sandbox.py

import os
import socket
import subprocess
import signal
import ctypes


def sandbox(target, *, privileged=True):
    CLONE_NEWNS      = 0x00020000 # New mount namespace group
    CLONE_NEWCGROUP  = 0x02000000 # New cgroup namespace
    CLONE_NEWUTS     = 0x04000000 # New utsname namespace
    CLONE_NEWIPC     = 0x08000000 # New ipc namespace
    CLONE_NEWUSER    = 0x10000000 # New user namespace
    CLONE_NEWPID     = 0x20000000 # New pid namespace
    CLONE_NEWNET     = 0x40000000 # New network namespace

    PR_SET_PDEATHSIG = 1

    euid = os.geteuid()
    egid = os.getegid()

    libc = ctypes.CDLL("libc.so.6")

    unshare_result = libc.unshare(
        CLONE_NEWUSER |
        CLONE_NEWNS |
        CLONE_NEWCGROUP |
        CLONE_NEWUTS |
        CLONE_NEWIPC |
        CLONE_NEWPID |
        CLONE_NEWNET
    )
    assert unshare_result == 0

    if os.fork():
        os.wait()
        return

    libc.prctl(PR_SET_PDEATHSIG, signal.SIGKILL)

    proc_values = {
        "/proc/self/setgroups": "deny",
        "/proc/self/uid_map": f"0 {euid} 1",
        "/proc/self/gid_map": f"0 {egid} 1",
    }
    for path, value in proc_values.items():
        with open(path, "w") as f:
            f.write(value)

    socket.sethostname("sandbox")
    subprocess.run(["/sbin/ip", "link", "set", "dev", "lo", "up"])

    if not privileged:
        unshare_result = libc.unshare(
            CLONE_NEWUSER
        )
        assert unshare_result == 0

        proc_values = {
            "/proc/self/setgroups": "deny",
            "/proc/self/uid_map": f"{euid} 0 1",
            "/proc/self/gid_map": f"{egid} 0 1",
        }
        for path, value in proc_values.items():
            with open(path, "w") as f:
                f.write(value)

    target()

    exit()


def target():
    print(os.getpid())

    os.execve("/bin/sh", ["/bin/sh"], os.environ)

    s = socket.create_server(("0.0.0.0", 80))
    input()
    print(s)


sandbox(target, privileged=True)