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# Configuration for the pwdutils suite of tools: passwd, useradd, etc.
{ config, lib, utils, pkgs, ... }:
with lib;
let
cfg = config.security.loginDefs;
in
{
options = with types; {
security.loginDefs = {
package = mkPackageOptionMD pkgs "shadow" { };
chfnRestrict = mkOption {
description = mdDoc ''
Use chfn SUID to allow non-root users to change their account GECOS information.
'';
type = nullOr str;
default = null;
};
settings = mkOption {
description = mdDoc ''
Config options for the /etc/login.defs file, that defines
the site-specific configuration for the shadow password suite.
See login.defs(5) man page for available options.
'';
type = submodule {
freeformType = (pkgs.formats.keyValue { }).type;
/* There are three different sources for user/group id ranges, each of which gets
used by different programs:
- The login.defs file, used by the useradd, groupadd and newusers commands
- The update-users-groups.pl file, used by NixOS in the activation phase to
decide on which ids to use for declaratively defined users without a static
id
- Systemd compile time options -Dsystem-uid-max= and -Dsystem-gid-max=, used
by systemd for features like ConditionUser=@system and systemd-sysusers
*/
options = {
DEFAULT_HOME = mkOption {
description = mdDoc "Indicate if login is allowed if we can't cd to the home directory.";
default = "yes";
type = enum [ "yes" "no" ];
};
ENCRYPT_METHOD = mkOption {
description = mdDoc "This defines the system default encryption algorithm for encrypting passwords.";
# The default crypt() method, keep in sync with the PAM default
default = "YESCRYPT";
type = enum [ "YESCRYPT" "SHA512" "SHA256" "MD5" "DES"];
};
SYS_UID_MIN = mkOption {
description = mdDoc "Range of user IDs used for the creation of system users by useradd or newusers.";
default = 400;
type = int;
};
SYS_UID_MAX = mkOption {
description = mdDoc "Range of user IDs used for the creation of system users by useradd or newusers.";
default = 999;
type = int;
};
UID_MIN = mkOption {
description = mdDoc "Range of user IDs used for the creation of regular users by useradd or newusers.";
default = 1000;
type = int;
};
UID_MAX = mkOption {
description = mdDoc "Range of user IDs used for the creation of regular users by useradd or newusers.";
default = 29999;
type = int;
};
SYS_GID_MIN = mkOption {
description = mdDoc "Range of group IDs used for the creation of system groups by useradd, groupadd, or newusers";
default = 400;
type = int;
};
SYS_GID_MAX = mkOption {
description = mdDoc "Range of group IDs used for the creation of system groups by useradd, groupadd, or newusers";
default = 999;
type = int;
};
GID_MIN = mkOption {
description = mdDoc "Range of group IDs used for the creation of regular groups by useradd, groupadd, or newusers.";
default = 1000;
type = int;
};
GID_MAX = mkOption {
description = mdDoc "Range of group IDs used for the creation of regular groups by useradd, groupadd, or newusers.";
default = 29999;
type = int;
};
TTYGROUP = mkOption {
description = mdDoc ''
The terminal permissions: the login tty will be owned by the TTYGROUP group,
and the permissions will be set to TTYPERM'';
default = "tty";
type = str;
};
TTYPERM = mkOption {
description = mdDoc ''
The terminal permissions: the login tty will be owned by the TTYGROUP group,
and the permissions will be set to TTYPERM'';
default = "0620";
type = str;
};
# Ensure privacy for newly created home directories.
UMASK = mkOption {
description = mdDoc "The file mode creation mask is initialized to this value.";
default = "077";
type = str;
};
};
};
default = { };
};
};
users.defaultUserShell = mkOption {
description = mdDoc ''
This option defines the default shell assigned to user
accounts. This can be either a full system path or a shell package.
This must not be a store path, since the path is
used outside the store (in particular in /etc/passwd).
'';
example = literalExpression "pkgs.zsh";
type = either path shellPackage;
};
};
###### implementation
config = {
assertions = [
{
assertion = cfg.settings.SYS_UID_MIN <= cfg.settings.SYS_UID_MAX;
message = "SYS_UID_MIN must be less than or equal to SYS_UID_MAX";
}
{
assertion = cfg.settings.UID_MIN <= cfg.settings.UID_MAX;
message = "UID_MIN must be less than or equal to UID_MAX";
}
{
assertion = cfg.settings.SYS_GID_MIN <= cfg.settings.SYS_GID_MAX;
message = "SYS_GID_MIN must be less than or equal to SYS_GID_MAX";
}
{
assertion = cfg.settings.GID_MIN <= cfg.settings.GID_MAX;
message = "GID_MIN must be less than or equal to GID_MAX";
}
];
security.loginDefs.settings.CHFN_RESTRICT =
mkIf (cfg.chfnRestrict != null) cfg.chfnRestrict;
environment.systemPackages = optional config.users.mutableUsers cfg.package
++ optional (types.shellPackage.check config.users.defaultUserShell) config.users.defaultUserShell
++ optional (cfg.chfnRestrict != null) pkgs.util-linux;
environment.etc =
# Create custom toKeyValue generator
# see https://man7.org/linux/man-pages/man5/login.defs.5.html for config specification
let
toKeyValue = generators.toKeyValue {
mkKeyValue = generators.mkKeyValueDefault { } " ";
};
in
{
# /etc/login.defs: global configuration for pwdutils.
# You cannot login without it!
"login.defs".source = pkgs.writeText "login.defs" (toKeyValue cfg.settings);
# /etc/default/useradd: configuration for useradd.
"default/useradd".source = pkgs.writeText "useradd" ''
GROUP=100
HOME=/home
SHELL=${utils.toShellPath config.users.defaultUserShell}
'';
};
security.pam.services = {
chsh = { rootOK = true; };
chfn = { rootOK = true; };
su = {
rootOK = true;
forwardXAuth = true;
logFailures = true;
};
passwd = { };
# Note: useradd, groupadd etc. aren't setuid root, so it
# doesn't really matter what the PAM config says as long as it
# lets root in.
useradd.rootOK = true;
usermod.rootOK = true;
userdel.rootOK = true;
groupadd.rootOK = true;
groupmod.rootOK = true;
groupmems.rootOK = true;
groupdel.rootOK = true;
login = {
startSession = true;
allowNullPassword = true;
showMotd = true;
updateWtmp = true;
};
chpasswd = { rootOK = true; };
};
security.wrappers =
let
mkSetuidRoot = source: {
setuid = true;
owner = "root";
group = "root";
inherit source;
};
in
{
su = mkSetuidRoot "${cfg.package.su}/bin/su";
sg = mkSetuidRoot "${cfg.package.out}/bin/sg";
newgrp = mkSetuidRoot "${cfg.package.out}/bin/newgrp";
newuidmap = mkSetuidRoot "${cfg.package.out}/bin/newuidmap";
newgidmap = mkSetuidRoot "${cfg.package.out}/bin/newgidmap";
}
// optionalAttrs config.users.mutableUsers {
chsh = mkSetuidRoot "${cfg.package.out}/bin/chsh";
passwd = mkSetuidRoot "${cfg.package.out}/bin/passwd";
};
};
}
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