# Threat model

Read this before relying on `ai-sandbox`. It is a **seatbelt, not a jail**: it
raises the cost of an agent's mistakes and of a moderately compromised prompt
context, on a machine you still log into as yourself.

## Who we assume is hostile

The modelled adversary is **the agent you are running**: an LLM harness with your
write access to one directory, capable of running arbitrary shell commands, and
vulnerable to prompt injection from the files it reads, the web pages it fetches,
and the package changelogs it installs. We assume it will try to escape when a
prompt injection tells it to.

We do **not** model a kernel-level adversary, a hostile container image from a
registry you don't control, or someone with access to your host user account.

## What stops working (defence in depth, most to least load-bearing)

| Attack | Stopped by | Evidence |
|---|---|---|
| Editing / deleting anything outside the project directory | `$PWD` is the only writable mount; the rest of the host is not in the mount namespace | `tests/e2e/12_sandbox.sh` |
| Rewriting your skills, prompts or global `AGENTS.md` | `~/.agents` is mounted, but read-only, and there is no flag to change that | `tests/e2e/12_sandbox.sh` |
| Reading `~/.ssh`, `~/.aws`, `~/.config/gcloud`, browser profiles | same as above; those paths do not exist in the container | `tests/e2e/12_sandbox.sh` |
| Exfiltrating your environment (API keys for *other* services) | nothing is passed through unless named with `--env` | `tests/unit/04_env.sh`, `tests/e2e/12_sandbox.sh` |
| Passing secrets through the process list to other users | values travel in a `0600` file, never in argv | `tests/e2e/12_sandbox.sh` |
| Egress to an arbitrary host (curl, python, a raw socket, a bespoke exfil tool) | netfilter `policy drop` inside the container's namespace | `tests/e2e/11_net.sh` |
| Egress through the proxy to a non-allowlisted domain, including HTTPS | squid's `http_access deny all` after the allowlist | `tests/e2e/11_net.sh` |
| Deleting or weakening the egress ruleset | the command runs with no capabilities; `CAP_NET_ADMIN` was dropped across `exec` | `tests/e2e/11_net.sh` |
| `unshare -n` to get a fresh namespace with its own routes | requires `CAP_SYS_ADMIN`, which the command does not have | `tests/e2e/11_net.sh` |
| Privilege escalation via a setuid binary in the image | `--security-opt no-new-privileges` + `--cap-drop=ALL` | container config, asserted in `tests/e2e/10_image.sh` |
| Reaching other host services on loopback | only the gate's port is routable through the mapped loopback address | `tests/e2e/11_net.sh` |
| Fork bombs, memory bombs, runaway builds | `--pids-limit`, `--memory`, `--cpus`, `--tmpfs` sizes | `tests/e2e/10_image.sh` |
| Writing to the host's package manager, `/etc`, global npm/pip | read-only-ish image, `HOME` inside the container, optional `--read-only` | `tests/e2e/12_sandbox.sh` |
| Credential persistence you did not ask for | `--ephemeral-home`; the default home volume is named and inspectable | `tests/e2e/12_sandbox.sh` |
| Silent wide-open starts | an empty allowlist in `allow` mode is a hard error | `tests/unit/01_args.sh` |
| An agent shipping work you have not looked at (`git push`) | the git remote is not in the allowlist, so nothing in the container can reach it; `ai-sandbox-autophase` commits and pushes on the host, outside the sandbox, between unit runs | `tests/unit/10_autophase.sh` |
| The gate becoming the escape (`validate.sh` is inside the writable mount) | the pass/fail gate runs in the sandbox as the same unprivileged user, not on the host | `tests/unit/10_autophase.sh` |

## What does **not** stop it

Be honest about these, and design your work accordingly.

