utils/src/main/java/com/cloud/utils/ssh/SshHelper.java - cloudstack - Git at Google

 //
 // Licensed to the Apache Software Foundation (ASF) under one
 // or more contributor license agreements.  See the NOTICE file
 // distributed with this work for additional information
 // regarding copyright ownership.  The ASF licenses this file
 // to you under the Apache License, Version 2.0 (the
 // "License"); you may not use this file except in compliance
 // with the License.  You may obtain a copy of the License at
 //
 //   http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing,
 // software distributed under the License is distributed on an
 // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 // KIND, either express or implied.  See the License for the
 // specific language governing permissions and limitations
 // under the License.
 //

 package com.cloud.utils.ssh;

 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;

 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang3.StringUtils;

 import org.apache.log4j.Logger;
 import org.joda.time.Duration;

 import com.trilead.ssh2.ChannelCondition;
 import com.trilead.ssh2.Connection;
 import com.trilead.ssh2.Session;
 import com.cloud.utils.Pair;

 public class SshHelper {
     private static final int DEFAULT_CONNECT_TIMEOUT = 180000;
     private static final int DEFAULT_KEX_TIMEOUT = 60000;

     private static final Logger s_logger = Logger.getLogger(SshHelper.class);

     public static Pair<Boolean, String> sshExecute(String host, int port, String user, File pemKeyFile, String password, String command) throws Exception {

         return sshExecute(host, port, user, pemKeyFile, password, command, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT, 120000);
     }

     public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, String localFile, String fileMode)
             throws Exception {

         scpTo(host, port, user, pemKeyFile, password, remoteTargetDirectory, localFile, fileMode, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT);
     }

     public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, String[] localFiles, String fileMode)
             throws Exception {

         scpTo(host, port, user, pemKeyFile, password, remoteTargetDirectory, localFiles, fileMode, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT);
     }

     public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, byte[] data, String remoteFileName,
             String fileMode) throws Exception {

         scpTo(host, port, user, pemKeyFile, password, remoteTargetDirectory, data, remoteFileName, fileMode, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT);
     }

     public static void scpFrom(String host, int port, String user, File permKeyFile, String localTargetDirectory, String remoteTargetFile) throws Exception {
         com.trilead.ssh2.Connection conn = null;
         com.trilead.ssh2.SCPClient scpClient = null;

         try {
             conn = new com.trilead.ssh2.Connection(host, port);
             conn.connect(null, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT);

             if (!conn.authenticateWithPublicKey(user, permKeyFile, null)) {
                 String msg = "Failed to authentication SSH user " + user + " on host " + host;
                 s_logger.error(msg);
                 throw new Exception(msg);
             }
             scpClient = conn.createSCPClient();

             scpClient.get(remoteTargetFile, localTargetDirectory);

         } finally {
             if (conn != null) {
                 conn.close();
             }
         }
     }

     public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, String localFile, String fileMode,
             int connectTimeoutInMs, int kexTimeoutInMs) throws Exception {

         com.trilead.ssh2.Connection conn = null;
         com.trilead.ssh2.SCPClient scpClient = null;

         try {
             conn = new com.trilead.ssh2.Connection(host, port);
             conn.connect(null, connectTimeoutInMs, kexTimeoutInMs);

             if (pemKeyFile == null) {
                 if (!conn.authenticateWithPassword(user, password)) {
                     String msg = "Failed to authentication SSH user " + user + " on host " + host;
                     s_logger.error(msg);
                     throw new Exception(msg);
                 }
             } else {
                 if (!conn.authenticateWithPublicKey(user, pemKeyFile, password)) {
                     String msg = "Failed to authentication SSH user " + user + " on host " + host;
                     s_logger.error(msg);
                     throw new Exception(msg);
                 }
             }

             scpClient = conn.createSCPClient();

             if (fileMode != null)
                 scpClient.put(localFile, remoteTargetDirectory, fileMode);
             else
                 scpClient.put(localFile, remoteTargetDirectory);
         } finally {
             if (conn != null)
                 conn.close();
         }
     }

