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lionaneesh 8Jul2011 00:20

Understanding Basic SQL Injection
 
SQL injection (also known as SQLI) is a code injection technique that occurs if the user-defined input data is not correctly filtered or sanitized of the ‘string literal escape characters’ embedded in SQL.

Basically SQLI is a way of injecting and executing arbitrary SQL statements. The whole idea is to make the application execute our arbitrary code which was not intended. In this tutorial we’ll be looking on how a basic SQL code injection can cause the application to mess up its authentication login and which would eventually lead to data access. So what’s the waiting then let’s get started.

Authentication Bypass (SQL injection)



Most of the authentication scripts you’ll find on the web are not secured and despite this vulnerability first appeared in 1990’s :snore: there are still many applications vulnerable to this attack.

How SQL injection works?

This attack simply exploits bad filtering or sanitizing mechanism in the database layer of an application, this vulnerability gives the room to attackers to basically alter arbitrary SQL code to be executed.

For example you have a basic SQL statement as follows:-
Code:

  SELECT * FROM Users where Name = ‘UserInput’;
Now if the page is vulnerable to this kind of attacks then an attacker have the room to alter anything to this SQL statement.
For Example the attacker can simple add
Code:

  ‘ or ‘1’ = ‘1
Which would result in :-
Code:

  SELECT * FROM Users where Name =  ‘’ or ‘1’ = ‘1’
Now if you know some basic SQL you can simply point out that this means that now the application will be forced to get all the users in the table as the statement now includes a or condition i.e ‘1’ = ‘1’ which in any case will always be true.

Demonstration



To demonstrate a basic SQL authentication bypass attack I have created a set of some php scripts.

defines.php
Code:

  <?php
  $tableName = "badlogin";
  $dbName              = "sqlnjection";
  $sqlServer = "localhost";
  $sqlUser = "root";
  $sqlPass = "";
  ?>

functions.php
Code:

  <?php
require "defines.php";

function checkTable()
{
        global $tableName;
        $query = "SELECT * from $tableName";
        $result = mysql_query($query) or die(mysql_error());
        if($result == FALSE) // Table is not created till
        createTable();
}
function createTable()
{
        global $tableName;
        $query = "CREATE TABLE $tableName(login char(50),pass char(50))";
        $result = mysql_query($query);
        $query = "INSERT INTO $tableName(login,pass) values('admin','UnCrACkAbLe')";
        $result = mysql_query($query);
}
function checkCredentials($login,$pass)
{
        global $tableName;
        $query = "SELECT * FROM $tableName WHERE login='$login' AND pass='$pass';";
        //            echo "<br/>$query<br/>";
        $result = mysql_query($query) or die(mysql_error());
        $rowsnum = mysql_num_rows($result);
        if($rowsnum > 0)
        {
                congrats();
        }
}
function congrats()
{
        echo"<p class='warning'>Congratulations You just completed the Challenge...</p>";
        echo"<script type='text/javascript'>alert('Mission Completed');</script>";
        // The redirection and Points award code should go here
}
?>

sqlInjection.php
Code:

<?php
require "defines.php";
require "functions.php";
?>
<html>
<head>
        <title>Bad Login</title>
        <link href='style.css' type='text/css' rel='stylesheet'/>
</head>
<body>
        <h1>Welcome to bad Login Please Enter your Credentals</h1>
        <form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
        <table align="center" class="login">
                <tr>
                        <td>Login</td>
                        <td> : <input type="text" name="login"/></td>
                </tr>
                <tr>
                        <td>Password</td>
                        <td> : <input type="text" name="email"/></td>
                </tr>       
                <tr>
                        <td><input type="submit" name="go"/></td>
                </tr>
        </table>
        </form>
<?php 
if( isset($_POST['login']) && isset($_POST['email']) &&        isset($_POST['go']) )
{
        mysql_connect("$sqlServer","$sqlUser","$sqlPass") or mysql_error();
        mysql_select_db("$dbName") or mysql_error();
        //checking if table exists
        checkTable(); // checks if the table exists and create new if not found
        checkCredentials($_POST['login'],$_POST['email']);
}
?>

