sandboxkit

Sandboxed code execution on Linux. Run a Python callable in a forked child or an argv command in a subprocess, isolated by namespaces, rlimits and Landlock. Rootless by default: an unprivileged user namespace gives the payload uid 0 inside its own mount, pid, network (no connectivity), ipc and uts namespaces.

Requires Python 3.10+ and Linux, with unprivileged user namespaces for the default configuration. Landlock support comes from landlockpy and is used when the running kernel has it.

Install

pip install sandboxkit

Usage

from sandboxkit import RLimits, Sandbox

sandbox = Sandbox(
    rlimits=RLimits(cpu_seconds=5, memory_bytes=64 << 20),
    timeout=10,
)
result = sandbox.run_argv(["/usr/bin/python3", "-c", "print(2 + 2)"])
assert result.ok and result.stdout == b"4\n"

# or run a callable. An OSError inside surfaces as result.errno
result = sandbox.run(lambda: print("running as uid", __import__("os").getuid()))

• namespaces picks the unshare(2) set. Namespace.CGROUP is opt-in.
• The real uid/gid is mapped to 0 inside, written by the parent through /proc// so it works on kernels that reject self-mapping.
• strict=True raises SandboxError on any namespace failure. strict=False (default) skips refused namespaces with a stderr note.
• landlock= takes a configured but unenforced landlockpy.Ruleset, restricted in the payload only, so the object stays usable.
• hostname= sets the UTS hostname, mount_proc=True mounts a fresh /proc, timeout= kills the whole sandbox tree.
• namespaces_supported() probes which namespaces this kernel actually lets the caller create; userns_available() checks the USER path.

Documentation

• API: docstrings in src/sandboxkit/, mostly sandbox.py
• namespaces(7): https://man7.org/linux/man-pages/man7/namespaces.7.html
• user_namespaces(7): https://man7.org/linux/man-pages/man7/user_namespaces.7.html
• unshare(2): https://man7.org/linux/man-pages/man2/unshare.2.html
• setrlimit(2): https://man7.org/linux/man-pages/man2/setrlimit.2.html
• Landlock: https://docs.kernel.org/userspace-api/landlock.html

License: 0BSD.