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A Beginner's Guide to SQL Injection for Students

SQL Injection is a common hacking technique that targets vulnerabilities in a web application's database layer...

What is SQL Injection?

SQL Injection (SQLi) occurs when an attacker inputs malicious SQL code into a form field...

  SELECT * FROM users WHERE username = 'user' AND password = 'pass';
                                

If the application doesn't properly validate or sanitize the input...

  SELECT * FROM users WHERE username = '' OR '1'='1' AND password = 'pass';
                                

Types of SQL Injection

• Classic SQL Injection: Directly injecting malicious SQL...
• Blind SQL Injection: The attacker doesn't see the query results...
• Time-Based SQL Injection: The attacker uses delays...
• Out-of-Band SQL Injection: The attacker uses external channels...
• Union-Based SQL Injection: The attacker uses the UNION operator...

How to Test for SQL Injection

To understand SQL Injection, you can practice on a safe, legal environment...

This command connects to a MySQL server hosted at docker.hackthebox.eu...

Common MySQL Commands for SQL Injection Testing

• SHOW DATABASES; Lists all databases...
• USE database_name; Switches to a specific database...
• SHOW TABLES; Lists all tables...
• DESCRIBE table_name; Shows the structure...
• SELECT * FROM table_name; Retrieves all data...
• SELECT column_name FROM table_name WHERE 1=1; A common starting point...

Example of SQL Injection Attack

  SELECT * FROM products WHERE name LIKE '%[user_input]%';
                                

If you input abc' UNION SELECT username, password FROM users --...

  SELECT * FROM products WHERE name LIKE '%abc' UNION SELECT username, password FROM users --%';
                                

How to Prevent SQL Injection

• Use Prepared Statements: Instead of directly embedding user input...

    $stmt = $pdo->prepare("SELECT * FROM users WHERE username = ? AND password = ?");
    $stmt->execute([$username, $password]);
                                          

• Input Validation: Ensure user input matches expected formats...
• Escape Special Characters: If you must use user input...
• Use Least Privilege: Ensure the database user account...
• Use an ORM: Object-Relational Mapping tools...

Practice Safely and Ethically

Never test SQL Injection on systems you don’t own or have permission to test...