SQL Injection

What is SQL Injection?

SQL Injection is a code injection technique that exploits vulnerabilities in an application's software by inserting or 'injecting' malicious SQL code into a query. This can allow attackers to access, manipulate, or delete data in your database, potentially leading to data breaches and loss.

How SQL Injection Works

The attacker usually enters malicious SQL code into an input field, which the application then mistakenly executes. For example, instead of a user entering just their username, they could enter:

This input might transform a query like:

The injected SQL code can change the intent of the query, potentially returning all rows in the users table instead of none.

Preventing SQL Injection

The best way to prevent SQL injection is by using parameterized queries (also known as prepared statements) that separate SQL logic from data. This ensures that user inputs are treated as data rather than executable code.

Using Parameterized Queries

Parameterized queries use placeholders for user input. Here is an example using Python's sqlite3 library:

By using ? as a placeholder and passing the username as a separate parameter, the database treats it solely as data, eliminating the risk of SQL injection.

Using Prepared Statements

Prepared statements are similar to parameterized queries but are often used in more complex applications. Here is an example using PHP's PDO:

In this PHP example, the :username placeholder is used to safely incorporate user input into the query. The execute method binds the user input to this placeholder.

Additional Precautions

Besides parameterized queries and prepared statements, consider these additional measures:

• Input Validation: Validate and sanitize user inputs to ensure they conform to expected formats.
• Least Privilege Principle: Give database accounts only the permissions necessary for their function.
• Error Handling: Avoid displaying detailed database error messages to users.