     public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, String[] localFiles, String fileMode,
                              int connectTimeoutInMs, int kexTimeoutInMs) throws Exception {

         com.trilead.ssh2.Connection conn = null;
         com.trilead.ssh2.SCPClient scpClient = null;

         try {
             conn = new com.trilead.ssh2.Connection(host, port);
             conn.connect(null, connectTimeoutInMs, kexTimeoutInMs);

             if (pemKeyFile == null) {
                 if (!conn.authenticateWithPassword(user, password)) {
                     String msg = "Failed to authentication SSH user " + user + " on host " + host;
                     s_logger.error(msg);
                     throw new Exception(msg);
                 }
             } else {
                 if (!conn.authenticateWithPublicKey(user, pemKeyFile, password)) {
                     String msg = "Failed to authentication SSH user " + user + " on host " + host;
                     s_logger.error(msg);
                     throw new Exception(msg);
                 }
             }

             scpClient = conn.createSCPClient();

             if (fileMode != null)
                 scpClient.put(localFiles, remoteTargetDirectory, fileMode);
             else
                 scpClient.put(localFiles, remoteTargetDirectory);
         } finally {
             if (conn != null)
                 conn.close();
         }
     }

     public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, byte[] data, String remoteFileName,
             String fileMode, int connectTimeoutInMs, int kexTimeoutInMs) throws Exception {

         com.trilead.ssh2.Connection conn = null;
         com.trilead.ssh2.SCPClient scpClient = null;

         try {
             conn = new com.trilead.ssh2.Connection(host, port);
             conn.connect(null, connectTimeoutInMs, kexTimeoutInMs);

             if (pemKeyFile == null) {
                 if (!conn.authenticateWithPassword(user, password)) {
                     String msg = "Failed to authentication SSH user " + user + " on host " + host;
                     s_logger.error(msg);
                     throw new Exception(msg);
                 }
             } else {
                 if (!conn.authenticateWithPublicKey(user, pemKeyFile, password)) {
                     String msg = "Failed to authentication SSH user " + user + " on host " + host;
                     s_logger.error(msg);
                     throw new Exception(msg);
                 }
             }

             scpClient = conn.createSCPClient();
             if (fileMode != null)
                 scpClient.put(data, remoteFileName, remoteTargetDirectory, fileMode);
             else
                 scpClient.put(data, remoteFileName, remoteTargetDirectory);
         } finally {
             if (conn != null)
                 conn.close();
         }
     }

     public static Pair<Boolean, String> sshExecute(String host, int port, String user, File pemKeyFile, String password, String command, Duration connectTimeout,
             Duration kexTimeout, Duration waitTime) throws Exception {
         return sshExecute(host, port, user, pemKeyFile, password, command, (int)connectTimeout.getMillis(), (int)kexTimeout.getMillis(), (int)waitTime.getMillis());
     }

     public static Pair<Boolean, String> sshExecute(String host, int port, String user, File pemKeyFile, String password, String command, int connectTimeoutInMs, int kexTimeoutInMs,
             int waitResultTimeoutInMs) throws Exception {

         com.trilead.ssh2.Connection conn = null;
         com.trilead.ssh2.Session sess = null;
         try {
             conn = new com.trilead.ssh2.Connection(host, port);
             conn.connect(null, connectTimeoutInMs, kexTimeoutInMs);

             if (pemKeyFile == null) {
                 if (!conn.authenticateWithPassword(user, password)) {
                     String msg = "Failed to authentication SSH user " + user + " on host " + host;
                     s_logger.error(msg);
                     throw new Exception(msg);
                 }
             } else {
                 if (!conn.authenticateWithPublicKey(user, pemKeyFile, password)) {
                     String msg = "Failed to authentication SSH user " + user + " on host " + host;
                     s_logger.error(msg);
                     throw new Exception(msg);
                 }
             }
             sess = openConnectionSession(conn);

             sess.execCommand(command);

