Can I mask an input text in a bat file?

Chathuranga Chandrasekara picture Chathuranga Chandrasekara · Mar 20, 2009 · Viewed 213.1k times · Source

I am writing a batch file to execute some other programs. In this case I need to prompt for a password. Do I have any way to mask the input text? I don't need to print ******* characters instead of input characters. Linux's Password prompt behavior (Print nothing while typing) is enough.

@echo off
SET /P variable=Password : 
echo %variable%
Pause

This will read the input but I can't mask the text using this approach.

Answer

unclemeat picture unclemeat · Dec 3, 2013

Yes - I am 4 years late.

But I found a way to do this in one line without having to create an external script; by calling powershell commands from a batch file.

Thanks to TessellatingHeckler - without outputting to a text file (I set the powershell command in a variable, because it's pretty messy in one long line inside a for loop).

@echo off
set "psCommand=powershell -Command "$pword = read-host 'Enter Password' -AsSecureString ; ^
    $BSTR=[System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($pword); ^
        [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR)""
for /f "usebackq delims=" %%p in (`%psCommand%`) do set password=%%p
echo %password%

Originally I wrote it to output to a text file, then read from that text file. But the above method is better. In one extremely long, near incomprehensible line:

@echo off
powershell -Command $pword = read-host "Enter password" -AsSecureString ; $BSTR=[System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($pword) ; [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR) > .tmp.txt & set /p password=<.tmp.txt & del .tmp.txt
echo %password%

I'll break this down - you can split it up over a few lines using caret ^, which is much nicer...

@echo off
powershell -Command $pword = read-host "Enter password" -AsSecureString ; ^
    $BSTR=[System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($pword) ; ^
        [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR) > .tmp.txt 
set /p password=<.tmp.txt & del .tmp.txt
echo %password%

This article explains what the powershell commands are doing; essentially it gets input using Read-Host -AsSecureString - the following two lines convert that secure string back into plain text, the output (plaintext password) is then sent to a text file using >.tmp.txt. That file is then read into a variable and deleted.