SQL Injection (SQLi) is a type of security attack that allows an attacker to manipulate SQL queries in a web application and gain unauthorized access to data. This attack exploits vulnerabilities in the handling of user inputs, where unverified or improperly processed inputs can be inserted into SQL queries. Consequences can include the theft of sensitive data, destruction of data, or gaining unauthorized access to the entire database.
How SQL Injection Works
SQL Injection attacks start where the application accepts user input and passes it into an SQL query without proper validation or escaping of special characters. Attackers can insert malicious code into these inputs, which alters the original logic of the SQL query. A typical example is inserting the condition OR '1'='1', which is always true and can lead to the disclosure of an entire table.
Types of SQL Injection
- Unbound SQL Injection: This type of attack utilizes the incorrect concatenation of user inputs with an SQL query. The attacker directly modifies the SQL query by inserting malicious code.
- Blind SQL Injection: Here, the attacker does not need to see the data from the database but deduces information from the application's response to various modified queries.
- Time-based Blind SQL Injection: The attacker observes how long it takes the database to execute a query and infers the structure of the database or the content of the data from this.
Preventing SQL Injection
To protect an application from SQL Injection, it is important to follow these practices:
- Use Parameterized Queries: These queries separate SQL code from user data and prevent the insertion of malicious code into the query.
- Escape Special Characters: When using parameterized queries is impractical, the application should escape special characters that could alter the SQL query.
- Limit Permissions: User accounts working with the database should have the minimum necessary permissions. If an attacker breaches the defense, limiting permissions can prevent further damage.
- Validate and Sanitize Inputs: All user inputs should be thoroughly validated and sanitized to prevent undesirable manipulations of data.
SQL Injection is one of the most serious security risks for web applications. Effective protection requires a comprehensive approach, including technical measures and regular security audits. Proper deployment of security practices and continuous education of developers can significantly reduce the risk of a successful SQL Injection attack.
