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Diffstat (limited to 'scripts/dpkg-fsys-usrunmess.pl')
| -rwxr-xr-x | scripts/dpkg-fsys-usrunmess.pl | 631 |
1 files changed, 631 insertions, 0 deletions
diff --git a/scripts/dpkg-fsys-usrunmess.pl b/scripts/dpkg-fsys-usrunmess.pl new file mode 100755 index 0000000..25dc259 --- /dev/null +++ b/scripts/dpkg-fsys-usrunmess.pl @@ -0,0 +1,631 @@ +#!/usr/bin/perl +# +# dpkg-fsys-usrunmess - Undoes the merged-/usr-via-aliased-dirs mess +# +# Copyright © 2020-2021 Guillem Jover <guillem@debian.org> +# +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 2 of the License, or +# (at your option) any later version. +# +# This program is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see <https://www.gnu.org/licenses/> + +use strict; +use warnings; +use feature qw(state); + +our ($PROGNAME) = $0 =~ m{(?:.*/)?([^/]*)}; +our $PROGVERSION = '1.22.x'; +our $ADMINDIR = '/var/lib/dpkg/'; + +use POSIX; +use File::Temp qw(tempdir); +use File::Find; +use Getopt::Long qw(:config posix_default bundling_values no_ignorecase); + +eval q{ + use File::FcntlLock; +}; +if ($@) { + fatal('missing File::FcntlLock module; please install libfile-fcntllock-perl'); +} + +my $opt_noact = length $ENV{DPKG_USRUNMESS_NOACT} ? 1 : 0; +my $opt_prompt = 0; +my $opt_prevent = -1; + +my @options_spec = ( + 'help|?' => sub { usage(); exit 0; }, + 'version' => sub { version(); exit 0; }, + 'dry-run|no-act|n' => \$opt_noact, + 'prompt|p' => \$opt_prompt, + 'prevention!' => \$opt_prevent, +); + +{ + local $SIG{__WARN__} = sub { usageerr($_[0]) }; + GetOptions(@options_spec); +} + +# Set a known umask. +umask 0022; + +my @aliased_dirs; + +# +# Scan all dirs under / and check whether any are aliased to /usr. +# + +foreach my $path (glob '/*') { + debug("checking symlink? $path"); + next unless -l $path; + debug("checking merged-usr symlink? $path"); + my $symlink = readlink $path; + next unless $symlink eq "usr$path" or $symlink eq "/usr$path"; + debug("merged-usr breakage, queueing $path"); + push @aliased_dirs, $path; +} + +if (@aliased_dirs == 0) { + print "System is fine, no aliased directories found, congrats!\n"; + exit 0; +} + +# +# dpkg consistency checks +# + +debug('checking dpkg database consistency'); +system(qw(dpkg --audit)) == 0 + or fatal("cannot audit the dpkg database: $!"); + +debug('checking whether dpkg has been interrupted'); +if (glob "$ADMINDIR/updates/*") { + fatal('dpkg is in an inconsistent state, please fix that'); +} + +$opt_prevent = prompt('Generate and install a regression prevention package') + if $opt_prevent < 0; + +if ($opt_prevent) { + debug('building regression prevention measures'); + my $tmpdir = tempdir(CLEANUP => 1, TMPDIR => 1); + my $pkgdir = "$tmpdir/pkg"; + my $pkgfile = "$tmpdir/dpkg-fsys-usrunmess.deb"; + + mkdir "$pkgdir" or fatal('cannot create temporary package directory'); + mkdir "$pkgdir/DEBIAN" or fatal('cannot create temporary directory'); + open my $ctrl_fh, '>', "$pkgdir/DEBIAN/control" + or fatal('cannot create temporary control file'); + print { $ctrl_fh } <<"CTRL"; +Package: dpkg-fsys-usrunmess +Version: $PROGVERSION +Architecture: all +Protected: yes +Multi-Arch: foreign +Section: admin +Priority: optional +Maintainer: Dpkg Developers <debian-dpkg\@lists.debian.org> +Installed-Size: 5 +Conflicts: usrmerge +Provides: usrmerge (= 25) +Replaces: usrmerge +Description: prevention measure to avoid unsuspected filesystem breakage + This package will prevent automatic migration of the filesystem to the + broken merge-/usr-via-aliased-dirs via the usrmerge package. + . + This package was generated and installed by the dpkg-fsys-usrunmess(8) + program. + +CTRL + close $ctrl_fh or fatal('cannot write temporary control file'); + + system(('dpkg-deb', '-b', $pkgdir, $pkgfile)) == 0 + or fatal('cannot create prevention package'); + + if (not $opt_noact) { + system(('dpkg', '-GBi', $pkgfile)) == 0 + or fatal('cannot install prevention package'); + } +} else { + print "Will not generate and install a regression prevention package.