Skip to main content

SQL Injection in search field

Earlier I had written about performing SQL injection in search field and how to do a DoS attack and privilege escalation using 'Like' operators. Now another SQLi exploitation I came across recently. That too in the search field. This becomes important as lots of people don't pay much attention on the search forms/ fields in the application. My aim is to show that a search form can also be exploited with SQL Injection. The following queries are based on a real world exploitation. The steps and data are for just illustration purpose only.
Suppose, the search form provides the details of users who have accessed the application some time and their login time details etc, we just need to provide their name in the search box provided. All the data were being going as Post request.
So, to just fingerprint the database, I provide, 'nil'+'esh' in the search field and it successfully gives me the results. That means the database behind the application is concatenating the name and made it a single string as 'nilesh'. This behavior shows it's a MS SQL server behind the scene. However,that also gets confirmed when the application straightaway throws an error about MS SQL server. But the above trick is another way of knowing about the database. For example: 'nil'| |'esh' could be Oracle and 'nil' 'esh' could be MySQL.

Now, next step is to extract some more information from the database, and Union query is a great way of doing that.
I supply, nilesh' UNION SELECT NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL-- which gives me no. of exact columns. As we can see, the no. of NULLs above is 8 so the table has 8 nos of columns. Anything less than 8 don't produce any error and anything above than 8 produces error. So, that way we can determine that the no. of columns are 8. Another way of doing that is executing ' ORDER BY query. Start by 'ORDER BY 1 till you get error and the no. before you get error is no. of the columns. So, supplying 'ORDER BY 9 gave error, so the no. is 8.

Next step is to know the datatype of the columns. The query ' UNION SELECT 'a',NULL,NULL,NULL,NULL,NULL,NULL,NULL--  which gives me error as 'conversion failed....data type int' so the first column is int. Similarly we can keep trying to replace each NULL in above query to know the datatypes of each column. Another example, ' UNION SELECT NULL,'a',NULL,NULL,NULL,NULL,NULL,NULL--  doesn't produce any error, so string datatype, so- forth, so-on.

Now more queries can be executed:
' UNION SELECT @@version,NULL,NULL,NULL,NULL,NULL,NULL,NULL--                /*version info*/

' UNION SELECT NULL,name,NULL,NULL,NULL,NULL,NULL,NULL from sysobjects where xtype='U'--                                                                            /*To retrieve only the user-defined objects*/
It gives the names of tables in database. One of them was, let's say, 'UserTable'. Now in order to see retrieve names of columns in the table, we run the following query:
' UNION SELECT NULL,b.name,NULL,NULL,NULL,NULL,NULL,NULL from sysobjects a,syscolumns b where a.id=b.id and a.name='UserTable'--     /*To discover the names of columns within the  table*/

Now when we have all in hand, we can run the following query to extract data from 'UserTable':
' UNION select ,.....from UserTable--
and that gives us the entire data from that table. That could be username and passwords also depending on the scenarios.




Comments

Vezance Xocobs said…
Good post. My blog once got hacked by SQL injection. I was flabbergasted at that time. My jaw almost dropped when I realized such a thing was even possible. This article went a long way in explaining how it could have happened.
rajani kota said…
Thanks for posting such a Useful information .
DevOps Training
DevOps Online Training

Popular posts from this blog

Ardilla- New tool for finding SQL Injection and XSS

Three Researchers -- MIT's Adam Kiezun , Stanford's Philip Guo , and Syracuse University's Karthick Jayaraman -- has developed a new tool ' Ardilla ' that automatically finds and exploits SQL injection and cross-site scripting vulnerabilities in Web applications. It creates inputs that pinpoint bugs in Web applications and then generates SQL injection and XSS attacks. But for now Ardilla is for PHP -based Web app only. The researchers say Ardilla found 68 never-before found vulnerabilities in five different PHP applications using the tool -- 23 SQL injection and 45 XSS flaws. More information is awaited. For their attack generation techniques refer to their document at: http://www.cs.washington.edu/homes/mernst/pubs/create-attacks-tr054.pdf

Combining power of Fiddler with Burp

Both are pretty powerful tools when it comes to intercept and modify http communications. But at some point of time, they become even more powerful combo if tied with each other. They complement each other. In a recent pentest I came across a similar situation where in Burp was not able to intercept a specific kind of traffic and Fiddler came to rescue. The application was designed to upload video. The initial communication was straight forward, I mean logging into application, filling up the video details etc. And all these were easily captured by Burp except the point where you hit the Upload Video and it connects to a different server and surprisingly it was not captured by Burp, not sure why, even after repeated attempts. So, I fired Fiddler to see if the it sees this request. But it's a;ways to play with requests using Burp due to it's various functionalities like, Intruder, Repeaters etc. But it was necessary to capture this request in Burp. So the below steps can be

File Upload through Null Byte Injection

Sometimes, during file upload we come across situation wherein there would be check on the file extension at the client side as well as server side too. If the application does allow only .jpeg extension to be uploaded, the client side java script checks for the extension of the file before passing the request. We all know that how easily this can be defeated. Some applications, checks for the extension at the server side also. That's not easy to bypass. However there are some ways with which it still can be bypassed. Most of server side scripts are written in high level languages such as Php, Java etc who still use some C/C++ libraries to read the file name and contents. That leads to the problem. In C/C++ a line ends with /00 or which is called Null Byte. So whenever the interpreter sees a null byte at the end of the a string, it stops reading thinking it has reached at the end of the string. This can be used for the bypass. It works for many servers, specially php servers. T