Command Encoded in Powershell FAIL - powershell

Question

I discovered that the command uncoded bad, but I do not understand what is wrong:
My Code :
$command = "(New-Object System.Net.WebClient).DownloadFile('http://localhost/update_program.exe','updater.exe'); Start-Process 'updater.exe'"
$bytes = [Text.Encoding]::Unicode.GetBytes($command)
$encodedCommand = [Convert]::ToBase64String($bytes)
echo $encodedCommand
Return
KABOAGUAdwAtAE8AYgBqAGUAYwB0ACAAUwB5AHMAdABlAG0ALgBOAGUAdAAuAFcAZQBiAEMAbABpAGU
AbgB0ACkALgBEAG8AdwBuAGwAbwBhAGQARgBpAGwAZQAoACcAaAB0AHQAcAA6AC8ALwBsAG8AYwBhAG
wAaABvAHMAdAAvAHUAcABkAGEAdABlAF8AcAByAG8AZwByAGEAbQAuAGUAeABlACcALAAnAHUAcABkA
GEAdABlAHIALgBlAHgAZQAnACkAOwAgAFMAdABhAHIAdAAtAFAAcgBvAGMAZQBzAHMAIAAnAHUAcABk
AGEAdABlAHIALgBlAHgAZQAnAA==
I try :
powershell -encodedCommand KABOAGUAdwAtAE8AYgBqAGUAYwB0ACAAUwB5AHMAdABlAG0ALgBOAGUAdAAuAFcAZQBiAEMAbABpAGUAbgB0ACkALgBEAG8AdwBuAGwAbwBhAGQARgBpAGwAZQAoACcAaAB0AHQAcAA6AC8ALwBsAG8AYwBhAGwAaABvAHMAdAAvAHUAcABkAGEAdABlAF8AcAByAG8AZwByAGEAbQAuAGUAeABlACcALAAnAHUAcABkAGEAdABlAHIALgBlAHgAZQAnACkAOwAgAFMAdABhAHIAdAAtAFAAcgBvAGMAZQBzAHMAIAAnAHUAcABkAGEAdABlAHIALgBlAHgAZQAnAA==
Return :
Editor's note: The symptom below is inconsistent with the code above, which is correct. There may not be a problem left to solve.
Missing expression after unary operator '-'.
In line: 1 Character: 2
+ - < <<< encodeCommand KABOAGUAdwAtAE8AYgBqAGUAYwB0ACAAUwB5AHMAdABlAG0ALgBOAGUA
dAAuAFcAZQBiAEMAbABpAGUAbgB0ACkALgBEAG8AdwBuAGwAbwBhAGQARgBpAGwAZQAoACcAaAB0AHQ
AcAA6AC8ALwBsAG8AYwBhAGwAaABvAHMAdAAvAHUAcABkAGEAdABlAF8AcAByAG8AZwByAGEAbQAuAG
UAeABlACcALAAnAHUAcABkAGEAdABlAHIALgBlAHgAZQAnACkAOwAgAFMAdABhAHIAdAAtAFAAcgBvA
GMAZQBzAHMAIAAnAHUAcABkAGEAdABlAHIALgBlAHgAZQAnAA==
+ CategoryInfo : ParserError: (-:String) [], ParentContainsErrorR
ecordException
+ FullyQualifiedErrorId : MissingExpressionAfterOperator
Because my command coded fails?

Answer 1

Okay, new answer as the question has changed quite drastically.
Try
#Encode Command
$command = "(New-Object System.Net.WebClient).DownloadFile('http://localhost/update_program.exe','updater.exe'); Start-Process 'updater.exe'"
$bytes = [Text.Encoding]::Unicode.GetBytes($command)
$encodedCommand = [Convert]::ToBase64String($bytes)
echo $encodedCommand
#Execute command
powershell.exe -EncodedCommand $encodedcommand
This should work so long as the statements in $command are correct.

Answer 2

Sorry, I think I misunderstood your question at first. I think you were trying to ask how to stop Powershell from executing the string you assign to $command. If so then try the following code
powershell -command {
$command = [string] $null; $command += '(New-Object System.Net.WebClient).DownloadFile(';
$command += "'http://localhost/update_program.exe','updater.exe') ;
Start-Process 'updater.exe'"; $bytes = [Text.Encoding]::Unicode.GetBytes($command);
$encodedCommand = [Convert]::ToBase64String($bytes); echo $encodedCommand
}
Microsoft wanted smart processing of variables to enable greater compatibility between variables and functions. I think it got confused when parsing your command. What I tried was to break up the string assignation so that Powershell didn't assume that the string was a set of instructions. The single statement above calls Powershell, assigns a null string to $command, twice concatenates with strings which Powershell cannot confuse and then outputs $encodedCommand at the end. Is this what you were after?