\n"; +} + +my $aliased_regex = '^(' . join('|', @aliased_dirs) . ')/'; + +# +# Get a list of all paths (including diversion) under the aliased dirs. +# + +my @search_args; +my %aliased_pathnames; +foreach my $dir (@aliased_dirs) { + push @search_args, "$dir/*"; +} + +# We also need to track /usr/lib/modules to then be able to compute its +# complement when looking for untracked kernel module files under aliased +# dirs. +my %usr_mod_pathnames; +push @search_args, '/usr/lib/modules/*'; + +open my $fh_paths, '-|', 'dpkg-query', '--search', @search_args + or fatal("cannot execute dpkg-query --search: $!"); +while (<$fh_paths>) { + if (m/^diversion by [^ ]+ from: .*$/) { + # Ignore. + } elsif (m/^diversion by [^ ]+ to: (.*)$/) { + if (-e $1) { + add_pathname($1, 'diverted pathname'); + } + } elsif (m/^.*: (.*)$/) { + add_pathname($1, 'pathname'); + } +} +close $fh_paths; + +# +# Get a list of all update-alternatives under the aliased dirs. +# + +my @selections = qx(update-alternatives --get-selections); +foreach my $selection (@selections) { + my $name = (split(' ', $selection))[0]; + my $slaves = 0; + + open my $fh_alts, '-|', 'update-alternatives', '--query', $name + or fatal("cannot execute update-alternatives --query: $!"); + while (<$fh_alts>) { + if (m/^\s*$/) { + last; + } elsif (m/^Link: (.*)$/) { + add_pathname($1, 'alternative link'); + } elsif (m/^Slaves:\s*$/) { + $slaves = 1; + } elsif ($slaves and m/^\s\S+\s(\S+)$/) { + add_pathname($1, 'alternative slave'); + } else { + $slaves = 0; + } + } + close $fh_alts; +} + +# +# Unfortunately we need to special case untracked kernel module files, +# as these are required for system booting. To reduce potentially moving +# undesired non-kernel module files (such as apache, python or ruby ones), +# we only look for sub-dirs starting with a digit, which should match for +# both Linux and kFreeBSD modules, and also for the modprobe.conf filename. +# + +find({ + no_chdir => 1, + wanted => sub { + my $path = $_; + + if (exists $aliased_pathnames{$path}) { + # Ignore pathname already handled. + } elsif (exists $usr_mod_pathnames{"/usr$path"}) { + # Ignore pathname owned elsewhere. + } elsif ($path eq '/lib/modules' or + $path eq '/lib/modules/modprobe.conf' or + $path =~ m{^/lib/modules/[0-9]}) { + add_pathname($path, 'untracked modules'); + } + }, +}, '/lib/modules'); + + +my $sroot = '/.usrunmess'; +my @relabel; + +# +# Create a shadow hierarchy under / for the new unmessed dir: +# + +debug("creating shadow dir = $sroot"); +mkdir $sroot + or sysfatal("cannot create directory $sroot"); +foreach my $dir (@aliased_dirs) { + debug("creating shadow dir = $sroot$dir"); + mkdir "$sroot$dir" + or sysfatal("cannot create directory $sroot$dir"); + chmod 0755, "$sroot$dir" + or sysfatal("cannot chmod 0755 $sroot$dir"); + chown 0, 0, "$sroot$dir" + or sysfatal("cannot chown 0 0 $sroot$dir"); + push @relabel, "$sroot$dir"; +} + +# +# Populate the split dirs with hardlinks or copies of the objects from +# their counter-parts in /usr. +# + +foreach my $pathname (sort keys %aliased_pathnames) { + my (@meta) = lstat $pathname + or sysfatal("cannot lstat object $pathname for shadow hierarchy"); + + if (-d _) { + my $mode = $meta[2]; + my ($uid, $gid) = @meta[4, 5]; + my ($atime, $mtime, $ctime) = @meta[8, 9, 10]; + + debug("creating shadow dir = $sroot$pathname"); + mkdir "$sroot$pathname" + or sysfatal("cannot mkdir $sroot$pathname"); + chmod $mode, "$sroot$pathname" + or sysfatal("cannot chmod $mode $sroot$pathname"); + chown $uid, $gid, "$sroot$pathname" + or sysfatal("cannot chown $uid $gid $sroot$pathname"); + utime $atime, $mtime, "$sroot$pathname" + or sysfatal("cannot utime $atime $mtime $sroot$pathname"); + push @relabel, "$sroot$pathname"; + } elsif (-f _) { + debug("creating shadow file = $sroot$pathname"); + copy("/usr$pathname", "$sroot$pathname"); + } elsif (-l _) { + my $target = readlink "/usr$pathname"; + + debug("creating shadow symlink = $sroot$pathname"); + symlink $target, "$sroot$pathname" + or sysfatal("cannot symlink $target to $sroot$pathname"); + push @relabel, "$sroot$pathname"; + } else { + fatal("unhandled object type for '$pathname'"); + } +} + +# +# Prompt at the point of no return, if the user requested it. +# + +if ($opt_prompt) { + if (!prompt("Shadow hierarchy created at '$sroot', ready to proceed")) { + print "Aborting migration, shadow hierarchy left in place.