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Properly implement --skip=output/dev and add --skip=output/mknod

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- the first implementation of --skip=output/dev was broken in root mode
 - add tests
 - add documentation
This commit is contained in:
Johannes Schauer Marin Rodrigues 2023-09-27 13:52:20 +02:00
parent cee8b67045
commit bf41b91e6f
Signed by untrusted user: josch
GPG key ID: F2CBA5C78FBD83E1
4 changed files with 208 additions and 57 deletions
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6
coverage.txt
View file

@ -422,3 +422,9 @@ Skip-If: hostarch in ["i386", "armel", "armhf", "mipsel"] # #1023286
Test: auto-mode-as-normal-user
Modes: auto
Test: skip-output-dev
Modes: root unshare
Test: skip-output-mknod
Modes: root unshare

194
mmdebstrap
View file

@ -3262,6 +3262,52 @@ sub run_cleanup() {
closedir($dh);
}
}
if (any { $_ eq 'cleanup/dev' } @{ $options->{skip} }) {
info "skipping cleanup/dev as requested";
} else {
# By default, tar is run with --exclude=./dev because we create the
# ./dev entries ourselves using @devfiles. But if --skip=output/dev is
# used, --exclude=./dev is not passed so that the chroot includes ./dev
# as created by base-files. But if mknod was available (for example
# when running as root) then ./dev will also include the @devfiles
# entries created by run_setup() and thus the resulting tarball will
# include things inside ./dev despite the user having supplied
# --skip=output/dev. So if --skip=output/dev was passed and if a
# tarball is to be created, we need to make sure to clean up the
# ./dev entries that were created in run_setup(). This is not done
# when creating a directory because in that case we want to do the
# same as debootstrap and create a directory including device nodes.
if ($options->{format} ne 'directory' && any { $_ eq 'output/dev' }
@{ $options->{skip} }) {
foreach my $file (@devfiles) {
my ($fname, $mode, $type, $linkname, $devmajor, $devminor)
= @{$file};
if (!-e "$options->{root}/dev/$fname") {
next;
}
# do not remove ./dev itself
if ($fname eq "") {
next;
}
if ($type == 0) { # normal file
error "type 0 not implemented";
} elsif ($type == 1) { # hardlink
error "type 1 not implemented";
} elsif (any { $_ eq $type } (2, 3, 4))
{ # symlink, char, block
unlink "$options->{root}/dev/$fname"
or error "failed to unlink ./dev/$fname: $!";
} elsif ($type == 5) { # directory
rmdir "$options->{root}/dev/$fname"
or error "failed to unlink ./dev/$fname: $!";
} else {
error "unsupported type: $type";
}
}
}
}
return;
}
@ -4445,6 +4491,7 @@ sub main() {
include => [],
architectures => [$hostarch],
mode => 'auto',
format => 'auto',
dpkgopts => [],
aptopts => [],
apttrusted => $apttrusted,
@ -4458,7 +4505,6 @@ sub main() {
skip => [],
};
my $logfile = undef;
my $format = 'auto';
Getopt::Long::Configure('default', 'bundling', 'auto_abbrev',
'ignore_case_always');
GetOptions(
@ -4541,7 +4587,7 @@ sub main() {
'q|quiet' => sub { $verbosity_level = 0; },
'v|verbose' => sub { $verbosity_level = 2; },
'd|debug' => sub { $verbosity_level = 3; },
'format=s' => \$format,
'format=s' => \$options->{format},
'logfile=s' => \$logfile,
# no-op options so that mmdebstrap can be used with
# sbuild-createchroot --debootstrap=mmdebstrap
@ -4708,16 +4754,16 @@ sub main() {
}
# sqfs is an alias for squashfs
if ($format eq 'sqfs') {
$format = 'squashfs';
if ($options->{format} eq 'sqfs') {
$options->{format} = 'squashfs';
}
# dir is an alias for directory
if ($format eq 'dir') {
$format = 'directory';
if ($options->{format} eq 'dir') {
$options->{format} = 'directory';
}
my @valid_formats
= ('auto', 'directory', 'tar', 'squashfs', 'ext2', 'null');
if (none { $_ eq $format } @valid_formats) {
if (none { $_ eq $options->{format} } @valid_formats) {
error "invalid format. Choose from " . (join ', ', @valid_formats);
}
