23d920c8f0
This enlarges the system uid/gid range 6-fold, from 100 to 600 ids. This is a preventative measure against running out of dynamically allocated ids for NixOS services with isSystemUser, which should become the preferred way of allocating uids for non-real users.
283 lines
9.2 KiB
Perl
283 lines
9.2 KiB
Perl
use strict;
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use File::Path qw(make_path);
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use File::Slurp;
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use JSON;
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make_path("/var/lib/nixos", { mode => 0755 });
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# Keep track of deleted uids and gids.
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my $uidMapFile = "/var/lib/nixos/uid-map";
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my $uidMap = -e $uidMapFile ? decode_json(read_file($uidMapFile)) : {};
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my $gidMapFile = "/var/lib/nixos/gid-map";
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my $gidMap = -e $gidMapFile ? decode_json(read_file($gidMapFile)) : {};
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sub updateFile {
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my ($path, $contents, $perms) = @_;
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write_file("$path.tmp", { binmode => ':utf8', perms => $perms // 0644 }, $contents);
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rename("$path.tmp", $path) or die;
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}
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sub hashPassword {
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my ($password) = @_;
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my $salt = "";
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my @chars = ('.', '/', 0..9, 'A'..'Z', 'a'..'z');
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$salt .= $chars[rand 64] for (1..8);
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return crypt($password, '$6$' . $salt . '$');
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}
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# Functions for allocating free GIDs/UIDs. FIXME: respect ID ranges in
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# /etc/login.defs.
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sub allocId {
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my ($used, $prevUsed, $idMin, $idMax, $up, $getid) = @_;
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my $id = $up ? $idMin : $idMax;
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while ($id >= $idMin && $id <= $idMax) {
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if (!$used->{$id} && !$prevUsed->{$id} && !defined &$getid($id)) {
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$used->{$id} = 1;
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return $id;
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}
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$used->{$id} = 1;
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if ($up) { $id++; } else { $id--; }
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}
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die "$0: out of free UIDs or GIDs\n";
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}
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my (%gidsUsed, %uidsUsed, %gidsPrevUsed, %uidsPrevUsed);
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sub allocGid {
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my ($name) = @_;
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my $prevGid = $gidMap->{$name};
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if (defined $prevGid && !defined $gidsUsed{$prevGid}) {
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print STDERR "reviving group '$name' with GID $prevGid\n";
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$gidsUsed{$prevGid} = 1;
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return $prevGid;
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}
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return allocId(\%gidsUsed, \%gidsPrevUsed, 400, 999, 0, sub { my ($gid) = @_; getgrgid($gid) });
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}
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sub allocUid {
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my ($name, $isSystemUser) = @_;
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my ($min, $max, $up) = $isSystemUser ? (400, 999, 0) : (1000, 29999, 1);
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my $prevUid = $uidMap->{$name};
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if (defined $prevUid && $prevUid >= $min && $prevUid <= $max && !defined $uidsUsed{$prevUid}) {
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print STDERR "reviving user '$name' with UID $prevUid\n";
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$uidsUsed{$prevUid} = 1;
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return $prevUid;
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}
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return allocId(\%uidsUsed, \%uidsPrevUsed, $min, $max, $up, sub { my ($uid) = @_; getpwuid($uid) });
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}
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# Read the declared users/groups.
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my $spec = decode_json(read_file($ARGV[0]));
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# Don't allocate UIDs/GIDs that are manually assigned.
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foreach my $g (@{$spec->{groups}}) {
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$gidsUsed{$g->{gid}} = 1 if defined $g->{gid};
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}
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foreach my $u (@{$spec->{users}}) {
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$uidsUsed{$u->{uid}} = 1 if defined $u->{uid};
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}
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# Likewise for previously used but deleted UIDs/GIDs.
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$uidsPrevUsed{$_} = 1 foreach values %{$uidMap};
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$gidsPrevUsed{$_} = 1 foreach values %{$gidMap};
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# Read the current /etc/group.
