SQL Injection
SQL Injection
SQL injection is a type of security vulnerability that occurs when an attacker inserts malicious SQL statements into a form field or other user input field in a web application. The injected SQL statement can manipulate the database to execute unintended commands or retrieve sensitive data. Here are some examples of SQL injection attacks:
- Login bypass:
An attacker can use SQL injection to bypass login credentials and gain unauthorized access to a web application by submitting a crafted username and password, such as:
username: ' or 1=1 --
password: anything
This will result in the following SQL query:
SELECT * FROM users WHERE username = '' or 1=1 -- ' AND password = 'anything';
The double hyphen (–) is used to comment out the rest of the SQL statement, so the password check is effectively ignored.
- Information disclosure:
An attacker can use SQL injection to retrieve sensitive information from a web application by submitting a crafted input that retrieves data from the database, such as:
input: '; SELECT * FROM users –
This will result in the following SQL query:
SELECT * FROM table_name WHERE input = ''; SELECT * FROM users -- ';
The semicolon (;) separates the two SQL statements, and the double hyphen (–) comments out the rest of the original statement.
- Data manipulation:
An attacker can use SQL injection to manipulate data in a web application by submitting a crafted input that updates or deletes data in the database, such as:
input: '; DROP TABLE users –
This will result in the following SQL query:
SELECT * FROM table_name WHERE input = ''; DROP TABLE users -- ';
The semicolon (;) separates the two SQL statements, and the DROP TABLE command is used to delete the users table from the database.
To prevent SQL injection, it is important to use prepared statements or parameterized queries in web applications to ensure that user input is properly sanitized and validated before being used in SQL statements. Additionally, limiting user privileges and using input validation and filtering can help prevent attacks.