# ai-sandbox

Run an autonomous coding agent against your real project, with the escape routes
closed: only the current directory is mounted, no ambient environment variables,
no root inside, hard resource caps, and outbound network limited to an explicit
allowlist that the agent cannot lift.

Single bash script, rootless podman, Ubuntu 24.04. No daemon, no k8s, no config
language.

```
$ cd ~/Projects/billing-api
$ pi --allow api.anthropic.com --env ANTHROPIC_API_KEY
[aisb] egress gate aisb-gate-7f3c1a -> 127.0.0.1:18084 (1 domains, 0 ip/cidr entries)
[aisb] egress net=allow enforce=nft proxy=[100.64.0.1:18084] direct=0 dns=0
 pi
```

`pi` there is an alias for `ai-sandbox`. Inside, the agent sees `/project` (your
cwd, read-write), nothing else on your disk, and the internet only where you
pointed it.

## Install

```bash
git clone <this repo> && cd ai-sandbox
./install.sh --alias pi          # symlinks to ~/.local/bin and adds the alias to ~/.bashrc
ai-sandbox doctor                # checks podman, rootless, subuid, pasta, SELinux, uid mapping
ai-sandbox build                 # optional: build the image now instead of on first run
make test                        # 160+ assertions, no containers needed
```

Requirements: podman ≥ 5 running rootless (with a `/etc/subuid` range for your
user), and either `pasta` (default in podman 5) or `slirp4netns`. Nothing else —
shellcheck, tests and the image build all run through podman.

## The alias, and how arguments are read

Sandbox flags are consumed until the first positional argument or unknown flag;
those become **arguments to the harness**:

```bash
alias pi='ai-sandbox'

pi                                     # runs pi inside the sandbox
pi --allow api.anthropic.com --env ANTHROPIC_API_KEY --model sonnet
#     ^^^^^ sandbox ^^^^^^^^^^^^^^^^^^^^^^^^          ^^^^^^^^^^^ for pi
pi --shell                             # a bash shell in the same sandbox
pi --net none -- make test             # -- replaces the command entirely
```

`--strict-args` turns an unrecognised flag into an error instead of a pass-through,
which is what you want in scripts.

## Network policy

| mode | what it means |
|---|---|
| `--net allow` *(default)* | Only the allowlist is reachable. A netfilter ruleset inside the container plus a domain-filtering proxy on the host loopback. If the ruleset cannot be installed, the sandbox **refuses to start** (exit 77). |
| `--net none` | No network at all. |
| `--net full` | Nothing restricted. Prints a warning. Never the default. |

```bash
ai-sandbox --allow api.anthropic.com --allow registry.npmjs.org --env ANTHROPIC_API_KEY
ai-sandbox --allow 10.20.0.5:5432            # a database: pinned IP and port
ai-sandbox --allow files.pythonhosted.org --allow pypi.org
ai-sandbox --no-gate --allow example.com     # no proxy container: pin resolved IPs instead
ai-sandbox --proxy corp-proxy.internal:3128  # route through a proxy you already run
```

Domains match that name and anything below it, and are enforced by the gate at
CONNECT time, so CDNs and rotating IPs are not a problem. IP/CIDR entries become
direct netfilter rules for non-HTTP destinations (databases, etc.).

An allowlist is **required** in `allow` mode: an empty list is a hard error, never
a silent free-for-all. Keep it in the repo so the policy is reviewable:

```
# .ai-sandbox/allow  (one entry per line, # comments fine)
api.anthropic.com
registry.npmjs.org
```

## Environment

Nothing is inherited except `TERM LANG LC_ALL LC_CTYPE TZ`.

```bash
--env ANTHROPIC_API_KEY          # from your environment
--env FOO=bar                    # literal (shows up in ps; prefer the two below)
--env-file ~/.config/secrets     # a 0600 NAME=VALUE file
```

Values are handed to podman through a `0600` file that is removed when the run
ends, so they never appear in `ps`, in the printed dry-run, or in the session log.
Asking for a variable that is not set fails the run closed.

## Filesystem

Your cwd is mounted at `/project` and is the working directory — that is the whole
default. Everything else is opt-in:

```bash
--mount ~/.ssh:ro                # if the agent must be able to push
--mount ../docs:/docs:ro         # read-only reference material
--no-cwd                         # a scratch sandbox with nothing mounted
--read-only                      # read-only root filesystem
--ephemeral-home                 # do not persist /home/sandbox (default: persist in a volume)
```

Files the agent writes land on your disk owned by **your** uid, not root
(`--userns=keep-id`, verified by `doctor`).

## Image

Built once per distinct policy from `ubuntu:24.04`, tagged by content hash, reused
afterwards: git, curl, jq, build tools, python3, Node 22 (checksum-verified
against nodejs.org) and the `pi` CLI. `--install PKG` adds packages and produces a
different tag, so variants coexist. `--base-image` swaps the base.

## Inspecting a run

```bash
ai-sandbox --dry-run --allow example.com --env KEY    # exact podman invocation, secrets redacted
ai-sandbox --print-policy                             # effective policy as key=value lines
ai-sandbox --print-entrypoint                         # the enforcement script baked into the image
ai-sandbox doctor [--deep]                            # host checks; --deep tests egress for real
ai-sandbox ps | clean [--all] [--volumes[=GLOB]] | inspect | gate up|status|logs|down
```

State lives under `~/.local/state/ai-sandbox` (session dirs, `log` of every run
with no secret values, build logs). Config in `~/.config/ai-sandbox`.

`/home/sandbox` is a named volume (`aisb-home`) so npm and tool caches survive
between runs. It outlives the image, so after changing the image you may be looking
at a stale home: `ai-sandbox clean --volumes` reclaims unused ones. It only deletes
volumes in the `aisb-` namespace that no container references, and `--volumes=GLOB`
narrows it to one name.

## Why it is hard to undo from inside

The container starts as root with `CAP_NET_ADMIN`, the entrypoint installs the
egress ruleset, and then it execs your command through

```
setpriv --reuid=1000 --regid=1000 --clear-groups --inh-caps=-all --bounding-set=-all --no-new-privs
```

No root, no capabilities, `no-new-privileges`. Flushing the ruleset needs
`CAP_NET_ADMIN`; `unshare -n` needs `CAP_SYS_ADMIN`; setuid helpers cannot hand
either back. Both are asserted against a real container in
[`tests/e2e/11_net.sh`](tests/e2e/11_net.sh). Details and the measurements behind
the design: [docs/networking.md](docs/networking.md).

**Read [docs/threat-model.md](docs/threat-model.md)** — it says plainly what this
does not protect you from (allowlisted destinations, container escapes, anything
you explicitly mounted).

## Project layout

```
bin/ai-sandbox            the application: one script, ~1.3k lines
install.sh                symlink into ~/.local/bin + optional alias
config/                   example config, allowlist and env file
docs/                     networking.md, threat-model.md, recipes.md
tests/run.sh              runner; tests/unit/* (no containers) tests/e2e/* (real ones)
tests/spike_network.sh    re-measure podman's behaviour on a new host
Makefile                  make test | e2e | lint | check | doctor | build
```

## Development

```bash
make test     # unit: args, config, argv construction, env handling, rule generation
make e2e      # + real containers: build cache, egress blocking, capability drop, lifecycle
make lint     # shellcheck in a container
make style    # bash -n
```

The Containerfile, the container entrypoint and the squid config are all generated
from `bin/ai-sandbox`, so the script remains the single source of truth
(`--print-containerfile`, `--print-entrypoint`).