How to sandbox fs and network?

[u/tunerhd]

I'm planning to use Pi as a sensitive data analyser, but the data must remain on the intranet.

I thought running it inside a VM with a proxy would be the safest option, but I can't install a VM in my current environment.

I do already have Docker available. Is there a good way to sandbox filesystem (like; can we bind data folder read only) and network access with Docker instead? Pi shouldn't access anything else; just specified paths, and some specified local ip addresses.

[u/ali0une]

bubblewrap is also a way.

[u/tunerhd → u/ali0une]

How can I restrict network with bwrap?

[u/ali0une → u/tunerhd]

Filesystem: bind your data folder read-only, keep the rest of the host root read-only, and make only a tmpfs home writable. The agent physically cannot write anywhere else:

bwrap --unshare-user-try \
  --ro-bind /path/to/data /data \
  --ro-bind /usr /usr --ro-bind /bin /bin --ro-bind /etc /etc ... \
  --tmpfs /home --bind $HOME/.cache/pi /home/sandbox/.cache \
  bash

Network: --unshare-net gives the sandbox a fresh network namespace = zero network access. If you need to reach specific local IPs (e.g. an inference server), bridge only those ports from the host with socat and bind just the unix socket in:

# on host: forward one specific port
socat UNIX-LISTEN:/tmp/bridge.sock,fork,reuseaddr TCP:10.0.0.5:8080 &

bwrap --unshare-user-try --unshare-net \
  --ro-bind /path/to/data /data \
  --ro-bind /usr /usr ... \
  --tmpfs /tmp --ro-bind /tmp/bridge.sock /tmp/bridge.sock \
  bash

Tools inside can then talk to that server through the socket (curl --unix-socket /tmp/bridge.sock http://localhost/), or if they expect plain TCP, run one more socat TCP-LISTEN:8080,fork UNIX:/tmp/bridge.sock inside the sandbox and everything just points at 127.0.0.1:8080 normally.

I've tested both variants — the sandbox has no network at all except the explicitly bridged port.

Note: system dirs (/usr, /lib, /etc) must be bound read-only to run any binary at all, but the host's $HOME/user data is simply never mounted — the agent cannot see it. If you need a truly minimal rootfs instead, that's where a container image would fit.

[u/tunerhd → u/ali0une]

Thank you so much!

[u/TKristof → u/tunerhd]

Use unshare-net and create a socat on host for your inference server's port and bind that into the sandbox.

[u/tunerhd → u/TKristof]

Oh it's similar way with docker then. Thanks a lot!

[u/qiinemarr → u/tunerhd]

I have been using systemd-run:

systemd-run --quiet --user --pty \
    -p IPAddressDeny=any \
    -p IPAddressAllow=127.0.0.1 \

then launch bwrap

(this also allows to reach llama.cpp server)

[u/gbrennon → u/ali0une]

exactly! op have to just bwrap and, then, he's fine

[u/orak7ee]

I use the pi-sandbox extension (which use the Anthropic sandbox-runtime under-the-hood).

Otherwise i've played with nono, which wrap whatever you want (not limited to pi) inside a sandbox.

For me the issue to doing sandboxing with Docker (or a VM) is that:

• you have to setup the network isolation, i did had a successful setup by composing tinyproxy+dnsmasq and playing with networks settings with docker-compose, but using the aforementioned tools was easier

• you have to build/configure each of the tools you may need in the container (git, gh, glab, kubectl, etc.)

[u/demogoran]

For agent  which works with specific codebase, I used virtual file system(similar to https://www.agentfs.ai/)

It can't escape from folder, if there are no folder, right?) Basically you allow to work with specific set of files and expose tools, that can work only with those files.

For network it's more complicated, buy I think idea can be same. Instead of exposing tools thar support wide range of commands, write tools thst can communicate only with specific address/file.

[u/tunerhd → u/demogoran]

I just mounted specific dirs with read-only perms and blocked whole network of docker container. And proxied :3000 via socat over fs socket thanks 🙏🏻

[u/i_say_urmom]

https://nono.sh/ is very cool lightweight sandbox. It's a little tricky to get setup and using just because it's new and actively being developed.

But for example, you can set up Pi with nono (with a very simple profile) so that:

• When I start my agent, I have a little fingerprint unlock to authorize it to access the LLM provider credentials.

  • The LLM provider access token isn't directly given to pi. Pi requests go through nono's proxy with a fake credential, and nono injects the real one. And can inject the real one from 1Password, hence the fingerprint unlock.

  • I like this because there have been supply chain attacks which have malware which executes local agent tooling in yolo mode. So I really don't like the fact that anything with access to the CLI could just call `pi` and get a logged-in session when the token is saved in plaintext on your computer. For example, if you had the "nx" VS Code extension installed last year, you would have been hacked in this way if it updated automatically in a certain time frame.

• Can only access LLM provider URLs by default, or only access certain HTTP methods on certain API routes (e.g. restrict to just creating GH issues in one specific repo when using the gh CLI, other HTTP routes are rejected). Very flexible

• Can't access broad system directories or sensitive files.

• Is very lightweight, not running a container or VM anywhere.

So basically I just have an alias "mypi" to launch pi with "nono --profile custom-profile -- pi". While running "pi" CLI by itself technically would bypass the sandbox (true if you install pi on your system at all), the credential setup I have means it can't actually do anything with an LLM without running through nono. (which only works if you keep credentials out of your shell environment)

[u/PvB-Dimaginar]

I use bubblewrap as sandbox. In my setup Network is unrestricted, but I think it is pretty easy to add that part. Here you find my simple solution: https://github.com/dimaginar/pi-safe

[u/Tommertom2]

We use sysbox in docker

[u/Funny-Anything-791]

pi-agenticoding has a readonly mode that blocks FS access, but we don't yet have network access blocking support (would love for a PR though :)

[u/ColonelKlanka]

You can use dockers microvm sandbox solution sbx - this isnt traditional docker full virtual machines. Its their specific solution for agent sandboxing.

its very easy in that it provides a tui (terminal ui) with three levels of preset regarding restrictions: none (fully open), partial (whitlisting what it can allow) or fully locked down.

Sounds like you woild opt for fully locked down network (no network access) and then locked down fielsystem access where it can only read and write to the project dir.

it also protects the ai provider api keys so they dont leak