Linux Ubuntu - SSH command to copy server to local or vice versa

 Copy file to Server to Local

    scp -P <port> <localfile path> <server user>@ip:<remote user home path>

    ex: > scp -P 22 mq/target/test.jar drvijay@192.2.2.2:/home/drvijay

Connect server : 

        ssh -p <port> <server user>@<IP>

        ssh -p 22 drvijay@182.2.2.2

Copy file from Server to Local

 

Note: ssh -p <port> small case for port option

          scp -P <port> upper -P for port specify.

Ms Sql server problem with linux python django app/settings.py

 From Database {section}

'driver': 'SQL Server Native Client 11.0',

To         

    'driver': 'ODBC Driver 17 for SQL Server'

ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) [ERROR] [MY-010187] [Server] Could not open file '/var/log/mysql/error.log' for error logging: Permission denied

    sudo rm /var/log/mysqld.log
    systemctl reload apparmor
    touch /var/log/mysqld.log
    chown mysql:mysql /var/log/mysqld.log
    chmod 0644 /var/log/mysqld.log
    systemctl restart mysql

React or Localhsot CORS Error to Solve in Server Side Filters

package com.drvijayy2k2;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import com.product.sr.global.utils.Constants;

/**
 * The Class ContextFilters
 * ******* THIS CONTROLLER IS THE COMMON filter for the API context, this will receive all the request/response ********
 *
 * @author drvijay
 */

@Component
@Order ( 1 )
public class ContextFilters implements Filter, Constants
{


    /*
     * (non-Javadoc)
     * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
     */
    @Override
    public void init ( FilterConfig arg0 ) throws ServletException
    {
    }

    /*
     * (non-Javadoc)
     * @see javax.servlet.Filter#destroy()
     */
    @Override
    public void destroy ()
    {
    }

    /*
     * (non-Javadoc)
     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
     */
    @Override
    public void doFilter ( ServletRequest request, ServletResponse response, FilterChain chain ) throws IOException, ServletException
    {
        try
        {
            HttpServletRequest req = (HttpServletRequest) request;
            HttpServletResponse res = (HttpServletResponse) response;

            res.setHeader ( "Access-Control-Allow-Origin", "*" );
            res.setHeader ( "Access-Control-Allow-Credentials", "true" );
            res.setHeader ( "Access-Control-Allow-Methods", "ACL, CANCELUPLOAD, CHECKIN, CHECKOUT, COPY, DELETE, GET, HEAD, LOCK, MKCALENDAR, MKCOL, MOVE, OPTIONS, POST, PROPFIND, PROPPATCH, PUT, REPORT, SEARCH, UNCHECKOUT, UNLOCK, UPDATE, VERSION-CONTROL" );
            res.setHeader ( "Access-Control-Max-Age", "3600" );
            res.setHeader ( "Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, Key, Authorization" );

            if ( "OPTIONS".equalsIgnoreCase ( req.getMethod () ) )
            {
                res.setStatus ( HttpServletResponse.SC_OK );
            }
            else
            {
                chain.doFilter ( req, res );
            }

        }
        catch ( Exception e )
        {
            //error
        }
    }

}

.htaccess file gives 500 internal server error

1. In your root folder
2. Create .htaccess file in your project root directory like below.

.htaccess

    RewriteEngine on
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-l
    RewriteRule ^(.*)$ index.php?url=$1 [QSA,L]

3. Save .htaccess file.

Python - Expecting property key name enclosed in double quotes - String to JSON

import demjson 
result = demjson.decode(' { key: "value" }' )


demjson plugin is very good on this

- Enjoy 

Error: The server encountered an error processing the request. See server logs for more details

This issue comes into picture whenever there is any issue at WCF service.
So see more details about the issue, you need to includeexceptiondetailInfaults attribute to true in servicedebug tag.

Go to your web.config

<servicebehaviors>
        <behavior name="myServiceBehavior">
          <servicedebug includeexceptiondetailinfaults="true" />
        </behavior>
</servicebehaviors>

Either you can also add class attribute to the service class.

Password Encrypt in JavaScript and Decrypt in Java

here is the steps,

1. create two jsps. [ login.jsp, validate.jsp ]
2. create one java.
3. Add cryptojs lib [ aes.js ] in your javascript path and mentioned in login.jsp.

here is the sample code.