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sub parseGroup {
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chomp;
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my @f = split(':', $_, -4);
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my $gid = $f[2] eq "" ? undef : int($f[2]);
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$gidsUsed{$gid} = 1 if defined $gid;
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return ($f[0], { name => $f[0], password => $f[1], gid => $gid, members => $f[3] });
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}
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my %groupsCur = -f "/etc/group" ? map { parseGroup } read_file("/etc/group") : ();
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# Read the current /etc/passwd.
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sub parseUser {
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chomp;
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my @f = split(':', $_, -7);
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my $uid = $f[2] eq "" ? undef : int($f[2]);
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$uidsUsed{$uid} = 1 if defined $uid;
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return ($f[0], { name => $f[0], fakePassword => $f[1], uid => $uid,
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gid => $f[3], description => $f[4], home => $f[5], shell => $f[6] });
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}
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my %usersCur = -f "/etc/passwd" ? map { parseUser } read_file("/etc/passwd") : ();
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# Read the groups that were created declaratively (i.e. not by groups)
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# in the past. These must be removed if they are no longer in the
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# current spec.
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my $declGroupsFile = "/var/lib/nixos/declarative-groups";
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my %declGroups;
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$declGroups{$_} = 1 foreach split / /, -e $declGroupsFile ? read_file($declGroupsFile) : "";
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# Idem for the users.
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my $declUsersFile = "/var/lib/nixos/declarative-users";
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my %declUsers;
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$declUsers{$_} = 1 foreach split / /, -e $declUsersFile ? read_file($declUsersFile) : "";
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# Generate a new /etc/group containing the declared groups.
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my %groupsOut;
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foreach my $g (@{$spec->{groups}}) {
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my $name = $g->{name};
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my $existing = $groupsCur{$name};
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my %members = map { ($_, 1) } @{$g->{members}};
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if (defined $existing) {
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$g->{gid} = $existing->{gid} if !defined $g->{gid};
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if ($g->{gid} != $existing->{gid}) {
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warn "warning: not applying GID change of group ‘$name’ ($existing->{gid} -> $g->{gid})\n";
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$g->{gid} = $existing->{gid};
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}
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$g->{password} = $existing->{password}; # do we want this?
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if ($spec->{mutableUsers}) {
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# Merge in non-declarative group members.
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foreach my $uname (split /,/, $existing->{members} // "") {
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$members{$uname} = 1 if !defined $declUsers{$uname};
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}
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}
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} else {
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$g->{gid} = allocGid($name) if !defined $g->{gid};
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$g->{password} = "x";
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}
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$g->{members} = join ",", sort(keys(%members));
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$groupsOut{$name} = $g;
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$gidMap->{$name} = $g->{gid};
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}
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# Update the persistent list of declarative groups.
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updateFile($declGroupsFile, join(" ", sort(keys %groupsOut)));
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# Merge in the existing /etc/group.
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foreach my $name (keys %groupsCur) {
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my $g = $groupsCur{$name};
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next if defined $groupsOut{$name};
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if (!$spec->{mutableUsers} || defined $declGroups{$name}) {
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print STDERR "removing group ‘$name’\n";
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} else {
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$groupsOut{$name} = $g;
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}
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}
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# Rewrite /etc/group. FIXME: acquire lock.
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my @lines = map { join(":", $_->{name}, $_->{password}, $_->{gid}, $_->{members}) . "\n" }
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(sort { $a->{gid} <=> $b->{gid} } values(%groupsOut));
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updateFile($gidMapFile, encode_json($gidMap));
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updateFile("/etc/group", \@lines);
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system("nscd --invalidate group");
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# Generate a new /etc/passwd containing the declared users.
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my %usersOut;
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foreach my $u (@{$spec->{users}}) {
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my $name = $u->{name};
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# Resolve the gid of the user.
