Introduction to SQL Injection

Study Notes

Introduction to SQL Injection

SQL injection is a code injection technique used to attack data-driven applications.
It lets attackers manipulate the database queries executed by the application.
This can lead to unauthorized access, data breaches, and other security vulnerabilities.

How SQL Injection Works

Attackers inject malicious SQL code into input fields.
The application, without proper validation, treats the injected code as legitimate SQL commands.
The injected code modifies the database's intended queries and yields unintended results.
For example, attackers can use SQL statements like ' OR '1'='1 to bypass authentication or DELETE FROM users; to delete all users from a database.

Types of SQL Injection

In-band SQL injection: Attackers retrieve the results of their injected SQL statements directly in the application's response.
Inferential SQL injection: An indirect attack where attackers infer database schema and data by analyzing the application's responses to different SQL queries.
Out-of-band SQL injection: Exploits alternate channels (e.g., mail server or remote file system) to communicate with the database—less common due to detection.

Vulnerable Code Examples

Code that directly concatenates user input to SQL queries without sanitization.
Code that lacks parameterized queries.
Code with improperly validated user-supplied input.

Prevention Techniques

Input Validation: Validate and sanitize all user-supplied input before using in SQL queries.
Parameterized Queries: Use parameterized queries (prepared statements), ensuring user input is treated as data, not code, separating data from the query structure.
Stored Procedures: Use stored procedures to encapsulate database operations, usually with better validation.
Least Privilege Principle: Give database accounts only the necessary privileges.
Output Encoding: Encode special characters in output to prevent further manipulation.
Web Application Firewalls (WAFs): Detect and block malicious SQL injection attacks.
Regular Updates: Keep databases and web applications updated with the latest security patches.

Preventing SQL Injection in Parameterized Queries

Parameterized queries treat user input as data, not part of the SQL command, preventing malicious input from affecting query execution.
Modern programming languages often have built-in support for parameterized queries or prepared statements.

Impact of SQL Injection Attacks

Unauthorized access to sensitive data.
Data modification or deletion.
Denial-of-service attacks on the database.
System compromise via database access.
Financial loss due to data breaches.
Reputational damage to organizations.

Common SQL Injection Attack Vectors

Input fields (usernames, passwords, search boxes, forms).
Cookies and HTTP headers.
Hidden form fields.
Using query parameters without proper quoting.

Detection Techniques

Penetration testing.
Security tools (like WAFs) for malicious pattern monitoring.
Observing error messages in web application responses.
Reviewing security logs regularly.

Mitigation Strategies

Secure coding practices.
Implementing input validation rules.
Consistent use of parameterized queries.
Using stored procedures, when appropriate.
Strengthening database access controls.

Description

This quiz covers the fundamental concepts of SQL injection, a code injection technique that targets data-driven applications. You will learn how attackers manipulate database queries and the various types of SQL injection attacks. Understanding these details is vital for securing applications against such vulnerabilities.