Java SSH connect with key using JSch - Auth Failed

Question

I'm trying to connect to localhost using SSH with key. But I still get an error:

Auth Failed

Here is the method implementation:

public void downloadUsingPublicKey(String username, String host)
{
     String privateKey = "~/.ssh/id_rsa";
     
     JSch jsch = new JSch(); 
     Session session = null; 
     Channel channel = null; 
     ChannelSftp channelSftp = null; 
     try 
     { 
         jsch.addIdentity(privateKey); 
         System.out.println("Private Key Added."); 
         
         session = jsch.getSession(username, host); 
         System.out.println("session created."); 
         
         java.util.Properties config = new java.util.Properties(); 
         config.put("StrictHostKeyChecking", "no"); 
         
         session.setConfig(config); 
         session.connect(); 
         
         channel = session.openChannel("sftp"); 
         channel.connect(); System.out.println("shell channel connected...."); 
         
         channelSftp = (ChannelSftp)channel; 
         channelSftp.cd(Config.dir); 
         
         System.out.println("Changed the directory..."); 
     } catch (JSchException e) 
     { 
         // TODO Auto-generated catch block 
         e.printStackTrace(); 
     } catch (SftpException e) 
     { 
         // TODO Auto-generated catch block 
         e.printStackTrace(); 
     }finally
     { 
         if(channelSftp!=null)
         { 
             channelSftp.disconnect(); 
             channelSftp.exit(); 
         } 
         if(channel!=null) channel.disconnect(); 
         if(session!=null) session.disconnect(); 
     } 
}

I've created my public/private key pair using Linux terminal, as follows:

ssh-keygen -t rsa -b 4096 -C "[email protected]"

I didn't put any phrase.

Next step:

ssh-add ~/.ssh/id_rsa

And finally

cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

Then when I run my program I get error:

com.jcraft.jsch.JSchException: Auth fail
    at com.jcraft.jsch.Session.connect(Session.java:512)
    at com.jcraft.jsch.Session.connect(Session.java:183)
    at pl.eroj.filedownloader.Downloader.downloadUsingPublicKey(Downloader.java:73)
    at pl.eroj.filedownloader.Downloader.main(Downloader.java:107)

Any ideas? My key is of OpenSSH type starting with line "-----BEGIN RSA PRIVATE KEY-----"

You need to add the client's (new) public key to the authorized_keys file ON THE SERVER — dave_thompson_085
– dave_thompson_085, Commented Jul 29, 2015 at 18:46
So if i get it correctly I need to copy the key from id_rsa.pub and paste it in the .ssh/authorized_keys on the server ? — Emil Rojewski
– Emil Rojewski, Commented Jul 29, 2015 at 21:17
copy&paste can work, as long as the result is one long line exactly as it is in the source file id_rsa.pub; depending on the terminals/UIs you use they might turn displayed line wraps into line breaks. A simple robust way is to scp .ssh/id_rsa.pub user@host:. then ssh to the server and cat the copy onto authorized_keys and check/fix the permissions (must be inaccessible to other users). Or if you don't yet have anything (needed) in server authorized_keys just chmod the local file and directly scp -p .ssh/id_rsa.pub user@host:.ssh/authorized_keys. — dave_thompson_085
– dave_thompson_085, Commented Jul 30, 2015 at 21:15
Yeah i used this method with scp and it all worked out :) so the problem was solved. Thanks for advice — Emil Rojewski
– Emil Rojewski, Commented Jul 31, 2015 at 0:17
Here is the blog article explaining how to connect to remote host by using public key authentication from java: svlada.com/ssh-public-key-authentication — svlada
– svlada, Commented Nov 23, 2015 at 20:25

Vladi · Accepted Answer · 2021-08-25 10:07:13Z

This how I connected localy using with Path of private Key when
privateKeyPath ="C:\Keys\private_key.ppk"

    public static OutputStream ConnectionUsingKey(String user, String hostName, String privateKeyPath)
        throws JSchException, IOException {
    JSch jsch = new JSch();
    Session session = null;
    try {

        jsch.addIdentity(privateKeyPath);
        session = jsch.getSession(user, hostName, 22);
        session.setConfig("PreferredAuthentications", "publickey");
        session.setConfig("StrictHostKeyChecking", "no");
        session.connect();
        if (session.isConnected() == true) {
            System.out.println("Connection to Session server is successfully");
        }
        channel = session.openChannel("shell");
        channel.setInputStream(System.in);
        channel.setOutputStream(System.out);
        channel.connect(30 * 1000);
        return channel.getOutputStream();

    } catch (JSchException e) {
        throw new RuntimeException("Failed to create Jsch Session object.", e);
    }
}

codester · Accepted Answer · 2021-12-23 20:07:03Z

0

Thank you @Vladi. In my case I needed to connect to a server that used both private key and a password. Hence I had to set the Config like this

        session.setConfig("PreferredAuthentications", "publickey,password");
        session.setPassword("some_password");

answered Dec 23, 2021 at 20:07

codester

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