1. login.jsp

<%@page import="java.util.Arrays"%>
<%@page import="package.Security"%>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
  
<%
    session.setAttribute ( "RANDKEY", Security.generateSecret (  ) );
%>
  
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
<script src="./js/rollups/aes.js"></script>
<script src="./js/rollups/pbkdf2.js"></script>
<script type="text/javascript">
    function convertAndSubmit()
    {
         var salt = CryptoJS.lib.WordArray.random(128/8);
        var iv = CryptoJS.lib.WordArray.random(128/8);          
        //console.log('salt  '+ salt );
        //console.log('iv  '+ iv );
        var key128Bits100Iterations = CryptoJS.PBKDF2( '<%=session.getAttribute ( "RANDKEY" ) %>', salt, { keySize: 128/32, iterations: 100 });
        //console.log( 'key128Bits100Iterations '+ key128Bits100Iterations);
        var encrypted = CryptoJS.AES.encrypt(document.login.password.value, key128Bits100Iterations, { iv: iv, mode: CryptoJS.mode.CBC, padding: CryptoJS.pad.Pkcs7  });
        document.login.salt.value = salt;
        document.login.iv.value = iv;
        document.login.password.value = encrypted;
        document.login.submit();
    }
</script>
</head>
<body>
    <form action="validate.jsp" method="post" name="login" autocomplete="off">
        <p>User Name : <input type="text" name="userName"/></p>
        <p>
                       <input type="text" style="display:none;">
            Password : <input type="password" name="password"/>
        </p>
        <p>
            <input type="hidden" name="salt"/>
            <input type="hidden" name="iv"/>
            <input type="button" value="Login" onclick="javascript:convertAndSubmit()"/>
        </p>
    </form>
</body>
</html>










   

        User Name :

       
                      
            Password :
       

       
           
           
           
       

   

2. validate.jsp


<%@page import="java.util.Arrays"%>
<%@page import="package.Security"%>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
</head>
<body>
    <%
        out.println ("<br/>Encrypted Password     :    " + request.getParameter("password"));
        out.println ("<br/>Salt                 :    " + request.getParameter("salt"));
        out.println ("<br/>IV                     :    " + request.getParameter("iv"));
        out.println ("<br/>Key                 :    " + session.getAttribute ( "RANDKEY" ) );
        out.println ("<br/>Original Password     :    " + Security.decryptAESEncryptWithSaltAndIV(request.getParameter("password"), session.getAttribute ( "RANDKEY" ).toString (  ), request.getParameter("salt"), request.getParameter("iv") ) );   
    %>
</body>
</html>






    <%
        out.println ("
Encrypted Password     :    " + request.getParameter("password"));
        out.println ("
Salt                 :    " + request.getParameter("salt"));
        out.println ("
IV                     :    " + request.getParameter("iv"));
        out.println ("
Key                 :    " + session.getAttribute ( "RANDKEY" ) );
        out.println ("
Original Password     :    " + YourJava.decryptAESEncryptWithSaltAndIV(request.getParameter("password"), session.getAttribute ( "RANDKEY" ).toString (  ), request.getParameter("salt"), request.getParameter("iv") ) );   
    %>

3. Security.java [add the below methods ]

/**
     * Hex string to byte array.
     *
     * @param s the s
     * @return the byte[]
     */
    public static byte [] hexStringToByteArray ( String s )
    {
        int len = s.length ();
        byte [] data = new byte[len / 2];
        for ( int i = 0; i < len; i += 2 )
        {
            data[i / 2] = (byte) ( ( Character.digit ( s.charAt ( i ), 16 ) << 4 ) + Character.digit ( s.charAt ( i + 1 ), 16 ) );
        }
        return data;
    }

