sloptrap

sloptrap runs the OpenAI Codex CLI inside a container with a predictable and locked-down filesystem view. The launcher script (sloptrap) resolves the project manifest, builds the support image directly, and starts Codex with the requested target (defaults to run). Hardened parsing blocks container escapes via manifest or ignore directives, verifies the downloaded Codex binary, and keeps the runtime environment minimal.

Dependencies

• Podman ≥ 4 (sloptrap refuses to run without it unless you explicitly override SLOPTRAP_CONTAINER_ENGINE).
• GNU bash, curl, tar, sha256sum, realpath (from GNU coreutils), and jq on the host.

Tip: set SLOPTRAP_CONTAINER_ENGINE=<engine> if you need to override the default Podman requirement.

macOS setup

sloptrap targets GNU userland. On macOS, install the GNU tools via Homebrew and the launcher will prepend their gnubin paths automatically:

brew install coreutils gnu-tar jq

Quick Start

1. Place sloptrap somewhere on your PATH/shared drive, for example with make install (the helper payload, helper Dockerfile, and Codex binary handling are bundled into the launcher).
2. (Optional) Create a project-specific manifest and ignore file:

   cat > path/to/project/.sloptrap <<'EOF'
   name=path/to/project
   packages_extra=make
   EOF
   
   cat > path/to/project/.sloptrapignore <<'EOF'
   .git/
   secrets/
   EOF
   

3. Run ./sloptrap path/to/project. On the first invocation sloptrap:
   • builds path/to/project-sloptrap-image if missing,
   • verifies the Codex binary hash,
   • creates ${HOME}/.codex, prepares a per-project state directory, and runs login if ${HOME}/.codex/auth.json is missing or empty.

Use ./sloptrap path/to/project shell to enter a troubleshooting shell inside the container or ./sloptrap path/to/project clean to remove cached images and state.

How It Works

• The project directory mounts at /workspace; project-scoped Codex state mounts at /codex from ${HOME}/.codex/sloptrap/state/<project-hash>, and shared auth mounts from ${HOME}/.codex/auth.json to /codex/auth.json.
• .sloptrapignore entries (if present in your project) are overlaid by tmpfs (for directories) or empty bind mounts (for files) so Codex cannot read the masked content.
• sloptrap launches containers on an isolated network (bridge on Docker, slirp4netns on Podman) with --cap-drop=ALL, --security-opt no-new-privileges, a read-only root filesystem, and tmpfs-backed /tmp, /run, and /run/lock. Projects that explicitly set allow_host_network=true in their manifest opt into --network host.
• The helper Dockerfile is embedded inside sloptrap; set SLOPTRAP_DOCKERFILE_PATH=/path/to/custom/Dockerfile if you need to supply your own recipe. The default image installs curl, bash, ca-certificates, libstdc++6, git, ripgrep, xxd, and file, so most debugging helpers are already available without adding packages_extra.
• The container user matches the host UID/GID (--userns=keep-id on Podman or --user UID:GID on Docker).
• The runtime environment is fixed to HOME/XDG variables pointing at /codex; manifest-controlled environment injection is disabled.

.sloptrap Manifest Reference

The manifest is optional. When absent, sloptrap derives:

• name = basename(project directory)
• packages_extra = "" (none)
• capabilities = "" (none) If a build is requested and no .sloptrap exists, sloptrap prompts to create one interactively.

Supported keys when the manifest is present:

Key	Default	Notes
name	project directory name	Must match ^[A-Za-z0-9_.-]+$. Used for image/container naming.
packages_extra	empty	Additional Debian packages installed during docker/podman build. Tokens must be alphanumeric plus +.-.
capabilities	empty	Optional privileged features. Supported values are apt-install and packet-capture. Capability-enabled runs require Podman. When packet-capture is combined with allow_host_network=true, sloptrap shows a runtime warning with concrete consequences and requires an interactive acknowledgement on every run.
allow_host_network	false	true opts into --network host; keep false unless the project absolutely requires direct access to host-local services.

Values containing $, `, or newlines are rejected to prevent command injection. Setting illegal keys or malformed values aborts the run before containers start. sloptrap always runs Codex with --sandbox danger-full-access --ask-for-approval never. codex_args is deprecated and rejected if present.

Capability trust is local state, not part of the repository. Builds for manifests that request capabilities require either an interactive trust confirmation or --trust-capabilities. Once the current manifest is trusted, its requested capabilities are enabled automatically for that project configuration. The allow_host_network=true plus packet-capture combination still requires a separate interactive acknowledgement each time a runtime container is launched.

.sloptrapignore

• Parsed using gitignore-style globbing with support for !negation.
• Entries must stay within the project root after resolving symlinks; attempts to reference ./.., absolute paths, or symlink escapes raise errors.
• Directory matches become --mount type=tmpfs,target=/workspace/<path>. File matches bind to empty files within .sloptrap-ignores/session-<pid>/.
• The helper directory is removed automatically on exit or during ./sloptrap <project> clean.

CLI Reference

./sloptrap [--dry-run] [--print-config] [--trust-capabilities] <code-directory> [target ...]

Options:

• --dry-run — print the container/engine commands that would run without executing them.
• --print-config — output the resolved manifest values, defaults, and ignore list.
• --trust-capabilities — trust the manifest's requested capabilities for the current build flow.
• -h, --help — display usage.
• -- — stop option parsing; remaining arguments are treated as targets.

