It is basically impossible to sandbox an erlang/elixir system if you allow it to run untested code, especially if you allow loading already compiled code. You *could* interpret erlang/elixir code but it would have to be very limiting but it is still possible to get around this. If you want to run the code within the erlang/elxixir system then the only safe way is to interpret/run another language where you can control how it interacts with the system outside it. Like for example running Lua either with luerl.

Another way would be to run a “safe” language/system outside erlang/elixir. Or perhaps best of all run a special system inside a DMZ.

Exactly this! Docker is NOT a sandbox, it is pretty trivial to ‘break out of it’, and it is designed for process segmentation, not sandboxing, and the developers are upfront about that. Anyone using docker to sandbox has a ticking time-bomb…

SmartOS Zones would be a good sandbox though. FreeBSD Jails, they ‘mostly’ work, but they can be broken out of with relative ease now too. I’d still say just support lua or something, not elixir.

I know i am a Cassandra at that point and that i mess a bit with the whole fun thing.

But Docker is not a sandbox. Is it better than the BEAM isolation ? Yes probably. But if you need a secure sandbox with Docker, the advise right now and for the year to come probably is to have one VM per Docker container. If you want a more secure sandbox/container, have a look at FreeBSD Jails or SmartOS Zones. You can run a Docker container on SmartOS Zones.

There are a lot of LUA implementations for the BEAM:

• https://github.com/rvirding/luerl by the very own RVirding, this is implemented in erlang, not super fast, but very safe, it implements ‘most’ of lua, good enough for simple scripting. However you can implement lua things in erlang/elixir that can be called from lua very fast, so it makes a great simple scripting layer.

• https://github.com/bendiken/exlua is just an Elixir wrapper of luerl to change the API a bit, does not add anything though.

• https://github.com/Eonblast/Erlualib Embedded driver to add lua to the BEAM, full power and normal lua speed, but you can crash the VM if lua crashes (rare, but possible). ^.^

• Do it yourself via a port: This is probably what you should do, make your own C LUA Port system (and release it as a hex.pm library!) that connects to the BEAM via a Port, full safety, full sandbox (as long as you leave out the lua standard library like filesystem and network I/O), etc…

EDIT: It would be fun to build a new simple safe scripting language on Elixir though, not hard to do. ^.^

FWIW I stopped researching exbox because the people interested it gave up on in-language sandboxes for their project and switched to Docker to run untrusted code.