a05a340e26
Run pam_unix an additional time rather than switching it from sufficient to required. This fixes a potential security issue for ecryptfs/pam_mount users as with pam_deny gone, if cfg.unixAuth = False then it is possible to login without a password.
491 lines
17 KiB
Nix
491 lines
17 KiB
Nix
# This module provides configuration for the PAM (Pluggable
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# Authentication Modules) system.
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{ config, lib, pkgs, ... }:
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with lib;
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let
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parentConfig = config;
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pamOpts = { config, name, ... }: let cfg = config; in let config = parentConfig; in {
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options = {
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name = mkOption {
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example = "sshd";
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type = types.str;
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description = "Name of the PAM service.";
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};
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unixAuth = mkOption {
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default = true;
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type = types.bool;
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description = ''
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Whether users can log in with passwords defined in
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<filename>/etc/shadow</filename>.
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'';
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};
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rootOK = mkOption {
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default = false;
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type = types.bool;
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description = ''
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If set, root doesn't need to authenticate (e.g. for the
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<command>useradd</command> service).
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'';
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};
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u2fAuth = mkOption {
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default = config.security.pam.enableU2F;
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type = types.bool;
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description = ''
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If set, users listed in
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<filename>~/.yubico/u2f_keys</filename> are able to log in
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with the associated U2F key.
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'';
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};
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usbAuth = mkOption {
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default = config.security.pam.usb.enable;
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type = types.bool;
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description = ''
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If set, users listed in
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<filename>/etc/pamusb.conf</filename> are able to log in
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with the associated USB key.
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'';
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};
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otpwAuth = mkOption {
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default = config.security.pam.enableOTPW;
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type = types.bool;
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description = ''
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If set, the OTPW system will be used (if
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<filename>~/.otpw</filename> exists).
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'';
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};
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fprintAuth = mkOption {
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default = config.services.fprintd.enable;
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type = types.bool;
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description = ''
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If set, fingerprint reader will be used (if exists and
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your fingerprints are enrolled).
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'';
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};
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oathAuth = mkOption {
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default = config.security.pam.enableOATH;
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type = types.bool;
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description = ''
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If set, the OATH Toolkit will be used.
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'';
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};
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sshAgentAuth = mkOption {
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default = false;
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type = types.bool;
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description = ''
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If set, the calling user's SSH agent is used to authenticate
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against the keys in the calling user's
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<filename>~/.ssh/authorized_keys</filename>. This is useful
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for <command>sudo</command> on password-less remote systems.
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'';
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};
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startSession = mkOption {
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default = false;
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type = types.bool;
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description = ''
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If set, the service will register a new session with
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systemd's login manager. For local sessions, this will give
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the user access to audio devices, CD-ROM drives. In the
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default PolicyKit configuration, it also allows the user to
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reboot the system.
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'';
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};
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setLoginUid = mkOption {
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type = types.bool;
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description = ''
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Set the login uid of the process
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(<filename>/proc/self/loginuid</filename>) for auditing
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purposes. The login uid is only set by ‘entry points’ like
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<command>login</command> and <command>sshd</command>, not by
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commands like <command>sudo</command>.
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'';
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};
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forwardXAuth = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Whether X authentication keys should be passed from the
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calling user to the target user (e.g. for
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<command>su</command>)
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'';
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};
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pamMount = mkOption {
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default = config.security.pam.mount.enable;
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type = types.bool;
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description = ''
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Enable PAM mount (pam_mount) system to mount fileystems on user login.
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'';
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};
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allowNullPassword = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Whether to allow logging into accounts that have no password
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set (i.e., have an empty password field in
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<filename>/etc/passwd</filename> or
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<filename>/etc/group</filename>). This does not enable
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logging into disabled accounts (i.e., that have the password
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field set to <literal>!</literal>). Note that regardless of
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what the pam_unix documentation says, accounts with hashed
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empty passwords are always allowed to log in.