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if ($u->{group} =~ /^[0-9]$/) {
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$u->{gid} = $u->{group};
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} elsif (defined $groupsOut{$u->{group}}) {
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$u->{gid} = $groupsOut{$u->{group}}->{gid} // die;
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} else {
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warn "warning: user ‘$name’ has unknown group ‘$u->{group}’\n";
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$u->{gid} = 65534;
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}
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my $existing = $usersCur{$name};
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if (defined $existing) {
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$u->{uid} = $existing->{uid} if !defined $u->{uid};
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if ($u->{uid} != $existing->{uid}) {
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warn "warning: not applying UID change of user ‘$name’ ($existing->{uid} -> $u->{uid})\n";
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$u->{uid} = $existing->{uid};
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}
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} else {
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$u->{uid} = allocUid($name, $u->{isSystemUser}) if !defined $u->{uid};
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if (defined $u->{initialPassword}) {
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$u->{hashedPassword} = hashPassword($u->{initialPassword});
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} elsif (defined $u->{initialHashedPassword}) {
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$u->{hashedPassword} = $u->{initialHashedPassword};
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}
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}
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# Create a home directory.
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if ($u->{createHome}) {
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make_path($u->{home}, { mode => 0700 }) if ! -e $u->{home};
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chown $u->{uid}, $u->{gid}, $u->{home};
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}
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if (defined $u->{passwordFile}) {
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if (-e $u->{passwordFile}) {
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$u->{hashedPassword} = read_file($u->{passwordFile});
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chomp $u->{hashedPassword};
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} else {
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warn "warning: password file ‘$u->{passwordFile}’ does not exist\n";
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}
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} elsif (defined $u->{password}) {
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$u->{hashedPassword} = hashPassword($u->{password});
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}
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$u->{fakePassword} = $existing->{fakePassword} // "x";
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$usersOut{$name} = $u;
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$uidMap->{$name} = $u->{uid};
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}
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# Update the persistent list of declarative users.
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updateFile($declUsersFile, join(" ", sort(keys %usersOut)));
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# Merge in the existing /etc/passwd.
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foreach my $name (keys %usersCur) {
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my $u = $usersCur{$name};
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next if defined $usersOut{$name};
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if (!$spec->{mutableUsers} || defined $declUsers{$name}) {
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print STDERR "removing user ‘$name’\n";
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} else {
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$usersOut{$name} = $u;
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}
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}
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# Rewrite /etc/passwd. FIXME: acquire lock.
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@lines = map { join(":", $_->{name}, $_->{fakePassword}, $_->{uid}, $_->{gid}, $_->{description}, $_->{home}, $_->{shell}) . "\n" }
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(sort { $a->{uid} <=> $b->{uid} } (values %usersOut));
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updateFile($uidMapFile, encode_json($uidMap));
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updateFile("/etc/passwd", \@lines);
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system("nscd --invalidate passwd");
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# Rewrite /etc/shadow to add new accounts or remove dead ones.
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my @shadowNew;
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my %shadowSeen;
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foreach my $line (-f "/etc/shadow" ? read_file("/etc/shadow") : ()) {
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chomp $line;
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my ($name, $hashedPassword, @rest) = split(':', $line, -9);
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my $u = $usersOut{$name};;
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next if !defined $u;
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$hashedPassword = "!" if !$spec->{mutableUsers};
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$hashedPassword = $u->{hashedPassword} if defined $u->{hashedPassword} && !$spec->{mutableUsers}; # FIXME
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chomp $hashedPassword;
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push @shadowNew, join(":", $name, $hashedPassword, @rest) . "\n";
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$shadowSeen{$name} = 1;
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}
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foreach my $u (values %usersOut) {
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next if defined $shadowSeen{$u->{name}};
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my $hashedPassword = "!";
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$hashedPassword = $u->{hashedPassword} if defined $u->{hashedPassword};
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# FIXME: set correct value for sp_lstchg.
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push @shadowNew, join(":", $u->{name}, $hashedPassword, "1::::::") . "\n";
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}
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updateFile("/etc/shadow", \@shadowNew, 0600);
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