129 lines
4.1 KiB
HTML
129 lines
4.1 KiB
HTML
---
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layout: post
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title: "How to rickroll people that try to run \"rm -rf\" on your system"
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date: 2016-07-28 16:00:00 +0200
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categories: linux
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---
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<strong>
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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!
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</strong>
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<p>
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I like Rick Astley late 80's songs, and you can see them here in my Spotify:
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</p>
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<p>
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<img
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src="/images/spotify_rickastley.png"
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alt="My Spotify with a bunch of Rick Astley songs">
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</p>
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<p>
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I like rickrolling people too, especially if they are trying to delete my entire
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<code>/home</code> directory or, even worse, <code>/</code>. Since I learned
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how to use the <code>alias</code> built-in, I wanted a way to prevent that
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random people tinkering with my laptop (that I may forgot to lock) could
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delete potentially important stuff, just for fun or boredom.
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</p>
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<p>
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The method that I will show will lock any <code>rm</code> command runned in
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both recursive and force mode, so <code>rm -rf</code>, <code>rm -f -r</code>
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and <code>rm -r --force</code> are all blocked, even if they are runned with
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<code>sudo</code>. I am going to alias the rm command in
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<code>/etc/profile</code>, <code>/etc/bash.bashrc</code> and in
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<code>/etc/zsh/zshrc</code> (I am a zsh user) so that the rickroll will be
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possible from all users, even root and the ones with a brand new
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<code>.bashrc</code> or <code>.zshrc</code>. Here is the code I appended to
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those files:
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</p>
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<p>
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{% highlight bash %}
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alias rm=/bin/rmAlias
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alias sudo='sudo ' # this enables aliases in sudo, see http://askubuntu.com/questions/22037/aliases-not-available-when-using-sudo
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{% endhighlight %}
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</p>
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<p>
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Since <code>alias</code> is not able to control the flags of the aliases (see
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<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
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<code>/bin/rmAlias</code>, that would run the command if it is safe. I did
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not use a function because it is a bit tricky to make that work with
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<code>sudo</code>. So, let's see the code I put in <code>rmAlias</code>:
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</p>
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<p>
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{% highlight bash %}
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#! /bin/bash
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# Rickroll whoever tries to desert this system, even root.
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# To achieve this, set the appropriate aliases even in /etc/profile and similars.
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# Video played when rickrolling
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ROLLVIDEO=/opt/anti-rm/serious-video.mkv # it's just Never Gonna Give You Up on my system, but be free to customize this!
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rickroll(){
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echo "Never gonna desert this system..."
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xdg-open $ROLLVIDEO 2>&1 &
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exit 0
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}
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while getopts ":rf-" opt; do
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# Prevent '--force' to be detected as -r and -f
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if [ "$opt" = "-" ]; then
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OPTIND=$OPTIND+1
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continue
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fi
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if [ "$opt" = "r" ] || [ "$opt" = "f" ]; then
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if [ "$tmp" = "" ]; then
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tmp=$opt
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continue
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elif [ "$tmp" != "$opt" ]; then
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rickroll
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fi
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fi
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done
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for var in "$@"
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do
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if [[ "$var" = "--force" && "$tmp" = "r" ]]; then
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rickroll
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fi
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done
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# If it's safe, just run rm
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/bin/rm "$@"
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exit $?
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{% endhighlight %}
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</p>
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<p>
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It may look messy to a <em>UNIX</em> guy more experienced than me, but it
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works. The <code>getopts</code> built-in sees if both the <code>-r</code> and
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the <code>-f</code> flags are used and, if so, it starts
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<code>rickroll()</code>, which opens with <code>xdg-open</code> that amazing
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clip from <em>RickAstleyVEVO</em>. From line 30 and below, the script checks
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if the <code>--force</code> flag is used instead of <code>-f</code>.
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</p>
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<p>
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Let's give execution permissions to the script we have just created:
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</p>
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<p>
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{% highlight bash %}
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# chmod +x /bin/rmAlias
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{% endhighlight %}
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</p>
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<p>
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Restart your shell, and enjoy. If you want to test safely, I suggest trying
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to run <code>rm -rf</code> with no folders or a nonexistant one, since this
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script stops even these commands.
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</p>
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<p>
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If you want even more security, you can rename this script to
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<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...
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</p>
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