Powershell – validate domain user with password

Another common problem yesterday: how to validate a domain user with a password. I had a service account that I suscpected had an invalid password. After some googling and trying different solutions, I came accross a post by Shay Levy that fitted my purpose.

I wrote a function based on the Levy post, and the following function CheckCredentials will validate username on format “domain\user” and password againt the supplied domain.

Add-Type -AssemblyName System.DirectoryServices.AccountManagement 

function CheckCredentials( [String]$username,  [String]$password)
{
    # find seperator character '\' in username string
    $sepidx = $username.IndexOf('\') ;

    # pick domain from username string
    $domain = $username.Substring(0, $sepidx);
    # pick user from username string
    $user = $username.Substring($sepidx+1, ($username.Length - $sepidx)-1)

    # create instance for domian principle context for input user
    $ct = [System.DirectoryServices.AccountManagement.ContextType]::Domain
    $pc = New-Object System.DirectoryServices.AccountManagement.PrincipalContext `
                        $ct,$domain

    # validate user credential for user with password against domain
    $res = $pc.ValidateCredentials($user,$password)

    return $res; #true: ok, false: invalid username and passwrod
}

The script will pick the domain from the supplied username string based on the ‘\’ seperator character. The function returns true of the username is successfully validated, otherwise false.