@ -5484,7 +5530,7 @@ sub main() {
my $tar_compressor = get_tar_compressor($options->{target});
# figure out the right format
if ($format eq 'auto') {
if ($options->{format} eq 'auto') {
# (stat(...))[6] is the device identifier which contains the major and
# minor numbers for character special files
# major 1 and minor 3 is /dev/null on Linux
@ -5493,7 +5539,7 @@ sub main() {
and -c '/dev/null'
and major((stat("/dev/null"))[6]) == 1
and minor((stat("/dev/null"))[6]) == 3) {
$format = 'null';
$options->{format} = 'null';
} elsif ($options->{target} eq '-'
and $OSNAME eq 'linux'
and major((stat(STDOUT))[6]) == 1
@ -5501,9 +5547,9 @@ sub main() {
# by checking the major and minor number of the STDOUT fd we also
# can detect redirections to /dev/null and choose the null format
# accordingly
$format = 'null';
$options->{format} = 'null';
} elsif ($options->{target} ne '-' and -d $options->{target}) {
$format = 'directory';
$options->{format} = 'directory';
} elsif (
defined $tar_compressor
or $options->{target} =~ /\.tar$/
@ -5511,7 +5557,7 @@ sub main() {
or -p $options->{target} # named pipe (fifo)
or -c $options->{target} # character special like /dev/null
) {
$format = 'tar';
$options->{format} = 'tar';
# check if the compressor is installed
if (defined $tar_compressor) {
my $pid = fork() // error "fork() failed: $!";
@ -5531,7 +5577,7 @@ sub main() {
}
}
} elsif ($options->{target} =~ /\.(squashfs|sqfs)$/) {
$format = 'squashfs';
$options->{format} = 'squashfs';
# check if tar2sqfs is installed
my $pid = fork() // error "fork() failed: $!";
if ($pid == 0) {
@ -5547,7 +5593,7 @@ sub main() {
error("failed to start tar2sqfs --version");
}
} elsif ($options->{target} =~ /\.ext2$/) {
$format = 'ext2';
$options->{format} = 'ext2';
# check if the installed version of genext2fs supports tarballs on
# stdin
(undef, my $filename) = tempfile(
@ -5568,32 +5614,34 @@ sub main() {
error "genext2fs failed with exit status: $exitstatus";
}
} else {
$format = 'directory';
$options->{format} = 'directory';
}
info "automatically chosen format: $format";
info "automatically chosen format: $options->{format}";
}
if ($options->{target} eq '-' and $format ne 'tar' and $format ne 'null') {
error "the $format format is unable to write to standard output";
if ( $options->{target} eq '-'
and $options->{format} ne 'tar'
and $options->{format} ne 'null') {
error "the $options->{format} format is unable to write to stdout";
}
if ($format eq 'null'
if ($options->{format} eq 'null'
and none { $_ eq $options->{target} } ('-', '/dev/null')) {
info "ignoring target $options->{target} with null format";
}
if ($format eq 'ext2') {
if ($options->{format} eq 'ext2') {
if (!can_execute 'genext2fs') {
error "need genext2fs for ext2 format";
}
} elsif ($format eq 'squashfs') {
} elsif ($options->{format} eq 'squashfs') {
if (!can_execute 'tar2sqfs') {
error "need tar2sqfs binary from the squashfs-tools-ng package";
}
}
if (any { $_ eq $format } ('tar', 'squashfs', 'ext2', 'null')) {
if ($format ne 'null') {
if (any { $_ eq $options->{format} } ('tar', 'squashfs', 'ext2', 'null')) {
if ($options->{format} ne 'null') {
if (any { $_ eq $options->{variant} } ('extract', 'custom')
and $options->{mode} eq 'fakechroot') {
info "creating a tarball or squashfs image or ext2 image in"
@ -5630,7 +5678,7 @@ sub main() {
) {
chmod 0755, $options->{root} or error "cannot chmod root: $!";
}
} elsif ($format eq 'directory') {
} elsif ($options->{format} eq 'directory') {
# user does not seem to have specified a tarball as output, thus work
# directly in the supplied directory
$options->{root} = $options->{target};
@ -5686,7 +5734,7 @@ sub main() {
}
}
} else {
error "unknown format: $format";
error "unknown format: $options->{format}";
}
# check for double quotes because apt doesn't allow to escape them and
@ -5770,15 +5818,28 @@ sub main() {
error "unknown mode: $options->{mode}";
