SQL Injection Exploitation series

Vishal
4 min readDec 19, 2022

Hello!!! in this series will try to exploit the SQL injection manually as well as using sqlmap.

To illustrate or practice, I am going to use the bWAPP a free and opensource deliberately insecure web app, you can download it from here.

Before starting lets see what is SQLi? and its type. Then we will see how to exploit it.

As per PortSwigger, SQL injection (SQLi) is a web security vulnerability that allows an attacker to interfere with the queries that an application makes to its database. It generally allows an attacker to view data that they are not normally able to retrieve.

As per OWASP, A SQL injection attack consists of insertion or “injection” of a SQL query via the input data from the client to the application.

There are many definitions to SQLi, but we want to learn it practically.

Types of SQL injection.

Types of SQL injection:

In-band SQLi:

In-band SQL Injection is the most common and easy-to-exploit of SQL Injection attacks. In-band SQL Injection occurs when an attacker is able to use the same communication channel to both launch the attack and gather results.

The 2 most common types of In-band SQLi are:

Error-based SQLi and Union Based SQLi.

Error-based SQLi:

Error-based SQLi is an in-band SQL Injection technique that relies on error messages thrown by the database server to obtain information about the structure of the database. In some cases, error-based SQL injection alone is enough for an attacker to enumerate an entire database. While errors are very useful during the development phase of a web application, they should be disabled on a live site, or logged to a file with restricted access instead.

Union-based SQLi:

Union-based SQLi is an in-band SQL injection technique that leverages the UNION SQL operator to combine the results of two or more SELECT statements into a single result which is then returned as part of the HTTP response.

Inferential SQLi (Blind SQLi):

Inferential SQL Injection, unlike in-band SQLi, may take longer for an attacker to exploit, however, it is just as dangerous as any other form of SQL Injection. In an inferential SQLi attack, no data is actually transferred via the web application and the attacker would not be able to see the result of an attack in-band (which is why such attacks are commonly referred to as “blind SQL Injection attacks”). Instead, an attacker is able to reconstruct the database structure by sending payloads, observing the web application’s response and the resulting behavior of the database server.

Boolean-based Blind SQLi:

Boolean-based SQL Injection is an inferential SQL Injection technique that relies on sending an SQL query to the database which forces the application to return a different result depending on whether the query returns a TRUE or FALSE result.
Depending on the result, the content within the HTTP response will change, or remain the same. This allows an attacker to infer if the payload used returned true or false, even though no data from the database is returned.

Time-based Blind SQLi:

Time-based SQL Injection is an inferential SQL Injection technique that relies on sending an SQL query to the database which forces the database to wait for a specified amount of time (in seconds) before responding. The response time will indicate to the attacker whether the result of the query is TRUE or FALSE.
Depending on the result, an HTTP response will be returned with a delay, or returned immediately. This allows an attacker to infer if the payload used returned true or false, even though no data from the database is returned.

Out-of-band SQLi:

It is not very common, mostly because it depends on features being enabled on the database server being used by the web application. Out-of-band SQL Injection occurs when an attacker is unable to use the same channel to launch the attack and gather results.
Out-of-band techniques, offer an attacker an alternative to inferential time-based techniques, especially if the server responses are not very stable (making an inferential time-based attack unreliable).
Out-of-band SQLi techniques would rely on the database server’s ability to make DNS or HTTP requests to deliver data to an attacker. Such is the case with Microsoft SQL Server’s xp_dirtree command, which can be used to make DNS requests to a server an attacker controls; as well as Oracle Database’s UTL_HTTP package, which can be used to send HTTP requests from SQL and PL/SQL to a server an attacker controls.

So now we know what is SQL injection and what are its type. Now we will see how to exploit it one by one.

You can find the link to the next blog i.e.error based sqli here.

--

--