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I implemented a Java program that will connect and execute a command in a remote server using JSCH. The problem is that whenever I tried to connect to the server, I got the following exception:
com.jcraft.jsch.JSchException: Session.connect: java.security.InvalidAlgorithmParameterException: Prime size must be multiple of 64, and can only range from 256 to 2048 (inclusive)
I tried the solution of adding the Bouncy Castle provider in jre/lib and security.provider and it works. But I need to make it project dependent, so I tried to add Bouncy Castle in my build path and add manually the Bouncy Castle provider in my program. But after exporting it to jar, I am still receiving the exception.
package services;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.security.Security;
import java.util.Iterator;
import java.util.Properties;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
public class MainService {
public MainService() {
Security.addProvider(new BouncyCastleProvider()); //Adding BouncyCastlePRovider in security
// TODO Auto-generated constructor stub
String report = "";
StringBuilder sb = new StringBuilder();
System.out.println("Running the monitoring...");
System.out.println("Starting printer monitoring...");
PrinterService ps = new PrinterService(); //A service that connects to the server and executes the commands
System.out.println("Building report for printer");
sb.append(ps.buildReport());
System.out.println("Done building report for printer");
System.out.println("Finish printer Monitoring...");
report = sb.toString();
writeToFile(report,"fai");
}
public static void main(String[] args) {
// TODO Auto-generated method stub
MainService msrv = new MainService();
}
public void writeToFile(String contents,String report_name){
try {
System.out.println("Writing to file...");
PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter(report_name+".html",false)));
pw.println(contents);
pw.close();
System.out.println("Done writing...");
} catch (IOException e) {
e.printStackTrace();
}
}
}
Here is my Server utilities that handles server connection:
package utilities;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Properties;
import javax.swing.JOptionPane;
import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;
import entity.Server;
public class ServerUtil {
public ServerUtil() {
// TODO Auto-generated constructor stub
}
public static Session createSession(Server srv){
JSch js = new JSch();
try {
Session s = js.getSession(srv.getUser().getUsername(), srv.getAddress(), 22);
s.setPassword(srv.getUser().getPassword());
Properties config = new Properties();
config.put("StrictHostKeyChecking", "no");
config.put("PreferredAuthentications", "password");
s.setConfig(config);
s.connect();
return s;
} catch (JSchException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return null;
}
}
public static ArrayList<String> executeCommands(Session s, String commands){
ArrayList<String> result = new ArrayList<String>();
try {
System.out.println("Creating channel...");
ChannelExec channel = (ChannelExec) s.openChannel("exec");
System.out.println("Channel created.");
System.out.println("Setting commands...");
channel.setCommand(commands);
System.out.println("Commands set.");
System.out.println("Connecting to channel...");
channel.connect();
System.out.println("Channel connected.");
System.out.println("Retrieving output...");
BufferedReader reader = new BufferedReader(new InputStreamReader(channel.getInputStream()));
String line;
while((line = reader.readLine()) != null){
result.add(line);
}
System.out.println("Output retrieved.");
channel.disconnect();
System.out.println("Returning result...");
return result;
} catch (JSchException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return result;
}catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return result;
}
}
}
While debugging, I find out that the error occurs when the printer service tries to connect to the server.
package services;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.Iterator;
import java.util.StringTokenizer;
import com.jcraft.jsch.Session;
import entity.Server;
import utilities.DatabaseUtil;
import utilities.ServerUtil;
public class PrinterService {
private ArrayList<String> server_names;
private ArrayList<ArrayList<String>> result_server;
public PrinterService() {
// TODO Auto-generated constructor stub
executePrinterMonitoring();
}
//Connect to the printer server and process printer monitoring
public void executePrinterMonitoring(){
Iterator<Server> it_s = DatabaseUtil.getServers("PRINTER").iterator();
server_names = new ArrayList<String>();
result_server = new ArrayList<ArrayList<String>>();
while(it_s.hasNext()){
Server svr = it_s.next();
System.out.println("***********START PRINTER SERVER***********");
String commands = "lpstat -t | sed '/READY/d'; lpstat -W | sed '/READY/d'";
Session connect = ServerUtil.createSession(svr);
StringTokenizer tokenize = new StringTokenizer(commands, ";");
ArrayList<String> res;
ArrayList<ArrayList<String>> res2 = new ArrayList<ArrayList<String>>();
System.out.println("Executing commands...");
while(tokenize.hasMoreTokens()){
String comm = tokenize.nextToken().trim();
res = ServerUtil.executeCommands(connect, comm);
res2.add(res);
}
System.out.println("Done executing commands...");
System.out.println("Processing results...");
processPMonitoring(res2,svr.getName());
connect.disconnect();
System.out.println("***********END PRINTER SERVER***********");
}
}
//Get the current date, date - 1, and date - 2
public String getDate(Calendar cal){
String mon;
String dy;
String dy2;
String dy3;
String yr;
int month = cal.get(Calendar.MONTH)+1;
int day = cal.get(Calendar.DATE);
int year = cal.get(Calendar.YEAR);
if(month < 10)
mon = "0"+month;
else
mon = ""+month;
if(day < 10){
dy = "0"+day;
}
else{
dy = ""+day;
}
yr = (year+"").substring(2, 4);
String date = mon+ "/"+dy+"/"+yr;
return date;
}
//Split and process the result from the server.
