a10r (u/a10r) - Readit News

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

subjectsigma · 9 months ago

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.

a10r · 9 months ago

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!

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

a10r · 9 months ago

By the way, the excellent discussion here got me thinking about the next logical step for vet: supporting private environments.

Running public scripts is great, but what about running deployment scripts from a private GitHub repo or setup scripts from an internal server?

Based on this, I've opened a new feature request to add authentication support to vet, with a roadmap that includes .netrc support, a VET_TOKEN environment variable, and a future goal of integrating with secret managers like HashiCorp Vault by reading tokens from stdin.

If you're interested in that direction, I'd love to get your thoughts on the feature request over on GitHub:

https://github.com/vet-run/vet/issues/4

Thanks again for all the great feedback!

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

thealistra · 9 months ago

Can you show how it works on the page or readme as a video?

Does it open pager or editor? How does it show the shellcheck issues.

a10r · 9 months ago

You're right, the README explains what vet does, but it doesn't do a great job of showing how it feels to use it. I'll definitely create a demo GIF for the page.

To answer your questions directly in the meantime:

- Pager or Editor? It opens a pager (less by default, but it will automatically use the much nicer bat if you have it installed for syntax highlighting). It doesn't open an editor to prevent any accidental modifications.

- ShellCheck Issues: If shellcheck finds issues, it prints its standard, colorful output directly to your terminal before you review the script. It then pauses and asks you if you want to proceed with the review despite the warnings, like this:

==> Running ShellCheck analysis...

In /tmp/tmp.XXXXXX line 7: echo "Processing file: $filename" ^-- SC2086: Double quote to prevent globbing and word splitting.

==> WARNING: ShellCheck found potential issues. [?] Continue with review despite issues? [y/N]

Thanks again for the excellent idea!

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

alganet · 9 months ago

What if someone peppers their malicious script with `# shellcheck disable=` pragmas?

a10r · 9 months ago

Great point.

A malicious actor could definitely do that. That’s why vet’s model doesn’t rely solely on ShellCheck—it’s just one layer. The key layer here is the diff. Even if the linter is silenced, the diff reveals any new suspicious # shellcheck disable= lines added to trusted scripts. That change alone is a red flag.

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

stedaniels · 9 months ago

It is very trivial to serve different code to someone inspecting the code than when they pipe it to bash. In the very rare case someone inspected it they’d likely do so in a way that was vulnerable to this.

a10r · 9 months ago

That’s an excellent point, and thank you for raising it. You are 100% correct—relying on users to inspect a URL that could be spoofed with User-Agent trickery is a flaw in the original recommendation. It's a classic threat model that I should have addressed from the start.

Thanks to your feedback, I've just merged a PR to change the recommended installation method in the documentation to the only truly safe one: a two-step "download, then execute the local file" process. This ensures the code a user inspects is the exact same code they run.

I sincerely appreciate you taking the time to share your expertise and hold the project to a higher standard. This is what makes a community great.

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

geocar · 9 months ago

> 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.

a10r · 9 months ago

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.

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

kevincox · 9 months ago

My main question is in 90% of cases these are installers. How are you actually verifying the software that you install? In some cases it is signed and verified but in many cases it is just coming down from the same HTTPS server with no additional verification. So are you then diffing the code (which may be compiled) as well?

I'm not saying that random running random installers from the internet is a great pattern. Something like installing from your distribution can have better verification mechanisms. But this seems to add very little confidence.

a10r · 9 months ago

You're absolutely right—vet's scope is focused on securing the installer script itself, not the binary it downloads.

The goal is to prevent the installer from being maliciously modified to, for example, skip its own checksum verification or download a binary from a different, malicious URL.

It's one strong link in the chain, but you're right that it's not the whole chain.

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

a10r · 9 months ago

Love the idea!

The two biggest hurdles for a security tool like this are LLM non-determinism and the major privacy risk of sending code to a third-party API.

This is exactly why vet relies on ShellCheck—it's deterministic, rules-based, and runs completely offline. It will always give the same, trustworthy output for the same input.

But your vision of smarter analysis is absolutely the right direction to be thinking. I'm excited for a future where fast, local AI models can make that a reality for vet. Great food for thought!

a10r commented on Show HN: Vet – A tool for safely running remote shell scripts getvet.sh... · Posted by u/a10r

a10r · 9 months ago

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