nixpkgs/nixos/modules/security/pam.nix

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# This module provides configuration for the PAM (Pluggable
# Authentication Modules) system.
{ config, lib, pkgs, ... }:
with lib;
let
parentConfig = config;
pamOpts = { config, name, ... }: let cfg = config; in let config = parentConfig; in {
options = {
name = mkOption {
example = "sshd";
type = types.str;
description = "Name of the PAM service.";
};
unixAuth = mkOption {
default = true;
type = types.bool;
description = ''
Whether users can log in with passwords defined in
<filename>/etc/shadow</filename>.
'';
};
rootOK = mkOption {
default = false;
type = types.bool;
description = ''
If set, root doesn't need to authenticate (e.g. for the
<command>useradd</command> service).
'';
};
u2fAuth = mkOption {
default = config.security.pam.enableU2F;
type = types.bool;
description = ''
If set, users listed in
<filename>~/.yubico/u2f_keys</filename> are able to log in
with the associated U2F key.
'';
};
usbAuth = mkOption {
default = config.security.pam.usb.enable;
type = types.bool;
description = ''
If set, users listed in
<filename>/etc/pamusb.conf</filename> are able to log in
with the associated USB key.
'';
};
otpwAuth = mkOption {
default = config.security.pam.enableOTPW;
type = types.bool;
description = ''
If set, the OTPW system will be used (if
<filename>~/.otpw</filename> exists).
'';
};
fprintAuth = mkOption {
default = config.services.fprintd.enable;
type = types.bool;
description = ''
If set, fingerprint reader will be used (if exists and
your fingerprints are enrolled).
'';
};
oathAuth = mkOption {
default = config.security.pam.oath.enable;
type = types.bool;
description = ''
If set, the OATH Toolkit will be used.
'';
};
sshAgentAuth = mkOption {
default = false;
type = types.bool;
description = ''
If set, the calling user's SSH agent is used to authenticate
against the keys in the calling user's
<filename>~/.ssh/authorized_keys</filename>. This is useful
for <command>sudo</command> on password-less remote systems.
'';
};
startSession = mkOption {
default = false;
type = types.bool;
description = ''
If set, the service will register a new session with
systemd's login manager. For local sessions, this will give
the user access to audio devices, CD-ROM drives. In the
default PolicyKit configuration, it also allows the user to
reboot the system.
'';
};
setEnvironment = mkOption {
type = types.bool;
default = true;
description = ''
Whether the service should set the environment variables
listed in <option>environment.sessionVariables</option>
using <literal>pam_env.so</literal>.
'';
};
setLoginUid = mkOption {
type = types.bool;
description = ''
Set the login uid of the process
(<filename>/proc/self/loginuid</filename>) for auditing
purposes. The login uid is only set by entry points like
<command>login</command> and <command>sshd</command>, not by
commands like <command>sudo</command>.
'';
};
forwardXAuth = mkOption {
default = false;
type = types.bool;
description = ''
Whether X authentication keys should be passed from the
calling user to the target user (e.g. for
<command>su</command>)
'';
};
pamMount = mkOption {
default = config.security.pam.mount.enable;
type = types.bool;
description = ''
Enable PAM mount (pam_mount) system to mount fileystems on user login.
'';
};
allowNullPassword = mkOption {
default = false;
type = types.bool;
description = ''
Whether to allow logging into accounts that have no password
set (i.e., have an empty password field in
<filename>/etc/passwd</filename> or
<filename>/etc/group</filename>). This does not enable
logging into disabled accounts (i.e., that have the password
field set to <literal>!</literal>). Note that regardless of
what the pam_unix documentation says, accounts with hashed
empty passwords are always allowed to log in.
'';
};
requireWheel = mkOption {
default = false;
type = types.bool;
description = ''
Whether to permit root access only to members of group wheel.
'';
};
limits = mkOption {
description = ''
Attribute set describing resource limits. Defaults to the
value of <option>security.pam.loginLimits</option>.
