nixpkgs/nixos/modules/config/update-users-groups.pl
Nikolay Amiantov f2c5970a76 users-groups service: add autoSubUidGidRange option
Previously we allocated subuids automatically for all normal users.
Make this explicitly configurable, so that one can use this for system
users too (or explicitly disable for normal users). Also don't allocate
automatically by default if a user already has ranges specified statically.
2022-01-09 09:43:55 +03:00

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use strict;
use warnings;
use File::Path qw(make_path);
use File::Slurp;
use Getopt::Long;
use JSON;
# Keep track of deleted uids and gids.
my $uidMapFile = "/var/lib/nixos/uid-map";
my $uidMap = -e $uidMapFile ? decode_json(read_file($uidMapFile)) : {};
my $gidMapFile = "/var/lib/nixos/gid-map";
my $gidMap = -e $gidMapFile ? decode_json(read_file($gidMapFile)) : {};
my $is_dry = ($ENV{'NIXOS_ACTION'} // "") eq "dry-activate";
GetOptions("dry-activate" => \$is_dry);
make_path("/var/lib/nixos", { mode => 0755 }) unless $is_dry;
sub updateFile {
my ($path, $contents, $perms) = @_;
return if $is_dry;
write_file($path, { atomic => 1, binmode => ':utf8', perms => $perms // 0644 }, $contents) or die;
}
sub nscdInvalidate {
system("nscd", "--invalidate", $_[0]) unless $is_dry;
}
sub hashPassword {
my ($password) = @_;
my $salt = "";
my @chars = ('.', '/', 0..9, 'A'..'Z', 'a'..'z');
$salt .= $chars[rand 64] for (1..8);
return crypt($password, '$6$' . $salt . '$');
}
sub dry_print {
if ($is_dry) {
print STDERR ("$_[1] $_[2]\n")
} else {
print STDERR ("$_[0] $_[2]\n")
}
}
# Functions for allocating free GIDs/UIDs. FIXME: respect ID ranges in
# /etc/login.defs.
sub allocId {
my ($used, $prevUsed, $idMin, $idMax, $up, $getid) = @_;
my $id = $up ? $idMin : $idMax;
while ($id >= $idMin && $id <= $idMax) {
if (!$used->{$id} && !$prevUsed->{$id} && !defined &$getid($id)) {
$used->{$id} = 1;
return $id;
}
$used->{$id} = 1;
if ($up) { $id++; } else { $id--; }
}
die "$0: out of free UIDs or GIDs\n";
}
my (%gidsUsed, %uidsUsed, %gidsPrevUsed, %uidsPrevUsed);
sub allocGid {
my ($name) = @_;
my $prevGid = $gidMap->{$name};
if (defined $prevGid && !defined $gidsUsed{$prevGid}) {
dry_print("reviving", "would revive", "group '$name' with GID $prevGid");
$gidsUsed{$prevGid} = 1;
return $prevGid;
}
return allocId(\%gidsUsed, \%gidsPrevUsed, 400, 999, 0, sub { my ($gid) = @_; getgrgid($gid) });
}
sub allocUid {
my ($name, $isSystemUser) = @_;
my ($min, $max, $up) = $isSystemUser ? (400, 999, 0) : (1000, 29999, 1);
my $prevUid = $uidMap->{$name};
if (defined $prevUid && $prevUid >= $min && $prevUid <= $max && !defined $uidsUsed{$prevUid}) {
dry_print("reviving", "would revive", "user '$name' with UID $prevUid");
$uidsUsed{$prevUid} = 1;
return $prevUid;
}
return allocId(\%uidsUsed, \%uidsPrevUsed, $min, $max, $up, sub { my ($uid) = @_; getpwuid($uid) });
}
# Read the declared users/groups
my $spec = decode_json(read_file($ARGV[0]));
# Don't allocate UIDs/GIDs that are manually assigned.
foreach my $g (@{$spec->{groups}}) {
$gidsUsed{$g->{gid}} = 1 if defined $g->{gid};
}
foreach my $u (@{$spec->{users}}) {
$uidsUsed{$u->{uid}} = 1 if defined $u->{uid};
