SQL Injection Attacks: Common Input Validation Errors

SQL injection attacks occur when an attacker is able to manipulate a web application’s database query by injecting malicious SQL code. This typically happens due to improper input validation, allowing for unauthorized data access or modification. Below are three practical examples that highlight common input validation errors leading to SQL injection vulnerabilities.

Example 1: Login Authentication Bypass

In a typical web application, users enter their credentials to log in. An input validation error can allow an attacker to bypass this authentication mechanism.

In this case, consider a login form that uses the following SQL query to validate user credentials:

SELECT * FROM users WHERE username = 'user_input' AND password = 'pass_input';

If the application does not properly validate the input, an attacker can input the following:

' OR '1'='1'; --

This input modifies the SQL query to:

SELECT * FROM users WHERE username = '' OR '1'='1' AND password = ''; --';

This condition is always true, allowing the attacker to bypass authentication and gain unauthorized access to the application.

Notes:

• To mitigate this type of attack, always use parameterized queries or prepared statements to ensure user inputs are treated as data, not executable code.

Example 2: Data Exfiltration via User Profile

In many applications, users can view their profile information stored in a database. If input validation is lacking, an attacker can extract data from the database.

Consider a scenario where the application retrieves user profile data with the following SQL query:

SELECT * FROM profiles WHERE user_id = 'user_input';

An attacker could input:

1; SELECT * FROM users; --

The resulting SQL query would look like this:

SELECT * FROM profiles WHERE user_id = '1'; SELECT * FROM users; --';

This allows the attacker to execute a second query that retrieves all users from the database, potentially exposing sensitive information.

Notes:

• Implementing strict input validation and using the principle of least privilege can help prevent unauthorized access to sensitive data.

Example 3: Altering Database Records

An attacker can also exploit input validation errors to alter or delete records in a database. This can have serious consequences for the integrity of the data.

Consider an application that allows users to update their profile information using an SQL query like:

UPDATE profiles SET email = 'new_email' WHERE user_id = 'user_input';

If validation is inadequate, the attacker could input:

1; DELETE FROM profiles; --

This would change the query to:

UPDATE profiles SET email = 'new_email' WHERE user_id = '1'; DELETE FROM profiles; --';

In this case, the attacker successfully deletes all entries in the profiles table, leading to data loss.

Notes:

• Always sanitize and validate input data, and consider implementing stored procedures to limit the potential for destructive queries.

By understanding these examples of SQL injection attacks, developers can better secure their applications and protect against input validation errors. Proper input validation is a critical aspect of maintaining database security.