diff --git a/nixops/desktop.nix b/nixops/desktop.nix
index 04760eb..0429ed8 100644
--- a/nixops/desktop.nix
+++ b/nixops/desktop.nix
@@ -8,9 +8,11 @@ in
 {
   deployment.targetHost = host;
 
+  disabledModules = [ "security/pam.nix" ];
   imports =
     [
       (./. + "/${host}-hardware-configuration.nix")
+      ./pam_p11
     ];
 
   networking.hostName = host;
@@ -21,6 +23,7 @@ in
   # $ nix search wget
   nixpkgs.config.allowUnfree = true;
   environment.systemPackages = with pkgs; [
+    opensc yubikey-manager yubikey-manager-qt
     wget vim gitAndTools.gitFull firefox thunderbird hexchat usbutils pciutils file lm_sensors audacious acpi
     gimp imagemagick
     (python3.withPackages(ps: with ps; [ numpy scipy matplotlib qtconsole regex ]))
@@ -52,6 +55,7 @@ in
   programs.ssh.startAgent = true;
   services.gnome3.gnome-keyring.enable = pkgs.lib.mkForce false;
   programs.ssh.agentPKCS11Whitelist = "${pkgs.opensc}/lib/opensc-pkcs11.so";
+  security.pam.p11.enable = true;
 
   # Enable CUPS to print documents.
   services.printing = {
diff --git a/nixops/light.nix b/nixops/light.nix
index 266f2bd..39fb23a 100644
--- a/nixops/light.nix
+++ b/nixops/light.nix
@@ -4,9 +4,11 @@
 {
   deployment.targetHost = host;
 
+  disabledModules = [ "security/pam.nix" ];
   imports =
     [
       (./. + "/${host}-hardware-configuration.nix")
+      ./pam_p11
     ];
 
   networking.hostName = host;
@@ -18,6 +20,7 @@
   documentation.enable = false;
   nixpkgs.config.allowUnfree = true;
   environment.systemPackages = with pkgs; [
+    opensc
     wget vim git firefox usbutils pciutils file lm_sensors acpi
     gimp imagemagick
     (python3.withPackages(ps: with ps; [ numpy scipy ]))
@@ -40,6 +43,7 @@
     '';
   programs.ssh.startAgent = true;
   programs.ssh.agentPKCS11Whitelist = "${pkgs.opensc}/lib/opensc-pkcs11.so";
+  security.pam.p11.enable = true;
 
   # Enable CUPS to print documents.
   services.printing = {
diff --git a/nixops/pam_p11/default.nix b/nixops/pam_p11/default.nix
new file mode 100644
index 0000000..5945535
--- /dev/null
+++ b/nixops/pam_p11/default.nix
@@ -0,0 +1,843 @@
+# This module provides configuration for the PAM (Pluggable
+# Authentication Modules) system.
+
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  pam_p11 = pkgs.callPackage ./pam_p11.nix {};
+
+  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).
+        '';
+      };
+
+      p11Auth = mkOption {
+        default = config.security.pam.p11.enable;
+        type = types.bool;
+        description = ''
+          If set, keys listed in
+          <filename>~/.ssh/authorized_keys</filename> and
+          <filename>~/.eid/authorized_certificates</filename>
+          can be used to log in with the associated PKCS#11 tokens.
+        '';
+      };
+
+      u2fAuth = mkOption {
+        default = config.security.pam.u2f.enable;
+        type = types.bool;
+        description = ''
+          If set, users listed in
+          <filename>$XDG_CONFIG_HOME/Yubico/u2f_keys</filename> (or
+          <filename>$HOME/.config/Yubico/u2f_keys</filename> if XDG variable is
+          not set) are able to log in with the associated U2F key. Path can be
+          changed using <option>security.pam.u2f.authFile</option> option.
+        '';
+      };
+
+      yubicoAuth = mkOption {
+        default = config.security.pam.yubico.enable;
+        type = types.bool;
+        description = ''
+          If set, users listed in
+          <filename>~/.yubico/authorized_yubikeys</filename>
+          are able to log in with the associated Yubikey tokens.