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'';
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};
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requireWheel = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Whether to permit root access only to members of group wheel.
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'';
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};
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limits = mkOption {
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description = ''
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Attribute set describing resource limits. Defaults to the
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value of <option>security.pam.loginLimits</option>.
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'';
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};
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showMotd = mkOption {
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default = false;
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type = types.bool;
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description = "Whether to show the message of the day.";
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};
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makeHomeDir = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Whether to try to create home directories for users
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with <literal>$HOME</literal>s pointing to nonexistent
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locations on session login.
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'';
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};
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updateWtmp = mkOption {
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default = false;
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type = types.bool;
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description = "Whether to update <filename>/var/log/wtmp</filename>.";
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};
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logFailures = mkOption {
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default = false;
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type = types.bool;
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description = "Whether to log authentication failures in <filename>/var/log/faillog</filename>.";
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};
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enableAppArmor = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Enable support for attaching AppArmor profiles at the
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user/group level, e.g., as part of a role based access
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control scheme.
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'';
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};
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text = mkOption {
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type = types.nullOr types.lines;
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description = "Contents of the PAM service file.";
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};
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};
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config = {
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name = mkDefault name;
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setLoginUid = mkDefault cfg.startSession;
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limits = mkDefault config.security.pam.loginLimits;
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# !!! TODO: move the LDAP stuff to the LDAP module, and the
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# Samba stuff to the Samba module. This requires that the PAM
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# module provides the right hooks.
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text = mkDefault
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(''
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# Account management.
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account sufficient pam_unix.so
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${optionalString config.users.ldap.enable
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"account sufficient ${pam_ldap}/lib/security/pam_ldap.so"}
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${optionalString config.krb5.enable
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"account sufficient ${pam_krb5}/lib/security/pam_krb5.so"}
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# Authentication management.
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${optionalString cfg.rootOK
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"auth sufficient pam_rootok.so"}
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${optionalString cfg.requireWheel
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"auth required pam_wheel.so use_uid"}
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${optionalString cfg.logFailures
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"auth required pam_tally.so"}
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${optionalString (config.security.pam.enableSSHAgentAuth && cfg.sshAgentAuth)
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"auth sufficient ${pkgs.pam_ssh_agent_auth}/libexec/pam_ssh_agent_auth.so file=~/.ssh/authorized_keys:~/.ssh/authorized_keys2:/etc/ssh/authorized_keys.d/%u"}
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${optionalString cfg.fprintAuth
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"auth sufficient ${pkgs.fprintd}/lib/security/pam_fprintd.so"}
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${optionalString cfg.u2fAuth
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"auth sufficient ${pkgs.pam_u2f}/lib/security/pam_u2f.so"}
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${optionalString cfg.usbAuth
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"auth sufficient ${pkgs.pam_usb}/lib/security/pam_usb.so"}
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'' +
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# Modules in this block require having the password set in PAM_AUTHTOK.
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# pam_unix is marked as 'sufficient' on NixOS which means nothing will run
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# after it succeeds. Certain modules need to run after pam_unix
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# prompts the user for password so we run it once with 'required' at an
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# earlier point and it will run again with 'sufficient' further down.
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# We use try_first_pass the second time to avoid prompting password twice
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(optionalString (cfg.unixAuth && (config.security.pam.enableEcryptfs || cfg.pamMount)) ''
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auth required pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} likeauth
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${optionalString config.security.pam.enableEcryptfs
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"auth optional ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so unwrap"}
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${optionalString cfg.pamMount
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"auth optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
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'') + ''
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${optionalString cfg.unixAuth
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"auth sufficient pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} likeauth try_first_pass"}
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${optionalString cfg.otpwAuth
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"auth sufficient ${pkgs.otpw}/lib/security/pam_otpw.so"}
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${optionalString cfg.oathAuth
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"auth sufficient ${pkgs.oathToolkit}/lib/security/pam_oath.so window=5 usersfile=/etc/users.oath"}
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${optionalString config.users.ldap.enable
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"auth sufficient ${pam_ldap}/lib/security/pam_ldap.so use_first_pass"}
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${optionalString config.krb5.enable ''
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auth [default=ignore success=1 service_err=reset] ${pam_krb5}/lib/security/pam_krb5.so use_first_pass
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auth [default=die success=done] ${pam_ccreds}/lib/security/pam_ccreds.so action=validate use_first_pass
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auth sufficient ${pam_ccreds}/lib/security/pam_ccreds.so action=store use_first_pass
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''}
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auth required pam_deny.so
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# Password management.
