SQL Injection
SQL Injection is a code injection technique that exploits vulnerabilities in an application's software by manipulating the SQL queries made to a database. It is a common and serious security threat that can result in unauthorized access to a database, leading to data theft, data manipulation, and even the complete compromise of a system.
How It Works
1. **Input Manipulation**: Attackers input malicious SQL code into form fields, URL parameters, or cookies.
2. **Query Execution**: The malicious input is included in an SQL query without proper sanitization.
3. **Database Response**: The database executes the manipulated query, allowing the attacker to read, modify, or delete data.
Types of SQL Injection
1. **Classic SQL Injection**: Direct insertion of SQL commands into user inputs.
2. **Blind SQL Injection**: The attacker cannot see the database output but can infer it through the application's behavior.
3. **Error-based SQL Injection**: Exploits database error messages to gain information about the database structure.
4. **Union-based SQL Injection**: Uses the UNION SQL operator to combine results from multiple queries into a single result set.
5. **Time-based Blind SQL Injection**: Uses time delays to infer whether certain conditions are true or false.
Common Attacks
- **Retrieving Hidden Data**: Modify a query to return additional results.
- **Subverting Application Logic**: Change a query to interfere with the application's logic.
- **Union Attacks**: Retrieve data from different database tables.
- **Examining the Database**: Extract information about the database version and structure.
- **Blind SQL Injection**: Extract data by evaluating responses from true/false queries.
Prevention Techniques
1. **Input Validation**: Ensure that user inputs are validated and sanitized before including them in SQL queries.
2. **Parameterized Queries**: Use prepared statements or parameterized queries to separate SQL code from data.
3. **Stored Procedures**: Use stored procedures to encapsulate SQL queries.
4. **Least Privilege Principle**: Limit database permissions to the minimum necessary for the application to function.
5. **Error Handling**: Do not expose detailed error messages to users; instead, log them for internal review.
6. **Regular Security Audits**: Conduct regular security assessments and code reviews to identify and fix vulnerabilities.