}
# If a tarball is to be created, we always (except if --skip=output/dev is
# passed) craft the /dev entries ourselves.
# Why do we put /dev entries in the final tarball?
# - because debootstrap does it
# - because schroot (#856877) and pbuilder rely on it and we care about
# Debian buildds (using schroot) and reproducible builds infra (using
# pbuilder)
# If both the above assertion change, we can stop creating /dev entries as
# well.
my $devtar = '';
# We always craft the /dev entries ourselves if a tarball is to be created
if (any { $_ eq $format } ('tar', 'squashfs', 'ext2')) {
if (any { $_ eq $options->{format} } ('tar', 'squashfs', 'ext2')) {
foreach my $file (@devfiles) {
my ($fname, $mode, $type, $linkname, $devmajor, $devminor)
= @{$file};
if (length "./dev/$fname" > 100) {
error "tar entry cannot exceed 100 characters";
}
if ($type == 3
and any { $_ eq 'output/mknod' } @{ $options->{skip} }) {
info "skipping output/mknod as requested for ./dev/$fname";
next;
}
my $entry = pack(
'a100 a8 a8 a8 a12 a12 A8 a1 a100 a8 a32 a32 a8 a8 a155 x12',
"./dev/$fname",
@ -5802,10 +5863,10 @@ sub main() {
= sprintf("%06o\0", unpack("%16C*", $entry));
$devtar .= $entry;
}
} elsif (any { $_ eq $format } ('directory', 'null')) {
} elsif (any { $_ eq $options->{format} } ('directory', 'null')) {
# nothing to do
} else {
error "unknown format: $format";
error "unknown format: $options->{format}";
}
my $exitstatus = 0;
@ -5818,11 +5879,14 @@ sub main() {
'--format=pax',
'--pax-option=exthdr.name=%d/PaxHeaders/%f,delete=atime,delete=ctime',
'-c',
'--exclude=./dev',
'--exclude=./lost+found'
);
# only exclude ./dev if device nodes are written out (the default)
if (none { $_ eq 'output/dev' } @{ $options->{skip} }) {
push @taropts, '--exclude=./dev';
}
# tar2sqfs and genext2fs do not support extended attributes
if ($format eq "squashfs") {
if ($options->{format} eq "squashfs") {
# tar2sqfs supports user.*, trusted.* and security.* but not system.*
# https://bugs.debian.org/988100
# lib/sqfs/xattr/xattr.c of https://github.com/AgentD/squashfs-tools-ng
@ -5831,7 +5895,7 @@ sub main() {
warning("tar2sqfs does not support extended attributes"
. " from the 'system' namespace");
push @taropts, '--xattrs', '--xattrs-exclude=system.*';
} elsif ($format eq "ext2") {
} elsif ($options->{format} eq "ext2") {
warning "genext2fs does not support extended attributes";
} else {
push @taropts, '--xattrs';
@ -5883,7 +5947,7 @@ sub main() {
close $childsock;
close $nblkreader;
if (!$options->{dryrun} && $format eq 'ext2') {
if (!$options->{dryrun} && $options->{format} eq 'ext2') {
my $numblocks = approx_disk_usage($options->{root});
print $nblkwriter "$numblocks\n";
$nblkwriter->flush();
@ -5892,7 +5956,8 @@ sub main() {
if ($options->{dryrun}) {
info "simulate creating tarball...";
} elsif (any { $_ eq $format } ('tar', 'squashfs', 'ext2')) {
} elsif (any { $_ eq $options->{format} }
('tar', 'squashfs', 'ext2')) {
info "creating tarball...";
# redirect tar output to the writing end of the pipe so
@ -5913,10 +5978,11 @@ sub main() {
or error "tar failed: $?";
info "done";
} elsif (any { $_ eq $format } ('directory', 'null')) {
} elsif (any { $_ eq $options->{format} }
('directory', 'null')) {
# nothing to do
} else {
error "unknown format: $format";
error "unknown format: $options->{format}";
}
exit 0;
@ -5948,7 +6014,7 @@ sub main() {
close $childsock;
close $nblkreader;
if (!$options->{dryrun} && $format eq 'ext2') {
if (!$options->{dryrun} && $options->{format} eq 'ext2') {
my $numblocks = approx_disk_usage($options->{root});
print $nblkwriter $numblocks;
$nblkwriter->flush();
@ -5957,7 +6023,8 @@ sub main() {
if ($options->{dryrun}) {
info "simulate creating tarball...";
} elsif (any { $_ eq $format } ('tar', 'squashfs', 'ext2')) {
} elsif (any { $_ eq $options->{format} }
