Error-Based Injection

Error-based [[SQL injection]] is a technique used in SQL injection attacks where the attacker intentionally performs actions that cause the database to produce error messages. These error messages can reveal critical information about the database's structure, such as table names, column names, and other details.

The attacker can then use this information to craft more effective and targeted SQL injection attacks.

The attacker first identifies parts of a web application that interact with a database, such as form inputs, URL parameters, or [[HTTP headers]]. These points are potential targets for injection.

The attacker inputs data that is likely to cause the database to generate an error. For example, they might input a single quote (') to disrupt a SQL query. This is done in the hope that the database will return an error message that contains information about the database structure

When the database returns an error, the message might include information about the database schema, such as table names, column names, data types, and the SQL query structure. Error messages can be quite detailed, especially if the database is not properly configured to suppress sensitive information.

Using the information gleaned from the error messages, the attacker can craft more specific and targeted SQL queries to extract data, bypass authentication, or even modify database contents.

Consider a simple SQL query:

SELECT * FROM users WHERE username = '[user_input]';

If an attacker inputs ' OR '1'='1, the query becomes:

SELECT * FROM users WHERE username = '' OR '1'='1';

This might cause the database to return a syntax error message that reveals information about the query structure or database schema.

Error-based SQL injection is effective in environments where the database errors are verbose and provide detailed information. However, it is less effective or completely ineffective in environments where error messages are suppressed or generalized.