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?
For security reasons, I review every line of code before it’s executed on my machine.
Before I die, I hope to take my ‘93 dell optiplex out of its box and finally see what this whole internet thing is about.
Not good enough. You should really be inspecting your CPU with a microscope.
It isn’t more dangerous than running a binary downloaded from them by any other means. It isn’t more dangerous than downloaded installer programs common with Windows.
TBH macOS has had the more secure idea of by default using sandboxes applications downloaded directly without any sort of installer. Linux is starting to head in that direction now with things like Flatpak.
If you’re worried, download it into a file first and read it.
What’s stopping the downloaded script from wiping my home directory?
You could just read the script file first… Or YOLO trust it like you trust any file downloaded from a relatively safe source… At least you can read a script.
| shstands for shake head at bad practicesAnd don’t forget to
sudo!Yeah I hate this stuff too, I usually pipe it into a file figure out what it’s doing and manually install the program from there.
FWIW I’ve never found anything malicious from these scripts but my internal dialogue starts screaming when I see these in the wild, I don’t want to run some script and not know what it’s touching malicious or not it’s a PITA.
As a linux user, I like to know what’s happening under the hood as best I can and these scripts go against that
I don’t cringe. Just instinctively
Ctrl+WYou 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.
All the software I have is downloaded from the internet…
You should try downloading the software from your mind brain, like us elite hackers do it. Just dump the binary from memory into a txt file and exe that shit, playa!
You should start getting it from CD-roms, that shit you can trust
I got my software from these free USB sticks I found in the parking lot.
Ah, you’re one of my users
It is kind of cool, when you’ve actually written your own software and use that. But realistically, I’m still getting the compiler from the internet…
Steady on Buck Rogers, what is this, 2025!?
Indeed, looking at the content of the script before running it is what I do if there is no alternative. But some of these scripts are awfully complex, and manually parsing the odd bash stuff is a pain, when all I want to know is : 1) what URL are you downloading stuff from? 2) where are you going to install the stuff?
As for running the program, I would trust it more than a random deployment script. People usually place more emphasis on testing the former, not so much the latter.
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.
That’s not what projects recommend though. Many recommend piping the output of an HTTP transfer over the public Internet directly into a shell interpreter. Even just
curl https://... > install.sh; sh install.shwould be one step up. The absolute minimum recommendation IMHO should be
curl https://... > install.sh; less install.sh; sh install.shbut this is still problematic.
Ultimately, installing software is a labourious process which requires care, attention and the informed use of GPG. It shouldn’t be simplified for convenience.
Also, FYI, the word “option” implies that I’m somehow restricted to a limited set of options in how I can use my GNU/Linux computer which is not the case.
Showing people that are running curl piped to bash the script they are about to run doesn’t really accomplish anything. If they can read bash and want to review the script then they can by just opening the URL, and the people that aren’t doing that don’t care what’s in the script, so why waste their time with it?
Do you think most users installing software from the AUR are actually reading the pkgbuilds? I’d guess it’s a pretty small percentage that do.
Showing people that are running curl piped to bash the script they are about to run doesn’t really accomplish anything. If they can read bash and want to review the script then they can by just opening the URL
What it accomplishes is providing the instructions (i.e. an easily copy-and-pastable terminal command) for people to do exactly that.
If you can’t review a bash script before running it without having an unnecessarily complex one-liner provided to you to do so, then it doesn’t matter because you aren’t going to be able to adequately review a bash script anyway.
If you can’t review a bash script before running it without having an unnecessarily complex one-liner provided to you
Providing an easily copy-and-pastable one-liner does not imply that the reader could not themselves write such a one-liner.
Having the capacity to write one’s own commands doesn’t imply that there is no value in having a command provided.
unnecessarily complex
LOL
I don’t think you realize that if your goal is to have a simple install method anyone can use, even redirecting the output to install.sh like in your examples is enough added complexity to make it not work in some cases. Again, those are not made for people that know bash.
even redirecting the output to install.sh like in your examples is enough added complexity to make it not work in some cases
You can’t have any install method that works in all cases.
if your goal is to have a simple install method anyone can use
Similarly, you can’t have an install method anyone can use.
I mean if you think that it’s bad for linux culture because you’re teaching newbies the wrong lessons, fair enough.
My point is that most people can parse that they’re essentially asking you to run some commands at a url, and if you have even a fairly basic grasp of linux it’s easy to do that in whatever way you want. I don’t know if I personally would be any happier if people took the time to lecture me on safety habits, because I can interpret the command for myself.
curl https://some-url/ | shis terse and to the point, and I know not to take it completely literally.linux culture
snigger
you’re teaching newbies the wrong lessons
The problem is not that it’s teaching bad lessons, it’s that it’s actually doing bad things.
most people can parse that they’re essentially asking you to run some commands at a url
I know not to take it completely literally
Then it needn’t be written literally.