\n"; + exit 0; + } +} + +# +# Mark all packages as half-configured so that we can force a mass +# reconfiguration, to trigger any code in maintainer scripts that might +# create files. +# +# XXX: We do this manually by editing the status file. +# XXX: We do this for packages that might not have maintscripts, or might +# not involve affected directories. +# + +debug('marking all dpkg packages as half-configured'); +if (not $opt_noact) { + open my $fh_lock, '>', "$ADMINDIR/lock" + or sysfatal('cannot open dpkg database lock file'); + my $fs = File::FcntlLock->new(l_type => F_WRLCK); + $fs->lock($fh_lock, F_SETLKW) + or sysfatal('cannot get a write lock on dpkg database'); + + my $file_db = "$ADMINDIR/status"; + my $file_dbnew = $file_db . '.new'; + + open my $fh_dbnew, '>', $file_dbnew + or sysfatal('cannot open new dpkg database'); + open my $fh_db, '<', $file_db + or sysfatal('cannot open dpkg database'); + while (<$fh_db>) { + if (m/^Status: /) { + s/ installed$/ half-configured/; + } + print { $fh_dbnew } $_; + } + close $fh_db; + $fh_dbnew->flush() or sysfatal('cannot flush new dpkg database'); + $fh_dbnew->sync() or sysfatal('cannot fsync new dpkg database'); + close $fh_dbnew or sysfatal('cannot close new dpkg database'); + + rename $file_dbnew, $file_db + or sysfatal('cannot rename new dpkg database'); +} + +# +# Replace things as quickly as possible: +# + +foreach my $dir (@aliased_dirs) { + debug("making dir backup = $dir.aliased"); + if (not $opt_noact) { + rename $dir, "$dir.aliased" + or sysfatal("cannot make backup directory $dir.aliased"); + } + + debug("renaming $sroot$dir to $dir"); + if (not $opt_noact) { + rename "$sroot$dir", $dir + or sysfatal("cannot install fixed directory $dir"); + } +} + +mac_relabel(); + +# +# Cleanup backup directories. +# + +foreach my $dir (@aliased_dirs) { + debug("removing backup = $dir.aliased"); + if (not $opt_noact) { + unlink "$dir.aliased" + or sysfatal("cannot cleanup backup directory $dir.aliased"); + } +} + +my %deferred_dirnames; + +# +# Cleanup moved objects. +# + +foreach my $pathname (sort keys %aliased_pathnames) { + my (@meta) = lstat $pathname + or sysfatal("cannot lstat object $pathname for cleanup"); + + if (-d _) { + # Skip directories as this might be shared by a proper path under the + # aliased hierearchy. And so that we can remove them in reverse order. + debug("deferring merged dir cleanup = /usr$pathname"); + $deferred_dirnames{"/usr$pathname"} = 1; + } else { + debug("cleaning up pathname = /usr$pathname"); + next if $opt_noact; + unlink "/usr$pathname" + or sysfatal("cannot unlink object /usr$pathname"); + } +} + +# +# Cleanup deferred directories. +# + +debug("cleaning up shadow deferred dir = $sroot"); +my $arg_max = POSIX::sysconf(POSIX::_SC_ARG_MAX) // POSIX::_POSIX_ARG_MAX; +my @batch_dirs; +my $batch_size = 0; + +foreach my $dir (keys %deferred_dirnames) { + my $dir_size = length($dir) + 1; + if ($batch_size + $dir_size < $arg_max) { + $batch_size += length($dir) + 1; + push @batch_dirs, $dir; + + } else { + next; + } + next if length $batch_size == 0; + + open my $fh_dirs, '-|', 'dpkg-query', '--search', @batch_dirs + or fatal("cannot execute dpkg-query --search: $!"); + while (<$fh_dirs>) { + if (m/^.*: (.*)$/) { + # If the directory is known by its aliased name, it should not be + # cleaned up. + if (exists $deferred_dirnames{$1}) { + delete $deferred_dirnames{$1}; + } + } + } + close $fh_dirs; + + @batch_dirs = (); + $batch_size = 0; +} + +my @dirs_linger; + +if (not $opt_noact) { + foreach my $dirname (reverse sort keys %deferred_dirnames) { + next if rmdir $dirname; + warning("cannot remove shadow directory $dirname: $!"); + + push @dirs_linger, $dirname; + } +} + +if (not $opt_noact) { + debug("cleaning up shadow root dir = $sroot"); + rmdir $sroot + or warning("cannot remove shadow directory $sroot: $!"); +} + +# +# Re-configure all packages, so that postinst maintscripts are executed. +# + +my $policypath = '/usr/sbin/dpkg-fsys-usrunmess-policy-rc.d'; + +debug('installing local policy-rc.d'); +if (not $opt_noact) { + open my $policyfh, '>', $policypath + or sysfatal("cannot create $policypath"); + print { $policyfh } <<'POLICYRC'; +#!