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#!/usr/bin/python3
# Copyright 2024 Helmut Grohne <helmut@subdivi.de>
# SPDX-License-Identifier: GPL-3
"""Map all available ranges from /etc/subuid and /etc/subgid as identity and
run a given command with all capabilities (including CAP_DAC_OVERRIDE)
inherited.
"""
import os
import sys
if __file__.split("/")[-2:-1] == ["examples"]:
sys.path.insert(0, "/".join(__file__.split("/")[:-2]))
import linuxnamespaces
def main() -> None:
# Construct an identity mapping of all available user/group ids
uidmap = [
linuxnamespaces.IDMapping(os.getuid(), os.getuid(), 1),
*(
linuxnamespaces.IDMapping(start, start, count)
for start, count
in linuxnamespaces.IDAllocation.loadsubid("uid").ranges
),
]
gidmap = [
linuxnamespaces.IDMapping(os.getgid(), os.getgid(), 1),
*(
linuxnamespaces.IDMapping(start, start, count)
for start, count
in linuxnamespaces.IDAllocation.loadsubid("gid").ranges
),
]
linuxnamespaces.unshare_user_idmap(uidmap, gidmap)
# We haven't changed uid. We still are non-root, but the user namespace
# augmented our permitted and effective capabilities! Add them to the
# inheritable set.
capabilities = linuxnamespaces.CapabilitySets.get()
capabilities.inheritable = capabilities.permitted & capabilities.effective
capabilities.set()
# Add all inheritable capabilities to the ambient set.
caps = capabilities.inheritable
while caps:
cap = caps & (~caps + 1)
caps ^= cap
linuxnamespaces.call_libc(
"prctl",
47, # PR_CAP_AMBIENT
2, # PR_CAP_AMBIENT_RAISE
cap.bit_length() - 1,
0,
0,
)
if len(sys.argv) > 1:
os.execvp(sys.argv[1], sys.argv[1:])
else:
os.execvp(os.environ["SHELL"], [os.environ["SHELL"]])
if __name__ == "__main__":
main()
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