+        '';
+      };
+
+      googleAuthenticator = {
+        enable = mkOption {
+          default = false;
+          type = types.bool;
+          description = ''
+            If set, users with enabled Google Authenticator (created
+            <filename>~/.google_authenticator</filename>) will be required
+            to provide Google Authenticator token to log in.
+          '';
+        };
+      };
+
+      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).
+        '';
+      };
+
+      googleOsLoginAccountVerification = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          If set, will use the Google OS Login PAM modules
+          (<literal>pam_oslogin_login</literal>,
+          <literal>pam_oslogin_admin</literal>) to verify possible OS Login
+          users and set sudoers configuration accordingly.
+          This only makes sense to enable for the <literal>sshd</literal> PAM
+          service.
+        '';
+      };
+
+      googleOsLoginAuthentication = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          If set, will use the <literal>pam_oslogin_login</literal>'s user
+          authentication methods to authenticate users using 2FA.
+          This only makes sense to enable for the <literal>sshd</literal> PAM
+          service.
+        '';
+      };
+
+      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.
+        '';
+      };
+
+      duoSecurity = {
+        enable = mkOption {
+          default = false;
+          type = types.bool;
+          description = ''
+            If set, use the Duo Security pam module
+            <literal>pam_duo</literal> for authentication.  Requires
+            configuration of <option>security.duosec</option> options.
+          '';
+        };
+      };
+
+      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.
+        '';
+      };
+
+      nodelay = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          Wheather the delay after typing a wrong password should be disabled.
+        '';
+      };
+
+      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.
+        '';
+      };
+
+      enableKwallet = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          If enabled, pam_wallet will attempt to automatically unlock the
+          user's default KDE wallet upon login. If the user has no wallet named
+          "kdewallet", or the login password does not match their wallet
+          password, KDE will prompt separately after login.
+        '';
+      };
+      sssdStrictAccess = mkOption {
+        default = false;
+        type = types.bool;
+        description = "enforce sssd access control";
+      };
+
+      enableGnomeKeyring = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          If enabled, pam_gnome_keyring will attempt to automatically unlock the
+          user's default Gnome keyring upon login. If the user login password does
+          not match their keyring password, Gnome Keyring will prompt separately
+          after login.
+        '';
+      };
+
+      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 required pam_unix.so
+          ${optionalString use_ldap
+              "account sufficient ${pam_ldap}/lib/security/pam_ldap.so"}
+          ${optionalString (config.services.sssd.enable && cfg.sssdStrictAccess==false)
+              "account sufficient ${pkgs.sssd}/lib/security/pam_sss.so"}
+          ${optionalString (config.services.sssd.enable && cfg.sssdStrictAccess)
+              "account [default=bad success=ok user_unknown=ignore] ${pkgs.sssd}/lib/security/pam_sss.so"}
+          ${optionalString config.krb5.enable
+              "account sufficient ${pam_krb5}/lib/security/pam_krb5.so"}
+          ${optionalString cfg.googleOsLoginAccountVerification ''
+            account [success=ok ignore=ignore default=die] ${pkgs.google-compute-engine-oslogin}/lib/pam_oslogin_login.so
+            account [success=ok default=ignore] ${pkgs.google-compute-engine-oslogin}/lib/pam_oslogin_admin.so
+          ''}
+
+          # Authentication management.
