function Test-IsAdministrator
{
$Identity = [System.Security.Principal.WindowsIdentity]::GetCurrent()
$Principal = New-Object System.Security.Principal.WindowsPrincipal($Identity)
$Principal.IsInRole([System.Security.Principal.WindowsBuiltInRole]::Administrator)
}
function Test-IsUacEnabled
{
(Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Policies\System).EnableLua -ne 0
}
if (!(Test-IsAdministrator))
{
if (Test-IsUacEnabled)
{
[string[]]$argList = @('-NoProfile', '-NoExit', '-File', $MyInvocation.MyCommand.Path)
$argList = $MyInvocation.BoundParameters.GetEnumerator() | ForEach-Object {"-$($_.Key)", "$($_.Value)"}
$argList = $MyInvocation.UnboundArguments
Start-Process PowerShell.exe -Verb Runas -WorkingDirectory $pwd -ArgumentList $argList
return
}
else
{
throw "You must be an administrator to run this script."
}
}
If I run the script above, it successfully spawns another PowerShell instance with elevated privileges but the current working directory is lost and automatically set to C:\Windows\System32. Bound Parameters are also lost or incorrectly parsed.
After reading similar questions I learned that when using Start-Process with -Verb RunAs, the -WorkingDirectory argument is only honored if the target executable is a .NET executable. For some reason PowerShell 5 doesn't honor it:
The problem exists at the level of the .NET API that PowerShell uses behind the scenes (see System.Diagnostics.ProcessStartInfo), as of this writing (.NET 6.0.0-preview.4.21253.7).
Quote from this related question:
In practice - and the docs do not mention that - the -WorkingDirectory parameter is not respected if you start a process elevated (with administrative privileges, which is what -Verb RunAs - somewhat obscurely - does): the location defaults to $env:SYSTEMROOT\system32 (typically, C:\Windows\System32).
So the most common solution I've seen involves using -Command instead of -File. I.E:
Start-Process -FilePath powershell.exe -Verb Runas -ArgumentList '-Command', 'cd C:\ws; & .\script.ps1'
This looks really hack-ish but works. The only problem is I can't manage to get an implementation that can pass both bound and unbound parameters to the script being called via -Command.
I am trying my hardest to find the most robust implementation of self-elevation possible so that I can nicely wrap it into a function (and eventually into a module I'm working on) such as Request-AdminRights which can then be cleanly called immediately in new scripts that require admin privileges and/or escalation. Pasting the same auto-elevation code at the beginning of every script that needs admin rights feels really sloppy.
I'm also concerned I might be overthinking things, and to just leave elevation to the script level instead of wrapping it into a function.
Any input at all is greatly appreciated.
CodePudding user response：
The closest you can get to a robust, cross-platform self-elevating script solution that supports:
- both positional (unnamed) and named arguments
- while preserving type fidelity within the constraints of PowerShell's serialization (see this answer)
- preserving the caller's working directory.
- On Unix-like platforms only: synchronous, same-window execution with exit-code reporting (via the standard
sudoutility).
is the following monstrosity (I certainly wish this were easier):
- Note:
For (relative) brevity, I've omitted your
Test-IsUacEnabledtest, and simplified the test for whether the current session is already elevated to[bool] (net.exe session 2>$null)You can drop everything between
# --- BEGIN: Helper function for self-elevation.and# --- END: Helper function for self-elevation.into any script to make it self-elevating.- If you find yourself in repeated need of self-elevation, in different scripts, you can copy the code into your
$PROFILEfile or - better suited to wider distribution - convert the dynamic (in-memory) module used below (viaNew-Module) into a regular persisted module that your scripts can (auto-)load. With theEnsure-Elevatedfunction available available via an auto-loading module, all you need in a given script is to callEnsure-Elevated, without arguments (or with-Verbosefor verbose output).
