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