tarfilter --idshift now provides taridshift

coverage.py

@@ -96,7 +96,6 @@ def main():
     # copy over files from git or as distributed
     for (git, dist, target) in [
         ("./mmdebstrap", "/usr/bin/mmdebstrap", "mmdebstrap"),
-        ("./taridshift", "/usr/bin/mmtaridshift", "taridshift"),
         ("./tarfilter", "/usr/bin/mmtarfilter", "tarfilter"),
         (
             "./proxysolver",

coverage.txt

@@ -52,7 +52,7 @@ Skip-If:
  fmt == "squashfs" and dist == "oldstable" # squashfs-tools-ng is not available
  fmt == "ext2" and dist == "oldstable" # genext2fs does not support SOURCE_DATE_EPOCH
 
-Test: taridshift-utility
+Test: tarfilter-idshift
 Needs-QEMU: true
 Skip-If: dist == "oldstable" # python3 tarfile module does not preserve xattrs
 

tarfilter

@@ -68,7 +68,10 @@ Both types of options use Unix shell-style wildcards:
 Thirdly, strip leading directory components off of tar members. Just as with
 GNU tar --strip-components, tar members that have less or equal components in
 their path are not passed through.
-"""
+
+Lastly, shift user id and group id of each entry by the value given by the
+--idshift argument. The resulting uid or gid must not be negative.
+""",
     )
     parser.add_argument(
         "--path-exclude",
@@ -100,6 +103,12 @@ their path are not passed through.
         type=int,
         help="Strip NUMBER leading components from file names",
     )
+    parser.add_argument(
+        "--idshift",
+        metavar="NUM",
+        type=int,
+        help="Integer value by which to shift the uid and gid of each entry",
+    )
     args = parser.parse_args()
     if (
         not hasattr(args, "pathfilter")
@@ -165,6 +174,15 @@ their path are not passed through.
                 for k, v in member.pax_headers.items()
                 if not pax_filter_should_skip(k)
             }
+            if args.idshift:
+                if args.idshift < 0 and -args.idshift > member.uid:
+                    print("uid cannot be negative", file=sys.stderr)
+                    exit(1)
+                if args.idshift < 0 and -args.idshift > member.gid:
+                    print("gid cannot be negative", file=sys.stderr)
+                    exit(1)
+                member.uid += args.idshift
+                member.gid += args.idshift
             if member.isfile():
                 with in_tar.extractfile(member) as file:
                     out_tar.addfile(member, file)

taridshift

@@ -1,67 +0,0 @@
-#!/usr/bin/env python3
-#
-# This script is in the public domain
-#
-# Author: Johannes Schauer Marin Rodrigues <josch@mister-muffin.de>
-#
-# This script accepts a tarball on standard input and prints a tarball on
-# standard output with the same contents but all uid and gid ownership
-# information shifted by the value given as first command line argument.
-#
-# A tool like this should be written in C but libarchive has issues:
-# https://github.com/libarchive/libarchive/issues/587
-# https://github.com/libarchive/libarchive/pull/1288/ (needs 3.4.1)
-# Should these issues get fixed, then a good template is tarfilter.c in the
-# examples directory of libarchive.
-#
-# We are not using Perl either, because Archive::Tar slurps the whole tarball
-# into memory.
-#
-# We could also use Go but meh...
-# https://stackoverflow.com/a/59542307/784669
-
-import tarfile
-import sys
-import argparse
-
-
-def main():
-    parser = argparse.ArgumentParser(
-        description="""\
-Accepts a tarball on standard input and prints a tarball on standard output
-with the same contents but all uid and gid ownership information shifted by the
-value given as first command line argument.
-"""
-    )
-    parser.add_argument(
-        "idshift",
-        metavar="NUM",
-        type=int,
-        help="Integer value by which to shift the uid and gid of each entry",
-    )
-    args = parser.parse_args()
-
-    # starting with Python 3.8, the default format became PAX_FORMAT, so this
-    # is only for compatibility with older versions of Python 3
-    with tarfile.open(fileobj=sys.stdin.buffer, mode="r|*") as in_tar, tarfile.open(
-        fileobj=sys.stdout.buffer, mode="w|", format=tarfile.PAX_FORMAT
-    ) as out_tar:
-        for member in in_tar:
-            if args.idshift < 0 and -args.idshift > member.uid:
-                print("uid cannot be negative", file=sys.stderr)
-                exit(1)
-            if args.idshift < 0 and -args.idshift > member.gid:
-                print("gid cannot be negative", file=sys.stderr)
-                exit(1)
-
-            member.uid += args.idshift
-            member.gid += args.idshift
-            if member.isfile():
-                with in_tar.extractfile(member) as file:
-                    out_tar.addfile(member, file)
-            else:
-                out_tar.addfile(member)
-
-
-if __name__ == "__main__":
-    main()

tests/tarfilter-idshift

@@ -10,12 +10,12 @@ adduser --gecos user --disabled-password user
 echo user:100000:65536 | cmp /etc/subuid -
 echo user:100000:65536 | cmp /etc/subgid -
 sysctl -w kernel.unprivileged_userns_clone=1
-# include iputils-ping so that we can verify that taridshift does not remove
+# include iputils-ping so that we can verify that tarfilter does not remove
 # extended attributes
 # run through tarshift no-op to create a tarball that should be bit-by-bit
-# identical to a round trip through "taridshift X" and "taridshift -X"
+# identical to a round trip through "tarfilter --idshift X" and "tarfilter --idshift -X"
 runuser -u user -- {{ CMD }} --mode=unshare --variant=apt --include=iputils-ping {{ DIST }} - {{ MIRROR }} \
-	| ./taridshift 0 > /tmp/debian-chroot.tar
+	| ./tarfilter --idshift 0 > /tmp/debian-chroot.tar
 # make sure that xattrs are set in the original tarball
 mkdir /tmp/debian-chroot
 tar --xattrs --xattrs-include='*' --directory /tmp/debian-chroot -xf /tmp/debian-chroot.tar ./bin/ping
@@ -25,9 +25,9 @@ rm /tmp/debian-chroot/bin/ping
 rmdir /tmp/debian-chroot/bin
 rmdir /tmp/debian-chroot
 # shift the uid/gid forward by 100000 and backward by 100000
-./taridshift 100000 < /tmp/debian-chroot.tar > /tmp/debian-chroot-shifted.tar
+./tarfilter --idshift 100000 < /tmp/debian-chroot.tar > /tmp/debian-chroot-shifted.tar
-./taridshift -100000 < /tmp/debian-chroot-shifted.tar > /tmp/debian-chroot-shiftedback.tar
+./tarfilter --idshift -100000 < /tmp/debian-chroot-shifted.tar > /tmp/debian-chroot-shiftedback.tar
-# the tarball before and after the roundtrip through taridshift should be bit
+# the tarball before and after the roundtrip through tarfilter should be bit
 # by bit identical
 cmp /tmp/debian-chroot.tar /tmp/debian-chroot-shiftedback.tar
 # manually adjust uid/gid and compare "tar -t" output