Jsch 深入浅出(一)
如果大家熟悉Linux的话，一定对ssh,sftp,scp等命令非常熟悉。ssh是一个安全协议，用来在不同系统或者服务器之间进行安全连接。ssh 在连接和传送的过程中会加密所有的数据。具体的解释，大家可以参考百度百科的文档。地址为：http://baike.baidu.com/view/16184.htm
但是SSH一般是基于客户端的或者Linux命令行的。比如客户端的工具:OpenSSH,putty,SSH Tectia；在linux上大家可以通过ssh username@host连接到所要想连接的主机。但是如果在J2EE中，如何实现SSH呢？进而可以实现SCP,SFTP的功能呢？下面介绍的JSCH就可以实现下边的功能。
JSCH是一个纯粹的用java实现SSH功能的java library. 官方地址为：http://www.jcraft.com/jsch/
GitHub 地址为:https://github.com/vngx/vngx-jsch
mvn 配置如下：
<dependency>
<groupId>com.jcraft</groupId>
<artifactId>jsch</artifactId>
<version>0.1.46</version>
</dependency>
下面简单介绍下JSCH的特点：
1.基于ＤＳＡ和ＲＳＡ加密。
2.可以实现４中认证机制。分别是：
- password
- publickey(DSA,RSA)
- keyboard-interactive
- gss-api-with-mic
3.生成public/private key pair.
4.执行bash script 等脚本
5.可以通过HTTP/SOCK5 proxy
6.支持常见SSH1协议和SSH2协议
我们日常用到的JSCH主要是基于是密码认证和private key 认证。
基于密码认证的比较简单。简单代码如下：
[java]
public class JschHandler {
private static final Logger log = LoggerFactory.getLogger(JschHandler.class);
public static final String SFTP_PROTOCAL = "sftp";
private String username;
private String host;
private int port;
private String identity;
private UserInfo userInfo;
private JSch jsch = null;
protected Session session = null;
private boolean firstInit = false;
private int authType = -1;
/**
* Private/public key authorization
* @param username user account
* @param host server host
* @param port ssh port
* @param identity the path of private key file.
* @see http://www.jcraft.com/jsch/
*/
public JschHandler(String username,String host,int port,String identity){
this.username = username;
this.host = host;
this.port = port;
this.identity = identity;
firstInit = false;
jsch = new JSch();
authType = 0 ;
}
/**
* Password authorization
* @param username
* @param host
* @param port
* @param userInfo User information for authorization
* @see com.jcraft.jsch.UserInfo
* @see http://www.jcraft.com/jsch/
*/
public JschHandler(String username,String host,int port,UserInfo userInfo){
this.username = username;
this.host = host;
this.port = port;
this.userInfo = userInfo;
firstInit = false;
jsch = new JSch();
authType = 1;
}
/**
*
* Initialize SSH session.
* When the parameters is not right, It will throw an JSchException.
* @throws MessageServicerException
* @see com.jcraft.jsch.JSch
*/
@SuppressWarnings("static-access")
protected void init() throws JSchException{
try {
validate();
log.info("JSCH identity:"+identity);
jsch.setLogger(new JschLogger());
jsch.setConfig("StrictHostKeyChecking", "no");
if(authType==0) jsch.addIdentity(identity);
session = jsch.getSession(username, host, port);
if(authType==1) session.setUserInfo(userInfo);
session.connect();
log.info("JSCH session connect success.");
} catch (JSchException e) {
log.error(e.getMessage());
throw e;
}
}
/**
* Validate parameters
* @throws JSchException
*/
private void validate() throws JSchException{
if(firstInit) return;
if(username==null||username.isEmpty()){
throw new JSchException("Parameter:username is empty.");
}
if(host==null||host.isEmpty()){
throw new JSchException("Parameter:host is empty.");
}else{
try {
InetAddress inet = InetAddress.getByName(host);
host = inet.getHostAddress();
log.info("JSCH connection address:"+host);
} catch (UnknownHostException e) {
throw new JSchException(e.getMessage(),e);
}
}
if(authType==0&&(identity==null||identity.isEmpty())){
throw new JSchException("Parameter:identity is empty.");
}
if(authType==1&&(userInfo==null)){
throw new JSchException("Parameter:userInfo is empty.");
}
firstInit = true;
}
/**
* release connections.