('tar', 'squashfs', 'ext2')) {
info "creating tarball...";
# redirect tar output to the writing end of the pipe so that
@ -6005,10 +6072,10 @@ sub main() {
}
info "done";
} elsif (any { $_ eq $format } ('directory', 'null')) {
} elsif (any { $_ eq $options->{format} } ('directory', 'null')) {
# nothing to do
} else {
error "unknown format: $format";
error "unknown format: $options->{format}";
}
exit 0;
@ -6066,7 +6133,7 @@ sub main() {
my $numblocks = 0;
close $nblkwriter;
if (!$options->{dryrun} && $format eq 'ext2') {
if (!$options->{dryrun} && $options->{format} eq 'ext2') {
$numblocks = <$nblkreader>;
if (defined $numblocks) {
chomp $numblocks;
@ -6083,9 +6150,9 @@ sub main() {
if ($options->{dryrun}) {
# nothing to do
} elsif (any { $_ eq $format } ('directory', 'null')) {
} elsif (any { $_ eq $options->{format} } ('directory', 'null')) {
# nothing to do
} elsif (any { $_ eq $format } ('tar', 'squashfs', 'ext2')) {
} elsif (any { $_ eq $options->{format} } ('tar', 'squashfs', 'ext2')) {
# we use eval() so that error() doesn't take this process down and
# thus leaves the setup() process without a parent
eval {
@ -6094,27 +6161,27 @@ sub main() {
error "cannot copy to standard output: $!";
}
} else {
if ( $format eq 'squashfs'
or $format eq 'ext2'
if ( $options->{format} eq 'squashfs'
or $options->{format} eq 'ext2'
or defined $tar_compressor) {
my @argv = ();
if ($format eq 'squashfs') {
if ($options->{format} eq 'squashfs') {
push @argv, 'tar2sqfs',
'--quiet', '--no-skip', '--force',
'--exportable',
'--compressor', 'xz',
'--block-size', '1048576',
$options->{target};
} elsif ($format eq 'ext2') {
} elsif ($options->{format} eq 'ext2') {
if ($numblocks <= 0) {
error "invalid number of blocks: $numblocks";
}
push @argv, 'genext2fs', '-B', 1024, '-b', $numblocks,
'-i', '16384', '-a', '-', $options->{target};
} elsif ($format eq 'tar') {
} elsif ($options->{format} eq 'tar') {
push @argv, @{$tar_compressor};
} else {
error "unknown format: $format";
error "unknown format: $options->{format}";
}
POSIX::sigprocmask(SIG_BLOCK, $sigset)
or error "Can't block signals: $!";
@ -6132,15 +6199,16 @@ sub main() {
or error "Can't unblock signals: $!";
# redirect stdout to file or /dev/null
if ($format eq 'squashfs' or $format eq 'ext2') {
if ( $options->{format} eq 'squashfs'
or $options->{format} eq 'ext2') {
open(STDOUT, '>', '/dev/null')
or error "cannot open /dev/null for writing: $!";
} elsif ($format eq 'tar') {
} elsif ($options->{format} eq 'tar') {
open(STDOUT, '>', $options->{target})
or error
"cannot open $options->{target} for writing: $!";
} else {
error "unknown format: $format";
error "unknown format: $options->{format}";
}
open(STDIN, '<&', $rfh)
or error "cannot open file handle for reading: $!";
@ -6177,7 +6245,7 @@ sub main() {
$exitstatus = 1;
}
} else {
error "unknown format: $format";
error "unknown format: $options->{format}";
}
close($rfh);
waitpid $pid, 0;
@ -6188,9 +6256,10 @@ sub main() {
# change signal handler message
$waiting_for = "cleanup";
if (any { $_ eq $format } ('directory')) {
if (any { $_ eq $options->{format} } ('directory')) {
# nothing to do
} elsif (any { $_ eq $format } ('tar', 'squashfs', 'ext2', 'null')) {
} elsif (any { $_ eq $options->{format} }
('tar', 'squashfs', 'ext2', 'null')) {
if (!-e $options->{root}) {
error "$options->{root} does not exist";
}
@ -6238,7 +6307,7 @@ sub main() {
error "unknown mode: $options->{mode}";
}
} else {
error "unknown format: $format";
error "unknown format: $options->{format}";
}
if ($got_signal) {
@ -7252,10 +7321,21 @@ Performs cleanup tasks, unless B<--skip=cleanup> is used:
=back
=item B<output>
For formats other than B<directory>, pack up the temporary chroot directory
into a tarball, ext2 image or squashfs image and delete the temporary chroot
directory.