- If you find yourself in repeated need of self-elevation, in different scripts, you can copy the code into your
# Sample script parameter declarations.
# Note: Since there is no [CmdletBinding()] attribute and no [Parameter()] attributes,
# the script also accepts *unbound* arguments.
param(
[object] $First,
[int] $Second,
[array] $Third
)
# --- BEGIN: Helper function for self-elevation.
# Define a dynamic (in-memory) module that exports a single function, Ensure-Elevated.
# Note:
# * In real life you would put this function in a regular, persisted module.
# * Technically, 'Ensure' is not an approved verb, but it seems like the best fit.
$null = New-Module -Name "SelfElevation_$PID" -ScriptBlock {
function Ensure-Elevated {
[CmdletBinding()]
param()
$isWin = $env:OS -eq 'Windows_NT'
# Simply return, if already elevated.
if (($isWin -and (net.exe session 2>$null)) -or (-not $isWin -and 0 -eq (id -u))) {
Write-Verbose "(Now) running as $(("superuser", "admin")[$isWin])."
return
}
# Get the relevant variable values from the calling script's scope.
$scriptPath = $PSCmdlet.GetVariableValue('PSCommandPath')
$scriptBoundParameters = $PSCmdlet.GetVariableValue('PSBoundParameters')
$scriptArgs = $PSCmdlet.GetVariableValue('args')
Write-Verbose ("This script, `"$scriptPath`", requires " ("superuser privileges, ", "admin privileges, ")[$isWin] ("re-invoking with sudo...", "re-invoking in a new window with elevation...")[$isWin])
# Note:
# * On Windows, the script invariably runs in a *new window*, and by design we let it run asynchronously, in a stay-open session.
# * On Unix, sudo runs in the *same window, synchronously*, and we return to the calling shell when the script exits.
# * -inputFormat xml -outputFormat xml are NOT used:
# * The use of -encodedArguments *implies* CLIXML serialization of the arguments; -inputFormat xml presumably only relates to *stdin* input.
# * On Unix, the CLIXML output created by -ouputFormat xml is not recognized by the calling PowerShell instance and passed through as text.
# * On Windows, the elevated session's working dir. is set to the same as the caller's (happens by default on Unix, and also in PS Core on Windows - but not in *WinPS*)
# Determine the full path of the PowerShell executable running this session.
# Note: The (obsolescent) ISE doesn't support the same CLI parameters as powershell.exe, so we use the latter.
$psExe = (Get-Process -Id $PID).Path -replace '_ise(?=\.exe$)'
if (0 -ne ($scriptBoundParameters.Count $scriptArgs.Count)) {
# ARGUMENTS WERE PASSED, so the CLI must be called with -encodedCommand and -encodedArguments, for robustness.
# !! To work around a bug in the deserialization of [switch] instances, replace them with Boolean values.
foreach ($key in @($scriptBoundParameters.Keys)) {
if (($val = $scriptBoundParameters[$key]) -is [switch]) { $null = $scriptBoundParameters.Remove($key); $null = $scriptBoundParameters.Add($key, $val.IsPresent) }
}
# Note: If the enclosings script is non-advanced, *both* $PSBoundParameters and $args may be populated, so we pass *both* through.
$serializedArgs = [System.Management.Automation.PSSerializer]::Serialize(($scriptBoundParameters, $scriptArgs), 1) # Use the same depth as the remoting infrastructure.
# The command that receives the (deserialized) arguments.
# Note: Since the new window running the elevated session must remain open, we do *not* append `exit $LASTEXITCODE`, unlike on Unix.
$cmd = 'param($bound, $positional) Set-Location "{0}"; & "{1}" @bound @positional' -f (Get-Location -PSProvider FileSystem).ProviderPath, $scriptPath
if ($isWin) {
Start-Process -Verb RunAs $psExe ('-noexit -encodedCommand {0} -encodedArguments {1}' -f [Convert]::ToBase64String([Text.Encoding]::Unicode.GetBytes($cmd)), [Convert]::ToBase64String([Text.Encoding]::Unicode.GetBytes($serializedArgs)))
}
else {
sudo $psExe -encodedCommand ([Convert]::ToBase64String([Text.Encoding]::Unicode.GetBytes($cmd))) -encodedArguments ([Convert]::ToBase64String([Text.Encoding]::Unicode.GetBytes($serializedArgs)))
}
}
else {
# NO ARGUMENTS were passed - simple reinvocation of the script with -c (-Command) is sufficient.
# Note: While -f (-File) would normally be sufficient, it leaves $args undefined, which could cause the calling script to break.