             InputStream stdout = sess.getStdout();
             InputStream stderr = sess.getStderr();

             byte[] buffer = new byte[8192];
             StringBuffer sbResult = new StringBuffer();
             int currentReadBytes = 0;
             while (true) {
                 throwSshExceptionIfStdoutOrStdeerIsNull(stdout, stderr);

                 if ((stdout.available() == 0) && (stderr.available() == 0)) {
                     int conditions = sess.waitForCondition(ChannelCondition.STDOUT_DATA | ChannelCondition.STDERR_DATA | ChannelCondition.EOF | ChannelCondition.EXIT_STATUS,
                             waitResultTimeoutInMs);

                     throwSshExceptionIfConditionsTimeout(conditions);

                     if ((conditions & ChannelCondition.EXIT_STATUS) != 0) {
                         break;
                     }

                     if (canEndTheSshConnection(waitResultTimeoutInMs, sess, conditions)) {
                         break;
                     }
                 }

                while((currentReadBytes = stdout.read(buffer)) != -1) {
                     sbResult.append(new String(buffer, 0 , currentReadBytes));
                 }

                 while((currentReadBytes = stderr.read(buffer)) != -1) {
                     sbResult.append(new String(buffer, 0, currentReadBytes));
                 }
             }

             String result = sbResult.toString();
             if (StringUtils.isBlank(result)) {
                 try {
                     result = IOUtils.toString(stdout, StandardCharsets.UTF_8);
                 }
                 catch (IOException e) {
                     s_logger.error("Couldn't get content of input stream due to: " + e.getMessage());
                     return new Pair<Boolean, String>(false, result);
                 }
             }

             if (sess.getExitStatus() == null) {
                 //Exit status is NOT available. Returning failure result.
                 s_logger.error(String.format("SSH execution of command %s has no exit status set. Result output: %s", command, result));
                 return new Pair<Boolean, String>(false, result);
             }

             if (sess.getExitStatus() != null && sess.getExitStatus().intValue() != 0) {
                 s_logger.error(String.format("SSH execution of command %s has an error status code in return. Result output: %s", command, result));
                 return new Pair<Boolean, String>(false, result);
             }
             return new Pair<Boolean, String>(true, result);
         } finally {
             if (sess != null)
                 sess.close();

             if (conn != null)
                 conn.close();
         }
     }


     protected static Session openConnectionSession(Connection conn) throws IOException, InterruptedException {
         Session sess = conn.openSession();
         return sess;
     }

     /**
      * Handles the SSH connection in case of timeout or exit. If the session ends with a timeout
      * condition, it throws an exception; if the channel reaches an end of file condition, but it
      * does not have an exit status, it returns true to break the loop; otherwise, it returns
      * false.
      */
     protected static boolean canEndTheSshConnection(int waitResultTimeoutInMs, com.trilead.ssh2.Session sess, int conditions) throws SshException, InterruptedException {
         if (isChannelConditionEof(conditions)) {
             int newConditions = sess.waitForCondition(ChannelCondition.EXIT_STATUS, waitResultTimeoutInMs);
             throwSshExceptionIfConditionsTimeout(newConditions);
             if ((newConditions & ChannelCondition.EXIT_STATUS) != 0) {
                 return true;
             }
         }
         return false;
     }

     /**
      * It throws a {@link SshException} if the channel condition is {@link ChannelCondition#TIMEOUT}
      */
     protected static void throwSshExceptionIfConditionsTimeout(int conditions) throws SshException {
         if ((conditions & ChannelCondition.TIMEOUT) != 0) {
             String msg = "Timed out in waiting for SSH execution exit status";
             s_logger.error(msg);
             throw new SshException(msg);
         }
     }

     /**
      * Checks if the channel condition mask is of {@link ChannelCondition#EOF} and not
      * {@link ChannelCondition#STDERR_DATA} or {@link ChannelCondition#STDOUT_DATA}.
      */
     protected static boolean isChannelConditionEof(int conditions) {
         if ((conditions & ChannelCondition.EOF) != 0) {
             return true;
         }
         return false;
     }