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password requisite pam_unix.so nullok sha512
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${optionalString config.security.pam.enableEcryptfs
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"password optional ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so"}
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${optionalString cfg.pamMount
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"password optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
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${optionalString config.users.ldap.enable
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"password sufficient ${pam_ldap}/lib/security/pam_ldap.so"}
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${optionalString config.krb5.enable
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"password sufficient ${pam_krb5}/lib/security/pam_krb5.so use_first_pass"}
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${optionalString config.services.samba.syncPasswordsByPam
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"password optional ${pkgs.samba}/lib/security/pam_smbpass.so nullok use_authtok try_first_pass"}
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# Session management.
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session required pam_env.so envfile=${config.system.build.pamEnvironment}
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session required pam_unix.so
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${optionalString cfg.setLoginUid
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"session ${
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if config.boot.isContainer then "optional" else "required"
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} pam_loginuid.so"}
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${optionalString cfg.makeHomeDir
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"session required ${pkgs.pam}/lib/security/pam_mkhomedir.so silent skel=/etc/skel umask=0022"}
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${optionalString cfg.updateWtmp
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"session required ${pkgs.pam}/lib/security/pam_lastlog.so silent"}
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${optionalString config.security.pam.enableEcryptfs
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"session optional ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so"}
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${optionalString config.users.ldap.enable
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"session optional ${pam_ldap}/lib/security/pam_ldap.so"}
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${optionalString config.krb5.enable
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"session optional ${pam_krb5}/lib/security/pam_krb5.so"}
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${optionalString cfg.otpwAuth
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"session optional ${pkgs.otpw}/lib/security/pam_otpw.so"}
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${optionalString cfg.oathAuth
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"session optional ${pkgs.oathToolkit}/lib/security/pam_oath.so window=5 usersfile=/etc/users.oath"}
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${optionalString cfg.startSession
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"session optional ${pkgs.systemd}/lib/security/pam_systemd.so"}
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${optionalString cfg.forwardXAuth
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"session optional pam_xauth.so xauthpath=${pkgs.xorg.xauth}/bin/xauth systemuser=99"}
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${optionalString (cfg.limits != [])
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"session required ${pkgs.pam}/lib/security/pam_limits.so conf=${makeLimitsConf cfg.limits}"}
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${optionalString (cfg.showMotd && config.users.motd != null)
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"session optional ${pkgs.pam}/lib/security/pam_motd.so motd=${motd}"}
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${optionalString cfg.pamMount
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"session optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
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${optionalString (cfg.enableAppArmor && config.security.apparmor.enable)
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"session optional ${pkgs.apparmor-pam}/lib/security/pam_apparmor.so order=user,group,default debug"}
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'');
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};
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};
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inherit (pkgs) pam_krb5 pam_ccreds;
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pam_ldap = if config.users.ldap.daemon.enable then pkgs.nss_pam_ldapd else pkgs.pam_ldap;
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# Create a limits.conf(5) file.
