<!-- SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved. -->
<!-- SPDX-License-Identifier: Apache-2.0 -->
# Sandbox Image Hardening

The NemoClaw sandbox image applies several security measures to reduce attack
surface and limit the blast radius of untrusted workloads.

## Removed Unnecessary Tools

Build toolchains (`gcc`, `g++`, `make`) and network probes (`netcat`) are
explicitly purged from the runtime image. These tools are not needed at runtime
and would unnecessarily widen the attack surface.

The runtime image keeps a small set of operational utilities for normal sandbox
workflows, including `vi`, `jq`, and `dos2unix`. Use these for lightweight
inspection and file cleanup inside the sandbox, but make durable image or policy
changes in the NemoClaw source tree and rebuild the sandbox.

If you need a compiler during build, use the existing multi-stage build
(the `builder` stage has full Node.js tooling) and copy only artifacts into the
runtime stage.

## Process Limits

The container ENTRYPOINT sets `ulimit -u 512` to cap the number of processes
a sandbox user can spawn. This mitigates fork-bomb attacks. The startup script
(`nemoclaw-start.sh`) applies the same limit.

Adjust the value via the `--ulimit nproc=512:512` flag if launching with
`docker run` directly.

## Dropping Linux Capabilities

The NemoClaw entrypoint drops dangerous capabilities from the process bounding
set before it starts agent services.
It removes `CAP_SYS_ADMIN`, `CAP_SYS_PTRACE`, `CAP_NET_RAW`,
`CAP_DAC_OVERRIDE`, `CAP_SYS_CHROOT`, `CAP_FSETID`, `CAP_SETFCAP`,
`CAP_MKNOD`, `CAP_AUDIT_WRITE`, and `CAP_NET_BIND_SERVICE`.
When `setpriv` is available, the entrypoint also removes the remaining
privilege-separation capabilities during the switch from root to the
`sandbox` and `gateway` users.

For defense-in-depth, also drop all Linux capabilities at the container runtime
when you launch the image directly:

```console
$ docker run --rm \
    --cap-drop=ALL \
    --ulimit nproc=512:512 \
    nemoclaw-sandbox
```

### Docker Compose Example

```yaml
services:
  nemoclaw-sandbox:
    image: nemoclaw-sandbox:latest
    cap_drop:
      - ALL
    cap_add:
      - NET_BIND_SERVICE
    ulimits:
      nproc:
        soft: 512
        hard: 512
    security_opt:
      - no-new-privileges:true
    read_only: true
    tmpfs:
      - /tmp:size=64m
```

> **Note:** The `Dockerfile` itself cannot enforce `--cap-drop`. That is a
> runtime concern controlled by the container orchestrator. Always configure
> capability dropping in your `docker run` flags, Compose file, or Kubernetes
> `securityContext`.

## Filesystem Layout

The sandbox Landlock policy declares which paths are writable.
The agent's home directory (`/sandbox`) is writable by default:

| Path | Access | Purpose |
|------|--------|---------|
| `/sandbox` | read-write | Home directory — agents can create files and use standard home paths |
| `/sandbox/.openclaw` | read-write | Agent config, state, workspace, plugins |
| `/sandbox/.nemoclaw` | read-write | Plugin state and config; blueprints within are DAC-protected (root-owned) |
| `/tmp` | read-write | Temporary files and logs |

This writable default is intentional.
Seeing the sandbox user create files under `/sandbox` or `/sandbox/.openclaw` in a fresh sandbox does not mean Landlock failed.
Landlock still enforces the fixed read-only system paths below.

System paths remain read-only to prevent agents from:

- Replacing system binaries with trojanized versions
- Modifying DNS resolution or TLS trust stores
- Tampering with libraries or shell configuration outside `/sandbox`

The image build pre-creates locked shell init files `.bashrc` and `.profile` without proxy entries.
Runtime proxy configuration is sourced from system-wide shell hooks that read `/tmp/nemoclaw-proxy-env.sh`.

### Landlock Kernel Requirements

Landlock LSM requires Linux kernel 5.13 or later with `CONFIG_SECURITY_LANDLOCK=y`.
The NemoClaw sandbox policy uses `compatibility: best_effort`, which means Landlock enforcement is silently skipped on kernels that do not support it.

On such kernels, protection falls back to DAC (file ownership and permissions) only.
Files outside the writable paths would be inaccessible to the agent regardless of DAC permissions.

Operators should verify Landlock availability:

```console
$ ls /sys/kernel/security/landlock
```

For production deployments, kernel 5.13+ with Landlock enabled is strongly recommended.
The `test/e2e/e2e-cloud-experimental/checks/04-landlock-readonly.sh` script validates enforcement at runtime.

## References

- [#804](https://github.com/NVIDIA/NemoClaw/issues/804): Filesystem layout and Landlock policy
- [#807](https://github.com/NVIDIA/NemoClaw/issues/807): gcc in sandbox image
- [#808](https://github.com/NVIDIA/NemoClaw/issues/808): netcat in sandbox image
- [#809](https://github.com/NVIDIA/NemoClaw/issues/809): No process limit
- [#797](https://github.com/NVIDIA/NemoClaw/issues/797): Drop Linux capabilities