   
    /**
     * Generate key from password with salt.
     *
     * @param password the password
     * @param saltBytes the salt bytes
     * @return the secret key
     * @throws GeneralSecurityException the general security exception
     */
    public static SecretKey generateKeyFromPasswordWithSalt ( String password, byte [] saltBytes ) throws GeneralSecurityException
    {
        KeySpec keySpec = new PBEKeySpec ( password.toCharArray (), saltBytes, 100, 128 );
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance ( PBKDF2_WITH_HMAC_SHA1 );
        SecretKey secretKey = keyFactory.generateSecret ( keySpec );

        return new SecretKeySpec ( secretKey.getEncoded (), AES );
    }

    /**
     * Decrypt aes encrypt with salt and iv.
     *
     * @param encryptedData the encrypted data
     * @param key the key
     * @param salt the salt
     * @param iv the iv
     * @return the string
     * @throws Exception the exception
     */
    public static String decryptAESEncryptWithSaltAndIV ( String encryptedData, String key, String salt, String iv ) throws Exception
    {

        byte [] saltBytes = hexStringToByteArray ( salt );
        byte [] ivBytes = hexStringToByteArray ( iv );
        IvParameterSpec ivParameterSpec = new IvParameterSpec ( ivBytes );
        SecretKeySpec sKey = (SecretKeySpec) generateKeyFromPasswordWithSalt ( key, saltBytes );

        Cipher c = Cipher.getInstance ( AES_CBC_PKCS5_PADDING );
        c.init ( Cipher.DECRYPT_MODE, sKey, ivParameterSpec );
        byte [] decordedValue = new BASE64Decoder ().decodeBuffer ( encryptedData );
        byte [] decValue = c.doFinal ( decordedValue );
        String decryptedValue = new String ( decValue );

        return decryptedValue;
    }

public String generateSecret (  )
{
    return "1234455553dsfdfdsfdsf";   //generate always random number and send for each request
}

 // enjoy madi.

Hosting more than a .NET remoting singleton server in the same process

I had the need of having three different singleton remoting object in the same process.
This post explains how I solved out the trick.

I have a windows application exposing via remoting three singleton objects, let' call them "S_a", "S_b" and "S_Main" .

"S_a" and "S_b" are instantiated by remote client applications.
"S_Main" object is instantiated by "S_a" and "S_b".
"S_a", "S_b" and "S_Main" resides on the same process, as I told before.
"S_a" and "S_b" are WellKnownServiceTypes.
"S_Main" is to be both a WellKnownServiceType (this is inside the server-application code where a port is open in listening mode) and a WellKnownClientType when configuring "S_a" and "S_b" for its instantiation (i.e inside "S_a" and "S_b" class definition there will be a point in which we say that "S_Main" is not a local object and is to be instantiated via remoting at a certain URL).

Triing to configure remoting in this way, leads to the generation of the Exception:
"Remoting configuration failed with the exception System.Runtime.Remoting.RemotingException"

"Attempt to redirect activation for type" [...]
"This is not allowed since either a well-known service type has already
been registered with that type or that type has been registered has a
activated service type"

The solution is to have the three singletons in three different appdomains hosted in the same windows process.

First thing to setup is to have three assemblies every one exposing a method which will configure remoting server-side for a single singleton. The classes inside these assemblies must inherit MarshalByRefObject.
In this way instantiating these three classes and calling the method on them, will open three ports in listening mode.

Every assembly is to be loaded in a different appdomain. In this way, inside the "S_A_AppDomain" (and also in "S_B_AppDomain") the "S_Main" object is configured as a WellKnownClientType, while in the S_Main_AppDomain it is configured as a WellKnownServiceType.
AppDomains provide proper isolation.

An Appdomain is created in this way:

Dim domaininfo As New AppDomainSetup
domaininfo.ApplicationBase = AppDomain.CurrentDomain.BaseDirectory

dim S_A_Domain As AppDomain = _
AppDomain.CreateDomain("S_A_RemotingServer", Nothing, domaininfo)
Here is the code used to load an assembly (ex: "Assembly.dll") inside the appdomain, instantiate the class (ex: "namespace.classname", which will reside in the newly created appdomain) and invoke the method that will configure remoting server-side (ex: "ActivateServer") :

Dim ann As [Assembly] = [Assembly].LoadFrom("Assembly.dll")

'Load the assembly in the appdomain
Dim a As [Assembly] = S_A_Domain.Load(ann.FullName)

'Create an instance (on the new appdomain)
Dim obj As Object = S_A_Domain.CreateInstanceAndUnwrap(ann.FullName, "namespace.classname")

'Get the type to use.
Dim myType As Type = a.GetType("namespace.classname")
'Get the method to call.
Dim mymethod As MethodInfo = myType.GetMethod("ActivateServer")

'Execute the method.
mymethod.Invoke(obj, Nothing)

The method is invoked in the instance of the class which resides in the separate appdomain, configuring remoting.