'';
};
showMotd = mkOption {
default = false;
type = types.bool;
description = "Whether to show the message of the day.";
};
makeHomeDir = mkOption {
default = false;
type = types.bool;
description = ''
Whether to try to create home directories for users
with <literal>$HOME</literal>s pointing to nonexistent
locations on session login.
'';
};
updateWtmp = mkOption {
default = false;
type = types.bool;
description = "Whether to update <filename>/var/log/wtmp</filename>.";
};
logFailures = mkOption {
default = false;
type = types.bool;
description = "Whether to log authentication failures in <filename>/var/log/faillog</filename>.";
};
enableAppArmor = mkOption {
default = false;
type = types.bool;
description = ''
Enable support for attaching AppArmor profiles at the
user/group level, e.g., as part of a role based access
control scheme.
'';
};
text = mkOption {
type = types.nullOr types.lines;
description = "Contents of the PAM service file.";
};
};
config = {
name = mkDefault name;
setLoginUid = mkDefault cfg.startSession;
limits = mkDefault config.security.pam.loginLimits;
# !!! TODO: move the LDAP stuff to the LDAP module, and the
# Samba stuff to the Samba module. This requires that the PAM
# module provides the right hooks.
text = mkDefault
(''
# Account management.
account sufficient pam_unix.so
${optionalString use_ldap
"account sufficient ${pam_ldap}/lib/security/pam_ldap.so"}
${optionalString config.services.sssd.enable
"account sufficient ${pkgs.sssd}/lib/security/pam_sss.so"}
${optionalString config.krb5.enable
"account sufficient ${pam_krb5}/lib/security/pam_krb5.so"}
# Authentication management.
${optionalString cfg.rootOK
"auth sufficient pam_rootok.so"}
${optionalString cfg.requireWheel
"auth required pam_wheel.so use_uid"}
${optionalString cfg.logFailures
"auth required pam_tally.so"}
${optionalString (config.security.pam.enableSSHAgentAuth && cfg.sshAgentAuth)
"auth sufficient ${pkgs.pam_ssh_agent_auth}/libexec/pam_ssh_agent_auth.so file=~/.ssh/authorized_keys:~/.ssh/authorized_keys2:/etc/ssh/authorized_keys.d/%u"}
${optionalString cfg.fprintAuth
"auth sufficient ${pkgs.fprintd}/lib/security/pam_fprintd.so"}
${optionalString cfg.u2fAuth
"auth sufficient ${pkgs.pam_u2f}/lib/security/pam_u2f.so"}
${optionalString cfg.usbAuth
"auth sufficient ${pkgs.pam_usb}/lib/security/pam_usb.so"}
${let oath = config.security.pam.oath; in optionalString cfg.oathAuth
"auth requisite ${pkgs.oathToolkit}/lib/security/pam_oath.so window=${toString oath.window} usersfile=${toString oath.usersFile} digits=${toString oath.digits}"}
'' +
# Modules in this block require having the password set in PAM_AUTHTOK.
# pam_unix is marked as 'sufficient' on NixOS which means nothing will run
# after it succeeds. Certain modules need to run after pam_unix
# prompts the user for password so we run it once with 'required' at an
# earlier point and it will run again with 'sufficient' further down.
# We use try_first_pass the second time to avoid prompting password twice
(optionalString (cfg.unixAuth && (config.security.pam.enableEcryptfs || cfg.pamMount)) ''
auth required pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} likeauth
${optionalString config.security.pam.enableEcryptfs
"auth optional ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so unwrap"}
${optionalString cfg.pamMount
"auth optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
'') + ''
${optionalString cfg.unixAuth
"auth sufficient pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} likeauth try_first_pass"}
${optionalString cfg.otpwAuth
"auth sufficient ${pkgs.otpw}/lib/security/pam_otpw.so"}
${optionalString use_ldap
"auth sufficient ${pam_ldap}/lib/security/pam_ldap.so use_first_pass"}
${optionalString config.services.sssd.enable
"auth sufficient ${pkgs.sssd}/lib/security/pam_sss.so use_first_pass"}
${optionalString config.krb5.enable ''
auth [default=ignore success=1 service_err=reset] ${pam_krb5}/lib/security/pam_krb5.so use_first_pass
auth [default=die success=done] ${pam_ccreds}/lib/security/pam_ccreds.so action=validate use_first_pass
auth sufficient ${pam_ccreds}/lib/security/pam_ccreds.so action=store use_first_pass
