Basic Loop Help - Powershell - powershell

Question

Complete Powershell Noobie here.
I have a .bat file that I would like to convert to Powershell.
Basically when run; it asks the user to enter their Active Directory credentials. Once validated; it starts a RSAT tool (example: dhcpmgmt.msc) as the elevated domain user.
However, if credentials are incorrect (if %ERRORLEVEL% EQU 5); it does a GOTO an echo "Incorrect username and password" and then loops back requesting the user to enter their credentials again.
When I use:
do
{
Start-Process -FilePath C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe -Credential (Get-Credential "$env:USERDNSDOMAIN\") -ArgumentList "C:\Windows\System32\dhcpmgmt.msc"
} until ($response -eq $null)
It works. But if I enter an incorrect password; the window closes.
I would like a notification information the user that the Username/Password is incorrect and then re-direct them to enter their credentials again. This would loop until either the user enters the correct credentials or simple clicks the cancel button.
Any help/guidance is highly appreciated. Thanks a bunch in advance!

Answer 1

You can run this in the while loop to keep asking for credentials until they are valid.
Take credentials
Run powershell with new creds
If fails, ask for new credentials. Break out of the loop if no.
while ($true)
{
$userCreds = Get-Credential "$env:USERDNSDOMAIN\"
try {
Start-Process powershell -Credential $userCreds -ArgumentList "C:\Windows\System32\dhcpmgmt.msc" -ErrorAction Stop
break
}
catch {
Write-Output "Invalid Credentials"
Write-Output "Enter new credentials?"
if ((Read-Host) -ne "Yes") { break }
}
}

Answer 2

This should do the needful.
Loop to Get and Check Credential
Try-Catch Credential Check
Raise Messagebox on Failed Credential
Exit script on Cancel.
$Credential=$null
while ($Credential -eq $null) {
$Credential = Get-Credential -Username "$env:USERDNSDOMAIN\" -message "Enter Admin Password"
try {
Start-Process -FilePath cmd.exe /c -Credential $Credential
}
catch {
$Credential=$null
IF (
$([System.Windows.MessageBox]::Show('Invalid UN/PW! ?','Credential Error','OKCancel','Error')
) -eq "Cancel") { EXIT}
}
}
### Your code to launch RSAT tools here:
We use a while loop.
While the credentials are NULL we p, getting the credentials, storing it as a secure string in a variable, then do a try-catch on the test of running a process, if that will try to get the credentials again, and we store the credentials in a variable as a secure string.
Initially, credentials are NULL so we ask for them.
Then we use Try to test the credentials by initiating a process as them.
If that fails we Catchit and 1st set credentials to NULL again, then we Raise a Windows Message Box to the user letting them know the credentials failed and checking if they would like to try again (OK) or Cancel.
If they respond with Cancel, there is no point in continuing the script so we just exit.
Otherwise, we just go ahead with our loop as planned