SQL Injection: Hack Websites with 1 Line of Code (SQLmap Tutorial)

Understanding Databases and SQL Injection Attacks

This article explains databases, how they function, and the risks of SQL injection, a common type of cyberattack. We'll cover the basics of database structure, how websites use them, and how malicious actors can exploit vulnerabilities.

What is a Database?

A database is a structured storage system for data. Think of it as a sophisticated network warehouse. When you register on a website and fill in your account and password, that information is stored in a database. Product information on e-commerce sites like Taobao or a user's collection list on platforms like Bilibili are also stored in databases.

• These databases are often dynamic, meaning the content changes based on the user or other factors. This contrasts with static web pages, where the content is fixed HTML that everyone sees.

How Databases Work: An Example with Bilibili

Let's illustrate with an example using Bilibili, a popular video-sharing platform.

1. User Authentication: When you log in, you enter your account and password.
2. Database Query: The system checks your user ID (UID) in a "user collection table." This table might have columns for user ID (UID), video ID (BBID), and the time of collection.
3. Data Retrieval: The system executes a query like "Select * from collection table where UID = 10086" to retrieve your data.
4. Displaying Results: The retrieved data is then processed (using languages like PHP or Java) and displayed on the webpage, showing you the videos you've collected. Similar processes are used for displaying your coin balance and other user-specific information.

Database Structure: Tables, Columns, and Rows

Think of a database as a collection of Excel spreadsheets.

• Table: An Excel sheet, stores a specific type of data (e.g., user accounts, product details). A database contains multiple tables. Examples for Bilibili could include a table for collected videos, a coin table, and tables for attention lists and fan lists.

• Column: A fixed category of data within a table (e.g., username, password, product price).

• Row: A specific piece of data within a table, representing an individual entry (e.g., your account information, a specific product).

SQL: Communicating with the Database

SQL (Structured Query Language) is the language programmers use to interact with databases. It allows them to retrieve, add, modify, and delete data.

• Example Queries:

  • SELECT mobile_number FROM user_table WHERE username = 'xiaobai': This retrieves the mobile number of the user named "xiaobai."

  • DELETE FROM order_table WHERE price = 0: This deletes all orders with a price of zero.

SQL Injection: A Major Security Risk

SQL injection is a type of cyberattack where malicious actors insert harmful SQL code into a website's input fields. This can allow them to bypass security measures, access sensitive data, or even take control of the database.

How SQL Injection Works

Let's consider a login process:

1. Normal Login: You enter your username and password.
2. SQL Query: The website constructs an SQL query to verify your credentials (e.g., SELECT * FROM user_table WHERE username = 'xiaobai' AND password = '123456').
3. Malicious Input: An attacker might enter a username like ' or 1=1 --. This input changes the SQL query to something that always evaluates to true.
4. Bypassing Authentication: The modified query allows the attacker to log in without knowing the actual password. They can even potentially access or modify other users' data.

Why SQL Injection Works

The root cause of SQL injection vulnerabilities is trusting user input too much. When code directly concatenates user-supplied strings into SQL queries without proper sanitization, it opens the door to attacks.

Preventing SQL Injection

• Parameterization: The preferred defense is to use parameterized queries (also known as prepared statements). This separates the SQL code from the user-supplied data, preventing malicious code from being executed. The user inputs are treated as plain text.

• Principle of Least Privilege: Grant database users only the necessary permissions.

• Zero Trust: Don't trust user input implicitly.

Web Application Firewalls (WAFs)

A Web Application Firewall (WAF) protects web applications (websites) from various network attacks, including SQL injection.

• How WAFs Work: WAFs analyze HTTP and HTTPS traffic, looking for patterns and signatures of known attacks. They can block malicious requests before they reach the web application.

• Limitations: While helpful, WAFs are not a foolproof solution. Attackers can sometimes bypass them, and WAFs cannot fix underlying vulnerabilities in the application code.

SQLMap: An Automated SQL Injection Tool

SQLMap is an open-source penetration testing tool that automates the process of detecting and exploiting SQL injection vulnerabilities. It can identify vulnerabilities, extract data, and even take control of database servers.

• Demonstration: The article briefly demonstrates using SQLMap to identify databases, tables, and data within a vulnerable application.

Real-World Examples of Data Breaches

• Time Machine (2004): A data leak exposed 31 million user authentication records.

• Equifax (2017): An SQL injection attack compromised over 147 million user records, costing the company significant financial losses and reputational damage.

Conclusion

Understanding databases and the risks of SQL injection is crucial for both developers and security professionals. By implementing proper security measures, such as parameterized queries and WAFs, organizations can significantly reduce their risk of falling victim to these attacks. While defensive technologies exist, it is always better to start by writing safe code with proper attention to the nature of external inputs and data.