''}
auth required pam_deny.so
# Password management.
password requisite pam_unix.so nullok sha512
${optionalString config.security.pam.enableEcryptfs
"password optional ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so"}
${optionalString cfg.pamMount
"password optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
${optionalString use_ldap
"password sufficient ${pam_ldap}/lib/security/pam_ldap.so"}
${optionalString config.services.sssd.enable
"password sufficient ${pkgs.sssd}/lib/security/pam_sss.so use_authtok"}
${optionalString config.krb5.enable
"password sufficient ${pam_krb5}/lib/security/pam_krb5.so use_first_pass"}
${optionalString config.services.samba.syncPasswordsByPam
"password optional ${pkgs.samba}/lib/security/pam_smbpass.so nullok use_authtok try_first_pass"}
# Session management.
${optionalString cfg.setEnvironment ''
session required pam_env.so envfile=${config.system.build.pamEnvironment}
''}
session required pam_unix.so
${optionalString cfg.setLoginUid
"session ${
if config.boot.isContainer then "optional" else "required"
} pam_loginuid.so"}
${optionalString cfg.makeHomeDir
"session required ${pkgs.pam}/lib/security/pam_mkhomedir.so silent skel=${config.security.pam.makeHomeDir.skelDirectory} umask=0022"}
${optionalString cfg.updateWtmp
"session required ${pkgs.pam}/lib/security/pam_lastlog.so silent"}
${optionalString config.security.pam.enableEcryptfs
"session optional ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so"}
${optionalString use_ldap
"session optional ${pam_ldap}/lib/security/pam_ldap.so"}
${optionalString config.services.sssd.enable
"session optional ${pkgs.sssd}/lib/security/pam_sss.so"}
${optionalString config.krb5.enable
"session optional ${pam_krb5}/lib/security/pam_krb5.so"}
${optionalString cfg.otpwAuth
"session optional ${pkgs.otpw}/lib/security/pam_otpw.so"}
${optionalString cfg.startSession
"session optional ${pkgs.systemd}/lib/security/pam_systemd.so"}
${optionalString cfg.forwardXAuth
"session optional pam_xauth.so xauthpath=${pkgs.xorg.xauth}/bin/xauth systemuser=99"}
${optionalString (cfg.limits != [])
"session required ${pkgs.pam}/lib/security/pam_limits.so conf=${makeLimitsConf cfg.limits}"}
${optionalString (cfg.showMotd && config.users.motd != null)
"session optional ${pkgs.pam}/lib/security/pam_motd.so motd=${motd}"}
${optionalString cfg.pamMount
"session optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
${optionalString (cfg.enableAppArmor && config.security.apparmor.enable)
"session optional ${pkgs.apparmor-pam}/lib/security/pam_apparmor.so order=user,group,default debug"}
'');
};
};
inherit (pkgs) pam_krb5 pam_ccreds;
use_ldap = (config.users.ldap.enable && config.users.ldap.loginPam);
pam_ldap = if config.users.ldap.daemon.enable then pkgs.nss_pam_ldapd else pkgs.pam_ldap;
# Create a limits.conf(5) file.
makeLimitsConf = limits:
pkgs.writeText "limits.conf"
(concatMapStrings ({ domain, type, item, value }:
"${domain} ${type} ${item} ${toString value}\n")
limits);
motd = pkgs.writeText "motd" config.users.motd;
makePAMService = pamService:
{ source = pkgs.writeText "${pamService.name}.pam" pamService.text;
target = "pam.d/${pamService.name}";
};
in
{
###### interface
options = {
security.pam.loginLimits = mkOption {
default = [];
example =
[ { domain = "ftp";
type = "hard";
item = "nproc";
value = "0";
}
{ domain = "@student";
type = "-";
item = "maxlogins";
value = "4";
}
];
description =
'' Define resource limits that should apply to users or groups.
