Introduction to SQL Injection
SQL Injection is a code injection technique used to attack data-driven applications by inserting malicious SQL statements into the execution field. The database is a vital part of any organization. This is handled by high-level security in an organization. Let us first learn what SQL is. SQL is a structured query language. Used to interact and to manipulate the database.
What SQL does exactly?
- Create a new database.
- Insert, update, delete records.
- Create new queries.
- Stored procedures.
- Create views.
- Execute queries.
- Set permissions.
It is one of the top security threats. This comes under cybercrime.
In SQL, we have a concept called SQL Injection. This technique is used to inject the code. SQLi (It is also known as a type of hacking, i.e., injection attack.) It is also known as the web hacking technique.
This injection injects malicious code into the database by giving input to a web page. These inputs have some conditi0ons, which are always true. With these conditions, hackers easily pass security tests. They can easily get data from the SQL database. With SQL Injection, they can add, modify, and delete records in the database. That database may be anyone among MySQL, SQL Server, Oracle, SQL Server, etc., is illegal.
If a website or an application is poorly designed, then these attacks may harm the entire system. So at this point, cybersecurity comes into the picture.
The behavior of SQL Injection
These attacks generally work on dynamic SQL statements. It is database engine-dependent. This differs from engine to engine. When we ask for input to the user on the webpage like username and password. Unintentionally we are giving the user access to give that input directly into the database.
Types of SQL Injection
Different types are mentioned below:
- In-band SQL injection (Classic SQL injection): In this technique, the hacker uses the same way to hack the database and get the data, i.e., result from the database.
- Error-based SQL injection: In this type, the hacker gets the error pattern of the database and access it. We can say this is the one type of in-band SQL injection.
- Union-based SQL injection: This technique is also a part of in-band SQL injection. The user combines the query and gets the result back as part of the HTTP response in this technique.
- Inferential SQL injection (Blind SQL injection): As the name suggests, here hacker does not use the band to get data from the database. Hacker has the capability to change the structure of the database by observing patterns of the database. This is a very dangerous type of SQL injection. This attack takes a long time to execute. Hacker is not able to see the output of the attack by this technique.
- Boolean-based (content-based) Blind SQL injection: This is a part of Inferential SQL injection. In this technique hacker forces the database to fetch results based on true or false conditions. Depending upon this condition result of the HTTP response gets changed. This kind of attack can infer if the payload used returned true or false, even though no data from the database is returned. These are especially slow attacks.
- Time-based Blind SQL injection: This technique is also part of Inferential SQL injection. Hackers use this technique to put the payloads in this technique, hackers giving time to the database to execute the query. Meantime hacker gets an idea about the result, whether it is true or false. This process of attack is also slow in nature.
- Out-of-band SQL injection: This is a feature-based attack. This is not very common. A hacker uses this attack when a hacker needs to use different channels to attack and others to get the result. Out-of-band SQL injection techniques are dependent on the database server’s ability to make DNS or HTTP requests to deliver data to the hacker.
How does it Work?
There are mainly two ways where the attacker focuses on getting data:
- Direct Attack: Directly using the combination of different values. Here hacker put the confirmed input, which gives the exact result.
- Research: Analyzing the database by giving different inputs. Here, the attacker observes the database server responses and decides which attack has to be done.
As we already discussed, SQL injection hackers put the condition in the input element, which is always true. Please check the following example.
Suppose we have the below query to get employee data from the database:
Select * from employees Where Userid = ‘500.’
Suppose we do not have any restriction on the user’s input. Then hackers may use this field to access data from the database easily.
And the query may look like below.
Select * from employees where User-id = 500 OR 1=1;
This query will return data from the database because 1=1 will always return true. In this way condition becomes true. This seems vulnerable. This is very dangerous to the organization. For instance, think about the banking sector. Where users have their net banking details, passwords, balance information, etc.
This technique is very easy for the hacker to get information by simply giving some input to the database.
Hackers get data by simply inserting OR and = by inserting it into the database.
” or “”=”
” or “”=”
At the server, the end query gets executed correctly; no error occurs. Also, you may use ‘ OR ‘1’=’1 to get data from the database server.
Now, the question arises, how would we maintain our database security?
And the answer is by using SQL parameters.
By adding extra parameters at the query when it executes. These attacks are easily preventable by some below techniques.
Stored procedures, prepared statements, Regular expressions, Database connection user access rights, Error messages, etc., are the prevention techniques.
One more thing that we should think, it is also sensible to have different databases for different purposes in the application.
One more thing that comes across is testing. Testing the database for a different condition is also the best way.
Creating a database is a crucial part. Having the risk of getting information in hackers’ hands is not good for any application. So, while creating the database, we must follow some easy steps to prevent this loss; a phrase suitable for this is ”Prevention is better than cure.”
This has been a guide to What is SQL Injection. Here we discuss the Behaviour, How does it work, and the respective types. You can also go through our other suggested articles to learn more –