# Also, on WinPS we must set the working dir.
if ($isWin) {
Start-Process -Verb RunAs $psExe ('-noexit -c Set-Location "{0}"; & "{1}"' -f (Get-Location -PSProvider FileSystem).ProviderPath, $scriptPath)
}
else {
# Note: On Unix, the working directory is always automatically inherited.
sudo $psExe -c "& `"$scriptPath`"; exit $LASTEXITCODE"
}
}
# EXIT after reinvocation, passing the exit code through, if possible:
# On Windows, since Start-Process was invoked asynchronously, all we can report is whether *it* failed on invocation.
exit ($LASTEXITCODE, (1, 0)[$?])[$isWin]
}
}
# --- END: Helper function for self-elevation.
"Current location: $($PWD.ProviderPath)"
# Call the self-elevation helper function:
# * If this session is already elevated, the call is a no-op and execution continues,
# in the current console window.
# * Otherwise, the function exits the script and re-invokes it with elevation,
# passing all arguments through and preserving the working directory.
# * On Windows:
# * UAC will prompt for confirmation / adming credentials every time.
# * Of technical necessity, the elevated session runs in a *new* console window,
# asynchronously, and the window running the elevated session remains open.
# Note: The new window is a regular *console window*, irrespective of the
# environment you're calling from (including Windows Terminal, VSCode,
# or the (obsolescent) ISE).
# * Due to running asynchronously in a new window, the calling session won't know
# the elevated script call's exit code.
# * On Unix:
# * The `sudo` utility used for elevation will prompt for a password,
# and by default remember it for 5 minutes for repeat invocations.
# * The elevated script runs in the *current* window, *synchronously*,
# and $LASTEXITCODE reflects the elevated script's exit code.
# That is, the elevated script runs and returns control to the non-elevated caller.
# Note that $LASTEXITCODE is only meaningful if the elevated script
# sets its intentionally, via `exit $n`.
# Omit -Verbose to suppress verbose output.
Ensure-Elevated -Verbose
# For illustration:
# Print the arguments received in diagnostic form.
Write-Verbose -Verbose '== Arguments received:'
[PSCustomObject] @{
PSBoundParameters = $PSBoundParameters.GetEnumerator() | Select-Object Key, Value, @{ n='Type'; e={ $_.Value.GetType().Name } } | Out-String
# Only applies to non-advanced scripts
Args = $args | ForEach-Object { [pscustomobject] @{ Value = $_; Type = $_.GetType().Name } } | Out-String
CurrentLocation = $PWD.ProviderPath
} | Format-List
Sample call:
If you save the above code to file script.ps1 and invoke it as follows:
./script.ps1 -First (get-date) -Third ('foo', 'bar') -Second 42 @{ unbound=1 } 'last unbound'
you'll see the following:
In the non-elevated session, which triggers the UAC /
sudopassword prompt (Windows example):Current location: C:\Users\jdoe\sample VERBOSE: This script, "C:\Users\jdoe\sample\script.ps1", requires admin privileges, re-invoking in a new window with elevation...In the elevated session (which on Unix runs transiently in the same window):
VERBOSE: (Now) running as admin. VERBOSE: == Arguments received: PSBoundParameters : Key Value Type --- ----- ---- First 10/30/2021 12:30:08 PM DateTime Third {foo, bar} Object[] Second 42 Int32 Args : Value Type ----- ---- {unbound} Hashtable last unbound String CurrentLocation : C:\Users\jdoe\sample