+          ${optionalString cfg.googleOsLoginAuthentication
+              "auth [success=done perm_denied=bad default=ignore] ${pkgs.google-compute-engine-oslogin}/lib/pam_oslogin_login.so"}
+          ${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"}
+          ${let p11 = config.security.pam.p11; in optionalString cfg.p11Auth
+              "auth ${p11.control} ${pam_p11}/lib/security/pam_p11.so ${pkgs.opensc}/lib/opensc-pkcs11.so"}
+          ${let u2f = config.security.pam.u2f; in optionalString cfg.u2fAuth
+              "auth ${u2f.control} ${pkgs.pam_u2f}/lib/security/pam_u2f.so ${optionalString u2f.debug "debug"} ${optionalString (u2f.authFile != null) "authfile=${u2f.authFile}"} ${optionalString u2f.interactive "interactive"} ${optionalString u2f.cue "cue"}"}
+          ${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}"}
+          ${let yubi = config.security.pam.yubico; in optionalString cfg.yubicoAuth
+              "auth ${yubi.control} ${pkgs.yubico-pam}/lib/security/pam_yubico.so mode=${toString yubi.mode} ${optionalString (yubi.mode == "client") "id=${toString yubi.id}"} ${optionalString yubi.debug "debug"}"}
+        '' +
+          # 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
+            || cfg.enableKwallet
+            || cfg.enableGnomeKeyring
+            || cfg.googleAuthenticator.enable
+            || cfg.duoSecurity.enable)) ''
+              auth required pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} ${optionalString cfg.nodelay "nodelay"} 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.enableKwallet
+                ("auth optional ${pkgs.plasma5.kwallet-pam}/lib/security/pam_kwallet5.so" +
+                 " kwalletd=${pkgs.libsForQt5.kwallet.bin}/bin/kwalletd5")}
+              ${optionalString cfg.enableGnomeKeyring
+                "auth optional ${pkgs.gnome3.gnome-keyring}/lib/security/pam_gnome_keyring.so"}
+              ${optionalString cfg.googleAuthenticator.enable
+                "auth required ${pkgs.googleAuthenticator}/lib/security/pam_google_authenticator.so no_increment_hotp"}
+              ${optionalString cfg.duoSecurity.enable
+                "auth required ${pkgs.duo-unix}/lib/security/pam_duo.so"}
+            '') + ''
+          ${optionalString cfg.unixAuth
+              "auth sufficient pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} ${optionalString cfg.nodelay "nodelay"} 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 sufficient 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"}
+          ${optionalString cfg.enableGnomeKeyring
+              "password optional ${pkgs.gnome3.gnome-keyring}/lib/security/pam_gnome_keyring.so use_authtok"}
+
+          # Session management.
+          ${optionalString cfg.setEnvironment ''
+            session required pam_env.so conffile=${config.system.build.pamEnvironment} readenv=0
+          ''}
+          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"}
+          ${optionalString (cfg.enableKwallet)
+              ("session optional ${pkgs.plasma5.kwallet-pam}/lib/security/pam_kwallet5.so" +
+               " kwalletd=${pkgs.libsForQt5.kwallet.bin}/bin/kwalletd5")}
+          ${optionalString (cfg.enableGnomeKeyring)
+              "session optional ${pkgs.gnome3.gnome-keyring}/lib/security/pam_gnome_keyring.so auto_start"}
+          ${optionalString (config.virtualisation.lxc.lxcfs.enable)
+               "session optional ${pkgs.lxc}/lib/security/pam_cgfs.so -c all"}
+        '');
+    };
+
+  };
+
+
+  inherit (pkgs) pam_krb5 pam_ccreds;
+
+  use_ldap = (config.users.ldap.enable && config.users.ldap.loginPam);
+  pam_ldap = if config.users.ldap.daemon.enable then pkgs.nss_pam_ldapd else pkgs.pam_ldap;
+
+  # Create a limits.conf(5) file.
+  makeLimitsConf = limits:
+    pkgs.writeText "limits.conf"
+       (concatMapStrings ({ domain, type, item, value }:
+         "${domain} ${type} ${item} ${toString value}\n")
+         limits);
+
+  motd = pkgs.writeText "motd" config.users.motd;
+
+  makePAMService = name: service:
+    { name = "pam.d/${name}";
+      value.source = pkgs.writeText "${name}.pam" service.text;
+    };
+
+in
+
+{
+
+  imports = [
+    (mkRenamedOptionModule [ "security" "pam" "enableU2F" ] [ "security" "pam" "u2f" "enable" ])
+  ];
+
+  ###### 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.