Each item in the list should be an attribute set with a
<varname>domain</varname>, <varname>type</varname>,
<varname>item</varname>, and <varname>value</varname>
attribute. The syntax and semantics of these attributes
must be that described in the limits.conf(5) man page.
'';
};
security.pam.services = mkOption {
default = [];
type = with types; loaOf (submodule pamOpts);
description =
''
This option defines the PAM services. A service typically
corresponds to a program that uses PAM,
e.g. <command>login</command> or <command>passwd</command>.
Each attribute of this set defines a PAM service, with the attribute name
defining the name of the service.
'';
};
security.pam.makeHomeDir.skelDirectory = mkOption {
type = types.str;
default = "/var/empty";
example = "/etc/skel";
description = ''
Path to skeleton directory whose contents are copied to home
directories newly created by <literal>pam_mkhomedir</literal>.
'';
};
security.pam.enableSSHAgentAuth = mkOption {
default = false;
description =
''
Enable sudo logins if the user's SSH agent provides a key
present in <filename>~/.ssh/authorized_keys</filename>.
This allows machines to exclusively use SSH keys instead of
passwords.
'';
};
security.pam.enableOTPW = mkOption {
default = false;
description = ''
Enable the OTPW (one-time password) PAM module.
'';
};
security.pam.enableU2F = mkOption {
default = false;
description = ''
Enable the U2F PAM module.
'';
};
security.pam.enableEcryptfs = mkOption {
default = false;
description = ''
Enable eCryptfs PAM module (mounting ecryptfs home directory on login).
'';
};
users.motd = mkOption {
default = null;
example = "Today is Sweetmorn, the 4th day of The Aftermath in the YOLD 3178.";
type = types.nullOr types.lines;
description = "Message of the day shown to users when they log in.";
};
};
###### implementation
config = {
environment.systemPackages =
# Include the PAM modules in the system path mostly for the manpages.
[ pkgs.pam ]
++ optional config.users.ldap.enable pam_ldap
++ optional config.services.sssd.enable pkgs.sssd
++ optionals config.krb5.enable [pam_krb5 pam_ccreds]
++ optionals config.security.pam.enableOTPW [ pkgs.otpw ]
++ optionals config.security.pam.oath.enable [ pkgs.oathToolkit ]
++ optionals config.security.pam.enableU2F [ pkgs.pam_u2f ]
++ optionals config.security.pam.enableEcryptfs [ pkgs.ecryptfs ];
security.setuidPrograms =
optionals config.security.pam.enableEcryptfs [ "mount.ecryptfs_private" "umount.ecryptfs_private" ];
environment.etc =
mapAttrsToList (n: v: makePAMService v) config.security.pam.services;
security.setuidOwners = [ {
program = "unix_chkpwd";
source = "${pkgs.pam}/sbin/unix_chkpwd.orig";
owner = "root";
setuid = true;
} ];
security.pam.services =
{ other.text =
''
auth required pam_warn.so
auth required pam_deny.so
account required pam_warn.so
account required pam_deny.so
password required pam_warn.so
password required pam_deny.so
session required pam_warn.so
session required pam_deny.so
'';
# Most of these should be moved to specific modules.
cups = {};
ftp = {};
i3lock = {};
i3lock-color = {};
screen = {};
vlock = {};
xlock = {};
xscreensaver = {};
runuser = { rootOK = true; unixAuth = false; setEnvironment = false; };
/* FIXME: should runuser -l start a systemd session? Currently
it complains "Cannot create session: Already running in a
session". */
runuser-l = { rootOK = true; unixAuth = false; };
};
};
}