If B<--skip=output/dev> is added, the resulting chroot will not contain the
device nodes, directories and symlinks that B<debootstrap> creates but just
an empty /dev as created by B<base-files>.
If B<--skip=output/mknod> is added, the resulting chroot will not contain
device nodes (neither block nor character special devices). This is useful
if the chroot tarball is to be exatracted in environments where mknod does
not function like in unshared user namespaces.
=back
=head1 EXAMPLES
@ -7470,7 +7550,7 @@ Create a system that can be used with podman:
As a docker/podman replacement:
$ mmdebstrap unstable | mmtarfilter --path-exclude='/dev/*' > chroot.tar
$ mmdebstrap --skip=output/mknod unstable chroot.tar
[...]
$ mmdebstrap --variant=custom --skip=update \
--setup-hook='tar-in chroot.tar /' \

35
tests/skip-output-dev Normal file
View file

@ -0,0 +1,35 @@
#!/bin/sh
set -eu
export LC_ALL=C.UTF-8
prefix=
if [ "$(id -u)" -eq 0 ] && [ "{{ MODE }}" != "root" ] && [ "{{ MODE }}" != "auto" ]; then
if ! id "${SUDO_USER:-user}" >/dev/null 2>&1; then
if [ ! -e /mmdebstrap-testenv ]; then
echo "this test modifies the system and should only be run inside a container" >&2
exit 1
fi
useradd --home-dir "/home/${SUDO_USER:-user}" --create-home "${SUDO_USER:-user}"
fi
prefix="runuser -u ${SUDO_USER:-user} --"
fi
# test this for both unshare and root mode because the code paths creating
# entries in /dev are different depending on whether mknod is available or not
$prefix {{ CMD }} --mode={{ MODE }} --variant=apt --skip=output/dev {{ DIST }} - {{ MIRROR }} | {
tar -t;
echo ./dev/console;
echo ./dev/fd;
echo ./dev/full;
echo ./dev/null;
echo ./dev/ptmx;
echo ./dev/pts/;
echo ./dev/random;
echo ./dev/shm/;
echo ./dev/stderr;
echo ./dev/stdin;
echo ./dev/stdout;
echo ./dev/tty;
echo ./dev/urandom;
echo ./dev/zero;
} | sort | diff -u tar1.txt -

30
tests/skip-output-mknod Normal file
View file

@ -0,0 +1,30 @@
#!/bin/sh
set -eu
export LC_ALL=C.UTF-8
prefix=
if [ "$(id -u)" -eq 0 ] && [ "{{ MODE }}" != "root" ] && [ "{{ MODE }}" != "auto" ]; then
if ! id "${SUDO_USER:-user}" >/dev/null 2>&1; then
if [ ! -e /mmdebstrap-testenv ]; then
echo "this test modifies the system and should only be run inside a container" >&2
exit 1
fi
useradd --home-dir "/home/${SUDO_USER:-user}" --create-home "${SUDO_USER:-user}"
fi
prefix="runuser -u ${SUDO_USER:-user} --"
fi
# test this for both unshare and root mode because the code paths creating
# entries in /dev are different depending on whether mknod is available or not
$prefix {{ CMD }} --mode={{ MODE }} --variant=apt --skip=output/mknod \
{{ DIST }} - {{ MIRROR }} | {
tar -t;
echo ./dev/console;
echo ./dev/full;
echo ./dev/null;
echo ./dev/ptmx;
echo ./dev/random;
echo ./dev/tty;
echo ./dev/urandom;
echo ./dev/zero;
} | sort | diff -u tar1.txt -