SQL injection is a common security vulnerability that occurs when user input is not properly validated and sanitized before being used in SQL queries. In the case of a web application, this can result in sensitive data being exposed, unauthorized access to sensitive areas of the website, or even a complete compromise of the target database. In this write-up, we will examine a SQL injection vulnerability that allows for login bypass in a web application, as demonstrated in the Portswigger Lab.
Link for the Lab: https://portswigger.net/web-security/sql-injection/lab-login-bypass
SELECT * FROM users WHERE username = '<username>' AND password = '<password>'
SELECT * FROM users WHERE username = 'administrator' OR '1'='1' AND password = 'test'
OR '1'='1' part of the payload will always evaluate to true, and the original query will be altered to return all records from the
users table. This will allow the malicious user to bypass the login process and gain unauthorized access to the application.
To prevent this vulnerability, the web application should implement proper input validation and sanitization to ensure that user input is not being used to manipulate the behavior of SQL queries. This can be achieved through the use of prepared statements or parameterized queries, which separate user input from the SQL query and prevent malicious payloads from being executed.
In conclusion, SQL injection is a serious security vulnerability that can have significant consequences if not properly addressed. To prevent this vulnerability, it is important to implement proper input validation and sanitization in web applications. By taking these steps, web applications can be protected from malicious actors who may attempt to exploit SQL injection vulnerabilities for malicious purposes.