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#!/usr/bin/python3
# Copyright 2024 Helmut Grohne <helmut@subdivi.de>
# SPDX-License-Identifier: GPL-3
"""Unshare a cgroup (and user) namespace such that the entire cgroup hierarchy
(inside the namespace) becomes writeable to the user.
"""
import asyncio
import os
import pathlib
import sys
if __file__.split("/")[-2:-1] == ["examples"]:
sys.path.insert(0, "/".join(__file__.split("/")[:-2]))
import linuxnamespaces
import linuxnamespaces.systemd
def get_cgroup(pid: int = -1) -> pathlib.PurePath:
"""Look up the cgroup that the given pid or the running process belongs
to.
"""
return pathlib.PurePath(
pathlib.Path(
f"/proc/{pid}/cgroup" if pid > 0 else "/proc/self/cgroup"
).read_text().split(":", 2)[2].strip()
)
def main() -> None:
mycgroup = get_cgroup()
if not os.access(
pathlib.Path("/sys/fs/cgroup") / mycgroup.relative_to("/"),
os.W_OK,
):
# For some shells - notably from graphical desktop environments, the
# hierarchy is immediately writeable. For others, we may create a scope
# unit.
try:
asyncio.run(
linuxnamespaces.systemd.start_transient_unit(
f"cgroup-{os.getpid()}.scope",
properties={"Delegate": True},
),
)
mycgroup = get_cgroup()
except NotImplementedError:
linuxnamespaces.systemd.reexec_as_transient_unit(
properties={"Delegate": True}
)
namespaces = (
linuxnamespaces.CloneFlags.NEWUSER
| linuxnamespaces.CloneFlags.NEWNS
| linuxnamespaces.CloneFlags.NEWCGROUP
)
linuxnamespaces.unshare_user_idmap(
[linuxnamespaces.IDMapping(os.getuid(), os.getuid(), 1)],
[linuxnamespaces.IDMapping(os.getgid(), os.getgid(), 1)],
namespaces,
)
linuxnamespaces.populate_sys("/", "/", namespaces, mycgroup)
os.execlp(os.environ["SHELL"], os.environ["SHELL"])
if __name__ == "__main__":
main()
|