1. **Anything you allowlist is reachable, in both directions.** Allow
   `api.github.com` and a prompt-injected agent can push your code to a repository
   it controls, using the token you deliberately handed it. The allowlist limits
   *where*, not *what*. Prefer least-privilege, read-only, short-lived tokens.
2. **The project directory is genuinely writable.** A bad `rm -rf`, a force push, a
   corrupted lockfile all still happen — just confined to that directory. Keep the
   tree committed (`ai-sandbox doctor` warns you when it is dirty).
3. **Kernel and runtime escapes.** A container is not a VM. A container escape
   vulnerability in runc/crun or the kernel gets an attacker to your user account.
   For genuinely untrusted code, use a VM or a disposable machine.
4. **`--net full` and the escape hatches do what they say.** `--allow-unenforced`,
   `--insecure-keep-root`, `--mount`, `AISB_EXTRA_ARGS`, `--net full` all weaken the
   posture. They are named to be uncomfortable on purpose; nothing uses them
   implicitly.
5. **Side channels.** Timing, resource consumption, and "the agent typed X into a
   form on a site you allowed" are out of scope.
6. **A cached home volume can hold credentials.** If a harness logs in inside the
   sandbox, the token lives in the `aisb-home` volume, and any later sandbox run
   using that volume can read it. `--ephemeral-home` per run, or a dedicated
   `AISB_HOME_VOLUME` per trust level.
7. **DNS is closed in gate mode, open in `--no-gate` mode.** With `--no-gate`, name
   lookups leave the container; that is a modest data channel and a fingerprint of
   what you are doing. Egress to non-allowlisted IPs stays blocked either way.
8. **The gate sees everything that flows through it** — including any credentials
   in proxied requests. That is the point of an egress proxy; the squid config logs
   to its own container log, and `gate logs` shows them. Do not put secrets in URLs.
9. **Supply chain inside the allowlist.** `registry.npmjs.org` allowlisted means any
   package, including a typosquatted one, can be fetched. Allowlisting a domain is
   not a security review of what you install from it.
10. **Rootless podman still means shared kernel and shared UID namespace.** Files
    the container writes are owned by *you*. There is no uid boundary between
    "agent's file" and "your file" beyond ownership metadata and your own discipline.
11. **Your `~/.agents` is readable inside the sandbox.** This is a deliberate
    exception to "only your project directory is mounted", because a harness without
    your skills is a harness you re-brief every run: `~/.agents` arrives read-only at
    `/home/sandbox/.agents` (`--no-agents` for a run without it, `--agents-dir` for a
    curated set). Read-only means the agent cannot write a `SKILL.md` that you will
    follow tomorrow on the host — that is the part that matters, and it holds even under
    `--insecure-keep-root`. It does *not* mean the contents are secret: the whole tree,
    including its `.git` history and any token someone pasted into a skill, is readable
    by whatever you run in there. Treat a shared skill directory as published to the
    agent, lint it for secrets (`skill-lint`), and keep credentials in the environment
    you pass explicitly rather than in a file that is mounted everywhere.
12. **The pi bridge reads a file that may hold a live key.** It rewrites `apiKey` to
    an environment reference and never copies `auth.json`, but the *endpoint* in your
    `models.json` becomes an endpoint the sandbox can be pointed at, and the token it
    uses is your real one. So the bridged config is a convenience, not a narrower
    credential: prefer a per-sandbox token from your gateway if it can mint one, and
    note that a bridged run whose token variable is unset or empty is refused rather
    than started. Sandboxed edits to `~/.pi/agent` persist in the home volume and win
    over later host changes (see the README), which is convenience with a consequence: a
    hostile run could rewrite the sandboxed pi config for later runs of that volume —
    point `baseUrl` at a host it controls, swap a model, change the provider. Merging
    `settings.json` per key limits this (a run can only pin the keys it actually writes,
    and everything else keeps following your host config), and `defaultThinkingLevel` is
    re-forced every run so a run cannot quietly lower the reasoning of the next. It is
    not eliminated: `--ephemeral-home` removes it, and `inspect` shows what is bridged.

13. **A push on the host still pushes what the agent wrote.** `ai-sandbox-autophase`
   keeps the remote away from the sandbox, but somebody has to deliver the work, and
   that somebody is the harness running as you. It commits only the phase's own
   changes and only after `.agents/validate.sh` passes — so read that gate as part of
   your trust base. It lives in the writable mount, which is exactly why the gate runs
   *in the sandbox* by default; `--validate-in host` hands that judgement to you and
   warns on every run.

## Residual risk rating

*Accidental destruction and ambient credential leakage: largely eliminated.*
*Deliberate data exfiltration over an allowlisted path: mitigated, not prevented.*
*Container escape to the host: out of scope, accept it or use a VM.*