     /**
      * Checks if the SSH session {@link com.trilead.ssh2.Session#getStdout()} or
      * {@link com.trilead.ssh2.Session#getStderr()} is null.
      */
     protected static void throwSshExceptionIfStdoutOrStdeerIsNull(InputStream stdout, InputStream stderr) throws SshException {
         if (stdout == null || stderr == null) {
             String msg = "Stdout or Stderr of SSH session is null";
             s_logger.error(msg);
             throw new SshException(msg);
         }
     }
 }
	//
	// Licensed to the Apache Software Foundation (ASF) under one
	// or more contributor license agreements. See the NOTICE file
	// distributed with this work for additional information
	// regarding copyright ownership. The ASF licenses this file
	// to you under the Apache License, Version 2.0 (the
	// "License"); you may not use this file except in compliance
	// with the License. You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing,
	// software distributed under the License is distributed on an
	// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
	// KIND, either express or implied. See the License for the
	// specific language governing permissions and limitations
	// under the License.
	//

	package com.cloud.utils.ssh;

	import java.io.File;
	import java.io.IOException;
	import java.io.InputStream;
	import java.nio.charset.StandardCharsets;

	import org.apache.commons.io.IOUtils;
	import org.apache.commons.lang3.StringUtils;

	import org.apache.log4j.Logger;
	import org.joda.time.Duration;

	import com.trilead.ssh2.ChannelCondition;
	import com.trilead.ssh2.Connection;
	import com.trilead.ssh2.Session;
	import com.cloud.utils.Pair;

	public class SshHelper {
	private static final int DEFAULT_CONNECT_TIMEOUT = 180000;
	private static final int DEFAULT_KEX_TIMEOUT = 60000;

	private static final Logger s_logger = Logger.getLogger(SshHelper.class);

	public static Pair<Boolean, String> sshExecute(String host, int port, String user, File pemKeyFile, String password, String command) throws Exception {

	return sshExecute(host, port, user, pemKeyFile, password, command, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT, 120000);
	}

	public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, String localFile, String fileMode)
	throws Exception {

	scpTo(host, port, user, pemKeyFile, password, remoteTargetDirectory, localFile, fileMode, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT);
	}

	public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, String[] localFiles, String fileMode)
	throws Exception {

	scpTo(host, port, user, pemKeyFile, password, remoteTargetDirectory, localFiles, fileMode, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT);
	}

	public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, byte[] data, String remoteFileName,
	String fileMode) throws Exception {

	scpTo(host, port, user, pemKeyFile, password, remoteTargetDirectory, data, remoteFileName, fileMode, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT);
	}

	public static void scpFrom(String host, int port, String user, File permKeyFile, String localTargetDirectory, String remoteTargetFile) throws Exception {
	com.trilead.ssh2.Connection conn = null;
	com.trilead.ssh2.SCPClient scpClient = null;

	try {
	conn = new com.trilead.ssh2.Connection(host, port);
	conn.connect(null, DEFAULT_CONNECT_TIMEOUT, DEFAULT_KEX_TIMEOUT);

	if (!conn.authenticateWithPublicKey(user, permKeyFile, null)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	scpClient = conn.createSCPClient();

	scpClient.get(remoteTargetFile, localTargetDirectory);

	} finally {
	if (conn != null) {
	conn.close();
	}
	}
	}

	public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, String localFile, String fileMode,
	int connectTimeoutInMs, int kexTimeoutInMs) throws Exception {

	com.trilead.ssh2.Connection conn = null;
	com.trilead.ssh2.SCPClient scpClient = null;

	try {
	conn = new com.trilead.ssh2.Connection(host, port);
	conn.connect(null, connectTimeoutInMs, kexTimeoutInMs);

	if (pemKeyFile == null) {
	if (!conn.authenticateWithPassword(user, password)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	} else {
	if (!conn.authenticateWithPublicKey(user, pemKeyFile, password)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	}

