How do i encode powershell script to base64 UTF16-LE string using C#

Question

I want to encode a powershell script from string, but I can't get it to be encoded in UTF16-LE.

I am using this to encode it to base64 string.

string encodedscript = "powershell -nop -enc " + Convert.ToBase64String(Encoding.UTF8.GetBytes(PowerShellScript));

But when i try to use UTF16-LE encoding, it does not work, for example:

string encodedscript = "powershell -nop -enc " + Convert.ToBase64String(Encoding.UTF16-LE.GetBytes(PowerShellScript));

So my question is how do i encode Powershell script using c# so it will be acceptable by powershell.

I am trying to achieve something like on this website in C#: https://raikia.com/tool-powershell-encoder/

This is code example, the powershell script PowerShellScript is extremly long.

Here is some example encoded script: https://pastesite.org/view/raw/74b98937

Example script: https://pastesite.org/view/raw/b573f289

@Theo I keep getting this error: Program 'powershell.exe' failed to run: The filename or extension is too longAt line:1 char:1 + powershell -nop -enc DQAKACQAZwBHAEIATABkAHkAIAA9ACAAWwBTAHkAcwB0AGUA ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. At line:1 char:1 + powershell -nop -enc DQAKACQAZwBHAEIATABkAHkAIAA9ACAAWwBTAHkAcwB0AGUA ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : ResourceUnavailable: (:) [], ApplicationFailedException + FullyQualifiedErrorId : NativeCommandFailed — Speed Runer
– Speed Runer, Commented Nov 13, 2021 at 9:50
Also when i run from batch file i get this error: The system cannot execute the specified program. — Speed Runer
– Speed Runer, Commented Nov 13, 2021 at 9:53
If I compare the result of "Get-Date" in the link you gave (result RwBlAHQALQBEAGEAdABlAA==) to PowerShell [Convert]::ToBase64String([System.Text.Encoding]::Unicode.GetBytes("Get-Date")) it gives me an equal result. That would mean in C# Convert.ToBase64String(Encoding.Unicode.GetBytes(PowerShellScript)) would do the same I guess ? See also this answer — Theo
– Theo, Commented Nov 13, 2021 at 10:26
Please show a complete, minimal code sample, that we can use to try and reproduce the issue. We don't know what PowerShellScript is, if and how you read it from disk and so on. — zett42
– zett42, Commented Nov 13, 2021 at 10:49

Speed Runer · Accepted Answer · 2021-11-14 21:28:51Z

2

Ok thanks everyone, for helping me out, i came out with this batch script which relaunches it self as powershell script, still yet working. But it shows error at start. I am suppressing it with && cls

#^ &@@Echo Off && Cls && Powershell -exec bypass -nop -noni - < "%~f0" && exit /B
#POWERSHELL CODE GOES HERE!

answered Nov 14, 2021 at 21:28

Speed Runer

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2 Comments

TessellatingHeckler Over a year ago

That is a pretty cool approach! Reminds me I have answered a question like it for a script which is both Bash shell and PowerShell , but I hadn't thought of anything like that for this use case.

Speed Runer Over a year ago

@TessellatingHeckler Thanks!

Adam Stephenson · Accepted Answer · 2022-08-08 21:34:10Z

0

You want to first encode to Unicode then to Base64.

public class Powershell
{
    public static string Command(string command)
    {
        var plainTextBytes = Encoding.Unicode.GetBytes(command);
        var encodedCommand = Convert.ToBase64String(plainTextBytes);

        return $"powershell.exe -EncodedCommand {encodedCommand}";
    }
}

edited Aug 8, 2022 at 21:34

answered Aug 8, 2022 at 21:33

Adam Stephenson

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