Show HN: Vet – A tool for safely running remote shell scripts

1. a10r ◴[28 Jun 25 19:57 UTC] No.44407666[source]▶

Hi HN, I'm the creator of `vet`. I've always been a bit nervous about the `curl | bash` pattern, even for trusted projects. It feels like there's a missing safety step. I wanted a tool that would show me a diff if a script changed, run it through `shellcheck`, and ask for my explicit OK before executing. That's why I built `vet`.

The install process itself uses this philosophy - I encourage you to check the installer script before running it!

I'd love to hear your feedback.

The repo is at https://github.com/vet-run/vet

replies(4): >>44409415 #>>44410454 #>>44410724 #>>44412363 #

2. __MatrixMan__ ◴[29 Jun 25 00:45 UTC] No.44409415[source]▶

>>44407666 (TP) #

I'm glad to see that I'm not the only person worried about this. It's a pretty glaring bit of attack surface if you ask me. I chuckled when I saw you used nvm as an example in your readme. I've pestered nvm about this sort of thing in the past (https://github.com/nvm-sh/nvm/issues/3349).

I'm a little uncertain about your threat model though. If you've got an SSL-tampering adversary that can serve you a malicious script when you expected the original, don't you think they'd also be sophisticated enough to instead cause the authentic script to subsequently download a malicious payload?

I know that nobody wants to deal with the headaches associated with keeping track of cryptographic hashes for everything you receive over a network (nix is, among other things, a tool for doing this). But I'm afraid it's the only way to actually solve this problem:

1. get remote inputs, check against hashes that were committed to source control

2. make a sandbox that doesn't have internet access

3. do the compute in that sandbox (to ensure it doesn't phone home for a payload which you haven't verified the hash of)

replies(1): >>44410382 #

3. charcircuit ◴[29 Jun 25 04:36 UTC] No.44410382[source]▶

>>44409415 #

Vet only downloads once, so what do you mean by subsequent download?

Also hashing on inputs is brittle and will break anytime the developer pushes an update. You want to trust their certificate instead.

replies(1): >>44413583 #

4. geocar ◴[29 Jun 25 04:55 UTC] No.44410454[source]▶

>>44407666 (TP) #

> I wanted a tool that would show me a diff if a script changed, run it through `shellcheck`

Why? What exactly do you think "shellcheck" does? When do you think you're diffing and what do you think you are diffing with?

> and ask for my explicit OK before executing.

But to what end? You're not better informed by what the script does with this strategy.

A small shell script like yours I can read in a minute and decide it does nothing for me, but large installers can be hard to decipher since they are balancing bandwidth costs with compatibility, and a lot of legitimate techniques can make this hard to follow without care and imagination.

> The install process itself uses this philosophy - I encourage you to check the installer script before running it!

I don't understand what philosophy you're talking about.

I think you're doing the exact same thing that malicious attackers do, you're just doing it worse:

    $ wget -qO- https://getvet.sh
    --2025-06-29 05:22:26--  https://getvet.sh/
    Resolving getvet.sh (getvet.sh)... 2a06:98c1:3120::5, 2a06:98c1:3121::5, 188.114.97.5, ...
    Connecting to getvet.sh (getvet.sh)|2a06:98c1:3120::5|:443... connected.
    HTTP request sent, awaiting response... 200 OK
    Length: unspecified [text/html]
    Saving to: ‘STDOUT’

    <!DOCTYPE html>
    <html lang="en">
    <head>
      <meta charset="UTF-8" />

I mean your script knows about wget, but your server doesn't. Sad. I also think you should be telling people to pull "https://github.com/vet-run/vet/blob/main/scripts/install.sh" instead of trying to be cute, but that's just me.

> I'd love to hear your feedback.

You're getting it: I think your program sucks, but I also like the idea of trying to do something, and I understand you just don't have any idea what to do or what the problem actually is.

So let me teach you a little bash:

    check () {
        echo "> $BASH_COMMAND" >&2
        echo -n "Allow? (yes/no) " >&2
        select c in yes no
        do
            if [ "$c" = "yes" ]
            then break
            elif [ "$c" = "no" ]
            then return 1
            fi
        done
    }

    shopt -s extdebug
    trap check DEBUG

This little scriptlet will wait until bash tries to run something, and ask before proceeding. Simples. Put this in front of an installer (or something else messy) and get step-by-step confirmation of what's going on. Something like this is in the BASH manual someplace, or was once upon a time.

