Can I mask an input text in a bat file

Question

I am writing a batch file for 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 behaviour (Print nothing while typing) is enough.

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

This will read the input but I cant mask the text using this approach.

Answer 1

You may use ReadFormattedLine subroutine for all kind of formatted input. For example, the command below read a password of 8 characters, display asterisks in the screen, and continue automatically with no need to press Enter:

call :ReadFormattedLine password="********" /M "Enter password (8 chars): "

This subroutine is written in pure Batch so it does not require any additional program, and it allows several formatted input operations, like read just numbers, convert letters to uppercase, etc. You may download ReadFormattedLine subroutine from Read a line with specific format.

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EDIT 2018-08-18: New method to enter an "invisible" password

The FINDSTR command have a strange bug that happen when this command is used to show characters in color AND the output of such a command is redirected to CON device. For details on how use FINDSTR command to show text in color, see this topic.

When the output of this form of FINDSTR command is redirected to CON, something strange happens after the text is output in the desired color: all the text after it is output as "invisible" characters, although a more precise description is that the text is output as black text over black background. The original text will appear if you use COLOR command to reset the foreground and background colors of the entire screen. However, when the text is "invisible" we could execute a SET /P command, so all characters entered will not appear on the screen.

@echo off
setlocal

set /P "=_" < NUL > "Enter password"
findstr /A:1E /V "^$" "Enter password" NUL > CON
del "Enter password"
set /P "password="
cls
color 07
echo The password read is: "%password%"

Answer 2

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.