SQL injection is a web security vulnerability that occurs when an attacker inserts malicious SQL (Structured Query Language) statements into a web application's database query. It takes advantage of a lack of proper input validation or sanitization of user-supplied data.
Web applications often use SQL databases to store and retrieve data. SQL injection occurs when an attacker is able to manipulate the SQL queries executed by the application. This can lead to unauthorized access, data manipulation, or even complete control over the database.
Here's an example to illustrate how SQL injection works:
Let's say there's a login form on a website that accepts a username and password. The application uses the following SQL query to check the credentials and authenticate the user:
```
SELECT * FROM users WHERE username = 'input_username' AND password = 'input_password';
```
In this example, 'input_username' and 'input_password' are the variables that should contain the user-supplied values. However, if the application does not properly validate or sanitize these values, an attacker can manipulate them. They could input something like:
```
input_username: ' OR '1'='1
input_password: ' OR '1'='1
```
Now, the manipulated SQL query becomes:
```
SELECT * FROM users WHERE username = '' OR '1'='1' AND password = '' OR '1'='1';
```
Since '1' always equals '1', this query will return all the rows from the "users" table, effectively bypassing the authentication process.
The consequences of a successful SQL injection attack can be severe. Attackers can extract sensitive information from databases, modify or delete data, gain unauthorized access to administrative functionalities, and even take control of the entire system.
Preventing SQL injection involves implementing proper input validation and parameterized queries or prepared statements. By using parameterized queries, user input is treated as data rather than executable SQL code, significantly reducing the risk of injection attacks. Regular security testing, keeping software up to date, and following secure coding practices are essential in mitigating SQL injection vulnerabilities.
