How to execute Base64 encoded powershell function?

Question

I have function like this (test.ps1):

function HLS {
    Write-Host 'Hello, World!'
}

I execute this commands in PS window:

$expression = Get-Content -Path .\test.ps1
$commandBytes = [System.Text.Encoding]::Unicode.GetBytes($expression)
$encodedCommand = [Convert]::ToBase64String($commandBytes)
powershell -EncodedCommand $encodedCommand

It does not give me any output, which is good because i would need to execute this function. After trying to execute this command:

PS C:\truncated> HLS

It gives me error:

HLS : The term 'HLS' is not recognized as the name of a cmdlet, function, script file, or operable program.

Does anyone know how to execute function that is passed as -EncodedCommand parameter?

Why not simply dot source your .\test.ps1 ?? By running powershell -EncodedCommand $encodedCommand, the script will use its own environment and the caller script will have no knowledge about that. — Theo
– Theo, Commented Mar 19, 2022 at 12:56
Becasue I need to execute it as base64 without touching the disk — Boże Bożenka
– Boże Bożenka, Commented Mar 19, 2022 at 12:59
..but you are touching the disk here: $expression = Get-Content -Path .\test.ps1 — Theo
– Theo, Commented Mar 19, 2022 at 13:00
IT is just for now, later the base64 will be embedded in command. $expression = Get-Content -Path .\test.ps1 is just temporary — Boże Bożenka
– Boże Bożenka, Commented Mar 19, 2022 at 13:00

mklement0 · Accepted Answer · 2022-03-19 15:12:40Z

Continuing from our comments.

If what you want is to embed just the base64 packed code block in your script, you should not use powershell -EncodedCommand $encodedCommand, because that will simply run in its own environment and your main script will know nothing about the function defined there.

For that you can use Invoke-Expression, but do read the Warning

$expression     = Get-Content -Path .\test.ps1
$commandBytes   = [System.Text.Encoding]::Unicode.GetBytes($expression)
$encodedCommand = [Convert]::ToBase64String($commandBytes)

# output the $encodedCommand so you can use it in the main script later:
$encodedCommand

Result:

ZgB1AG4AYwB0AGkAbwBuACAASABMAFMAIAB7AA0ACgAgACAAIAAgAFcAcgBpAHQAZQAtAEgAbwBzAHQAIAAnAEgAZQBsAGwAbwAsACAAVwBvAHIAbABkACEAJwANAAoAfQA=

Next, in your main script, use the base64 value of $encodedCommand directly:

$encodedCommand = 'ZgB1AG4AYwB0AGkAbwBuACAASABMAFMAIAB7AA0ACgAgACAAIAAgAFcAcgBpAHQAZQAtAEgAbwBzAHQAIAAnAEgAZQBsAGwAbwAsACAAVwBvAHIAbABkACEAJwANAAoAfQA='
Invoke-Expression ([System.Text.Encoding]::Unicode.GetString([convert]::FromBase64String($encodedCommand)))
# now the function is known and can be used
HLS

Result:

Hello, World!

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