+
+          Note that these limits do not apply to systemd services,
+          whose limits can be changed via <option>systemd.extraConfig</option>
+          instead.
+       '';
+    };
+
+    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 {
+      type = types.bool;
+      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 = mkEnableOption "the OTPW (one-time password) PAM module";
+
+    security.pam.p11 = {
+      enable = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          Enables P11 PAM (<literal>pam_p11</literal>) module.
+
+          If set, users can log in with SSH keys and PKCS#11 tokens.
+
+          More information can be found <link
+          xlink:href="https://github.com/OpenSC/pam_p11">here</link>.
+        '';
+      };
+
+      control = mkOption {
+        default = "sufficient";
+        type = types.enum [ "required" "requisite" "sufficient" "optional" ];
+        description = ''
+          This option sets pam "control".
+          If you want to have multi factor authentication, use "required".
+          If you want to use the PKCS#11 device instead of the regular password,
+          use "sufficient".
+
+          Read
+          <citerefentry>
+            <refentrytitle>pam.conf</refentrytitle>
+            <manvolnum>5</manvolnum>
+          </citerefentry>
+          for better understanding of this option.
+        '';
+      };
+    };
+
+    security.pam.u2f = {
+      enable = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          Enables U2F PAM (<literal>pam-u2f</literal>) module.
+
+          If set, users listed in
+          <filename>$XDG_CONFIG_HOME/Yubico/u2f_keys</filename> (or
+          <filename>$HOME/.config/Yubico/u2f_keys</filename> if XDG variable is
+          not set) are able to log in with the associated U2F key. The path can
+          be changed using <option>security.pam.u2f.authFile</option> option.
+
+          File format is:
+          <literal>username:first_keyHandle,first_public_key: second_keyHandle,second_public_key</literal>
+          This file can be generated using <command>pamu2fcfg</command> command.
+
+          More information can be found <link
+          xlink:href="https://developers.yubico.com/pam-u2f/">here</link>.
+        '';
+      };
+
+      authFile = mkOption {
+        default = null;
+        type = with types; nullOr path;
+        description = ''
+          By default <literal>pam-u2f</literal> module reads the keys from
+          <filename>$XDG_CONFIG_HOME/Yubico/u2f_keys</filename> (or
+          <filename>$HOME/.config/Yubico/u2f_keys</filename> if XDG variable is
+          not set).
+
+          If you want to change auth file locations or centralize database (for
+          example use <filename>/etc/u2f-mappings</filename>) you can set this
+          option.
+
+          File format is:
+          <literal>username:first_keyHandle,first_public_key: second_keyHandle,second_public_key</literal>
+          This file can be generated using <command>pamu2fcfg</command> command.
+
+          More information can be found <link
+          xlink:href="https://developers.yubico.com/pam-u2f/">here</link>.
+        '';
+      };
+
+      control = mkOption {
+        default = "sufficient";
+        type = types.enum [ "required" "requisite" "sufficient" "optional" ];
+        description = ''
+          This option sets pam "control".
+          If you want to have multi factor authentication, use "required".
+          If you want to use U2F device instead of regular password, use "sufficient".
+
+          Read
+          <citerefentry>
+            <refentrytitle>pam.conf</refentrytitle>
+            <manvolnum>5</manvolnum>
+          </citerefentry>
+          for better understanding of this option.
+        '';
+      };
+
+      debug = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          Debug output to stderr.
+        '';
+      };
+
+      interactive = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          Set to prompt a message and wait before testing the presence of a U2F device.
+          Recommended if your device doesn’t have a tactile trigger.
+        '';
+      };
+
+      cue = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          By default <literal>pam-u2f</literal> module does not inform user
+          that he needs to use the u2f device, it just waits without a prompt.
+
+          If you set this option to <literal>true</literal>,
+          <literal>cue</literal> option is added to <literal>pam-u2f</literal>
+          module and reminder message will be displayed.