	scpClient = conn.createSCPClient();

	if (fileMode != null)
	scpClient.put(localFile, remoteTargetDirectory, fileMode);
	else
	scpClient.put(localFile, remoteTargetDirectory);
	} finally {
	if (conn != null)
	conn.close();
	}
	}

	public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, String[] localFiles, String fileMode,
	int connectTimeoutInMs, int kexTimeoutInMs) throws Exception {

	com.trilead.ssh2.Connection conn = null;
	com.trilead.ssh2.SCPClient scpClient = null;

	try {
	conn = new com.trilead.ssh2.Connection(host, port);
	conn.connect(null, connectTimeoutInMs, kexTimeoutInMs);

	if (pemKeyFile == null) {
	if (!conn.authenticateWithPassword(user, password)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	} else {
	if (!conn.authenticateWithPublicKey(user, pemKeyFile, password)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	}

	scpClient = conn.createSCPClient();

	if (fileMode != null)
	scpClient.put(localFiles, remoteTargetDirectory, fileMode);
	else
	scpClient.put(localFiles, remoteTargetDirectory);
	} finally {
	if (conn != null)
	conn.close();
	}
	}

	public static void scpTo(String host, int port, String user, File pemKeyFile, String password, String remoteTargetDirectory, byte[] data, String remoteFileName,
	String fileMode, int connectTimeoutInMs, int kexTimeoutInMs) throws Exception {

	com.trilead.ssh2.Connection conn = null;
	com.trilead.ssh2.SCPClient scpClient = null;

	try {
	conn = new com.trilead.ssh2.Connection(host, port);
	conn.connect(null, connectTimeoutInMs, kexTimeoutInMs);

	if (pemKeyFile == null) {
	if (!conn.authenticateWithPassword(user, password)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	} else {
	if (!conn.authenticateWithPublicKey(user, pemKeyFile, password)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	}

	scpClient = conn.createSCPClient();
	if (fileMode != null)
	scpClient.put(data, remoteFileName, remoteTargetDirectory, fileMode);
	else
	scpClient.put(data, remoteFileName, remoteTargetDirectory);
	} finally {
	if (conn != null)
	conn.close();
	}
	}

	public static Pair<Boolean, String> sshExecute(String host, int port, String user, File pemKeyFile, String password, String command, Duration connectTimeout,
	Duration kexTimeout, Duration waitTime) throws Exception {
	return sshExecute(host, port, user, pemKeyFile, password, command, (int)connectTimeout.getMillis(), (int)kexTimeout.getMillis(), (int)waitTime.getMillis());
	}

	public static Pair<Boolean, String> sshExecute(String host, int port, String user, File pemKeyFile, String password, String command, int connectTimeoutInMs, int kexTimeoutInMs,
	int waitResultTimeoutInMs) throws Exception {

	com.trilead.ssh2.Connection conn = null;
	com.trilead.ssh2.Session sess = null;
	try {
	conn = new com.trilead.ssh2.Connection(host, port);
	conn.connect(null, connectTimeoutInMs, kexTimeoutInMs);

	if (pemKeyFile == null) {
	if (!conn.authenticateWithPassword(user, password)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	} else {
	if (!conn.authenticateWithPublicKey(user, pemKeyFile, password)) {
	String msg = "Failed to authentication SSH user " + user + " on host " + host;
	s_logger.error(msg);
	throw new Exception(msg);
	}
	}
	sess = openConnectionSession(conn);

	sess.execCommand(command);