}
# Likewise for previously used but deleted UIDs/GIDs.
$uidsPrevUsed{$_} = 1 foreach values %{$uidMap};
$gidsPrevUsed{$_} = 1 foreach values %{$gidMap};
# Read the current /etc/group.
sub parseGroup {
chomp;
my @f = split(':', $_, -4);
my $gid = $f[2] eq "" ? undef : int($f[2]);
$gidsUsed{$gid} = 1 if defined $gid;
return ($f[0], { name => $f[0], password => $f[1], gid => $gid, members => $f[3] });
}
my %groupsCur = -f "/etc/group" ? map { parseGroup } read_file("/etc/group", { binmode => ":utf8" }) : ();
# Read the current /etc/passwd.
sub parseUser {
chomp;
my @f = split(':', $_, -7);
my $uid = $f[2] eq "" ? undef : int($f[2]);
$uidsUsed{$uid} = 1 if defined $uid;
return ($f[0], { name => $f[0], fakePassword => $f[1], uid => $uid,
gid => $f[3], description => $f[4], home => $f[5], shell => $f[6] });
}
my %usersCur = -f "/etc/passwd" ? map { parseUser } read_file("/etc/passwd", { binmode => ":utf8" }) : ();
# Read the groups that were created declaratively (i.e. not by groups)
# in the past. These must be removed if they are no longer in the
# current spec.
my $declGroupsFile = "/var/lib/nixos/declarative-groups";
my %declGroups;
$declGroups{$_} = 1 foreach split / /, -e $declGroupsFile ? read_file($declGroupsFile, { binmode => ":utf8" }) : "";
# Idem for the users.
my $declUsersFile = "/var/lib/nixos/declarative-users";
my %declUsers;
$declUsers{$_} = 1 foreach split / /, -e $declUsersFile ? read_file($declUsersFile, { binmode => ":utf8" }) : "";
# Generate a new /etc/group containing the declared groups.
my %groupsOut;
foreach my $g (@{$spec->{groups}}) {
my $name = $g->{name};
my $existing = $groupsCur{$name};
my %members = map { ($_, 1) } @{$g->{members}};
if (defined $existing) {
$g->{gid} = $existing->{gid} if !defined $g->{gid};
if ($g->{gid} != $existing->{gid}) {
dry_print("warning: not applying", "warning: would not apply", "GID change of group $name ($existing->{gid} -> $g->{gid})");
$g->{gid} = $existing->{gid};
}
$g->{password} = $existing->{password}; # do we want this?
if ($spec->{mutableUsers}) {
# Merge in non-declarative group members.
foreach my $uname (split /,/, $existing->{members} // "") {
$members{$uname} = 1 if !defined $declUsers{$uname};
}
}
} else {
$g->{gid} = allocGid($name) if !defined $g->{gid};
$g->{password} = "x";
}
$g->{members} = join ",", sort(keys(%members));
$groupsOut{$name} = $g;
$gidMap->{$name} = $g->{gid};
}
# Update the persistent list of declarative groups.
updateFile($declGroupsFile, join(" ", sort(keys %groupsOut)));
# Merge in the existing /etc/group.
foreach my $name (keys %groupsCur) {
my $g = $groupsCur{$name};
next if defined $groupsOut{$name};
if (!$spec->{mutableUsers} || defined $declGroups{$name}) {
dry_print("removing group", "would remove group", "$name");
} else {
$groupsOut{$name} = $g;
}
}
# Rewrite /etc/group. FIXME: acquire lock.
my @lines = map { join(":", $_->{name}, $_->{password}, $_->{gid}, $_->{members}) . "\n" }
(sort { $a->{gid} <=> $b->{gid} } values(%groupsOut));
updateFile($gidMapFile, to_json($gidMap));
updateFile("/etc/group", \@lines);
nscdInvalidate("group");
# Generate a new /etc/passwd containing the declared users.
my %usersOut;
foreach my $u (@{$spec->{users}}) {
my $name = $u->{name};
# Resolve the gid of the user.
if ($u->{group} =~ /^[0-9]$/) {
$u->{gid} = $u->{group};
} elsif (defined $groupsOut{$u->{group}}) {
$u->{gid} = $groupsOut{$u->{group}}->{gid} // die;
} else {
warn "warning: user $name has unknown group $u->{group}\n";
$u->{gid} = 65534;
}
my $existing = $usersCur{$name};
if (defined $existing) {
$u->{uid} = $existing->{uid} if !defined $u->{uid};
if ($u->{uid} != $existing->{uid}) {
dry_print("warning: not applying", "warning: would not apply", "UID change of user $name ($existing->{uid} -> $u->{uid})");
$u->{uid} = $existing->{uid};
}
} else {
$u->{uid} = allocUid($name, $u->{isSystemUser}) if !defined $u->{uid};
if (defined $u->{initialPassword}) {
$u->{hashedPassword} = hashPassword($u->{initialPassword});
} elsif (defined $u->{initialHashedPassword}) {
$u->{hashedPassword} = $u->{initialHashedPassword};
