ducoterra
a08a69f143
Two changes, one bug found through the other.
Thinking is policy now: defaultThinkingLevel is xhigh unless you say otherwise
(thinking / --thinking / AISB_THINKING, with pi's levels plus 'host' to decline
and 'off' meaning pi's own no-reasoning level). It is written into the bridged
settings and re-applied by the entrypoint on every run, so a run cannot set its
own reasoning down for the runs after it. Unknown levels are refused with the
list to pick from. Nothing is written for codex, claude or a command after --,
and --no-pi-config declines it along with the bridge, because pi's own defaults
are what that flag asks for.
The reason xhigh had never reached a sandbox is worse than a missing default:
settings.json was managed as one whole file, and pi rewrites its own settings
(a theme change, "seen the changelog"), so the first such write matched nothing
and froze every host preference out permanently -- provider, model, thinking
budgets and level included, a real session left holding just
{"lastChangelogVersion": "1.4.0"}. It is merged per key instead, against a copy
of what we last wrote: a key edited in the sandbox stays edited, a key never
touched follows the host again, an untouched key the host dropped is dropped, a
key pi invented survives, and a file with no base copy takes the host values --
which repairs the volumes already frozen. Unparseable JSON is re-seeded with a
warning since pi cannot use it either; a file the container cannot read is
reported with the fix, because nothing inside the sandbox can repair one.
One trap worth remembering: the seeding script is passed to bash -c in single
quotes, so a single quote inside it closes the argument early and the rest runs
in the outer shell -- valid bash, wrong program, clean bash -n and clean
shellcheck. tests/unit/06_entrypoint.sh extracts the seeding script and asserts
it is quote-free, and extracts the merge program to test its semantics without
a container; tests/e2e/12_sandbox.sh does the same in a real run, including
forcing the level back after the sandbox sets it to off.
LLM-Generated: true
14 KiB
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 aipi.reeseapps.com --env AI_API_TOKEN
[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
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 # 390+ assertions (unit needs no containers; --e2e builds and runs)
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:
alias pi='ai-sandbox'
pi # runs pi inside the sandbox
pi --allow aipi.reeseapps.com --env AI_API_TOKEN --model turbo
# ^^^^^ 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. |
ai-sandbox --allow aipi.reeseapps.com --allow registry.npmjs.org --env AI_API_TOKEN
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)
aipi.reeseapps.com
registry.npmjs.org
If you bridge your pi config (below), ai-sandbox tells you when the model endpoint
your own models.json points at is not in the allowlist -- pi would otherwise start
and sit there unable to answer, which reads like a broken sandbox.
Environment
Nothing is inherited except TERM LANG LC_ALL LC_CTYPE TZ.
--env AI_API_TOKEN # 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 only
writable mount, and nothing else on the host is visible except the one exception
below. Everything else is opt-in:
--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).
Your .agents is shared, read-only
A harness with no skills is a harness you have to re-brief on every run, so ~/.agents
— skills, prompt templates, your standing AGENTS.md — is bind-mounted at
/home/sandbox/.agents, which is where pi looks for user-level skills. Nothing is
copied; it is one mount, and it is read-only:
pi # your skills are there
pi --no-agents # a run where the harness sees none of them
pi --agents-dir ~/work/.agents # a different set, e.g. per-team
Read-only is not a convenience limit. A skill is an instruction the model follows
later, on the host, outside the sandbox — so a sandbox that could edit ~/.agents
had a persistence path out of itself, planted as a helpful-looking SKILL.md. There is
no flag to make it writable, and the ro holds even with --insecure-keep-root.
A project's own .agents/ needs no setting at all: it is inside the project mount, and
harnesses that read both (pi reads ~/.agents/skills and .agents/skills) see the
project's next to yours. What that costs in exposure is spelled out in
docs/threat-model.md: whatever is in those files — including
any token someone pasted into a skill — is now readable by the agent you are sandboxing.
Run --no-agents if a set of skills is not one you would hand to a stranger.
