Use-Impersonation.psm1

function Use-Impersonation
{
    param(
        [string] $Username,
        [securestring] $Password,
        [string] $Domain = '.\',
        [scriptblock] $ScriptBlock
    )
<#
    .SYNOPSIS 
        Impersonates a user and executes a script block as that user.
    .PARAMETER Username
        The username with which you'd like to impersonate
    .PARAMETER Password
        A SecureString representing the user's password
    .PARAMETER Domain
        An optional domain. You may omit this parameter if you wish to impersonate a local user.
    .PARAMETER ScriptBlock
        The code to execute
    .EXAMPLE
        Use-Impersonation -Username "myuser" `
            -Password (ConvertTo-SecureString "mypassword" -AsPlainText -Force) `
            -Domain "WORKGROUP" `
            -ScriptBlock { Write-Host "Hello World!" }
#>
        
    $logonUserSignature =
@"
[DllImport( "advapi32.dll" )]
public static extern bool LogonUser( String lpszUserName,
                                    String lpszDomain,
                                    String lpszPassword,
                                    int dwLogonType,
                                    int dwLogonProvider,
                                    ref IntPtr phToken );
"@

    $AdvApi32 = Add-Type -MemberDefinition $logonUserSignature -Name "AdvApi32" -Namespace "PsInvoke.NativeMethods" -PassThru

    $closeHandleSignature =
@"
[DllImport( "kernel32.dll", CharSet = CharSet.Auto )]
public static extern bool CloseHandle( IntPtr handle );
"@

    $Kernel32 = Add-Type -MemberDefinition $closeHandleSignature -Name "Kernel32" -Namespace "PsInvoke.NativeMethods" -PassThru
        
    try
    {
        $Logon32ProviderDefault = 0
        $Logon32LogonInteractive = 2
        $tokenHandle = [IntPtr]::Zero
        $unmanagedString = [IntPtr]::Zero;
        $success = $false
        
        try
        {
            $unmanagedString = [System.Runtime.InteropServices.Marshal]::SecureStringToGlobalAllocUnicode($Password);
            $success = $AdvApi32::LogonUser($Username, $Domain, [System.Runtime.InteropServices.Marshal]::PtrToStringUni($unmanagedString), $Logon32LogonInteractive, $Logon32ProviderDefault, [Ref] $tokenHandle)
        }
        finally
        {
            [System.Runtime.InteropServices.Marshal]::ZeroFreeGlobalAllocUnicode($unmanagedString);
        }
        
        if (!$success)
        {
            $retVal = [System.Runtime.InteropServices.Marshal]::GetLastWin32Error()
            Write-Host "LogonUser was unsuccessful. Error code: $retVal"
            return
        }

        $identityName = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name
        Write-Host "Current Identity: $identityName"

        $newIdentity = New-Object System.Security.Principal.WindowsIdentity( $tokenHandle )
        $context = $newIdentity.Impersonate()

        $identityName = [System.Security.Principal.WindowsIdentity]::GetCurrent().Name
        Write-Host "Impersonating: $identityName"

        & $scriptBlock
    }
    catch [System.Exception]
    {
        Write-Host $_.Exception.ToString()
    }
    finally
    {
        if ($null -ne $context)
        {
            $context.Undo()
        }
        if ($tokenHandle -ne [System.IntPtr]::Zero)
        {
            $Kernel32::CloseHandle($tokenHandle) | Out-Null
        }
    }
}

Export-ModuleMember -Function "Use-Impersonation"