I think you’re giving the authors of such installation instructions too much credit. I think they intend people to take it literally. I think this because I’ve argued with many of them.
Who the fuck types out “snigger” haha
Teleports behind you
deleted by creator
What’s stopping the downloaded script from wiping my home directory?
What’s stopping any Makefile, build script, or executable from running
rm -rf ~? The correct answer is “nothing”. PPAs are similarly open, things are a little safer if you only use your distro’s default package sources, but it’s always possible that a program will want to be able to delete something in your home directory, so it always has permission.Containerized apps are the only way around this, where they get their own home directory.
Don’t forget your package manager, running someone’s installer as root
It’s roughly the same state as when windows vista rolled out UAC in 2007 and everything still required admin rights because that’s just how everything worked…but unlike Microsoft, Linux distros never did the thing of splitting off installs into admin vs unprivileged user installers.
plenty of package managers have.
flatpak doesn’t require any admin to install a new app
nixos doesn’t run any code at all on your machine for just adding a package assuming it’s already been cached. if it hasn’t been cached it’s run in a sandbox. the cases other package managers use post install configuration scripts for are a different mechanism which possibly has root access depending on what it is.
Gonna ignore nix since they have two users, but flatpak is fair. However flatpak is a sandboxing scheme which is distinct from per-user installs. In many cases it can be the better route but not always. I think the reason it’s popular on Linux is also the dll hell problem.
idk if 2 users is fair, it may just be my circles but I see nixos mentioned more than almost anything else on lemmy/hn/etc in the past couple years
This is simpler than the download, ./configure, make, make install steps we had some decades ago, but not all that different in that you wind up with arbitrary, unmanaged stuff.
Preferably use the distro native packages, or else their build system if it’s easily available (e.g. AUR in Arch)
I think safer approach is to:
- Download the script first, review its contents, and then execute.
- Ensure the URL uses HTTPS to reduce the risk of man-in-the-middle attacks
If steam accidentally deleted someone’s home directory in a bash script via a single error, I doubt I would catch that one myself.
Ah yes for all of the bash experts who understand what they are reading.
If you’ve downloaded and audited the script, there’s no reason to pipe it from curl to sh, just run it. No https necessary.
The https is to cover the factthat you might have missed something.
I guess I download and skim out of principle, but they might have hidden something in there.
Wat. All https does is encrypt the connection when downloading. If you’ve already downloaded the file to audit it, then it’s in your drive, no need to use curl to download it again and then pipe it to sh. Just click the thing.
Yeah, https was for downloading it in the first place. My bad, I didn’t get my thoughts out in the right order.
That makes sense. I probably should have gotten it from context.
Install scripts are bad in general. ideally use officially packaged software.
But then they’d have to lay some guy 15$ to package it and thats like, spending money
Distros do the packaging. Devs can not be trusted
That’s how you end up without software.
That’s how you end up with a secure well tested system. Having the distro do software reviews adds another level of validation. Devs are bad about shipping software with vulnerable dependencies and stuff like that.
And then you install wordpress, lol.
Loads of distros have user packing like arch and nixos… also many distors accept donations to package your software either way so my point stands even then.
Meanwhile nix install instructions start of with a curl
?
the instructions for installing on not nixos https://nixos.org/download/
What part is confusing you?
Key being reduce. Https doesn’t protect from loads of attacks. Best to verify the sig.
If its not signed, open a bug report
Saved that, thank you.
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.
it is detectable […] server side, if you download the script [vs] pipe it into a shell
I presume you mean if you download the script in a browser, vs using curl to retrieve it, where presumably you are piping it to a shell. Because yeah, the user agent is going to reveal which tool downloaded it, of course. You can use curl to simply retrieve the file without executing it though.
Or are you suggesting that curl makes something different in its request to the server for the file, depending on whether it is saving the file to disk vs streaming it to a pipe?
It is actually a passive detection based of the timing of the chunk requests. Because curl by default will only request new chunks when the buffer is freed by the shell executing the given commands. This then can be used to detect that someone is not merely downloading but simultaneously executing it. Here’s a writeup about it:
You can also find some proof-of-concept implementations online to try it out yourself.
Wow, thanks for this. That is very helpful context. And thanks for your original post too, or I’d never have asked.
Oh, you’re welcome, kind person :)
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
teeand then into Bash.Can anyone even find one single instance of that trick ever actually being used in the wild (not as a demo)?
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.
