nixpkgs/nixos/modules/config/update-users-groups.pl
Eelco Dolstra a57bcd38b4
update-users-groups.pl: Keep track of deallocated UIDs/GIDs
When a user or group is revived, this allows it to be allocated the
UID/GID it had before.

A consequence is that UIDs and GIDs are no longer reused.

Fixes #24010.
2017-03-29 18:13:18 +02:00

283 lines
9.1 KiB
Perl
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use strict;
use File::Path qw(make_path);
use File::Slurp;
use JSON;
make_path("/var/lib/nixos", { mode => 0755 });
# 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)) : {};
sub updateFile {
my ($path, $contents, $perms) = @_;
write_file("$path.tmp", { binmode => ':utf8', perms => $perms // 0644 }, $contents);
rename("$path.tmp", $path) or die;
}
sub hashPassword {
my ($password) = @_;
my $salt = "";
my @chars = ('.', '/', 0..9, 'A'..'Z', 'a'..'z');
$salt .= $chars[rand 64] for (1..8);
return crypt($password, '$6$' . $salt . '$');
}
# 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}) {
print STDERR "reviving group '$name' with GID $prevGid\n";
$gidsUsed{$prevGid} = 1;
return $prevGid;
}
return allocId(\%gidsUsed, \%gidsPrevUsed, 400, 499, 0, sub { my ($gid) = @_; getgrgid($gid) });
}
sub allocUid {
my ($name, $isSystemUser) = @_;
my ($min, $max, $up) = $isSystemUser ? (400, 499, 0) : (1000, 29999, 1);
my $prevUid = $uidMap->{$name};
if (defined $prevUid && $prevUid >= $min && $prevUid <= $max && !defined $uidsUsed{$prevUid}) {
print STDERR "reviving user '$name' with UID $prevUid\n";
$uidsUsed{$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") : ();
# 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") : ();
# 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) : "";
# Idem for the users.
my $declUsersFile = "/var/lib/nixos/declarative-users";
my %declUsers;
$declUsers{$_} = 1 foreach split / /, -e $declUsersFile ? read_file($declUsersFile) : "";
# 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}) {
warn "warning: not applying GID change of group $name ($existing->{gid} -> $g->{gid})\n";
$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}) {
print STDERR "removing group $name\n";
} 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, encode_json($gidMap));
updateFile("/etc/group", \@lines);
system("nscd --invalidate 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}) {
warn "warning: not applying UID change of user $name ($existing->{uid} -> $u->{uid})\n";
$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} = $u->{initialHashedPassword};
}
}
# Create a home directory.
if ($u->{createHome}) {
make_path($u->{home}, { mode => 0700 }) if ! -e $u->{home};
chown $u->{uid}, $u->{gid}, $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});
}
$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}) {
print STDERR "removing user $name\n";
} 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, encode_json($uidMap));
updateFile("/etc/passwd", \@lines);
system("nscd --invalidate 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") : ()) {
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
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, 0600);