Haritz Haritz - 9 months ago 61
Java Question

Skipping Kerberos authentication prompts with JSch

I am using the

Connect()
method in the
Ssh
Java class below in order to connect to a server using SSH (JSch) and running a command in the server.

The problem is that when running
Connect()
the server prompts the next messages:

Kerberos username [********]:

Kerberos password for ********:


And in order to continue running I need to manually press the Enter key twice, one for the user name and one for the password. I have tried to add the next code:

// Press ENTER
Robot r = new Robot();
r.keyPress(KeyEvent.VK_ENTER);
r.keyRelease(KeyEvent.VK_ENTER);


But this code only works for the user name, I can not figure out how to automatically press ENTER when the server asks for the password. So far I have tried to put another code snippet as the one shown above below the

session.connect();


line.

package ConnectSSH;

import java.awt.Robot;
import java.awt.event.KeyEvent;
import java.io.*;

import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;
import com.jcraft.jsch.UserInfo;

public class Ssh{

private static final String user = "********";
private static final String host = "********";
private static final Integer port = 22;
private static final String pass = "********";

public void Connect() throws Exception{
JSch jsch = new JSch();
Session session = jsch.getSession(user, host, port);
UserInfo ui = new SUserInfo(pass, null);
session.setUserInfo(ui);
session.setPassword(pass);
//Press ENTER
Robot r = new Robot();
r.keyPress(KeyEvent.VK_ENTER);
r.keyRelease(KeyEvent.VK_ENTER);
session.connect();
ChannelExec channelExec = (ChannelExec)session.openChannel("exec");
InputStream in = channelExec.getInputStream();
channelExec.setCommand("RUN COMMAND");
channelExec.connect();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String linea = null;
int index = 0;
while ((linea = reader.readLine()) != null) {
System.out.println(++index + " : " + linea);
}
channelExec.disconnect();
session.disconnect();
}
}


And this is the
SUserInfo
class

package ConnectSSH;

import com.jcraft.jsch.UserInfo;

public class SUserInfo implements UserInfo {

private String password;
private String passPhrase;

public SUserInfo (String password, String passPhrase) {
this.password = password;
this.passPhrase = passPhrase;
}

public String getPassphrase() {
return passPhrase;
}

public String getPassword() {
return password;
}

public boolean promptPassphrase(String arg0) {
return true;
}

public boolean promptPassword(String arg0) {
return false;
}

public boolean promptYesNo(String arg0) {
return true;
}

public void showMessage(String arg0) {
System.out.println("SUserInfo.showMessage()");
}
}


And this is what the logger returns:

