sslSocket2() throws Exception \{
2.  SSLContext context = SSLContext.getInstance("SSL");
3.  // 初始化
4.  context.init(null,
5.  new TrustManager\[\] \{ new Test2.MyX509TrustManager() \},
6.  new SecureRandom());
7.  SSLSocketFactory factory = context.getSocketFactory();
8.  SSLSocket s = (SSLSocket) factory.createSocket("localhost", 10002);
9.  System.out.println("ok");
10. 
11. OutputStream output = s.getOutputStream();
12. InputStream input = s.getInputStream();
13. 
14. output.write("alert".getBytes());
15. System.out.println("sent: alert");
16. output.flush();
17. 
18. byte\[\] buf = new  byte\[1024\];
19. int len = input.read(buf);
20. System.out.println("received:" \+  new String(buf, 0, len));
21. \}

public static void sslSocket2() throws Exception {
    		SSLContext context = SSLContext.getInstance("SSL");
                    // 初始化
    		context.init(null,
    				new TrustManager[] { new Test2.MyX509TrustManager() },
    				new SecureRandom());
    		SSLSocketFactory factory = context.getSocketFactory();
    		SSLSocket s = (SSLSocket) factory.createSocket("localhost", 10002);
    		System.out.println("ok");
    
    		OutputStream output = s.getOutputStream();
    		InputStream input = s.getInputStream();
    
    		output.write("alert".getBytes());
    		System.out.println("sent: alert");
    		output.flush();
    
    		byte[] buf = new byte[1024];
    		int len = input.read(buf);
    		System.out.println("received:" + new String(buf, 0, len));
    	}

服务器端可以成功echo客户端的发出的字符串"alert"。 完整代码见附件。

[b5e097a5-3ec4-358d-972d-18cc928daafd.jpg]: /images/20220805/90c21d3b56354d78aba2455289f04971.png
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