Pi inside the sandbox
The image has pi baked in, and its home is a volume, so out of the box the sandboxed
pi has no provider and no preferences. Rather than making you configure it twice,
ai-sandbox bridges your host ~/.pi/agent/{models,settings}.json -- rewriting
them, because copying them would ship your credential into a container whose entire
purpose is to be unable to use it:
| your host config | what the sandbox gets |
|---|---|
apiKey: "sk-..." or apiKey: "!pass show ..." |
apiKey: "$AI_API_TOKEN" -- pi resolves it itself, no value is written to disk |
a header like X-Trace: "!date +%s" |
dropped, and reported: a host command is not run in the sandbox |
baseUrl: "https://aipi.reeseapps.com/v1" |
unchanged, along with every model, limit and thinking level |
| settings: provider, model, theme, thinking budgets, telemetry | unchanged, merged per key |
a settings value pointing into ~ |
dropped, and reported: that path is not mounted |
auth.json, models-store.json, sessions, extensions |
never touched |
The rewritten pair is seeded into /home/sandbox/.pi/agent at container start, owned by
your uid, mode 600. The two files are managed differently, because they are different
kinds of thing:
| file | rule | why |
|---|---|---|
models.json |
replaced when missing or unchanged, left alone once you edit it in the sandbox | it is a catalog; a partial merge of a provider list is worse than either choice |
settings.json |
merged per key | pi rewrites its own settings — a theme change, "seen the changelog" — and managing the file whole meant that one write froze every host preference out of the sandbox permanently |
So in settings.json: a key you change inside the sandbox stays yours, a key you never
touched follows the host again, a key the host drops disappears unless you had changed
it, and a key pi added (lastChangelogVersion) survives.
Thinking is xhigh, and it is policy
defaultThinkingLevel is the one setting ai-sandbox insists on, because pi's own
default is medium and a sandbox run is usually the kind of work you want reasoned
about hard:
pi --allow aipi.reeseapps.com # xhigh, whatever your host settings.json says
pi --thinking max ... # this run only
pi --thinking off ... # no reasoning, e.g. a mechanical refactor at scale
pi --thinking host ... # stop forcing it; your settings.json decides
--thinking is a policy, not a preference: it is written over the merged settings on
every run, so a run cannot set its own thinking level down for the runs after it. It is
pi-only — codex, claude and anything you put after -- read their own config, and
ai-sandbox leaves that alone. --no-pi-config declines the policy too, since "pi starts
with its own defaults" is what that flag is for.
The token itself follows the normal rule -- it is the one variable the bridged config
names, so it is passed by name (never by value, and never into ps):
pi --allow aipi.reeseapps.com # AI_API_TOKEN is picked up and announced
pi --no-pi-token-env ... # don't pass it; the run then fails closed
pi --pi-token-env GW_TOKEN ... # a different variable name
pi --no-pi-config --shell # no bridge at all
Refusing rather than launching a pi with no credential is deliberate -- the alternative is an agent that silently cannot reach its model.
Image
Both images come from one base, docker.io/library/ubuntu:24.04 — including the gate,
which is squid from Ubuntu's apt rather than a third-party image. Built once per
distinct policy and tagged by content hash: git, curl, jq, build tools, python3, Node
22 (tarball verified against nodejs.org SHASUMS256.txt) and the pi CLI. --install PKG adds packages and produces a different tag, so variants coexist, and
--base-image swaps the base.
The base is pinned by digest
A tag is a moving pointer: FROM ubuntu:24.04 means "whatever Canonical points at
this week", which makes a build unreproducible and a security patch invisible. So the
tag is resolved to a digest, recorded under ~/.cache/ai-sandbox/base/, and the
digest goes into the FROM line and into the content hash — refreshing the base
produces a new image instead of mutating one a sandbox may be running right now.
ai-sandbox update --check # what upstream has, what you are pinned to, nothing built
ai-sandbox update # re-resolve, rebuild sandbox + gate, keep the old image
ai-sandbox build --refresh-base
Freshness is a TTL: every AISB_BASE_TTL_DAYS (default 7) the digest is re-resolved,
which is a manifest read (skopeo), not a download. Offline, or with
AISB_BASE_AUTO_UPDATE=0, the recorded digest is kept — a stale pin beats a mutable
one, and AISB_BASE_TTL_DAYS=-1 pins until you say otherwise. A build with no digest
is announced as UNPINNED, labelled that way, and warned about by doctor. Preview
modes (--dry-run, --print-*) never touch the network, so they stay scriptable and
report the pin you already have; inspect is the one that asks the machine now.
What an image admits to being
podman image inspect on any ai-sandbox image shows aisb.base-digest, aisb.node,
aisb.pi-package, aisb.pi-version (plus aisb.role=gate for the gate), and
/etc/aisb/manifest.txt inside it lists every resolved apt package version — the
answer to "which squid was doing the filtering" once the build log is long gone. The
previous image is always kept after an update, so rollback is a tag away.
Inspecting a run
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. Details and the measurements behind
the design: docs/networking.md.
Read 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
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).