![]() Even if this approach is perfectly valid, the first one is more popular. The number of columns in the injected select is increased until the database engine does not return an error related to the number of columns. The alternative technique to determine the number of columns is to directly inject a new statement with UNION. ![]() We can now conclude that the original query has 3 columns. ![]() ORA-01785: ORDER BY item must be the number of a SELECT-list expression. SELECT name, description, price FROM products WHERE id= 1 ORDER BY 4 Query generated (selects only 3 columns). Let’s now see how to get rid of a table name error with an example (this list of system tables was used): Notice that at this step, it is not even necessary to specify column names since a minimal SELECT statement can be used. Even if database systems have different naming convention, the number of popular DBMS is really limited and a valid system table name can be found quickly. Guessing may be an option to find a table name that exists in the database (a good one in some cases), but let’s consider an approach that will guarantee successful results even if luck is not on your side. The best way to find such information is to use system tables instead of user tables. For more information refer to the last section of the article. However, the same principle would apply if it was not the case. To simplify learning, this article explains how it can be done when error reporting is enabled. ![]() To do this, a valid table name must be known but it is also necessary to determine the number of columns in the first query and their data type. Because the UNION operator can only be used if both queries have the exact same structure, the attacker must craft a SELECT statement similar to the original query. UNION-based attacks allow the tester to easily extract information from the database. The MySQL UNION operator makes combining the results from SELECT queries quick and painless and is a good tool for getting a quick combined result set from several tables with similar columns.įor more MySQL and MariaDB tips and tricks, check out our other database articles.Understanding how to create a valid UNION-based attack to extract information The UNION operator has merged the results from both tables, using the column names defined in the first SELECT query. The UNION ALL operator works the same way as the UNION operator, but it will include duplicate rows: SELECT column FROM first_table
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