tarfilter --idshift now provides taridshift
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5 changed files with 26 additions and 76 deletions
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@ -96,7 +96,6 @@ def main():
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# copy over files from git or as distributed
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for (git, dist, target) in [
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("./mmdebstrap", "/usr/bin/mmdebstrap", "mmdebstrap"),
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("./taridshift", "/usr/bin/mmtaridshift", "taridshift"),
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("./tarfilter", "/usr/bin/mmtarfilter", "tarfilter"),
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(
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"./proxysolver",
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@ -52,7 +52,7 @@ Skip-If:
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fmt == "squashfs" and dist == "oldstable" # squashfs-tools-ng is not available
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fmt == "ext2" and dist == "oldstable" # genext2fs does not support SOURCE_DATE_EPOCH
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Test: taridshift-utility
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Test: tarfilter-idshift
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Needs-QEMU: true
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Skip-If: dist == "oldstable" # python3 tarfile module does not preserve xattrs
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20
tarfilter
20
tarfilter
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@ -68,7 +68,10 @@ Both types of options use Unix shell-style wildcards:
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Thirdly, strip leading directory components off of tar members. Just as with
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GNU tar --strip-components, tar members that have less or equal components in
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their path are not passed through.
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"""
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Lastly, shift user id and group id of each entry by the value given by the
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--idshift argument. The resulting uid or gid must not be negative.
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""",
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)
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parser.add_argument(
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"--path-exclude",
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@ -100,6 +103,12 @@ their path are not passed through.
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type=int,
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help="Strip NUMBER leading components from file names",
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)
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parser.add_argument(
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"--idshift",
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metavar="NUM",
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type=int,
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help="Integer value by which to shift the uid and gid of each entry",
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)
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args = parser.parse_args()
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if (
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not hasattr(args, "pathfilter")
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@ -165,6 +174,15 @@ their path are not passed through.
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for k, v in member.pax_headers.items()
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if not pax_filter_should_skip(k)
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}
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if args.idshift:
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if args.idshift < 0 and -args.idshift > member.uid:
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print("uid cannot be negative", file=sys.stderr)
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exit(1)
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if args.idshift < 0 and -args.idshift > member.gid:
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print("gid cannot be negative", file=sys.stderr)
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exit(1)
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member.uid += args.idshift
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member.gid += args.idshift
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if member.isfile():
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with in_tar.extractfile(member) as file:
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out_tar.addfile(member, file)
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67
taridshift
67
taridshift
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@ -1,67 +0,0 @@
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#!/usr/bin/env python3
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#
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# This script is in the public domain
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#
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# Author: Johannes Schauer Marin Rodrigues <josch@mister-muffin.de>
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#
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# This script accepts a tarball on standard input and prints a tarball on
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# standard output with the same contents but all uid and gid ownership
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# information shifted by the value given as first command line argument.
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#
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# A tool like this should be written in C but libarchive has issues:
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# https://github.com/libarchive/libarchive/issues/587
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# https://github.com/libarchive/libarchive/pull/1288/ (needs 3.4.1)
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# Should these issues get fixed, then a good template is tarfilter.c in the
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# examples directory of libarchive.
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#
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# We are not using Perl either, because Archive::Tar slurps the whole tarball
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# into memory.
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#
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# We could also use Go but meh...
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# https://stackoverflow.com/a/59542307/784669
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import tarfile
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import sys
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import argparse
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def main():
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parser = argparse.ArgumentParser(
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description="""\
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Accepts a tarball on standard input and prints a tarball on standard output
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with the same contents but all uid and gid ownership information shifted by the
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value given as first command line argument.
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"""
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)
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parser.add_argument(
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"idshift",
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metavar="NUM",
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type=int,
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help="Integer value by which to shift the uid and gid of each entry",
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)
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args = parser.parse_args()
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# starting with Python 3.8, the default format became PAX_FORMAT, so this
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# is only for compatibility with older versions of Python 3
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with tarfile.open(fileobj=sys.stdin.buffer, mode="r|*") as in_tar, tarfile.open(
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fileobj=sys.stdout.buffer, mode="w|", format=tarfile.PAX_FORMAT
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) as out_tar:
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for member in in_tar:
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if args.idshift < 0 and -args.idshift > member.uid:
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print("uid cannot be negative", file=sys.stderr)
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exit(1)
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if args.idshift < 0 and -args.idshift > member.gid:
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print("gid cannot be negative", file=sys.stderr)
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exit(1)
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member.uid += args.idshift
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member.gid += args.idshift
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if member.isfile():
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with in_tar.extractfile(member) as file:
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out_tar.addfile(member, file)
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else:
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out_tar.addfile(member)
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if __name__ == "__main__":
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main()
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@ -10,12 +10,12 @@ adduser --gecos user --disabled-password user
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echo user:100000:65536 | cmp /etc/subuid -
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echo user:100000:65536 | cmp /etc/subgid -
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sysctl -w kernel.unprivileged_userns_clone=1
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# include iputils-ping so that we can verify that taridshift does not remove
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# include iputils-ping so that we can verify that tarfilter does not remove
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# extended attributes
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# run through tarshift no-op to create a tarball that should be bit-by-bit
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# identical to a round trip through "taridshift X" and "taridshift -X"
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# identical to a round trip through "tarfilter --idshift X" and "tarfilter --idshift -X"
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runuser -u user -- {{ CMD }} --mode=unshare --variant=apt --include=iputils-ping {{ DIST }} - {{ MIRROR }} \
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| ./taridshift 0 > /tmp/debian-chroot.tar
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| ./tarfilter --idshift 0 > /tmp/debian-chroot.tar
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# make sure that xattrs are set in the original tarball
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mkdir /tmp/debian-chroot
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tar --xattrs --xattrs-include='*' --directory /tmp/debian-chroot -xf /tmp/debian-chroot.tar ./bin/ping
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@ -25,9 +25,9 @@ rm /tmp/debian-chroot/bin/ping
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rmdir /tmp/debian-chroot/bin
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rmdir /tmp/debian-chroot
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# shift the uid/gid forward by 100000 and backward by 100000
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./taridshift 100000 < /tmp/debian-chroot.tar > /tmp/debian-chroot-shifted.tar
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./taridshift -100000 < /tmp/debian-chroot-shifted.tar > /tmp/debian-chroot-shiftedback.tar
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# the tarball before and after the roundtrip through taridshift should be bit
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./tarfilter --idshift 100000 < /tmp/debian-chroot.tar > /tmp/debian-chroot-shifted.tar
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./tarfilter --idshift -100000 < /tmp/debian-chroot-shifted.tar > /tmp/debian-chroot-shiftedback.tar
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# the tarball before and after the roundtrip through tarfilter should be bit
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# by bit identical
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cmp /tmp/debian-chroot.tar /tmp/debian-chroot-shiftedback.tar
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# manually adjust uid/gid and compare "tar -t" output
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