Askpass Implementation For Doas

posted on 2021-01-20 by Chris Noxz

As I was trying to move away from using sudo to instead be using doas, mostly due to recent security concerns, I had yet to find any solution for the missing ASKPASS functionality. So instead of creating a fork of doas that I would have to maintain, I instead found a quite obvious solution using expect and tcl. I wrote this short script which in its current state have a pseudo dependency of dmenu.

#!/usr/bin/expect --

# askpass implementation for doas
# example usage: DOAS_ASKPASS="dmenu -P -p password:" doas_askpass echo working

# don't mind the man behind the curtain
log_user 0

# no command, then nothing to do
if { $argc == 0 } { exit 0 }

# treat all arguments as command input
set cmd [lrange $argv 0 end];

# read askpass from env or fallback to dmanu_pass ()
if {[info exists ::env(DOAS_ASKPASS)]} {
	set askpass "$::env(DOAS_ASKPASS)"
} else {
	set askpass "dmenu_pass password:"
}

# read password from user
set pwd [exec {*}$askpass]

# spawn doas operation
spawn doas {*}$cmd

# send password and execute command
expect "doas*password:" {
	send -- "$pwd\r"
	expect \r
	log_user 1
	expect eof
}

Of course, feel free to use it if you have similar needs.