This looks pretty decent actually. Sure, you could consider it a frontend/SDK for bubblewrap/seatbelt/processcontainer; but setting em up consistently is far from trivial; and hand rolling is a really bad idea (speaking from experience).
I like the ‘learning’ mode for figuring out what perms/config a runtime needs, the MIT license, the clear optional telemetry disclosures, and somewhat light and still readable documentation.
Regardless of your views on Microsoft, this looks quite useful; serves a clear purpose, and from a quick glance, looks like a high quality project even if it’s just the first version.
Do any of these sandboxing solutions have a dynamic component to them that lets you grant permissions, starting with a minimal sandbox and asynchronously adding permissions as they become necessary? Harnesses try to do this when accessing non-project folders, but it's not always strictly enforced and generally not revocable. Harnesses also block agent execution until a decision is made, which requires constant monitoring to ensure progress can happen when the agent could easily proceed with an alternative method right away.
I like the idea of a minimal sandbox that protects against accidental `rm -rf` and against personal data leakage, but such a setup then often gets in the way of the specific task to be done. Ideally the sandbox would be able to aggregate blocked accesses and then expose them in an external TUI dashboard, where I can then enable access (without blocking any running agent on this, since that's prone to "press okay" fatigue).
That site thinks this file has 2.9k sloc and doesn't seem to parse rust comments. In reality, there's only 1,465 sloc; and 635 loc of tests.
Definitely nowhere near 350k sloc.
--
As for your sandbox run: it's a single-contributor project, seems to have only have basic smoke tests, and has a few major/critical security issues:
* _generate_seccomp_filter compares newline-deliminated syscalls, against a multi-line blocklist, meaning the entire function doesn't block anything and is essentially a no-op.
* Main script invokes working directory's .env as shellcode, before switching into restricted filesystems and dropping capabilities. Attacker-controlled .env can run shellcode with full privileges.
* Lots of race conditions which I haven't verified, but doesn't really matter.
I'd make PRs, but I don't think it's a good idea to try and DIY a sandboxing system in bash with minimal SLOC as the target in the first place. I'm also slightly concerned that most of your comments on HN seem to be promoting this repo?
Why is everyone making their own code execution agent runtime engines I have an entire project built on top of openshell already, why not first come up with a sandboxing policy design, like unix did, and then build on top of that.
Currently all project do tend to agree on what and how they work but certain things being different makes porting tedius, if all of them have a bare minimum subset common amongst them it would be much easier to switch, and validate security surface area.
I feel like there are more vulnerabilities in this vibe coded slop sandboxes, and it's more likely everyone one of us trusting them to build projects around them will shoot our foot off once a cve is hit in one that's common in all of them but since they are all slop copies someone will have to figure out how they apply to all others and then manually fix it properly, and if one of them makes a CVE public it will leave dozens of these runtimes open to exploits.
I wish the best to my future self with regards to security I feel like we are completely screwed. Since we can no longer depend on upstream for security.
"Im really fkin worried we're all building the same thing"
Everyone has been building a harness/sandbox the last 6 months. Ive seen dozens and dozens shared in discords.
Even companies are totally stuck focused on the same paradigms.
The previous iteration of this was RAG/Chat interfaces. See PewDiePie's project. Last month it was briefly everyone building the same classifier.
Peter Thiel, gave a lecture about this same phenomenon 15 years ago likely because he observed the same things going on during other hype cycles. Everyone building the same things. Its called something like "Dont build the obvious thing"
This is why Im moving towards hardware for personal projects, it forces me to be much more creative and think outside the "How can I make something AI adjacent/powered" trap thats so easy to fall into in pure software right now.
My guess is that Microsoft thinks this can be deployed with standard, company-wide policy across platforms (mostly) with their IT management tools which poses a unique advantage.
In reality, however, knowing how much difference there is between OSes, how tricky it is to configure these things to make them actually useful, and how bad Microsoft products are, I'm not enthusiastic about this project -- there are so many others on the market already, and I'll wait to see if this gains traction.
(Note that on MacOS it only supports seatbelt? That's not nearly the same as microvm.)
The problem with OS level sandboxes, and the reason why WebAssembly's being explored in this space (and Electron is so popular), is that relying on OS/hardware features means your TAM shrinks to a fraction of total, and it's historically well known you set yourself up to lose.
History is littered with tons of super cool OS features that didn't manage to gather enough market share and ended up as cool futures, and fodder for 'we invented the future 20 years ago' style articles.
e.g. this one puts multi-platform support as a high requirement, a requirement that OpenShell doesn't fulfil (and likely won't given it's architecture/goals).
That’s exactly it.
There should be some permission logic for delegating.
But as always, there are rivals trying to set their tone on what’s the standard. We all wish there was one unified agreed concept that will work but I guess the most common one will eventually survive.
Just as Microsoft in a sense embraces Linux with WSL and also Apple has their virtualization framework.
I hope we’ll eventually get unified model management system to include also permissions designed properly
They have a sandbox escape in there. Likewise capability ordering is wrong. Exactly what you should expect from Microsoft.
Since this apparently wraps bubblewrap (another incompetent action on behalf of Microslop), did a quick sweep of that codebase too. Setuid is wrong, capability dropping is wrong, bubblewrap does _not_ protect against compromised/vulnerable kernels (and it should fyi), wrote up a full bubblewrap/mxc sandbox escape too.