* @author
*/
protected void destory(){
if(session!=null) session.disconnect();
log.info("JSCH session destory");
}
private static class JschLogger implements com.jcraft.jsch.Logger{
@Override
public boolean isEnabled(int level) {
return true;
}
@Override
public void log(int level, String message) {
System.out.println(String.format("[JSCH –> %s]", message));
}
}
public void setUserInfo(UserInfo userInfo) {
this.userInfo = userInfo;
}
}
[/java]
Client
[java]
public static class MyUserInfo implements UserInfo, UIKeyboardInteractive {
public String getPassword() {
return null;
}
public boolean promptYesNo(String str) {
Object[] options = { "yes", "no" };
int foo = JOptionPane.showOptionDialog(null, str, "Warning",
JOptionPane.DEFAULT_OPTION, JOptionPane.WARNING_MESSAGE,
null, options, options[0]);
return foo == 0;
}
String passphrase;
JTextField passphraseField = (JTextField) new JPasswordField(20);
public String getPassphrase() {
return passphrase;
}
public boolean promptPassphrase(String message) {
Object[] ob = { passphraseField };
int result = JOptionPane.showConfirmDialog(null, ob, message,
JOptionPane.OK_CANCEL_OPTION);
if (result == JOptionPane.OK_OPTION) {
passphrase = passphraseField.getText();
return true;
} else {
return false;
}
}
public boolean promptPassword(String message) {
return true;
}
public void showMessage(String message) {
JOptionPane.showMessageDialog(null, message);
}
final GridBagConstraints gbc = new GridBagConstraints(0, 0, 1, 1, 1, 1,
GridBagConstraints.NORTHWEST, GridBagConstraints.NONE,
new Insets(0, 0, 0, 0), 0, 0);
private Container panel;
public String[] promptKeyboardInteractive(String destination,
String name, String instruction, String[] prompt, boolean[] echo) {
panel = new JPanel();
panel.setLayout(new GridBagLayout());
gbc.weightx = 1.0;
gbc.gridwidth = GridBagConstraints.REMAINDER;
gbc.gridx = 0;
panel.add(new JLabel(instruction), gbc);
gbc.gridy++;
gbc.gridwidth = GridBagConstraints.RELATIVE;
JTextField[] texts = new JTextField[prompt.length];
for (int i = 0; i < prompt.length; i++) {
gbc.fill = GridBagConstraints.NONE;
gbc.gridx = 0;
gbc.weightx = 1;
panel.add(new JLabel(prompt[i]), gbc);
gbc.gridx = 1;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weighty = 1;
if (echo[i]) {
texts[i] = new JTextField(20);
} else {
texts[i] = new JPasswordField(20);
}
panel.add(texts[i], gbc);
gbc.gridy++;
}
if (JOptionPane.showConfirmDialog(null, panel, destination + ": "
+ name, JOptionPane.OK_CANCEL_OPTION,
JOptionPane.QUESTION_MESSAGE) == JOptionPane.OK_OPTION) {
String[] response = new String[prompt.length];
for (int i = 0; i < prompt.length; i++) {
response[i] = texts[i].getText();
}
return response;
} else {
return null; // cancel
}
}
}
[/java]
测试类
[java]
public void testSftp() throws JSchException{
UserInfo userInfo = new MyUserInfo();
JftpHandler jhandler = new JftpHandler("username","hostname",22,userInfo);
try {
jhandler.init();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
String pwd = null;
try {
pwd = jhandler.pwd();
} catch (SftpException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(pwd);
// jhandler.destory();
}
[/java]
基于private key 认证的有点费时。关于如何配置private/public key认证，大家通过google来配置。简单流程如下：
1.在linux 下执行ssh-keygen -t dsa /ssh-keygen -t rsa.这样就会成一对对应的public key 和private key.比如id_dsa_1024,id_dsa_1024.pub.
2. 把public key(id_dsa_1024.pub)复制到想要连接的服务器上，放到对应用户的.ssh目录下。
3.
cd ~/.ssh
#将Client的公钥放入Server的信任列表
cat id_dsa_1024.pub >> authorized_keys
#更新权限，很重要
chmod 0600 *从此以后Client SSH登录Server就不要手工输入密码了
配置完成以后，重新登录一下，就可以发现不用输入密码就可以实现远程登录了。
由于现在基于ＳＳＨ协议的算法很多，加密和解密的算法也不一样。目前Jsch只支持OpenSSH和SSH 1生成的private/public key.
所以当你们发现不能通过private/public key认证的时候，不是jsch的问题，而是不能识别的问题。
简单代码如下：
[java]
@Test
public void testSftp() throws JSchException{
JftpHandler jhandler = new JftpHandler("username","hostname",22,"C:\\data\\id_dsa_2048_a");
try {
jhandler.init();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
String pwd = null;
try {
pwd = jhandler.pwd();
} catch (SftpException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(pwd);
// jhandler.destory();
}
[/java]
上面只是对JSCH的简单介绍，希望对大家有所用户。。。。