curl https://some-url/ | sh

I see this all over the place nowadays, even in communities that, I would think, should be security conscious. How is that safe? What’s stopping the downloaded script from wiping my home directory? If you use this, how can you feel comfortable?

I understand that we have the same problems with the installed application, even if it was downloaded and installed manually. But I feel the bar for making a mistake in a shell script is much lower than in whatever language the main application is written. Don’t we have something better than “sh” for this? Something with less power to do harm?

  • zygo_histo_morpheus@programming.dev
    1·
    11 months ago

    You have the option of piping it into a file instead, inspecting that file for yourself and then running it, or running it in some sandboxed environment. Ultimately though, if you are downloading software over the internet you have to place a certain amount of trust in the person your downloading the software from. Even if you’re absolutely sure that the download script doesn’t wipe your home directory, you’re going to have to run the program at some point and it could just as easily wipe your home directory at that point instead.

  • Undaunted@feddit.org
    0·
    11 months ago

    You shouldn’t install software from someone you don’t trust anyway because even if the installation process is save, the software itself can do whatever it has permission to.

    “So if you trust their software, why not their install script?” you might ask. Well, it is detectable on server side, if you download the script or pipe it into a shell. So even if the vendor it trustworthy, there could be a malicious middle man, that gives you the original and harmless script, when you download it, and serves you a malicious one when you pipe it into your shell.

    And I think this is not obvious and very scary.

    • FizzyOrange@programming.dev
      01·
      11 months ago

      it is detectable on server side, if you download the script or pipe it into a shell

      Irrelevant. This is just an excuse people use to try and win the argument after it is pointed out to them that there’s actually no security issue with curl | bash.

      It’s waaaay easier to hide malicious code in a binary than it is in a Bash script.

      You can still see the “hidden” shell script that is served for Bash - just pipe it through tee and then into Bash.

      Can anyone even find one single instance of that trick ever actually being used in the wild (not as a demo)?

      • Undaunted@feddit.org
        1·
        11 months ago

        I never tried to win any argument. Hell I was not even aware that I’m participating in one. I just wanted to share the info, that even if the vendor is absolutely trustworthy and even if you validated the script by downloading and looking at it, there’s still another hole that’s not obvious to see.

        Yes it’s unlikely, but again, I never said it were. There are also arguments you can run curl with, to tell it to do the download first and then push it through the pipe afterwards, though I don’t know them by heart now.

        It won’t cost you anything to set those parameters, when you insist to use curl | bash, just in the off chance that someone’s trying to do what I mentioned.

        But I’m also someone who usually validates their downloads with a checksum so maybe I’m just weird. Who knows.