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diff --git a/man/pam_systemd_home.xml b/man/pam_systemd_home.xml new file mode 100644 index 0000000..ff4735c --- /dev/null +++ b/man/pam_systemd_home.xml @@ -0,0 +1,175 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<refentry id="pam_systemd_home" conditional='ENABLE_PAM_HOME'> + + <refentryinfo> + <title>pam_systemd_home</title> + <productname>systemd</productname> + </refentryinfo> + + <refmeta> + <refentrytitle>pam_systemd_home</refentrytitle> + <manvolnum>8</manvolnum> + </refmeta> + + <refnamediv> + <refname>pam_systemd_home</refname> + <refpurpose>Authenticate users and mount home directories via <filename>systemd-homed.service</filename> + </refpurpose> + </refnamediv> + + <refsynopsisdiv> + <para><filename>pam_systemd_home.so</filename></para> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><command>pam_systemd_home</command> ensures that home directories managed by + <citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> + are automatically activated (mounted) on user login, and are deactivated (unmounted) when the last + session of the user ends. For such users, it also provides authentication (when per-user disk encryption + is used, the disk encryption key is derived from the authentication credential supplied at login time), + account management (the <ulink url="https://systemd.io/USER_RECORD/">JSON user record</ulink> embedded in + the home store contains account details), and implements the updating of the encryption password (which + is also used for user authentication).</para> + </refsect1> + + <refsect1> + <title>Options</title> + + <para>The following options are understood:</para> + + <variablelist class='pam-directives'> + + <varlistentry> + <term><varname>suspend=</varname></term> + + <listitem><para>Takes a boolean argument. If true, the home directory of the user will be suspended + automatically during system suspend; if false it will remain active. Automatic suspending of the home + directory improves security substantially as secret key material is automatically removed from memory + before the system is put to sleep and must be re-acquired (through user re-authentication) when + coming back from suspend. It is recommended to set this parameter for all PAM applications that have + support for automatically re-authenticating via PAM on system resume. If multiple sessions of the + same user are open in parallel the user's home directory will be left unsuspended on system suspend + as long as at least one of the sessions does not set this parameter to on. Defaults to + off.</para> + + <para>Note that TTY logins generally do not support re-authentication on system resume. + Re-authentication on system resume is primarily a concept implementable in graphical environments, in + the form of lock screens brought up automatically when the system goes to sleep. This means that if a + user concurrently uses graphical login sessions that implement the required re-authentication + mechanism and console logins that do not, the home directory is not locked during suspend, due to the + logic explained above. That said, it is possible to set this field for TTY logins too, ignoring the + fact that TTY logins actually don't support the re-authentication mechanism. In that case the TTY + sessions will appear hung until the user logs in on another virtual terminal (regardless if via + another TTY session or graphically) which will resume the home directory and unblock the original TTY + session. (Do note that lack of screen locking on TTY sessions means even though the TTY session + appears hung, keypresses can still be queued into it, and the existing screen contents be read + without re-authentication; this limitation is unrelated to the home directory management + <command>pam_systemd_home</command> and <filename>systemd-homed.service</filename> implement.)</para> + + <para>Turning this option on by default is highly recommended for all sessions, but only if the + service managing these sessions correctly implements the aforementioned re-authentication. Note that + the re-authentication must take place from a component running outside of the user's context, so that + it does not require access to the user's home directory for operation. Traditionally, most desktop + environments do not implement screen locking this way, and need to be updated + accordingly.</para> + + <para>This setting may also be controlled via the <varname>$SYSTEMD_HOME_SUSPEND</varname> + environment variable (see below), which <command>pam_systemd_home</command> reads during initialization and sets + for sessions. If both the environment variable is set and the module parameter specified the latter + takes precedence.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>debug</varname><optional>=</optional></term> + + <listitem><para>Takes an optional boolean argument. If yes or without the argument, the module will log + debugging information as it operates.</para></listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Module Types Provided</title> + + <para>The module implements all four PAM operations: <option>auth</option> (reason: to allow + authentication using the encrypted data), <option>account</option> (reason: users with + <filename>systemd-homed.service</filename> user accounts are described in a <ulink + url="https://systemd.io/USER_RECORD/">JSON user record</ulink> and may be configured in more detail than + in the traditional Linux user database), <option>session</option> (user sessions must be tracked in order + to implement automatic release when the last session of the user is gone), <option>password</option> (to + change the encryption password — also used for user authentication — through PAM).</para> + </refsect1> + + <refsect1> + <title>Environment</title> + + <para>The following environment variables are initialized by the module and available to the processes of the + user's session:</para> + + <variablelist class='environment-variables'> + <varlistentry> + <term><varname>$SYSTEMD_HOME=1</varname></term> + + <listitem><para>Indicates that the user's home directory is managed by <filename>systemd-homed.service</filename>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>$SYSTEMD_HOME_SUSPEND=</varname></term> + + <listitem><para>Indicates whether the session has been registered with the suspend mechanism enabled + or disabled (see above). The variable's value is either <literal>0</literal> or + <literal>1</literal>. Note that the module both reads the variable when initializing, and sets it for + sessions.</para></listitem> + </varlistentry> + + </variablelist> + </refsect1> + + <refsect1> + <title>Example</title> + + <para>Here's an example PAM configuration fragment that permits users managed by + <filename>systemd-homed.service</filename> to log in:</para> + + <programlisting>#%PAM-1.0 +auth sufficient pam_unix.so +<command>-auth sufficient pam_systemd_home.so</command> +auth required pam_deny.so + +account required pam_nologin.so +<command>-account sufficient pam_systemd_home.so</command> +account sufficient pam_unix.so +account required pam_permit.so + +<command>-password sufficient pam_systemd_home.so</command> +password sufficient pam_unix.so sha512 shadow try_first_pass +password required pam_deny.so + +-session optional pam_keyinit.so revoke +-session optional pam_loginuid.so +<command>-session optional pam_systemd_home.so</command> +-session optional pam_systemd.so +session required pam_unix.so</programlisting> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>homed.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>homectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>pam_systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |