Category Archives: Non classé

SSH connection from Jenkins


How to access remotely to a machine from jenkins without storing password ?

– We were using maven ssh plugin to remotely access a machine. However this solution was not satisfying because the password of the username was stored inside a file. We should not expose the password in a file.


The solution chosen is using the Credentials Jenkins plugin

Configure the job to pass the SSH private-key using an SSH agent

This allows the user to securely provide access to remote resources (using SSH authentication) without exposing the SSH private-key material to the job.

1. Create key private and key public :

In a linux machine , generate a key pair-value pulic and private , with the following command

It generates, in the folder .ssh, two files : id_rsa et
o Id_rsa is the private key , it should be added on Jenkins.
o is the public key, it should be added on the distant server to be recognized by Jenkins.

2. Add the public key on the target distant server

We put the public key in the folder .ssh of the home of the user with wich we will access. It is added in the files called authorized_keys of the hidden folder “.ssh”

3. Add the private key in Jenkins

Go to manage Credentials and follow steps from here to add a username which can access the distant machine :

Select “SSH Username with private key”

4. Modify The build to allow SSH Agent

Choose the username you will like to use to access to the distant machine.


Following this, it is possible to access remotely with ssh from Jenkins with no login/password. It applied only to the machine which has username with public key in .ssh/authorized_keys folder.


Ssh Credentials Management :


Session ID in the URL : is it a vulnerability ?


I noticed at authentication of several JAVA web applications, the Session ID attached at the url like this…

When first authenticated, the website reveals in the URL a sensitive information “the session ID”. This is a security risk according to OWASP reference.
Indeed if an attacker get the session ID it can lead to the vulnerability of session fixation.

Scanner like Acunetix will detect is as a security risk too:

Why the session id is passed to the URL ?

According to this post, it is by design of JavaEE:

This isn’t a bug, it’s by design. When a new session is created, the server isn’t sure if the client supports cookies or not, and so it generates a cookie as well as the jsessionid on the URL. When the client comes back the second time, and presents the cookie, the server knows the jsessionid isn’t necessary, and drops it for the rest of the session. If the client comes back with no cookie, then the server needs to continue to use jsessionid rewriting.
You may not explicitly use cookies, but you do implicitly have a session, and the container needs to track that session.

What is a Session Fixation ?

Session Fixation is an attack that permits an attacker to hijack a valid user session.

This vulnerability is part of Top 10 2013-A2-Broken Authentication and Session Management

How to test for Session Fixation ?

What is a Session ?

HTTP protocol and Web Servers are stateless, what it means is that for web server every request is a new request to process and they can’t identify if it’s coming from client that has been sending request previously.

But sometimes in web applications, we should know who the client is and process the request accordingly. For example, a shopping cart application should know who is sending the request to add an item and in which cart the item has to be added or who is sending checkout request so that it can charge the amount to correct client.

This is a link to Servlet specification to understand better the session scope in Java :

SRV.7.3 Session Scope
HttpSession objects must be scoped at the application (or servlet context) level. The underlying mechanism, such as the cookie used to establish the session, can be the same for different contexts, but the object referenced, including the attributes in that object, must never be shared between contexts by the container.


Validate Session Id on server side
For sometimes i thought that cookies or hidden input fields is the solution against the “session ID” in the url. According to the link below it is a limited solution. Even if it is hard to copy paste cookies and hidden fields it is still possible to retrieve the Session ID information with special tools on unencrypted website.

Depending of the website it is possible that the sessionId on the URL is not a security risk. If the web application is well designed and the session ID is validated on server side, this is not a problem :

The best practice , in all case is to validate on the server side.
Other solutions are possible :

Use Filter to get rid of Session ID in URL

Here is an example of using a Filter to get rid of session Id in the URL :

I believe this solution is not necessary if good validation of session ID is done on the server Side.

Spring Security Framework

Probably the best solution for JavaEE is to use well tested framework like spring security framework. It is also a default security against other common vulnerabilities.
The authentication form using spring security provide high security against common vulnerabilities :

The SecurityConfig will:

Require authentication to every URL in your application

Generate a login form for you

Allow the user with the Username user and the Password password to authenticate with form based authentication

Allow the user to logout

CSRF attack prevention

Session Fixation protection

Security Header integration

HTTP Strict Transport Security for secure requests

X-Content-Type-Options integration

Cache Control (can be overridden later by your application to allow caching of your static resources)

X-XSS-Protection integration

X-Frame-Options integration to help prevent Clickjacking

Integrate with the following Servlet API methods




HttpServletRequest.html#login(java.lang.String, java.lang.String)


What is the difference between XSS and CSRF vulnerabilities ?