public void processPMonitoring(ArrayList<ArrayList<String>> s,String servername){
Iterator<String> res1 = s.get(0).iterator();
Iterator<String> res2 = s.get(1).iterator();
ArrayList<String> as = new ArrayList<String>();
ArrayList<String> fres = new ArrayList<String>();
Calendar cal = Calendar.getInstance();
String date1 = getDate(cal);
cal.add(Calendar.DATE, -1);
String date2 = getDate(cal);
cal.add(Calendar.DATE, -1);
String date3 = getDate(cal);
int header = 1;
System.out.println("Checking server:"+servername);
System.out.println("Getting queued results...");
while(res1.hasNext()){
if(header <= 3){
//as.add(res1.next());
header++;
}
else{
String curr = res1.next();
if(curr.contains("@")){
if(curr.contains("STDIN")){
String f4 = "";
String f5 = "";
if(res1.hasNext())
f4 = res1.next();
if(res1.hasNext())
f5 = res1.next();
if(f4.contains(date1)){
as.add(curr);
}
else if(f4.contains(date2)){
as.add(curr);
}
else if(f4.contains(date3)){
as.add(curr);
}
}
}
else{
String f1 = curr;
String f2 = "";
String f3 = "";
if(res1.hasNext())
f2 = res1.next();
if(res1.hasNext())
f3 = res1.next();
if(f2.contains(date1)){
as.add(f1);
}
else if(f2.contains(date2)){
as.add(f1);
}
else if(f2.contains(date3)){
as.add(f1 + " - 3 DAYS OLD!");
}
}
}
}
System.out.println("Done queued results...");
Iterator<String> g = as.iterator();
boolean flag = true;
String cl = "";
String std = "";
header = 1;
System.out.println("Processing queued results...");
while(res2.hasNext() && g.hasNext()){
if(header <=2){
fres.add(res2.next());
header++;
}
else{
String curr = res2.next();
if(curr.contains("@")){
fres.add(curr);
continue;
}
if(flag){
cl = g.next();
if(cl.contains("@") && cl.contains("STDIN")){
continue;
}
int first_st = cl.indexOf("STDIN");
int last_ind = 0;
for(last_ind = first_st+1;;last_ind++){
//System.out.println("Value of CL:"+cl);
//System.out.println("Checking for spaces");
//System.out.println("STD CURRENT CHAR:"+cl.charAt(last_ind));
if(cl.charAt(last_ind) == ' '){
break;
}
}
std = cl.substring(first_st, last_ind);
flag = false;
if(fres.get(fres.size()-1).contains(std)){
flag = true;
continue;
}
}
if(curr.contains(std)){
fres.add(curr);
flag = true;
}
}
}
System.out.println("Done processing queued results...");
System.out.println("Post-process queued results...");
int size = fres.size();
boolean down = false;
for(int i=0;i<size;i++){
if(fres.get(i).contains("@") && fres.get(i).contains("DOWN")){
down = true;
fres.remove(i);
i--;
size--;
continue;
}
if(down){
if(fres.get(i).contains("@") && !fres.get(i).contains("DOWN")){
down = false;
continue;
}
fres.remove(i);
i--;
size--;
}
}
System.out.println("Done post-processing queued results...");
//Post-process
server_names.add(servername);
result_server.add(fres);
//fres.add(0,servername);
//writeToFile(fres,3);
}
public String buildReport(){
String report = "";
StringBuilder sb = new StringBuilder();
Timestamp ts = new Timestamp(new Date().getTime());
sb.append("<table style=\"border:1px solid black; text-align:center;\" rules=\"all\">");
sb.append("<h1 style=\"margin:0px 0px 0px 50px\">Printer Monitoring as of "+ts.toString()+"</h1>");
sb.append("<tr style=\"background-color: seagreen\">"
+ "<th style=\"padding: 6px\">SERVER</th>"
+ "<th style=\"padding: 6px\">QUEUE</th>"
+ "<th style=\"padding: 6px\">DEV</th>"
+ "<th style=\"padding: 6px\">STATUS</th>"
+ "<th style=\"padding: 6px\">JOB FILES</th>"