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makeLimitsConf = limits:
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pkgs.writeText "limits.conf"
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(concatMapStrings ({ domain, type, item, value }:
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"${domain} ${type} ${item} ${toString value}\n")
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limits);
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motd = pkgs.writeText "motd" config.users.motd;
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makePAMService = pamService:
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{ source = pkgs.writeText "${pamService.name}.pam" pamService.text;
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target = "pam.d/${pamService.name}";
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};
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in
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{
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###### interface
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options = {
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security.pam.loginLimits = mkOption {
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default = [];
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example =
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[ { domain = "ftp";
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type = "hard";
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item = "nproc";
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value = "0";
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}
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{ domain = "@student";
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type = "-";
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item = "maxlogins";
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value = "4";
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}
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];
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description =
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'' Define resource limits that should apply to users or groups.
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Each item in the list should be an attribute set with a
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<varname>domain</varname>, <varname>type</varname>,
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<varname>item</varname>, and <varname>value</varname>
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attribute. The syntax and semantics of these attributes
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must be that described in the limits.conf(5) man page.
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'';
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};
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security.pam.services = mkOption {
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default = [];
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type = types.loaOf types.optionSet;
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options = [ pamOpts ];
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description =
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''
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This option defines the PAM services. A service typically
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corresponds to a program that uses PAM,
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e.g. <command>login</command> or <command>passwd</command>.
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Each attribute of this set defines a PAM service, with the attribute name
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defining the name of the service.
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'';
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};
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security.pam.enableSSHAgentAuth = mkOption {
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default = false;
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description =
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''
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Enable sudo logins if the user's SSH agent provides a key
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present in <filename>~/.ssh/authorized_keys</filename>.
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This allows machines to exclusively use SSH keys instead of
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passwords.
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'';
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};
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security.pam.enableOTPW = mkOption {
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default = false;
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description = ''
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Enable the OTPW (one-time password) PAM module.
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'';
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};
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security.pam.enableOATH = mkOption {
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default = false;
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description = ''
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Enable the OATH (one-time password) PAM module.
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'';
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};
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security.pam.enableU2F = mkOption {
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default = false;
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description = ''
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Enable the U2F PAM module.
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'';
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};
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security.pam.enableEcryptfs = mkOption {
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default = false;
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description = ''
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Enable eCryptfs PAM module (mounting ecryptfs home directory on login).
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'';
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};
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users.motd = mkOption {
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default = null;
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example = "Today is Sweetmorn, the 4th day of The Aftermath in the YOLD 3178.";
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type = types.nullOr types.lines;
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description = "Message of the day shown to users when they log in.";
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};
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};
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###### implementation
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config = {
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environment.systemPackages =
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# Include the PAM modules in the system path mostly for the manpages.
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[ pkgs.pam ]
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++ optional config.users.ldap.enable pam_ldap
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++ optionals config.krb5.enable [pam_krb5 pam_ccreds]
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++ optionals config.security.pam.enableOTPW [ pkgs.otpw ]
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++ optionals config.security.pam.enableOATH [ pkgs.oathToolkit ]
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++ optionals config.security.pam.enableU2F [ pkgs.pam_u2f ]
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++ optionals config.security.pam.enableEcryptfs [ pkgs.ecryptfs ];
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security.setuidPrograms =
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optionals config.security.pam.enableEcryptfs [ "mount.ecryptfs_private" "umount.ecryptfs_private" ];
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environment.etc =
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mapAttrsToList (n: v: makePAMService v) config.security.pam.services;
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security.setuidOwners = [ {
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program = "unix_chkpwd";
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source = "${pkgs.pam}/sbin/unix_chkpwd.orig";
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owner = "root";
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setuid = true;
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} ];
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security.pam.services =
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{ other.text =
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''
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auth required pam_warn.so
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auth required pam_deny.so
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account required pam_warn.so
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account required pam_deny.so
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password required pam_warn.so
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password required pam_deny.so
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session required pam_warn.so
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session required pam_deny.so
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'';
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# Most of these should be moved to specific modules.
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cups = {};
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ftp = {};
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i3lock = {};
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screen = {};
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vlock = {};
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xlock = {};
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xscreensaver = {};
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};
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};
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}
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