INFO: Connecting to ****** port 22
INFO: Connection established
INFO: Remote version string: SSH-2.0-Sun_SSH_1.1.2
INFO: Local version string: SSH-2.0-JSCH-0.1.52
INFO: CheckCiphers: aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc,3des-ctr,arcfour,arcfour128,arcfour256
INFO: aes256-ctr is not available.
INFO: aes192-ctr is not available.
INFO: aes256-cbc is not available.
INFO: aes192-cbc is not available.
INFO: CheckKexes: diffie-hellman-group14-sha1,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521
INFO: diffie-hellman-group14-sha1 is not available.
INFO: CheckSignatures: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
INFO: SSH_MSG_KEXINIT sent
INFO: SSH_MSG_KEXINIT received
INFO: kex: server: gss-group1-sha1-toWM5Slw5Ew8Mqkay+al2g==,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1
INFO: kex: server: ssh-rsa,ssh-dss
INFO: kex: server: aes128-ctr,aes128-cbc,arcfour,3des-cbc,blowfish-cbc,aes192-ctr,aes192-cbc,aes256-ctr,aes256-cbc
INFO: kex: server: aes128-ctr,aes128-cbc,arcfour,3des-cbc,blowfish-cbc,aes192-ctr,aes192-cbc,aes256-ctr,aes256-cbc
INFO: kex: server: hmac-md5,hmac-sha1,hmac-sha1-96,hmac-md5-96
INFO: kex: server: hmac-md5,hmac-sha1,hmac-sha1-96,hmac-md5-96
INFO: kex: server: none,zlib
INFO: kex: server: none,zlib
INFO: kex: server: ar-EG,ar-SA,bg-BG,ca-ES,cs-CZ,da-DK,de,de-AT,de-CH,de-DE,de-LU,el-CY,el-GR,en-AU,en-CA,en-GB,en-IE,en-MT,en-NZ,en-US,es,es-AR,es-BO,es-CL,es-CO,es-CR,es-EC,es-ES,es-GT,es-MX,es-NI,es-PA,es-PE,es-PY,es-SV,es-UY,es-VE,et-EE,fi-FI,fr,fr-BE,fr-CA,fr-CH,fr-FR,fr-LU,he-IL,hi-IN,hr-HR,hu-HU,is-IS,it,it-IT,ja-JP,kk-KZ,ko,ko-KR,lt-LT,lv-LV,mk-MK,mt-MT,nb-NO,nl-BE,nl-NL,nn-NO,pl,pl-PL,pt-BR,pt-PT,ro-RO,ru,ru-RU,sh-BA,sk-SK,sl-SI,sq-AL,sr-CS,sv,sv-SE,th-TH,tr-TR,uk-UA,zh,zh-CN,zh-HK,zh-TW,ar,ca,cz,da,el,et,fi,he,hu,ja,lt,lv,nl,no,no-NO,no-NY,nr,pt,sr-SP,sr-YU,th,tr,i-default
INFO: kex: server: ar-EG,ar-SA,bg-BG,ca-ES,cs-CZ,da-DK,de,de-AT,de-CH,de-DE,de-LU,el-CY,el-GR,en-AU,en-CA,en-GB,en-IE,en-MT,en-NZ,en-US,es,es-AR,es-BO,es-CL,es-CO,es-CR,es-EC,es-ES,es-GT,es-MX,es-NI,es-PA,es-PE,es-PY,es-SV,es-UY,es-VE,et-EE,fi-FI,fr,fr-BE,fr-CA,fr-CH,fr-FR,fr-LU,he-IL,hi-IN,hr-HR,hu-HU,is-IS,it,it-IT,ja-JP,kk-KZ,ko,ko-KR,lt-LT,lv-LV,mk-MK,mt-MT,nb-NO,nl-BE,nl-NL,nn-NO,pl,pl-PL,pt-BR,pt-PT,ro-RO,ru,ru-RU,sh-BA,sk-SK,sl-SI,sq-AL,sr-CS,sv,sv-SE,th-TH,tr-TR,uk-UA,zh,zh-CN,zh-HK,zh-TW,ar,ca,cz,da,el,et,fi,he,hu,ja,lt,lv,nl,no,no-NO,no-NY,nr,pt,sr-SP,sr-YU,th,tr,i-default
INFO: kex: client: diffie-hellman-group1-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521
INFO: kex: client: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
INFO: kex: client: aes128-ctr,aes128-cbc,3des-ctr,3des-cbc,blowfish-cbc
INFO: kex: client: aes128-ctr,aes128-cbc,3des-ctr,3des-cbc,blowfish-cbc
INFO: kex: client: hmac-md5,hmac-sha1,hmac-sha2-256,hmac-sha1-96,hmac-md5-96
INFO: kex: client: hmac-md5,hmac-sha1,hmac-sha2-256,hmac-sha1-96,hmac-md5-96
INFO: kex: client: none
INFO: kex: client: none
INFO: kex: client:
INFO: kex: client:
INFO: kex: server->client aes128-ctr hmac-md5 none
INFO: kex: client->server aes128-ctr hmac-md5 none
INFO: SSH_MSG_KEXDH_INIT sent
INFO: expecting SSH_MSG_KEXDH_REPLY
INFO: ssh_rsa_verify: signature true
WARN: Permanently added '********' (RSA) to the list of known hosts.
INFO: SSH_MSG_NEWKEYS sent
INFO: SSH_MSG_NEWKEYS received
INFO: SSH_MSG_SERVICE_REQUEST sent
INFO: SSH_MSG_SERVICE_ACCEPT received
INFO: Authentications that can continue: gssapi-with-mic,publickey,keyboard-interactive,password
INFO: Next authentication method: gssapi-with-mic


And then it shows the next message

Kerberos username [******]: Kerberos password for ********:


Where the Enter key is pressed automatically for the username by the robot, but the Enter key for the password needs to be pressed from the keyboard.

Answer Source

You have a Kerberos/GSSAPI authentication set as the preferred, yet you does not seem to actually use/want it. As you claim not to specify any username or password for the Kerberos prompts.

The solution is to remove the Kerberos/GSSAPI (gssapi-with-mic) from the list of preferred authentication methods:

session.setConfig(
    "PreferredAuthentications", 
    "publickey,keyboard-interactive,password");

Reference: SFTP connection through Java asking for weird authentication.