</body>
</html>

Constructing the Attack String :-

Our main purpose for this scenario is to check is to exploit the vulnerability in the above set of pages and gain access to ‘admin’ account , We can simply do that by the following ways :-
  1. Giving “admin'#” as a username to the application , This means that after writing admin as a username we used ‘#’ to comment any other code after that.
  2. Giving “admin” as username and “ ‘ or ‘1’ = ‘1 “ as password. This would trick the application to use an ‘or always true’ condition which would eventually result in authentication bypass.
That’s all for this tutorial , Stay tuned for more

alssadi 14Jul2011 01:36

Re: Understanding Basic SQL Injection
 
incredible post love it , and very helpful

lionaneesh 14Jul2011 18:16

Re: Understanding Basic SQL Injection
 
Quote:

Originally Posted by alssadi (Post 84980)
incredible post love it , and very helpful

My Pleasure.

Mr.sp41t3r 23Jul2011 23:51

Re: Understanding Basic SQL Injection
 
Thanks You :)

lionaneesh 24Jul2011 13:00

Re: Understanding Basic SQL Injection
 
Quote:

Originally Posted by Mr.sp41t3r (Post 85359)
Thanks You :)

Welcome! :D

Scripting 26Jul2011 13:47

Re: Understanding Basic SQL Injection
 
Really good, but It might be more advanced :)

lionaneesh 26Jul2011 17:52

Re: Understanding Basic SQL Injection
 
Quote:

Originally Posted by Scripting (Post 85422)
Really good, but It might be more advanced :)

MY Please , and the coming articles will be more advanced for sure.

Eldadmika 23Aug2011 18:10

Re: Understanding Basic SQL Injection
 
tanx. and i need more explanation on sql..

JohnAadam 26Oct2011 05:56

Re: Understanding Basic SQL Injection
 
can you suggest what should i choose to do sql injection whether to do it manual or to do it with tools like havij 1.15 .:crazy::confused:

lionaneesh 26Oct2011 08:17

Re: Understanding Basic SQL Injection
 
Quote:

Originally Posted by JohnAadam (Post 88475)
can you suggest what should i choose to do sql injection whether to do it manual or to do it with tools like havij 1.15 .:crazy::confused:

Tools like Havij , SQLMAP always fail for advanced SQL injections which you'll mostly find on Real World Websites , Using tools like these may allow you to exploit basic and easy SQL injections but often these type of tools misses a lot of them! So i suggest you to stick with manual SQLI testing , and if you are scanning a whole subnet of servers i suggest you to edit some scripts yourself. :)

icecube_media 28Oct2011 12:24

Re: Understanding Basic SQL Injection
 
this is some nice information but what if admin page is not accessible of a website ??

JohnAadam 28Oct2011 21:51

Re: Understanding Basic SQL Injection
 
Haa ... the same condition happen with me .

I got admin username and password but could not found the log in page . :crazy:

That was a freeky think i tried a lot of think but failed :wacky:

lionaneesh 28Oct2011 21:55

Re: Understanding Basic SQL Injection
 
Quote:

Originally Posted by icecube_media (Post 88559)
this is some nice information but what if admin page is not accessible of a website ??

Quote:

Originally Posted by JohnAadam (Post 88581)
Haa ... the same condition happen with me .

I got admin username and password but could not found the log in page . :crazy:

That was a freeky think i tried a lot of think but failed :wacky:

There are many possible ways of finding a admin panel , I'll write a tutorial on it if possible.

JohnAadam 28Oct2011 22:00

Re: Understanding Basic SQL Injection
 
Can you give the link if possible . But i have tried it in Havij were 400 admin log in pages were tested.

lionaneesh 28Oct2011 22:01

Re: Understanding Basic SQL Injection
 
Quote:

Originally Posted by JohnAadam (Post 88583)
Can you give the link if possible . But i have tried it in Havij were 400 admin log in pages were tested.

Havij is Just a Automated tool! Finding admin pages , Just dont rely on that! There are several factors which involve a number of steps!

JohnAadam 28Oct2011 22:19

Re: Understanding Basic SQL Injection
 
OK i take your advice ... can you post the link....
Please accept me on gtalk . I had send u an invitation.

lionaneesh 28Oct2011 22:40

Re: Understanding Basic SQL Injection
 
Quote:

Originally Posted by JohnAadam (Post 88586)
OK i take your advice ... can you post the link....
Please accept me on gtalk . I had send u an invitation.

I accepted u on GTALK , I'll get back to u as i have got some time to spare! :) Thanks


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