To sum up ,the vulnerability CSRF allows an attacker to use existing functionalities of a web application. In a bank application , an attacker could force a customer to use the existing feature of transferring money to “attacker’s account”.

In other hand XSS vulnerability allow an attacker to “create new functionalities” on the website using Javascript code :

  • Deface the website
  • Send cookies information to an attacker’s website

  • More detailed explanation of the differences :

    Fundamental difference is that CSRF (Cross-site Request forgery) happens in authenticated sessions when the server trusts the user/browser, while XSS (Cross-Site scripting) doesn’t need an authenticated session and can be exploited when the vulnerable website doesn’t do the basics of validating or escaping input.

    Owasp made a top-10 of the most common vulnerabilities in web applications.This classification did not change from 2013 to 2017.

  • XSS corresponds to A3 – Cross-site scripting
  • CSRF corresponds to A8- Cross-site request forgery

    CSRF prevention

    Basically one solution against this attack is to append a unique identifier to the POST form and let the server verify the identifier. POST form request is usually used to modify data. That’s usually what attacker will try to use when exploiting CSRF vulnerability. GET requests are normally used to retrieve information.

    In Java the framework Spring Security used an unique identifier as anti CSRF technique :

    How to test for CSRF vulnerability ?

    XSS types

    XSS happens when we don’t escape characters and validate input .Typically this vulnerability allows an attacker to send input with the intention to retrieve sensitive information(for example cookie) from the website.

    There are different types of XSS attacks :

  • Stored XSS attacks
  • Reflected XSS attack
  • Stored XSS attacks

    This is the worse XSS vulnerability to have on one website. Indeed if the malicious javascript code is stored in the database, potentially this malicious code could be executed in different webpages of the website.

    Reflected XSS attack

    It is very similar to a stored XSS attack except the malicious code is not stored. The malicious code can be executed on the web browser.

    How to test for XSS vulnerability ?

    Test Reflected XSS attack
    In the following example i have added some Javascript code into the input “info”.If the cookie is written back to the screen , this website is sensitive to XSS attack :<script>alert(document.cookie)</script>

    Test Stored XSS attack
    This webpage explained how to test a website for stored XSS vulnerability.

    XSS prevention

    Basically input should be checked for special characters. Input should be validated and verified.

  • One solution is to use Regex to escape characters.
  • Another solution is to use existing libraries to avoid XSS. In Java ESAPI seems like a robust library :
  • How to avoid XSS and allow HTML tags with javascript :

    Detailed XSS Explanation

    There are many websites explaining in details XSS attacks. This one explained in details the scenarios of attacks :

    This other website gives an overview of the difference between the XSS types

    Framework Gwt offers some protection

    On one application ,the scanner Zap Proxy did not found any of these vulnerabilities(XSS-CSRF). This webapp used the framework Gwt. By default it has limited protection against these vulnerabilities. But it is possible to test Gwt more in depth for vulnerabilities with this tool :

    How to verify your java libraries have known security vulnerabilities ?

    A maven plugin can check you Java libaries for known vulnerabilities. It is called dependency-check-maven.

    The OWASP Dependency Check utility uses NIST’s National Vulnerability Database (NVD) to identify the vulnerable dependencies, so the list is always up-to-date.



    You will need the following to use Owasp Maven dependency Check.

  • Maven version superior to 3.1
  • Tips to quickly check only some libraires

    Let’s say you can not compile all the project because some jars/files are missing. Then you cannot use the plugin immediately. You need to compile the project first. If you don’t need to compile the project entirely, you can just create a simple pom with all dependencies to check.

    Example :

    <?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="" xmlns:xsi="" xsi:schemaLocation="">

    Check maven dependencies with this command :

    mvn dependency-check:check


    Check the link above to use reporting for your continuous integration. Otherwise here is an example of reporting once you launch the maven plugin :

    One or more dependencies were identified with known vulnerabilities in my_project:
    logback-core-1.1.3.jar (ch.qos.logback:logback-core:1.1.3, cpe:/a:logback:logback:1.1.3) : CVE-2017-5929
    commons-collections-3.2.1.jar (commons-collections:commons-collections:3.2.1, cpe:/a:apache:commons_collections:3.2.1) : CVE-2015-6420


    If you have the following error

    -Dmaven.multiModuleProjectDirectory system property is not set

    then you need to modify the java configuration like this in eclipse :owasp_check_maven

    Basics IBM Websphere MQ Series

    This article introduced a simple MQ Server composed of a queue manager, local queues, channels. Channels allow the queues to communicate between each other. Aliases can also be used to give an alias to queues.

