![]() ![]() The ( #) used here is to comment out the rest of the backend query. Using id= ' order by 3 # application throws the MySQL error and tells that the 3 rd column is not used in the query. In this way, our work to guess number of columns become easy with ORDER BY. So the deduction would be when I used ORDER BY with 2 I didn't get any error but when I used with 3 I got the above error, so the number of columns used in the backend query is 2. So query will execute only when it will be sorted according to the columns used in the query.īut If I want to sort the results by column 3 (which is not used in the query) MySQL will generate the error saying:ĮRROR 1054 (42S22): Unknown column '3' in 'order clause' Like the query above uses 2 columns, using ORDER BY the result can be sorted according to column 1 (first_name) or according to column 2(last _name). ORDER BY sorts the results according the the columns. We'll need proper enumeration of the backend query for which MySQL helps us. MySQL> select first_name, last_name from users where user_id=1 īut it is just a wild guess. Our guess about the backend query from the front end is something like: Let's dig further and try to enumerate to try to guess the backend query, number of columns used in the query, database name, MySQL version etc. Take:MySQL helps to explore the SQL injection further. So, the injection point is identified as the USERID field and it is possible to communicate to the backend SQL server from the front end which will make the SQL injection possible.Ģ. MySQL> select first_name, last_name from users where user_id=' '' Īnd hence, it creates a syntax error. If provided input is the quote ( ') the SQL query breaks and becomes: MySQL> select first_name, last_name from users where user_id=' ' If I try to imagine the query at the backend it would be something like: The reason is the backend SQL query causes a syntax error when supplied a ( ') instead of integer. If you will see the error closely it is a syntax error. We can see that the database error is generated which confirms that the application is vomiting database errors also, the database in use is MySQL. It takes an integer as input and displays the First Name and Surname associated with the User ID provided. Like in the screenshot shown below, the USER ID field could be vulnerable to SQL injection. ![]() ![]() By analyzing the application properly,the possible injection points can be identified. Identifying the SQL injection is the key step, and it takes a lot of skill and experience to identify the injection point. It is easy to install and configure DVWA and for the demo I have kept the script security as "low". The concept behind the attack is the same in both the scenarios but there is a slight difference in exploitation that we will discuss later. I will be using two scenarios where DVWA is installed on Linux OS and another in Windows OS. It is a good tool for web application security enthusiasts to begin with. DVWA is PHPMySQLApache application and purposefully made vulnerable. It is easy to install and can be downloaded from. Keep in mind this is a staged payload.For the demo I am using Damn Vulnerable Web Application (DVWA). This is a module from Rapid7 that should be used with their handler but you don't have to. This will work with any operating system on a server. I'm writing this on my phone and is a bit difficult to structure the text. Ask me if there is something that you dont understand. ![]() So if that other server (remote url) executes that php( you upload the file and open the url), you would need a public IP, because that server is on the internet and cannot find your physical ip. The file needs to be executed from the server that you want to conect to, so that the php in that system executes the bash command. So the php is being executed in your server, not in another site. If your ip is in the same network as the server, (or your routing table is configured to forward to another network) the server tries to make the connection serverip->yourcomputerip:8080 So when you execute the php script, it runs on the server that hosts the file (localhost) and tries to connect to the desired ip. So ngrok makes a localhost port public, like localhost:3000->, so at this point you have something like a public subdomain and a public ip that forwards the connections to your localhost. ![]()
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