	InputStream stdout = sess.getStdout();
	InputStream stderr = sess.getStderr();

	byte[] buffer = new byte[8192];
	StringBuffer sbResult = new StringBuffer();
	int currentReadBytes = 0;
	while (true) {
	throwSshExceptionIfStdoutOrStdeerIsNull(stdout, stderr);

	if ((stdout.available() == 0) && (stderr.available() == 0)) {
	int conditions = sess.waitForCondition(ChannelCondition.STDOUT_DATA \| ChannelCondition.STDERR_DATA \| ChannelCondition.EOF \| ChannelCondition.EXIT_STATUS,
	waitResultTimeoutInMs);

	throwSshExceptionIfConditionsTimeout(conditions);

	if ((conditions & ChannelCondition.EXIT_STATUS) != 0) {
	break;
	}

	if (canEndTheSshConnection(waitResultTimeoutInMs, sess, conditions)) {
	break;
	}
	}

	while((currentReadBytes = stdout.read(buffer)) != -1) {
	sbResult.append(new String(buffer, 0 , currentReadBytes));
	}

	while((currentReadBytes = stderr.read(buffer)) != -1) {
	sbResult.append(new String(buffer, 0, currentReadBytes));
	}
	}

	String result = sbResult.toString();
	if (StringUtils.isBlank(result)) {
	try {
	result = IOUtils.toString(stdout, StandardCharsets.UTF_8);
	}
	catch (IOException e) {
	s_logger.error("Couldn't get content of input stream due to: " + e.getMessage());
	return new Pair<Boolean, String>(false, result);
	}
	}

	if (sess.getExitStatus() == null) {
	//Exit status is NOT available. Returning failure result.
	s_logger.error(String.format("SSH execution of command %s has no exit status set. Result output: %s", command, result));
	return new Pair<Boolean, String>(false, result);
	}

	if (sess.getExitStatus() != null && sess.getExitStatus().intValue() != 0) {
	s_logger.error(String.format("SSH execution of command %s has an error status code in return. Result output: %s", command, result));
	return new Pair<Boolean, String>(false, result);
	}
	return new Pair<Boolean, String>(true, result);
	} finally {
	if (sess != null)
	sess.close();

	if (conn != null)
	conn.close();
	}
	}


	protected static Session openConnectionSession(Connection conn) throws IOException, InterruptedException {
	Session sess = conn.openSession();
	return sess;
	}

	/**
	* Handles the SSH connection in case of timeout or exit. If the session ends with a timeout
	* condition, it throws an exception; if the channel reaches an end of file condition, but it
	* does not have an exit status, it returns true to break the loop; otherwise, it returns
	* false.
	*/
	protected static boolean canEndTheSshConnection(int waitResultTimeoutInMs, com.trilead.ssh2.Session sess, int conditions) throws SshException, InterruptedException {
	if (isChannelConditionEof(conditions)) {
	int newConditions = sess.waitForCondition(ChannelCondition.EXIT_STATUS, waitResultTimeoutInMs);
	throwSshExceptionIfConditionsTimeout(newConditions);
	if ((newConditions & ChannelCondition.EXIT_STATUS) != 0) {
	return true;
	}
	}
	return false;
	}

	/**
	* It throws a {@link SshException} if the channel condition is {@link ChannelCondition#TIMEOUT}
	*/
	protected static void throwSshExceptionIfConditionsTimeout(int conditions) throws SshException {
	if ((conditions & ChannelCondition.TIMEOUT) != 0) {
	String msg = "Timed out in waiting for SSH execution exit status";
	s_logger.error(msg);
	throw new SshException(msg);
	}
	}

	/**
	* Checks if the channel condition mask is of {@link ChannelCondition#EOF} and not
	* {@link ChannelCondition#STDERR_DATA} or {@link ChannelCondition#STDOUT_DATA}.
	*/
	protected static boolean isChannelConditionEof(int conditions) {
	if ((conditions & ChannelCondition.EOF) != 0) {
	return true;
	}
	return false;
	}

	/**
	* Checks if the SSH session {@link com.trilead.ssh2.Session#getStdout()} or
	* {@link com.trilead.ssh2.Session#getStderr()} is null.
	*/
	protected static void throwSshExceptionIfStdoutOrStdeerIsNull(InputStream stdout, InputStream stderr) throws SshException {
	if (stdout == null \|\| stderr == null) {
	String msg = "Stdout or Stderr of SSH session is null";
	s_logger.error(msg);
	throw new SshException(msg);
	}
	}
	}