    Create a queue manager

    Queue managers are the main components in a WebSphere MQ messaging network.

    Display queue managers before


    If the queue manager does not already exist create a queue manager

    crtmqm QM1

    Start the queue manager

    strmqm QM1

    This command will modify the queue manager. For example here channel authentication are not recorded :


    Create a channel

    Definition of a channel

    WebSphere MQ uses two different types of channels:

  • A message channel, which is a unidirectional communications link between two queue managers.
  • An MQI channel, which is bidirectional and connects an application (MQI client) to a queue manager on a server machine.

    How to create a Channel ?

    In our app we use a “receiver channel”

    A receiver channel is a message channel that the queue manager uses to receive messages from other queue managers.

    Verify existence of channel

    dspmqfls -m QM1 -t CHAN_RCV

    Create a receiver channel

     runmqsc QM1  <<e@

    Also we use “Sender channel”

    A sender channel is a message channel that the queue manager uses to send messages to other queue managers.

    Create a receiver channel

     runmqsc QM1  <<e@

    What is a purpose of a transmission queue ?

    We need this queue to send a message to another queue.

    Create a transmission queue :

    runmqsc QM1 <<e@

    Create a local queue/in for the reception of message

    runmqsc QM1 <<e@

    Create a corresponding alias of the queue. It is a link to the queue.


    Create a local queue/out to send messages

    It is the same thing as for the reception of the message. Only the name of the queue is different.

    What is the difference between queue and channel in MQ ?

    For IBM MQ one endpoint is always the queue manager (a type of messaging engine) and the other is an application or another queue manager.

    Based on this example, it should be obvious that channel as used in the book and channel as defined by any messaging transport are at different levels of abstraction. As used by MQ, a channel is a specific set of configuration parameters that define a communication path and includes such attributes as CONNAME, MAXMSGL, tuning parameters, SSL parameters,

    Once an MQ channel is successfully started, you can see a running instance of it by displaying the channel status. In the case of CLUSRCVR, SVRCONN, and (less commonly) RCVR or RQSTR channels, you may see multiple instances of the same channel active simultaneously.

    How to connect to a queue manager in MQ ?

    I actually use the mqexplorer(mqj.cmd) from Windows. The project is opensource at .

    Run the program MQ explorer and from “Show Queue Manager” choose a remote queue for distant server MQ.

    show_queue_manager - Copy


    If there is an error in mqjexplorer(example with MQRC_Q_MGR_NOT_AVAILABLE) , verify that queue is started:

    strmqm QM1

    If it is OK then verify that the listener is started :

    runmqlsr -m QM1 -t TCP -p PORT_MQ &

    Normally it fixes the issue of queue manager not being accessible from mqexplorer.

    How to simulate a MQ server ?

    The problem

    Our application is retrieving information from a distant server using IBM Websphere Mq messaging system. In production we need to install two MQ servers , one on machine A and another one on machine B:

    Creation Fil MQ

    We want to avoid installing MQ Server on two machines for the qualification platform. How to simulate machine B ‘s MQ Server ?

    The solution

    This article will explain several steps taken to simulate the communication between two MQ servers. These are the steps explained :

  • Create a MQ server on machine A
  • Run a Java application on machine B within tomcat which listens to inqueue QueueManager and send back information to Outqueue MQ queue manager
  • Create a MQ server on machine A

    A IBM MQ server is composed of a queue manager, local queues, channels. Channels allow the queues to communicate between each other. Aliases can also be used to give an alias to queues.

    Simulate a MQ server on machine B

    First of all install tomcat on the machine B. The solution is using Java to catch JMS information from our MQ Server on machine A. To simulate the MQ Server these are the steps :

  • Add a listener in web.xml
  • The Java class listener will be launched at tomcat startup.
  • At statup , the listener starts one Thread or multiple ones to listen one or multiples queue managers
  • Let’s assume we have one thread listening to one Queue manager
  • When a Thread is cathing a JMS message, from receiver/in queue of machine A, it will parse the message
  • Based on the parsed message we check a database or filesystem for a DataSet response
  • Finally we send the dataset response to the Out/sender queue of machine A
  • The application in machine A reads the out/sender queue and process it like normal not knowing it is consuming messages from the simulator
  • That’s it : the machine B simulated a MQ Server
  • Add a listener to tomcat web.xml


    At startup of tomcat the MQlistener will be launched. The thread is started within the listener like this :

    final MqThread mq= new MqThread (mqinfo);
    MqThread .start();

    Read MQ configuration detailed from a file

    We need to know to which receiver/in queue we will listen to and which sender/out queue we will send message to.

