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Show HN: Drop – a rootless Linux sandbox with gVisor support

47 points mixedbit 1 hour ago 7 comments

I created Drop because I always felt uneasy installing and running third-party programs using my main user account. A single compromised dependency means a full compromise of the system. What is even worse, because I ship software from my computer, a single compromised dependency can lead to compromise of all the users of my software.

Containers and VMs are one solution, but for local work, they are often detrimental to productivity. It takes effort to configure a machine with all the tools and configs needed for productive work, but a container or a VM will be stripped of all these tools. This is great for production deployments, where the aim is a reproducible system with minimal dependencies, but can get in the way of productive local work.

Drop is language independent, but the workflow is inspired by Python's virtualenv. With virtualenv the environment isolation is only a convention that relies on installed dependencies being good citizens. With Drop the isolation is enforced.

Each Drop environment gets its own writable and easily disposable home dir, with only selected config files and dirs from the original home mounted, mostly read-only.

Drop uses Linux namespaces for isolation (user, mount, network, PID, IPC, cgroup), doesn't require root and, as an option, uses gVisor user-space kernel, which adds protection against exploiting host kernel vulnerabilities to escape the sandbox.

I don't want to make the introductory post too lengthy, but I'm here to answer any questions and give any additional technical details.

Note: This is my 3rd submission of the project, the first two did not draw attention. Since then I have added support for gVisor and created a project website to better explain the concept and organize documentation.

yu3zhou4 36 minutes ago | parent

Gratulacje Jan! Looks like something critical to gain adoption these days, security-wise. For others who also wonder how it works, I find this docs page a bit more informative than the landing page https://droprun.sh/docs/sandbox-overview/

JoshTriplett 33 minutes ago | parent

So, the primary advantage of this over bubblewrap is the insulation layer between the program and kernel syscalls?

mixedbit 19 minutes ago | parent

Bubblewrap is a low level tool, it describes itself as a sandbox building block, rather than a high-level sandbox intended to be used directly (for example, Flatpak uses bubblewrap as its building block). Drop in contrast is high-level, designed to be used directly in day-to-day work without the need to assemble the low-level details of the sandbox.

zoobab 27 minutes ago | parent

Have you ever tried to use proot?

It does not use process namespaces, and can run on Android (on Termux with proot-distro).

refibrillator 15 minutes ago | parent

Hi OP, funny enough I’m working on something very similar. Lots of us are I guess! Take that as validation of your thinking.

I like that your readme has a couple paragraphs comparing to popular tools in this space. Personally I feel it is a bit light on the security differentiators (if any). For example you are using the same fundamental primitives that are used in nsjail, runc, etc. Thus it seems you have recreated those libraries in some aspects, so would be curious to hear your rationale for approaching this way vs building explicitly on those primitives.

saghm 10 minutes ago | parent

This is super interesting to me. I've slowly been working on something similar (https://gitlab.com/saghm/tartarus) because my ideal sandboxing is "prevent writing to anything outside this dir but still allow reading to most things so that I don't have to manually copy things into a container/VM". I approached it by trying to figure out how to build up a bubblewrap based on a config that gave the properties I wanted, with the hope that I could eventually expand it to support other platforms via stuff like `sandbox-exec` on MacOS, but I haven't had time to work on it more for a while.

At a glance, this seems to be providing most of what I was originally looking for when I ended up deciding I'd have to write it myself, but focusing specifically on Linux and providing a more full-fledged sandbox rather than only caring about a small set of permissions that I personally had a need for. Probably the biggest (and least hardened) feature that I spent time on in mine was trying to figure out how to allow arbitrary GUI apps so that I could run agents in it via Zed.

I'm definitely going to try this out and see how well it works for me. It's insane to me that this is something none of the big AI companies have bothered solving this yet other than via opaque rules built into their harnesses or absolutely awful manual rules that expect me to hard-code shapes of shell commands that I want to allow or not allow.

killerstorm 6 minutes ago | parent

> my ideal sandboxing is "prevent writing to anything outside this dir but still allow reading to most things so that I don't have to manually copy things into a container/VM"

That's what Codex does out of the box, and it's not good against malware - i.e. a rogue npm packet (or even just codex after prompt injection) can read your ssh key and send it to the attacker.