Start-Process powershell credentials don't work but when using cmd it does

Question

I am trying to run a powershell script from another powershell script passing in the credentials of a different user and then using the credentials:

Start-Process powershell.exe -Credential "LON\my-user" -NoNewWindow -ArgumentList "-file C:\DevopsScripts\stuckApps.ps1"

I have this is numerous different ways all get the same error. I have tried setting the username and password before the command:

$username = "LON\my-user"
$password = "pass"
$PSS = ConvertTo-SecureString $password -AsPlainText -Force
$cred = new-object system.management.automation.PSCredential $username,$PSS
$env:USERNAME 
Start-Process powershell.exe -Credential $cred -NoNewWindow -ArgumentList "-file C:\DevopsScripts\stuckApps.ps1"

But everything I try gets the error:

Start-Process : This command cannot be run due to the error: The user name or password is incorrect.

I know the username and password are correct as they have been tested on the cmd which it works fine:

C:\Users\ADM-me>runas /noprofile /user:LON\my-user"powershell.exe C:\DevopsScripts\stuckApps.ps1"

What am I doing wrong here and how could I fix this, preferably by setting the password beforehand, so this can be automated. Also this does not need to be done using Start-Process, just this is the closest thing I could find to working.

I think the problem I am having is this, in stuck apps it has this:

$conn = New-Object System.Data.SqlClient.SqlConnection
$conn.ConnectionString = "Server = mssql.co.uk; Database = mydata; Integrated Security = true;"
$conn.Open()

I need this to run the credentials that I am trying to pass through it or else I get this error. `Exception calling "Open" with "0" argument(s): "Login failed. The login is from an untrusted domain and cannot be used with Windows authentication."

But I can't pass the credentials through as the only ones that work are admin ones, (which I have but then that will throw the error above). Is it possible for me to use the admin logins to access stuck apps then use the logins needed to connect on stuck apps as an AD login.

Answer 1

Your first attempt with -Credential "LON\my-user" can't work, but your second attempt is correct, building the object of class PSCredential, as required (see the type in Get-Help Start-Process -Parameter Credential, it is PSCredential and not String). I tried the same with some reused code here, and it works here both or CMD and PS1 calling a PS1 test script via Powershell.exe, using a local test account (sorry, no domain @home).

So even though my code ist not identical and the domain of the user is the local machine, the approach is the same compared to yours and - sorry that this does not solve your problem - I don't see that you are doing sth. wrong.

To play safe, please make sure though to test with the same Powershell version, the below scripts executed under W10 1607 (so Powershell 5.1.14393.1198), all scripts in the same directory.

testscript.ps1

write-host "Testscript is run with user: $($env:USERNAME)"
Start-Sleep 2

testrun.cmd

runas /noprofile /user:%COMPUTERNAME%\myaccount "powershell.exe -NoProfile -ExecutionPolicy ByPass -file %~dp0testscript.ps1"

testrun.ps1

$Username       = "$($env:COMPUTERNAME)\myaccount"
$Password       = 'mypassword'
$SecurePassword = ConvertTo-SecureString -String $Password -AsPlainText -Force
$ScriptFile     = Join-Path -Path $PSScriptRoot -ChildPath 'testscript.ps1'
$Credential     = New-Object System.Management.Automation.PSCredential( $Username, $SecurePassword)
$StartOpts = @{ 'FilePath'        = 'powershell.exe'
                'Credential'      = $Credential
                'NoNewWindow'     = $false
                'ArgumentList'    = @( '-f', $ScriptFile,
                                       '-ExecutionPolicy', 'Bypass',
                                       '-NoProfile'
                                     )
               }
Start-Process @StartOpts

Some remarks on testrun.ps1

• Don't mind the parameters for Start-Process being passed as a hashtable, it's just better readable for me, otherwise it makes not difference
• The ArgumentList is being passed as a string array here - I prefer it this way so that it is automatically taken care for double qouting parameters, e.g. when the pathname of the script directory would contain spaces
• The parameter -NoNewWindow passed to Start-Process seems not to have any effect here - a new window is opened
• I always recommend to add the parameters -Noprofile and -ExecutionPolicy Bypass when using Powershell.exe to launch scripts or execute commands, just to make sure it works despite of the Execution Policy set or any present user or machine profile scripts.
  However, at least the parameter -NoProfile seems not to work the same when Powershell.exe is being called fom the above CMD or PS1. Called from PS1, my machine profile gets nevertheless executed, but not fom CMD... interesting! The MSDN: PowerShell.exe Command-Line Help just says about this parameter: "Does not load the Windows PowerShell profile." Funny! There are six of them, see Technet: Understanding the Six PowerShell Profiles. I use "Current User, Current Host – console" and "All Users, Current Host – console". Lesson learned, but I am not sure if it's a bug or a feature.