SQL Injection Attack: What is it, and how can we defend ourselves from it?
SQL Injection is a vulnerability where attackers tamper with the SQL queries that an application sends to a database. Let me explain this with an example.
Imagine a login page and for authentication purposes, a user uses a username and password. If inputs are correct then the user is presented with his or her profile page, otherwise the user is presented with an error message. If this application is vulnerable to SQL Injection, which means it doesn't use parametrized queries, it doesn't validate user input, then what will happen is that any SQL characters or SQL code that the attacker adds as part of the payload will become part of the query. So essentially what happened over here is that the attacker exploited a SQL injection vulnerability in the login functionality of the application to bypass authentication. So in this case, the attacker no longer needed to know the admin's password because the attacker was able to change the query to no longer ask for the admin's password.
Impact on Security
Can view sensitive information
Can be used to alter the database
Can delete data
For another example, imagine you're at the bank about to send money to your friend through a wire transfer. You write down the instructions on a piece of paper and give it to the bank's accountant after confirming your identity. But when you leave, some bad people change your instructions. They add an extra line saying you should transfer $700 to an unknown account.
Since the accountant already verified your identity, they follow both sets of instructions - the correct one and the fraudulent one.
Now, let's compare this to an SQL injection attack. When you're dealing with people, you'd likely double-check the instructions before handing them over to make sure everything is correct. Unfortunately, a web application doesn't have this ability. If the server isn't protected, the attack can succeed. In the context of SQL injection, it means "injecting" harmful SQL code (a "true statement") into the input data that a client submits to the application. This can lead to unauthorized access and manipulation of the application's database.
SQL Injection in a Login Form
Suppose you have a login form on a website where users enter their username and password. The application queries the database using the submitted values to check if the user exists and if the password is correct.
Legitimate SQL query:
SELECT * FROM users WHERE username = 'input_username' AND password = 'input_password';
Malicious SQL injection:
input_username: ' OR '1'='1
input_password: anything
Explanation: The malicious user enters ' OR '1'='1 as the username, and anything as the password. The SQL query becomes:
SELECT * FROM users WHERE username = '' OR '1'='1' AND password = 'anything';
Since '1'='1' is always true, the query will return all records from the "users" table, effectively bypassing the login and granting unauthorized access to the system.
SQL Injection in a Search Form
Consider a search form on a website where users can search for products by entering a keyword. The application queries the database using the submitted keyword.
Legitimate SQL query:
SELECT * FROM products WHERE product_name LIKE '%input_keyword%';
Malicious SQL injection:
input_keyword: ' OR 1=1; --
Explanation: The malicious user enters ' OR 1=1; -- as the keyword. The SQL query becomes:
SELECT * FROM products WHERE product_name LIKE '%' OR 1=1; -- %';
The double dash -- is a SQL comment and ignores the rest of the original query. The injected SQL 1=1 is always true, resulting in all products being returned in the search, instead of the intended search results.
In both cases, the attackers manipulated the input data to inject malicious SQL code, exploiting vulnerabilities in the web application's handling of user input. To prevent SQL injection, proper input validation and parameterized queries or prepared statements should be used.
Why SQL Injection Attacks Are Very Harmful
SQL injection attacks can cause serious problems. Attackers can steal personal information, passwords, and sensitive data, leading to identity theft and financial fraud. This not only affects the people whose information was stolen but also the company that suffered the security breach. Companies may face angry customers, lawsuits, and compensation costs, and their reputations can be severely damaged, sometimes even forcing them to shut down.
Cybercriminals target personal information, like social security numbers (SSNs), because it remains useful for a long time. They can commit crimes months or years after stealing this data. This is different from bank information and credit card details, which require more immediate action for criminals to use or sell the information. In the hacker community, there are hidden online stores where stolen information is sold for malicious purposes.
Now that we understand what an SQL injection attack is and why it's so harmful, let's explore the precautions we can take to avoid these attacks.
To make your web application secure and protect it from SQL injection attacks, you need to take specific actions to defend your server:
Avoid Dynamic SQL, Use Prepared Statements Instead
Never directly insert user input into SQL queries. Disable "data interpretation" to store user data without executing it as SQL code. Prepared statements allow the safe handling of user input, keeping it separate from the SQL query.
Sanitize User Input
Ensure that special SQL syntax is restricted from being inserted as user input. Data that is safe for JSON files might be harmful if used in SQL queries or SSH commands.
Limit Database Permissions
Follow the principle of least privilege (POLP). Assign the minimum necessary access level for each user. Avoid granting "all privileges" unless genuinely required for specific tasks.
Limit Display of Specific Errors
Prevents detailed error messages that expose sensitive information. Instead of displaying specific errors like "User 'JohnDoe123' was not found," restrict error messages or turn them off completely. Only internal users should have access to error logs for troubleshooting purposes.
If you like to read more about prevention methods, please visit the OWASP SQL Injection Prevention Cheat Sheet.
I would like to express my gratitude to all the readers who took the time to explore this topic with me. Thank you for your interest and attention. I hope you found the information valuable and insightful.
Remember, knowledge is the first step towards building a safer and more secure digital environment. By staying informed and implementing the necessary precautions, we can collectively protect ourselves and others from potential threats.
If you have any further questions or would like to delve deeper into this subject, please feel free to reach out. Your feedback and engagement are essential in fostering a community dedicated to enhancing our online safety.
Once again, thank you for being part of this journey, and I wish you all the best in your endeavors. Stay safe and informed!