6

I would like my Zsh prompt to display whether my sudo credentials are cached. What I have so far should help in explaining what I want to achieve.

function sudo-warning {
    if sudo -nl &>/dev/null; then
        echo -n " %{${fg[red]}%}🔓%{$reset_color%}"
    # optionally, show a locked lock if no sudo credentials active
    #else
    #    echo -n " %{${fg[blue]}%}🔒%{$reset_color%}"
    fi  
}

# Update prompt every 10 seconds
TMOUT=10
TRAPALRM() {
    zle reset-prompt
}

PROMPT='%n$(sudo-warning) '

The problem is that sudo -nl &>/dev/null updates the timestamp of the last sudo call, so no timeout is ever reached. So, is there a way to get retrieve information about whether sudo still has my credentials cached, without updating the timeout itself?

2

This seems to work for me to tell whether the timeout is reached:

sudo-expired() [[ $(
  trap "" XFSZ
  limit filesize 0
  LC_ALL=C sudo -n true 2>&1) = *"password is required" ]]

That is, set the filesize limit to 0 for the update of the timestamp file to fail, but as long as we don't let that limit kill sudo, we're still able to tell if a password was required or not.

Used like in yours (with a few simplifications):

sudo-warning()
  if sudo-expired; then
    echo '%F{blue}🔒%f'
  else
    echo '%F{red}🔓%f'
  fi

TMOUT=10
TRAPALRM() zle reset-prompt
set -o promptsubst
PS1='%n$(sudo-warning) '
  • This is a very nice and clever hack! The nice thing about limiting the file size is that no emails are sent out, even if mail_badpass is set. This works perfectly for me. However, this might also be considered a security issue. I’ll try to contact the developers about this. – timothymctim Jan 3 '18 at 14:14
  • @timothymctim, note that I've already contacted the sudo (and some distro) maintainers a few years back about the implications of changing the limits (and other process attributes like signal handler). – Stéphane Chazelas Jan 3 '18 at 14:18

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