/bin/sh +echo "$0: Denied action $2 for service $1" +exit 101 +POLICYRC + close $policyfh or fatal("cannot write $policypath"); + + my @alt = (qw(/usr/sbin/policy-rc.d policy-rc.d), $policypath, qw(1000)); + system(qw(update-alternatives --install), @alt) == 0 + or fatal("cannot register $policypath"); + + system(qw(update-alternatives --set policy-rc.d), $policypath) == 0 + or fatal("cannot select alternative $policypath"); +} + +debug('reconfiguring all packages'); +if (not $opt_noact) { + local $ENV{DEBIAN_FRONTEND} = 'noninteractive'; + system(qw(dpkg --configure --pending)) == 0 + or fatal("cannot reconfigure packages: $!"); +} + +debug('removing local policy-rc.d'); +if (not $opt_noact) { + system(qw(update-alternatives --remove policy-rc.d), $policypath) == 0 + or fatal("cannot unregister $policypath: $!"); + + unlink $policypath + or warning("cannot remove $policypath"); + + # Restore the selections we saved initially. + open my $altfh, '|-', qw(update-alternatives --set-selections) + or fatal('cannot restore alternatives state'); + print { $altfh } $_ foreach @selections; + close $altfh or fatal('cannot restore alternatives state'); +} + +print "\n"; + +if (@dirs_linger) { + warning('lingering directories that could not be removed:'); + foreach my $dir (@dirs_linger) { + warning(" $dir"); + } +} + +print "Done, hierarchy unmessed, congrats!\n"; +print "Rebooting now is very strongly advised.\n"; + +print "(Note: you might need to run 'hash -r' in your shell.)\n"; + +## +## Functions +## + +sub debug +{ + my $msg = shift; + + print { *STDERR } "D: $msg\n"; +} + +sub warning +{ + my $msg = shift; + + warn "warning: $msg\n"; +} + +sub fatal +{ + my $msg = shift; + + die "error: $msg\n"; +} + +sub sysfatal +{ + my $msg = shift; + + fatal("$msg: $!"); +} + +sub copy +{ + my ($src, $dst) = @_; + + # Try to hardlink first. + return if link $src, $dst; + + # If we are on different filesystems, try a copy. + if ($! == POSIX::EXDEV) { + # XXX: This will not preserve hardlinks, these would get restored + # after the next package upgrade. + system('cp', '-a', $src, $dst) == 0 + or fatal("cannot copy file $src to $dst: $?"); + } else { + sysfatal("cannot link file $src to $dst"); + } +} + +sub mac_relabel +{ + my $has_cmd = 0; + foreach my $path (split /:/, $ENV{PATH}) { + if (-x "$path/restorecon") { + $has_cmd = 1; + last; + } + } + return unless $has_cmd; + + foreach my $pathname (@relabel) { + system('restorecon', $pathname) == 0 + or fatal("cannot restore MAC context for $pathname: $?"); + } +} + +sub add_pathname +{ + my ($pathname, $origin) = @_; + + if ($pathname =~ m{^/usr/lib/modules/}) { + debug("tracking $origin = $pathname"); + $usr_mod_pathnames{$pathname} = 1; + } elsif ($pathname =~ m/$aliased_regex/) { + debug("adding $origin = $pathname"); + $aliased_pathnames{$pathname} = 1; + } +} + +sub prompt +{ + my $query = shift; + + print "$query (y/N)? "; + my $reply = <STDIN>; + chomp $reply; + + return 0 if $reply ne 'y' and $reply ne 'yes'; + return 1; +} + +sub version() +{ + printf "Debian %s version %s.\n", $PROGNAME, $PROGVERSION; +} + +sub usage +{ + printf +'Usage: %s [<option>...]' + . "\n\n" . +'Options: + -p, --prompt prompt before the point of no return. + --prevention enable regression prevention package installation. + --no-prevention disable regression prevention package installation. + -n, --no-act just check and create the new structure, no switch. + --dry-run ditto. + -?, --help show this help message. + --version show the version.' + . "\n", $PROGNAME; +} + +sub usageerr +{ + my ($msg, @args) = @_; + + state $printforhelp = 'Use --help for program usage information.'; + + $msg = sprintf $msg, @args if @args; + warn "$PROGNAME: error: $msg\n"; + warn "$printforhelp\n"; + exit 2; +} |