+ "<th style=\"padding: 6px\">USER</th>"
+ "<th style=\"padding: 6px\">PP</th>"
+ "<th style=\"padding: 6px\">%</th>"
+ "<th style=\"padding: 6px\">BLKS</th>"
+ "<th style=\"padding: 6px\">CP</th>"
+ "<th style=\"padding: 6px\">RNK</th>"
+ "</tr>");
int counter = 0;
Iterator<String> it_s = server_names.iterator();
while(it_s.hasNext()){
sb.append("<tr style=\"background-color: green\"><td style=\"padding: 6px\"><b>"+it_s.next().toUpperCase()+"</b></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr>");
Iterator<String> it_res = result_server.get(counter).iterator();
if(result_server.get(counter).isEmpty()){
sb.append("<tr><td></td><td style=\"padding: 6px\"><h5>CLEAN</h5></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr>");
}
else if(result_server.get(counter).size() == 2){
sb.append("<tr><td></td><td style=\"padding: 6px\"><h5>CLEAN</h5></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr>");
}
else{
while(it_res.hasNext()){
String res = it_res.next();
if(!res.contains("Dev") && !res.contains("----")){
StringTokenizer tok = new StringTokenizer(res," ");
sb.append("<tr>");
if(tok.countTokens() == 11){
sb.append("<td style=\"padding: 6px\"></td>");
for(int x=0;x<10;x++){
if(x == 3){
sb.append("<td style=\"padding: 6px\">"+tok.nextToken()+" "+tok.nextToken()+"</td>");
}
else{
sb.append("<td style=\"padding: 6px\">"+tok.nextToken()+"</td>");
}
}
}
else{
sb.append("<td style=\"padding: 6px\"></td>");
sb.append("<td style=\"padding: 6px\"></td>");
sb.append("<td style=\"padding: 6px\"></td>");
sb.append("<td style=\"padding: 6px\">"+tok.nextToken()+"</td>");
sb.append("<td style=\"padding: 6px\">"+tok.nextToken()+" "+tok.nextToken()+"</td>");
sb.append("<td style=\"padding: 6px\">"+tok.nextToken()+"</td>");
sb.append("<td style=\"padding: 6px\"></td>");
sb.append("<td style=\"padding: 6px\"></td>");
sb.append("<td style=\"padding: 6px\">"+tok.nextToken()+"</td>");
sb.append("<td style=\"padding: 6px\">"+tok.nextToken()+"</td>");
sb.append("<td style=\"padding: 6px\">"+tok.nextToken()+"</td>");
}
sb.append("</tr>");
}
}
}
counter++;
}
sb.append("</table>");
sb.append("</br></br>");
report = sb.toString();
return report;
}
}
I would also like to know if there is a way to make Bouncy Castle a light weight, since I need my jar to be < 2MB since I need to transfer it to a server, and I don't have a permission to transfer a file > 2MB.
Thank you for the help. This is my first post in stackoverflow, and I really love this community. Thanks.
392
My workaround was changing this registry key to allow 1024 bit DH keys in Windows 10 (2048 was/is the minimum bit size per https://docs.microsoft.com/en-us/security-updates/securityadvisories/2016/3174644)
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\KeyExchangeAlgorithms\Diffie-Hellman]
"ServerMinKeyBitLength"=dword:00000400
I was getting the same error with JGit's use of JSch. I tried a lot of suggestions in this thread to no avail.
But then recently, I noticed that if I used a slightly newer jre than I used before, the error went away.
Just for the record, I was using "jsch-0.1.55.jar" and the two jre's I tried were:
I can't say for sure whether it was merely the JRE upgrade that resolved the problem or the suggested tweaks from this thread that I made in addition.
All the same, just wanted to share the experience in case it helps someone else.
21
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