In a large script this might annoy people, so if it were me, I would have a whitelist of commands that I think are safe, or maybe a "remember" option that updates that script. I might also have a blacklist for things like sudo.

While I'm on the subject of sudo, a nasty trick bad guys use is get you to run sudo on something innocuous and then rely on the cached credentials to run a sneaky (silent) sudo in the same session. Running sudo -k before interacting with an unknown program can help tremendously with this.

replies(1): >>44412560 #

5. BaudouinVH ◴[29 Jun 25 06:22 UTC] No.44410724[source]▶

>>44407666 (TP) #

The idea is great. Vet will work for people who can run the code displayed. Right now my skills are not high enough. Unsure wether I sit with the majority or minority of future users.

My 2 cents

6. subjectsigma ◴[29 Jun 25 11:54 UTC] No.44412363[source]▶

>>44407666 (TP) #

I appreciate you finding a problem and trying to build a solution, but I think your solution will not work very well. Shellcheck is not a virus or vulnerability scanner, it’s not designed for the thing you are using it for.

replies(1): >>44413234 #

7. a10r ◴[29 Jun 25 12:29 UTC] No.44412560[source]▶

>>44410454 #

Wow, thank you for taking the time to write such a detailed and in-depth critique.

First, let me address the bugs you found, because you were 100% right. The wget user-agent issue revealed a significant and regrettable flaw in the server-side logic. Thanks to your report, a fix has already been merged and deployed.

The installer also had a conceptual flaw in its security recommendation, as you and others pointed out. The documentation has been updated to recommend a two-step "download, then execute" process and now includes a direct link to the GitHub release asset for maximum transparency—no more "cute" domain magic as the primary method.

Your trap DEBUG suggestion is a really powerful technique, and it highlights a core philosophical difference in how to approach this problem:

Your approach is an "In-Flight Monitor"—it steps through an executing script and asks for permission at each step. It's fantastic for deep, real-time analysis.

vet's approach is a "Pre-Flight Check"—its goal is to let a human review and approve a complete, static snapshot of a script before a single line of it ever executes.

I chose the "pre-flight" path because diffing and shellcheck are central to the idea. They answer the questions: "I trusted this script last month, but has it changed at all since then?" and "Does this static code contain any obvious red flags?"

The trap DEBUG method is powerful, but it can't answer that "what's changed?" question upfront and runs the risk of "prompt fatigue" on large installers, where a user might just start hitting 'y' to get through it.

You've given me a lot to think about, especially on how to better articulate this philosophy. I sincerely appreciate you taking the time to teach and challenge the project. This is the kind of tough, expert feedback that makes open source better, and you've already had a direct, positive impact on it.

8. a10r ◴[29 Jun 25 14:00 UTC] No.44413234[source]▶

>>44412363 #

You are absolutely right, and that's a crucial distinction to make. ShellCheck is a linter, not a security scanner.

Its role in vet isn't to find malware, but to act as an automated code quality check. A script full of shellcheck warnings is a red flag, which helps inform the user's final decision to trust it or not. It's one of several signals that vet provides.

Thanks for the important clarification!

9. __MatrixMan__ ◴[29 Jun 25 14:46 UTC] No.44413583{3}[source]▶

>>44410382 #

After looking closer, I think I misunderstood. I thought that after a human reviewed the script, vet would cache something which indicates that that script is trusted--that way it can run in CI without a human involved, and vet is checking that it is indeed the thing the human trusted. Looks like not.

Re: hashes, the whole point is that I want it to break anytime the developer pushes an update, that's my cue to review the update and decide once more whether I want it in my project. The lack of awareness re: what that curl is going to provide is the whole reason people think that `curl | bash` is insecure.

Otherwise there's no commit which indicates the moment we started depending on the new version--nothing to find if we're later driving `git bisect` to figure out when something went wrong. It could supply a malicious payload once, revert back to normal behavior, and you'd have no way to notice.

Also, you end up with developers who have different versions installed based on when they ran the command, there's no association with the codebase. That's a different kind of headache.