Behaviour:

• Missing manifests are treated as default configuration; when a build is requested, sloptrap runs the interactive wizard if a TTY is available, otherwise it warns and continues with defaults.
• SLOPTRAP_CONTAINER_ENGINE overrides engine auto-detection.
• If ${HOME}/.codex/auth.json is absent or empty, sloptrap prepends a login run before executing your targets.
• Fresh interactive run sessions receive a launcher-generated startup prompt telling the agent it is inside sloptrap, summarising the resolved manifest/runtime state, and pointing it at /workspace/.sloptrap for exact project configuration. resume does not inject that prompt again.
• Exit status mirrors the last target executed; errors in parsing or setup abort early with a message.

--print-config fields include manifest_present=true|false, requested/enabled capability lists, trust status, resolved paths, and the sanitised ignore mount roots so you can confirm what will be hidden inside the container.

Regression Suite

• make regress (or tests/run_tests.sh) runs shellcheck against sloptrap and then executes every scenario in tests/run_tests.sh, including the container build path check.
• The suite must pass cleanly; ShellCheck diagnostics or scenario regressions cause a non-zero exit and should be fixed before shipping changes.

Built-in Targets

Targets are supplied after the code directory. When omitted, sloptrap defaults to run.

Target	Description
build	Download Codex (if missing), verify SHA-256, and build the container image.
build-if-missing	No-op when the image already exists; otherwise delegates to build.
rebuild	Rebuild the image from scratch (--no-cache).
run	Default goal. Runs the container with Codex using sloptrap's built-in runtime flags.
resume <session-id>	Continues a Codex session by running codex resume <session-id> inside the container (builds if needed).
login	Starts Codex in login mode to bootstrap shared ${HOME}/.codex/auth.json credentials.
shell	Launches /bin/bash inside the container for debugging.
wizard	Creates or updates .sloptrap interactively (no build); rerun build or rebuild afterward.
stop	Best-effort stop of the running container (if any).
clean	Removes .sloptrap-ignores, deletes the container/image, and stops the container if necessary.

The launcher executes targets sequentially, so ./sloptrap repo build run performs an explicit rebuild before invoking Codex. Extra targets may be added in the future; unknown names fail fast.

Capability Helpers

When the current manifest's capabilities are trusted and enabled, the container includes helper commands:

• slop-apt install <package...> for session-scoped package installation.
• slopcap capture --interface <iface> [--filter <expr>] [--output <path>] [--stdout] for non-promiscuous packet capture through a dedicated helper container. Host-network captures require an explicit acknowledgement each run.

Execution Environment

• Container engine: Podman or Docker for standard runs. Capability-enabled runs require Podman. Podman uses --userns=keep-id; Docker receives the equivalent --user UID:GID for standard runs.
• Filesystem view: the project directory mounts at /workspace; ${HOME}/.codex/sloptrap/state/<project-hash> mounts at /codex; ${HOME}/.codex/auth.json mounts at /codex/auth.json.
• Ignore filter: .sloptrapignore entries are overlaid with tmpfs directories or empty bind mounts so data remains unavailable to Codex.
• Network: isolated networking is used by default; allow_host_network=true opts into --network host. When packet-capture is enabled, sloptrap starts a separate capture helper container in the same Podman pod so the main Codex container does not receive NET_RAW.
• Process context: standard runs drop capabilities, set no-new-privileges, use a read-only root filesystem, and keep scratch paths (/tmp, /run, /run/lock) on tmpfs. Capability-enabled runs may selectively add the runtime options required for the requested capability.
• Codex configuration: runtime flags are fixed to --sandbox danger-full-access --ask-for-approval never. Persistent Codex state is project-scoped under ${HOME}/.codex/sloptrap/state/, while credentials are shared via ${HOME}/.codex/auth.json and mounted read-only except during the login target.

Threat Model and Limits

• Outbound disclosure: prompts and referenced data travel from the container to the configured LLM endpoint. Any file content within /workspace or environment data exposed to the process can appear in that traffic.
• Shared storage: /workspace, project-scoped /codex, and /codex/auth.json are host mounts. Files written to these locations become visible on the host and to the LLM provider through prompts.
• Environment surface: the container receives a minimal fixed environment (HOME/XDG paths, CODEX_HOME). The manifest no longer allows injecting additional environment variables.
• Process isolation: standard runs keep a read-only root filesystem and no extra Linux capabilities. Capability-enabled runs deliberately relax specific runtime controls for the enabled feature, so they should be treated as a stronger trust decision than a default session. packet-capture now runs in a dedicated helper container so the main Codex container does not hold raw-socket capability.
• Networking stance: traffic is unrestricted once it leaves the container. sloptrap does not enforce an allowlist or DNS policy. Host networking is opt-in per manifest; when it is combined with packet-capture, sloptrap warns and requires an explicit acknowledgement for each runtime launch because the capture helper will have raw packet access in the host namespace and may observe plaintext traffic or inject spoofed packets. If you require an offline or firewalled workflow, sloptrap is not an appropriate launcher.
• Persistence: Codex history and logs accumulate per project under ${HOME}/.codex/sloptrap/state/. Sensitive prompts recorded on disk remain on the host after the session. Because .git/ is ignored inside the container, any historical secrets in Git objects stay outside the LLM context unless explicitly surfaced in the working tree.
• Codex cache hygiene: per-project state mounts remain writable by the container and hold prompts/history/state, while ${HOME}/.codex/auth.json holds shared credentials. Rotate credentials regularly and protect both locations.
• Secret scanning: sloptrap does not perform secret discovery or redaction; any credentials present in the project remain available to Codex and the upstream provider.
• Local model exception: pointing Codex at a local or self-hosted model keeps data within the host network boundary, but the filesystem and environment exposure described above is unchanged.

These constraints focus on limiting host data exposure to the Codex session while acknowledging that any material introduced into the context window may leave the environment through the upstream API.