TL;DR
Someone might be able to log in to your website without a password if it’s vulnerable to SQL injection. This guide shows you how to find and fix the most common cause – problems with how login forms are handled.
What is SQL Injection?
SQL injection happens when attackers insert malicious code into your login form fields (username, password). If your website doesn’t properly check this input, it can be used to manipulate the database query and bypass security. The ‘OR 1=1’ trick is a classic example – it always evaluates to true, letting anyone in.
How to Fix It: Step-by-Step
Understand Your Code: Find the part of your website code that handles login. This usually involves taking username and password from the form and using them in a database query.
Most websites use PHP, Python (with frameworks like Django or Flask), Ruby on Rails, or similar languages.
Look for code connecting to databases like MySQL, PostgreSQL, SQL Server, etc.
Never Trust User Input: This is the golden rule! Always treat anything entered by a user as potentially dangerous.
Use Prepared Statements (Parameterized Queries): This is the *best* way to prevent SQL injection. Instead of directly embedding user input into your query, you use placeholders that are filled in safely by the database driver.
PHP Example:
$stmt = $pdo->prepare(‘SELECT * FROM users WHERE username = ? AND password = ?’);
$stmt->execute([$username, $password]);
$user = $stmt->fetch();
Python (using psycopg2 for PostgreSQL):
cur.execute(“SELECT * FROM users WHERE username = %s AND password = %s”, (username, password))
user = cur.fetchone()
Input Validation: While prepared statements are the main defence, validation adds an extra layer of security.
Check Data Types: Make sure usernames and passwords contain only allowed characters (letters, numbers, etc.).
Limit Length: Set maximum lengths for username and password fields. For example, a username shouldn’t be longer than 50 characters.
if (strlen($username) > 50) {
// Handle error – too long!
}
Escaping (Use with Caution): If you absolutely *cannot* use prepared statements (which is rare these days), escaping special characters can help, but it’s much less reliable.
PHP Example: Use mysqli_real_escape_string() or PDO’s built-in escaping features. Be very careful with character encoding!
Warning: Escaping is prone to errors and should be avoided if possible. Prepared statements are far superior.
Least Privilege Principle: The database user your website uses should have only the permissions it *needs*. Don’t give it full admin access.
Web Application Firewall (WAF): A WAF can detect and block common SQL injection attacks. It’s a good extra layer of defence, but don’t rely on it as your sole protection.
Regular Security Scanning: Use tools to automatically scan your website for vulnerabilities, including SQL injection.
OWASP ZAP is a free and open-source scanner.
Commercial scanners are also available.
Testing Your Fix
Try the ‘OR 1=1’ Attack: Enter ‘OR 1=1’ in both the username and password fields. If your fix is working, you should *not* be able to log in.
Other Injection Attempts: Try other common SQL injection payloads (search online for examples).
Fuzz Testing: Use tools to automatically generate a large number of random inputs and see if any cause errors or unexpected behaviour.
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