}
}
# Ensure home directory incl. ownership and permissions.
if ($u->{createHome}) {
make_path($u->{home}, { mode => 0700 }) if ! -e $u->{home} and ! $is_dry;
chown $u->{uid}, $u->{gid}, $u->{home};
chmod 0700, $u->{home};
}
if (defined $u->{passwordFile}) {
if (-e $u->{passwordFile}) {
$u->{hashedPassword} = read_file($u->{passwordFile});
chomp $u->{hashedPassword};
} else {
warn "warning: password file $u->{passwordFile} does not exist\n";
}
} elsif (defined $u->{password}) {
$u->{hashedPassword} = hashPassword($u->{password});
}
if (!defined $u->{shell}) {
if (defined $existing) {
$u->{shell} = $existing->{shell};
} else {
warn "warning: no declarative or previous shell for $name, setting shell to nologin\n";
$u->{shell} = "/run/current-system/sw/bin/nologin";
}
}
$u->{fakePassword} = $existing->{fakePassword} // "x";
$usersOut{$name} = $u;
$uidMap->{$name} = $u->{uid};
}
# Update the persistent list of declarative users.
updateFile($declUsersFile, join(" ", sort(keys %usersOut)));
# Merge in the existing /etc/passwd.
foreach my $name (keys %usersCur) {
my $u = $usersCur{$name};
next if defined $usersOut{$name};
if (!$spec->{mutableUsers} || defined $declUsers{$name}) {
dry_print("removing user", "would remove user", "$name");
} else {
$usersOut{$name} = $u;
}
}
# Rewrite /etc/passwd. FIXME: acquire lock.
@lines = map { join(":", $_->{name}, $_->{fakePassword}, $_->{uid}, $_->{gid}, $_->{description}, $_->{home}, $_->{shell}) . "\n" }
(sort { $a->{uid} <=> $b->{uid} } (values %usersOut));
updateFile($uidMapFile, to_json($uidMap));
updateFile("/etc/passwd", \@lines);
nscdInvalidate("passwd");
# Rewrite /etc/shadow to add new accounts or remove dead ones.
my @shadowNew;
my %shadowSeen;
foreach my $line (-f "/etc/shadow" ? read_file("/etc/shadow", { binmode => ":utf8" }) : ()) {
chomp $line;
my ($name, $hashedPassword, @rest) = split(':', $line, -9);
my $u = $usersOut{$name};;
next if !defined $u;
$hashedPassword = "!" if !$spec->{mutableUsers};
$hashedPassword = $u->{hashedPassword} if defined $u->{hashedPassword} && !$spec->{mutableUsers}; # FIXME
chomp $hashedPassword;
push @shadowNew, join(":", $name, $hashedPassword, @rest) . "\n";
$shadowSeen{$name} = 1;
}
foreach my $u (values %usersOut) {
next if defined $shadowSeen{$u->{name}};
my $hashedPassword = "!";
$hashedPassword = $u->{hashedPassword} if defined $u->{hashedPassword};
# FIXME: set correct value for sp_lstchg.
push @shadowNew, join(":", $u->{name}, $hashedPassword, "1::::::") . "\n";
}
updateFile("/etc/shadow", \@shadowNew, 0640);
{
my $uid = getpwnam "root";
my $gid = getgrnam "shadow";
my $path = "/etc/shadow";
(chown($uid, $gid, $path) || die "Failed to change ownership of $path: $!") unless $is_dry;
}
# Rewrite /etc/subuid & /etc/subgid to include default container mappings
my $subUidMapFile = "/var/lib/nixos/auto-subuid-map";
my $subUidMap = -e $subUidMapFile ? decode_json(read_file($subUidMapFile)) : {};
my (%subUidsUsed, %subUidsPrevUsed);
$subUidsPrevUsed{$_} = 1 foreach values %{$subUidMap};
sub allocSubUid {
my ($name, @rest) = @_;
# TODO: No upper bounds?
my ($min, $max, $up) = (100000, 100000 * 100, 1);
my $prevId = $subUidMap->{$name};
if (defined $prevId && !defined $subUidsUsed{$prevId}) {
$subUidsUsed{$prevId} = 1;
return $prevId;
}
my $id = allocId(\%subUidsUsed, \%subUidsPrevUsed, $min, $max, $up, sub { my ($uid) = @_; getpwuid($uid) });
my $offset = $id - 100000;
my $count = $offset * 65536;
my $subordinate = 100000 + $count;
return $subordinate;
}
my @subGids;
my @subUids;
foreach my $u (values %usersOut) {
my $name = $u->{name};
foreach my $range (@{$u->{subUidRanges}}) {
my $value = join(":", ($name, $range->{startUid}, $range->{count}));
push @subUids, $value;
}
foreach my $range (@{$u->{subGidRanges}}) {
my $value = join(":", ($name, $range->{startGid}, $range->{count}));
push @subGids, $value;
}
if($u->{autoSubUidGidRange}) {
my $subordinate = allocSubUid($name);
$subUidMap->{$name} = $subordinate;
my $value = join(":", ($name, $subordinate, 65536));
push @subUids, $value;
push @subGids, $value;
}
}
updateFile("/etc/subuid", join("\n", @subUids) . "\n");
updateFile("/etc/subgid", join("\n", @subGids) . "\n");
updateFile($subUidMapFile, encode_json($subUidMap) . "\n");