+        '';
+      };
+    };
+
+    security.pam.yubico = {
+      enable = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          Enables Yubico PAM (<literal>yubico-pam</literal>) module.
+
+          If set, users listed in
+          <filename>~/.yubico/authorized_yubikeys</filename>
+          are able to log in with the associated Yubikey tokens.
+
+          The file must have only one line:
+          <literal>username:yubikey_token_id1:yubikey_token_id2</literal>
+          More information can be found <link
+          xlink:href="https://developers.yubico.com/yubico-pam/">here</link>.
+        '';
+      };
+      control = mkOption {
+        default = "sufficient";
+        type = types.enum [ "required" "requisite" "sufficient" "optional" ];
+        description = ''
+          This option sets pam "control".
+          If you want to have multi factor authentication, use "required".
+          If you want to use Yubikey instead of regular password, use "sufficient".
+
+          Read
+          <citerefentry>
+            <refentrytitle>pam.conf</refentrytitle>
+            <manvolnum>5</manvolnum>
+          </citerefentry>
+          for better understanding of this option.
+        '';
+      };
+      id = mkOption {
+        example = "42";
+        type = types.str;
+        description = "client id";
+      };
+
+      debug = mkOption {
+        default = false;
+        type = types.bool;
+        description = ''
+          Debug output to stderr.
+        '';
+      };
+      mode = mkOption {
+        default = "client";
+        type = types.enum [ "client" "challenge-response" ];
+        description = ''
+          Mode of operation.
+
+          Use "client" for online validation with a YubiKey validation service such as
+          the YubiCloud.
+
+          Use "challenge-response" for offline validation using YubiKeys with HMAC-SHA-1
+          Challenge-Response configurations. See the man-page ykpamcfg(1) for further
+          details on how to configure offline Challenge-Response validation.
+
+          More information can be found <link
+          xlink:href="https://developers.yubico.com/yubico-pam/Authentication_Using_Challenge-Response.html">here</link>.
+        '';
+      };
+    };
+
+    security.pam.enableEcryptfs = mkEnableOption "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.p11.enable [ pam_p11 ]
+      ++ optionals config.security.pam.u2f.enable [ pkgs.pam_u2f ];
+
+    boot.supportedFilesystems = optionals config.security.pam.enableEcryptfs [ "ecryptfs" ];
+
+    security.wrappers = {
+      unix_chkpwd = {
+        source = "${pkgs.pam}/sbin/unix_chkpwd.orig";
+        owner = "root";
+        setuid = true;
+      };
+    };
+
+    environment.etc = mapAttrs' makePAMService config.security.pam.services;
+
+    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.
+        i3lock = {};
+        i3lock-color = {};
+        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; };
+      };
+
+  };
+
+}
diff --git a/nixops/pam_p11/pam_p11.nix b/nixops/pam_p11/pam_p11.nix
new file mode 100644
index 0000000..2257bd5
--- /dev/null
+++ b/nixops/pam_p11/pam_p11.nix
@@ -0,0 +1,23 @@
+{ stdenv, fetchFromGitHub, autoreconfHook, pkg-config, openssl, libp11, pam }:
+
+stdenv.mkDerivation rec {
+  pname = "pam_p11";
+  version = "0.3.1";
+
+  src = fetchFromGitHub {
+    owner = "OpenSC";
+    repo = "pam_p11";
+    rev = "pam_p11-${version}";
+    sha256 = "1caidy18rq5zk82d51x8vwidmkhwmanf3qm25x1yrdlbhxv6m7lk";
+  };
+
+  patchPhase =
+    ''
+    substituteInPlace src/match_openssh.c --replace \
+      '"%s/.ssh/authorized_keys", pw->pw_dir)' \
+      '"/etc/ssh/authorized_keys.d/%s", pw->pw_name)'
+    '';
+
+  nativeBuildInputs = [ autoreconfHook pkg-config ];
+  buildInputs = [ pam openssl libp11 ];
+}