Asked Grok the difference between mxc and flatpak:
"So MXC is a cross-platform “what may this workload touch?” layer aimed at agents. Flatpak is a Linux app format whose sandbox happens to share a backend with MXC on Linux."
I like the ‘learning’ mode for figuring out what perms/config a runtime needs, the MIT license, the clear optional telemetry disclosures, and somewhat light and still readable documentation.
Regardless of your views on Microsoft, this looks quite useful; serves a clear purpose, and from a quick glance, looks like a high quality project even if it’s just the first version.
Not sure I will give up on smolvm though.
I have scripts to launch an instance per task. Nono wraps my coding agent.
I provide the git clone for the specific task.
It works really well.
I like the idea of a minimal sandbox that protects against accidental `rm -rf` and against personal data leakage, but such a setup then often gets in the way of the specific task to be done. Ideally the sandbox would be able to aggregate blocked accesses and then expose them in an external TUI dashboard, where I can then enable access (without blocking any running agent on this, since that's prone to "press okay" fatigue).
Does anything close to this exist yet?
I used agent over 1 year and basically always give codex full permission on each thread, do not get issue so far
Why we need this layer of complexity? Or its mainly for big company that need control ?
I'd be way more confident building upon something I can grasp and understand. [2]
[1]: https://ghloc.dev/microsoft/mxc [2]: https://github.com/sandbox-utils/sandbox-run
https://ghloc.dev/microsoft/mxc?branch=main&locsPath=%5B%22s...
That site thinks this file has 2.9k sloc and doesn't seem to parse rust comments. In reality, there's only 1,465 sloc; and 635 loc of tests.
Definitely nowhere near 350k sloc.
--
As for your sandbox run: it's a single-contributor project, seems to have only have basic smoke tests, and has a few major/critical security issues:
* _generate_seccomp_filter compares newline-deliminated syscalls, against a multi-line blocklist, meaning the entire function doesn't block anything and is essentially a no-op.
* Main script invokes working directory's .env as shellcode, before switching into restricted filesystems and dropping capabilities. Attacker-controlled .env can run shellcode with full privileges.
* Lots of race conditions which I haven't verified, but doesn't really matter.
I'd make PRs, but I don't think it's a good idea to try and DIY a sandboxing system in bash with minimal SLOC as the target in the first place. I'm also slightly concerned that most of your comments on HN seem to be promoting this repo?
That being said, a month of MXC has more line changes than 2-3 years of runc
Currently all project do tend to agree on what and how they work but certain things being different makes porting tedius, if all of them have a bare minimum subset common amongst them it would be much easier to switch, and validate security surface area.
I feel like there are more vulnerabilities in this vibe coded slop sandboxes, and it's more likely everyone one of us trusting them to build projects around them will shoot our foot off once a cve is hit in one that's common in all of them but since they are all slop copies someone will have to figure out how they apply to all others and then manually fix it properly, and if one of them makes a CVE public it will leave dozens of these runtimes open to exploits.
I wish the best to my future self with regards to security I feel like we are completely screwed. Since we can no longer depend on upstream for security.
"Im really fkin worried we're all building the same thing"
Everyone has been building a harness/sandbox the last 6 months. Ive seen dozens and dozens shared in discords.
Even companies are totally stuck focused on the same paradigms.
The previous iteration of this was RAG/Chat interfaces. See PewDiePie's project. Last month it was briefly everyone building the same classifier.
Peter Thiel, gave a lecture about this same phenomenon 15 years ago likely because he observed the same things going on during other hype cycles. Everyone building the same things. Its called something like "Dont build the obvious thing"
This is why Im moving towards hardware for personal projects, it forces me to be much more creative and think outside the "How can I make something AI adjacent/powered" trap thats so easy to fall into in pure software right now.
In reality, however, knowing how much difference there is between OSes, how tricky it is to configure these things to make them actually useful, and how bad Microsoft products are, I'm not enthusiastic about this project -- there are so many others on the market already, and I'll wait to see if this gains traction.
(Note that on MacOS it only supports seatbelt? That's not nearly the same as microvm.)
History is littered with tons of super cool OS features that didn't manage to gather enough market share and ended up as cool futures, and fodder for 'we invented the future 20 years ago' style articles.
e.g. this one puts multi-platform support as a high requirement, a requirement that OpenShell doesn't fulfil (and likely won't given it's architecture/goals).
But as always, there are rivals trying to set their tone on what’s the standard. We all wish there was one unified agreed concept that will work but I guess the most common one will eventually survive.
Just as Microsoft in a sense embraces Linux with WSL and also Apple has their virtualization framework.
I hope we’ll eventually get unified model management system to include also permissions designed properly
Since this apparently wraps bubblewrap (another incompetent action on behalf of Microslop), did a quick sweep of that codebase too. Setuid is wrong, capability dropping is wrong, bubblewrap does _not_ protect against compromised/vulnerable kernels (and it should fyi), wrote up a full bubblewrap/mxc sandbox escape too.
"So MXC is a cross-platform “what may this workload touch?” layer aimed at agents. Flatpak is a Linux app format whose sandbox happens to share a backend with MXC on Linux."