    Example of properties file containing these information :

    hostname	  = myserver
    port		  = 9999
    queueManager = MYQUEUEMANAGER	  = QUEUE.OUT
    queue.out	  = QUEUE.IN

    “” represents the queue we are lestening to. “queue.out” is the queue we are going to send message to.

    Start a thread listening to a receiver queue

    The MqThread extends Thread class. It contains a run() method which will be executed when the thread is started.

    The MqThread constructor prepares an active connection with the queue manager and the queue receiver and sender in order to communicate with the MQ server .

    import javax.jms.QueueConnection;
    public MqThread (MqInfo mqInfo) throws JMSException {
    final MQQueueConnectionFactory queueConnectionFactory = new MQQueueConnectionFactory();
          queueConnection = queueConnectionFactory.createQueueConnection(mqInfo.user, mqInfo.password);
          // A QueueConnection object is
          // an active connection to a point-to-point JMS provider.
          this.queueSession = queueConnection.createQueueSession(false, Session.AUTO_ACKNOWLEDGE);
          // A QueueConnection can be used 
          // to create a QueueSession, 
          // from which specialized 
          // queue-related objects can be created
          this.receiver = session.createReceiver(mqInfo.receiverQueue);
          // Creates a QueueReceiver object to receive 
          // messages from the specified queue.
          this.sender = session.createSender(mqInfo.senderQueue);
          // Creates a QueueSender object to send 
          // messages to the specified queue.

    More information about QueueConnection

    The thread will be listening to MQ receiver queue. When a JMS message is sent to that queue the thread will consume and parse the message.

    public run() {
    		this.queueManager = queueManager;
                    while (isThreadTerminated) {
    		    final Message message = receiver.receive(1000);
    		    proccessMessage(message );

    The run() method is listening to queue receiver to handle messages from this queue.

    Receives the next message that arrives within the specified timeout interval.

    Based on the parsed message we check a database or filesystem for a DataSet response

    Once the message is parsed we can retrieve a DataSet response from a file system. This example is not complet but give an idea what to do :

    	private String getDataSetResponse(String inputMessage) {
    		final String filename = getFileNameDataSet(inputMessage);
    		return getFile(filename );

    Finally we send the dataset to the Out/sender queue of machine A

    private void sendMessage(String message, String messageId) throws JMSException {
           final TextMessage dataSetMessage = session.createTextMessage(message);
           sender.send(dataSetMessage );

    That ‘s it

    How to apply CSS specific on several tables ?


    Our website did not look nice because of a CSS problem.
    Indeed some data on one row of a table was scrollable.
    The data of one row would overflow.

    How to stop this data to be scrollable on one line ?
    The goal was to present the information in several lines instead of one line. The solution to this first problem was to modify the table-layout for the CSS element table to “fixed” property.

    table {
        border-collapse: collapse;
        clear: both;
        margin-left: auto;
        margin-right: auto;
        width: 98%;
        table-layout: fixed;

    Unfortunalely because of this global modification of CSS another problem popped up in a diffrent webpage :


    The solution for this second problem was to make the CSS table tag to this configuration :

    table-layout: auto

    Auto layout is the default property for most of the tables of my website in CSS.The auto property adapts the table layout to all different browers which is practical. But how can we apply specific CSS properties to specific tables ?

    This link help me to apply specific CSS to one specific table using id :


    This is the html page where we had a scrollable/overflow initial problem :

    <table id="my_tableA_X" class="result ">
    <table id="my_tableA_Y" class="result ">
    <table id="my_tableA_Z" class="result ">

    my_tableA_Y is having the scrollable/overflow problem. But I want also all other tables (starting with my_tableA) to have a similar look. Therefore i  will  apply the same CSS properties to all tables with id starting  by “my_tableA”. Regex is used to achieve this inside CSS file :

    The solution to the two problems :

        border-collapse: collapse;
        clear: both;
        margin-left: auto;
        margin-right: auto;
        margin-bottom: 5px;
        margin-top: 5px;
        width: 98%;    
        table-layout: fixed;
    table {
        border-collapse: collapse;
        clear: both;
        margin-left: auto;
        margin-right: auto;
        width: 98%;
        table-layout: auto;

    Now all table which start with an id my_tableA have the same layout and columns have same size , width, etc… This solution fixed the problem. The second table CSS tag indicates that other tables will have auto layout.