eval_workspace

A local HTTP service for running untrusted code in Python, JavaScript, Java, and Rust, with resource limits (CPU time, memory, wall-clock timeout, process count) and automatic toolchain provisioning — no root required.

What it does

• Multi-language execution: POST /run with {"language": "python", "code": "..."}, get back stdout/stderr/exit code
• Local sandboxing: each execution runs in its own process group with:
  • CPU time limit (RLIMIT_CPU)
  • Memory limit (RLIMIT_AS for Python/Java/Rust; Node uses --max-old-space-size instead — V8 reserves large virtual address space upfront, so RLIMIT_AS kills it before user code even runs)
  • Process count limit (fork-bomb protection, RLIMIT_NPROC)
  • Wall-clock timeout (catches processes waiting on I/O rather than burning CPU)
  • No inherited environment variables
  • Fresh temp directory per execution, deleted after
• Auto-provisioning toolchains: if a language runtime isn't found on PATH, it's downloaded as an official prebuilt binary into ~/.eval_workspace/toolchains/ — no system package manager, no root:
  • Node.js — official prebuilt tarball from nodejs.org
  • Java — Temurin JDK prebuilt tarball from Adoptium
  • Rust — via rustup, which already installs to user-space by design
  • Python — detected only; not auto-installed (no good universal static build to fetch)

Honest limitations — read this before relying on it

This is local (rlimit-based) sandboxing, not container/VM isolation. It reliably stops:

• Infinite loops (CPU limit + wall-clock timeout)
• Memory bombs (memory limit)
• Fork bombs (process count limit)
• Runaway processes waiting on stdin/network (wall-clock timeout)

It does not provide the same guarantees as Docker, gVisor, or Firecracker against a genuinely adversarial payload. There's no filesystem or namespace isolation beyond a scratch temp directory, and no syscall filtering. If your threat model includes deliberately hostile code trying to escape the sandbox (not just buggy/runaway code), you need real container/VM isolation — this tool does not provide that, and no amount of rlimit tuning makes it equivalent.

Java requires a specific class name. Submitted Java code must define public class Main — same convention most online judges use, since the filename must match the public class name to compile.

Network access is required to auto-install missing toolchains. If the machine running this has no outbound internet access, toolchain auto-install will fail cleanly (returns a clear error) rather than hang — but it can't conjure a compiler out of nowhere either. Pre-install what you need if you're running somewhere network-restricted.

What's actually been tested vs. what hasn't

To be direct about verification status:

Tested end-to-end, with real cross-checks:

• Python execution (basic output, errors)
• JavaScript execution via real Node.js (basic output, thrown errors)
• CPU-limit enforcement (infinite loop correctly killed)
• Wall-clock timeout enforcement (sleeping process correctly killed)
• Memory-limit enforcement (large allocation correctly triggers MemoryError)
• Clean error handling when a toolchain is missing (no crash, structured error returned)
• Clean error handling when network is unavailable during auto-install (no crash, structured error returned)
• Limit-clamping logic (abuse-scale requests get capped to sane maximums)

Not testable in the environment this was built in, and not yet verified on a real machine:

• Java compilation + execution (the build environment had a JRE but no JDK)
• Rust compilation + execution (Rust wasn't installed, and the sandbox had no network to fetch it)
• The actual toolchain download/extract logic for Node, JDK, and Rust (needs real network access to confirm the URLs and archive layouts are exactly right)
• The aiohttp HTTP server itself running live (aiohttp wasn't installable in the build sandbox — the route handlers are thin, tested wrappers around the executor, but the actual server process hasn't been smoke-tested)

If you're the first to run this somewhere with real network and a full toolchain set, treat the untested parts above as "should work, please verify" rather than "confirmed working."

Install

pip install eval-workspace

Usage

Check what's already available:

python -m eval_workspace.cli check

Pre-install any missing toolchains:

python -m eval_workspace.cli install

Start the server:

eval-workspace

Starts on http://127.0.0.1:8765 by default.

Run some code:

curl -X POST http://127.0.0.1:8765/run \
  -H "Content-Type: application/json" \
  -d '{"language": "python", "code": "print(2 + 2)"}'

{"ok": true, "stdout": "4\n", "stderr": "", "exit_code": 0, "timed_out": false, "duration_seconds": 0.05, "error": ""}

Custom limits per request:

curl -X POST http://127.0.0.1:8765/run \
  -H "Content-Type: application/json" \
  -d '{"language": "rust", "code": "fn main() { println!(\"hi\"); }", "limits": {"cpu_seconds": 10, "memory_mb": 512}}'

Check server + toolchain health:

curl http://127.0.0.1:8765/health

API reference

POST /run

Field	Type	Required	Notes
language	string	yes	python, javascript/js, java, or rust
code	string	yes	max 100,000 characters
stdin	string	no	piped to the program's stdin
limits	object	no	see below, all optional

limits fields (all clamped server-side to the max shown):

Field	Default	Max
cpu_seconds	5	30
memory_mb	256	1024
wall_clock_seconds	10	60
max_processes	16	32
max_output_bytes	200000	1000000

GET /languages

Returns the list of supported language identifiers.

GET /health

Returns toolchain availability for each language.

License

MIT