SQL injection

SQL injection is a technique often used to attack databases through a website. This is done by including portions of SQL statements in a web form entry field in an attempt to get the website to pass a newly formed rogue SQL command to the database (e.g. dump the database contents to the attacker). SQL injection is a code injection technique that exploits a security vulnerability in a website’s software. The vulnerability happens when user input is either incorrectly filtered for string literal escape characters embedded in SQL statements or user input is not strongly typed and unexpectedly executed. SQL commands are thus injected from the web form into the database of an application (like queries) to change the database content or dump the database information like credit card or passwords to the attacker. SQL injection is mostly known as an attack vector for websites but can be used to attack any type of SQL database.

• SQL code is injected into the sql query

• Allows attacker to do almost anything the database user is permitted

• Example sql statement will return all the data from the ‘users’ table:

$sql = "SELECT * FROM users WHERE
username='$user' AND password='$pass'";
$user and $pass contain the value ' OR 1=1"

• Further attack possibilities: insert data, delete data, read data, denial of service…

Counter Measures

• Use prepared statements when supported by the database

• Use database-specific escaping functions when creating the sql statement ex: mysqli_real_escape_string()

• Addslashes() is not a sufficient approach

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