---
layout: post
title: 'How to rickroll people that try to run "rm -rf" on your system'
date: 2016-07-28 16:00:00 +0200
categories: linux
---

<strong>
  WARNING: The method showed here could not prevent the actual execution of "rm
  -rf" if the "UNIX vandal" is clever enough. Proceed at your own risk, and make
  backups!
</strong>

<p>
  I like Rick Astley late 80's songs, and you can see them here in my Spotify:
</p>

<p>
  <img
    src="/images/spotify_rickastley.png"
    alt="My Spotify with a bunch of Rick Astley songs"
  />
</p>

<p>
  I like rickrolling people too, especially if they are trying to delete my
  entire
  <code>/home</code> directory or, even worse, <code>/</code>. Since I learned
  how to use the <code>alias</code> built-in, I wanted a way to prevent that
  random people tinkering with my laptop (that I may forgot to lock) could
  delete potentially important stuff, just for fun or boredom.
</p>

<p>
  The method that I will show will lock any <code>rm</code> command runned in
  both recursive and force mode, so <code>rm -rf</code>,
  <code>rm -f -r</code> and <code>rm -r --force</code> are all blocked, even if
  they are runned with <code>sudo</code>. I am going to alias the rm command in
  <code>/etc/profile</code>, <code>/etc/bash.bashrc</code> and in
  <code>/etc/zsh/zshrc</code> (I am a zsh user) so that the rickroll will be
  possible from all users, even root and the ones with a brand new
  <code>.bashrc</code> or <code>.zshrc</code>. Here is the code I appended to
  those files:
</p>

<p>
{% highlight bash %}
alias rm=/bin/rmAlias
alias sudo='sudo ' # this enables aliases in sudo, see http://askubuntu.com/q/22037/
{% endhighlight %}
</p>

<p>
  Since <code>alias</code> is not able to control the flags of the aliases (see
  <a
    href="http://apple.stackexchange.com/questions/50963/how-do-i-add-a-flag-to-an-alias"
    >here</a
  >, we are going to redirect each call of <code>rm</code> to
  <code>/bin/rmAlias</code>, that would run the command if it is safe. I did not
  use a function because it is a bit tricky to make that work with
  <code>sudo</code>. So, let's see the code I put in <code>rmAlias</code>:
</p>

<p>
{% highlight bash %}
#!/bin/bash # Rickroll whoever tries to desert this system, even root. 
# To achieve this, set the appropriate aliases even in /etc/profile and similars. 

# Video played when rickrolling: it's just Never Gonna Give You Up on my system,
# but be free to customize this! 
ROLLVIDEO=/opt/anti-rm/serious-video.mkv

rickroll() { 
    echo "Never gonna desert this system..."
    xdg-open $ROLLVIDEO 2>&1 & exit 0
}

while getopts ":rf-" opt; do 
    # Prevent '--force' to be detected as -r and -f
    if [ "$opt" = "-" ]; then 
        OPTIND=$OPTIND+1
        continue
    fi
    if [ "$opt" = "r" ] || [ "$opt" = "f" ]; then
        if [ "$tmp" = "" ]; then 
            tmp=$opt
            continue
        elif [ "$tmp" != "$opt" ]; then
            rickroll
        fi
    fi
done

for var in "$@" do
    if [[ "$var" = "--force" && "$tmp" = "r" ]]; then 
        rickroll 
    fi
done 

# If it's safe, just run rm 
/bin/rm "$@"
exit $? 
{% endhighlight %}
</p>

<p>
  It may look messy to a <em>UNIX</em> guy more experienced than me, but it
  works. The <code>getopts</code> built-in sees if both the <code>-r</code> and
  the <code>-f</code> flags are used and, if so, it starts
  <code>rickroll()</code>, which opens with <code>xdg-open</code> that amazing
  clip from <em>RickAstleyVEVO</em>. From line 30 and below, the script checks
  if the <code>--force</code> flag is used instead of <code>-f</code>.
</p>

<p>Let's give execution permissions to the script we have just created:</p>

<p>{% highlight bash %}chmod +x /bin/rmAlias{% endhighlight %}</p>

<p>
  Restart your shell, and enjoy. If you want to test safely, I suggest trying to
  run <code>rm -rf</code> with no folders or a nonexistant one, since this
  script stops even these commands.
</p>

<p>
  If you want even more security, you can rename this script to
  <code>/bin/rm</code> and move the original one in some other place, getting
  rid of all the aliases. I prefer the solution above because it's tidier: you
  haven't to move anything. In fact, this could be just an AUR package...
</p>